Feeding Formula Eliminates the Necessity of Bacterial Dysbiosis and Induces Inflammation and Injury in the Paneth Cell Disruption Murine NEC Model in an Osmolality-Dependent Manner.

Necrotizing enterocolitis (NEC) remains a significant cause of morbidity and mortality in preterm infants. Formula feeding is a risk factor for NEC and osmolality, which is increased by the fortification that is required for adequate growth of the infant, has been suggested as a potential cause. Our laboratory has shown that Paneth cell disruption followed by induction of dysbiosis can induce NEC-like pathology in the absence of feeds. We hypothesized adding formula feeds to the model would exacerbate intestinal injury and inflammation in an osmolality-dependent manner. NEC-like injury was induced in 14-16 day-old C57Bl/6J mice by Paneth cell disruption with dithizone or diphtheria toxin, followed by feeding rodent milk substitute with varying osmolality (250-1491 mOsm/kg H2O). Animal weight, serum cytokines and osmolality, small intestinal injury, and cecal microbial composition were quantified. Paneth cell-disrupted mice fed formula had significant NEC scores compared to controls and no longer required induction of bacterial dysbiosis. Significant increases in serum inflammatory markers, small intestinal damage, and overall mortality were osmolality-dependent and not related to microbial changes. Overall, formula feeding in combination with Paneth cell disruption induced NEC-like injury in an osmolality-dependent manner, emphasizing the importance of vigilance in designing preterm infant feeds.

Loss of murine Paneth cell function alters the immature intestinal microbiome and mimics changes seen in neonatal necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) remains the leading cause of gastrointestinal morbidity and mortality in premature infants. Human and animal studies suggest a role for Paneth cells in NEC pathogenesis. Paneth cells play critical roles in host-microbial interactions and epithelial homeostasis. The ramifications of eliminating Paneth cell function on the immature host-microbial axis remains incomplete. Paneth cell function was depleted in the immature murine intestine using chemical and genetic models, which resulted in intestinal injury consistent with NEC. Paneth cell depletion was confirmed using histology, electron microscopy, flow cytometry, and real time RT-PCR. Cecal samples were analyzed at various time points to determine the effects of Paneth cell depletion with and without Klebsiella gavage on the microbiome. Deficient Paneth cell function induced significant compositional changes in the cecal microbiome with a significant increase in Enterobacteriacae species. Further, the bloom of Enterobacteriaceae species that occurs is phenotypically similar to what is seen in human NEC. This further strengthens our understanding of the importance of Paneth cells to intestinal homeostasis in the immature intestine.

Development of the Neonatal Intestinal Microbiome and Its Association With Necrotizing Enterocolitis.

PURPOSE: Neonatal necrotizing enterocolitis (NEC) remains the most devastating gastrointestinal disease for premature infants. In the United States alone, NEC affects >4000 premature infants yearly, has a mortality rate of nearly 33%, and costs the health care system >$1 billion annually. Although NEC has been actively researched for several decades, its pathophysiology remains elusive. One potential mechanism suggests that disruption of the normal neonatal intestinal bacterial flora induces a proinflammatory state, allowing translocation of pathogens across the intestinal epithelia. Disruption of the normal intestinal flora (dysbiosis) is associated with many human diseases. Thus, it is a reasonable hypothesis that dysbiosis may play an important role in the development of NEC. This hypothesis is supported by evidence that probiotic use in premature infants can prevent the development of NEC. Although the role of probiotics and NEC is covered in other reviews, this review instead focuses on normal bacterial colonization in both term and preterm infants and on the association of dysbiosis and the development of NEC. METHODS: PubMed was queried with the use of the following key search terms: NEC, neonatal microbiome, fetal microbiome, maternal microbiome, neonatal dysbiosis, and microbiome ontogeny. Relevant literature was reviewed and selected for inclusion in accordance with the objectives of the article according to the authors' discretion. Articles that made key salient points in review articles were further pulled from PubMed. FINDINGS: Although the onset of NEC is thought to involve bacteria, the mechanisms behind their involvement remain unclear. Research to date has failed to identify a single causative organism, and current theories and data now indicate that a disruption of the host intestinal flora is associated with the onset of disease. Recent reports have found that a bloom of Proteobacteria, specifically Enterobacteriacae species, occurs just before the diagnosis of NEC. Whether this is a causative event or merely a marker of intestinal disease is still unclear. IMPLICATIONS: Because of the complexity of these interactions, it is vital that we continue to investigate the host-bacterial axis in the developing intestine in both humans and in animal models.