Tissue-Engineered Tendon for Enthesis Regeneration in a Rat Rotator Cuff Model.

Healing of rotator cuff (RC) injuries with current suture or augmented scaffold techniques fails to regenerate the enthesis and instead forms a weaker fibrovascular scar that is prone to subsequent failure. Regeneration of the enthesis is the key to improving clinical outcomes for RC injuries. We hypothesized that the utilization of our tissue-engineered tendon to repair either an acute or a chronic full-thickness supraspinatus tear would regenerate a functional enthesis and return the biomechanics of the tendon back to that found in native tissue. Engineered tendons were fabricated from bone marrow-derived mesenchymal stem cells utilizing our well-described fabrication technology. Forty-three rats underwent unilateral detachment of the supraspinatus tendon followed by acute (immediate) or chronic (4 weeks retracted) repair by using either our engineered tendon or a trans-osseous suture technique. Animals were sacrificed at 8 weeks. Biomechanical and histological analyses of the regenerated enthesis and tendon were performed. Statistical analysis was performed by using a one-way analysis of variance with significance set at p < 0.05. Acute repairs using engineered tendon had improved enthesis structure and lower biomechanical failures compared with suture repairs. Chronic repairs with engineered tendon had a more native-like enthesis with increased fibrocartilage formation, reduced scar formation, and lower biomechanical failure compared with suture repair. Thus, the utilization of our tissue-engineered tendon showed improve enthesis regeneration and improved function in chronic RC repairs compared with suture repair. Clinical Significance: Our engineered tendon construct shows promise as a clinically relevant method for repair of RC injuries.