Extracellular matrix specificity for the differentiation of capillary endothelial cells.

Capillary endothelial cells in a fenestrated vasculature contain openings in attenuated areas of the cytoplasm which are often covered with one or two diaphragms. However, due to endothelial cell dedifferentiation upon culturing, such indicative membrane structure are often not expressed. The expression of a more differentiated phenotype can be regulated by the extracellular matrix to which the cells attach. In addition, during angiogenesis endothelial cell migration enables their interaction with other cell types and matrices which may directly affect endothelial cell growth and function. We report the ability to modify the expression of diaphragmed fenestrations and transcapillary channels in capillary endothelial cells by specific extracellular matrices. When the number of membrane openings is measured, growth of the cells on Madin--Darby canine kidney cell matrix results in the greatest number while other matrices or isolated matrix components are only partially active. Production of such a biologically active matrix not only allows an avenue to identify fenestrae-associated proteins but also provides an easy culture method to more closely mimic the in vivo phenotype of endothelial cells.