HUMAN GUT-BLOOD-BRAIN AXIS MICROPHYSIOLOGICAL SYSTEM FOR STUDIES OF GUT-NEUROPATHOGENESIS

Recent research suggests that the gut luminal environment, which includes commensal microbiota and metabolite components, can significantly influence behavior, emotions, and cognitive abilities in the brain, and even reverse certain conditions.The intricate bidirectional communication between the central nervous system (CNS) and the intestine occurs through the Gut-Brain Axis (GBA), wherein the circulatory system serves as one possible route for this exchange of signals.Despite mounting evidence, a substantial knowledge gap persists in understanding the precise mechanisms underlying the communication between the gut and brain in both health and disease, primarily due to the absence of relevant direct models.Herein, we present a 3D human gut-blood-brain axis-on-achip (GBBA) that integrates a gut lumen villus structure, a tubular blood vessel and mini-brain tissue to capture the physio-pathological properties of gut and brain features.First, we demonstrated the physiological properties by illustrating the formation of a 3D structure, encompassing a villus in the tubular gut epithelium, a 3D tubular blood vessel derived from human embryonic stem cells (hES), and a 3D neuron and astrocytes environment differentiated from neural progenitor cell (NPC).This structure manifested a functional tight barrier within both the gut epithelium and the brain vascular-like structure, evidenced by the expression of zonula occludens-1 (ZO-1), occludin (OCLN) along with the subsequent expression of intestinal villus on gut epithelium; and the presence of ZO-1, OCLN effectively prevented the penetration of leakage dyes (FITC-dextran: M.wt.3-70 kDa), underscoring the barrier properties of the 3D brain vascular-like structure.In addition, we emphasized the interaction of these barriers to astrocytes and neurons in a 3D-like brain tissue microenvironment.Secondly, we simulated gut infection disorder by single injection of the high dose lipopolysaccharides (LPS: 1 M) in the gut epithelium.In this environment, we observed the alteration of the gut crypt-villus structure by showing the reduction of villi expression (VIL1), OCLN, allows the infiltration of toxins into the blood vessel, subsequently leading to the breakdown of the tight barrier on brain vascular-like structures by showing the leakage of FITCdextran, indicating the entry of toxic factors into brain tissue.This is followed by the activation of A1 astrocytes phenotype and a reduction in synaptic expression in the brain tissue environment.Finally, we modeled synuclein (-syn) propagation associated with Parkinson's disease through a single injection of preformed fibrils (PFFs: 1 M) in the brain tissue region containing neurons and astrocytes.We observed the absorption of PFFs by astrocytes, prompting the generation of phosphorylated -syn in neurons.This protein then migrated to the brain endothelium layer and was subsequently transported into the gut epithelium via extracellular vesicle (EV) mechanisms.Furthermore, we observed a correlation between this formulation and increased inflammation within the brain region, results in induced damage to capillary structures, as evidenced by reduced levels of ZO-1 and increased blood-brain barrier permeability.In summary, we contend that our gut-blood-brain axis-on-a-chip closely mimics the human gut-brain architecture, and our model may facilitate the study of the mechanisms of gut-neuropathogenesis, and the development of therapeutic agents for neurodegenerative disease.