A Synthetic Graft With Multilayered Co-Electrospinning Nanoscaffolds for Bridging Massive Rotator Cuff Tear in a Rat Model

Abstract

Background: Graft bridging is used in massive rotator cuff tear (MRCT); however, the integration of graft-tendon and graft-bone is still a challenge. Hypothesis: A co-electrospinning nanoscaffold of polycaprolactone (PCL) with an “enthesis-mimicking” (EM) structure could bridge MRCT, facilitate tendon regeneration, and improve graft-bone healing. Study Design: Controlled laboratory study. Methods: First, we analyzed the cytocompatibility of the electrospinning nanoscaffolds, including aligned PCL (aPCL), nonaligned PCL (nPCL), aPCL–collagen I, nPCL–collagen II, and nPCL-nanohydroxyapatite (nHA). Second, for the EM condition, nPCL–collagen II and nPCL-nHA were electrospun layer by layer at one end of the aPCL–collagen I; for the control condition, the nPCL was electrospun on the aPCL. In 40 mature male rats, resection of both the supraspinatus and infraspinatus tendons was performed to create MRCT, and the animals were divided randomly into EM and control groups. In both groups, one end of the layered structure was fixed on the footprint of the rotator cuff, whereas the other end of the layered structure was sutured with the tendon stump. The animals were euthanized for harvesting of tissues for histologic and biomechanical analysis at 4 weeks or 8 weeks postoperatively. Results: All scaffolds showed good cytocompatibility in vitro. The graft-tendon tissue in the EM group had more regularly arranged cells, denser tissue, a significantly higher tendon maturing score, and more birefringence compared with the control group at 8 weeks after operation. Newly formed fibrocartilage could be observed at the graft-bone interface in both groups by 8 weeks, but the EM group had a higher graft-bone healing score and significantly more newly formed fibrocartilage than the control group. An enthesis-like structure with transitional layers was observed in the EM group at 8 weeks. Biomechanically, the values for maximum failure load and stiffness of the tendon-graft-bone complex were significantly higher in the EM group than in the control group at 8 weeks. Conclusion: The co-electrospinning nanoscaffold of aPCL–collagen I could be used as a bridging graft to improve early graft-tendon healing for MRCT in a rat model and enhance early enthesis reconstruction in combination with a multilayered structure of nPCL–collagen II and nPCL-nHA. Clinical Relevance: We constructed a graft to bridge MRCT, enhance graft-tendon healing and graft-bone healing, and reconstruct the enthesis structure.