Application of a Demineralized Cortical Bone Matrix and Bone Marrow–Derived Mesenchymal Stem Cells in a Model of Chronic Rotator Cuff Degeneration

The success of rotator cuff repair is primarily dependent on tendon-bone healing. Failure is common because weak scar tissue replaces the native enthesis, rendering it prone to reruptures. A demineralized bone matrix (DBM) consists of a network of collagen fibers that provide a sustained release of growth factors such as bone morphogenetic proteins. Previous studies have demonstrated that it can regenerate a fibrocartilaginous enthesis. The use of a DBM and mesenchymal stem cells (MSCs) at the healing enthesis will result in a higher bone mineral density at the tendon insertion and will enhance the regeneration of a morphologically superior enthesis when compared with an acellular human dermal matrix. Controlled laboratory study. Eighteen female Wistar rats underwent unilateral detachment of the supraspinatus tendon. Three weeks later, tendon repair was carried out in animals randomized into 3 groups: group 1 received augmentation of the repair with a cortical allogenic DBM (n = 6); group 2 received augmentation with a nonmeshed, ultrathick, acellular human dermal matrix (n = 6); and group 3 underwent tendon-bone repair without a scaffold (n = 6). All animals received 1 × 106 MSCs delivered in fibrin glue to the repair site. Specimens were retrieved at 6 weeks postoperatively for histological analysis and the evaluation of bone mineral density. All groups demonstrated closure of the tendon-bone gap with a fibrocartilaginous enthesis. Although there were no significant differences in the enthesis maturation and modified Movin scores, repair augmented with a dermal matrix + MSCs exhibited a disorganized enthesis, abnormal collagen fiber arrangement, and greater cellularity compared with other MSC groups. Only repairs augmented with a DBM + MSCs reached a bone mineral density not significantly lower than nonoperated controls. A DBM enhanced with MSCs can augment rotator cuff healing at 6 weeks and restore bone mineral density at the enthesis to its preinjury levels. Biological augmentation of rotator cuff repair with a DBM and MSCs may reduce the incidence of retears, although further studies are required to determine its effectiveness