[Role of DNA methyltransferase 1 in mouse skin aging]

To explore the role ofDNA methyltransferase 1 (DNMT1) in mouse skin aging.
 Methods: Epidermal conditional K14 Cre-mediated DNA methyltransferase 1 (DNMT1) knockout mice (Mut group, n=4) and the littermate normal mice with the same age (WT group) n=4) were used in this study. HE staining was used to detect the pathological changes of skin; the changes of number in the dermal elastic fibers were detected by Gomori aldehyde fuchsin staining, the number of 5-bromo-2-deoxyuridine (BrdU)-labeled transit amplifying cells (TAC) in epidermis were detected by immunohistochemical staining; the number of chlorodeoxyuridine (CldU)-label-retaining cells (LRC) in epidermis were detected by immunofluorescent staining.
 Results: Compared with the WT group, the skin showed premature aging symptoms in the Mut group concomitant with the decreased epidermal thickness as well as the number of dermal collagen fibers, while the increased dermal elastic fiber fracture. Compared with the WT group, the number of TAC in the epidermis was significantly increased (P<0.05), and the number of LRC was significantly decreased (P<0.05) in the Mut group.
 Conclusion: The phenotype of skin premature aging in epidermal stem cell conditional DNMT1-knockout mice suggests an important role of DNMT1 in skin aging.