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Aptamer-Functionalized Bioscaffold Enhances Cartilage Repair by Improving Stem Cell Recruitment in Osteochondral Defects of Rabbit Knees

Background: Recruitment of endogenous stem cells has been considered an alternative to cell injection/implantation in articular cartilage repair. Purpose: (1) To develop a cartilage tissue-engineering scaffold with clinically available biomaterials and functionalize the scaffold with an aptamer (Apt19s) that specifically recognizes pluripotent stem cells. (2) To determine whether this scaffold could recruit joint-resident mesenchymal stem cells (MSCs) when implanted into an osteochondral defect in a rabbit model and to examine the effects of cartilage regeneration. Study Design: Controlled laboratory study. Methods: The reinforced scaffold was fabricated by embedding a silk fibroin sponge into silk fibroin/hyaluronic acid–tyramine hydrogel and characterized in vitro. A cylindrical osteochondral defect (3.2 mm wide × 4 mm deep) was created in the trochlear grooves of rabbit knees. The rabbits were randomly assigned into 3 groups: Apt19s-functionalized scaffold group, scaffold-only group, and control group. Animals were sacrificed at 6 and 12 weeks after transplantation. Repaired tissues were evaluated via gross examination, histologic examination, and immunohistochemistry. Results: In vitro, this aptamer-functionalized scaffold could recruit bone marrow–derived MSCs and support cell adhesion. In vivo, the aptamer-functionalized scaffold enhanced cell homing in comparison with the aptamer-free scaffold. The aptamer-functionalized scaffold group also exhibited superior cartilage restoration when compared with the scaffold-only group and the control group. Conclusion: The Apt19s-functionalized scaffold exhibited the ability to recruit MSCs both in vitro and in vivo and achieved a better outcome of cartilage repair than the scaffold only or control in an osteochondral defect model. Clinical Relevance: The findings demonstrate a promising strategy of using aptamer-functionalized bioscaffolds for restoration of chondral/osteochondral defects via aptamer-introduced homing of MSCs.