Differential Growth Factor Retention by Platelet-Rich Plasma Composites

Purpose: This study evaluates the temporal sequence and growth factor release from platelet-rich plasma (PRP) combined with different bone substitutes (BS), to identify an optimal substrate for extended growth factor retention.

Materials and Methods: PRP was clotted with bovine thrombin or thrombin receptor activator peptide-6 (TRAP). In addition, PRP was clotted using Allogro (Ceramed, Lakewood, CO), BioGlass (Mo-Sci, Rolla, MN), or BioOss (Osteohealth, Shirley, NY). The effects of media exchange and BS on platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGFbeta) release were quantified via enzyme-linked immunosorbent assay.

Results: At day 1, the thrombin group released 36% more PDGF than the TRAP group and 80% more than the BS groups. At 7 days, PDGF release was the greatest for the TRAP group. PDGF release was minimal for all groups at day 14, with BS groups retaining 60% more PDGF than thrombin clots. Similarly, the thrombin group released the greatest amount of TGFbeta (81.4% of the total), whereas TRAP and BS groups released significantly less TGFbeta at day 1. Compared with thrombin, TRAP retained 39.2% more TGFbeta, whereas BS groups retained even greater levels (Allogro, 54.3%; BioOss, 45.8%; BioGlass, 67.0%). No significant difference in TGFbeta release was observed among the substitutes after day 1. The BS groups continued to retain TGFbeta after 14 days, whereas all TGFbeta in the thrombin clots was depleted.

Conclusions: PRP preparation with thrombin results in a large, immediate release of growth factors that could be lost into the interstitium in vivo. TRAP-BS may prove more efficacious than thrombin in sustaining growth factor levels critical for the cascade of events leading to bone formation.