Expression of Ihh signaling pathway in condylar cartilage after bite-raising in adult rats.

Temporomandibular joint osteoarthritis (TMJOA) is a complex inflammatory condition with multiple factors and degenerative processes co-occurring. However, its pathogenesis remains uncertain. The purpose of the study was to observe the expression of Indian hedgehog (Ihh) signal related molecules in TMJOA induced by bite-raising and to study the effect and mechanism of Ihh signaling. Our research indicated that Ihh signaling pathway can be activated in condylar cartilage induced by bite-raising. The histological analysis showed TMJOA-like structural changes of condylar cartilage in experiment groups. Ihh, Smoothened (Smo), and Gli zinc finger transcription factors-1 (Gli-1) were activated in the experimental groups, and the expression levels increased significantly over time, whereas the sham control groups showed no fluctuation. Additionally, the expression levels of matrix metalloproteinase-13 (MMP-13) and cysteinyl aspartate specific proteinase-3 (Caspase-3) in the experiment groups increased in a time-dependent manner compared with the matched sham control groups. In conclusion, our results indicated that the Ihh signaling pathway may activate the occurrence of TMJOA by mediating the hypertrophy of chondrocytes, which may be an important regulatory mechanism and potential therapeutic target in the repair of condylar cartilage.