Human Amniotic Membrane Improves Healing In A Chronic, Massive Rotator Cuff Repair Model

Rotator cuff tendon heals by fibrovascular scar that is weaker than native tissue leading to repairs that are prone to failure. To investigate the utility of an amniotic-membrane-derived human allograft in improving tendon-bone healing and skeletal muscle architecture, a rotator cuff repair model in Sprague-Dawley rats was established, tendon biomechanical testing, single muscle fiber biomechanical testing, microcomputed tomography analysis, tendon and muscle histological analysis, and gene expression analysis were performed. Our findings demonstrated single muscle-fibers with larger cross-sectional area and greater maximum isometric and specific force in the augmented experimental repair (ER) group. Additionally, microcomputed tomography revealed a larger volume of newly formed bone and histomorphometric analysis demonstrated significantly greater fibrocartilage area and collagen organization at the healing tendon-bone insertion site in the ER group compared to the control repair (CR) group. Muscle gene expression analysis revealed increased expression of COL1A1 and MMP-2 and decreased expression of FITM-2 in the ER group compared to CR. These findings revealed that augmentation with human amniotic membrane was associated with positive effects on the entire muscle-tendon-bone unit. Based on these findings, we believe that further investigation is warranted to optimize local and spatial delivery of amniotic tissue-based products