Mesenchymal stem cell therapy is a novel regenerative approach for treating tendinopathy. Here, we evaluated the safety and efficacy of allogeneic adipose-derived mesenchymal stem cells (allo-ASC) in treating lateral epicondylosis (LE). Under ultrasound guidance, allo-ASCs mixed with fibrin glue were injected into the hypoechoic common extensor tendon lesions of 12 participants with chronic LE; 6 subjects each were administered 10 6 or 10 7 cells in 1 ml. Safety was evaluated at day 3 and weeks 2, 6, 12, 26, and 52 post-injection. Efficacy was assessed by measuring patients' visual analog scale (VAS) score for elbow pain, modified Mayo clinic performance index for the elbow, and by evaluating longitudinal and transverse ultrasound images of tendon defect areas after 6, 12, 26, and 52 weeks. No significant adverse effects of allo-ASC injection were observed through 52 weeks of follow-up. From baseline through 52 weeks of periodic follow-up, VAS scores progressively decreased from 66.8 6 14.5 mm to 14.8 6 13.1 mm and elbow performance scores improved from 64.0 6 13.5 to 90.6 6 5.8. Tendon defects also significantly decreased through this period. Allo-ASC therapy was thus safe and effective in improving elbow pain, performance, and structural defects for 52 weeks. This clinical study is the first to reveal therapeutic value of mesenchymal stem cell injection for treating chronic tendinopathy. STEM CELLS 2015;33:2995-3005 SIGNIFICANCE STATEMENTClinical use of mesenchymal stem cells in the treatment of tendinopathy has not been well studied because it may be related to the invasive procedures required to obtain autologous stem cells. Allogeneic stem cells may be an optimal treatment option for tendinopathy, if safety and efficacy can be conclusively demonstrated. Here, we evaluated the safety and efficacy of allogeneic adipose-derived mesenchymal stem cells in treating chronic lateral epicondylosis of 12 participants. No significant adverse effects of allogeneic stem cells were observed through 52 weeks of follow-up. Elbow pain, performance scores, and tendon defects area measured by ultrasound improved through this period. This clinical study is the first to reveal therapeutic value of mesenchymal stem cell injection for treating chronic tendinopathy.

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