Effects of platelet lysates on select bone cell functions

Although platelet-rich plasma and platelet concentrates have been used to promote bone healing in orthopaedic and maxillofacial surgery, the underlying cellular-level mechanisms remain poorly understood. The present in vitro study investigated the effects of human platelet lysate (PL) on selected functions of cultured bone cells. Cells from 18-day-old fetal rat calvaria were isolated by a collagenase digestion procedure. PL was added at different concentrations on pre- or post-confluent cell stage. After 1 day, bone cell proliferation was maximal and half-maximal in the presence of PL from 3 x 10(8) and 0.5 x 10(8) platelets/ml, respectively. During 17 h, the number of bone cells traversing the scrape border of a scrape wound model increased by 16-fold in the presence of PL from 3 x 10(8) platelets/ml. The presence of PL from 3 x 10(8) platelets/ml in pre-confluent bone cell cultures for 48 h resulted in a threefold decrease of alkaline phosphatase (ALP) specific activity. In the case of confluent bone cells, the presence of PL (from 1 x 10(6) to 3 x 10(8) platelets/ml) for 11 days, the ALP specific activity and total calcium content decreased in a PL dose-dependent manner and reached a minimum in the presence of PL from 3 x 10(8) platelets/ml. In summary, short-term PL exposure (up to 24 h) promotes the proliferative and chemotactic bone cell functions while long-term PL exposure results in a decrease of both ALP activity and mineral formation. These data show that the soluble components contained in PL may affect the bone healing process by modulating differently bone cell functions.