Girardi Gregory, Zumpano Danielle, Raybould Helen, Seker Erkin
Department of Biomedical Engineering, University of California - Davis, Davis, CA, 95616, USA.
Department of Anatomy, Physiology, and Cell Biology, University of California - Davis, Davis, CA, 95616, USA.
Bioelectron Med. 2024 Feb 21;10(1):3. doi: 10.1186/s42234-023-00140-3.
Vagal afferent neurons represent the key neurosensory branch of the gut-brain axis, which describes the bidirectional communication between the gastrointestinal system and the brain. These neurons are important for detecting and relaying sensory information from the periphery to the central nervous system to modulate feeding behavior, metabolism, and inflammation. Confounding variables complicate the process of isolating the role of the vagal afferents in mediating these physiological processes. Therefore, we developed a microfluidic model of the sensory branch of the gut-brain axis. We show that this microfluidic model successfully compartmentalizes the cell body and neurite terminals of the neurons, thereby simulates the anatomical layout of these neurons to more accurately study physiologically-relevant processes.
We implemented a primary rat vagal afferent neuron culture into a microfluidic platform consisting of two concentric chambers interconnected with radial microchannels. The microfluidic platform separated cell bodies from neurite terminals of vagal afferent neurons. We then introduced physiologically-relevant gastrointestinal effector molecules at the nerve terminals and assessed their retrograde transport along the neurite or capacity to elicit an electrophysiological response using live cell calcium imaging.
The angle of microchannel outlets dictated the probability of neurites growing into a chamber versus tracking along chamber walls. When the neurite terminals were exposed to fluorescently-labeled cholera toxin subunit B, the proteins were taken up and retrogradely transported along the neurites over the course of 24 h. Additionally, mechanical perturbation (e.g., rinsing) of the neurite terminals significantly increased intracellular calcium concentration in the distal soma. Finally, membrane-displayed receptor for capsaicin was expressed and trafficked along newly projected neurites, as revealed by confocal microscopy.
In this work, we developed a microfluidic device that can recapitulate the anatomical layout of vagal afferent neurons in vitro. We demonstrated two physiologically-relevant applications of the platforms: retrograde transport and electrophysiological response. We expect this tool to enable controlled studies on the role of vagal afferent neurons in the gut-brain axis.
迷走传入神经元是肠-脑轴的关键神经感觉分支，肠-脑轴描述了胃肠系统与大脑之间的双向通信。这些神经元对于检测并将感觉信息从外周传递至中枢神经系统以调节进食行为、新陈代谢和炎症反应非常重要。混杂变量使分离迷走传入神经在介导这些生理过程中的作用的过程变得复杂。因此，我们开发了一种肠-脑轴感觉分支的微流控模型。我们表明，这种微流控模型成功地分隔了神经元的细胞体和神经突末端，从而模拟了这些神经元的解剖布局，以便更准确地研究生理相关过程。
我们将原代大鼠迷走传入神经元培养物植入一个由两个通过径向微通道相互连接的同心腔室组成的微流控平台中。该微流控平台将迷走传入神经元的细胞体与神经突末端分隔开。然后，我们在神经末梢引入生理相关的胃肠效应分子，并使用活细胞钙成像评估它们沿神经突的逆行运输或引发电生理反应的能力。
微通道出口的角度决定了神经突生长到腔室中与沿腔室壁延伸的概率。当神经突末端暴露于荧光标记的霍乱毒素亚基B时，这些蛋白质在24小时内被摄取并沿神经突逆行运输。此外，神经突末端的机械扰动（例如冲洗）显著增加了远端细胞体中的细胞内钙浓度。最后，共聚焦显微镜显示，辣椒素的膜展示受体在新长出的神经突上表达并运输。
在这项工作中，我们开发了一种能够在体外重现迷走传入神经元解剖布局的微流控装置。我们展示了该平台的两种生理相关应用：逆行运输和电生理反应。我们期望这个工具能够对迷走传入神经元在肠-脑轴中的作用进行可控研究。
