HETEROGENEITY IN COLLAGEN BIOSYNTHESIS BY SPROUTING RETINAL ENDOTHELIAL-CELLS

Bovine retinal microvascular endothelial cells can display two distinc t and reversible morphologies in culture: 'cobblestone' and 'sprouting '. The cobblestone morphology resembles the resting cells lining the l umen of mature vessels while the sprouting morphology resembles the an giogenic cells involved in the formation of new vessels. Retinal cells displayed some heterogeneity in the shape of the cells making up the cobblestone monolayer. In contrast, all cell lines displayed an identi cal sprouting morphology. We have investigated the synthesis of matrix macromolecules by retinal endothelial cells displaying either the cob blestone or the sprouting morphology. Type IV was the only collagen sy nthesised by eight different lines of early-passage (between one and s ix) cobblestone endothelial cells. Collagen types I and III were not d etected in these cultures. In contrast, heterogeneity was observed in the types of collagen synthesised by four lines of early-passage cells displaying the sprouting morphology. That is, two lines synthesised c ollagen types I, III and IV, whereas two other lines continued to synt hesise only type IV collagen. Both cobblestone and sprouting cells syn thesised fibronectin and thrombospondin, although the relative amounts of these macromolecules varied with culture conditions. The pattern o f collagen synthesis by cobblestone cells was also affected by in vitr o ''ageing'': 4/5 lines examined above passage eight synthesised colla gen types I, III and IV. Our results indicate that there is heterogene ity in the sprouting phenotype displayed by retinal endothelial cells, and that this phenotype is not necessarily associated with the synthe sis of type I collagen. We suggest that differences in the spectrum of matrix macromolecules synthesised by sprouting endothelial cells may play a role in the control of angiogenesis. (C) 1994 Wiley-Liss, Inc.