Basic Fibroblast Growth Factor Is a Signal for the Initiation of Centrosome Redistribution to the Front of Migrating Endothelial Cells at the Edge of an In Vitro Wound

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Abstract
Abstract Rapid, efficient repair of the endothelium following focal endothelial wounding and denudation is regulated by a complex series of cellular processes. Directed cell migration, an early essential event in repair, is thought to be initiated by centrosome redistribution toward the front of the cell prior to the onset of migration. As such, centrosomal polarity may be an important regulatory event in directed endothelial cell migration. Little is known about the regulation of this process. To study this further, in vitro wounds were created down the middle of confluent porcine aortic endothelial monolayers by mechanical denudation. Conditioned media collected 1 hour after wounding contained basic fibroblast growth factor (bFGF). Antibodies directed against bFGF added to the cultures at the time of wounding significantly inhibited cell migration and transiently inhibited centrosome redistribution. When transcription was transiently inhibited with actinomycin D, present at 1 hour before and for 1 hour after wounding, the cells moved more slowly (5.2±2.8 versus 22.7±5.7 μm/h for control), taking five times longer for the wound to close. Throughout this period, centrosomes did not reorient to the front of the cells. When either recombinant bFGF or conditioned medium collected from control cultures at 1 hour after wounding was added 23 hours after actinomycin D was washed out (at which time RNA synthesis returned to control levels), the centrosomes redistributed to the front of the cells, and cells migrated at a rapid rate (17.2±4.2 μm/h), similar to control. However, the recombinant bFGF or conditioned media had no effect when added immediately after actinomycin D was removed, ie, when RNA synthesis was still inhibited. Thus, bFGF initiates centrosome redistribution by stimulating processes that lead to the transcription of as yet unknown essential gene(s) that are induced immediately following wounding, and this appears to be at least one mechanism by which bFGF enhances aortic endothelial migration and repair at the site of an endothelial wound.