Inhibition of vascular endothelial cell morphogenesis in cultures by limbal epithelial cells

PURPOSE. To study the in vitro angiogenic activity of human conjunctival an d limbal epithelial cells and conjunctival, limbal, and corneal fibroblasts in a three-cell-type coculture model. METHODS. Human umbilical vein endothelial cells (EC) were cocultured with e pithelial cells, fibroblasts, or epithelial cells and fibroblasts to test t heir effect on EC morphogenesis. Neutralizing antibodies to some known angi ogenic factors were added to the culture to see whether the EC morphogenesi s may be blocked by a particular antibody. RESULTS. Conjunctival and limbal epithelial cells exhibited very little or no stimulatory effect on EC tube formation when examined in an EC-epithelia l cell coculture system. In contrast, conjunctival, limbal, and corneal fib roblasts all promoted EC morphogenesis when examined under the same culture conditions. Fibroblast-induced EC morphogenesis was inhibited by addition of anti-vascular endothelial growth factor (VEGF) and/or anti-basic fibrobl ast growth factor (bFGF) antibodies to the culture medium. In the three-cel l-type coculture system consisting of ECs, fibroblasts, and epithelial cell s, limbal epithelial cells (but not conjunctival epithelial cells) exhibite d a strong inhibitory effect on fibroblast-induced EC tube formation. CONCLUSIONS. The proangiogenic activity of ocular surface fibroblasts is pr obably mediated through a paracrine mechanism by VEGF and bFGF. Limbal epit helial cells, but not conjunctival epithelial cells, inhibit fibroblast-sti mulated angiogenesis.