The Vasculome: From Many, One

The Vasculome: From Many, One introduces the fundamental bases of the “unity in diversity of the Vasculome, from the coming together of various cell lineages during development, to its deceptively simple solution for architectural design: the efficient interplay of a few types of building blocks supporting key similar functions throughout the body and their highly specialized functional local variations. Specific examples are included to illustrate how the Vasculome is integral to the function and malfunction of different organs, such as the brain or the kidney.

Each section is preceded by an introductory summary that will give a high level unified view of the key concepts illustrated in the various chapters in that section.

Zorina Galis' The Vasculome was named a finalist in the Clinical Medicine category of the American Association of Publishers’ 2023 PROSE Awards.

• 2023 PROSE Awards - Winner: Finalist: Clinical Medicine: Association of American Publishers
• Brings together leading experts who present the latest biomedical thinking about the vasculature from the integrative perspective of the Vasculome
• Challenges traditional real and perceived boundaries within vascular research areas and stimulates new fundamental thinking and medical explorations
• Creates the bases for translating the integrative Vasculome concept into improved fundamental and clinical assessment and management of local and systemic contributions of the vasculature in health and disease

• Language: English
• Publisher: Academic Press
• Release date: Jun 11, 2022
• ISBN: 9780128225479

Book preview

The Vasculome

From Many, One

Edited by

Zorina S. Galis

Vascular Researcher, Bethesda, MD, United States

Table of Contents

Cover image

Title page

Companion website

Copyright

Contributors

Preamble

Acknowledgment

List of abbreviations

The architectural design of the vasculome: basis for system-wide functional unity and local diversity

Section 1. The endothelium: key unifying principle of the vasculome. Basis for systemic unity and for engineering of local specialization

Chapter 1. Development of, and environmental impact on, endothelial cell diversity

Introduction

Diversity of endothelial cell types

Endothelial cell diversity within adult organs

Impact of environmental factors on endothelial cell specification

Epigenetic and noncoding RNA regulation of endothelial cell phenotype

Summary and conclusions

Chapter 2. Endothelial cell heterogeneity and plasticity in health and disease—new insights from single-cell studies

Introduction

Endothelial cell heterogeneity and plasticity

Angiogenic EC phenotypes

EC metabolic heterogeneity

EC heterogeneity in tissue repair

EC heterogeneity in cancer

Perspectives and therapeutic implications

Section 2. Vasculome’s key building blocks—beyond the endothelium

Chapter 3. The remarkable diversity of vascular smooth muscle in development and disease: a paradigm for mesenchymal cell types

Introduction

The vascular system is a developmental mosaic

Assembly of the vessel wall in development

Self-organization guides artery wall development

Positional identity and VSMC diversity

VSMC differentiation, phenotypic switching, and reprogramming

VSMC reprogramming to multiple mesenchymal cell types

Role of Krüppel-like factor 4 in VSMC reprogramming

VSMC single-cell transcriptomes and VSMC reprogramming

VSMC single-cell transcriptomes and embryonic origins

Vascular smooth muscle clonal expansions in vivo

SMC diversity: one genome, many epigenomes

VSMCs—a paradigm for mesenchymal cell types

Does VSMC reprogramming extend the vasculome beyond the vascular system?

Chapter 4. Smooth muscle diversity in the vascular system

Introduction

Vascular smooth muscle cell diversity: contractile properties

Vascular smooth muscle cell diversity in vasomotor control and signaling networks

Alternative splicing to rewire signaling networks

Newer methodologies for the study of smooth muscle diversity

Conclusion

Chapter 5. Resident vascular immune cells in health and atherosclerotic disease

Macrophages

Granulocytes

Dendritic cells

CD4+ and CD8+ T cells

Other T cell subsets

B cells

Other lymphoid cells

Conclusion

Chapter 6. Perivascular adipose tissue: friend or foe?

Introduction

PVAT vascular functions

Perivascular adipose tissue implications in pathology

Conclusion

Chapter 7. Major vascular ECM components, differential distribution supporting structure, and functions of the vasculome

Structure and function of the vasculome

Major vascular ECM proteins

The ECM and its interactions with cells

Conclusions

Section 3. Putting it all together: vasculome integration across body scales and within tissues

Chapter 8. Out to the tissues: the arterial side (arteries, arterioles—development, structure, functions, and pathologies)

Introduction

The arterial wall: development, structure, and function

Arterial pathologies

Conclusion

Chapter 9. Capillary diversity: endothelial cell specializations to meet tissue metabolic needs

Introduction

Attributes of capillary endothelial cells

Maintenance and expansion of capillary networks

Endothelial control of nutrient delivery

Release of angiocrine factors to support tissue physiology

Endothelial cell role in immune surveillance

Indicators of tissue-specific endothelial cell plasticity?

Consequences of compromised endothelial cell performance

Conclusions

Chapter 10. The neurovascular unit and blood–CNS barriers in health and disease

The neurovascular unit and the blood–CNS barrier in the healthy state

CNS angiogenesis and BBB/BRB development

Vascular basement membrane and CNS vascular barrier maturation

The neurovascular unit and blood–CNS barriers in neurological and ocular diseases

Chapter 11. Lymphatic biology and medicine

Introduction

Lymphatic vasculature

Lymphangiogenesis

Lymphedema

Pathological conditions with lymphatic defects

Concluding remarks

Investigating the vasculome: context-driven methods, uses, and limitations

Section 1. Experimental and computational studies of the vasculome

Chapter 12. The flow-dependent endotheliome: hemodynamic forces, genetic programs, and functional phenotypes

Introduction

Flow patterns in the human circulation

Modeling human hemodynamic forces in vitro

Unraveling flow-dependent endothelial gene expression and functional phenotypes

Conclusions and future directions

Chapter 13. Intravital photoacoustic microscopy of microvascular function and oxygen metabolism

Introduction

Multiparametric PAM: the working principles

Intravital PAM of the skin microvasculature

Intravital PAM of the dorsal vasculature

Intravital PAM of the cerebral microvasculature

Intravital PAM of the microvasculature in other tissues and organs

Frontiers in intravital PAM of the microvasculature

Conclusion

Chapter 14. Systems biology modeling of endothelial cell and macrophage signaling in angiogenesis in human diseases

Introduction

Computational models of HIF stabilization and HIF-mediated cellular pathways in angiogenesis

Computational models of growth factor-mediated signaling pathways regulating angiogenesis

Computational multipathway models of endothelial cells and macrophages in angiogenesis

Discussion and future perspectives

Chapter 15. Simulation of blood flow and oxygen transport in vascular networks

Introduction

Simulation of blood flow

Simulation of oxygen transport

Discussion

Chapter 16. Clinical investigations of vascular function

Vascular endothelial function

Arterial stiffness

Conclusions

Appendix A. Supplementary data

Section 2. Realizing the promise of new high-content technologies

Chapter 17. Angiodiversity—A tale retold by comparative transcriptomics

Introduction

Chapter 18. Using pattern recognition and discriminant analysis of functional perfusion data to create angioprints for normal and perturbed angiogenic microvascular networks

Introduction

Overall experimental design

Results

Discussion

Methods

Experimental data

Automated pattern recognition and discrete optimization-based classification model for discriminant analysis

Image-based pattern recognition algorithm

Chapter 19. Artificial intelligence for the vasculome

Introduction

Conclusion

Vasculome dynamics: in health and in sickness

Section 1. Cooperating during development and organogenesis to create vasculome diversity

Chapter 20. Vascular development and organogenesis: depots of diversity among conduits of connectivity define the vasculome

Introduction

Historical perspective of the vasculome concept

Vascular development and organogenesis: where it all starts

Vascular development and organogenesis: location-dependent crosstalk

Circulation-dependent input for local vascular specialization

The vasculome: conclusions and future directions

Chapter 21. Normal vascular identity (arteries, veins, and lymphatics) and malformations

Introduction

Vasculogenesis: arteriovenous differentiation

Angiogenesis: sprouting angiogenesis

Establishing vascular identity

Vascular malformations

Vascular tumors

Switching of arterial–venous identity

Summary

Chapter 22. Sprouting angiogenesis in vascular and lymphatic development

Vascular development

Sprouting angiogenesis

Vascular endothelial growth factor and regulation of tip cell formation

Guidance receptor signaling

The Notch directive: tip or stalk?

Refinement of sprouting angiogenesis by BMP signals

Lymphatic development

Section 2. Physiological and pathological remodeling of the vasculome

Chapter 23. Enablers and drivers of vascular remodeling

Introduction

Brief on vascular mechanics

Biological and physiological consequences of mechanics

Mechanobiology and SMC phenotype

ECM turnover in evolving mechanical states

Mechanical homeostasis—an organizing principle

Conclusion

Appendix 1

Chapter 24. Extracellular matrix dynamics and contribution to vascular pathologies

Atherosclerosis

Vascular calcification

Arterial stiffening

Aneurysms

Limitations and areas needing further study

Chapter 25. Lymphatic vascular anomalies and dysfunction

Introduction

Lymphatic vascular tumors

Lymphatic malformations

Lymphatic malformations associated with other vascular malformations or overgrowth syndromes

Primary lymphedema

Conclusions

Part IV. The vasculome as perpetrator and victim in local and systemic diseases

Chapter 26. Endothelial dysfunction: basis for many local and systemic conditions

Introduction

Physiological role of endothelial (vascular) function

Mechanisms of endothelial dysfunction

Therapeutic prevention of endothelial (vascular) dysfunction

Conclusions and clinical implications

Chapter 27. The vascular phenotype in hypertension

Introduction

Vascular function: integration of vascular smooth muscle contraction/relaxation

Vascular remodeling in hypertension

The immune system and inflammation—a new paradigm in the vascular phenotype in hypertension

Perivascular adipose tissue influences vascular function in hypertension

Vascular aging in hypertension

Conclusions

Chapter 28. Functional roles of lymphatics in health and disease

Introduction

Lymphatics in adipose metabolism and obesity

Lymphatics in skin regeneration

Lymphatics in the central nervous system

Alzheimer's disease

Aging

Lymphatic function in aqueous drainage and glaucoma

Lymphatics in cardiovascular disease

Atherosclerosis

Myocardial infarction

Conclusions

Chapter 29. Extracellular matrix genetics of thoracic and abdominal aortic diseases

Thoracic aortic aneurysms predispose to acute aortic dissections

Heritable thoracic aortic disease genetics highlights the importance of maintaining an aortic structural component, the elastin-contractile unit

The genetics of abdominal aortic aneurysms

The extracellular matrix in genetics of aortic disease

Chapter 30. Peripheral arterial disease (pathophysiology, presentation, prevention/management)

Introduction

PAD: epidemiology and risk factors

Diagnosis and initial evaluation

Spectrum of disease

Pathophysiology and pathobiology

Disease management

PAD therapies in development

Conclusions

Chapter 31. Venous diseases including thromboembolic phenomena

Venous thrombogenesis with special emphasis on selectins

Venous thrombosis and resolution

Pre-clinical/basic science models

Preclinical/translational models

Research reproducibility/comparative pathology/statistical consultation

New areas of venous research in thrombogenesis, resolution, and novel approaches for the future

Part V. The vasculome in diagnosis, prevention, and treatment of other diseases

Chapter 32. Targeting vascular zip codes: from combinatorial selection to drug prototypes

Introduction

A brief history of phage display

In vivo phage display and vascular zip codes

Human vascular mapping project

Translational/clinical applications

Bone Metastasis Targeting Peptidomimetic-11 (BMTP-11)

Adipotide

Other zip codes

Conclusions

Chapter 33. Angiosome concept for vascular interventions

Introduction

Clinical implementation of the angiosome model in the current treatment of CLTI

Summary

Chapter 34. RNA therapies for cardiovascular disease

Introduction to RNA therapeutics

RNA therapeutics in lipid disorders

Emerging RNA therapeutics for cardiac transthyretin amyloidosis

Future perspectives

Chapter 35. The brain vasculome: an integrative model for CNS function and disease

Introduction

Vasculome modifying factors

Cell–Cell interactions

Levels of vasculome mapping

The functional vasculome

Conclusions and future directions

Part VI. Looking forward toward Precision Health for the vasculome

Chapter 36. Vasculome: defining and optimizing vascular health

Introduction

Conclusion

Chapter 37. The Vasculome provides a body-wide cellular positioning system and functional barometer. The Vasculature as Common Coordinate Frame (VCCF) concept

Key requirements for a common coordinate frame (CCF) for the human body

Evaluating the vasculature as CCF and road map for the human body

Practical considerations for using the vasculature as a human body CCF

Vasculature as a barometer of functional tissue status and health

Parting thoughts

Index

Companion website

Copyright

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Notices

Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.

Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.

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Contributors

Bipul R. Acharya

Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA, United States

Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, United States

Wellcome Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom

Dritan Agalliu

Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States

Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, United States

V.A. Alexandrescu,     Cardiovascular and Thoracic Surgery Department, CHU Sart-Tilman University Hospital, Liège, Belgium

Zakaria Almuwaqqat,     Emory Clinical Cardiovascular Research Institute, Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia

Rheure Alves-Lopes,     Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, United Kingdom

Ken Arai,     Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Wadih Arap

Rutgers Cancer Institute of New Jersey, Newark, NJ, United States

Division of Hematology/Oncology, Department of Medicine, Rutgers New Jersey Medical School, Newark, NJ, United States

Victoria L. Bautch

Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

Curriculum in Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

Lisa M. Becker,     Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, VIB Center for Cancer Biology, VIB, Leuven, Belgium

Michelle P. Bendeck

Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada

Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, Canada

Jan Walter Benjamins,     Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands

Saptarshi Biswas,     Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States

E. Boesmans,     Cardiovascular and Thoracic Surgery Department, CHU Sart-Tilman University Hospital, Liège, Belgium

Livia L. Camargo,     Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, United Kingdom

Peter Carmeliet

Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, VIB Center for Cancer Biology, VIB, Leuven, Belgium

Laboratory of Angiogenesis and Vascular Heterogeneity, Department of Biomedicine, Aarhus University, Aarhus, Denmark

State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, P.R. China

Munir Chaudhuri,     Department of Internal Medicine, Emory University School of Medicine, Atlanta, GA, United States

Nicholas W. Chavkin

Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA, United States

Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, United States

Ondine Cleaver,     Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States

Clément Cochain

Institute of Experimental Biomedicine, University Hospital Würzburg, Würzburg, Germany

Comprehensive Heart Failure Center, University Hospital Würzburg, Würzburg, Germany

Michael S. Conte,     Department of Surgery, Division of Vascular and Endovascular Surgery, University of California San Francisco, San Francisco, CA, United States

Azzurra Cottarelli

Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States

Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, United States

Christie L. Crandall,     Department of Mechanical Engineering and Materials Science, Washington University, St. Louis, MO, United States

Anne Cuypers,     Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, VIB Center for Cancer Biology, VIB, Leuven, Belgium

Andreas Daiber

Department of Cardiology, Medical Center of the Johannes Gutenberg University, Mainz, Germany

German Center for Cardiovascular Research (DZHK), Mainz, Germany

Alan Dardik

Department of Cellular and Molecular Biology, Yale School of Medicine, New Haven, CT, United States

Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, United States

Department of Surgery, Yale School of Medicine, New Haven, CT, United States

VA Connecticut Healthcare System, West Haven, CT, United States

Jui M. Dave

Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Medicine, Yale University, New Haven, CT, United States

Department of Genetics, Yale University, New Haven, CT, United States

J.O. Defraigne,     Cardiovascular and Thoracic Surgery Department, CHU Sart-Tilman University Hospital, Liège, Belgium

Wenjun Deng

Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Department of Neurology, Clinical Proteomics Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Robert J. DeStefano,     Department of Internal Medicine, Emory University School of Medicine, Atlanta, GA, United States

Devinder Dhindsa,     Emory Clinical Cardiovascular Research Institute, Division of Cardiology, Emory University School of Medicine, Atlanta, GA, United States

Danny J. Eapen,     Department of Medicine, Division of Cardiology, Emory University, Atlanta, GA, United States

Anne Eichmann

Cardiovascular Research Center, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, United States

Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, United States

Inserm U970, Paris Cardiovascular Research Center, Paris, France

Christian El Amm,     Department of Surgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States

Omotayo Eluwole

Department of Physiology, University of Witwatersrand, Johannesburg, Gauteng, South Africa

Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria

Christian Faaborg-Andersen,     Emory University School of Medicine, Atlanta, GA, United States

Steven A. Fisher,     Departments of Medicine (Cardiovascular Division) and Physiology, University of Maryland School of Medicine and Baltimore Veterans Administration Medical Center, Baltimore, MD, United States

Zorina S. Galis,     Vascular Researcher, Bethesda, MD, United States

Guillermo García-Cardeña,     Department of Pathology, Center for Excellence in Vascular Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States

Xin Geng,     Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States

Michael A. Gimbrone Jr. ,     Department of Pathology, Center for Excellence in Vascular Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States

Luis Gonzalez

Department of Cellular and Molecular Biology, Yale School of Medicine, New Haven, CT, United States

Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, United States

Daniel M. Greif

Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Medicine, Yale University, New Haven, CT, United States

Department of Genetics, Yale University, New Haven, CT, United States

Xiaowu Gu,     Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States

Shuzhen Guo,     Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Tara L. Haas,     Faculty of Health, York University, Toronto, ON, Canada

Omar Hahad

Department of Cardiology, Medical Center of the Johannes Gutenberg University, Mainz, Germany

German Center for Cardiovascular Research (DZHK), Mainz, Germany

Pim van der Harst

Department of Cardiology, Heart and Lung Division, University Medical Centre Utrecht, Utrecht, the Netherlands

Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands

Peter K. Henke,     Section of Vascular Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI, United States

Karen K. Hirschi

Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA, United States

Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, United States

Departments of Medicine and Genetics, Yale University School of Medicine, Yale Cardiovascular Research Center, New Haven, CT, United States

C. Holemans,     Cardiovascular and Thoracic Surgery Department, CHU Sart-Tilman University Hospital, Liège, Belgium

Gonçalo Hora de Carvalho,     Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands

Song Hu,     Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States

Jay D. Humphrey,     Department of Biomedical Engineering and Vascular Biology and Therapeutics Program, Yale University, New Haven, CT, United States

Shabatun J. Islam,     Emory Clinical Cardiovascular Research Institute, Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia

Xinguo Jiang

VA Palo Alto Health Care System, Palo Alto, CA, United States

Stanford University School of Medicine, Stanford, CA, United States

Luis Eduardo Juarez-Orozco

Department of Cardiology, Heart and Lung Division, University Medical Centre Utrecht, Utrecht, the Netherlands

Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands

Angelos D. Karagiannis,     Department of Internal Medicine, Emory University School of Medicine, Atlanta, GA, United States

Anita Kaw,     Division of Medical Genetics, Department of Internal Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, United States

Kaveeta Kaw,     Division of Medical Genetics, Department of Internal Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, United States

Fatemeh Kazemzadeh,     Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands

A. Kerzmann,     Cardiovascular and Thoracic Surgery Department, CHU Sart-Tilman University Hospital, Liège, Belgium

Alexander S. Kim,     Department of Surgery, Division of Vascular and Endovascular Surgery, University of California San Francisco, San Francisco, CA, United States

Ageliki Laina

Department of Clinical Therapeutics, National and Kapodistrian University of Athens, School of Medicine, Athens, Greece

Biosciences Institute, Vascular Biology and Medicine Theme, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom

Eva K. Lee

Center for Operations Research in Medicine and Healthcare, Georgia Institute of Technology, Atlanta, GA, United States

Center for Bioinformatics and Computational Genomics, Georgia Institute of Technology, Atlanta, GA, United States

Jinyu Li

Cardiovascular Research Center, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, United States

Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, United States

Wenlu Li,     Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Chien-Jung Lin

Department of Cell Biology and Physiology, Washington University, St. Louis, MO, United States

Department of Internal Medicine (Cardiovascular Division), Washington University, St. Louis, MO, United States

Xiaolei Liu,     Center for Vascular and Developmental Biology, Feinberg Cardiovascular and Renal Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States

Eng H. Lo

Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Department of Neurology, Clinical Proteomics Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Josephine Lok

Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Pediatric Critical Care Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Mark W. Majesky

Center for Developmental Biology & Regenerative Medicine, Seattle Children's Research Institute, University of Washington, Seattle, WA, United States

Departments of Pediatrics, University of Washington, Seattle, WA, United States

Laboratory Medicine & Pathology, University of Washington, Seattle, WA, United States

Ziad Mallat

Department of Medicine, Division of Cardiovascular Medicine, University of Cambridge, Cambridge, United Kingdom

Université de Paris, PARCC, INSERM, Paris, France

Muzi J. Maseko,     Department of Physiology, University of Witwatersrand, Johannesburg, Gauteng, South Africa

Dianna M. Milewicz,     Division of Medical Genetics, Department of Internal Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, United States

Amanda L. Mohabeer

Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada

Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, Canada

Augusto C. Montezano,     Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, United Kingdom

Giorgio Mottola

Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Medicine, Yale University, New Haven, CT, United States

Department of Genetics, Yale University, New Haven, CT, United States

Thomas Münzel

Department of Cardiology, Medical Center of the Johannes Gutenberg University, Mainz, Germany

German Center for Cardiovascular Research (DZHK), Mainz, Germany

Daniel D. Myers,     Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, MI, United States

Karla B. Neves,     Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, United Kingdom

Mark R. Nicolls

VA Palo Alto Health Care System, Palo Alto, CA, United States

Stanford University School of Medicine, Stanford, CA, United States

MingMing Ning

Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Department of Neurology, Clinical Proteomics Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Andrea T. Obi,     Section of Vascular Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI, United States

Guillermo Oliver,     Center for Vascular and Developmental Biology, Feinberg Cardiovascular and Renal Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States

Renata Pasqualini

Rutgers Cancer Institute of New Jersey, Newark, NJ, United States

Division of Cancer Biology, Department of Radiation Oncology, Rutgers New Jersey Medical School, Newark, NJ, United States

Alessandra Pasut,     Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, VIB Center for Cancer Biology, VIB, Leuven, Belgium

Alexandra Pislaru,     Faculty of Science, York University, Toronto, ON, Canada

Aleksander S. Popel,     Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, United States

Raymundo A. Quintana,     Department of Medicine, Division of Cardiology, Emory University, Atlanta, GA, United States

Arshed A. Quyyumi,     Emory Clinical Cardiovascular Research Institute, Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia

Francisco J. Rios,     Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, United Kingdom

Stanley G. Rockson,     Stanford University School of Medicine, Stanford, CA, United States

Martina Rudnicki,     Faculty of Health, York University, Toronto, ON, Canada

Junichi Saito

Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Medicine, Yale University, New Haven, CT, United States

Department of Genetics, Yale University, New Haven, CT, United States

Charles D. Searles Jr. ,     Department of Medicine, Division of Cardiology, Emory University, Atlanta, GA, United States

Timothy W. Secomb,     Department of Physiology and BIO5 Institute, University of Arizona, Tucson, AZ, United States

Cristina M. Sena,     Institute of Physiology, iCBR, Faculty of Medicine, University of Coimbra, Coimbra, Portugal

Richard L. Sidman,     Department of Neurology, Harvard Medical School, Boston, MA, United States

Federico Silva-Palacios,     Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States

Tracey L. Smith

Rutgers Cancer Institute of New Jersey, Newark, NJ, United States

Division of Cancer Biology, Department of Radiation Oncology, Rutgers New Jersey Medical School, Newark, NJ, United States

Suman Sood,     Division of Hematology/Oncology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, United States

Laurence S. Sperling

Emory Clinical Cardiovascular Research Institute, Division of Cardiology, Emory University School of Medicine, Atlanta, GA, United States

Katz Professor in Preventive Cardiology, Professor of Global Health, Hubert Department of Global Health, Rollins School of Public Health at Emory University, Atlanta, GA, United States

R. Sathish Srinivasan

Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States

Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States

Kimon Stamatelopoulos

Department of Clinical Therapeutics, National and Kapodistrian University of Athens, School of Medicine, Athens, Greece

Biosciences Institute, Vascular Biology and Medicine Theme, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom

Konstantinos Stellos

Biosciences Institute, Vascular Biology and Medicine Theme, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom

Department of Cardiology, Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom

Naidi Sun,     Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States

Wen Tian

VA Palo Alto Health Care System, Palo Alto, CA, United States

Stanford University School of Medicine, Stanford, CA, United States

Rhian M. Touyz,     Institute of Cardiovascular and Medical Sciences, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, United Kingdom

Nikolaos Ι. Vlachogiannis

Biosciences Institute, Vascular Biology and Medicine Theme, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom

Department of Cardiology, Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom

Jessica E. Wagenseil,     Department of Mechanical Engineering and Materials Science, Washington University, St. Louis, MO, United States

Thomas W. Wakefield,     Section of Vascular Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI, United States

Charlotte R. Wayne,     Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States

Changhong Xing

Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX, United States

Ming Wai Yeung,     Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands

Yu Zhang,     Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, United States

Chen Zhao,     Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, United States

Preamble

The vasculome: from many, one concept Zorina S. Galis

When a patient experiences a medical condition affecting a discrete organ, such as an eye or kidney, the choice of medical experts to be consulted appears clear, yet, frequently the underlying problem may be a local manifestation of a systemic vascular condition, such as hypertension, and that important connection frequently may go undiagnosed. This is especially true for the dysfunction of the microvasculature, which, in spite of its microscopic scale, is essential for every organ's survival and proper function, and makes up the majority of our vasculature, yet may indeed be out of sight, out of mind! Such everyday medical occurrences illustrate the important ramifications of local and systemic vascular health, respectively, malfunction and the continuous deepening of biomedical expertise needed to deal with the complexity of different parts of the body-wide vascular system, as it substantially participates in the function and malfunction of all the different organs. Furthermore, medical conditions clearly associated with malfunction of the vasculature continue to be the leading causes of mortality and disability in medium and high-income countries, and they are on the rise in the rest of the world. Our grasp of a unified vasculature, a main pillar of whole-person health, has been inadvertently fragmented by the evolution of highly specialized knowledge silos. Vascular researchers and practitioners focusing on various areas of the same vascular system may spend their entire professional lives segregated into these knowledge silos, training and working in different academic and health care departments, using different scientific jargons, belonging to different professional societies, and attending different specialty conferences.

A life-long quest to understand the structure, function, and malfunction of the vasculature, in its many contexts, and to enable the design of effective clinical interventions has led the Editor of this book to the realization that further advances could well be accelerated by a collective reframing of future fundamental and clinical explorations of the vasculature so that we always consider any of its various parts as integral to its body-wide system. Since the vasculature is integrated not only in itself, but also within all the tissues across the entire body, one cannot fully grasp the developmental or functional underpinnings, including the malfunction, of any tissue or organ without considering its vasculature. All these considerations have led to our proposing the following concept of the vasculome.

The vasculome is an integrated, multiscale, multidimensional representation of the entire vasculature and its local and systemic interactions and functions within the body. The vasculome concept encompasses not only the entire physical blood and lymph vasculature, but also the body of knowledge obtained through different types of investigations about its local and unified nature and its essential importance to the human body's survival and function from the integrative perspective of "E pluribus unum: from many, one." The vasculature's systemic unity within the body is naturally achieved through the seamless integration of local structural and functional vascular variations. These variations are exquisitely adapted to support the survival and key functions across body's several size scales, from the single-cell level to the specialized multicellular organotypic functional tissue units (FTUs) that collectively support and define each organ's function, to whole tissues and organs—and ultimately to the entire body.

Answering fundamental and clinical questions about this complex integrated system usually requires breaking it down to manageable pieces to allow different types of investigations in various contexts. For instance, questions may require circumscribing investigations to one of the body areas or a defined size scale, at cell, tissue, or organ level, in specific research environments (e.g., clinical, experimental, in vivo, in situ, in vitro, or in silico), and using investigative tools applicable to those environments. The latest scientific and technological advancements have augmented the amount of multidimensional information we can amass about the vasculature. It is fair to say that our knowledge about the vasculome has many times circled back to the classical understanding of it, yet in an ever-expanding ascending spiral, knowledge is elevated at a new level when additional information is gained through the use of the latest sophisticated investigative methods. These new understandings compel us to find ways to rethink holistically about the essential contributions of the vasculome to human health and disease. They also support the vision that the vasculome could be personalized and predictive, which can help advance the clinical assessment and management of its local and systemic contributions in each one of us.

I am grateful to many leading vascular researchers who, in spite of the challenging times we have been weathering during the extended COVID pandemic, have answered the call to participate in the present Vasculome book project by providing their insights and examples to help flesh-in this concept, often challenging our existing assumptions about real or perceived boundaries of the vasculature. They remind our readers to approach knowledge about the vasculature guided by its nature-built integrative nature, for the vasculome is integrated within itself and within the body. Accordingly, this book highlights the fundamental bases of the unity in diversity of the vasculome, from its genesis in the coming together of various cell lineages during development, to its deceptively simple solution for architectural design: the efficient interplay of a few major types of building blocks that support vascular and other body-wide functions through highly specialized local functional variations. Finally, it hypothesizes the underpinnings of vascular dysfunction and its essential contributions to disease. To these ends, the book also presents some of the many investigative tools specific to the vasculome. The summaries appearing immediately below highlight main concepts presented in the various book sections; however, given the highly integrative nature of the vasculome, it is important to emphasize that these concepts could be organized—and should be connected by the reader—in many different ways. An interactive visualization tool has been built to show connections between the main topics of The Vasculome and is accessible from the book's web page.

Part I. The architectural design of the vasculome: basis for system-wide functional unity and local diversity

The earliest descriptions of human dissections support the idea of a unified vasculature, the physical basis of the vasculome. A lot of our understating of the vasculature comes from the later establishment of many in vitro, in situ, and in vivo investigative environments and methods which have advanced our knowledge by studying the vasculature's components in isolation, as briefly reviewed by Bautch (2022).

As suggested above, the nature-built, seamless body-wide integration of the vasculome's structure and function is achieved through the efficient interplay of a few types of specialized building blocks, different cell types and extracellular matrix (ECM) components. These are assembled in various combinations and proportions to create the specialized structural units representing different types of vessels carrying blood or lymph.

Every blood and lymphatic vessel is built upon the shared foundation of an innermost, single-cell thick, contiguous layer formed through the assembly of endothelial cells (ECs). While physically contiguous, the endothelial layer is assembled from different EC types essential for the survival and specific function of not only each specialized vascular structure, but also of all other cells within the entire body (Acharya et al., 2022; Becker et al., 2022; Gu and Cleaver, 2022). For instance, organotypic ECs are the central components of the multicellular specialized functional tissue units (FTUs) of various organs, such as the kidney, brain, or muscle (Cottarelli et al., 2022).

In various segments of the vasculature, the endothelium is overlayed by different types of successive concentric vascular layers formed through the assembly of various combinations of other vascular cell types (Cochain and Mallat, 2022; Fisher, 2022; Majesky, 2022; Sena, 2022), embedded and held together by the mortar-like ECM (Wagenseil et al., 2022). This efficient structural design suggests that various vascular segments could be reengineered through the successive application of their typical cellular and ECM layers on top of their specialized endothelial layer. Furthermore, a 3D print of any organ perhaps might be produced, first by creating its tubular network of one-cell thick endothelial layer upon which all other vascular cell types and ECM layers could be applied to build the organ's vasculature first, then continuing to add consecutive layers of various types of neighboring cells, all dependent on vasculature for survival, to eventually building up an entire organ from the inside-out.

Section 1. The endothelium as the key unifying principle of the vasculome. Basis for endothelial systemic unity and for engineering of local specialization

The endothelium, which creates the interface between all tissues and circulating blood or lymph, is a master sensor, mediator, and integrator (sensitive and responsive) of local and systemic signals. The physical continuity of the endothelial layer, which covers the inside of all blood and lymph vessels and the heart, creates the structural and functional unity of the vasculome throughout the body. In all blood vessels, large and small, throughout the body, the endothelial layer performs the same main key functions. It mediates blood–tissue exchanges, such as those involving oxygen and essential nutrients. It enables body-wide communication and integration via sensing and mediating physical and biochemical signals, as well as the controlled transfer of molecules and cells between blood, lymph, and all other tissues. It maintains a nonthrombogenic surface, and it participates in control of blood flow and immunosurveillance. At the same time, specialized adaptations to the unique needs of each of the different tissues and organs, whose survival and proper function depend on endothelium-mediated exchanges, are achieved through local variations in EC structure and function. In this respect, the endothelial layer is structurally and functionally central to not only integrating all the parts of the vasculome, but also to the integration of the vasculome within each body tissue perfused by blood vessels and drained by lymph vessels. Yet, likely because of its thin, one-cell thick dimensions, the endothelium is too easily forgotten or remains elusive in most clinical investigations. The vasculome concept addresses this oversight head on by placing the endothelium front and center. Several chapters are dedicated to describing the various bases of the Vasculome's unity in diversity that can be directly related back to the endothelium.

New single-cell analyses are expanding and deepening the knowledge about the in situ structural and functional heterogeneity of the endothelium (Acharya et al., 2022), revealed over decades using different investigative techniques, principally electron microscopy, perhaps the original technology allowing single-cell level analysis of the EC's structure and function in its native environments (Galis, 2022).

Some aspects of EC diversity and identity, both within the various blood and lymphatic vessel types, and within various organs, are genetically determined. Some are acquired early during organogenesis (Bautch, 2022; Gu and Cleaver, 2022) and even into adulthood. Maintenance of ECs' identity depends on their environment, which also plays an important role in maintaining the identity of various types of vessels (Dardik and Gonzalez, 2022). For instance, the ability to integrate different combinations of mechanical forces—including shear, pulsatile, and hydrostatic forces—in the various active environments of different vascular segments and body locations, and to translate them into biochemical signals, plays an essential role in acquiring and maintaining EC diversity and healthy functioning. The close relation between those mechanical forces and the ability of ECs to acquire and maintain normal function is supported by research showing that certain forces have differing effects on different EC types. For instance, oscillatory shear stress (OSS) is developmentally needed for lymphatic ECs to form normal valves, yet OSS triggers pathogenic pathways in arterial ECs that need laminar shear for their normal function (García-Cardeña and Gimbrone, 2022).

The local variation of endothelial structure and function is exquisitely adapted to support tissues' specific metabolic needs and functions, best demonstrated by the structural and functional diversity of organotypic capillaries, the simplest vascular structures (Rudnicki et al., 2022). Examples of the diversity of EC permeability include (1) the tight continuous ECs limiting blood–tissue exchanges to controlled transcellular routes, the main basis for the tight blood–brain barrier (BBB) (Cottarelli et al., 2022, Gu and Cleaver, 2022, Xing et al., 2022); (2) the fenestrated ECs forming the selective glomerular filtration barrier (GFB) of the kidney (Gu and Cleaver, 2022); and (3) the discontinuous ECs of lymph nodes, which allow transfer of entire cells (Jiang and Rockson, 2022). These specialized ECs participate at the core of the various types of FTUs that define and support each organ's main function. Their unity in diversity supports the important notion that due to the contiguity of the endothelial layer, all identical FTUs within an organ, as well as all the different types of FTUs of all the other organs, are physically and likely functionally, connected to each other, and also integrated within the entire vasculome. Respectively, the organotypic FTUs directly contribute to the integration of the vasculome within the architecture, environment, and specific function of all organs, explaining why the health of the vasculome is central to the health of each organ, as well as health overall.

The endothelium recruits other types of tissue-specific cells, not only during the development of the vasculature itself (Eichmann and Li, 2022), but also during the organogenesis of various tissues (Bautch, 2022). ECs meet high energetic demands during organogenesis and angiogenesis by relying mainly on glycolysis. Oxygen availability and EC metabolic state are emerging as determinants of arterial–venous specification. Beyond driving and orchestrating vascular development, organogenesis, and tissue patterning, the endothelium continues to produce angiocrine factors that are essential for the survival, function, and regeneration of other cells throughout adulthood (Bautch, 2022; Gu and Cleaver, 2022). Developmental EC programs may be reactivated during this time, as an appropriate response needed for repair and regeneration, but also inappropriately, as in the pathogenesis of some genetic or other diseases that have endothelial dysfunction as a main driver. The capacity of ECs to transdifferentiate into other cell types is an area of active research and debate because of its relevance to clinically significant processes, including tissue regeneration and vascular pathologies.

The endothelium has to be able to dynamically adapt to fluctuating nutrients, to tissue metabolic demands, to hemodynamic forces, and other to stimuli from both its luminal and tissue sides. Understanding the variety of EC types, subsets, and their different metabolic states is important for understanding tissue and organ function and the ability to intervene therapeutically (Becker et al., 2022; Rudnicki et al., 2022). Endothelial cells also participate in immune surveillance, signaling the need for, and mediating, the inflammatory response. The EC inflammatory gene repertoire is organ-specific and related to organ function and resilience/susceptibility. Activation of the endothelium in response to some of these challenges can lead to dysfunction (Munzel et al., 2022). Not surprisingly, endothelial dysfunction, which can be measured clinically (Quyyumi et al., 2022), has been associated with many local and systemic clinical conditions.

Section 2. Vasculome's key building blocks—beyond the endothelium

Various types of blood or lymphatic vessels are created through the combinatorial assemblage of a few types of vascular cells: endothelial and vascular smooth muscle cells, pericytes, as well as and other cells residing in the vascular ECM, further contributing to the overall unity and local specialization of various vascular segments within the vasculome (Dave et al., 2022, Jiang and Rockson, 2022, Liu and Oliver, 2022, Rudnicki et al., 2022). The physical and functional interactions between all these different types of building blocks create the basis for additional functions of the vasculome, including vascular reactivity, resistance, and vessel wall remodeling. The specific structure of every individual blood or lymph vessel supports its function within the local environment and its integration within the body wide vasculome.

The vascular smooth muscle cells (VSMCs) are the most abundant vascular cell type that invests the walls of vasculome's blood and lymph vessels. Understanding of the VSMCs' great diversity has continuously evolved. Thanks to a variety of new investigative approaches, the VSMC origin and life trajectory has been connected to the EC-driven orchestration of vascular development and patterning (Bautch, 2022; Gu and Cleaver, 2022). VSMC precursors from different embryonic origins are dynamically recruited to the nascent vasculature in response to its evolving local needs and mechanical cues, contributing to VSMC heterogeneity, not only in various parts of the vasculature but also within the same vascular segment (Majesky, 2022). The fundamental understanding of how VSMCs acquire heterogeneity, the connection between VSMC positional identity and vascular disease, and the mechanisms that either help maintain or work to change the identity of VSMC in different vascular beds and in various contexts of the vasculome (Fisher, 2022) have created bases for guiding development of interventional strategies to address local manifestation of vascular disease within a systemic vasculature. Pericytes, the mural cells of the microvasculature, also play important roles, perhaps best exemplified in their participation in the neurovascular unit (NVU) (Cottarelli et al., 2022; Xing et al., 2022).

New technologies also have allowed a new appreciation of the contribution of other cell types found to be associated with vascular structures, yet not traditionally considered to be vascular cells. We now know that some immune cells are legitimate residents of the normal vasculome. Playing an important surveillance function, these contribute to its homeostasis, as well as participate in the normal or pathological tissue remodeling that occurs in response to vascular injury and the development and progression of vascular diseases (Cochain and Mallat, 2022). The macrophage, the main type of inflammatory cell traditionally investigated in relation to the diseased vasculature, is now known to come in different flavors. Some vascular resident macrophages are adapted to performing specific homeostatic functions in various normal vascular beds, while others are recruited postnatally from circulating monocytes in inflammatory conditions associated with the development and progression of various vascular conditions, including formation of atherosclerotic lesions. A small number of neutrophils, mast cells, dendritic cells, and T cells (CD4+ and CD8+) also can be found in the normal arterial wall, and various lymphoid cells reside in the intima and adventitia of arteries and in perivascular structures, such as the perivascular-associated adipose tissue (PVAT), as well as in the microvasculature. Normal PVAT that contains adipocytes, vascular and immune cells, fibroblasts, and multipotent mesenchymal cells contributes to the homeostasis and vasoactivity of large arteries (Sena, 2022). Under pathological conditions, secondary lymphoid structures can develop within the PVAT (Cochain and Mallat, 2022), contributing to vascular dysfunction. Again, the local diversity of vascular cellular constituents is the basis for the diversity of vascular functions. Finally, changes in the normal cellular composition and the overall vascular landscape are associated with disease processes and aging.

Another crucial aspect of the connection between the characteristic structure and the function of each type of vessel is the composition and organization of its vascular ECM, which provides the cells with a structural framework, mechanical properties, mechanosensing, and other signals contributing to the overall cellular environment needed to perform local functions and to participate in the systemic activities of the vasculome (Wagenseil et al., 2022). The combinatorial assembly of various ECM components contributes to the distinct structural and functional identity of different types of vascular segments in various locations. This assembly closely correlates with the specific cellular composition, tissue organization, geometry, and function, as well as the type and magnitude of mechanical forces vessel wall cells have to create and withstand, as highlighted by the dire consequences of inborn errors of ECM-associated genes (Kaw et al., 2022). The ECM composition and assembly changes during development and aging, or in response to changes in the physical environment of blood vessels, which drive vascular tissue remodeling (Humphrey, 2022). These increase ECM turnover, triggering both synthesis of increased or different repertoire of ECM components, as well as increased production and action of ECM degrading enzymes. Such ECM changes are an essential component of normal adaptation and repair, but also contribute to the development and progression of various vascular diseases (Mohabeer and Bendeck, 2022). Far from being, as once thought, the amorphous filler between the cells, the ECM has emerged as one of the most fascinating and dauntingly multifaceted components of every tissue. Methods that would allow us to understand how this 3D complex assembled, yet dynamic, vascular ECM functions in its natural context are still lagging compared to those used to investigate cell function in situ.

Section 3. Putting it all together: vasculome integration across body scales and within tissues

The Vasculome concept calls for integration of vascular knowledge over the entire body and across its size scales, recapturing the nature-built vascular system design: seamlessly tapering from the large, stand-alone major blood vessels, which are among the longest and strongest anatomical structures in the body (macroscale), to the small vessels investing all organs (mesoscale), down to the single-cell scale of the smallest functional vascular structures that invest all tissues (microscale), the one EC-thick capillary tubes formed by one EC hugging itself.

The blood vasculature creates a body-wide closed circuit through the seamless hierarchical assembly of distinct structural units representing different types of blood vessels. Anatomical observations of the vascular system indicate once again its very efficient design: the road taken by oxygenated blood through the largest vessels to the smallest vessels only branches six times to reach any other cell within the body, and a similar, reversed branching pattern ensures blood's return to the heart from any location within the body. In addition, the lymphatic vasculature, mostly running in parallel to the blood vasculature, functions as an auxiliary backup system collecting fluid that has escaped into tissues and returning it via a unidirectional trip back into the blood vasculature (Jiang and Rockson, 2022).

This hierarchical design is most obvious in the building of the arterial system that tapers down from the aorta; the largest blood vessel, to large, elastic, and medium muscular arteries; then to smaller arterioles, to regulate blood flow and distribution to all organs and tissues. Arteries are built during development through the highly orchestrated integration of the greatest number and types of the various vasculome building blocks to create the anatomical structures needed to support pumping and conducting oxygenated blood, as well as to accomplish organ-specific functions (Dave et al., 2022). For instance, the hypoxic dilation of coronary arteries and sympathetic activation are needed to pump blood from the heart, while the hypoxic vasoconstriction of the pulmonary artery triggers blood oxygenation in the lungs. The serial design of the liver vasculature is needed for detoxification of blood received from the digestive organs, while in the kidney the afferent arterioles modulate hydrostatic pressure, and the efferent arterioles control the filtration rate. It is no surprise that arteries are the main contributors to vascular pathologies and systemic disease, such as atherosclerosis, aneurysm formation, peripheral arterial disease, or hypertension (Conte and Kim, 2022; Touyz et al., 2022). Mechanisms implicated in arterial pathology include reactivation of vascular developmental programs (Bautch, 2022), dysfunction of their various constituents, including the ECs (Becker et al., 2022; Munzel et al., 2022), VSMCs (Majesky, 2022), ECM (Kaw et al., 2022; Mohabeer and Bendeck, 2022), and vascular inflammation (Cochain and Mallat, 2022).

The theme of vascular diversity in the service of local tissue function is a major tenet of the vasculome, evident even at the smallest end of the vascular hierarchy and the simplest vascular structures, the capillaries, where most of the blood–tissue exchanges occur (Rudnicki et al., 2022). Organs usually contain different types of capillaries that support their survival, specific metabolic needs, and function (Gu and Cleaver, 2022). Much of the capillary specialization relies on the diversity of ECs, traditionally characterized in relation to their structural and functional features involved in transendothelial transport, i.e., continuous, fenestrated, or discontinuous endothelia, and a major basis for capillary specificity. New technologies have revealed that the variety of metabolic EC phenotypes contributes to normal EC identity in different tissues and to EC regenerative capacity, but also to EC transition to dysfunction and disease (Becker et al., 2022; Rudnicki et al., 2022). Such findings enhance the fundamental understanding of EC biology and suggest an important opportunity to use ECs to collect functional and spatial information about their local tissue milieu and neighboring cells (Galis, 2022).

Capillary specialization is essential for the function of various organ FTUs, which have organotypic ECs as their central elements. The intricate relationship between organ-specific ECs and other cell types forming their FTUs begins early in development and continues throughout the life of the FTUs. For instance, an intricate developmental dance, spanning the embryonic and postnatal stage, was shown to be needed for the proper formation of the tight barriers between blood and tissues in the brain, spinal cord, and retina: essential in supporting the function of their NVUs and maintaining their immune privilege (Cottarelli et al., 2022). Any changes in the normal properties of their continuous-type ECs, e.g., changes in tight junction integrity, low levels of transcytosis, and low expression of adhesion molecules, central for the BBB/blood–retina barrier (BRB), and NVUs, are associated with organ dysfunction and many pathologies, including stroke, multiple sclerosis, or retinal disease. Thus, the ability to assess organotypic EC function provides a very useful and sensitive way to monitor the functional state of the various organ specific FTUs, and perhaps diagnose and manage any changes detectible before overt clinical symptoms (Galis, 2022). Other capillary characteristics—including at the single-cell level (e.g., type and density of accompanying mural cells), or at the tissue level (e.g., the typical spatial capillary density and branching within the tissues)—are also essential for their ability to support local function and tissue metabolic needs (Secomb, 2022). Each tissue's microvascular networks create 3D identifiable vascular patterns that are indicative of normal or diseased states (Galis, 2022; Lee and Galis, 2022).

Blood and lymph are collected from the tissue and returned to the heart via veins and lymphatic vessels, based on a similar hierarchical vascular organization, only this time moving back through small then large size vessels. The specific structure of veins and lymphatic vasculature is adapted to their particular function and mechanical environment, although it is constituted from similar types of building blocks as those on the arterial side. The veins are an integral part of the closed circuit of the blood vasculature, while the lymphatic vasculature is largely paralleling and complementing the blood vasculature, and nevertheless inextricably related to it, developmentally, functionally, and structurally. The lymphatic vasculature unidirectionally returns filtrated lymph to the vein side of blood circulation, helping maintain interstitial fluid balance between tissues and the blood. It also supports reverse cholesterol transport by removing cholesterol from peripheral tissues and providing circulatory conduits for immune cell trafficking and dietary lipid absorption (Jiang and Rockson, 2022). Lymph collection and unidirectional flow are supported by specialized vascular features, such as buttons, valves, lymphangions, and the hierarchical organization of the lymphatic vasculature. The lymphatic vasculature also supports the functional integration of the various components of the lymphatic system, including primary and secondary organs. For instance, the filtering of interstitial fluid collected from different tissues through numerous lymph nodes is essential for immune priming and induction of peripheral tolerance. Inborn defects of lymphatic vasculature or malfunction secondary to interventions are causes for known lymphatic pathologies (El Amm et al., 2022; Jiang and Rockson, 2022) and contribute to other diseases (Liu and Oliver, 2022).

Part II. Investigating the vasculome: context-driven methods, uses, and limitations

The vasculome is investigated using some of the methods commonly used for other body tissues and organs, yet its characteristics also warrant specialized approaches. For instance, the advantages and limitations of studying cells taken out of their in situ natural context and cultured in vitro are widely recognized. However, culturing vascular cells, especially ECs, warrants additional consideration, related to the difficulties of (1) harvesting viable and sufficient number of ECs from endothelial monolayers or from among the many other cell types of various tissue samples and (2) recreating in vitro the physically active environment necessary for maintaining vascular cell identity and function. A work-around has been to isolate human vascular cells from the more readily available vessels, e.g., ECs from discarded human umbilical veins or VSMCs of saphenous veins harvested for vascular grafts, and then to propagate and maintain these cells for several generations in the traditional static cell culture conditions.

Reports on the activities of specific types of vascular cells maintained and propagated under static conditions in vitro may not be representative of those of corresponding cell types of other vessels, e.g., of the ECs of other types of arteries, veins, or microvasculature, or even of their own their behaviors within their native mechanically active environments.

Section 1. Experimental and computational studies of the vasculome

The close spatial association between atherosclerotic lesions and areas of arteries experiencing complex blood flow patterns has led to early investigations of a potential causal effect of disturbed shear stress. Several in vitro systems have been built to directly investigate the effect of different shear stress patterns upon the structure and function of ECs (García-Cardeña and Gimbrone, 2022). The use of such in vitro systems has allowed researchers to demonstrate that steady laminar flow may be atheroprotective because it is associated with the expression of genes supporting antithrombotic, antiadhesive, antiinflammatory, and antioxidant activities, while the expression of these genes is reduced or absent in areas with disturbed flow, giving rise to the Atheroprotective Gene Hypothesis. Through the application of various in vitro flow stimulator models, the Kruppel-like factor (KLF) 2 has emerged as a key atheroprotective transcription factor. Such experiments have also unraveled molecular pathways activated by blood flow, creating opportunities for new therapeutic approaches in atherosclerosis.

An advantage of in vivo experiments is that they allow for interrogation of the effects of systemic factors such as sex, race, age, and of systemic conditions such as obesity or diabetes on the structure and function of vasculature and its components in various body locations and contexts. These effects are still not systematically examined, although many have been found to be independently associated with cardiovascular disease. In vivo experiments also provide the most comprehensive way to study the effects of various therapeutic interventions. Most in vivo investigative methods are currently applicable only in experimental conditions. For instance, in vivo observations of blood flow, transendothelial transport, and regulatory processes are revealing, but particularly challenging in the dynamic metabolic and mechanical environments of the microvasculature. Label-free and minimally invasive in situ imaging of microvascular function and oxygen metabolism by intravital photoacoustic microscopy (Sun and Hu, 2022) has allowed multiparametric imaging of the cerebrovascular structures in the awake rat brain, including comprehensive and quantitative characterization of their structure (density, tortuosity), mechanical properties (e.g., wall shear stress, resistance, and reactivity), hemodynamics (e.g., blood perfusion, oxygenation, and flow speed), and the associated tissue oxygen extraction and metabolism. Despite any limitations, in vivo and in situ experimental methods provide important information that can be used in conjunction with theoretical modeling to predict parameters for vascular segments that cross boundaries and for which experimental information about flow and oxygen levels is incomplete (Secomb, 2022). Understanding these phenomena requires a network-oriented approach to analyzing vascular function.

Simulations of blood flow have to consider the hierarchical branching structure of the vasculome, which seamlessly connects the largest to the smallest vascular structures with inner diameters of the vascular space available to carry blood that vary over four orders of magnitude. Different dynamic regimens are at work in large vessels, as compared to those in smaller ones whose diameters approach the size of the red blood cells passing through them. Other geometrical parameters, such as vascular segment length, bifurcations, curvatures, etc., vary widely. All these variations result in complex blood flow patterns, creating variations in blood shear stress, which are sensed and acted upon by the inner EC lining of the vasculature. Pathological conditions involve various changes in vascular geometry, during which the physiological adaptive reaction of the vasculature may fail to restore normal blood flow, which brings other systems into play. Physics of oxygen transport simulation allows us to calculate values of parameters such as tissue perfusion and oxygen extraction, which can be used to predict the effects of various changes in blood flow or those due to variations in oxygen demand. These simulations are valuable for predicting key characteristics driving vascular function or dysfunction, especially for the natural in situ environments where experimental information is very difficult to obtain. They can also be used to inform experiments with isolated vascular cells or vessels. For instance, estimates of complex flow hemodynamic conditions have been used to develop in vitro systems allowing for testing the effects of different flow patterns upon cultured ECs (García-Cardeña and Gimbrone, 2022).

Combining simulation and in vitro experimentation has also been used to dissect intracellular pathways involved in interactions between ECs and other cell types, to enable predictions at the systemic level, as various ECs share many common nodes: molecules that act as master regulators of multiple processes. For instance, models have been developed for cellular interactions between ECs and macrophages during angiogenesis, a multifactorial process driven by hypoxia (Eichmann and Li, 2022) that is essential in tissue development and repair, but also can fuel pathology, thus has important translational applications (Zhang et al., 2022).

Clinical investigations of endothelial and vascular function are essential to assessing overall health (Quyyumi et al., 2022).Various risk factors and genetics contribute to endothelial dysfunction, which has been shown to be an independent predictor of future development of hypertension, diabetes, or atherosclerosis, and a predictor of progression toward future adverse cardiovascular