Activation Of B-Catenin Signalling Leads To Temporomandibular Joint Defects

Despite extensive research in knee and hip osteoarthritis (OA), the underlying mechanism of temporomandibular joint (TMJ) disorder remains largely unknown. The purpose of this study was to determine whether the constitutive activation of β-catenin in the middle and deep layers of the articular cartilage can compromise the homeostasis of this tissue in the TMJ. Co12CreERT2 transgenic mice were bred with RosamT/mG reporter mice to determine Cre recombination efficiency. Co12CreERT2 mice were then crossed with β-cateninflox (ex3)/+ mice to generate β- catenin conditional activation mice, β-catenin(ex3) Co12ER. TMJ samples were harvested when the mice were 1-, 3- or 6-month-old and evaluated using histology, histomorphometry and immunohistochemistry. β-catenin(ex3) Co12ER mice were further crossed with Mmp13flox/flox and Adamts5−/− mice to generate β-catenin(ex3)/Mmp13) Co12ER and β-catenin(ex3) Co12ER)/Adamts5−/− double mutant mice to investigate the role of Mmp13 and Adamts5 in the development of TMJ disorder. High levels of Cre-recombination were seen in Co12CreERT2;RosamT/mG mice. Progressive TMJ defects developed in 1-, 3- and 6-month-old β-catenin(ex3) Co12ER mice, as revealed by histology and histomorphometry. Results further demonstrated that the defects observed in β-catenin(ex3) Co12ER mice were significantly decelerated after deletion of the Mmp13 or Adamts5 gene in (β-catenin(ex3)/Mmp13) co12ER or β-catenin(ex3) Co12ER/ Adamts5−/− double mutant mice. In summary, we found that β-catenin is a critical gene in the induction of TMJ cartilage degeneration, and over-expressing β-catenin in TMJ cartilage leads to defects assembling an OA-like phenotype. Deletion of Mmp13 and Adamts5 in β-catenin(ex3) Co12ER mice ameliorates the development of TMJ defects. This study suggests that Mmp13 and Adamts5 could be potential therapeutic targets for the treatment of TMJ disorders