The Role of Collagen VI α6 Chain Gene in Atopic Dermatitis

BACKGROUND: In a previous study, we carried out whole-exome sequencing to identify genetic variants associated with early onset atopic dermatitis (AD) in Koreans and found that collagen VI α6 chain (COL6A6) gene polymorphisms are associated. COL6A6 is one of the chains that makes up the triple helix of collagen VI, and little is known about its role in AD. OBJECTIVE: To identify how COL6A6 changes in AD and clarify its role. METHODS: Immunohistochemical staining for COL6A6 was performed on tissues of AD, other skin diseases, and healthy controls. Human keratinocytes and fibroblasts were exposed to inflammatory cytokines and cultured to evaluate changes in COL6A6 expression. COL6A6 small interfering RNA (siRNA) was transfected into cells to identify the role of COL6A6. RESULTS: Total COL6A6 mRNA was higher in AD than in controls. In AD tissues, COL6A6 mRNA decreased significantly in the epidermis compared to controls, whereas COL6A6 protein was increased in the dermis. In the cultured cells, COL6A6 mRNA was suppressed in the epidermis by interleukin (IL)-4 and IL-13, whereas COL6A6 protein was induced in the dermis. In the COL6A6 siRNA-transfected keratinocyte, mRNA of FLG, LOR, and CASP14 decreased compared to controls; in contrast, mRNA of MMP1 increased. CONCLUSION: The reduction of epidermal COL6A6 due to the genetic mutation can cause skin barrier damage and it can contributes to the early onset of AD. COL6A6 is induced by IL-4 and IL-13, and it may play a role in fibrotic remodeling and inflammatory processes, which are major features of AD.