In this study, a novel three-dimensional poly (lactide-co-glycolide) (PLGA)/nano-hydroxyapatite (NHA) scaffold was fabricated by a thermally induced phase separation technique and its potential application in cartilage tissue-engineering was investigated. The PLGA scaffold was used as a control and mesenchymal stem cells (MSCs) were seeded in both scaffolds. After 12-days culture, SEM images and confocal laser scanning microscopy illustrated that MSCs attached more moderately and more cells distributed in PLGA/NHA scaffolds. MTT test and DNA assay showed that the viability and proliferation of MSCs in PLGA/NHA scaffolds were significantly superior to PLGA scaffolds during in vitro culture. Through in vivo study, the efficacy of this scaffold combining with MSCs for repairing articular osteochondral defects was evaluated in a rat model. Osteochondral defects in rats knees were left untreated, or treated with PLGA/NHA-MSCs composites or PLGA-MSCs composites. Twelve weeks after operation, histological examination revealed that the defects in the PLGA/NHA-MSCs treated group were filled with smooth and hyaline-like cartilage with abundant glycosaminoglycan and collagen type II deposition, but deficient in collagen type I at 12 weeks after operation. To investigate the final fate of MSCs transplanted into the defect areas, the fluorescent dye CM-DiI was used to prelabel cells. At 12 weeks after transplantation, we still observed the red fluorescence in the repair area. These findings suggest that the PLGA/NHA-MSCs composite may be potentially used for cartilage repair in clinical application. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.