An impact of masticatory muscle function on IL-1beta and SOX9 expression in condyle.

The importance of masticatory muscle function on the growth and differentiation of condyle was examined. The aim of this study was to investigate how reduced masticatory muscle function influences intrinsic regulatory factors which govern growth and differentiation of condylar cartilage. Masseter muscles of 3-week-old Wistar rats were resected bilaterally. Masseteric resected animals and corresponding control animals were sacrificed at 3, 6, 12 and 21 days post-resection. The condyles were then processed for histological and immunohistochemical analysis. The expression patterns of an inhibitory regulator (IL-1beta) and a master regulator (Sox9) of chondrogenesis in condylar cartilage of growing rats were investigated. Quantitative analysis shows that masseteric resection significantly increased the number of IL-1beta positive cells in proliferative layer. In contrast, the number of Sox9 positive cells was significantly decreased compared to the control animals. It can be concluded that the reduced articular function due to masseteric resection decreased condylar cartilage cell differentiation which led to the decrease in the thickness of condylar cartilage.