2013 Neer Award: Effect of the adipose-derived stem cell for the improvement of fatty degeneration and rotator cuff healing in rabbit model

Background: This study was conducted to verify the effects of adipose-derived stem cells (ADSCs) on tendon healing and reversal of fatty infiltration in a chronic rotator cuff tear model by using the rabbit sub-scapularis (SSC). Methods: The SSC insertions in 32 rabbits were cut bilaterally. After 6 weeks, secondary procedures were performed bilaterally, dividing the rabbits into 4 groups of 8 rabbits each as follows: the ADSC+repair group, saline+repair group, ADSC-only group, and saline-only group. A fifth group of 8 rabbits served as normal controls (control group). Electromyographic, biomechanical, and histologic analyses were performed 6 weeks after the secondary procedures. Results: All SSC tendons in the ADSC-only and saline-only groups failed to heal and were excluded from the electromyographic and biomechanical tests. On electromyographic evaluation, the ADSC+repair group exhibited a larger compound muscle action potential area than the saline+repair group (11.86 +/- 2.97 ms . mV vs 9.42 +/- 3.57 ms . mV, P=.029), and this response was almost at the level of the control group (13.17 +/- 6.6 3 ms . mV, P=.456). Biomechanically, the load-to-failure of the ADSC+repair group (87.02 +/- 29.81 N) was higher than that of the saline+repair group (59.85 +/- 37.77 N), although this difference did not reach statistical significance (P=.085). Histologically, the mean proportions of fatty infiltration in the SSC muscles were 29% +/- 15%, 43% +/- 9%, 51% +/- 14%, 63% +/- 10%, and 18% +/- 9% for the ADSC+repair, saline+repair, ADSC-only, saline-only, and control groups, respectively (P<.001). The degree of fat staining increased from the ADSC+repair group (unclear or weak) to the saline-only group (strongly present). Conclusion: Local administration of ADSCs might have the possibility to improve muscle function and tendon healing and decrease fatty infiltration after cuff repair. (C) 2014 Journal of Shoulder and Elbow Surgery Board of Trustees.