Gap Junctional Versus Paracrine Signaling in the Human Lens Epithelium: Analysis Based on Multicellular Ca²⁺ Imaging...

Area of Science:

• Ophthalmology
• Cell Biology
• Biophysics

Background:

• Intercellular communication via calcium (Ca²⁺) waves is vital for lens epithelial cell (LEC) function and homeostasis.
• Disruption of LEC communication is linked to cataract development.
• Understanding Ca²⁺ wave propagation mechanisms is key to addressing lens dysfunction.

Purpose of the Study:

• Investigate the roles of gap-junctional coupling and ATP-mediated paracrine signaling in human lens epithelial Ca²⁺ wave propagation.
• Determine the contribution of these pathways to mechanically induced Ca²⁺ waves.
• Elucidate the mechanisms underlying Ca²⁺ signaling in the human lens epithelium.

Main Methods:

• Multicellular Ca²⁺ imaging on human lens capsule preparations from cataractous lenses.
• Pharmacological assessment using apyrase (ATP hydrolysis) and carbenoxolone (gap-junction blocker).
• Development of a biophysically detailed computational model simulating Ca²⁺ dynamics, gap-junctional IP₃/Ca²⁺ diffusion, and extracellular ATP signaling.

Main Results:

• Apyrase partially reduced Ca²⁺ wave extent, amplitude, and duration, but not speed.
• Carbenoxolone significantly inhibited wave transmission, restricting it to adjacent cells.
• Computational modeling indicated that a hybrid mechanism of gap-junctional communication and ATP release was necessary to replicate experimental findings.

Conclusions:

• Mechanically induced Ca²⁺ waves in the human lens epithelium are mediated by a cooperative interplay between gap-junctional and ATP-based paracrine signaling.
• This dual-pathway mechanism is essential for coordinated cellular responses supporting lens homeostasis and transparency.
• The findings provide insights into cellular communication critical for preventing lens pathologies like cataracts.