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Nonselective cation channel activation during wound healing in the corneal endothelium
1Department of Physiology and Biophysics, University of Tennessee, Memphis 38163, USA.
Abstract:
Rabbit corneas were injured by mechanical or thermal trauma. At several time points after wounding, corneal endothelial cells were isolated and their ion channels examined using standard and amphotericin perforated-patch whole cell patch-clamp configurations. Within 15-24 h after mechanical or thermal trauma, a nonselective cation current was observed in 79% of the cells examined that was not present in unwounded or sham-wounded corneas. By 73 h postwounding, the current was present in only 10% of the cells examined. The wound healing-induced current is outwardly rectifying, activates at depolarized voltages, shows no sign of inactivation, and is inhibited by flufenamic acid, quinidine, and acetate. In addition to this new current, it was observed that endothelial cells from freeze-wounded corneas no longer expressed the transient K+ current seen in control, sham, and mechanically wounded corneas. Corneal endothelial superfusion experiments found no significant difference in swelling rates between control and flufenamic acid-superfused wounded corneas, indicating that the wound healing-induced channel is not involved in the stromal hydration maintenance function of the corneal endothelium.
Insights
A novel nonselective cation current appears in rabbit corneal endothelial cells within 24 hours of injury but diminishes by 73 hours. This wound-healing current is not involved in maintaining corneal hydration.
Area of Science:
- Ophthalmology
- Cell Biology
- Ion Channel Physiology
Background:
- Corneal wound healing is crucial for maintaining vision.
- The corneal endothelium plays a vital role in regulating stromal hydration.
- Ion channel activity in corneal endothelial cells is implicated in cellular function and repair.
Purpose of the Study:
- To investigate the changes in ion channel activity in corneal endothelial cells following mechanical or thermal injury.
- To characterize a novel ion current induced during corneal wound healing.
- To determine the role of this wound-induced current in corneal hydration maintenance.
Main Methods:
- Rabbit corneas were subjected to mechanical or thermal trauma.
- Corneal endothelial cells were isolated at various time points post-wounding.
- Whole-cell patch-clamp electrophysiology was used to examine ion channel function.
- Flufenamic acid and quinidine were used to inhibit specific ion currents.
- Corneal endothelial superfusion experiments assessed stromal hydration rates.
Main Results:
- A nonselective cation current, not present in control corneas, was observed in 79% of wounded corneal endothelial cells within 15-24 hours.
- This wound-induced current decreased significantly by 73 hours post-wounding.
- The current exhibited outward rectification, activated at depolarized voltages, and was inhibited by flufenamic acid, quinidine, and acetate.
- Endothelial cells from freeze-wounded corneas lacked the transient K+ current found in controls.
- Superfusion experiments showed no difference in swelling rates between control and treated wounded corneas.
Conclusions:
- A transient, nonselective cation current is induced in corneal endothelial cells during the early stages of wound healing.
- This wound-healing-induced current is distinct from the transient K+ current and is not responsible for maintaining corneal hydration.
- Further research is needed to elucidate the specific role and molecular identity of this novel ion channel in corneal repair processes.