An Osteochondral Tissue-Mimicking Hydrogel-Scaffold Di-Block Patch for Rapid Repair of Focal Load-Bearing Cartilage Lesions.

Load-bearing cartilage lesions are progressive, so focal lesions require rapid repair to support loading; otherwise, they may generate degeneration of a large area of cartilage till worse osteoarthritis occurs. Replacing the focally lesioned cartilage with synthetic grafts can instantly recover the damaged cartilage's load-bearing capacity, but have issues with mismatched mechanical properties and weak cartilage integration. Inspired by natural osteochondral tissue, a hydrogel-titanium scaffold (gel-Ti) di-block patch with a robust interlocking interface is developed. In this osteochondral tissue-mimicking gel-Ti patch, the hydrogel layer offers mechanical properties comparable to those of native cartilage, whereas the titanium scaffold layer with pores for bone ingrowth integrates the patch with subchondral bone and thus host cartilage. Consequently, the gel-Ti patch achieves prompt and effective repair of load-bearing cartilage defects in rabbit and canine models, in striking contrast to the dry and rigid ultra-high-molecular-weight polyethylene (UHMWPE) patch that induces progressive cartilage destruction. Moreover, the gel-Ti patch shows favorable chondroprotective effects, durable mechanical properties, and long-term safety. This work reveals a new approach to address the urgent clinical need to rapidly restore focal cartilage damage to withstand loading, thereby preventing further worsening of cartilage and joints.