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

Effective intercellular communication among lens epithelial cells (LECs) is essential for lens homeostasis, and its disruption has been implicated in cataract formation. This study investigates the mechanisms of calcium (Ca²⁺) wave propagation in the human lens epithelium, focusing on the respective roles of gap-junctional coupling and ATP-mediated paracrine signaling.

We performed multicellular Ca²⁺ imaging on human postoperative anterior lens capsule preparations obtained from cataractous lenses during cataract surgery which retained intact monolayers containing viable LECs. Mechanically induced Ca²⁺ waves were recorded, and the contribution of specific signaling pathways was evaluated by pharmacological intervention using apyrase (an ATP-hydrolyzing enzyme) and carbenoxolone (CBX; a gap-junctional blocker). To interpret the experimental results, we developed a biophysically detailed computational model of the LEC monolayer, incorporating intracellular Ca²⁺ dynamics, gap-junctional IP₃/Ca²⁺ diffusion, and extracellular ATP signaling.

Apyrase moderately reduced the spatial extent, amplitude, and duration of Ca²⁺ waves without affecting propagation speed. In contrast, CBX significantly suppressed wave transmission, limiting activation to cells directly adjacent to the stimulation site. Simulations reproduced key experimental features and indicated that neither pure gap-junctional nor purely paracrine signaling mechanisms alone could explain the observed dynamics. Instead, a hybrid mechanism combining gap-junctional communication and partially regenerative ATP release was required.

Our results highlight the cooperative roles of gap-junctional and ATP-based paracrine signaling in mediating mechanically induced Ca²⁺ wave propagation in the human lens epithelium. This dual-pathway mechanism may be critical for coordinated cellular responses that support physiological processes such as ion homeostasis and transparency maintenance in the human lens.