Platelet-dependent serum factor that stimulates the proliferation of epidermal cells in vitro.

Agglutinated platelets are known to release a factor that stimulates the growth of arterial smooth muscle cells or dermal fibroblasts. The present study was designed to see the effect of this platelet factor on epidermal cells. The growth of cultured epidermal cells and dermal fibroblasts obtained from guinea pig ear skin was observed using 10% platelet-rich serum or platelet-poor serum in the culture medium. These sera were prepared from fresh human blood according to the method described by Ross. The cell growth was checked by counting the number of cells in culture or by the uptake of labeled thymidine by the cells. The platelet-rich serum significantly stimulated the growth of epidermal cells as well as fibroblasts as compared with the platelet-poor serum. This implies that platelet factor released after injury to cutaneous vessels in trauma or inflammation plays an important role in initiating proliferation of epidermal cells and dermal fibroblasts.