Site-Specific Expression of HOXA Genes in Skin and its Effect on Skin Elasticity

The skin, the body's largest organ, covers the entire body and consists of 3 layers: the epidermis, dermis, and subcutaneous tissue. Its structure and properties vary by body region. Although HOX genes are implicated in mechanisms contributing to regional skin property differences, their influence is not completely understood. In this study, we focused on the relationships between HOX gene expression to regional differences in dermal structure and skin elasticity. Our results revealed significantly higher HOXA cluster expression in skin tissues and cells derived from the body in comparison with those derived from the face. Among HOXA genes highly expressed in the body, HOXA9 was found to regulate dermal fibroblast proliferation and extracellular matrix–related gene expression, both associated with skin elasticity. Furthermore, HOXA9 was shown to affect cell proliferation and extracellular matrix–related gene expression through insulin-like GF 1 signaling. Collectively, our findings suggest that HOXA genes are expressed differently in different body regions, variably affecting dermal structure and cellular functions, thus contributing to regional variation in the skin.