In situ tissue engineering of the tendon-to-bone interface by endogenous stem/progenitor cells.

The long-term success of surgical repair of rotator cuff tears is largely dependent on restoration of a functional tendon-to-bone interface. We implemented micro-precise spatiotemporal delivery of growth factors in three-dimensional printed scaffolds for integrative regeneration of a fibrocartilaginous tendon-to-bone interface. Sustained and spatially controlled release of tenogenic, chondrogenic and osteogenic growth factors was achieved using microsphere-based delivery carriers embedded in thin membrane-like scaffolds. In vitro, the scaffolds embedded with spatiotemporal delivery of growth factors successfully guided regional differentiation of mesenchymal progenitor cells, forming multiphase tissues with tendon-like, cartilage-like and bone-like regions. In vivo, when implanted at the interface between the supraspinatus tendon and the humeral head in a rat rotator cuff repair model, these scaffolds promoted recruitment of endogenous tendon progenitor cells followed by integrative healing of tendon and bone via re-formation of strong fibrocartilaginous interfaces. Our findings demonstrate the potential of in situ tissue engineering of tendon-to-bone interfaces by endogenous progenitor cells. The in situ tissue engineering approach shows translational potential for improving outcomes after rotator cuff repair.