Clinical signs synovial fluid cytology and growth factor concentrations after intra-articular use of a platelet-rich product in horses with osteoarthritis

Abstract

Background: Osteoarthritis (OA) is a common cause of lameness in equines, resulting in poor performance. Platelet-rich plasma (PRP) can deliver a collection of bioactive molecules that play important roles in conditions such as OA. Objectives: To (1) investigate the clinical and synovial changes, (2) determine serum amyloid A (SAA) and total protein (TP) concentrations on serum and synovial fluid, and (3) determine synovial fluid platelet-derived growth factor-BB (PDGF-BB) and transforming growth factor-B1 (TGF-b1) in normal and osteoarthritic joints after intra-articular injection with a platelet-rich product (PRPr). Study design: Experimental. Methods: Horses (n = 5) with naturally occurring OA, affecting either antebrachiocarpal, middle carpal or metacarpophalangeal joints, and normal horses (n = 5). A PRPr was prepared from all horses using a gravity filtration system. Clinical evaluation, synovial fluid analysis, and determination of serum and synovial SAA and TP concentrations were performed on day 0 (prior to PRPr treatment), day 1, day 2, day 5, day 21 and day 56 posttreatment. Synovial fluid growth factor concentrations (PDGF-BB and TGF-β1) were determined on day 1 and day 5. PRPr composition was also analysed. Results: The gravity filtration system produced a moderately concentrated PRPr. The synovial effusion score was statistically significant between the control and OA group on day 0 (p < 0.05) with a higher score in the OA group. However, within the control group the synovial effusion score was significantly elevated on day 1 and 2 compared to day 0 (p < 0.05). For both groups the synovial fluid nucleated cell count, predominantly intact neutrophils, were significantly increased on day 1 and day 2 (p < 0.001 for both), with no significant difference between groups. The mean PDGF-BB and TGF-β1 concentrations were high for both groups but significantly lower in the OA group (p < 0.01 and p < 0.001, respectively) on day 1 compared to normal joints. Concentrations for PDGF-BB remained similar on day 5, compared to day 1, with no significant difference between groups. Conclusions: Intra-articular treatment with PRPr resulted in a transient synovial inflammatory reaction of short duration. Synovial fluid growth factor concentrations were elevated after intra-articular injection of PRPr in OA joints.