Engineered tendon-fibrocartilage-bone composite and bone marrow-derived mesenchymal stem cell sheet augmentation promotes rotator cuff healing in a non-weight-bearing canine model

Reducing rotator cuff failure after repair remains a challenge due to suboptimal tendon-to-bone healing. In this study we report a novel biomaterial with engineered tendon-fibrocartilage-bone composite (TFBC) and bone marrow-derived mesenchymal stem cell sheet (BMSCS); this construct was tested for augmentation of rotator cuff repair using a canine non-weight-bearing (NWB) model. A total of 42 mixed-breed dogs were randomly allocated to 3 groups (n = 14 each). Unilateral infraspinatus tendon underwent suture repair only (control); augmentation with engineered TFBC alone (TFBC), or augmentation with engineered TFBC and BMSCS (TFBC + BMSCS). Histomorphometric analysis and biomechanical testing were performed at 6 weeks after surgery. The TFBC + BMSCS augmented repairs demonstrated superior histological scores, greater new fibrocartilage formation and collagen fiber organization at the tendon-bone interface compared with the controls. The ultimate failure load and ultimate stress were 286.80 +/- 45.02 N and 4.50 +/- 1.11 MPa for TFBC + BMSCS group, 163.20 +/- 61.21 N and 2.60 +/- 0.97 MPa for control group (TFBC + BMSCS vs control, P = 1.12E-04 and 0.003, respectively), 206.10 +/- 60.99 N and 3.20 +/- 1.31 MPa for TFBC group (TFBC + BMSCS vs TFBC, P = 0.009 and 0.045, respectively). In conclusion, application of an engineered TFBC and BMSCS can enhance rotator cuff healing in terms of anatomic structure, collagen organization and biomechanical strength in a canine NWB model. Combined TFBC and BMSCS augmentation is a promising strategy for rotator cuff tears and has a high potential impact on clinical practice.