Background.Platelet-rich plasma (PRP) has been used as treatment of ligament desmopathy.However, there is scarce in vitro information about the mechanism of action of leukocyte rich and leukocyte poor PRP related products.The aim of this study was to compare the anti-inflammatory, anabolic and anti-catabolic effects of a leukocyte-concentrate platelet-rich gel supernatant (Lc-PRGS) and a leukocyte-reduced PRGS (Lr-PRGS) of ligament explants (LEs) challenged with lipopolysaccharide (LPS).Methods.LEs from 6 horses were cultured for 72 h with Lc-PRGS and Lr-PRGS at concentrations of 25 and 50%, respectively.Hyaluronic acid (HA) was measured by ELISA on culture media of experimental groups at 1 h and 72 h.At 72 h, LEs were used either for quantitative gene expression of nuclear factor kappa B (NFkB), type 1 collagen (COL1A1), cartilage oligomeric matrix protein (COMP), decorin (DCN), transforming growth factor beta 1 (TGF-β1), matrix metalloproteinase 3 (MMP3) and matrix metalloproteinase 13 (MMP13) or for histology analysis.Results.All PRGS produced NFkB down-regulation.25% Lr-PRGS produced up-regulation of COL1A1, DCN and TGF-β1.25% Lc-PRGS induced MMP3 and MMP13 down-regulation in comparison to the rest of hemoderivatives.The general histology score was apparently better in LEs cultured with 25% Lr-PRGS.Conclusions.These findings suggest that 25% Lr-PRGS is more suitable for SL desmopathy and that possibly the up-regulation of extracellular matrix (ECM) ligament anabolic genes is more important to induce SL healing than the down-regulation of ECM ligament catabolic genes.In order to determine the clinical relevance of the results found in this study, is necessary to test the effects of Lc-PRP and Lr-PRP in animal or human models.The use of Lc-PRP and Lr-PRP in desmopathy cases will be an easy-safe-low cost option for treatment.