Microbiota from Preterm Infants Who Develop Necrotizing Enterocolitis Drives the Neurodevelopment Impairment in a Humanized Mouse Model

Abstract

Necrotizing enterocolitis (NEC) is the leading basis for gastrointestinal morbidity and poses a significant risk for neurodevelopmental impairment (NDI) in preterm infants. Aberrant bacterial colonization preceding NEC contributes to the pathogenesis of NEC, and we have demonstrated that immature microbiota in preterm infants negatively impacts neurodevelopment and neurological outcomes. In this study, we tested the hypothesis that microbial communities before the onset of NEC drive NDI. Using our humanized gnotobiotic model in which human infant microbial samples were gavaged to pregnant germ-free C57BL/6J dams, we compared the effects of the microbiota from preterm infants who went on to develop NEC (MNEC) to the microbiota from healthy term infants (MTERM) on brain development and neurological outcomes in offspring mice. Immunohistochemical studies demonstrated that MNEC mice had significantly decreased occludin and ZO-1 expression compared to MTERM mice and increased ileal inflammation marked by the increased nuclear phospho-p65 of NFκB expression, revealing that microbial communities from patients who developed NEC had a negative effect on ileal barrier development and homeostasis. In open field and elevated plus maze tests, MNEC mice had worse mobility and were more anxious than MTERM mice. In cued fear conditioning tests, MNEC mice had worse contextual memory than MTERM mice. MRI revealed that MNEC mice had decreased myelination in major white and grey matter structures and lower fractional anisotropy values in white matter areas, demonstrating delayed brain maturation and organization. MNEC also altered the metabolic profiles, especially carnitine, phosphocholine, and bile acid analogs in the brain. Our data demonstrated numerous significant differences in gut maturity, brain metabolic profiles, brain maturation and organization, and behaviors between MTERM and MNEC mice. Our study suggests that the microbiome before the onset of NEC has negative impacts on brain development and neurological outcomes and can be a prospective target to improve long-term developmental outcomes.

Treatment of preterm brain injury via gut‐microbiota–metabolite–brain axis

“…NEC is characterized by dysbiosis (i.e., increased TLR4 activity) and is associated with a significant risk of neurodevelopmental disorders. 140 In a rat model of NEC, FMT before or after induction of NEC significantly alleviated inflammation, oxidative stress, and intestinal mucosal damage, suggesting that FMT may be a potential therapy for NEC. 141 Experimental FMT in neonatal preterm piglets reduced NEC risk, but the effect was donor‐specific.…”

Potential Epigenetic Effects of Human Milk on Infants’ Neurodevelopment

“…There is evidence that the gut microbiome during early life contributes to the establishment of epigenetic modifications and it is also associated with brain development and neurodevelopment [ 113 , 114 , 115 ]. The colonization of the infant’s intestine after birth, influenced by maternal flora, delivery method, early skin-to-skin contact, and neonatal diet, results in specific epigenetic patterns that can influence the protective function of the gut mucosa against future insults [ 116 ].…”

“…Furthermore, the gut microorganisms secrete molecules which can reach the brain via the circulatory system after absorption and affect the brain’s development ( Figure 3 ), especially during sensitive periods (gut–brain axis) [ 117 ]. Interestingly, in a recent study in a humanized mouse model, the aberrant gut microbiome of preterm infants had negative effects on brain organization and maturation, and brain metabolism, as well as on behavior and memory [ 114 ]. The connection between the gut microbiome and brain function has led to investigations into its potential role in neurobehavioral disorders, such as autism spectrum disorder (ASD), anxiety and attention-deficit-hyperactivity disorder [ 118 ].…”

The neonatal gut microbiota: a role in the encephalopathy of prematurity

“…However, this limits causal inference: the relationships observed could reflect a separate process causally linked to the development of both the gut microbiome and brain structure. Nevertheless, preclinical data shows that colonisation of germ-free mice with preterm microbial communities associates with poor growth, systemic and neuroinflammation, delayed neuronal development and myelination, disrupted brain microstructural connectivity, and behavioural deficits 73,74 , supporting a causal relationship. Future studies with longitudinal microbiome sampling over the NICU period are needed to clarify the critical time window for the strongest influence of the gut microbiome on brain microstructural development.…”