Thrombin stimulates fibroblast chemotaxis and replication.

The serine protease alpha-thrombin, a product of the circulating zymogen prothrombin, plays multiple roles in homeostasis and coagulation. During blood clotting, it is present within fibrin matrices and is likely to be presented to local cell populations. It is known to be a fibroblast mitogen, but its effects on fibroblast recruitment have not been assessed. Here we compared the effect of human alpha-thrombin on chemotaxis and proliferation of human and rat skin fibroblasts and assessed the mechanism of these actions. Fibroblast chemotaxis was assayed using a 48-well Boyden chamber and replication assessed by a spectrophotometric method, based upon the uptake and subsequent elution of methylene blue by fibroblasts. Two fibroblast cell lines were used; fetal rat skin (FR) and newborn human foreskin (HS68). Human alpha-thrombin stimulated FR fibroblast chemotaxis over a wide range of doses (10(-12) M to 10(-7) M). Maximal migration was seen at 10(-10) M; 39 +/- 2.5 cells/high power field (h.p.f.) compared with 19 +/- 3 cells/h.p.f. for media control. In the same assay platelet-derived growth factor, a well characterized fibroblast chemoattractant, caused a maximal stimulation of 44 +/- 5 cells/h.p.f. at a concentration of 3 x 10(-9) M. A similar stimulation was observed with HS68 fibroblasts, although for this cell line maximal chemotaxis (190 +/- 12.5% of control) was seen at 10(-8) M thrombin. Fibroblast replication was optimal at 1.25 x 10(-9) M thrombin (134 +/- 4 and 127 +/- 5% of control for FR and HS68, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)