A microfluidic chip recapitulating the human neurovascular unit with a functional blood–brain barrier for modeling gut–brain interactions

The blood–brain barrier (BBB) is essential for central nervous system homeostasis, but most current in vitro models lack structural and functional fidelity. We developed a physiologically relevant human neurovascular unit microfluidic chip (hNVU-on-a-chip) incorporating brain microvascular endothelial cells, astrocytes, and microglia to reconstruct a biomimetic BBB microenvironment. Barrier function was confirmed by low apparent permeability (P_app) and active P-glycoprotein (P-gp) efflux, with performance superior to Transwell models. Transcriptomic profiling revealed endothelial maturation with upregulated barrier and transport genes and downregulated proliferative pathways. Introducing gut microbial metabolites altered brain-side neurotransmitter metabolism, elevating biogenic amines and reducing precursors, consistent with enhanced turnover. Together, the hNVU-on-a-chip recapitulates BBB architecture and function, and provides a robust platform to investigate gut–brain axis interactions.