BMP2 Signaling in Mechanical Loading of Mandibular Condylar Cartilage

Objectives: The mandibular condylar cartilage remodels in response to mechanical load by regulating chondrogenesis and endochondral ossification, in order to achieve a balance between mechanical load and the remodeling capacity of the mandibular condylar cartilage. The purpose of this study was to examine the effects of static compressive loading on the mandibular condylar cartilage. We hypothesized that BMP2 signaling plays a key role and is required for sensing of mechanical loading in mandibular condylar cartilage.
Methods: Four-week old triple transgenic mice (Dkk3 X Col2A1 X Col10A1) were divided into two groups: (1) Unloaded, (2) Loaded (5 days with 50cN of compressive force). All the animals were injected with Ethynyl Deoxyuridine (EDU) 24 hours before euthanization. Immunohistochemistry, gene expression, microCT and rate of proliferation were analyzed and compared.
Results: Our histology indicated a significant increase in the number of the Dkk3 and Col10A1 expressing cells in the loaded group. There is increased BMP2 and Sox 9 expression, increased chondrocyte proliferation, but decreased SOST expression. Moreover, there was significant increase in the bone volume fraction and the trabecular thickness in the loaded group.
Conclusions: The increased expression of BMP2 is associated with the adaptive remodeling of the mandibular condylar cartilage after static compressive load.