Capillary growth of rat aortic segments cultured in collagen gel without serum

The process of angiogenesis was studied under serum-free conditions using rat aortic segments in three-dimensional collagen gel. In serum-free and growth-factor free conditions, the capillaries formed networks and tube-like structures, and the endothelial cells produced von Willebrand factor, laminin and type IV collagen, but the number of capillaries was lower and their growth was slower than in medium containing 20% fetal calf serum (FCS). Incorporation of bromodeoxyuridine (BrdU) and inhibition of growth by hydroxyurea suggested that capillary growth depended mainly on cell proliferation and not on migration. Capillary growth in PRMI 1640 or DMEM was similar and more efficient than in MEM. Only slight growth was seen in Medium 199 and HAM-F12. The addition of serum to the medium accelerated capillary growth in proportion to the amount added. In serum-free conditions, ITS(+) and fibroblast growth factor (FGF) promoted capillary growth, but not to a significant extent. There ware no differences in capillary growth among the gel matrices used (type I collagen, type I + II collagen, type I + IV collagen, fibrin and plasma clot).