Increased fragility and acceleration of migration of corneal epithelial cells in an epiplakin deficiency

Abstract

Purpose: Epiplakin is one of intermediate filament-related components. To examine fragility and mechanism of migration of corneal epithelial cells in an epiplakin deficiency. We previously reported that the loss of epiplakin facilitates healing of a defect in corneal epithelium in mice (ARVO 2009), and epiplakin knockdown by Short-interfering RNA (siRNA) was accelerated the migration of HCEC and suppressed TGFb1 activation of p38 and JNK signals (ARVO2012).

Methods: (1) We used Epiplakin KO (KO) (n=4) and wild type (WT) (n=4). The corneal surface was gently brushed with a surgical micro-sponge. Then ultrathin sections were cut and observed under transmission electron microscopy. (2) We ran real-time RT-PCR for cell-cell connection-related components in RNA samples obtained from KO (n=12)and WT (n=12). (3)Effect of siRNA knockdown of EPPK on E-cadherin expression was also studied in AV40- immortalized corneal epithelial cells by using western blotting.

Results: (1)Transmission electron microscopy showed that each layer of the epithelial cells was well maintained following brushing in a WT epithelium although partial separation between cells of the superficial layer. In a KO epithelium one or two layer(s) of basal or supra-basal epithelial cells were found to be in the original position following the treatment and upper layer cells were found to be removed. (2)Real-time RT-PCR also showed that mRNA expression of E-cadherin was suppressed by the loss of epiplakin, while that of desmoglein-1 or desmoplakin-1 was not affected by epiplakin gene knockout in a mouse cornea. (3)EPPK knockdown suppressed E-cadherin expression in the cells.

Conclusions: The loss of epiplakin affects the corneal epithelium integrity. The mechanism of acceleration of cell migration in the KO corneal epithelium is to be further investigated, although suppression of expression of E-cadherin in the absence of EPPK might be included. The possibility of the potential corneal epithelium disturbance in the patient who has abnormalities to EPPK was suggested.

Keywords: 482 cornea: epithelium