Allogenic platelet-rich plasma and platelet-rich plasma extracellular vesicles alter the proteome of tenocytes in an in vitro equine model of tendon inflammation: A pilot study

Abstract Background Tendon injuries are common in horses, often resulting in a high risk of reinjury. Hemoderivative therapeutics including platelet-rich plasma (PRP) show promise but outcomes vary due to inconsistent composition. PRP is rich in soluble growth factors and extracellular vesicles (EVs), the latter facilitate cell-to-cell communication by delivering biologically active cargo. This pilot study profiled the proteome of PRP and PRP-derived EVs and examined their effects on an equine tendon inflammatory model in vitro . Methods Plasma was isolated via double centrifugation and PRP produced using a commercial filtration kit. EVs were isolated from PRP and plasma using differential ultracentrifugation and characterised with the Exoview Tetraspanin assay. Equine tenocytes were stimulated with interleukin 1β and tumor necrosis factor α, then treated with PRP or PRP-derived EVs. Proteomic analysis was conducted on cell lysates, PRP and PRP-EVs using data-dependent acquisition liquid chromatography-tandem mass spectrometry and the data analyzed using multivariate and univariate approaches. Results PRP contained 575 quantifiable proteins and PRP-derived EVs 209 proteins. When compared to plasma and plasma derived EVs respectively, PRP and PRP-EVs were enriched in proteins associated with cellular waste disposal and inhibition of lipid metabolism. Experimental factors (inflammatory stimulation and/or treatments) significantly affected the abundance of 18 proteins as expressed in equine tenocytes including col1a1 (col1a1) and sequestosome 1, associated with collagen metabolism and nuclear factor kappa B signaling. Discussion The findings from this study suggest PRP-derived EVs influence inflammatory tenocytes and may be crucial to the efficacy of PRP.