Temporomandibular joint disorders predominantly afflict women, suggesting a role for estrogen in the disease process. In bone, estrogen inhibits mechanical-loading induced periosteal bone formation. We were interested to see whether a similar mechanism occurs in the periosteal-derived mandibular condylar cartilage. In a model of decreased occlusal loading, we found that early chondrocyte differentiation (Sox9 and Collagen type 2) was inhibited in female but not male WT mice. The purpose of this study was to examine the effects of estrogen receptor beta in mediating these sex differences.
Method: 21-day-old male (n=23) and female (n=22) ER beta KO mice were exposed to normal or decreased occlusal loading (soft diet administration and 1 mm incisor trimming every other day) for a period of 4 weeks. The mice were sacrificed at 49 days of age. Histological analyses, gene expression of chondrocyte markers, micro-CT analyses of the subchondral bone microarchitecture and cell proliferation were evaluated for each of the groups.
Result: In both male and female ER beta KO mice decreased occlusal loading caused a significant decrease in collagen type 10 expression, subchondral bone volume, and trabecular number, compared with sex matched normal loading controls
Conclusion:
In decreased occlusal loading models, sex differences in early chondrocyte maturation were not found in the ER beta KO mice. Greater understanding in the role of estrogen in mediating TMJ mechanical loading induced remodeling is critical in order to determine the sex predilection of TMJ diseases.