Composite Patch with Heterogeneous Structural Design for Improved Rotator Cuff Repair

Postoperative re-tear remains a prevalent challenge in rotator cuff repair. To address this, we developed a bioactive glass composite rotator cuff patch (BCP) with heterogeneous structural design to promote tendon-bone interface regeneration. The BCP features an outer barrier of hydrophobic poly (lactic acid) (PLA) electrospun membrane, which prevents infiltration of inflammatory fibrotic tissue. The inner structure, fabricated via a dual-nozzle 3D printing strategy, comprises gelatin methacryloyl (GelMA) hydrogel layers differentially loaded with zinc-doped (ZnBG) or strontium-doped (SrBG) bioactive glass, targeting the tendon and bone regions, respectively. Bioactive glass enables sustained ion release within the physiological environment, establishing distinct ionic microenvironments across the tissue interface. In vitro, ZnBG-released ions significantly promoted the proliferation and migration of tendon-derived stem cells, upregulated mature tendon matrix expression, and inhibited fibrotic scarring. Conversely, SrBG-released ions enhanced the osteogenic differentiation and mineralization potential of bone marrow mesenchymal stem cells. In vivo evaluation further demonstrated that the BCP effectively facilitated organized collagen regeneration and improved the quality of its integration with bone. Additionally, the BCP favorably modulated the local immune microenvironment toward a reparative phenotype. In summary, this study presents an innovative biomaterial strategy for achieving comprehensive structural and functional regeneration of the tendon-bone interface following rotator cuff injury.