Endothelial wounds with disruption in cell migration repair primarily by cell proliferation

Disruption of vascular integrity results in activation of endothelial cells to initiate repair. Cytoskeletal reorganization, cell spreading, migration, and proliferation are important processes which regulate rapid and efficient repair. Cell proliferation has been thought to be a secondary event and dependent to a large extent on prior cell migration. We used a model of dysfunctional repair to test the hypothesis that a reduction in migration will result in a reduction in cell proliferation. The extent of cell proliferation was studied in an in vitro repair model, in which endothelial function is studied during the closure of a 1500-microns mechanically induced wound in a confluent monolayer. Dysfunctional repair is induced in this model by transiently inhibiting endothelial cell transcription. Wounds are incubated with actinomycin D at the time of wounding for 2 hr, which results in wound closure taking about 4.5 times longer than normal. Cell proliferation is measured by 5-bromo-2'-deoxyuridine incorporation. In actinomycin D-treated wounds, the rate of cell migration is reduced, and for the first 120 hr very little cell proliferation occurs and it involves the first 4 rows of cells adjacent to the wound edge. This is in comparison to normal wounds in which proliferation is prominent by 24 hr after wounding, also involving the first 4 rows of cells and by 48 hr, proliferation extends to involve the first 10 rows of cells. In dysfunctional wounds, however, it takes 144 hr after wounding before the first 10 rows of cells begin to actively proliferate. In addition, proliferation occurs deeper in the monolayer and this level is maintained over the next 144 hr, when the wound closes. Thus, when migration is reduced, proliferation becomes prominent and persists to complete repair. However, the overall rate of repair is reduced.