Comparing a Conventional 2D with a 3D Bioelectronic Platform for Studying the Mechanism of Diet on Host-Microbiome Interactions in the Human Gut

Increasing evidence demonstrates that the gut microbiome plays a significant role in human health and disease. Moreover, a strong association of the gut microbiome with the aetiology of non-communicable diseases such as type II diabetes or inflammatory bowel disease (IBD) exists.¹ Metabolites, synthesized by gut bacteria from the diet, are key for inducing beneficial health effects within host-microbiome interactions. The most prominent metabolites are short-chain fatty acids (SCFA), which are mainly acetate, propionate, and butyrate, predominantly produced by fermentation of dietary-derived fibre by bacteria like <i>F. prausnitzii.</i>² SCFAs have been shown to induce several favourable health effects in the mechanism of diabetes or obesity, but are also able to improve the functionality of the gut barrier in IBD. These effects induced by SCFAs are suggested to be mediated via activation of G-Protein coupled receptors (GPCR), especially the candidate GPR43, however, full mechanisms are not well understood yet.³<br/>The most obvious reasons for that are the limited possibility to study non-invasively host-microbiome interactions in humans as well as a lack of access to human biopsies. Conventional 2D in vitro models are valuable tools for high-throughput screening and animal studies allow to get insights into cause-effect relationships, however, a translation to human physiology is still challenging.⁴ Thus, with the recently developed electronic 3D model of the human gut, we are aiming to generate predictions on host-microbiome interactions that are closer to the real human <i>in vivo</i> situation. The use of a soft and tissue-like electroactive scaffold (PEDOT: PSS) as a platform for cell hosting, allows to monitor in real-time non-invasively changes of the electrical resistance as a readout parameter of the gut barrier functionality (barrier integrity).⁵ Co-culturing of cell lines promotes cell-cell communications and thereby improves the expression of native cell receptor profiles as well as cell signalling processes.⁶ In addition, the integration of a bioelectronic sensor enables detection of the overall cell activity after activation of GPR43 by SCFAs instead of single pathway analysis, commonly done in conventional receptor assays.⁷ Currently, the effects of SCFAs on markers of the gut barrier integrity are compared in (<i>i</i>) traditional 2D Transwell inserts versus the 3D bioelectronic model of the human gut. Moreover, for getting a better understanding of the bioelectrical signature of the 3D platform, (<i>ii</i>) electrical readouts are deconvoluted using conventional molecular biological techniques like RT-qPCR.<br/><br/><u>References:</u><br/>[1] Finlay, B. B., CIFAR Humans, and Microbiome. "Are noncommunicable diseases communicable?." Science 367.6475 (2020): 250-251.<br/>[2] Parada Venegas, Daniela, et al. "Short-chain fatty acids (SCFAs)-mediated gut epithelial and immune regulation and its relevance for inflammatory bowel diseases." Frontiers in immunology (2019): 277.<br/>[3] Zhang, Zhilin, et al. "Regulatory role of short-chain fatty acids in inflammatory bowel disease." Cell Communication and Signaling 20.1 (2022): 1-10.<br/>[4] Leenaars, Cathalijn HC, et al. "Animal to human translation: A systematic scoping review of reported concordance rates." Journal of translational medicine 17.1 (2019): 1-22.<br/>[5] Pitsalidis, Charalampos, et al. "Organic bioelectronics for in vitro systems." Chemical Reviews (2021).<br/>[6] Edmondson, Rasheena, et al. "Three-dimensional cell culture systems and their applications in drug discovery and cell-based biosensors." Assay and drug development technologies 12.4 (2014): 207-218.<br/>[7] Hillger, Julia M., et al. "Whole-cell biosensor for label-free detection of GPCR-mediated drug responses in personal cell lines." Biosensors and Bioelectronics 74 (2015): 233-242.