The angiogenic factor, basic fibroblast growth factor (FGF), either stimulates endothelial cell growth or promotes capillary differentiation depending upon the microenvironment in which it acts. Analysis of various in vitro models of spontaneous angiogenesis, in combination with time-lapse cinematography, demonstrated that capillary tube formation was greatly facilitated by promoting multicellular retraction and cell elevation above the surface of the rigid culture dish or by culturing endothelial cells on malleable extracellular matrix (ECM) substrata. These observations suggested to us that mechanical (i.e., tension-dependent) interactions between endothelial cells and ECM may serve to regulate capillary development. To test this hypothesis, FGF-stimulated endothelial cells were grown in chemically defined medium on bacteriological (nonadhesive) dishes that were precoated with different densities of fibronectin. Extensive cell spreading and growth were promoted by fibronectin coating densities that were highly adhesive (greater than 500 ng/cm2), whereas cell rounding, detachment, and loss of viability were observed on dishes coated with low fibronectin concentrations (less than 100 ng/cm2). Intermediate fibronectin coating densities (100-500 ng/cm2) promoted cell extension, but they could not completely resist cell tractional forces. Partial retraction of multicellular aggregates resulted in cell shortening, cessation of growth, and formation of branching tubular networks within 24-48 h. Multicellular retraction and subsequent tube formation also could be elicited on highly adhesive dishes by overcoming the mechanical resistance of the substratum using higher cell plating numbers. Dishes coated with varying concentrations of type IV collagen or gelatin produced similar results. These results suggest that ECM components may act locally to regulate the growth and pattern-regulating actions of soluble FGF based upon their ability to resist cell-generated mechanical loads. Thus, we propose that FGF-stimulated endothelial cells may be "switched" between growth, differentiation, and involution modes during angiogenesis by altering the adhesivity or mechanical integrity of their ECM.

https://rupress.org/jcb/article-pdf/109/1/317/1058123/317.pdf

Mechanochemical switching between growth and differentiation during fibroblast growth factor-stimulated angiogenesis in vitro: role of extracellular matrix.

Angiogenesis in wound healing.

Tumor interactions with the vasculature: angiogenesis and tumor metastasis.

The blood vessels vascularizing the central nervous system exhibit a series of distinct properties that tightly control the movement of ions, molecules, and cells between the blood and the parenchyma. This "blood-brain barrier" is initiated during angiogenesis via signals from the surrounding neural environment, and its integrity remains vital for homeostasis and neural protection throughout life. Blood-brain barrier dysfunction contributes to pathology in a range of neurological conditions including multiple sclerosis, stroke, and epilepsy, and has also been implicated in neurodegenerative diseases such as Alzheimer's disease. This review will discuss current knowledge and key unanswered questions regarding the blood-brain barrier in health and disease.

https://rupress.org/jem/article-pdf/217/4/e20190062/1173545/jem_20190062.pdf

The blood-brain barrier in health and disease: Important unanswered questions.

Tissue Culture of Endothelial Cells.- Culture and identification of large vessel endothelial cells.- Culture of capillary endothelial cells.- Culture of endothelial cells from neural capillaries.- Culture of pulmonary endothelial cells on microcarrier beads.- Construction of an artificial blood vessel wall from cultured endothelial cells.- Determinants of Endothelial and Smooth Muscle Cell Growth.- Growth requirements for bovine aortic endothelium in vitro.- Contact inhibition in the endothelium.- Endothelial cell motility.- Factors which stimulate the growth of human umbilical vein endothelial cells in vitro.- Macrophages, neovascularization, and the growth of vascular cells.- The limited life-span of bovine endothelial cells.- Endothelium, heparin, and the regulation of vascular smooth muscle cell growth.- Morphology of Cultured Endothelial Cells.- Morphology of vascular endothelial cells in culture.- The endothelial cytoskeleton.- Synthesis of Connective Tissue Elements by Endothelial Cells.- Metabolism of thrombospondin and fibronectin by endothelial cells.- Collagen synthesis by endothelial cells in culture.- Sulfated glycosaminoglycans and vascular endothelial cells.- Elastin synthesis by endothelial cells.- Gene mapping using hybrids of human endothelial cells and rodent fibroblasts.- Interactions of Endothelial Cells with the Coagulation and Complement Systems and Formed Elements in Blood.- Properties of plasminogen activators produced by endothelial cells.- Synthesis of Factor VIII by endothelial cells.- Tissue factor activity of cultured human vascular cells.- Activation of Hageman factor by cultured rabbit endothelial cells.- Prostacyclin production by endothelial cells.- Regulation of endothelial cell function by cyclic nucleotides.- Interactions of thrombin, antithrombin III, and Protein C with endothelium.- Viral infection of endothelium and the induction of Fc and C3 receptors.- Adhesive interactions between polymorphonuclear leukocytes and endothelium.- Neutrophil endothelial interactions.- Synthesis of colony stimulating activity by endothelial cells.- Interaction with and Metabolism of Plasma Components by Endothelial Cells.- The metabolism of vasoactive peptides by human endothelial cells.- The metabolism of angiotensin I and bradykinin by endothelial cells.- Metabolism of serotonin and adenosine.- Receptors for insulin and multiplication stimulating activity (MSA) in endothelial cells.- Binding of lipoprotein lipase to cultured endothelial cells.- Role of lipoproteins in the regulation of cultured endothelial cell cholesterol metabolism.- Quantitative aspects of endocytosis in cultured endothelial cells.- Immunologic Aspects of Endothelial Cells.- The alloantigens of endothelial cells.- Accessory cell function of human endothelial cells: presentation of antigen to T cells.- Cell surface markers on endothelial cells: a developmental perspective.- Endothelial Cell and Vasular Prostheses.- Endothelial seeding of vascular prostheses.- Endothelial Cells and Cancer.- Angiogenesis.- Synthesis of collagenase and plasminogen activator by endothelial cells.- In vitro systems for studying the interaction of metastatic tumor cells with endothelial cells and subendothelial basement membranes.

Biology of endothelial cells

The ultrastructural organization of ruthenium red (RR) stainable material within small blood vessels located in the limbus of the rabbit eye was studied. Proteoglycans were identified in this material by digesting tissues with Streptomyces hyaluronidase, testicular hyaluronidase, chondroitinase ABC, or heparinase before ruthenium red staining. Neuraminidase digestion enabled separate identification of sialoglycoprotein. The luminal surface of endothelial cells demonstrates an RR-stained glycocalyx containing both sialoglycoprotein and proteoglycans, which are removed by testicular hyaluronidase and crude heparinase. The basal coat of endothelial cells and small granules (10-20 nm in diameter) located within the basal lamina stain with RR and are removed only by crude heparinase. The surface coat of smooth muscle cells and small granules (10-20 nm) within their basal laminas are also digested by crude heparinase. Large proteoglycan granules (20-50 nm), which are completely removed by testicular hyaluronidase and partially digested by Streptomyces hyaluronidase, are deposited between the connective tissue fibers of the media and adventitia. Other large granules that are attached to collagen fibers contain enzyme-resistant anionic materials. The surface coat of adventitial fibroblasts is removed only by crude heparinase. Thin filaments (3-5 nm in diameter) interconnect the cell coat material, basal lamina granules, and large connective tissue granules, to form a network of proteoglycans that traverses the intima, media, and adventitia. The highly ordered arrangement of proteoglycans in the microvascular wall suggests that these macromolecules play several roles in microvascular function.

Proteoglycans in the microvasculature. I. Histochemical localization in microvessels of the rabbit eye.

The ultrastructural distribution of proteoglycans around capillaries growing in the cornea of the rabbit eye was determined after staining with ruthenium red (RR). Proteoglycans were identified by digesting tissues with glycosaminoglycan-degradative enzymes. Sialoglycoproteins were differentiated from proteoglycans by neuraminidase digestion. The capillary sprouts demonstrated a luminal glycocalyx containing testicular hyaluronidase-sensitive proteoglycans but little or no sialoglycoprotein. At the capillary tips, where mitosing and migrating endothelial cells are located, the basal cell surface displayed a network of small RR-stained granules (8 nm in diameter), which was partially removed by streptomyces hyaluronidase but not by testicular hyaluronidase. Thin filaments connected the granules to the endothelial cell plasmalemma and to a similar network of granules that is normally present in the corneal stroma. The stroma granules were partially digested by testicular hyaluronidase. In older capillary regions, where endothelial cells ceased proliferation, the basal network of proteoglycan granules was gradually infiltrated by fibrillar material until a basal lamina was formed. The proteoglycan granules were then arranged on both sides of the lamina densa, and a thin glycocalyx covered the basal endothelial cell surface. Thus, proteoglycans and anionic materials associated with growing capillaries serve to link proliferating and migrating endothelial cells to the extracellular matrix, help to organize the capillary basal lamina, form an anionic surface along the luminal front of capillaries, and probably help stabilize the structure of the capillary wall after proliferation ceases.

Proteoglycans in the microvascular. II. Histochemical localization in proliferating capillaries of the rabbit cornea.

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Proteoglycans in the microvasculature. I. Histochemical localization in microvessels of the rabbit eye.

Proteoglycans in the microvascular. II. Histochemical localization in proliferating capillaries of the rabbit cornea.