Disorganization of cultured vascular endothelial cell monolayers by fibrinogen fragment D

Fibrinogen fragment D, which is heterogeneous, has several important biological functions. Human fibrinogen fragments D₉₄ (molecular weight, 94,000), D₇₈ (78,000), and E (52,000) were purified. Fragments D₇₈ and D₉₄ but not purified fibrinogen or fragment E specifically caused disorganization of bovine aortic endothelial cells cultured as monolayers. Within 2 hours of exposure to pathophysiological concentrations of fragment D, the confluent endothelial cells retracted from each other and projected pseudopodia. These disturbed cells subsequently became rounded and detached from the substrate. The actin present in stress fibers in stationary monolayer cells was diffusely redistributed in cells with fragment D-induced alterations in morphology. This effect was not observed in monolayers of kidney epithelial cells. The results demonstrate a specific effect of fibrinogen fragment D on the disorganization of cultured vascular endothelial cell monolayers and suggest that fragment D plays a role in the pathogenesis of syndromes with vascular endothelial damage.