Regulation of DNA methylation levels in the process of oral mucosal regeneration of oral ulcer model
Naotaro Akiyama1,2, Tomomi Yamamoto-Fukuda2,3, Mamoru Yoshikawa1 and Hiromi Kojima3
1Department of Otorhinolaryngology, Toho University, School of Medicine, Tokyo, 2Department of Histology and Cell Biology, Nagasaki University, Graduate School of Biomedical Sciences, Nagasaki and 3Department of Otorhinolaryngology, Jikei University, School of Medicine, Tokyo, Japan
Offprint requests to: Naotaro Akiyama, Department of Otorhinolaryngology, Toho University, School of Medicine, Ohashi Meguro-ku, 2-22-36, Tokyo 153-8515, Japan. e-mail: naotaro.akiyama@med.toho-u.ac.jp
Summary. DNA methylation is an important epigenetic mechanism for cellular maintenance. However, the methylation pattern and the key molecule regulated epigenetically in oral mucosal regeneration is unclear. In this study, we generated a rat oral ulcer model and investigated the cell proliferative activities and DNA methylation patterns immunohistochemically. We also performed immunohistochemical analysis of a regulator of epithelial stem/progenitor cell differentiation in the rat model.
We demonstrated immunohistochemistry using antibodies for the molecules as follows: Ki-67, a marker of cellular proliferation; 5-methylcytosine (5-mC), a marker of DNA methylation; 5-hydroxymethylcytosine (5-hmC), a marker of DNA demethylation; Dnmt1, a maintenance DNA methyltransferase; Dnmt3a and Dnmt3b, de novo DNA methyltransferases; and Wnt5a, a regulator of stem/progenitor cell differentiation.
In this model, re-epithelialization was completed at Day 4 after ulceration. Regenerating mucosal hypertrophy reached a peak at Day 5 and appeared normal at Day 14. Ki-67-positive cells increased at Day 2 and returned to normal at Day 6 after ulceration. The ratio of the expression level of 5-mC to 5-hmC declined at Day 5 and returned to normal at Day 6. The expression level of Dnmt1 had not changed compared to the normal control at every time point. On the other hand, the expression levels of Dnmt3a and Dnmt3b had decreased significantly at Day 5 and returned to normal at Day 6. Moreover, Wnt5a-positive cells increased at Day 5.
In conclusion, oral mucosal regeneration was strictly regulated by DNA methylation. Moreover, Wnt5a might play a critical role in oral mucosal regeneration. Histol Histopathol 35, 247-256 (2020)
Key words: DNA methylation, 5-mC, 5-hmC, Wnt5a, oral ulcer
DOI: 10.14670/HH-18-147