Expression Distribution of Keratins in Normal and Pathological Corneas and the Regulatory Role of Krt17 on Limbal Stem Cells.

PURPOSE: This study aimed to compare variations in keratins (KRTs), particularly stress KRTs, under normal and pathological conditions, with a specific focus on investigating the role of KRT17. METHODS: This research examined changes in KRT and limbal stem cell (LSC) markers in normal and various pathological corneas using mRNA and proteomic sequencing data alongside single-cell sequencing data from normal mouse corneas. The effects of the Krt17 recombinant protein and specific small interfering RNA on the clonal formation and proliferation of human limbal epithelial cells (HLECs) were investigated. mRNA sequencing was conducted on Krt17 knockdown HLECs, and the findings were validated using qPCR, immunofluorescence staining, neutrophil chemotaxis, and herpes simplex virus 1 infection assay. The STRING database was used to predict Krt17's interacting proteins. RESULTS: Various KRTs in the corneal epithelia exhibited differences in expression levels and patterns. Under pathological conditions, stress KRTs Krt17 and Krt16 were upregulated, while differentiation-related Krt12 was downregulated, and the expression of the LSC markers Krt17, Krt14, and IFITM3 were commonly increased. Supplementation and intervention experiments confirmed that Krt17 promotes clonal formation and proliferation in HLECs. Krt17 knockdown resulted in the upregulation of genes related to inflammation and defense responses, while downregulating molecules associated with differentiation pathways. Krt17 knockdown promoted neutrophil chemotaxis and alleviated herpes simplex virus 1 infection in HLECs. CONCLUSIONS: KRTs play a crucial role in the homeostasis and pathological regulation of the corneal epithelium. The stress Krt17 located in LSCs is involved in regulating the stemness, proliferation, and differentiation of LSCs, as well as immune and defense responses.