Enhancement of tendon-bone healing following rotator cuff repair using hydroxyapatite with TGFβ1

The formation of fibrocartilage at the healing site following a rotator cuff tear repair is a major problem in the field of tendon-bone healing. The present study aimed to enhance the healing of the tendon-bone interface following rotator-cuff tear repair by the interposition of hydroxyapatite (HA) encapsulated with transforming growth factor β1 (TGFβ1). Using an acute rotator cuff repair model, rats were divided into three groups: i) Repair only (control); ii) HA group; and iii) HA-TGFβ1 group. Animals were sacrificed at 2, 4 and 8 weeks following surgery. Micro-computed tomography (CT), histomorphometric analyses and biomechanical tests were used to evaluate the supraspinatus tendon-bone complex. The micro-CT images revealed notable novel bone formation in the groups treated with HA-TGFβ1. The histomorphometric analyses demonstrated improved fibrocartilage formation and collagen organization at the tendon-bone interface. The HA-TGFβ1 combination significantly improved the area of fibrocartilage, particularly at early time points (2 and 4 weeks). There was a significantly greater load-to-failure force achieved in the HA and HA-TGFβ1 groups compared with the control group at 4 and 8 weeks. Augmentation of the ceramic powder with HA-TGFβ1 at the tendon-bone interface was demonstrated to strengthen the healing entheses, increase bone and fibrocartilage formation and improve collagen organization compared with surgical repair alone. Local application of HA-TGFβ1 demonstrates potential in improving tendon-bone healing following rotator cuff repair.