PLATELET RICH PLASMA ACTIVATION IN COLLAGEN/GLYCOSAMINOGLYCAN OSTEOCHONDRAL SCAFFOLDS FOR ARTICULAR CARTILAGE TISSUE ENGINEERING APPLICATIONS

Abstract

Introduction: Platelet rich plasma (PRP) has been hypothesised to be of potential benefit to articular cartilage tissue engineering, through its release of autologous growth factors. The aim of this study was to ascertain whether the addition of thrombin is required to achieve platelet activation and sustained growth factor release in-vitro, when PRP is applied to a collagen based osteochondral scaffold.

Methods: Collagen/glycosaminoglycan scaffolds were fashioned, to which equal combined volumes of test substances were added (n=3): 500μl PRP; 375μl PRP + 125μl autologous thrombin (3:1); 455μl PRP + 45μl bovine thrombin (10:1). One ml of DMEM/F12 medium was added to each scaffold and changed completely at 12/24 hours, and 3/10 days, following which release of TGF-β1, PDGF-AB and bFGF were measured using ELISA. Secondly, equal sized collagen/glycosaminogly-can and polylactide co-glycolide scaffolds were fashioned to which 500μl of PRP were added (n=3). Similar conditions were followed as previously except that only PDGF-AB was assayed.

Results: A similar cumulative release profile of all growth factors was found over the 10 day period. An increase in growth factor release was seen in the PRP only group at all time points with PDGF-AB in particular reaching statistical significance at all time points (p< 0.006). These findings remained apparent when a correction for volume was made (p< 0.028) suggesting a particular role of the collagen in platelet activation. This was shown in the second experiment, in which a significantly increased cumulative volume of PDGF-AB was released from the collagen/glycosaminoglycan scaffold without thrombin activation (p< 0.04).

Discussion: This study shows that collagen is a potent activator of platelets, requiring no further additive to achieve satisfactory growth factor release when applied clinically. These results suggest that if PRP is combined with polymer scaffolds, it should be activated with thrombin to achieve optimum growth factor release.