Regenerative effects of mesenchymal stem cells by dosage in a chronic rotator cuff tendon tear in a rabbit model

Aim: We investigated the therapeutic effects and optimal dose of human umbilical cord blood (UCB)-derived mesenchymal stem cell (MSC) injection in a chronic full-thickness rotator cuff tendon tear. Methods: Rabbits (n = 30) were allocated into three groups (normal saline, G1-Sal; 1 × 10⁶ cells UCB-MSC, G2-Low; 2 × 10⁶ cells UCB-MSC, G3-High). Injections were done into the chronic full-thickness rotator cuff tendon tear 6 weeks after a full-thickness tendon tear of the subscapularis was created. Gross & histologic evaluation and motion analysis was done at pre and 4 weeks post-injection. Results: There were no significant differences in tear size and motion analysis parameters 4 weeks after injection between G2-Low and G3-High. Conclusion: The benefits of UCB-MSCs are not dose-dependent in a rabbit model.