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 cellproliferation was maximal and half‐maximal in the presence of PL from 3 × 108 and 0.5 × 108 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 × 108 platelets/ml. The presence of PL from 3 × 108 platelets/ml in pre‐confluent bone cellcultures for 48 h resulted in a threefold decrease of alkaline phosphatase (ALP) specificactivity. In the case of confluent bone cells, the presence of PL (from 1 × 106 to 3 × 108 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 × 108 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 adecrease 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. Résumé Bien que les concentrés en plaquettes et le plasma riche en plaquettes ont été utilisés pour promouvoir la guérison osseuse dans la chirurgie maxillo‐faciale et orthopédique, les mécanismes aux niveaux cellulaires sous‐jacents restent peu connus. L'étude in vitro présente a étudié les effets du lysate de plaquettes humaines (PL) sur des fonctions sélectives de cellules osseuses en culture. Des cellules du crâne d'un foetus de rat âgé de18 jours ont été isolées par un processus de digestion par collagénase. PL a été ajoutéà différentes concentrations sur les étapes cellulaires pré‐ et post‐confluentes. Après une journée, la prolifération cellulaire osseuse était respectivement maximale et demi‐maximale en présence de PL de 3 × 108 et 0,5 × 108 plaquettes/ml. Durant 17h le nombre de cellules osseuses traversant la bordure rugueuse d'un modèle de guérison non‐lisse augmentait de 16x en