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.

Fibrin sealants and platelet preparations in bone and periodontal healing.

Fibrin sealants and platelet concentrates have been used alone or in association with bone substitutes to promote bone healing in orthopedic and oral surgery. Commercial fibrin sealants are homologous plasma-derived products that mimic the last step of a coagulation cascade, leading to a fibrin clot. They are used for topical hemostasis and tissue sealing and as melting agents for particulate bone substitutes. Infectious risk led to the development of autologous fibrin sealants from the patient's own plasma. However, their fabrication results in less reproducible or less satisfactory rheologic properties. The use of autologous products with high platelet concentrations, such as platelet-rich plasma, platelet concentrate, and platelet gels, has recently been suggested for combining the fibrin sealant properties with the growth factor effects of platelets. We describe the characteristics and limitations of fibrin sealants (commercial/autologous) and platelet preparations and review their effects on bone and periodontal healing as reported in experimental studies and clinical trials.