Distribution Map of Peristaltic Waves in the Chicken Embryonic Gut Reveals Importance of Enteric Nervous System and Inter-Region Cross Talks Along the Gut Axis

Abstract

Gut peristaltic movements recognized as the wave-like propagation of a local contraction are crucial for effective transportation and digestion/absorption of ingested materials. Although the physiology of gut peristalsis has been well studied in adults, it remains largely unexplored how the cellular functions underlying these coordinated tissue movements are established along the rostral-caudal gut axis during development. The chicken embryonic gut serves as an excellent experimental model for elucidating the endogenous potential and regulation of these cells since peristalsis occurs even though no ingested material is present in the moving gut. By combining video-recordings and kymography, we provide a spatial map of peristaltic movements along the entire gut posterior to the duodenum: midgut (jejunum and ileum), hindgut, caecum, and cloaca. Since the majority of waves propagate bidirectionally at least until embryonic day 12 (E12), the sites of origin of peristaltic waves (OPWs) can unambiguously be detected in the kymograph. The spatial distribution map of OPWs has revealed that OPWs become progressively confined to specific regions/zones along the gut axis during development by E12. Ablating the enteric nervous system (ENS) or blocking its activity by tetrodotoxin perturb the distribution patterns of OPWs along the gut tract. These manipulations have also resulted in a failure of transportation of inter-luminally injected ink. Finally, we have discovered a functional coupling of the endpoint of hindgut with the cloaca. When surgically separated, the cloaca ceases its acute contractions that would normally occur concomitantly with the peristaltic rhythm of the hindgut. Our findings shed light on the intrinsic regulations of gut peristalsis, including unprecedented ENS contribution and inter-region cross talk along the gut axis.

Commentary: Localization of contractile wave nucleation sites as an emerging phenomenon of stochastic myogenic gut motility

“…At E12 ( cpm), nucleation sites concentrated along distinct positions along the length of the gut ( Figures 1C,D ). The spatiotemporal maps and the spontaneous emergence of OPWs strongly resemble the results of Shikaya et al (2022) The positions of the OPWs slowly drifted with time and could even disappear ( Figure 1C ). A similar continuous drift occurring both before and after the administration of tetrodotoxin was reported in Figure 5B by Shikaya et al (2022) —because the drift is continuous I do not think it is induced by tetrodotoxin but rather reflects the natural time evolution of a purely myogenic system.…”

“…In their recent article, Shikaya et al (2022) reported on the existence of preferential sites of nucleation of contractile waves along the chicken embryonic day 12 midgut, termed sites of “origin of peristaltic waves” (OPW). Histological analysis by the authors did not reveal any peculiarities of these sites compared to other locations along the gut.…”

“…Localized above-threshold depolarization of the smooth muscle leads to the nucleation of two contractile waves propagating symmetrically away from the point of depolarization, at a constant speed of about 30 μm/s at E8-E12 ( Chevalier et al, 2020 ; Shikaya et al, 2022 ), and that further depolarizes the tissue in its wake. Smooth muscle can only spontaneously depolarize again after a certain refractory period, which is typically on the order of 10–60 s for chicken embryonic intestinal smooth muscle.…”

“…The simulation was run over 500 time steps, and parameters p and τ were explored to reproduce the experimentally observed frequencies of contractiles waves of 0.6 cpm (cycles per minute) at E8 ( Chevalier et al, 2017 ; Shikaya et al, 2022 ) and of 1.4 cpm at E12 ( Chevalier et al, 2020 ; Shikaya et al, 2022 ). At E8 ( cpm), I observed random distribution of nucleation sites along the length of the gut for all values of τ < 60 s ( Figures 1A,B ), in agreement with the findings of Shikaya et al (2022) at this stage. The wave pattern is reminiscent of that of the pigmentation of some seashells (inset), that occurs by a similar traveling wave mechanism ( Meinhardt and Klingler, 1987 ).…”

Newly raised anti-c-Kit antibody detects interstitial cells of Cajal in the gut of chicken embryos

“…The chicken embryonic gut, which is highly gene-manipulable in/ex vivo , has recently emerged as a powerful model for elucidating the endogenous potential and regulation of peristalsis-related cells including ICCs, because peristalsis occurs even though no ingested material is present in the moving gut (Chevalier et al, 2017). In addition, the distribution map of peristaltic movements along the entire gut axis is available (Shikaya et al, 2022). Previous studies using in situ hybridization with c-Kit showed that the composition of ICCs in the chicken gut largely parallel that in mammals (Chevalier et al, 2020; Lecoin et al, 1996; Yang et al, 2012).…”