Encapsulated Allogeneic Synovial Membrane Mesenchymal Stem Cells Provide Better Outcomes of Chondral Lesions in Horses

Abstract: Osteoarthritis is the main cause of equine lameness, and its treatment remains ineffective. Synovial membrane mesenchymal stem cells (_SMMSCs) provide satisfactory outcomes in joint injuries, mainly due to their immunomodulatory and reparative properties. This study aimed to evaluate the effect of _SMMSCs, either encapsulated in alginate hydrogel or free, in chondral lesions of horses.Methods: Chondral lesions were surgically induced in the medial trochlea of the talus of fifteen horses. Animals were treated with PBS free _SMMSCs or encapsulated _SMMSCs. Physical evaluations, assignment of lameness scores and synovial fluid analysis were performed (cytological analysis and dosage of IL-1, IL-10, IL-6, INF-Ɣ, TNF ????, P substance, serum amyloid A, TGF-β, IGF and PGE2) for two weeks. Cartilage biopsies were performed 150 days after induction for histological analysis and immunohistochemistry staining.Results: All groups initially presented inflammation. Although free _SMMSCs showed moderate tissue repair, encapsulated _SMMSCs had a lower grade of inflammation with superior tissue macro- and microscopic aspects at the end, while the control group showed fibrosis and poor cartilage aspect. This study suggests better effectiveness of stem cells in chondral defects when encapsulated MSCs are used.Conclusion: While the absence of treatment perpetuates cartilage degradation, encapsulated _SMMSCs respond better to initial inflammation, interacting and modulating the environment through the release of anti-inflammatory cytokines. Better outcomes observed in encapsulated MSCs were related to the immuno- and physical barriers provided by the alginate hydrogel, allowing a longer period of permanence and interaction between MSCs and the environment.