Adenoviral-mediated gene transfer of human bone morphogenetic protein-13 does not improve rotator cuff healing in a rat model

Background: Rotator cuff tendon-to-bone healing occurs by formation of a scar tissue interface after repair, which makes it prone to failure. Bone morphogenetic protein-13 (BMP-13) has been implicated in tendon and cartilage repair, and thus may augment rotator cuff repairs. The purpose of this study was to determine if the application of mesenchymal stem cells (MSCs) transduced with BMP-13 could improve regeneration of the tendon-bone insertion site in a rat rotator cuff repair model. Hypothesis: Mesenchymal stem cells genetically modified to overexpress BMP-13 will improve rotator cuff healing based on histologic and biomechanical outcomes. Study Design: Controlled laboratory study. Methods: Sixty Lewis rats underwent unilateral detachment and repair of the supraspinatus tendon and 10 rats were used for MSC harvest. Animals were randomized into 2 groups (30 animals/group). The experimental group received 10⁶ MSCs transduced with adenoviral-mediated gene transfer of human BMP-13 (Ad-BMP-13). The second group received untransduced MSCs. Fifteen animals in each group were sacrificed at 2 and 4 weeks. At each time point, 12 animals were allocated for biomechanical testing, and 3 for histomorphometric analysis. Results: There were no differences in the amount of new cartilage formation or collagen fiber organization between groups at either time point. There were also no differences in the biomechanical strength of the repairs, the cross-sectional area, peak stress at failure, or stiffness. Conclusion: Application of MSCs genetically modified to overexpress BMP-13 did not improve healing in a rat model of rotator cuff repair. Clinical Relevance: Further studies are needed to evaluate various growth factors and combinations of growth factors to determine the optimal factor for the biologic augmentation of rotator cuff repairs.