An Optogenetics-based Approach to Regulate Colonic Contractions by Modulating the Activity of the Interstitial Cells of Cajal in Mice

Background/Aims The interstitial cells of Cajal (ICC) are pacemaker cells in the gastrointestinal (GI) tract. We examined whether the activity of ICC could be stimulated to control colonic contractions. An optogenetics-based mouse model in which the light-sensitive protein channelrhodopsin-2 (ChR2) was expressed was used to accomplish cell specific, direct stimulation of ICC.Methods An inducible site-specific Cre-loxP recombination system was used to generate KitCreERT2/+;ROSAChR2(H134R)/tdTo mat o/+ mice in which ChR2(H134R), a variant of ChR2, was genetically expressed in ICC after tamoxifen administration. Genotyping and immunofluorescence analysis were performed to confirm gene fusion and expression. Isometric force recordings were performed to measure changes in contractions in the colonic muscle strips.Results ChR2 was specifically expressed in Kit-labeled ICC. The isometric force recordings showed that the contractions of the colonic muscle strips changed under 470 nm blue light. Light stimulation evoked premature low-frequency and high amplitude (LFHA) contractions and enhanced the frequency of the LFHA contractions. The light-evoked contractions were blocked by T16Ainh-A01, an antagonist of anoctamin 1 channels that are expressed selectively in ICC in colonic muscles.Conclusions Our study demonstrates a potentially feasible approach to stimulate the activity of ICC by optogenetics. The colonic motor patterns of muscle strips, especially LFHA contractions, can be regulated by 470 nm light via ChR2, which is expressed in ICC. (J Neurogastroenterol Motil 2023;29:388-399)

Automated summary

The activity of interstitial cells of Cajal (ICC) in the gastrointestinal tract was stimulated using optogenetics-based methods. The study utilized a genetically modified mouse model expressing the light-sensitive protein channelrhodopsin-2 (ChR2) in ICC, which allowed for specific and direct stimulation of the cells. The results demonstrated that 470 nm blue light stimulation could induce low-frequency high-amplitude contractions in the colonic muscle strips, and the frequency of these contractions could be enhanced. This stimulation effect was blocked by an antagonist specific to ICC-expressed channels. This study provides evidence for the feasibility of stimulating ICC activity through optogenetics.