Mechanical Stimulation of Equine Bone Marrow Mesenchymal Stromal Cell-Derived Cartilage-Like In Vitro Model Triggers Osteoarthritis Features

Osteoarthritis (OA) affects millions of people globally, causing irreversible cartilage damage, chronic inflammation, and progressive joint dysfunction. Similarly, horses can develop OA spontaneously or due to their athletic careers, influenced by mechanical and biochemical factors. Current treatments primarily focus on symptom relief without promoting cartilage regeneration. In line with the 3Rs principles (refine, reduce, replace), the development of <i>in vitro</i> OA models is essential for advancing new therapeutic approaches against OA. In response to this need, the present study aimed to develop an <i>in vitro</i> model of mechanically induced OA. Bone marrow-derived mesenchymal stromal cells (BM-MSCs) were cultured in a biomaterial scaffold and differentiated for 21 days using a chondrogenic medium to produce cartilage-like <i>in vitro</i> models. The cartilage-like <i>in vitro</i> models underwent mechanical stimulation (compression) for 3 and 7 days at pressures sufficient to induce injurious stress. BM-MSC-derived chondrocytes express the transient receptor potential vanilloid-type 4 (TRPV4) channel and are responsive to mechanical stimulation. Mechanical stimulation was found to reduce cell proliferation without inducing cell death. The overall protein levels of type II collagen drastically declined after both 3 and 7 days of mechanical stimulation. Additionally, glycosaminoglycan (GAG) content within the cartilage-like <i>in vitro</i> models decreased, whereas GAG release into the supernatant increased following mechanical stimulation. Ultimately, compression led to the upregulation of catabolic factors and inflammatory mediators. In conclusion, this model successfully replicates several key features of OA, making it a valuable tool for investigating the disease's mechanisms and testing new therapeutic strategies.