The systemic effects of platelet-rich plasma injection

Platelet-rich plasma (PRP) is an autologous blood product used to treat acute and chronic tendon, ligament, and muscle injuries in over 86,000 athletes in the United States annually. The World Anti-Doping Agency (WADA) banned intramuscular PRP injections in competitive athletes in 2010 because of concerns that it may increase performance-enhancing growth factors. The ban on PRP was removed in 2011 because of limited evidence for a systemic ergogenic effect of PRP, but the growth factors within PRP remain prohibited.

To quantify the effect of PRP injection on systemic growth factors with performance-enhancing effects and to identify molecular markers to detect treated athletes.

Descriptive laboratory study.

Six ergogenic growth factors monitored by WADA-human growth hormone (hGH), insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), basic fibroblast growth factor (bFGF or FGF-2), vascular endothelial growth factor (VEGF), and platelet-derived growth factor-BB (PDGF-BB)-were measured in 25 patients before (baseline) and at 0.25, 3, 24, 48, 72, and 96 hours after intratendinous leukocyte-rich PRP injection. Eating and exercise were prohibited for 3 hours before testing. Growth factors were quantified by enzyme-linked immunosorbent assay, and the change relative to each patient's baseline was calculated.

Relative to serum, PRP contained significantly more bFGF (226 vs 5 pg/mL), VEGF (1426 vs 236 pg/mL), and PDGF-BB (26,285 vs 392 pg/mL), but IGF-1 and hGH were not elevated. Serum levels increased significantly for IGF-1 at 24 and 48 hours, for bFGF at 72 and 96 hours, and for VEGF at 3, 24, 48, 72, and 96 hours after PRP injection. Additionally, VEGF was increased in all 25 patients after PRP treatment.

Serum IGF-1, VEGF, and bFGF levels are significantly elevated after PRP injection, supporting a possible ergogenic effect of PRP. An indirect marker for hGH doping, the product of IGFBP-3 × IGF-1, also significantly increased after PRP. Platelet-rich plasma appears to trigger an increase in circulating growth factors through activating biological pathways rather than by serving as a vehicle for the direct delivery of presynthesized growth factors. Elevated VEGF was observed in all patients after PRP, and ≥88% of patients had elevated VEGF at each time point from 3 to 96 hours after PRP, suggesting that VEGF may be a sensitive molecular marker to detect athletes recently treated with PRP.

This is the first and only adequately powered study of the systemic effects of PRP. We present evidence that PRP contains and may trigger systemic increases in substances currently banned in competitive athletes. Finally, we provide evidence that VEGF could serve as a useful molecular marker to detect athletes treated with PRP.