Induction of apoptotic cell death in vascular endothelial cells cultured in three-dimensional collagen lattice

Endothelial cells derived from fetal bovine aorta (BAECs) undergo apoptosis in three-dimensional (3-D) type I collagen lattice in the absence of specific angiogenic factor. In the presence of angiogenic factor, BAECs survive and form a capillary-like tube structure in 3-D culture. In the present study we elucidate the mechanisms of BAECs apoptosis or survival and tube formation in 3-D culture, When BAECs embedded in collagen lattice were cultured with angiogenic factor (fibroblast growth factor-a (FGF-S) or 4 beta-phorbol la-myristate 13-acetate (PMA)) in the presence of PD98059, a specific inhibitor of mitogen-activated protein kinase kinase, BAECs did not form tube structures and underwent apoptosis in collagen lattice. Function-blocking antibody against alpha v beta 3 integrin also inhibited tube formation and induced apoptosis in 3-D culture in the presence of angiogenic factors. Exposure of BAECs to FGF-S and PMA had no effect on the (alpha v beta 3 integrin expression but induced the activation of alpha v beta 3 integrin. PD98059 attenuated alpha v beta 3 integrin activation in response to angiogenic factor. KB-R8301, a hydroxamic acid-based matrix metalloproteinase (MMP) inhibitor, prevented apoptotic cell death in the absence of angiogenic factor in 3-D culture and enhanced capillary-like tube formation in the presence of angiogenic factor, which was not inhibited by the anti-alpha v beta 3 integrin antibody. The results suggest that angiogenic factor-induced alpha v beta 3 integrin activation through the MER-ERK pathway regulates the BAEC fate between apoptosis and angiogenesis in collagen lattice. MMP derived from BAECs seems to play a key role in the release of cryptic ligands for alpha v beta 3 integrin from intact collagen. (C) 1999 Academic Press.