Stanniocalcin‐1 mediates negative regulatory action of epidermal layer on expression of matrix‐related genes in dermal fibroblasts

Dermal–epidermal interaction plays a role in many pathophysiological processes, such as tumor invasion and psoriasis, as well as wound healing, and is mediated at least in part by secretory factors. In this study, we investigated the factor(s) involved. We found that stanniocalcin‐1 (STC1), a cytokine, is expressed at the basal layer of epidermis. Knockdown of STC1 with siRNA in HaCaT cells decreased matrix metalloproteinase 1 (MMP1) expression, suggesting that STC1 serves as an autocrine factor, maintaining MMP1 mRNA expression in the epidermal layer. In dermal fibroblasts, STC1 increased MMP1 mRNA expression and decreased collagen1A1 and elastin mRNA expression. These actions were inhibited by SP600125, a jun kinase (JNK) inhibitor. Nuclear translocation of AP‐1, a downstream signal of JNK, was implicated in the actions of STC1. In a coculture system of HaCaT cells and fibroblasts, used as a model of dermal–epidermal interaction, knockdown of STC1 in HaCaT cells with siRNA reduced the negative effects (i.e., induction of MMP1 and decrease of collagen1A1 and elastin) of STC1 on fibroblasts. These results suggest that STC1 secreted from the epidermal layer is a mediator of dermal–epidermal interaction.