Strengthening of the barrier function in human telomerase reverse transcription (hTERT) immortalized corneal and conjunctival epithelium by double-stranded RNA

To investigate the response to polyinosinic:polycytidylic acid [poly(I:C)], a double-stranded RNA Toll-like receptor 3 agonist that mimics viral infection, in the barrier function of two established human telomerase reverse transcriptase-immortalized cell lines, termed HCLE for the human corneal-limbal epithelial line and HCjE for the human conjunctival-epithelial line. In this study, HCLE and HCjE cells were used to evaluate the underlying mechanism of epithelial-cell barrier function regulation. Briefly, HCLE and HCjE cells were first cultured on 12-well Transwell® (Corning®) filter-plates, and reverse transcription-polymerase chain reaction, western blotting, and immunohistochemical examinations were then performed to assess tight junction (TJ)-related protein expression and cellular distribution. Next, the barrier function of the cells was measured via transepithelial electrical resistance (TEER) and paracellular molecular flux. The cells were then stimulated with poly(I:C) and the TEER and TJ-related protein expressions were analyzed. Similar to that in in vivo epithelium, the expression of claudin (CLDN) subtypes CLDN-1, -4, and -7 was observed in the HCLE and HCjE cells, and the barrier function in the HCLE cells was tighter than that in the HCjE cells. Post stimulation with poly(I:C), TEER of the HCLE and HCjE cells increased in a dose- and time-dependent manner, the production of TJ-related protein mRNA and CLDN-4 protein were elevated, and the barrier function of the HCLE and HCjE cells increased, thus possibly indicating that the increased barrier function is a defense mechanism against viral infection.