In vitro reendothelialization. Microfilament bundle reorganization in migrating porcine endothelial cells.

An experimentally induced wound made in a confluent monolayer culture of porcine thoracic aortic endothelial cells (ECs) was studied 22 hours after wounding using 7-nitrobenz-2-oxa-1,3-diazole (NBD) phallacidin and immunofluorescence microscopy to localize actin and myosin containing microfilament (MF) bundles. ECs extending from the wound edge back toward the confluent monolayer showed a specific change in cell shape and in MF bundle distribution and orientation, which correlated with the cell migration behavior observed using time-lapse cinemicrophotography. The migrating ECs in the first zone, the leading zone, were polygonal to partially elongated in shape, and contained distinct central MF bundles oriented both parallel and perpendicular to the wound edge. The second zone, the elongated zone, was characterized by elongated cells with central MF bundles oriented parallel to the direction of migration. A third zone, the transitional zone, showed nonmigrating polygonal ECs containing prominent central and dense peripheral bands (DPB) of MF bundles. The central MF bundles were oriented randomly with respect to the wound edge. The MF bundles of the confluent resting monolayer were both centrally and peripherally located with the latter being more prominent. The results indicate that the reorientation of central MF bundles and reduction in the peripheral MF bundles are probably important in the reorganization of the cytoskeletal system during the conversion of stationary cells to migrating cells.