Ex vivo and miniaturized in vitro to study microbiota-gut-brain axis.

The microbiota-gut-brain axis involves complex bidirectional communication through neural, immune, and endocrine pathways. Microbial metabolites, such as short-chain fatty acids, influence gut motility and brain function by interacting with gut receptors and modulating hormone release. Additionally, microbial components such as lipopolysaccharides and cytokines can cross the gut epithelium and the blood-brain barrier, impacting immune responses and cognitive function. Ex vivo models, which preserve gut tissue and neural segments, offer insight into localized gut-brain communication by allowing for detailed study of nerve excitability in response to microbial signals, but they are limited in systemic complexity. Miniaturized in vitro models, including organ-on-chip platforms, enable precise control of the cellular environment and simulate complex microbiota-host interactions. These systems allow for the study of microbial metabolites, immune responses, and neuronal activity, providing valuable insights into gut-brain communication. Despite challenges such as replicating long-term biological processes and integrating immune and hormonal systems, advancements in bioengineered platforms are enhancing the physiological relevance of these models, offering new opportunities for understanding the mechanisms of the microbiota-gut-brain axis. This review aims to describe the ex vivo and miniaturized in vitro models which are used to mimic the in vivo conditions and facilitate more precise studies of gut brain communication.