Osteoarthritis (OA) is mostly incurable and non-regenerative with long-term complications. Autologous conditioned serum (ACS), which is enriched in Interleukin 1 receptor antagonists (IL-1RA) and growth factors, could be an alternative treatment to accelerate the positive therapeutic effects. ACS is proposed to alleviate inflammation by blocking IL-1 receptors. However, to date, there is no report focusing on the cell-mediated anti-inflammation and regenerative effect caused by ACS, especially the ACS from patients. Therefore, this study aims to investigate the therapeutic potential of ACS generated from dogs with spontaneous OA, focusing on its promising anti-inflammatory and regenerative properties in vitro compared to the matched plasma. We found that ACS prepared from ten OA dogs contained significant concentrations of IL-1RA, vascular endothelial growth factor, and transforming growth factor beta, which are key cytokines in anti-inflammation and angiogenesis. Furthermore, we found that ACS suppressed T cell activity by reducing proliferation of effector T cells and simultaneously expanding numbers of immune suppressive FOXP3⁺ T cells. Lastly, we showed that ACS enhanced the proliferation of osteocytes and fibroblasts and promoted extracellular matrix gene expression in primary chondrocyte culture. Therefore, these studies indicate that ACS prepared from dogs with OA is active as an immunomodulatory and regenerative strategy for use in OA management.

Autologous conditioned serum (ACS) contains anti-inflammatory mediators, whereas cannabidiol (CBD) may have analgesic and immunomodulatory effects. This exploratory randomized trial evaluated intra-articular ACS, alone or combined with oral CBD, after tibial plateau leveling osteotomy in dogs. Twenty-seven dogs were randomized to placebo, ACS, or ACS + CBD (n = 9/group). Outcomes included C-reactive protein (CRP), peak vertical force, orthopedic assessment scores (lameness, joint mobility, pain on palpation, weight-bearing, and overall clinical condition), Canine Brief Pain Inventory, radiographic outcomes, and safety. CRP peaked on Day 1. In the linear mixed model using a heterogeneous first-order autoregressive covariance structure, treatment-group (p = 0.001) and visit (p < 0.001) effects were significant, whereas the treatment-group × visit interaction did not reach significance (p = 0.053). Exploratory comparisons showed lower CRP in ACS + CBD than placebo on Days 3 (adjusted p = 0.007) and 5 (adjusted p = 0.001), with model-dependent sensitivity findings. No consistent treatment-group differences were identified in clinical or structural outcomes. One ACS-treated dog developed a surgical site infection, and alkaline phosphatase activity was higher in ACS + CBD on Day 28. The CRP findings remain hypothesis-generating, with uncertain clinical relevance.