BMSCs differentiating into chondrocytes for repairing mandibular condylar cartilage defects

Purpose: To repair the full-thickness cartilaginous defects of mandibular condylar by transplanting bone marrow stromal cells (BMSCs) combined with chondrocytes.

Methods: 27 goats were included in this study. The goat's temporomandibular joint was opened-up and a dish-like full-thickness cartilaginous defect of condyle was made by a round-bur. The in-vitro cultured autologous BMSCs and auricular chondrocytes were mixed with injectable scaffold PluronicF-127 (Sigma, USA) and the construct was implanted into the defect with the cell concentration of 5*107/ml (the ratio between BMSCs and chondrocytes is 8:2) in the experimental groups (n=16, 4/gp). The same defects in the control groups (n=8, 2/gp) were implanted with only the Pluronic F-127 into the condylar articular cartilage defects. 4, 8, 12, and 24 weeks postoperatively, goats (4 in the experimental group and 2 in the control group) were sacrificed in each period. The recovery of the articular cartilage defects were detected and evaluated by gross observation, histopathology and immunochemical staining. In order to trace and evaluate the differentiation ability of the BMSCs in vivo, green fluorescent protein (GFP) labeled BMSCs, auricular chondrocytes and PluronicF-127 were implanted into the same defects in 3 goats. 4,8,12 weeks postoperatively, 1 goat was sacrificed and the restorative tissue of the defect was harvested for frozen-section and observed under laser confocal microscope.

Results: The full-thickness articular cartilage defects were well restored and appeared as the normal-cartilage layers in the experimental group with strong immunostaining of type II collagen while fibrous tissues seen in the control groups. GFP labeled cells were existed in the neocartilage under laser confocal microsope . In the control group, the cartilage defects were repaired with mixture of the fibrous cartilage-like tissues and osseous tissues.

Conclusions: The BMSCs can be differentiated by chondrocytes and play an important role in repairing the temporomandibular joint articular cartilage defects.