Abstract:[Objective] To investigate the effect of bone marrow mesenchymal stem cells (BMSCs) composied with nano-polyaiticglycolic acid (PLGA) frame on repairing femoral cartilage defect in rats. [Methods] BMSCs were obtained from the bone marrow cavity of the tibia and femur of rats, cultured and passed through, and then cultured on the nano-PLGA scaffold frame, and the graft was observed under electron microscope. Eighteen SD rats were operated on both hind limbs to create cartilage defect on the distal femur, and the defect on the right side was filled with BMSC-PLGA composited material (the graft group), whereas the defect on the left side left not further treated [the blank control (BC) group]. Gross and histological observation and scoring, as well as optical density values measured in toluidine blue staining and immunohistochemical staining were compared between the two groups. [Results] BMSCs grew in a unique spiral shape, the PLGA frame showed fiber interwoven network structure under electron microscope, and BMSCs grew well on the PLGA frame. At 1 and 3 months after implantation, the graft group proved significantly superior to the BC group in terms of gross observation scores [(8.1±0.8) vs (1.7±0.8), P< 0.001; (10.3±1.2) vs (3.8±1.5), P<0.001], histological score [(11.6±1.0) vs (4.0±0.9), P<0.001; (15.5±1.0) vs (4.8±0.8), P<0.001], toluidine blue staining OD value [(0.2±0.0) vs (0.1±0.0), P<0.001; (0.4±0.0) vs (0.1± 0.0), P<0.001], in addition, immunohistochemical II collagen detection OD value [(0.4±0.0) vs (0.1±0.0), P<0.001] 3 months postoperatively. [Conclusion] BMSCs -PLGA composition does effectively repair cartilage defects in rats in this study, demonstrating a potential tissue engineering modification method for the treatment of cartilage defects.