Intratendinous Injection of Mesenchymal Stem Cells for the Treatment of Rotator Cuff Disease: A 2-Year Follow-Up Study

Purpose: To assess the mid-term safety and efficacy of an intratendinous injection of autologous adipose tissue-derived mesenchymal stem cells (AD MSCs) for rotator cuff disease at 2-year follow-up. Methods: The first part of the study consisted of 3 dose-escalation groups, with 3 patients each, for the evaluation of safety: low-dose (1.0 x 10(7) cells), middose (5.0 x 10(7)), and high-dose (1.0 x 10(8)) groups. For the second part, we planned to include 9 patients receiving the high dose for the evaluation of exploratory efficacy. Clinical outcomes were assessed according to pain, range of motion, muscle strength, functional scores, overall satisfaction and function, and presence of failure. Structural outcomes included changes in volume of tendon defects measured using magnetic resonance imaging. Results: This study enrolled 19 patients (9 for the first part and 10 for the second part) with partial-thickness rotator cuff tears. There were no treatment- related adverse events at minimum 2-year follow-up. Intratendinous injection of AD MSCs reduced shoulder pain by approximately 90% at 1 and 2 years in the mid- and high-dose groups. The strength of the supraspinatus, infraspinatus, and teres minor significantly increased by greater than 50% at 2 years in the high-dose group. Shoulder function measured with 6 commonly used scores improved for up to 2 years in all dose groups. Structural outcomes evaluated with magnetic resonance imaging showed that the volume of bursal-sided defects in the high-dose group nearly disappeared at 1 year and did not recur at up to 2 years. No failures-defined as the performance of any kind of shoulder surgery or return of the Shoulder Pain and Disability Index score to the preinjection level-occurred during follow-up. Conclusions: This study showed continued safety and efficacy of an intratendinous injection of AD MS Cs for the treatment of partial-thickness rotator cuff tears over a 2-year period through regeneration of tendon defects.