Osteoarthritis is the most common human and animal joint diseases encountered world-wide. General strategies for restoration of the damaged joint surfaces are (1) enhancement of the intrinsic healing capacity of cartilage, (2) replacement of the damaged cartilage, and (3) regeneration of the articular cartilage surface. Animal models are widely used to develop and evaluate the reconstruction of articular cartilage. Due to the similarities in size, load, and type of injuries of joints, horse is the most appropriate animal for modeling joint diseases of humans. As the first step in regenerative strategy is isolation and characterization of competent stem cells, bone marrow was aspirated from 3 mares. Samples were mixed with culture medium and were centrifuged using high density liquid. Mononuclear cells in buffy coat were collected, washed and cultured. After 3 passages (P3), putative mesenchymal stem cells (MSCs) were analyzed for morphological, gene expression, differentiation and growth characteristics. The cells were slender and spindle-shaped, and expressed common surface markers for MSCs including CD29, CD44, CD 90, and MHC-I, but not CD34 (a hematopoietic stem cell marker) and MHC-II. P3 cells differentiated into adipocytes, chondrocytes and osteocytes when they were cultured in appropriate differentiation medium. Also, the isolated cells were able to form colonies. Based on these results, we succeed to isolate and characterize horse MSCs from bone marrow. According to the chondrogenic differentiation potential of these cells, they can be used in regenerative medicine for treatment of joint injuries in horse, as the best animal model for human joint diseases.

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