Support and stimulation of epidermal cell outgrowth from porcine skin explants by platelet factors

The effect of a platelet homogenate fraction (PHF) on epidermal cell outgrowth from porcine skin explants was examined in culture medium with and without 5% foetal bovine serum (FBS). Explants were sustained and outgrowth was initiated, supported and stimulated by PHF, in the absence of FBS. PHF-supported outgrowth was concentration-dependent up to 130 micrograms protein/ml. PHF activity was not removed by heat treatment at 100 degrees C for 2 min but was destroyed by heating at 100 degrees C for 5 min. The factor responsible for epidermal cell outgrowth in PHF may be epibolin or serum spreading factor, or may be a platelet-derived factor as yet undescribed. Viability and outgrowth were stimulated by the 'high molecular weight' fraction of PHF (greater than 30 kd). PHF plus 5% FBS gave inhibition of outgrowth, which was not PHF concentration-dependent; however, this inhibitory effect was variable with different PHF preparations. This study is the first to demonstrate an effect of platelet-derived factors on epidermal cell viability and outgrowth.