Mohawk transcription factor regulates homeostasis of the periodontal ligament [RESEARCH ARTICLE]

Naoki Koda, Tempei Sato, Masahiro Shinohara, Shizuko Ichinose, Yoshiaki Ito, Ryo Nakamichi, Tomohiro Kayama, Kensuke Kataoka, Hidetsugu Suzuki, Keiji Moriyama, and Hiroshi Asahara

The periodontal ligament (PDL), which connects the teeth to the alveolar bone, is essential for periodontal tissue homeostasis. Although the significance of the PDL is recognized, molecular mechanisms underlying PDL function are not well-known. We report that Mohawk homeobox (Mkx), a tendon-specific transcription factor, regulates PDL homeostasis by preventing its degeneration. Mkx is expressed in the mouse PDL at the age of 10 weeks and 12 months. In Mkx^–/– mice, age-dependent expansion of the PDL at the maxillary 1^st molar (M1) furcation area was observed. Transmission electron microscopy (TEM) revealed that Mkx^–/– mice presented collagen fibril degeneration in PDL with age, while the collagen fibril diameter gradually increased in Mkx^+/+ mice. PDL cells lost their shape in Mkx^–/– mice, suggesting changes in PDL properties. Microarray and quantitative polymerase chain reaction (qPCR) analyses of Mkx^–/– PDL revealed an increase in osteogenic gene expression and no change in PDL- and inflammatory-related gene expression. Additionally, COL1A1 and COL1A2 were upregulated in Mkx-overexpressing human PDL fibroblasts, whereas osteogenic genes were downregulated. Our results indicate that Mkx prevents PDL degeneration by regulating osteogenesis.

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