The effects of platelet releasate on the migration and proliferation of bone marrow-derived cells cultured under osteogenic conditions

Concentrated platelets and their products are currently being used as a clinical tool to accelerate endosseous wound healing. However, there is a lack of understanding regarding the actions of platelets and platelet released products on osteogenic cells. In the current study, we show that releasate from thrombin activated platelets increases the migration and proliferation of osteogenic cultures of bone marrow cells by a dose-dependent mechanism. Using a scratch wound assay, we demonstrated that platelet releasate (PR) stimulated up to a 2.40 +/- 0.50-fold increase in scratch closure in serum-free medium, relative to a control containing thrombin. In the presence of serum, the addition of PR resulted in a 1.45 +/- 0.13-fold increase in scratch closure. To isolate migration from proliferation, cell monolayers were pre-incubated with 5, 10 and 20 mug/ml of Mitomycin C (MMC), which inhibits cell division. This resulted in a large overall decrease in the leading front of scratch closure, which indicated that PR stimulated cell mitogenesis. However, irrespective of MMC pre-treatment, PR stimulated a motogenic response. These results provide a possible mechanism whereby platelets may influence bone regeneration.