Effects of bone morphogenetic protein-7 and low-molecular-weight peptide solution on healing in a rotator cuff tear model: a histopathologic and biomechanical study in rats

Rotator cuff tears are the most prevalent shoulder pathology requiring surgery, yet high retear rates necessitate additional biological adjuncts. This study evaluated the effects of bone morphogenetic protein-7 (BMP-7) and low-molecular-weight peptide solution (LMWPS) on early tendon-to-bone healing. We hypothesized that these 2 agents with different mechanisms of action would histopathologically and biomechanically enhance early rotator cuff repair. Acute rotator cuff repairs were performed bilaterally on 24 Wistar albino rats divided into 3 groups: control, LMWPS (5 &#x3bc;L at 1 &#x3bc;g/&#x3bc;L), and BMP-7 (200 &#x3bc;L at 2.5 ng/&#x3bc;L) groups. At 4 weeks postoperation, the right shoulders underwent biomechanical testing (maximum load, maximum stress, stiffness, and Young modulus), whereas the left shoulders were evaluated histopathologically using the Tendon Healing Scoring System. The BMP-7 group achieved significantly superior biomechanical and histopathologic outcomes compared with the LMWPS and control groups. Biomechanically, stiffness and Young modulus were significantly higher in the BMP-7 group than in the LMWPS group (P = .013 vs. P = .011). Histopathologically, both LMWPS and BMP-7 treatment resulted in a significantly higher tenocyte-like cell ratio (P = .008 vs. P < .001) and more organized parallel fiber alignment (P < .001) than in the control group. Although the LMWPS group showed significantly increased vascularity compared with the control and the BMP-7 groups (P = .006 vs. P = .008), it demonstrated the lowest stiffness among the groups (P = .022 vs. P = .013). BMP-7 application significantly enhances the quality of tendon-to-bone healing by promoting structural maturation and functional stability. Although LMWPS increases biological activity, it does not achieve the mechanical maturity provided by BMP-7 at 4 weeks.