SERUM-FREE IN-VITRO MODEL OF RENAL MICROVESSEL DEVELOPMENT

The differentiation and organization of the embryonic renal vasculatur e is a crucial event in renal development. To study this process, we d eveloped a serum-free in vitro model of renal microvessel development. Mouse embryonic kidney explants, when embedded specifically in type I collagen, demonstrate outgrowth of microvascular structures when stim ulated by the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA, 10-50 ng/ml). Other polypeptide growth factors stimulated little, if any, microvessel outgrowth from the explants. Similar outgrowths were not observed when other embryonic tissue explants were used. The numbe r of microvessels observed depended on the gestational age of the expl ants. We hypothesize that TPA induces the in situ differentiation of m etanephric mesenchymal cells into endothelial cell precursors and that specific matrix proteins and cell-matrix interactions are necessary f or the organization of these precursors into microvessels. Our model w ill allow us to examine in detail the responsiveness of metanephric ki dney cells to both growth factors and extracellular matrix molecules a nd to understand how they influence renal endothelial cell differentia tion.