Role of asphyxia and feeding in a neonatal rat model of necrotizing enterocolitis

Microbiota regulates neonatal disease tolerance to virus-evoked necrotizing enterocolitis by shaping the STAT1-NLRC5 axis in the intestinal epithelium

Microbiota and feeding modes influence the susceptibility of premature newborns to necrotizing enterocolitis (NEC) through mechanisms that remain unknown. Here, we show that microbiota colonization facilitated by breastmilk feeding promotes NOD-like receptor family CARD domain containing 5 (Nlrc5) gene expression in mouse intestinal epithelial cells (IECs). Notably, inducible knockout of the Nlrc5 gene in IECs predisposes neonatal mice to NEC-like injury in the small intestine upon viral inflammation in an NK1.1+ cell-dependent manner. By contrast, formula feeding enhances neonatal gut colonization with environment-derived tilivalline-producing Klebsiella spp. Remarkably, tilivalline disrupts microbiota-activated STAT1 signaling that controls Nlrc5 gene expression in IECs through a PPAR-γ-mediated mechanism. Consequently, this dysregulation hinders the resistance of neonatal intestinal epithelium to self-NK1.1+ cell cytotoxicity upon virus infection/colonization, promoting NEC development. Together, we discover the underappreciated role of intestinal microbiota colonization in shaping a disease tolerance program to viral inflammation and elucidate the mechanisms impacting NEC development in neonates.

Immunological aspects of necrotizing enterocolitis models: a review

Necrotizing enterocolitis (NEC) is one of the most devasting diseases affecting preterm neonates. However, despite a lot of research, NEC's pathogenesis remains unclear. It is known that the pathogenesis is a multifactorial process, including (1) a pathological microbiome with abnormal bacterial colonization, (2) an immature immune system, (3) enteral feeding, (3) an impairment of microcirculation, and (4) possibly ischemia-reperfusion damage to the intestine. Overall, the immaturity of the mucosal barrier and the increased expression of Toll-like receptor 4 (TLR4) within the intestinal epithelium result in an intestinal hyperinflammation reaction. Concurrently, a deficiency in counter-regulatory mediators can be seen. The sum of these processes can ultimately result in intestinal necrosis leading to very high mortality rates of the affected neonates. In the last decade no substantial advances in the treatment of NEC have been made. Thus, NEC animal models as well as in vitro models have been employed to better understand NEC's pathogenesis on a cellular and molecular level. This review will highlight the different models currently in use to study immunological aspects of NEC.

Neuropilin-1high monocytes protect against neonatal inflammation

Neonates are susceptible to inflammatory disorders such as necrotizing enterocolitis (NEC) due to their immature immune system. The timely appearance of regulatory immune cells in early life contributes to the control of inflammation in neonates, yet the underlying mechanisms of which remain poorly understood. In this study, we identified a subset of neonatal monocytes characterized by high levels of neuropilin-1 (Nrp1), termed Nrp1high monocytes. Compared with their Nrp1low counterparts, Nrp1high monocytes displayed potent immunosuppressive activity. Nrp1 deficiency in myeloid cells aggravated the severity of NEC, whereas adoptive transfer of Nrp1high monocytes led to remission of NEC. Mechanistic studies showed that Nrp1, by binding to its ligand Sema4a, induced intracellular p38-MAPK/mTOR signaling and activated the transcription factor KLF4. KLF4 transactivated Nos2 and enhanced the production of nitric oxide (NO), a key mediator of immunosuppression in monocytes. These findings reveal an important immunosuppressive axis in neonatal monocytes and provide a potential therapeutic strategy for treating inflammatory disorders in neonates.

A graded neonatal mouse model of necrotizing enterocolitis demonstrates that mild enterocolitis is sufficient to activate microglia and increase cerebral cytokine expression

Background

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 but can occur even after mild NEC. Although multiple animal models exist, none allow the experimenter to control nor represent the gradient of symptom severities seen in NEC patients. We bridge this knowledge gap by developing a graded murine model of NEC and studying its relationship with neuroinflammation across a range of NEC severities.

Methods

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 the experiment, we collected tissues (intestine, liver, plasma, brain) for immunohistochemistry, immunofluorescence, and cytokine and chemokine analysis.

Results

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 with higher DSS concentrations. Histology revealed small intestinal disarray among mice fed all DSS concentrations, 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. Although the number of neurons and microglia in the CA1 hippocampal region did not differ, microglial branching was significantly reduced in DSS-fed mice.

Conclusion

We characterize a novel graded model of NEC that recapitulates the full range of NEC severities. We show that mild NEC is sufficient to initiate neuroinflammation and microglia activation. This model will facilitate studies on the neurodevelopmental effects of NEC.

Extracellular Nicotinamide Phosphoribosyltransferase Is a Therapeutic Target in Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of prematurity. Postulated mechanisms leading to inflammatory necrosis of the ileum and colon include activation of the pathogen recognition receptor Toll-like receptor 4 (TLR4) and decreased levels of transforming growth factor beta (TGFβ). Extracellular nicotinamide phosphoribosyltransferase (eNAMPT), a novel damage-associated molecular pattern (DAMP), is a TLR4 ligand and plays a role in a number of inflammatory disease processes. To test the hypothesis that eNAMPT is involved in NEC, an eNAMPT-neutralizing monoclonal antibody, ALT-100, was used in a well-established animal model of NEC. Preterm Sprague-Dawley pups delivered prematurely from timed-pregnant dams were exposed to hypoxia/hypothermia and randomized to control-foster mother dam-fed rats, injected IP with saline (vehicle) 48 h after delivery; control + mAB-foster dam-fed rats, injected IP with 10 µg of ALT-100 at 48 h post-delivery; NEC-orally gavaged, formula-fed rats injected with saline; and NEC + mAb-formula-fed rats, injected IP with 10 µg of ALT-100 at 48 h. The distal ileum was processed 96 h after C-section delivery for histological, biochemical, molecular, and RNA sequencing studies. Saline-treated NEC pups exhibited markedly increased fecal blood and histologic ileal damage compared to controls (q < 0.0001), and findings significantly reduced in ALT-100 mAb-treated NEC pups (q < 0.01). Real-time PCR in ileal tissues revealed increased NAMPT in NEC pups compared to pups that received the ALT-100 mAb (p < 0.01). Elevated serum levels of tumor necrosis factor alpha (TNFα), interleukin 6 (IL-6), interleukin-8 (IL-8), and NAMPT were observed in NEC pups compared to NEC + mAb pups (p < 0.01). Finally, RNA-Seq confirmed dysregulated TGFβ and TLR4 signaling pathways in NEC pups that were attenuated by ALT-100 mAb treatment. These data strongly support the involvement of eNAMPT in NEC pathobiology and eNAMPT neutralization as a strategy to address the unmet need for NEC therapeutics.

Evaluation of the protective and therapeutic effects of extra virgin olive oil rich in phenol in experimental model of neonatal necrotizing enterocolitis by clinical disease score, ınflammation, apoptosis, and oxidative stress markers

BACKGROUND AND AIM

Necrotizing Enterocolitis (NEC) is an inflammation-associated ischemic necrosis of the intestine. To investigate the effects of extra virgin olive oil (EVOO) on inflammation, oxidative stress, apoptosis, and histological changes in NEC-induced newborn rats.

MATERIALS AND METHODS

24 rats were randomly divided into three groups: control, NEC and NEC + EVOO. NEC induction was performed using hypoxia-hyperoxia, formula feeding, and cold stress. The NEC + EVOO group received 2 ml/kg EVOO with high phenolic content by gavage twice a day for 3 days. 3 cm of bowel including terminal ileum, cecum, and proximal colon was excised.

RESULTS

Weight gain and clinical disease scores were significantly higher in the NEC + EVOO group than in the NEC group (p < 0.001). EVOO treatment caused significant decreases in IL1β, IL6 levels (p = 0.016, p = 0.029 respectively) and EGF, MDA levels (p = 0.032, p = 0.013 respectively) compared to NEC group. Significant decreases were observed in IL6 gene expression in the NEC + EVOO group compared to the NEC group (p = 0.002). In the group NEC + EVOO, the number of Caspase-3 positive cells was found to be significantly reduced (p < 0.001) and histopathological examination revealed minimal changes and significantly lower histopathological scores (p < 0.001).

CONCLUSION

Phenol-rich EVOO prevents intestinal damage caused by NEC by inhibiting inflammation, oxidative stress, apoptosis.

Paneth cell ontogeny in term and preterm ovine models

Introduction

Paneth cells are critically important to intestinal health, including protecting intestinal stem cells, shaping the intestinal microbiome, and regulating host immunity. Understanding Paneth cell biology in the immature intestine is often modeled in rodents with little information in larger mammals such as sheep. Previous studies have only established the distribution pattern of Paneth cells in healthy adult sheep. Our study aimed to examine the ontogeny, quantification, and localization of Paneth cells in fetal and newborn lambs at different gestational ages and with perinatal transient asphyxia. We hypothesized that ovine Paneth cell distribution at birth resembles the pattern seen in humans (highest concentrations in the ileum) and that ovine Paneth cell density is gestation-dependent.

Methods

Intestinal samples were obtained from 126-127 (preterm, with and without perinatal transient asphyxia) and 140-141 (term) days gestation sheep. Samples were quantified per crypt in at least 100 crypts per animal and confirmed as Paneth cells through in immunohistochemistry.

Results

Paneth cells had significantly higher density in the ileum compared to the jejunum and were absent in the colon.

Discussion

Exposure to perinatal transient asphyxia acutely decreased Paneth cell numbers. These novel data support the possibility of utilizing ovine models for understanding Paneth cell biology in the fetus and neonate.

Clostridium scindens exacerbates experimental necrotizing enterocolitis via upregulation of the apical sodium-dependent bile acid transporter

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in premature infants. Evidence indicates that bile acid homeostasis is disrupted during NEC: ileal bile acid levels are elevated in animals with experimental NEC, as is expression of the apical sodium-dependent bile acid transporter (Asbt). In addition, bile acids, which are synthesized in the liver, are extensively modified by the gut microbiome, including via the conversion of primary bile acids to more cytotoxic secondary forms. We hypothesized that the addition of bile acid-modifying bacteria would increase susceptibility to NEC in a neonatal rat model of the disease. The secondary bile acid-producing species Clostridium scindens exacerbated both incidence and severity of NEC. C. scindens upregulated the bile acid transporter Asbt and increased levels of intraenterocyte bile acids. Treatment with C. scindens also altered bile acid profiles and increased hydrophobicity of the ileal intracellular bile acid pool. The ability of C. scindens to enhance NEC requires bile acids, as pharmacological sequestration of ileal bile acids protects animals from developing disease. These findings indicate that bile acid-modifying bacteria can contribute to NEC pathology and provide additional evidence for the role of bile acids in the pathophysiology of experimental NEC.NEW & NOTEWORTHY Necrotizing enterocolitis (NEC), a life-threatening gastrointestinal emergency in premature infants, is characterized by dysregulation of bile acid homeostasis. We demonstrate that administering the secondary bile acid-producing bacterium Clostridium scindens enhances NEC in a neonatal rat model of the disease. C. scindens-enhanced NEC is dependent on bile acids and driven by upregulation of the ileal bile acid transporter Asbt. This is the first report of bile acid-modifying bacteria exacerbating experimental NEC pathology.

Development of a novel definitive scoring system for an enteral feed-only model of necrotizing enterocolitis in piglets

Introduction

Necrotizing enterocolitis (NEC) is a complex inflammatory disorder of the human intestine that most often occurs in premature newborns. Animal models of NEC typically use mice or rats; however, pigs have emerged as a viable alternative given their similar size, intestinal development, and physiology compared to humans. While most piglet NEC models initially administer total parenteral nutrition prior to enteral feeds, here we describe an enteral-feed only piglet model of NEC that recapitulates the microbiome abnormalities present in neonates that develop NEC and introduce a novel multifactorial definitive NEC (D-NEC) scoring system to assess disease severity.

Methods

Premature piglets were delivered via Caesarean section. Piglets in the colostrum-fed group received bovine colostrum feeds only throughout the experiment. Piglets in the formula-fed group received colostrum for the first 24 h of life, followed by Neocate Junior to induce intestinal injury. The presence of at least 3 of the following 4 criteria were required to diagnose D-NEC: (1) gross injury score ≥4 of 6; (2) histologic injury score ≥3 of 5; (3) a newly developed clinical sickness score ≥5 of 8 within the last 12 h of life; and (4) bacterial translocation to ≥2 internal organs. Quantitative reverse transcription polymerase chain reaction was performed to confirm intestinal inflammation in the small intestine and colon. 16S rRNA sequencing was performed to evaluate the intestinal microbiome.

Results

Compared to the colostrum-fed group, the formula-fed group had lower survival, higher clinical sickness scores, and more severe gross and histologic intestinal injury. There was significantly increased bacterial translocation, D-NEC, and expression of IL-1α and IL-10 in the colon of formula-fed compared to colostrum-fed piglets. Intestinal microbiome analysis of piglets with D-NEC demonstrated lower microbial diversity and increased Gammaproteobacteria and Enterobacteriaceae.

Conclusions

We have developed a clinical sickness score and a new multifactorial D-NEC scoring system to accurately evaluate an enteral feed-only piglet model of NEC. Piglets with D-NEC had microbiome changes consistent with those seen in preterm infants with NEC. This model can be used to test future novel therapies to treat and prevent this devastating disease.

State-of-the-art review and update of in vivo models of necrotizing enterocolitis

NEC remains one of the most common causes of mortality and morbidity in preterm infants. Animal models of necrotizing enterocolitis (NEC) have been crucial in improving our understanding of this devastating disease and identifying biochemical pathways with therapeutic potential. The pathogenesis of NEC remains incompletely understood, with no specific entity that unifies all infants that develop NEC. Therefore, investigators rely on animal models to manipulate variables and provide a means to test interventions, making them valuable tools to enhance our understanding and prevent and treat NEC. The advancements in molecular analytic tools, genetic manipulation, and imaging modalities and the emergence of scientific collaborations have given rise to unique perspectives and disease correlates, creating novel pathways of investigation. A critical review and understanding of the current phenotypic considerations of the highly relevant animal models of NEC are crucial to developing novel therapeutic and preventative strategies for NEC.

Human Bone Marrow-Derived Mesenchymal Stromal Cells Reduce the Severity of Experimental Necrotizing Enterocolitis in a Concentration-Dependent Manner

Necrotizing enterocolitis (NEC) is a devastating gut disease in preterm neonates. In NEC animal models, mesenchymal stromal cells (MSCs) administration has reduced the incidence and severity of NEC. We developed and characterized a novel mouse model of NEC to evaluate the effect of human bone marrow-derived MSCs (hBM-MSCs) in tissue regeneration and epithelial gut repair. NEC was induced in C57BL/6 mouse pups at postnatal days (PND) 3-6 by (A) gavage feeding term infant formula, (B) hypoxia/hypothermia, and (C) lipopolysaccharide. Intraperitoneal injections of PBS or two hBM-MSCs doses (0.5 × 10⁶ or 1 × 10⁶) were given on PND2. At PND 6, we harvested intestine samples from all groups. The NEC group showed an incidence of NEC of 50% compared with controls (p < 0.001). Severity of bowel damage was reduced by hBM-MSCs compared to the PBS-treated NEC group in a concentration-dependent manner, with hBM-MSCs (1 × 10⁶) inducing a NEC incidence reduction of up to 0% (p < 0.001). We showed that hBM-MSCs enhanced intestinal cell survival, preserving intestinal barrier integrity and decreasing mucosal inflammation and apoptosis. In conclusion, we established a novel NEC animal model and demonstrated that hBM-MSCs administration reduced the NEC incidence and severity in a concentration-dependent manner, enhancing intestinal barrier integrity.

Models of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death and disability from gastrointestinal disease in premature infants. The mortality of patients with NEC is approximately 30%, a figure that has not changed in many decades, reflecting the need for a greater understanding of its pathogenesis. Progress towards understanding the cellular and molecular mechanisms underlying NEC requires the study of highly translational animal models. Such animal models must mimic the biology and physiology of premature infants, while still allowing for safe experimental manipulation of environmental and microbial factors thought to be associated with the risk and severity of NEC. Findings from animal models have yielded insights into the interactions between the host, the colonizing microbes, and the innate immune receptor Toll-like Receptor 4 (TLR4) in driving disease development. This review discusses the relative strengths and weaknesses of available in vivo, in vitro, and NEC-in-a-dish models of this disease. We also highlight the unique contributions that each model has made to our understanding of the complex interactions between enterocytes, microbiota, and immune cells in the pathogenesis of NEC. The overall purpose of this review is to provide a menu of options regarding currently available animal models of NEC, while in parallel hopefully reducing the potential uncertainty and confusion regarding NEC models to assist those who wish to enter this field from other disciplines.

Necrotizing enterocolitis: Bench to bedside approaches and advancing our understanding of disease pathogenesis

Necrotizing enterocolitis (NEC) is a devastating, multifactorial disease mainly affecting the intestine of premature infants. Recent discoveries have significantly enhanced our understanding of risk factors, as well as, cellular and genetic mechanisms of this complex disease. Despite these advancements, no essential, single risk factor, nor the mechanism by which each risk factor affects NEC has been elucidated. Nonetheless, recent research indicates that maternal factors, antibiotic exposure, feeding, hypoxia, and altered gut microbiota pose a threat to the underdeveloped immunity of preterm infants. Here we review predisposing factors, status of unwarranted immune responses, and microbial pathogenesis in NEC based on currently available scientific evidence. We additionally discuss novel techniques and models used to study NEC and how this research translates from the bench to the bedside into potential treatment strategies.

Astaxanthin Reduces the Severity of Intestinal Damage in a Neonatal Rat Model of Necrotizing Enterocolitis

OBJECTIVE

This study aimed to ascertain the effects of astaxanthin (ASX) in an experimental necrotizing enterocolitis (NEC) model using rat pups.

STUDY DESIGN

Forty-two pups born from five Wistar albino rats were randomly divided into three groups as the control group, NEC + placebo (saline), and NEC + ASX. Pups in the NEC + ASX group were given 100 mg/kg/day oral ASX from day 1 to day 4 of the study. Saline of 2 mL/kg was given to the NEC + placebo group. Histopathological, immunohistochemical (caspase-3), and biochemical evaluations including the total antioxidant status (TAS), total oxidant status (TOS), superoxide dismutase (SOD), glutathione (GSH), lipid hydroperoxide (LPO), 8-hydroxydeoxyguanosine (8-OHdG), advanced oxidation protein products (AOPP), myeloperoxidase (MPO), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and nuclear factor erythroid 2-related factor 2 (Nfr-2) activities were all performed.

RESULTS

A better survival rate and weight gain were demonstrated in the NEC + ASX group (p < 0.05). In the histopathological evaluation, the severity of intestinal damage was significantly reduced in the NEC + ASX group, as well as decreased apoptosis (enzyme-linked immunosorbent assay [ELISA] for caspase-3; p = 0.001). The biochemical analyses of intestinal tissue TOS, oxidative stress index (OSI; TOS/TAS), IL-1β, LPO, 8-OHdG, AOPP, caspase-3 (p < 0.001 for all), and TNF-α and MPO (p = 0.001 for both parameters) levels were lower in the NEC + ASX group than in the NEC + placebo group. Nrf-2, TAS, GSH, and SOD levels were higher in the NEC + ASX group than in the NEC + placebo group (p = 0.001, 0.001, <0.001, and 0.01, respectively).

CONCLUSION

ASX treatment has been shown to effectively reduce the severity of intestinal damage in NEC due to its antioxidant, anti-inflammatory, and antiapoptotic properties.

KEY POINTS

· NEC causes extremely high morbidity and mortality, as well as many complications.. · We investigated the effectiveness of ASX in the experimental NEC model created in rat pups.. · First study examining the effect of ASX on the experimental NEC rat model..

Comparison and Investigation of Exosomes from Human Amniotic Fluid Stem Cells and Human Breast Milk in Alleviating Neonatal Necrotizing Enterocolitis

In view of the devastating impact of neonatal necrotizing enterocolitis (NEC) on newborns, the research on its intervention is particularly important. Although exosomes from human amniotic fluid stem cells (AFSC) and human breast milk (HBM) can protect against NEC, their mechanisms remain unclear. Here, we intend to compare the intervention effects of two types of exosomes on NEC mouse model and reveal their respective regulatory mechanisms. In general, both AFSC-derived exosomes (AFSC-exos) and HBM-derived exosomes (HBM- exos) can alleviate NEC- associated intestinal injury, significantly reduce NEC score, and reduce systemic and ileal inflammation and NEC related brain injury during experimental NEC. However, the mode and mechanism of action of the two sources of exosomes were not identical. In vivo, the number of ileal crypts was more significantly restored after HBM-exos intervention than AFSC-exos, and in vitro, HBM-exos preferentially inhibited the inflammatory response of intestinal epithelial cells (IECs), whereas AFSC-exos preferentially regulated the migration of IECs. Mechanistically, GO and KEGG analyses revealed the different therapeutic mechanisms of AFSC-exos and HBM-exos in NEC. Taken together, our results illustrate that AFSC-exos and HBM-exos reduce the severity of experimental NEC and intestinal damage through different mechanisms, supporting the potential of cell-free or breast milk free exosome therapy for NEC.

Graphical Abstract

Efficacy of Probiotic Consortium Transplantation on Experimental Necrotizing Enterocolitis

INTRODUCTION

Fecal microbiota transplantation (FMT) is a promising therapy, but it has not been used to treat neonatal necrotizing enterocolitis (NEC) due to reports of adverse side effects. Probiotics are considered relatively safe with practicable administrative procedures; however, no systematic research has compared the results of FMT and probiotic consortium transplantation (PCT) on oxidative stress in the intestines of patients with NEC. We conducted this study to provide a basis for optimizing NEC therapy.

METHODS

Eight-day-old newborn C57BL/6 mice were randomly divided into the following four groups: the dam-fed group (control group); the NEC induction group (NEC group); the NEC induction and transplantation of Lactobacillus reuteri and Bifidobacterium infantis consortium group (NEC + PCT group); and the NEC induction and the FMT group (NEC + FMT). Intestinal injury, oxidative stress indexes, intestinal barrier function, and inflammatory cytokines were assessed in the terminal ileum.

RESULTS

FMT more effectively modulates oxidative stress in the intestine than does PCT; however, the difference between the effects of PCT and FMT was not significant. The protective effect was associated with enhanced antioxidant capacity, regulation of the main components of the mucus layer, reduced inflammatory reactions, and improved intestinal integrity.

CONCLUSIONS

Intestinal dysbiosis affects oxidative stress, inflammatory response, and mucosal integrity. Although FMT is more effective than PCT in regulating oxidative stress, PCT may be preferred in pediatrics because the proportion and dose of transplanted bacteria can be standardized and individualized according to individual conditions.

Antibacterial and anti-inflammatory effects of Lactobacillus reuteri in its biofilm state contribute to its beneficial effects in a rat model of experimental necrotizing enterocolitis

INTRODUCTION

Necrotizing enterocolitis (NEC) remains a significant surgical emergency in neonates. We have demonstrated the efficacy of Lactobacillus reuteri (Lr) in protecting against experimental NEC when administered as a biofilm by incubation with maltose loaded dextranomer microspheres. Lr possesses antimicrobial and anti-inflammatory properties. We developed mutant strains of Lr to examine the importance of its antimicrobial and anti-inflammatory properties in protecting the intestines from NEC.

METHODS

Premature rat pups were exposed to hypoxia/hypothermia/hypertonic feeds to induce NEC. To examine the importance of antimicrobial reuterin and anti-inflammatory histamine, pups received either native or mutant forms of Lr, in either its planktonic or biofilm states, prior to induction of NEC. Intestinal histology was examined upon sacrifice.

RESULTS

Compared to no treatment, administration of a single dose of Lr in its biofilm state significantly decreased the incidence of NEC (67% vs. 18%, p < 0.0001), whereas Lr in its planktonic state had no significant effect. Administration of reuterin-deficient or histamine-deficient forms of Lr, in either planktonic or biofilm states, resulted in significant loss of efficacy.

CONCLUSION

Antimicrobial and anti-inflammatory effects of Lr contribute to its beneficial effects against NEC. This suggests that both infectious and inflammatory components contribute to the etiology of NEC.

Next-Generation Probiotic Therapy to Protect the Intestines From Injury

Probiotics are live microorganisms that, when administered in adequate amounts, provide health benefits to the host. Some strains of the probiotic Lactobacillus reuteri (L. reuteri) have both antimicrobial and anti-inflammatory properties that may be exploited for the treatment and prevention of different gastrointestinal diseases, including necrotizing enterocolitis (NEC) and Clostridioides difficile (C. difficile) infection. Our laboratory has developed a new delivery system for L. reuteri in which the probiotic is incubated with biocompatible, semipermeable, porous dextranomer microspheres (DM) that can be loaded with beneficial and diffusible cargo. L. reuteri can be induced to form a biofilm by incubating the bacteria on the surface of these microspheres, which enhances the efficacy of the probiotic. Loading the DM with sucrose or maltose induces L. reuteri to produce more biofilm, further increasing the efficacy of the probiotic. Using a rat model of NEC, L. reuteri administered in its biofilm state significantly increases animal survival, reduces the incidence of NEC, preserves gut barrier function, and decreases intestinal inflammation. In a murine model of Clostridiodes difficile infection, L. reuteri administered in its biofilm state decreases colitis when administered either before or after C. difficile induction, demonstrating both prophylactic and therapeutic efficacy. There are currently no FDA-approved probiotic preparations for human use. An FDA-approved phase I clinical trial of L. reuteri in its biofilm state in healthy adults is currently underway. The results of this trial will be used to support a phase 1 clinical trial in neonates, with the goal of utilizing L. reuteri in its biofilm state to prevent NEC in premature neonates in the future.

The inhibition of enterocyte proliferation by lithocholic acid exacerbates necrotizing enterocolitis through downregulating the Wnt/β-catenin signalling pathway

Objectives

Necrotizing enterocolitis (NEC) is a catastrophic gastrointestinal emergency in preterm infants, whose exact aetiology remains unknown. The role of lithocholic acid (LCA), a key component of secondary bile acids (BAs), in NEC is unclear.

Methods

Clinical data were collected to analyse the changes of BAs in NEC patients. In vitro studies, the cell proliferation and cell death were assessed. In vivo experiments, the newborn rats were administered with low or high dose of LCA and further induced NEC.

Results

Clinically, compared with control group, total BAs in the NEC patients were significantly higher when NEC occurred. In vitro, LCA treatment significantly inhibited the cell proliferation through arresting cell cycle at G1/S phase without inducing apoptosis or necroptosis. Mechanistically, the Wnt/β‐catenin pathway was involved. In vivo, LCA inhibited intestinal cell proliferation leading to disruption of intestinal barrier, and thereby increased the severity of NEC. Specifically, LCA supplementation caused higher levels of FITC‐labelled dextran in serum, reduced PCNA expression and inhibited the activity of Wnt/β‐catenin pathway in enterocytes. The LC–MS/MS test found that LCA was significantly higher in intestinal tissue of NEC group, and more obviously in the NEC‐L and NEC‐H group compared with the DM group.

Conclusion

LCA exacerbates NEC by inhibiting intestinal cell proliferation through downregulating the Wnt/β‐catenin pathway.

The benefits, limitations and opportunities of preclinical models for neonatal drug development

Increased research to improve preclinical models to inform the development of therapeutics for neonatal diseases is an area of great need. This article reviews five common neonatal diseases - bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, perinatal hypoxic-ischemic encephalopathy and neonatal sepsis - and the available in vivo, in vitro and in silico preclinical models for studying these diseases. Better understanding of the strengths and weaknesses of specialized neonatal disease models will help to improve their utility, may add to the understanding of the mode of action and efficacy of a therapeutic, and/or may improve the understanding of the disease pathology to aid in identification of new therapeutic targets. Although the diseases covered in this article are diverse and require specific approaches, several high-level, overarching key lessons can be learned by evaluating the strengths, weaknesses and gaps in the available models. This Review is intended to help guide current and future researchers toward successful development of therapeutics in these areas of high unmet medical need.

DRG1 Maintains Intestinal Epithelial Cell Junctions and Barrier Function by Regulating RAC1 Activity in Necrotizing Enterocolitis

BACKGROUND

An immature intestine is a high-risk factor for necrotizing enterocolitis (NEC), which is a serious intestinal disease in newborns. The regulation of developmentally regulated GTP-binding protein 1 (DRG1) during organ development suggests a potential role of DRG1 in the maturation process of the intestine.

AIM

To illustrate the function of DRG1 during the pathogenesis of NEC.

METHODS

DRG1 expression in the intestine was measured using immunohistochemistry and q-PCR. Immunoprecipitation coupled with mass spectrometry was used to identify the interacting proteins of DRG1. The biological functions of the potential interactors were annotated with the Database for Annotation, Visualization and Integrated Discovery. Caco2 and FHs74Int cells with stable DRG1 silencing or overexpression were used to investigate the influence of DRG1 on cell junctions and intestinal barrier permeability and to elucidate the downstream mechanism.

RESULTS

DRG1 was constitutively expressed during the intestinal maturation process but significantly decreased in the ileum in the context of NEC. Protein interaction analysis revealed that DRG1 was closely correlated with cell junctions. DRG1 deficiency destabilized the E-cadherin and occludin proteins near the cell membrane and increased the permeability of the epithelial cell monolayer, while DRG1 overexpression prevented lipopolysaccharide-induced disruption of E-cadherin and occludin expression and cell monolayer integrity. Further investigation suggested that DRG1 maintained cell junctions, especially adherens junctions, by regulating RAC1 activity, and RAC1 inhibition with NSC23766 attenuated intestinal injury and led to improved barrier integrity in experimental NEC.

CONCLUSIONS

Our findings illustrate the mechanism underlying the effect of DRG1 deficiency on epithelial cell permeability regulation and provide evidence supporting the application of RAC1 inhibitors for protection against NEC.

Inhibition of Interleukin-6 signaling: A novel therapeutic approach to necrotizing enterocolitis

OBJECTIVES

This study investigated the effects of tocilizumab on the prevention and treatment of experimental necrotizing enterocolitis (NEC) in newborn rats.

METHODS

Forty-two newborn Sprague-Dawley rats were randomly separated into three groups: NEC + placebo, NEC + tocilizumab, and the control group. NEC + placebo and NEC + tocilizumab groups were given 1 mg/kg lipopolysaccharide intraperitoneally once only on the first day, were fed with a special rodent formula every 3 h, inhaled 100% CO2 for 10 min, were exposed to cold stress at + 4 °C for 5 min, and 97% O2 for 5 min twice a day for 3 days. NEC + tocilizumab group was treated with 8 mg/kg/day tocilizumab (Actemra®) intraperitoneally, while NEC + placebo group was given intraperitoneal 0.9% saline at a dose of 2 mL/kg/day from the first day to the end of the study. All newborn rats were sacrificed on day 4. Specimens were taken for histopathologic, immunohistochemical and biochemical evaluation from the ileum and proximal colon.

RESULTS

NEC + tocilizumab group had higher weight gain and survival rate compared to NEC + placebo group and clinical sickness score was reduced in NEC + tocilizumab group (p < 0.05). Lower tissue damage and apoptosis were found in the NEC + tocilizumab group compared to the NEC + placebo group (p < 0.01). Tissue Interleukin-6, Interleukin-1β, TNF-α, myeloperoxidase and caspase-3 levels were significantly decreased in the NEC + tocilizumab group (p < 0.01).

CONCLUSIONS

Tocilizumab could be a potential option in the prevention and treatment of NEC.

Ursodeoxycholic acid protects neonatal rats from necrotizing enterocolitis: a biochemical, histopathological, and immunohistochemical study

BACKGROUND

The pathophysiology of necrotizing enterocolitis (NEC) includes the massive production of endogenous cytokines with exaggerated activation of inflammatory pathways. Ursodeoxycholic acid (UDCA) has been used as an anti-inflammatory, antioxidant, and anti-apoptotic agent. We investigated the possible protective effects of UDCA in a neonatal rat pup model of NEC.

METHODS

We randomly divided rat pups into three groups: a control group, a non-treated NEC group, and a UDCA-treated NEC group. We induced NEC by feeding formula enterally and via hypoxia/reoxygenation. Intestinal samples were collected for histopathological and immunohistochemical evaluation. Blood samples were taken for biochemical analyses.

RESULTS

UDCA significantly reduced the extents of terminal ileal and jejunal injuries compared to the NEC group (p < .01), reduced Bax and caspase-3 immunoreactivities (both p < .01), and lowered serum levels of platelet-activating factor and intestinal fatty acid-binding protein (p < .01, p = .023, respectively).

CONCLUSIONS

In a rat model of NEC, UDCA protects against adverse intestinal histological, immunohistochemical, and biochemical changes. UDCA significantly reduces the effects of NEC on the rat pup intestine.

Lactobacillus reuteri in Its Biofilm State Improves Protection from Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a devastating disease predominately found in premature infants that is associated with significant morbidity and mortality. Despite decades of research, medical management with broad spectrum antibiotics and bowel rest has remained relatively unchanged, with no significant improvement in patient outcomes. The etiology of NEC is multi-factorial; however, gastrointestinal dysbiosis plays a prominent role in a neonate's vulnerability to and development of NEC. Probiotics have recently emerged as a new avenue for NEC therapy. However, current delivery methods are associated with potential limitations, including the need for at least daily administration in order to obtain any improvement in outcomes. We present a novel formulation of enterally delivered probiotics that addresses the current limitations. A single enteral dose of Lactobacillus reuteri delivered in a biofilm formulation increases probiotic survival in acidic gastric conditions, increases probiotic adherence to gastrointestinal epithelial cells, and reduces the incidence, severity, and neurocognitive sequelae of NEC in experimental models.

The decrease of fucosylation in intestinal epithelium is related to the development of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating neonatal gastrointestinal emergency. Fucosylated glycans on intestinal epithelial cells (IECs) play a central role in the maintenance of intestinal homeostasis. Nevertheless, its association with necrotizing enterocolitis is not clear. We examined paraffin-embedded intestinal specimens from participants and found that the NEC patients showed lower intestinal epithelial fucosylation levels than the control patients. In the mouse model of NEC, the percentage of fucosylated epithelial cells (F-ECs) and ILC3s was decreased. Also, the expression levels of IL-22 and Fut2 were reduced. Moreover, the critical role of epithelial fucosylation in NEC was further confirmed by administering the anti-IL-22 antibody, which caused an increase in histological damage, body weight loss, intestinal permeability and proinflammatory cytokine release correlated with a reduction of F-ECs. Overall, intestinal fucosylation deficiency led to increased susceptibility and severity of NEC. Further studies are needed to determine whether modification of intestinal fucosylation affects the development of NEC.

TFF3 mediates the NF-κB/COX2 pathway to regulate PMN-MDSCs activation and protect against necrotizing enterocolitis

Intestinal trefoil factor 3 (TFF3) plays an important role in repairing the intestinal mucosa. However, the detailed mechanism regarding immune regulation by TFF3 is not well defined. Here, we reported that treatment of mouse BM cells and human peripheral blood mononuclear cells from healthy volunteers with TFF3 activated polymorphnuclear myeloid-derived suppressor cells (PMN-MDSCs) in vitro. We also found that prostaglandin E2 is a major TFF3-mediated MDSC target, and that NF-κB/COX2 signaling was involved in this process. Moreover, TFF3 treatment or transfer of TFF3-derived PMN-MDSCs (TFF3-MDSCs) to experimental necrotizing enterocolitis (NEC) mice caused PMN-MDSC accumulation in the lamina propria (LP), which was associated with decreased intestinal inflammation, permeability, bacterial loading, and prolonged survival. Interestingly, no NEC severity remission was observed in Rag1 KO mice that were given TFF3-MDSCs, but coinjection with CD4⁺ T cells significantly relieved NEC inflammation. Overall, TFF3 mediates the NF-κB/COX2 pathway to regulate PMN-MDSC activation and attenuates NEC in a T-cell-dependent manner, which suggests a novel mechanism in preventing NEC occurrence.

Parenteral lipid emulsions induce unique ileal fatty acid and metabolomic profiles but do not increase the risk of necrotizing enterocolitis in preterm pigs

Necrotizing enterocolitis (NEC) is a manifestation of maladaptive intestinal responses in preterm infants centrally medicated by unattenuated inflammation. Early in the postnatal period, preterm infants develop a deficit in arachidonic and docosahexaenoic acid, both potent regulators of inflammation. We hypothesized that the fatty acid composition of parenteral lipid emulsions uniquely induces blood and intestinal fatty acid profiles which, in turn, modifies the risk of NEC development. Forty-two preterm pigs were randomized to receive one of three lipid emulsions containing 100% soybean oil (SO), 15% fish oil (MO15), or 100% fish oil (FO100) with enteral feedings over an 8-day protocol. Blood and distal ileum tissue were collected for fatty acid analysis. The distal ileum underwent histologic, proteomic, and metabolomic analyses. Eight pigs [3/14 SO (21%), 3/14 MO15 (21%), and 2/14 FO100 (14%)] developed NEC. No differences in NEC risk were evident between groups despite differences in induced fatty acid profiles in blood and ileal tissue. Metabolomic analysis of NEC versus no NEC tissue revealed differences in tryptophan metabolism and arachidonic acid-containing glycerophospholipids. Proteomic analysis demonstrated no differences by lipid group; however, 15 proteins differentiated NEC versus no NEC in the domains of tissue injury, glucose uptake, and chemokine signaling. Exposure to parenteral lipid emulsions induces unique intestinal fatty acid and metabolomic profiles; however, these profiles are not linked to a difference in NEC development. Metabolomic and proteomic analyses of NEC versus no NEC intestinal tissue provide mechanistic insights into the pathogenesis of NEC in preterm infants.NEW & NOTEWORTHY Exposure to parenteral lipid emulsions induces unique intestinal fatty acid and metabolomic profiles; however, these profiles are not linked to a difference in NEC risk in preterm pigs. Metabolomic and proteomic analyses provide mechanistic insights into NEC pathogenesis. Compared with healthy ileal tissue, metabolites in tryptophan metabolism and arachidonic acid-containing glycerophospholipids are increased in NEC tissue. Proteomic analysis differentiates NEC versus no NEC in the domains of tissue injury, glucose uptake, and chemokine signaling.

Necrotizing enterocolitis intestinal barrier function protection by antenatal dexamethasone and surfactant-D in a rat model

BACKGROUND

Necrotizing enterocolitis (NEC) is the most common gastrointestinal disorder in premature neonates. Possible therapeutic approaches are centered on promoting maturation of the gastrointestinal mucosal barrier. Studies have demonstrated that antenatal administration of corticosteroids can decrease NEC incidence and mortality.

METHODS

Pregnant rat dams were administered dexamethasone 48 h prior to delivery. The pups were subjected to an experimental NEC-like injury protocol. Ileal tissues and sera were collected and evaluated for inflammatory cytokines, gut permeability and expressions and localizations of tight junction proteins, and surfactant protein-D by immunohistochemistry/immunofluorescent staining. Intestinal epithelial cells (IEC-6) were pretreated with SP-D to examine the effect of SP-D on tight junction protein expressions when challenged with platelet-activating factor and lipopolysaccharide to model proinflammatory insults.

RESULTS

Antenatal dexamethasone reduced systemic inflammation, preserved intestinal barrier integrity, and stimulated SP-D expression on the intestinal mucosal surface in pups exposed to NEC-like injury. Pretreatment of SP-D blocked platelet-activating factor/lipopolysaccharide-induced tight junction disruption in IEC-6 cells in vitro.

CONCLUSIONS

Antenatal dexamethasone preserves the development of intestinal mucosal barrier integrity and reduces incidence and morbidity from an experimental NEC-like injury model. Dexamethasone upregulation of intestinal SP-D-protective effects on tight junction proteins.

IMPACT

Antenatal administration of dexamethasone can function in concert with intestinal surfactant protein-D to decrease systemic inflammatory responses, and protect intestinal barrier integrity in a neonatal rat model of NEC. A novel role of intestinal SP-D in preserving tight junction protein structures under inflammatory conditions. We describe the intestinal SP-D-an overlooked role of antenatal dexamethasone in neonatal NEC?

Intestinal tract and parenteral multi-organ sequential pathological injury caused by necrotizing enterocolitis

BACKGROUND

To explore the relationship between the pathological changes of the colon, terminal ileum, lung, liver and kidney, and the changes of Bax, PCNA and PAF in a rat model of NEC.

METHODS

One hundred and forty neonatal SD rats were randomly divided into NEC group and control group (70 in each group). NEC group was given hypoxia, cold stimulation and artificial feeding twice a day for 3 consecutive days. The control group was only fed normally. After modeling, From the 1st day to the 7th day, 10 rats were sampled in each group for pathological examination of colon, terminal ileum, lung, liver and kidney tissue. The levels of Bax, PCNA and PAF were investigated by immunohistochemistry.

RESULTS

Compared with the normal group, in the NEC group, on the 1st day, the colon, terminal ileum, lung, liver and kidney showed inflammatory damage. On the 5th day, the inflammatory injury was reduced. The inflammation disappeared on the 7th day. There were differences in the time of apoptosis in the intestine. In the intestine, the proliferation of PCNA was weak at first and then strong. Bax in liver and kidney showed marked apoptosis and apoptosis time increased in the lung. The expression of PCNA increased in lung, liver and kidney, and the expression of PAF increased in lung and liver.

CONCLUSIONS

NEC can lead to secondary injury of different degrees in colon, terminal ileum, lung, liver and kidney, and the degree and time of injury and repair were different. In general, organ repair played a leading role on the 4th day after modeling.

Maltodextrin-induced intestinal injury in a neonatal mouse model

Prematurity and enteral feedings are major risk factors for intestinal injury leading to necrotizing enterocolitis (NEC). An immature digestive system can lead to maldigestion of macronutrients and increased vulnerability to intestinal injury. The aim of this study was to test in neonatal mice the effect of maltodextrin, a complex carbohydrate, on the risk of intestinal injury. The goal was to develop a robust and highly reproducible murine model of intestinal injury that allows insight into the pathogenesis and therapeutic interventions of nutrient-driven intestinal injury. Five- to 6-day-old C57BL/6 mice were assigned to the following groups: dam fed (D); D+hypoxia+Klebsiella pneumoniae; maltodextrin-dominant human infant formula (M) only; M+hypoxia; and M+hypoxia+K. pneumoniae. The mice in all M groups were gavage fed five times a day for 4 days. Mice were exposed to hypoxia twice a day for 10 min prior to the first and last feedings, and K. pneumoniae was added to feedings as per group assignment. Mice in all M groups demonstrated reduced body weight, increased small intestinal dilatation and increased intestinal injury scores. Maltodextrin-dominant infant formula with hypoxia led to intestinal injury in neonatal mice accompanied by loss of villi, increased MUC2 production, altered expression of tight junction proteins, enhanced intestinal permeability, increased cell death and higher levels of intestinal inflammatory mediators. This robust and highly reproducible model allows for further interrogation of the effects of nutrients on pathogenic factors leading to intestinal injury and NEC in preterm infants.This article has an associated First Person interview with the first author of the paper.

Erythropoietin prevents necrotizing enterocolitis in very preterm infants: a randomized controlled trial

Background

Necrotizing enterocolitis (NEC) is one of the most severe complications in very preterm infants, but there are currently no accepted methods to prevent NEC. Studies have shown that erythropoietin (EPO) has the potential to prevent NEC or improve outcomes of preterm NEC. This study aimed to determine whether recombinant human EPO (rhEPO) could protect against NEC in very preterm infants.

Methods

The study was a prospective randomized clinical trial performed among four NICU centers. A total of 1327 preterm infants with gestational age ≤ 32 weeks were admitted to the centers, and 42 infants were excluded leaving 1285 eligible infants to be randomized to the rhEPO or control group. Infants in the rhEPO group were given 500 IU/kg rhEPO intravenously every other day for 2 weeks, while the control group was given the same volume of saline. The primary outcome was the incidence of NEC in very preterm infants at 36 weeks of corrected gestational age.

Results

A total of 1285 infants were analyzed at 36 weeks of corrected age for the incidence of NEC. rhEPO treatment significantly decreased the incidence of NEC (stage I, II and III) (12.0% vs. 17.1%, p = 0.010), especially confirmed NEC (stage II and III) (3.0% vs. 5.4%, p = 0.027). Meanwhile, rhEPO treatment significantly reduced the number of red blood cells transfusion in the confirmed NEC cases (1.2 ± 0.4 vs. 2.7 ± 1.0, p = 0.004). Subgroup analyses showed that rhEPO treatment significantly decreased the incidence of confirmed NEC at gestational age < 28 weeks (p = 0.019), and the incidence of all stages NEC in preterm infants with hemoglobin < 90 g/l (p = 0.000) and 5 min Apgar score > 5 (p = 0.028).

Conclusion

Repeated low-dose rhEPO treatment is beneficial against NEC in very preterm infants.

Trial registration The protocol was registered retrospectively at ClinicalTrials.gov (NCT03919500) on April 18, 2019. https://clinicaltrials.gov/ct2/show/NCT03919500

Precision-based modeling approaches for necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants and remains stubbornly difficult to treat in many cases. Much of our understanding of NEC pathogenesis has been gained through the study of highly translational animal models. However, most models of NEC are limited by their overall complexity and by the fact that they do not incorporate human tissue. To address these limitations, investigators have recently developed precision-based ex vivo models of NEC, also termed 'NEC-in-a-dish' models, which provide the opportunity to increase our understanding of this disease and for drug discovery. These approaches involve exposing intestinal cells from either humans or animals with or without NEC to a combination of environmental and microbial factors associated with NEC pathogenesis. This Review highlights the current progress in the field of NEC model development, introduces NEC-in-a-dish models as a means to understand NEC pathogenesis and examines the fundamental questions that remain unanswered in NEC research. By answering these questions, and through a renewed focus on precision model development, the research community may finally achieve enduring success in improving the outcome of patients with this devastating disease.

Developmental 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure of either parent enhances the risk of necrotizing enterocolitis in neonatal mice

BACKGROUND

Necrotizing enterocolitis (NEC) is a rare, but potentially fatal intestinal inflammatory condition most often arising in premature infants. Infants provided formula are also at greater risk of developing this disease. Although the majority of formula-fed, preterm infants do not develop NEC, up to 30% of infants with the disease do not survive. Thus, identifying additional, currently unrecognized factors, which may predispose a specific infant to NEC development would be a significant clinical advancement. In this regard, we have previously reported that offspring of female or male mice with a history of developmental exposure to the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exhibit altered sensitivity to inflammatory challenges and are frequently born premature. Herein, we examined the possibility that, compared to unexposed mice (F1_NONE ), developmental TCDD exposure of either parent (maternal, F1M_TCDD , or paternal, F1P_TCDD ) would enhance the risk of NEC in offspring (F2_TCDD mice) in association with supplemental formula feeding.

METHODS

Beginning on postnatal day 7, all neonates were randomized to maternal milk only or maternal milk with up to 20 supplemental formula feedings. All pups remained with the Dams and were additionally allowed to nurse ad libitum.

RESULTS

Formula-fed F2_NONE pups rarely developed NEC while this disease was common in formula-fed F2M_TCDD and F2P_TCDD mice. Unexpectedly, 50% of F2M_TCDD pups that were not provided supplemental formula also developed NEC.

CONCLUSIONS

Our studies provide evidence that a history of parental TCDD exposure enhances the risk of NEC in offspring and suggest exposure to environmental immunotoxicants such as TCDD may also contribute to this inflammatory disease in humans.

Preventative and therapeutic effects of fennel (Foeniculum vulgare) seed extracts against necrotizing enterocolitis

We aimed to understand the efficacy of fennel (Foeniculum vulgare: FV) extract in an experimental necrotizing enterocolitis (NEC) model. Forty-two rat pups were divided into three groups as NEC, NEC treated with fennel extract, and control. At the end of the experiment, tissue samples were taken from the proximal colon and ileum for biochemical and immuno-histological studies including hematoxylin-eosin and Caspase-3-8-9 immunohistochemical staining. Bowel damage and apoptosis were found to be less in the NEC + FV group. Oxidant stress, caspase 3, TNF-α, and IL-6 levels were considerably decreased in the NEC + FV group. Antioxidants were significantly higher in the NEC + FV group more than in the NEC group. Moreover, protein, DNA damage, and lipid peroxidation were found to be decreased in the NEC + FV group compared to the NEC group. PRACTICAL APPLICATIONS: Intense inflammation, oxidant stress, apoptosis, and infection are important in the development of NEC. Fennel has anti-oxidant, anti-inflammatory, antibacterial, antifungal, antiviral, immunomodulatory effects. Fennel extract might be a novel option in the treatment of NEC through its anti-oxidant, anti-inflammatory, anti-apoptotic, and cytoprotective features.

Histological analysis of the intestinal wall of newborn rats submitted to hypoxia and reoxygenation to evaluate the protective effect of N-Acetylcysteine

Purpose

To evaluate the effect of N-Acetylcysteine (NAC) in newborn rats submitted to hypoxia and reoxygenation (H/R) conditions in an experimental model of necrotizing enterocolitis.

Methods

Eight pregnant rats and their 70 cubs were used (5 groups) and exposed to H/R conditions and received NAC at different times. The animals in the H/R groups were placed in a gas chamber (100% CO²) for 10 minutes and then reoxygenated for 10 minutes (100% O²), twice a day for the first three days of life, with a six-hour span between events. On the third day of life, the animals were anesthetized, laparotomized and the intestines were resected.

Results

The H/R and NAC groups showed changes in the intestinal wall in relation to the number, height and width of the villi when compared to the control group (p<0.0001), but with better preservation of structures in the NAC group. There were no differences between groups regarding the number (%) of mitoses.

Conclusion

The administration of NAC decreased the lesions in the intestinal wall of rats submitted to H/R, therefore suggesting that this drug can be used to prevent the development of necrotizing enterocolitis in newborns.

Development of an improved murine model of necrotizing enterocolitis shows the importance of neutrophils in NEC pathogenesis

Various research models to induce necrotizing enterocolitis (NEC) in animals exist, yet significant differences in NEC severity between murine animal models and human patients persist. One possible explanation for the difference in severity may be the variance in neutrophil concentration among newborn humans (50-70%) in comparison to neonatal mice (10-25%). However, neutrophil activity has yet to be evaluated in NEC pathogenesis. Thus, the aim of the study was to evaluate the effects of altered neutrophil concentrations in neonatal mice while simultaneously undergoing a NEC induction. A total of 44 neonatal mice were included in this study and 40 were subjected to an established NEC induction paradigm and 4 were assigned a sham group. Of the 40 mice, 30 received granulocyte-colony stimulating factor (G-CSF) on a daily basis, while 10 were used as controls (receiving inactivated G-CSF). Mice undergoing G-CSF treatment were further divided into two subgroups: (1) wildtype and (2) ELANE-knockout (KO). ELANE - KO mice are incapable of producing neutrophil elastase (NE) and were used to evaluate the role of neutrophils in NEC. For each of the groups, the following metrics were evaluated: survival, NEC severity, tissue damage, neutrophil count and activation, and NETs formation. An improved murine model of NEC was developed using (1) Lipopolysaccharides and Neocate gavage feeding, (2) hypoxia, and (3) G-CSF administration. The results suggest that the addition of G-CSF resulted in significantly elevated NEC manifestation rates with consequent tissue damage and intestinal inflammation, without affecting overall mortality. Animals without functioning NE (ELANE-KO) appeared to have been protected from NEC development. This study supports the importance of neutrophils in NEC pathogenesis. The optimized NEC induction paradigm, using G-CSF administration, resulted in elevated neutrophil counts, resembling those of neonatal humans. Elevation of neutrophil levels significantly improved NEC disease manifestation by modeling human physiology more accurately than current NEC models. Thus, in the future, murine NEC experiments should include the elevation of neutrophil levels to improve the transition of research findings from mice to humans.

Impact of Developmental Age, Necrotizing Enterocolitis Associated Stress, and Oral Therapeutic Intervention on Mucus Barrier Properties

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease of incompletely understood pathophysiology predominantly affecting premature infants. While NEC is associated with microbial invasion of intestinal tissues, and mucus modulates interactions between microbes and underlying tissues, variations in mucus barrier properties with NEC-associated risk factors have not been investigated. This study explored differences in mucus composition (total protein, DNA, mucin content, sialic acid, and immunoregulatory proteins), as well as structural and transport properties, assessed by tracking of particles and bacteria (E. coli and E. cloacae) with developmental age and exposure to NEC stressors in Sprague Dawley rats. Early developmental age (5 day old) was characterized by a more permeable mucus layer relative to 21 day old pups, suggesting immaturity may contribute to exposure of the epithelium to microbes. Exposure to NEC stressors was associated with reduced mucus permeability, which may aid in survival. Feeding with breastmilk as opposed to formula reduces incidence of NEC. Thus, NEC-stressed (N-S) rat pups were orally dosed with breastmilk components lysozyme (N-S-LYS) or docosahexaenoic acid (N-S-DHA). N-S-LYS and N-S-DHA pups had a less permeable mucus barrier relative to N-S pups, which suggests the potential of these factors to strengthen the mucus barrier and thus protect against disease.

Human Milk Oligosaccharides Activate Epidermal Growth Factor Receptor and Protect Against Hypoxia-Induced Injuries in the Mouse Intestinal Epithelium and Caco2 Cells

BACKGROUND

Hypoxia-induced intestinal barrier injuries lead to necrotizing enterocolitis (NEC). Although NEC in preterm neonates is preventable by human milk oligosaccharides (HMOs), the underlying mechanism remains unknown.

OBJECTIVE

To reveal the role and mechanism of HMOs in protecting against hypoxia-induced injuries in intestinal epithelium of neonatal mice and cultured Caco2 cells.

METHODS

NEC was induced by hypoxia and cold stress. Seventy C57BL/C pups (7-d-old) were divided into 5 groups and fed maternal breast milk (BM), formula alone (FF), or the formula added with HMOs at 5 (LHMO), 10 (MHMO), or 20 mg/mL (HHMO) for 3 d. Ileal hypoxia inducible factor 1α (HIF1α) and cleaved Caspase 3 were determined, along with staining for Ki-67 protein to labeled proliferative cells. In vitro, adherent Caco2 cells (undifferentiated, passage 14) were treated with HMOs, galacto-oligosaccharides, fructo-oligosaccharides, or mixed oligosaccharides at 10 mg/mL for 1 d exposed to 1% O2. Cell proliferation and apoptosis, along with phosphorylated epidermal growth factor receptor (P-EGFR) and 38KD MAPK (P-P38), were assayed in differentiated or undifferentiated Caco2 cells.

RESULTS

Compared with the FF-fed mice, those fed MHMO and HHMO had 52% lower (P < 0.05) NEC scores, 60-80% greater (P < 0.05) KI67-positive cell numbers, and 56-71% decreases (P < 0.05) in ileal HIF1α and cleaved Caspase 3 (56-71%). Compared with those untreated, the HMO-treated Caco2 cells displayed 60% greater (P < 0.05) proliferative activity and 19% lower (P < 0.05) apoptotic cells after the hypoxia exposure. The HMO treatment led to 58% or 10-fold increases (P < 0.05) of P-EGFR and 48-89% decreases (P < 0.05) of P-P38 in either differentiated or undifferentiated Caco2 cells compared with the controls.

CONCLUSION

Supplementing HMOs at 10-20 mg/mL into the formula for neonatal mice or media for Caco2 cells conferred protection against the hypoxia-induced injuries. The protection in the Caco2 cells was associated with an activation of EGFR.

Prolyl hydroxylase 2 silencing enhances the paracrine effects of mesenchymal stem cells on necrotizing enterocolitis in an NF-κB-dependent mechanism

Treatment options for necrotizing enterocolitis (NEC) remain inadequate. Here we examined if and how prolyl hydroxylase 2 (PHD2) silencing enhances the paracrine effects of bone-marrow-derived mesenchymal stem cells (BM-MSCs) on NEC. In this study, BM-MSCs were transduced with lentiviruses containing GFP (GFP-MSC) or shPHD2-GFP constructs (PHDMSC), followed by intraperitoneal injection of the PHDMSC-conditioned medium (PHDMSC-CM) or the GFP-MSC-conditioned medium (MSC-CM) into a rat pup model of NEC. Our results showed that systemic infusion of PHDMSC-CM, but not MSC-CM, significantly improved intestinal damage and survival of NEC rats. Such benefits may involve the modulation of epithelial regeneration and inflammation, as indicated by the regeneration of intestinal epithelial/stem cells, the regulation of Treg cells function and pro-/anti-inflammatory cytokine balance. The mechanism for the superior paracrine efficacy of PHDMSC is related to a higher release of pivotal factor IGF-1 and TGF-β2. NF-κB activation was induced by PHD2 silencing to induce IGF-1 and TGF-β2 secretion via binding to IGF-1 and TGF-β2 gene promoter. Our work indicated that PHD2 silencing enhanced the paracrine effect of BM-MSCs on NEC via the NF-κB-dependent mechanism which may be a novel strategy for stem cell therapy on NEC.

Human Breast Milk-Derived Extracellular Vesicles in the Protection Against Experimental Necrotizing Enterocolitis

PURPOSE

Necrotizing enterocolitis (NEC) is a leading cause of death in premature infants. Breast feeding decreases the incidence of NEC but, even with aggressive promotion of nursing in Neonatal Intensive Care Units, morbidity and mortality remain high. Previous studies from our laboratory have demonstrated that extracellular vesicles (EVs) purified from mouse and rat stem cells can protect the intestines from NEC. The aim of this study was to determine whether human breast milk (BM)-derived EVs could prevent NEC.

METHODS

EVs were purified from human donor breast milk. NEC was induced in premature rat pups by exposure to asphyxia/hypothermia/hypercaloric feeds. Pups were randomized to: (1) breast fed, no injury, (2) NEC, (3) NEC + BM-derived EVs once intraperitoneally (IP), (4) NEC + BM-derived EVs enterally (PO) with each feed. Intestinal tracts were examined for histologic damage. Additionally, the effect of BM-derived EVs on intestinal epithelial cells (IEC) subjected to hypoxia/reoxygenation injury in vitro was examined.

RESULTS

NEC incidence was 0% in breast-fed pups and 62% in pups subjected to NEC. IP administration of BM-derived EVs decreased NEC incidence to 29% and enteral administration further decreased NEC incidence to 11.9%. (p < 0.05). BM-derived EVs significantly increased cell proliferation and decreased apoptosis in IEC in vitro.

CONCLUSION

Breast milk-derived EVs delivered either IP or enterally significantly decrease the incidence and severity of experimental NEC, protect IEC from injury in vitro, and may represent an innovative therapeutic option for NEC in the future.

TYPE OF STUDY

Basic science study.

LEVEL OF EVIDENCE

N/A.

Human β-defensin-3 reduces excessive autophagy in intestinal epithelial cells and in experimental necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of mortality in preterm newborns. Intestinal barrier dysfunction is one key event in NEC pathogenesis. Human β-defensin-3 (hBD3), one member of cationic host defence peptides, was reported to reduce the development of necrotizing enterocolitis in a neonatal rat model. And autophagy was induced in the intestine of human and animals with NEC. We hypothesized that regulation of autophagy might play a critical role in hBD3-mediated protection against NEC injury. Autophagy activity was evaluated both in intestinal epithelial cells and in NEC models. Newborn Sprague-Dawley rats were divided randomly into four groups: Control + NS, Control + rapamycin, NEC + NS, and NEC + hBD3. Body weight, histological score, survival time, enterocyte migration and mucosal barrier were recorded. Our results showed that hBD3 pretreatment could effectively inhibit autophagy activity in cultured IEC-6 and Caco2 enterocytes, and CXCR4 might be involved in hBD3-mediated autophagy suppression. Moreover, hBD3-induced inhibition of autophagy significantly promoted the intestinal epithelial cell migration by wound healing assay and transwell migration assay. In the rat model of NEC, hBD3 could noticeably reduce the expression of autophagy-activated proteins, down-regulate the expression of inflammatory mediators, and promote the mucosal integrity. Our data suggest an additional role of hBD3-mediated protection against intestinal mucosal injury: inhibition of over-activated autophagy in enterocytes.

β-arrestin-2 enhances intestinal epithelial apoptosis in necrotizing enterocolitis

Apoptosis among intestinal epithelial cells contributes to necrotizing enterocolitis (NEC), a severe intestinal disease that particularly affects premature infants. β-arrestin-2, an important regulator of G-protein-coupled receptors, is expressed in intestinal epithelial cells, where its activation promotes apoptosis. We found that β-arrestin-2 was overexpressed in both human and murine NEC samples. β-arrestin-2-deficient mice were protected from endoplasmic reticulum stress and NEC development. The endoplasmic reticulum-resident chaperone BiP was found to promote intestinal epithelial cell survival. Pretreatment of intestinal epithelial cells or mice with the BiP inhibitor HA15 increased cell apoptosis and promoted NEC development. β-arrestin-2 bound to BiP and promoted its polyubiquitination and degradation, thereby facilitating the release of the pro-apoptotic molecule BIK from BiP. Silencing β-arrestin-2 downregulated apoptosis by increasing BiP levels, which suppressed endoplasmic reticulum stress. This study suggests that β-arrestin-2 induces NEC development by inhibiting BiP, thereby triggering apoptosis in response to endoplasmic reticulum stress. Thus, novel therapeutic strategies to inhibit β-arrestin-2 may enhance the treatment of NEC.

Sumac (Rhus coriaria) for the prevention and treatment of necrotizing enterocolitis

Leukotrienes, free oxygen radicals, tumor necrosis factor-alpha, and inflammatory mediators play major roles in the development of necrotizing enterocolitis (NEC). Rhus coriaria (RC: sumac) extracts may enhance cell viability by reinforcing defenses against free radical species in several progressive diseases as well as inflammatory diseases. The aim of the present study was to evaluate the effects of RC in a rat NEC model in terms of intestinal damage. Newborn pups were separated into three groups: control, NEC, and NEC treated with RC. Mortality and clinical sickness scores were evaluated. At the end of the study, ileum and proximal colon were obtained from all rats and histopathological and immunohistochemical studies were performed. In this study, the anti-inflammatory, antioxidant, immunomodulatory, and anti-apoptotic activities of RC were demonstrated in a rat NEC model, which suggests RC as a promising treatment option for preventing intestinal tissue damage. PRACTICAL APPLICATIONS: Free oxygen radicals, tumor necrosis factor-alpha, and inflammatory mediators play major roles in the development of NEC. Intestinal tissue damage is caused by necrosis and apoptosis as a result of intestinal inflammation and release of pro-inflammatory cytokines. Anti-inflammatory, antioxidant, immunomodulatory, and anti-apoptotic activities of RC are especially due to its phenolic compounds. In this study, the anti-inflammatory, antioxidant, immunomodulatory, and anti-apoptotic activities of RC were demonstrated in a rat NEC model. RC can suggest as a new treatment option for preventing intestinal injury.

A murine neonatal model of necrotizing enterocolitis caused by anemia and red blood cell transfusions

Necrotizing enterocolitis (NEC) is an idiopathic, inflammatory bowel necrosis of premature infants. Clinical studies have linked NEC with antecedent red blood cell (RBC) transfusions, but the underlying mechanisms are unclear. Here we report a neonatal murine model to investigate this association. C57BL/6 mouse pups rendered anemic by timed phlebotomy and then given RBC transfusions develop NEC-like intestinal injury with prominent necrosis, inflammation, and submucosal edema/separation of the lamina propria in the ileocecal region and colon within 12-24 h. The anemic intestine is infiltrated by inflammatory macrophages, which are activated in situ by RBC transfusions via a Toll-like receptor (TLR)-4-mediated mechanism and cause bowel injury. Chelation of RBC degradation products with haptoglobin, absence of TLR4, macrophage depletion, and inhibition of macrophage activation is protective. Intestinal injury worsens with increasing severity and the duration of anemia prior to transfusion, indicating a need for the re-evaluation of current transfusion guidelines for premature infants.

The protective effects of fecal microbiota transplantation in an experimental model of necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is a serious disease that affects premature neonates, causing high mortality. In the search for new options of treatment it was investigated whether fecal microbiota transplantation (FMT) decreased the inflammatory response during NEC development in experimental model.

METHODS

Wistar rats were used and divided as follows: naïve, control (NEC induction), FMT-before (transplantation of microbiota before insult) and FMT-after (microbiota transplantation after insult). The microbiota transplantation was performed by administering a feces solution obtained from an adult donor rat. The induction of enterocolitis involves feeding by artificial formula, hypothermia, hypoxia and endotoxin administration. MPO activity, TNF-α, IL-1β and IL-6 levels, oxidative and nitrosative damage and the grade of intestinal mucosa lesion were analyzed.

RESULTS

The control group had a significant increase of inflammatory and oxidative parameters when compared to naive animals. Both FMT-before and after decreased all inflammatory and oxidative damage parameters when compared to control group. This was also true to the intestinal mucosa damage.

CONCLUSION

FMT administered just before or after NEC induction improved gut and systemic inflammation, and gut oxidative damage and intestinal injury.

Role of lactadherin in intestinal barrier integrity in experimental neonatal necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is one of the most widespread and devastating gastrointestinal diseases in neonates. Destruction of the intestinal barrier is the main underlying cause of NEC. The aim of this study was to determine the role of lactadherin in preventing NEC in a neonatal rat model and investigate the molecular mechanism of lactadherin-mediated protection of the intestinal barrier. Neonatal rats were divided into three groups: dam feeding (DF), NEC (NEC), and NEC supplemented with 10 μg/(g·day) recombinant human lactadherin (NEC+L). Intestinal permeability, tissue damage, and cell junction protein expression and localization were evaluated. We found that lactadherin reduced weight loss caused by NEC, reduced the incidence of NEC from 100% to 46.7%, and reduced the mean histological score for tissue damage to 1.40 compared with 2.53 in the NEC group. Intestinal permeability of lactadherin-treated rats was significantly reduced when compared with that of the NEC group. In addition, the expression levels of JAM-A, claudin 3, and E-calcium in the ileum of NEC group animals increased compared with those in the ileum of DF group animals, and these levels decreased in the NEC+L group. Lactadherin changed the localization of claudin 3, occludin, and E-cadherin in epithelial cells. The mechanism underlying lactadherin-mediated protection of the intestinal barrier might be restoring the correct expression levels and localization of tight junction and adherent junction proteins. These findings suggest a new candidate agent for the prevention of NEC in newborns.

Human Milk Oligosaccharides Protect against Necrotizing Enterocolitis by Inhibiting Intestinal Damage via Increasing the Proliferation of Crypt Cells

SCOPE

Necrotizing enterocolitis (NEC) is a devastating disease that is highly lethal in premature infants. Human milk oligosaccharides (HMOs) efficiently reduce the incidence of NEC. However, the protective mechanism of HMO treatment is unknown. It is hypothesized that HMOs protect against NEC by inhibiting the damage to intestinal epithelial cells.

METHODS AND RESULTS

C57BL/6 pups are challenged with hypoxia and cold stress to induce NEC. All pups are sacrificed after 72 h. It is found that HMO administration reduces the concentrations of IL-8 in the serum and ileum of all NEC mice. Ileum toll-like receptor 4 (TLR4) protein expression and nuclear factor kappa-B (NFκB) pathway activation are inhibited. The proliferative ability of enterocytes in the ileum is restored as determined by labeling with proliferation markers (Ki67, SOX9). In a 3D culture intestinal crypt organoids study, HMO treatment improves the maturation of organoid cells and increases the ratio of proliferative cells under lipopolysaccharides (LPS) treatment. HMO treatment downregulates TLR4 expression in the organoid cells, thus reducing the effect of LPS.

CONCLUSION

HMOs protect intestinal epithelial cells from injury by accelerating the turnover of crypt cells by reducing the expression of TLR4 on intestinal epithelial cells.

Necrotizing enterocolitis leads to disruption of tight junctions and increase in gut permeability in a mouse model

Background

Necrotizing enterocolitis (NEC) is a leading cause of death in preterm infants. Neonates weighing <1500 grams are at the highest risk for acquiring NEC, with a prevalence of nearly 7-10%, mortality up to 30%, and several long-term complications among survivors. Despite advancements in neonatal medicine, this disease remains a challenge to treat. The aim of this study is to investigate the effect of NEC on gut epithelial tight junctions and its barrier function using a NEC mouse model.

Methods

Three-day old C57BL/6 mouse pups were fed with Esbilac formula every 3 hours and then subjected to hypoxia twice daily followed by cold stress. Dam fed pups from the same litters served as controls. Pups were observed and sacrificed 96 hours after the treatments and intestines were removed for experiments. The successful induction of NEC was confirmed by histopathology. Changes in tight junction proteins in NEC intestines were studied by western blotting and immunofluorescent microscopy using specific protein markers. The gut leakage in NEC was visualized using biotin tracer molecules.

Results

Our study results demonstrate that we induced NEC in >50% of experimental pups, pups lost nearly 40% of weight and their intestines showed gross changes and microscopic changes associated with NEC. There were inflammatory changes with loss of tight junction barrier function and disruption of tight junction claudin proteins in the intestines of NEC mouse model. We have demonstrated for the first time that NEC intestines develop increased leakiness as visualized by biotin tracer leakage.

Conclusions

NEC leads to breakdown of epithelial barrier due to changes in tight junction proteins with increased leakiness which may explain the transmigration of microbes and microbial products from the gut lumen into the blood stream leading to sepsis like signs clinically witnessed.

Therapeutic and preventative effects of ankaferd blood stopper in an experimental necrotizing enterocolitis model

Necrotizing enterocolitis (NEC) is a major neonatal health problem that especially affects preterm infants and causes severe morbidity and mortality. Although its pathogenesis is not fully understood, important risk factors include prematurity, oxidative stress, inflammation, and apoptosis. Ankaferd Blood Stopper® (ABS) has antioxidant, antiinflammatory, antimicrobial, antiapoptotic, and wound healing accelerant properties. In this study, we aimed to investigate whether treatment with ABS reduced the severity of NEC in rat pups in an experimental NEC model. Thirty-six newborn Wistar albino rat pups were randomly assigned to the control, NEC + saline, or NEC + ABS groups. NEC was induced by intraperitoneal injection of lipopolysaccharide, feeding with hyperosmolar enteral formula, and exposure to hypoxia/hyperoxia and cold stress. ABS was administered intraperitoneally to the pups in the NEC + ABS group daily starting on day 1 of the study at a dose of 2 ml/kg by diluting 2 ml with saline at a ratio of 1:3. All pups were sacrificed on day 4. The terminal ileum including the proximal colon was removed for histopathological and immunohistochemical examination and biochemical analysis. Macroscopic assessment and intestinal injury scores were lower in NEC + ABS group compared to the NEC + saline group (p < 0.05). Immunohistochemical evaluations of caspase-3, -8, and -9 revealed significantly reduced apoptosis in the NEC + ABS group compared to the NEC + saline group (p = 0.001). Total oxidant status, oxidative stress index, tumor necrosis factor α and interleukin-1β levels, and lipid, protein, and deoxyribonucleic acid oxidation products were significantly lower in the NEC + ABS group compared to NEC + saline group (p < 0.001 for all), while total antioxidant status, glutathione, and superoxide dismutase levels were higher in the NEC + ABS group (p < 0.001, p < 0.001, p = 0.01, respectively). ABS treatment has the potential to effectively reduce the severity of intestinal damage in NEC due to its antioxidant, antiinflammatory, and antiapoptotic properties. Therefore, NEC may be an alternative option for treatment.