Fibrin-enhanced endothelial cell organization

The formation of cloned bovine endothelial cells into capillary‐like tubes is accelerated from 3–7 days to 2–18 h in the presence of fibrin. Indirect immu‐nofluorescence showed the presence of both fibrin and fibronectin in the strands along which the cells organized. Electronmicroscopy revealed the same type of cell structures as form in the absence of fibrin; it also revealed a gradual decrease with time of the fibrin within the putative lumen. Fibrin and fibronectin are commonly present during angiogenesis in vivo, thus these in vitro observations may well have relevance to the in vivo process.