Aspirin Does Not Inhibit Platelet-Rich Plasma Releasate Efficacy in a Murine Model of Rotator Cuff Tendinopathy

Platelet-rich plasma (PRP) has been shown to be a promising treatment for subacromial impingement, and although its interaction with aspirin (ASA) is controversial, many providers ask patients to stop non–steroidal anti-inflammatory drug use before PRP administration. This studied aimed to identify the effect of PRP in a murine model of subacromial impingement and to explore the effect of ASA on PRP treatment. A murine model of subacromial impingement was used, incorporating 48 wild-type C57BL/6 mice. After impingement surgery, mice received either human PRP activated via calcium chloride or saline injected into the subacromial space. The mice received either drinking water with ASA or standard drinking water, creating 4 groups: saline injection, saline injection + ASA, PRP injection, and PRP injection + ASA. All injections occurred at 3 weeks after impingement surgery, and mice were evaluated at 6 weeks. Each mouse underwent gait analysis, biomechanical analysis (N = 10 shoulders), histological analysis (N = 6), and gene expression analysis (N = 8). Biomechanical testing showed increased load to failure in the PRP group compared to the ASA group, and increased stiffness in PRP vs saline, PRP vs ASA, and PRP vs ASA + PRP. Gene expression analysis identified 17 downregulated genes between the ASA + PRP and saline groups. Eight of these differentially expressed genes contribute to collagen biosynthesis and modification, 4 to extracellular matrix (ECM) synthesis, and 4 to ECM degradation. In this preliminary analysis, PRP injections in a murine model of subacromial impingement demonstrated mixed effects on tendon quality and pain, and ASA did not have a consistent effect on the response to PRP.