In vitro reendothelialization of a single-cell wound. Role of microfilament bundles in rapid lamellipodia-mediated wound closure.

The mechanism and regulation of reendothelialization of small aortic endothelial wounds is not well understood. An in vitro model system was designed to study the repair of a wound created by the removal of a single endothelial cell from a confluent monolayer. Time-lapse cinemicrophotography was used to characterize the kinetics of wound repair. Because all of the endothelial cells adjacent to the wound extruded lamellipodia to rapidly close the wound within 30 to 45 minutes, the repair process was referred to descriptively as rapid lamellipodia-mediated wound closure. Treatment of the wounded cultures with cytochalasin B resulted in a marked decrease in lamellipodia extrusion and a significant delay in wound closure. Washout of cytochalasin B resulted in the reappearance of lamellipodia extrusion and the rapid closure of the wound. Localization of actin microfilaments by 7-nitrobenz-2-oxa-1,3-diazole phallicidin in control and cytochalasin B-treated wounds showed that rapid lamellipodia-mediated wound closure was associated with the presence of a dense peripheral band of actin microfilament bundles normally located around the periphery of each endothelial cell in the confluent monolayer. The results suggest that the process of single-cell wound repair is a function of lamellipodial extrusion which itself may be regulated, at least in part, by the actin-containing dense peripheral band of microfilament bundles located at the periphery of endothelial cells in confluent monolayers.