Biomechanical, Histologic, and Molecular Evaluation of Tendon Healing in a New Murine Model of Rotator Cuff Repair

Purpose: To develop a clinically relevant, robust murine model of rotator cuff tendon repair to examine cellular and molecular mechanisms of healing. Methods: Sixty C57BL/6 male mice underwent rotator cuff transection and repair using microsurgical techniques. A modified Kessler suturing technique was used prior to tendon detachment. Sutures were passed through 2 intersecting bone tunnels that were made at the tendon attachment site. Mice were sacrificed at 2 and 4 weeks with subsequent biomechanical, histologic, micro-CT, and gene expression evaluations. Results: Failure forces in the 2- and 4-week groups were 36% and 75% of the intact tendon, respectively. Histologic evaluation revealed complete reattachment of the tendon with no observable gap. Healing occurred by formation of fibrovascular tissue at the tendon-bone interface, similar to larger animal models. Molecular analysis revealed gene expression consistent with gradual healing of the reattached tendon over a period of 4 weeks. Comparisons were made using 1-way analysis of variance. Conclusions: This model is distinguished by use of microsurgical suturing techniques, which provides a robust, reproducible, and economic animal model to study various aspects of rotator cuff pathology. Clinical Relevance: Improvement of clinical outcomes of rotator cuff pathology requires in-depth understanding of the underlying cellular and molecular mechanisms of healing. This study presents a robust murine model of supraspinatus repair to serve as a standard research tool for basic and translational investigations into signaling pathways, gene expression, and the effect of biologic augmentation approaches.