Biology Of Endothelial Cells

The participation of endothelial cells in various physiologic and pathologic processes has been hypothesized since before the turn of the century. However, until recently, direct evidence for endothelial involvement in these processes has been extremely difficult to obtain due to the inability to study endothelial cell function in vitro. Though the possibility of using cultured endothelial cells to study endothelial cell function in vitro was recognized many years ago, the inability to culture unambiguously identifiable endothelial cells limited investigators in their studies of endothelial function. As a result, the field of endothelial cell biology lay relatively fallow for many years. The development in the early 1970's of routine and easily implemented methods for culturing human endothelial cells and the demonstration that cultured endothelial cells synthesized a physiologically relevant protein, Factor VIII/von Willebrand Factor, quickly changed this state of affairs. Over the following decade the scope of endothelial cell research rapidly widened, spreading in a number of directions. First, methods were developed to culture endothelial cells from a variety of species. Second, methods were developed to culture endothelial cells from different organs and types of blood vessels (arteries, veins, and capillaries) within a single species. Third, and most important, investigators began using cultured endothelial cells as tools to study the potential involvement of endothelial cells in a wide assortment of biologically interesting processes. The net result has been a tremendous increase in our understanding of endothelial cell function.

Although blood capillaries were first observed through a flea-lens microscope by Malpighi in 1661,200 more years elapsed before the cellular nature of the vessel wall was conclusively demonstrated. Beginning with the middle of the 19th cen tury, our knowledge of the histological organization of blood vessels has steadily increased. However, the endothelium, which for a long time was considered to be just an inert barrier lining, had been barely explored until three decades ago. Since then, there has been an upsurge of interest in the fine structure and function of endothelial cells. Intense in vivo and in vitro investigations have revealed that the endothelial cell is a key element in a wide variety of normal activities and diseases. A large number of investigators and laboratories have been attracted to endothelial cell research, thus supporting the expansion of the continuously grow ing and diversifying field of endotheliology. The number of articles published annually on this subject has increased from a few score at the beginning of the 1970s to more than a thousand in recent years, and an increasing number of journals, books, societies, and symposia focused primarily on the vascular en dothelium have marked the last decade.

The endothelium, a monolayer of endothelial cells, constitutes the inner cellular lining of the blood vessels (arteries, veins and capillaries) and the lymphatic system, and therefore is in direct contact with the blood/lymph and the circulating cells. The endothelium is a major player in the control of blood fluidity, platelet aggregation and vascular tone, a major actor in the regulation of immunology, inflammation and angiogenesis, and an important metabolizing and an endocrine organ. Endothelial cells controls vascular tone, and thereby blood flow, by synthesizing and releasing relaxing and contracting factors such as nitric oxide, metabolites of arachidonic acid via the cyclooxygenases, lipoxygenases and cytochrome P450 pathways, various peptides (endothelin, urotensin, CNP, adrenomedullin, etc.), adenosine, purines, reactive oxygen species and so on. Additionally, endothelial ectoenzymes are required steps in the generation of vasoactive hormones such as angiotensin II. An endothelial dysfunction linked to an imbalance in the synthesis and/or the release of these various endothelial factors may explain the initiation of cardiovascular pathologies (from hypertension to atherosclerosis) or their development and perpetuation. Table of Contents: Introduction / Multiple Functions of the Endothelial Cells / Calcium Signaling in Vascular Cells and Cell-to-Cell Communications / Endothelium-Dependent Regulation of Vascular Tone / Conclusion / References

Endothelial cell biology has developed into a vibrant discipline and has become a critical instrument to study several disease processes on the cellular and molecular level. It is now widely recognized that dysfunctions of normal endothelial cell homeostasis are involved in some of the most important human diseases, including ischemic heart diseases, hypertension, atherosclerosis, tumors, diabetes, arthritis, and inflammation. Further, the increasing importance and recognition of the field of vascular biology in general requires in vitro and in vivo techniques in order to address the complex questions. Methods in Endothelial Cell Biology is a comprehensive practical "how-to"-guide summarizing the most relevant established techniques as well as a number of new emerging techniques. Easy-to-follow reliable protocols provide a useful lab bench resource for the experienced researcher and newcomer to the field.

Endothelial cells are early targets of radiation injury. Because these cells are tissues easily damaged by radiation, if we can understand the causes of radiation injury, then normal cells can be well protected and tumors can be destroyed. The Radiation Biology of the Vascular Endothelium brings together expert reviews on the biology and radiobiology of the vasculature, with emphasis on the endothelial cell component of blood vessels. The book covers both the basic aspects of endothelial cell biology and the practical consequences of this for the oncologist, with special reference to the radiation oncologist. After reading The Radiation Biology of the Vascular Endothelium, no clinical or experimental oncologist should be able to ignore the intimate relationship between tumor and normal tissue cells and endothelial cells that form the barrier to, and are the bearers of, essential nutrient supplies.

The aim of the Handbooks in Practical Animal Cell Biology is to provide practical workbooks for those involved in primary cell culture. Each volume addresses a different cell lineage, and contains an introductory section followed by individual chapters on the culture of specific differentiated cell types. The authors of each chapter are leading researchers in their fields and use their first-hand experience to present reliable techniques in a clear and thorough manner. Endothelial Cell Culture contains chapters on endothelial cells derived from 1) lung, 2) bone marrow, 3) brain, 4) mammary glands, 5) skin, 6) adipose tissue, 7) female reproductive system, and 8) synovium.

The vascular endothelium lining the inner surface of blood vessels serves as the first interface for circulating blood components to interact with cells of the vascular wall and surrounding extravascular tissues. In addition to regulating blood delivery and perfusion, a major function of vascular endothelia, especially those in exchange microvessels (capillaries and postcapillary venules), is to provide a semipermeable barrier that controls blood–tissue exchange of fluids, nutrients, and metabolic wastes while preventing pathogens or harmful materials in the circulation from entering into tissues. During host defense against infection or tissue injury, endothelial barrier dysfunction occurs as a consequence as well as cause of inflammatory responses. Plasma leakage disturbs fluid homeostasis and impairs tissue oxygenation, a pathophysiological process contributing to multiple organ dysfunction associated with trauma, infection, metabolic disorder, and other forms of disease. In this book, we provide an updated overview of microvascular endothelial barrier structure and function in health and disease. The discussion is initiated with the basic physiological principles of fluid and solute transport across microvascular endothelium, followed by detailed information on endothelial cell–cell and cell–matrix interactions and the experimental techniques that are employed to measure endothelial permeability. Further discussion focuses on the signaling and molecular mechanisms of endothelial barrier responses to various stimulations or drugs, as well as their relevance to several common clinical conditions. Taken together, this book provides a comprehensive analysis of microvascular endothelial cell and molecular pathophysiology. Such information will assist scientists and clinicians in advanced basic and clinical research for improved health care.