In situ grown bacterial cellulose-based integrated biphasic biomimetic scaffold for synchronous repair of critical-sized osteochondral defects

Regenerating critical-sized osteochondral defects poses a significant challenge due to the need to simultaneously restore biphasic tissue structures and reconstruct a mechanically stable osteochondral interface. Transcriptomic analysis has identified Matrix Metalloproteinase-2 (MMP2), Matrix Metalloproteinase-9 (MMP9), and Osteoprotegerin (OPG) as crucial regulatory genes in this repair process. Molecular docking analysis suggests that the natural compound icariin (ICA) can bind to and potentially modulate these genes. To address this, we developed a biomimetic biphasic scaffold using in situ bacterial cellulose (BC) growth technology combined with ICA-loaded PLGA microspheres (ICA@PLGA). The scaffold comprises a cartilage layer of BC hydrogel and a bone layer of a 3D-printed PLGA/β-TCP composite. Characterization confirmed strong interfacial integration through a three-dimensional interlocking architecture and hydrogen-bonding network, enabling sustained release of ICA. In vitro studies demonstrated enhanced osteogenic and chondrogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) by the scaffold. In vivo evaluation in rabbit femoral head osteochondral defect model further validated the scaffold's ability to promote synchronized osteochondral repair and regeneration by regulating MMP2/MMP9 expression and OPG levels. Histological and radiological analyses revealed regenerated tissues resembling native subchondral bone and hyaline cartilage, with anisotropic collagen fiber alignment. This study introduces an integrated therapeutic approach that combines biomimetic scaffold design with targeted molecular regulation for treating critical-sized osteochondral defects in clinical settings.