There is significant communication and interdependence among the gut, the microbiome, and the brain during development. Diseases, such as necrotizing enterocolitis (NEC), highlight how injury to the immature gastrointestinal tract leads to long-term neurological consequences, due to vulnerabilities of the brain in the early stages of life. A better understanding of the developing gut–microbiota–brain axis is needed to both prevent and treat the devastating consequences of these disease processes. The gut–microbiota–brain axis is a bidirectional communication pathway that includes metabolic, nervous, endocrine, and immune components. In this review, we discuss gut development, microbiome colonization and maturation, and the interactions that influence neurodevelopment in the context of NEC. We describe the components of the gut–brain axis and how the microbiome is an integral member of this relationship. Finally, we explore how derangements within the microbiome and gut–microbiota–brain axis affect the normal development and function of the other systems and long-term neurodevelopmental consequences for patients.

Necrotizing enterocolitis (NEC) is a significant cause of morbidity and mortality for preterm infants in the neonatal intensive care unit. From the first surgical approaches for NEC in the 1970s and the development of Bell’s staging criteria, there has been a continuous medical and scientific journey towards understanding the pathophysiology, clinical progression, and treatment possibilities for this devastating disease. Basic science research has played a crucial role in understanding the pathogenesis of NEC. In vivo NEC models, which include rodents (mice, rats) and pigs, and in vitro NEC models, which utilize intestinal cell lines and organoids, have identified critical disease biomarkers, pathways in NEC pathogenesis, and novel therapeutic targets. These potential therapies have been brought into clinical trials to improve treatment options for infants with NEC. This review will provide a comprehensive assessment of research conducted over the last decade, leading to a deeper understanding of the disease’s development and progression through the use of innovative models, the identification of novel biomarkers, the development of new therapeutic approaches, and, finally, an overview of the latest clinical trials. We will conclude with a discussion of ongoing challenges and future research directions, highlighting the optimism and hope that these advancements bring to the field of neonatology and pediatric surgery. This review will serve as a reference and guide for future NEC research, with the ultimate goal of enhancing clinical outcomes and improving the quality of life for patients with NEC and their families.

Necrotizing enterocolitis (NEC) is an inflammatory gastrointestinal process that afflicts approximately 10% of preterm infants born in the United States each year, with a mortality rate of 30%. NEC severity is graded using Bell’s classification system, from stage I mild NEC to stage III severe NEC. Over half of NEC survivors present with neurodevelopmental impairment during adolescence, a long-term complication that is poorly understood. Although multiple animal models exist, none prospectively controls for NEC severity. We bridge this knowledge gap by characterizing a graded murine model of NEC and studying its relationship with neuroinflammation across a range of NEC severities. Postnatal day 3 (P3) C57BL/6 mice were fed a formula containing different concentrations (0% control, 0.25%, 1%, 2%, and 3%) of dextran sodium sulfate (DSS). P3 mice were fed every 3 hours for 72 hours. We collected data on weight gain and behavior (activity, response, body color) during feeding. At the end of feeding, we collected tissues (intestine, liver, plasma, brain) for immunohistochemistry, immunofluorescence, and cytokine and chemokine analysis. Throughout NEC induction, mice fed higher concentrations of DSS died sooner, lost weight faster, and became sick or lethargic earlier. Intestinal characteristics (dilation, color, friability) were worse in mice fed higher DSS concentrations. Histology revealed small intestinal disarray among all mice fed DSS, while higher DSS concentrations resulted in reduced small intestinal cellular proliferation and increased hepatic and systemic inflammation. In the brain, IL-2, G-CSF, and CXCL1 concentrations increased with higher DSS concentrations, and microglial branching in the hippocampus CA1 was significantly reduced in DSS-fed mice. In conclusion, we characterized a novel graded model of NEC that recapitulates the full range of NEC severities. We showed that mild NEC is sufficient to initiate neuroinflammation and microglia activation. This model will facilitate long-term studies on the neurodevelopmental effects of NEC.