The effects of adipose-derived stem cell transplantation on tendon-bone healing in a model of chronic rotator cuff tear with suprascapular nerve injury

Abstract Background : Recurrence of massive rotator cuff tears (RCTs) are relatively common due to resultant muscle atrophy and fatty infiltration, possibly caused by scapular nerve (SN) injury. Growing evidence suggests that adipose-derived stem cells (ADSCs) are useful tools for regeneration in chronic RCT models. However, data on the effects of ADSCs on in chronic RCT models with SNI are limited. This study aimed to investigate the effect of ADSCs on tendon-bone healing in a chronic rotator cuff tear (RCT) model with scapular nerve (SN) injury. Methods: Overall, 36 adult rats (weight=344±33 g) were equally divided into the ADSC (+) and ADSC (-) group. Both groups underwent right shoulder surgery in which the supraspinatus was detached, and SN injury was induced; he untreated left shoulder in the ADSC (-) group was used as a control. In the ADSC (+) group, abdominal fat was collected to culture ADSCs. At 6 weeks postoperatively, the ADSC (+) group underwent surgical tendon repair with ADSC injection, whereas the ADSC (-) group underwent tendon repair with saline injection. Shoulders were harvested at 10, 14, and 18 weeks and underwent histological, fluorescent, and biomechanical analyses. Results: In bone-tendon junction, a firm enthesis, including dense mature fibrocartilage and well-aligned cells, was observed in the ADSC (+) group. Conversely, decreased cell density and immature fibrocartilage were observed in the ADSC (-) group. Fatty infiltration was more uncommon in the ADSC (+) group compared to that in the ADSC (-) group. The mean maximum stress and linear stiffness was higher in the ADSC (+) group than in the ADSC (-) group at 18 weeks. Neither the mean Young’s modulus nor the cross-sectional area were significantly different throughout the study. Conclusion: ADSC injection produced better histological and biomechanical outcomes. Thus, ADSC supplementation showed a positive effect on tendon-bone healing in a chronic RCT model with SN injury; therefore, ADSC injection possibly accelerates recovery in large RCT repair.