Laboratoire Matière et Systèmes Complexes, Université Paris Diderot/CNRS UMR 7057, Sorbonne Paris Cité, 10 rue Alice Domon et Léonie Duquet, 75013, Paris, France.
Imagoseine Core Facility, Institut Jacques Monod, Université Paris Diderot/CNRS UMR7592, 15 rue Hélène Brion, 75013, Paris, France.
J Physiol. 2019 May;597(10):2785-2801. doi: 10.1113/JP277746. Epub 2019 Apr 21.
Neurogenic gut movements start after longitudinal smooth muscle differentiation in three species (mouse, zebrafish, chicken), and at E16 in the chicken embryo. The first activity of the chicken enteric nervous system is dominated by inhibitory neurons. The embryonic enteric nervous system electromechanically couples circular and longitudinal spontaneous myogenic contractions, thereby producing a new, rostro-caudally directed bolus transport pattern: the migrating motor complex. The response of the embryonic gut to mechanical stimulation evolves from a symmetric, myogenic response at E12, to a neurally mediated, polarized, descending inhibitory, 'law of the intestine'-like response at E16. High resolution, whole-mount 3D reconstructions are presented of the enteric nervous system of the chicken embryo at the neural-control stage E16 with the iDISCO+ tissue clarification technique.
Gut motility is a complex transport phenomenon involving smooth muscle, enteric neurons, glia and interstitial cells of Cajal. Because these different cells differentiate and become active at different times during embryo development, studying the ontogenesis of motility offers a unique opportunity to 'time-reverse-engineer' the peristaltic reflex. Working on chicken embryo intestinal explants in vitro, we found by spatio-temporal mapping and signal processing of diameter and position changes that motility follows a characteristic sequence of increasing complexity: (1) myogenic circular smooth muscle contractions from E6 to E12 that propagate as waves along the intestine, (2) overlapping and independent, myogenic, low-frequency, bulk longitudinal smooth muscle contractions around E14, and (3) tetrodotoxin-sensitive coupling of longitudinal and circular contractions by the enteric nervous system as from E16. Inhibition of nitric oxide synthase neurons shows that the coupling consists in nitric oxide-mediated relaxation of circular smooth muscle when the longitudinal muscle layer is contracted. This mechanosensitive coupling gives rise to a directional, cyclical, propagating bolus transport pattern: the migrating motor complex. We further reveal a transition to a polarized, descending, inhibitory reflex response to mechanical stimulation after neuronal activity sets in at E16. This asymmetric response is the elementary mechanism responsible for peristaltic transport. We finally present unique high-resolution 3D reconstructions of the chicken enteric nervous system at the neural-control stage based on confocal imaging of iDISCO+ clarified tissues. Our study shows that the enteric nervous system gives rise to new peristaltic transport patterns during development by coupling spontaneous circular and longitudinal smooth muscle contraction waves.
神经源性肠道运动始于三种物种（鼠、斑马鱼、鸡）的纵向平滑肌分化，在鸡胚的 E16 开始。鸡肠神经系统的第一个活动由抑制性神经元主导。胚胎肠神经系统通过电机械耦合环形和纵向自发肌源性收缩，从而产生新的、头足向的食团传输模式：移行性运动复合波。胚胎肠道对机械刺激的反应从 E12 时的对称、肌源性反应，发展为 E16 时的神经介导、极化、下行抑制、“肠道定律”样反应。使用 iDISCO+组织澄清技术，我们呈现了 E16 神经控制阶段鸡胚肠神经系统的高分辨率、整体式 3D 重建。
肠道运动是一种涉及平滑肌、肠神经元、神经胶质和 Cajal 间质细胞的复杂传输现象。由于这些不同的细胞在胚胎发育过程中不同的时间分化和活跃，研究运动的发生为“逆向工程”蠕动反射提供了一个独特的机会。我们通过对鸡胚肠外植体的时空映射和直径和位置变化的信号处理发现，运动遵循一个特征性的复杂性递增序列：（1）从 E6 到 E12 的肌源性环形平滑肌收缩，沿着肠道传播为波，（2）E14 周围重叠且独立的、肌源性、低频、块状纵向平滑肌收缩，（3）从 E16 开始，肠神经系统通过纵向和环形收缩的河豚毒素敏感性耦合。一氧化氮合酶神经元的抑制表明，这种耦合由纵向肌层收缩时环形平滑肌的一氧化氮介导的松弛组成。这种机械敏感的耦合产生了一个方向、循环、传播的食团传输模式：移行性运动复合波。我们进一步揭示，在 E16 神经元活动开始后，对机械刺激的反应过渡到极化、下行、抑制反射。这种不对称反应是负责蠕动传输的基本机制。最后，我们根据 iDISCO+澄清组织的共聚焦成像，呈现了基于神经控制阶段的鸡肠神经系统的独特高分辨率 3D 重建。我们的研究表明，肠神经系统通过耦合自发的环形和纵向平滑肌收缩波，在发育过程中产生新的蠕动传输模式。
