Polydactyly bone marrow-derived mesenchymal stem cell-conditioned medium can prevent cartilage degeneration and alleviate knee pain in a rat model of osteoarthritis.

Background: Osteoarthritis (OA) is characterized by progressive degeneration of joint cartilage and has substantially increased worldwide. Recently, Mesenchymal stem cells (MSCs) have been explored as a cell-based therapy for the treatment of OA. MSC therapy has not been safely introduced into clinical practice due to immune rejection and the need for highly controlled culture protocols. The therapeutic efficacy of MSC treatment is mediated by the paracrine effect, and conditioned medium (CM) containing MSC-derived secreted factors have potential for useful cell-free therapy. CM can be prepared from various sources, though bone marrow MSCs obtained from infant polydactyly patients may be particularly useful for chondrogenic differentiation and the regulation of cartilage formation. The purpose of this study was to evaluate the effect of polydactyly bone marrow MSC-derived conditioned medium (pBMSC-CM) on the prevention of cartilage degeneration and knee pain using a rat monoiodoacetate (MIA)-induced knee OA model. Methods: pBMSC-CM was isolated from the bone marrow of an infant polydactyly thumb. In vitro, cell proliferation was evaluated in chondrocytes cultured with pBMSC-CM, and gene expression of cartilage matrix markers was assessed by quantitative reverse transcription PCR. RNA sequencing was conducted to analyze differentially expressed genes in pBMSCs. A knee arthritis model was generated by an intra-articular injection of MIA into the right knee of 18 Sprague-Dawley rats, which were then divided into three groups: (1) No-treatment group, (2) Culture medium only group, and (3) pBMSC-CM group. Each group received intra-articular injections of either saline, alpha-Minimal Essential Medium, or pBMSC-CM one week after the MIA injection. To assess knee joint pain, the struggle threshold of the knee joint extension angle was measured every week. Two weeks after treatment injections, a retrograde neurotracer was injected into both knees. After one week, articular cartilage and synovitis were evaluated based on histological characteristics. The dorsal root ganglions (DRG) were immunostained to evaluate the expression of calcitonin gene-related peptide (CGRP). Results: pBMSC-CM enhanced chondrocyte proliferation and upregulated cartilage matrix genes. Chondrogenic and neuroprotective genes were highly expressed in pBMSCs. In behavioral tests, the pBMSC-CM group showed significant improvement in struggle threshold compared to the no-treatment and culture medium only groups. Histological evaluation showed significantly less cartilage degeneration in the pBMSC-CM group than in the other two groups. There were no significant differences in the degree of synovitis among the three groups, although CGRP expression in DRG was lower in the pBMSC-CM group. Conclusion: In this study, pBMSC-CM therapy reduced extracellular matrix degeneration in the articular cartilage and suppressed CGRP expression in the DRG in an MIA-induced rat OA model. Our findings suggest that pBMSC-CM therapy alleviated knee pain not only in the behavioral test but also in CGRP assessment. Overall, this study provides important insights into the potential of pBMSC-CM for the treatment of knee OA and contributes to future clinical trials.