Abstract

P 027

New insights into electrophysiology and ion channel expression in the human corneal endothelium

Mergler S., Pleyer U.
Charité - Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augenklinik, Berlin

Objective: The corneal endothelium plays a crucial role in the physiology and tranparency of the human cornea. During life the number of endothelial cells decreases. Moreover, endothelial cell loss is accelerated after various impairments such as surgical trauma (e.g. cataract extraction) and following corneal transplantation. Importantly, this cell loss is associated with programmed cell death (apoptosis) and changed ion channel activity. So far, little is known about the electrophysiology and ion channel expression (e.g. Ca²⁺ channels) in corneal endothelial cells.
Methods: Immortalized human corneal endothelial cells were used as an established cell model (HCEC-SV40). Effects of the various selective and potent ion channel modulators on [Ca²⁺]_i and on Ca²⁺ permeable ion channel activity were investigated by highly sensitive measuring methods (cell fluorescence imaging, patch-clamping).
Results: Extracellular application of different established calcium channel tools clearly influence calcium regulation (e.g. reduction of L-type Ca²⁺ channel activity by nifidipine). Furthermore, artificial cooling agents such as the highly potent activator icilin for cold receptors (TRPM8) clearly modulate intracellular calcium. Specifically icilin (10 µM) increased [Ca²⁺]_i from 109±6 nM to 178±7 nM after 3 min followed by full recovery (114±5 nM) to the baseline (±SEM; n=6).
Conclusions: Various ion channel activities and receptors in human corneal endothelial cells could be detected by highly sensitive measuring methods. This new field not only will help to better understand physiological functions of the cornea, but also may have direct clinical implications. For example, rinse solutions for intraocular surgery can be optimised after detailed investigations or different temperature control during corneal storage may play a pivotal role in retaining viability of stored human corneas.

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