Fibulin-7 Promotes Short-term Histological Bone-Tendon Interface Healing in a Murine Rotator Cuff Repair Model.

BACKGROUND: Aging is associated with degenerative changes in both bone and tendon tissues, leading to impaired healing at the bone-tendon interface (BTI) during rotator cuff repair. The role of fibulin-7 (FBLN7) in enhancing BTI healing in aged populations warrants an investigation because of its potential regenerative properties. PURPOSE: To determine whether FBLN7 can enhance tendon-bone healing and regeneration in a model of rotator cuff repair in aging mice. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 5 young (8 weeks old) and 5 aged (18 months old) C57BL/6 mice were used for a baseline supraspinatus tendon-humerus evaluation. Another 20 aged mice underwent rotator cuff repair and were allocated to either the FBLN7 (intervention) group (n = 10), receiving a fibrin sealant with FBLN7, or a control group (n = 10), receiving a standard fibrin sealant. Mice were euthanized at 4 (n = 5 per group) and 8 (n = 5 per group) weeks after surgery. The supraspinatus tendon-humerus complexes were harvested for micro-computed tomography, histological analysis, and biomechanical testing. RESULTS: The expression of FBLN7 was significantly lower in aged mice at the BTI compared with young mice (P < .05). Histological and biomechanical assessments revealed that the FBLN7 group exhibited improved subchondral bone morphology (P < .05) and denser cortical bone (P < .05), along with significantly higher failure loads and stiffness (P < .05), compared with the control group. Additionally, the FBLN7 group demonstrated superior fibrocartilage formation (P < .05) and the upregulated expression of osteogenic (Runx2; P < .01 at week 4 and P < .05 at week 8), chondrogenic (Sox9; P < .01 at week 4 and P < .05 at week 8), and tenogenic (SCX; P < .05 at week 4) factors. CONCLUSION: FBLN7 significantly enhanced healing and regeneration at the BTI in aged mice, supporting its potential as a therapeutic intervention to improve rotator cuff repair outcomes. CLINICAL RELEVANCE: These findings highlight FBLN7's potential role in clinical sports medicine, suggesting that it could be utilized to promote better recovery and healing in aged patients undergoing rotator cuff repair, addressing a critical challenge in postoperative rehabilitation.