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Background: Poor healing of the tendon-bone interface after rotator cuff repair is one of the main causes of surgical failure. Previous studies demonstrated that demineralized cortical bone (DCB) could improve healing of the enthesis. Purpose: To evaluate the outcomes of hierarchically demineralized cortical bone (hDCB) coated with stem cell–derived extracellular matrix (hDCB-ECM) in the repair of the rotator cuff in a rabbit model. Study Design: Controlled laboratory study. Methods: Tendon-derived stem cells (TDSCs) were isolated, cultured, and identified. Then, hDCB was prepared by the graded demineralization procedure. Finally, hDCB-ECM was fabricated via 2-week cell culture and decellularization, and the morphologic features and biochemical compositions of the hDCB-ECM were evaluated. A total of 24 rabbits (48 samples) were randomly divided into 4 groups: control, DCB, hDCB, and hDCB-ECM. All rabbits underwent bilateral detachment of the infraspinatus tendon, and the tendon-bone interface was repaired with or without scaffolds. After surgery, 8 rabbits were assessed by immunofluorescence staining at 2 weeks, and the others were assessed by micro–computed tomography (CT) examination, immunohistochemical staining, histological staining, and biomechanical testing at 12 weeks. Results: TDSCs were identified to have universal stem cell characteristics including cell markers, clonogenicity, and multilineage differentiation. The hDCB-ECM contained 3 components (bone, partial DCB, and DCB coated with ECM) with a gradient of calcium and phosphorus elements, and the ECM had stromal cell-derived factor 1, biglycan, and fibromodulin. Macroscopic observations demonstrated the absence of infection and rupture around the enthesis. The results of immunofluorescence staining showed that hDCB-ECM promoted stromal cell recruitment. Results of micro-CT analysis, immunohistochemical staining, and histological staining showed that hDCB-ECM enhanced bone and fibrocartilage formation at the tendon-bone interface. Biomechanical analysis showed that the hDCB-ECM group had higher ultimate tensile stress and Young modulus than the DCB group. Conclusion: The administration of hDCB-ECM promoted healing of the tendon-bone interface. Clinical Relevance: hDCB-ECM could provide useful information for the design of scaffolds to repair the tendon-bone interface, and further studies are needed to determine its effectiveness.

It is highly desirable to develop a novel scaffold that can induce stem cell migration in tendon tissue engineering and regeneration. The objective of this study is to assess the effect of stem cell extracellular matrix-modified decellularized tendon slices (ECM-DTSs) on bone marrow mesenchymal stem cells (BMSCs) migration and explore the possible molecular mechanisms. Native ECM produced by BMSCs and tendon-derived stem cells (TDSCs) was deposited on DTSs, denoted as bECM-DTSs and tECM-DTSs, respectively, and the migration of BMSCs treated with the extracts from ECM-DTSs was studied. Almost all the seeded stem cells were removed from the stem cell-DTS composites, while ECM produced by stem cells completely covered the surface of the DTSs. Significantly higher levels of chemokines, including stromal cell-derived factor-1 (SDF-1) and monocyte chemotactic protein-1 (MCP-1) were released by ECM-DTSs than by bare DTSs (p < 0.05), according to ELISA, and tECM-DTSs exhibited the highest release within 72 h. bECM-DTSs and tECM-DTSs markedly improved BMSCs migration compared to bare DTSs, with tECM-DTSs yielding the best recruitment effects. The ECM-DTSs led to early cytoskeletal changes compared to bare DTSs (p < 0.05). Migration-related gene and protein expression was significantly upregulated in BMSCs treated with ECM-DTSs via the PI3K/AKT signaling pathway (p < 0.05), indicating that ECM-DTSs could enhance BMSCs migration via the PI3K/AKT signal pathway, and the effect of tECM-DTSs on BMSCs migration is superior to that of bECM-DTSs. This may provide the experimental and theoretical evidence for using stem cell-derived ECMmodified scaffold as a novel approach to recruit stem cells.