Sirt6 deficiency impairs corneal epithelial wound healing

Corneal transparency, dependent on the integrity of epithelial cells, is essential for vision. Corneal epithelial damage is one of the most commonly observed ocular conditions and proper wound healing is necessary for corneal transparency. Sirt6, a histone deacetylase, has been shown to regulate many cellular events including aging and inflammation. However, its specific role in corneal epithelial wound healing remains unknown. Here we demonstrated that Sirt6 was expressed in corneal epithelial cells and its expression decreased with age. In an in vivo corneal epithelial wound healing model, Sirt6 deficiency resulted in delayed and incomplete wound healing and was associated excessive inflammation in the corneal stroma and dysfunction of Notch signaling, leading to keratinization of the corneal epithelium and corneal opacity. Aging Sirt6-deficient mice spontaneously developed corneal keratitis with extensive infiltration of inflammatory cells into the cornea. In vitro experiments demonstrated that primary corneal epithelial cells with Sirt6 downregulation expressed increased basal levels of inflammatory genes and exhibited hyper-inflammatory reactivity to IL-1 beta and TNF alpha treatment. These results provide compelling evidence that Sirt6 is a critical regulator of inflammation in the cornea, and is responsible for corneal epithelial wound healing, thus contributing to the maintenance of epithelial integrity and corneal transparency.