Direct Stimulation of Gastric Smooth Muscle Cells via G_q Proteins With Light

Optogenetics is a cutting-edge approach that can enable direct stimulation of gastric smooth muscle cells (SMC) by combining cell-specific overexpression of light-sensitive proteins with light stimulation. We previously demonstrated that direct optogenetic stimulation of gastric SMC via depolarization can restore contractility and food propulsion and could become a new treatment strategy for gastroparesis. The human receptor Neuropsin (hOPN5) enables activation of G_q signaling with UV light. Herein, we explore this new strategy for direct optogenetic stimulation of gastric SMC.

We used a transgenic mouse model expressing hOPN5 in fusion with eYFP. Antral longitudinal smooth muscle strips were used for isometric force measurements and whole stomachs for intragastric pressure measurements, comparing light stimulation to other stimuli. Adeno-associated virus (AAV) serotypes were screened for efficiency in transducing cultured gastric SMC, and transduced cells were tested by Ca²⁺ imaging.

hOPN5 expression was restricted to and found in ~1/3 of SMC in the stomach. UV light induced isometric force and increased intragastric pressure only in transgenic mice similarly to electrical field stimulation and reached approximately 1/3 of the force induced by global depolarization and muscarinic receptor activation. Importantly, optical stimulation remained effective in an ex vivo gastroparesis model. AAV 2.5 was by far the most effective serotype for SMC transduction, and UV light triggered Ca²⁺ transients in SMC expressing hOPN5.

hOPN5 is a new and effective tool to directly stimulate gastric SMC to control contractility with light. Thus, it is an additional and complementary approach to light-induced membrane depolarization to restore gastric motility.