Hyaluronan synthase 3 regulates hyaluronan synthesis in cultured human keratinocytes

Three human hyaluronan synthase genes (HAS1, HAS2, and HAS3) have been cloned, but the functional differences between these HAS genes remains obscure. The purpose of this study was to examine which of the HAS genes are selectively regulated in epidermis. We examined the relation of changes between hyaluronan production and HAS gene expression when cytokines were added to cultured human keratinocytes. Interferon-gamma increased hyaluronan production whereas transforming growth factor beta decreased it. Both cytokines affected preferentially high-molecular-mass (> 106 Da) hyaluronan production. Consistent with the change in hyaluronan synthesis, we found that interferon-gamma markedly upregulated HAS3 mRNA whereas transforming growth factor beta downregulated HAS3 transcript levels. The expression of HAS1 mRNA was not significantly affected by either cytokine, and HAS2 mRNA expression was undetectable under either basal or cytokine-stimulated conditions by northern blot using total RNA. Furthermore, in situ mRNA hybridization showed that mouse epidermal keratinocytes abundantly expressed HAS3 mRNA from the basal to the granular cell layers, suggesting that HAS3 functions in epidermis. These findings suggest that HAS3 gene expression plays a crucial role in the regulation of hyaluronan synthesis in the epidermis.