The Effect of Single vs Serial Platelet-Rich Plasma Injection in Osteochondral Lesions Treated with Microfracture: An in Vivo Rabbit Model

CATEGORY: Ankle; Basic Sciences/Biologics INTRODUCTION/PURPOSE: Platelet-rich plasma (PRP) has gained increasing interest as a potential therapeutic augment for decreasing inflammation and enhancing healing after cartilage injury. However, it remains unknown whether osteochondral repair outcomes benefit from multiple PRP injections. We performed this animal study to investigate the effects of serial PRP injections on cartilage repair tissue, subchondral bone remodeling, and joint inflammation. METHODS: Forty-eight adult New Zealand White rabbits were randomly assigned to receive either one (1P), two (2P), or three (3P) PRP injections. Cylindrical full-thickness cartilage defects with subsequent microdrilling were created on the central medial femoral condyle of both knees. PRP injections were provided on the day of surgery and every 2 weeks thereafter until the assigned number of injections was achieved for each group. Rabbits in each group were euthanized at 3, 6, or 12 weeks postoperatively. Cartilage repair tissue was assessed using the International Cartilage Repair Society (ICRS) macroscopic and modified ICRS histological scoring systems. Subchondral bone remodeling was evaluated by micro-computer tomography (µCT) analysis. Joint inflammatory cytokines including IL-1, IL-1ra, IL-6, IL-8, TNFα, and TGFβ were assessed by quantitative polymerase chain reaction. RESULTS: Macroscopic assessment at 3 and 6 weeks demonstrated improved mean ICRS macroscopic scores in the PRP groups compared with the control group, although this difference was not significant. The mean ICRS macroscopic score at 12 weeks in Group 3P was significantly lower than the control, but there was no significant difference compared with Group 1P and Group 2P (Control: 6.1+-3.3, Group 1P: 3.4+-2.7, Group 2P: 4.2+-2.9, Group 3P: 0.7+-1.5). The mean modified ICRS histological score was significantly higher at each time point for the PRP groups compared with the control group, but there was no significant difference in the scores among PRP groups. There were no significant differences in outcomes for the characteristics evaluated by µCT nor inflammatory cytokine levels among each group at each time point. CONCLUSION: Serial PRP injections, as compared to a single PRP injection, do not have a significant impact on cartilage repair tissue nor inflammatory cytokine levels at 12 weeks after surgery in an in vivo animal model. Further work is necessary to determine the effect of single versus serial PRP injections on cartilage repair tissue in humans.