Impaired mucosal regeneration in neonatal necrotising enterocolitis

Early gut microbiota intervention in premature infants: Application perspectives

BACKGROUND

Preterm birth is the leading cause of death in children under the age of five. One of the major factors contributing to the high risk of diseases and deaths in premature infants is the incomplete development of the intestinal immune system. The gut microbiota has been widely recognized as a critical factor in promoting the development and function of the intestinal immune system after birth. However, the gut microbiota of premature infants is at high risk of dysbiosis, which is highly associated with adverse effects on the development and education of the early life immune system. Early intervention can modulate the colonization and development of gut microbiota and has a long-term influence on the development of the intestinal immune system.

AIM OF REVIEW

This review aims to summarize the characterization, interconnection, and underlying mechanism of gut microbiota and intestinal innate immunity in premature infants, and to discuss the status, applicability, safety, and prospects of different intervention strategies in premature infants, thus providing an overview and outlook of the current applications and remaining gaps of early intervention strategies in premature infants.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review is focused on three key concepts. Firstly, the gut microbiota of premature infants is at high risk of dysbiosis, resulting in dysfunctional intestinal immune system processes. Secondly, contributing roles of early intervention have been observed in improving the intestinal environment and promoting gut microbiota colonization, which is significant in the development and function of gut immunity in premature infants. Thirdly, different strategies of early intervention, such as probiotics, fecal microbiota transplantation, and nutrients, show different safety, applicability, and outcome in premature infants, and the underlying mechanism is complex and poorly understood.

Bugs and the barrier: A review of the gut microbiome and intestinal barrier in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease that affects premature neonates. It frequently results in significant morbidity and mortality for those affected. Years of research into the pathophysiology of NEC have revealed it to be a variable and multifactorial disease. However, there are risk factors associated with NEC including low birth weight, prematurity, intestinal immaturity, alterations in microbial colonization, and history of rapid or formula based enteral feeds (Fig. 1).^1-3 An accepted generalization of the pathogenesis of NEC includes a hyperresponsive immune reaction to insults such as ischemia, starting formula feeds, or alterations in the microbiome with pathologic bacterial colonization and translocation. This reaction causes a hyperinflammatory response disrupting the normal intestinal barrier, allowing abnormal bacterial translocation and ultimately sepsis.^1,2,4 This review will focus specifically on the interactions with the microbiome and intestinal barrier function in NEC.

Intestinal Epithelial Barrier Function and Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a major cause of morbidity and mortality in premature infants. NEC is characterized by intestinal tissue inflammation and necrosis. The intestinal barrier is altered in NEC, which potentially contributes to its pathogenesis by promoting intestinal bacterial translocation and stimulating the inflammatory response. In premature infants, many components of the intestinal barrier are immature. This article reviews the different components of the intestinal barrier and how their immaturity contributes to intestinal barrier dysfunction and NEC.

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.

Necrotizing Enterocolitis: LPS/TLR4-Induced Crosstalk Between Canonical TGF-β/Wnt/β-Catenin Pathways and PPARγ

Necrotizing enterocolitis (NEC) represents one of the major causes of morbidity and mortality in premature infants. Several recent studies, however, have contributed to a better understanding of the pathophysiology of this dreadful disease. Numerous intracellular pathways play a key role in NEC, namely: bacterial lipopolysaccharide (LPS), LPS toll-like receptor 4 (TLR4), canonical Wnt/β-catenin signaling and PPARγ. In a large number of pathologies, canonical Wnt/β-catenin signaling and PPARγ operate in opposition to one another, so that when one of the two pathways is overexpressed the other is downregulated and vice-versa. In NEC, activation of TLR4 by LPS leads to downregulation of the canonical Wnt/β-catenin signaling and upregulation of PPARγ. This review aims to shed light on the complex intracellular mechanisms involved in this pathophysiological profile by examining additional pathways such as the GSK-3β, NF-κB, TGF-β/Smads, and PI3K-Akt pathways.

Expressions of Fib, IL-12 in Serum of Neonatal Necrotizing Enterocolitis and Their Correlation with Clinicopathological Features

Background:

To investigate the expressions of fibrinogen (Fib) and Interleukin-12 (IL-12) in serum of neonatal necrotizing enterocolitis (NEC), and to analyze the correlation between the two and their relationship with clinicopathological features.

Methods:

Forty two children with NEC treated in Xuzhou Children’s Hospital, Xuzhou Medical University Xuzhou, China from 2016–2019 were selected as an observation group and 40 children who underwent physical examination at the same period as a control group. The expression levels of Fib and IL-12 in the serum of two groups were detected by ELISA. The correlation between Fib and IL-12 in the observation group and the correlation among the expressions of Fib, IL-12, the clinicopathological features and common examination indexes of the children with NEC were investigated by Pearson correlation analysis.

Results:

The levels of Fib and IL-12 in the serum of the children in observation group were significantly higher than those in the control group were (P<0.05). There was a significant positive correlation between the levels of Fib and IL-12 in the serum of the children in observation group (P<0.05). The expression levels of Fib, IL-12 were not significantly correlated with sex and age of NEC children, but correlated with vomiting, diarrhea, bloody stool and bradycardia in NEC children (P<0.05). Fib and IL-12 were positively correlated with erythrocyte level (P<0.05) and negatively correlated with platelet level.

Conclusion:

The expressions of Fib and IL-12 in the serum of NEC children can objectively predict the severity of NEC.

Transcriptome Differences Suggest Novel Mechanisms for Intrauterine Growth Restriction Mediated Dysfunction in Small Intestine of Neonatal Piglets

Impaired intestinal function is frequently detected in newborns with intrauterine growth restriction (IUGR), whereas the mechanism between transcriptome profiles and small intestinal dysfunction is still unclear. Therefore, this study was conducted by using IUGR neonatal piglets to uncover the mechanism underlying intestinal dysfunction. Neonatal piglets with IUGR and normal birth weight (NBW) were sacrificed at birth. Transcriptomic sequencing was performed on jejunum samples and generated 18,997 and 17,531 genes in NBW and IUGR groups, respectively. A total of 10 differentially expressed genes (DEGs) were identified; of note, only seven were mapped to the genome reference database, with two up-regulated (HSF4 and NR1H4; heat shock transcription factor 4 and nuclear receptor subfamily 1 group H member 4, respectively) and five down-regulated (SLC35C1, BTNL3, BPI, NLRP6, and SLC5A8; Solute carrier family 35 member C1, butyrophilin like 3, bactericidal permeability increasing protein, NLR family pyrin domain containing 6, and solute carrier family 5 member 8, respectively). Combining an enrichment analysis and reverse transcriptase–quantitative polymerase chain reaction validation of DEGs, our results proved the lipid metabolism disorder, intestinal dysfunction, and inflammatory response in IUGR piglets. Here, IUGR piglets presented lower concentration of glucose and triglyceride and higher concentration of total cholesterol and low-density lipoprotein cholesterol in plasma, compared with NBW piglets. Histological analysis revealed decreased mucins and increased apoptosis in both jejunum and ileum for IUGR piglets. Collectively, we found that IUGR induced intestinal dysfunction by altering lipid metabolism, intestinal barrier, and inflammatory response in neonatal piglets at birth, which provides new insights into the prevention and treatment of IUGR that protects against metabolic disorders and inflammatory-related diseases.

Necrotizing Enterocolitis: A Multi-omic Approach and the Role of the Microbiome

Necrotizing enterocolitis (NEC) is a poorly defined disease that primarily affects preterm infants. There has not been much progress in the prevention or treatment of NEC since it became recognized as a common problem in preterm infants. Reasons for this lack of progress include the likelihood that different diseases are being put under the same moniker of "NEC," similar to using "diabetes" for the different diseases it represents. In order to make progress, better delineation of the phenotypes that present as NEC will be necessary to clearly establish their pathophysiology, find specific and sensitive biomarkers, and establish preventative regimens. In this review, we summarize some of the entities that are being called NEC, discuss the pathophysiology of the most classic form of NEC, and provide an overview of how we might proceed in the future to make progress in this field.

Emerging Biomarkers for Prediction and Early Diagnosis of Necrotizing Enterocolitis in the Era of Metabolomics and Proteomics

Necrotizing Enterocolitis (NEC) is a catastrophic disease affecting predominantly premature infants and is characterized by high mortality and serious long-term consequences. Traditionally, diagnosis of NEC is based on clinical and radiological findings, which, however, are non-specific for NEC, thus confusing differential diagnosis of other conditions such as neonatal sepsis and spontaneous intestinal perforation. In addition, by the time clinical and radiological findings become apparent, NEC has already progressed to an advanced stage. During the last three decades, a lot of research has focused on the discovery of biomarkers, which could accurately predict and make an early diagnosis of NEC. Biomarkers used thus far in clinical practice include acute phase proteins, inflammation mediators, and molecules involved in the immune response. However, none has been proven accurate enough to predict and make an early diagnosis of NEC or discriminate clinical from surgical NEC or other non-NEC gastrointestinal diseases. Complexity of mechanisms involved in NEC pathogenesis, which remains largely poorly elucidated, could partly explain the unsatisfactory diagnostic performance of the existing NEC biomarkers. More recently applied technics can provide important insight into the pathophysiological mechanisms underlying NEC but can also aid the detection of potentially predictive, early diagnostic, and prognostic biomarkers. Progress in omics technology has allowed for the simultaneous measurement of a large number of proteins, metabolic products, lipids, and genes, using serum/plasma, urine, feces, tissues, and other biological specimens. This review is an update of current data on emerging NEC biomarkers detected using proteomics and metabolomics, further discussing limitations and future perspectives in prediction and early diagnosis of NEC.

Engineering the Mucus Barrier

Mucus selectively controls the transport of molecules, particulate matter, and microorganisms to the underlying epithelial layer. It may be desirable to weaken the mucus barrier to enable effective delivery of drug carriers. Alternatively, the mucus barrier can be strengthened to prevent epithelial interaction with pathogenic microbes or other exogenous materials. The dynamic mucus layer can undergo changes in structure (e.g., pore size) and/or composition (e.g., protein concentrations, mucin glycosylation) in response to stimuli that occur naturally or are purposely administered, thus altering its barrier function. This review outlines mechanisms by which mucus provides a selective barrier and methods to engineer the mucus layer from the perspective of strengthening or weakening its barrier properties. In addition, we discuss strategic design of drug carriers and dosing formulation properties for efficient delivery across the mucus barrier.

Evaluation of Intestinal Damage Biomarkers in Calves with Atresia Coli

Introduction

Intestinal obstruction such as atresia coli causes pathophysiological changes in gastrointestinal tissue due to the rise of intra-abdominal pressure. The aim of this study is to determine the intestinal damage with intestinal biomarkers in calves with atresia coli.

Material and Methods

The study was conducted on 40 Holstein calves diagnosed with atresia coli with mild to moderate abdominal distention and 10 healthy Holstein calves which served as the control. Blood samples were collected from all calves, and then serum concentrations of intestinal biomarkers were estimated, namely intestinal fatty acid binding protein (IFABP), liver fatty acid binding protein (LFABP), trefoil factor 3 (TFF3), and intestinal alkaline phosphatase (IAP), using commercially available specific bovine ELISA kits. An automatic blood gas analyser was employed for determining the lactate concentration.

Results

The concentrations of serum LFABP (P < 0.01), IFABP, TFF3, IAP, and blood lactate (P < 0.001) were significantly higher in calves with atresia coli than in healthy calves.

Conclusion

The calves affected with atresia coli exhibited severe intestinal damage, and IFABP, LFABP, and TFF3 have significant diagnostic importance and play a useful role in determining the intestinal damage due to intestinal obstruction. High levels of IAP and lactate may serve as a signal for the development of intestinal injury.

The Interaction of the Gut Microbiota with the Mucus Barrier in Health and Disease in Human

Glycoproteins are major players in the mucus protective barrier in the gastrointestinal and other mucosal surfaces. In particular the mucus glycoproteins, or mucins, are responsible for the protective gel barrier. They are characterized by their high carbohydrate content, present in their variable number, tandem repeat domains. Throughout evolution the mucins have been maintained as integral components of the mucosal barrier, emphasizing their essential biological status. The glycosylation of the mucins is achieved through a series of biosynthetic pathways processes, which generate the wide range of glycans found in these molecules. Thus mucins are decorated with molecules having information in the form of a glycocode. The enteric microbiota interacts with the mucosal mucus barrier in a variety of ways in order to fulfill its many normal processes. How bacteria read the glycocode and link to normal and pathological processes is outlined in the review.

Eukaryotic protein glycosylation: a primer for histochemists and cell biologists

Proteins undergo co- and posttranslational modifications, and their glycosylation is the most frequent and structurally variegated type. Histochemically, the detection of glycan presence has first been performed by stains. The availability of carbohydrate-specific tools (lectins, monoclonal antibodies) has revolutionized glycophenotyping, allowing monitoring of distinct structures. The different types of protein glycosylation in Eukaryotes are described. Following this educational survey, examples where known biological function is related to the glycan structures carried by proteins are given. In particular, mucins and their glycosylation patterns are considered as instructive proof-of-principle case. The tissue and cellular location of glycoprotein biosynthesis and metabolism is reviewed, with attention to new findings in goblet cells. Finally, protein glycosylation in disease is documented, with selected examples, where aberrant glycan expression impacts on normal function to let disease pathology become manifest. The histological applications adopted in these studies are emphasized throughout the text.

Inflammation and Apoptosis: Dual Mediator Role for Toll-like Receptor 4 in the Development of Necrotizing Enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is the leading cause of neonatal gastrointestinal mortality; effective interventions are lacking with limited understanding of the pathogenesis of NEC. The importance of Toll-like receptor 4 (TLR4) signaling in NEC is well documented; however, the potential mechanisms that regulate enterocyte inflammation and apoptosis remain unclear. The aim of this study was to characterize the role of TLR4-mediated inflammation and apoptosis in the development of NEC and to determine the major apoptotic pathways and regulators in the process.

METHODS

TLR4-deficient C57BL/10ScNJ mice and lentivirus-mediated stable TLR4-silent cell line (IEC-6) were used. NEC was induced by formula gavage, cold, hypoxia, combined with lipopolysaccharide in vivo or lipopolysaccharide stimulation in vitro. Enterocyte apoptosis was evaluated by TUNEL or Annexin analysis. The expression of TLR4, caspase3, caspase8, caspase9, Bip, Bax, Bcl-2, and RIP was detected by Western blot and immunofluorescence. Inflammatory factors such as tumor necrosis factor-α and interleukin-2 were examined by Luminex.

RESULTS

Defect of TLR4 led to suppressed enterocytes apoptosis both in vitro and in vivo; the expression of caspase3, caspase8, Bip, and Bax was decreased; and caspase9 and Bcl-2 were increased. NEC severity was attenuated in TLR4-deficient mice compared with wild-type counterparts, and enterocytes apoptosis was correlated with NEC severity. RIP and cytokine level of tumor necrosis factor-α and interleukin-2 were also decreased.

CONCLUSIONS

TLR4-induced inflammation and apoptosis play a critical role in the pathogenesis of NEC. TLR4 inhibition, combined with extrinsic (caspase8) and/or endoplasmic reticulum stress (Bip) apoptosis signaling blockade could serve as a potential effective treating strategy for NEC.

TFF2 deficiency exacerbates weight loss and alters immune cell and cytokine profiles in DSS colitis, and this cannot be rescued by wild-type bone marrow

The trefoil factor TFF2 is a member of a tripartite family of small proteins that is produced by the stomach and the colon. Recombinant TFF2, when applied intrarectally in a rodent model of hapten colitis, hastens mucosal healing and reduces inflammatory indexes. Additionally, TFF2 is expressed in immune organs, supporting a potential immunomodulatory and reparative role in the bowel. In this study we confirm that TFF2 is expressed in the colon and is specifically enriched in epithelial cells relative to colonic leukocytes. TFF2-deficient, but not TFF1-deficient, mice exhibit a more severe response to acute or chronic dextran sulfate (DSS)-induced colitis that correlates with a 50% loss of expression of TFF3, the principal colonic trefoil. In addition, the response to acute colitis is associated with altered expression of IL-6 and IL-33, but not other inflammatory cytokines. While TFF2 can reduce macrophage responsiveness and block inflammatory cell recruitment to the colon, the major role in limiting the susceptibility to acute colitis appears to be maintenance of barrier function. Bone marrow transfer experiments demonstrate that leukocyte expression of TFF2 is not sufficient for prevention of colitis induction but, rather, that the gastrointestinal epithelium is the primary source of TFF2. Together, these findings illustrate that epithelial TFF2 is an important endogenous regulator of gut mucosal homeostasis that can modulate immune and epithelial compartments. Because of its extreme stability, even in the corrosive gut lumen, TFF2 is an attractive candidate as an oral therapeutic scaffold for future drug development in the treatment of inflammatory bowel disease.

Pathogenesis of necrotizing enterocolitis: modeling the innate immune response

Necrotizing enterocolitis (NEC) is a major cause of morbidity and mortality in premature infants. The pathophysiology is likely secondary to innate immune responses to intestinal microbiota by the premature infant's intestinal tract, leading to inflammation and injury. This review provides an updated summary of the components of the innate immune system involved in NEC pathogenesis. In addition, we evaluate the animal models that have been used to study NEC with regard to the involvement of innate immune factors and histopathological changes as compared to those seen in infants with NEC. Finally, we discuss new approaches to studying NEC, including mathematical models of intestinal injury and the use of humanized mice.

Postnatal prebiotic fiber intake in offspring exposed to gestational protein restriction has sex-specific effects on insulin resistance and intestinal permeability in rats

Maternal protein restriction (PR) during pregnancy is known to have numerous adverse effects on offspring, including increased adiposity and impaired glucose tolerance later in life. A few studies have shown that this adverse programming can be reversed by dietary or hormonal therapies early in postnatal life. The objective of this study was to determine if a weaning diet high in prebiotic fiber could mitigate some of the negative effects of maternal PR, such as increased adiposity and impaired glucose tolerance. Wistar rats were fed a low- (8%) or normal- (20%) protein diet during pregnancy. Male and female pups were weaned onto control (C; 5% fiber, 20% protein) or high (prebiotic) fiber (HF; 21% wt:wt, 1:1 ratio oligofructose and inulin at 4-10 wk; 10% wt:wt, 1:1 ratio oligofructose and inulin at 10-24 wk; 17.3% protein) diets. At 24 wk of age, glucose tolerance, body composition, satiety hormones, gut microbiota, and markers of intestinal permeability were measured in the offspring. Maternal PR reduced offspring birth weight by 5% and lean mass by 9% compared with the C offspring (P < 0.007). HF-fed offspring had lower body weights and percentage body fat (∼23% in males, ∼19% in females) at 24 wk than did C offspring (P < 0.02). Compared with C pups, pups fed the HF diet had greater cecal Bifidobacterium spp. (>5-fold) and plasma concentrations of the gut trophic hormone glucagon-like peptide 2 (GLP-2) (P < 0.05). In male PR offspring fed the HF diet, insulin resistance measured by the homeostasis model assessment of insulin resistance was reduced by 81% compared with those fed the C diet (P = 0.02). In female PR offspring fed the HF diet, plasma endotoxin was greater and colonic tight junction protein 1 (Tjp1) expression was lower than in those fed the C diet. A high prebiotic fiber weaning diet mitigated increased adiposity and insulin resistance associated with maternal PR, which could improve health and decrease risk of chronic disease in offspring born to malnourished dams. However, the functional importance of sex-specific changes in markers of intestinal barrier function warrants further investigation.

Amniotic fluid stem cells improve survival and enhance repair of damaged intestine in necrotising enterocolitis via a COX-2 dependent mechanism

OBJECTIVE

Necrotising enterocolitis (NEC) remains one of the primary causes of morbidity and mortality in neonates and alternative strategies are needed. Stem cells have become a therapeutic option for other intestinal diseases, which share some features with NEC. We tested the hypothesis that amniotic fluid stem (AFS) cells exerted a beneficial effect in a neonatal rat model of NEC.

DESIGN

Rats intraperitoneally injected with AFS cells and their controls (bone marrow mesenchymal stem cells, myoblast) were analysed for survival, behaviour, bowel imaging (MRI scan), histology, bowel absorption and motility, immunofluorescence for AFS cell detection, degree of gut inflammation (myeloperoxidase and malondialdehyde), and enterocyte apoptosis and proliferation.

RESULTS

AFS cells integrated in the bowel wall and improved rat survival and clinical conditions, decreased NEC incidence and macroscopic gut damage, improved intestinal function, decreased bowel inflammation, increased enterocyte proliferation and reduced apoptosis. The beneficial effect was achieved via modulation of stromal cells expressing cyclooxygenase 2 in the lamina propria, as shown by survival studies using selective and non-selective cyclooxygenase 2 inhibitors. Interestingly, AFS cells differentially expressed genes of the Wnt/β-catenin pathway, which regulate intestinal epithelial stem cell function and cell migration and growth factors known to maintain gut epithelial integrity and reduce mucosal injury.

CONCLUSIONS

We demonstrated here for the first time that AFS cells injected in an established model of NEC improve survival, clinical status, gut structure and function. Understanding the mechanism of this effect may help us to develop new cellular or pharmacological therapies for infants with NEC.

Stem cells as a potential therapy for necrotizing enterocolitis

INTRODUCTION

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease of neonates, especially those born prematurely, that remains an important cause of morbidity and mortality. Although current treatments such as inotropes, antibiotics and ventilation are supportive, there is an urgent need for novel therapies that specifically target the affected intestine.

AREAS COVERED

We briefly introduce the disease and the effects on intestinal epithelia. We provide a brief description of amniotic fluid stem (AFS) cells, and then describe some recent data in which AFS cells were beneficial in an animal model of NEC and a potential mechanism is described. The effects of AFS cells are compared with data on bone marrow mesenchymal stem cells. The potential implications of these findings for therapy are discussed.

EXPERT OPINION

The current data are promising and demonstrate that stem cells do have an effect in rodent models of NEC. However, the short timescale, limited ability for longitudinal evaluation and uncertain clinical relevance of these models means that there are considerable challenges to be overcome before attempting stem cell therapy in clinical trials. Nevertheless, these data open up novel areas of research into a prevention or therapy for this devastating disease.

Duodenal perforation associated with norovirus and rotavirus gastroenteritis

Key Clinical Message

Norovirus (NoV) and rotavirus (RV) gastroenteritis are usually self-limiting. However, few pediatric cases of bowel perforation and no duodenal perforation with NoV gastroenteritis were reported. We describe two children with duodenal perforation due to NoV or RV gastroenteritis. Suspicion for this association enables prompt intervention, preventing lethal outcomes of these common infections.

Innate immune signaling in the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a challenging disease to treat, and caring for patients afflicted by it remains both frustrating and difficult. While NEC may develop quickly and without warning, it may also develop slowly, insidiously, and appear to take the caregiver by surprise. In seeking to understand the molecular and cellular processes that lead to NEC development, we have identified a critical role for the receptor for bacterial lipopolysaccharide (LPS) toll like receptor 4 (TLR4) in the pathogenesis of NEC, as its activation within the intestinal epithelium of the premature infant leads to mucosal injury and reduced epithelial repair. The expression and function of TLR4 were found to be particularly elevated within the intestinal mucosa of the premature as compared with the full-term infant, predisposing to NEC development. Importantly, factors within both the enterocyte itself, such as heat shock protein 70 (Hsp70), and in the extracellular environment, such as amniotic fluid, can curtail the extent of TLR4 signaling and reduce the propensity for NEC development. This review will highlight the critical TLR4-mediated steps that lead to NEC development, with a focus on the proinflammatory responses of TLR4 signaling that have such devastating consequences in the premature host.

Bacterial invasion of HT29-MTX-E12 monolayers: effects of human breast milk

AIM

The supramucosal gel, crucial for gut barrier function, might be compromised in necrotizing enterocolitis (NEC). Breast milk is associated with a reduced incidence of NEC. We compared the effects of human breast milk (BM) versus a neonatal formula, Nutriprem 1 (FF), on adherence, internalisation, and penetration of NEC-associated Escherichia coli through monolayers of mucus producing intestinal cells, HT29-MTX-E12 (E12).

METHODS

E12 cells were grown to confluence on membranes permeable to bacteria. E. coli, reference strain and isolated from a NEC-affected intestine, were cultured in LB broth, labelled with fluorescein and biotinylated. Bacteria were suspended in tissue culture medium (TC) or mixtures of TC with BM or FF and applied to the E12 cultures. Bacterial numbers were assessed by fluorescence. DyLight 650-labelled neutravidin, which cannot cross cell membrane, evaluated extracellular bacteria. Fluorescence of basolateral medium was measured to quantify translocation. Bacterial concentrations were compared using the Mann Whitney U test.

RESULTS

After 1h exposure, E12 cultures adhered or internalised more NEC-derived bacteria than standard strain E. coli and more suspended in FF than BM (P<0.001). A greater proportion of NEC-derived bacteria internalised when suspended in TC or BM. In FF, the NEC-derived strain internalised least. More translocation occurred in BM incubations compared to FF in the first 1-4h: NEC-E. coli less than the reference strain. After 24h translocated bacterial populations were equal.

CONCLUSION

In this pilot study, breast milk was associated with relatively less adhesion and internalisation of NEC-associated E. coli to mucus covered E12s compared to formula milk.

Treatment with intestinal trefoil factor regulates TLR2/4 and NF-κB expression and protects against LPS-induced intestinal injury in rats

AIM: To investigate whether intestinal trefoil factor (ITF) regulates the expression of Toll-like receptor (TLR) 2/4 and nuclear factor-κB (NF-κB) and exerts a protective effect against lipopolysaccharide (LPS)-induced intestinal injury in rats.

METHODS: Twenty-four 10-day-old Wistar rats were randomly and equally divided into three groups: control group (intraperitoneally injected with normal saline 1 mL/kg ), endotoxemia group (intraperitoneally injected with LPS 5 mg/kg), and LPS + ITF group (intraperitoneally injected with LPS 5 mg/kg and recombinant ITF 0.1 mL/per rat). Rats were sacrificed 3 h after injection. A segment of the distal ileum was dissected for hematoxylin-eosin staining. Pathological changes in the small intestine were observed under an optical microscope. The mRNA and protein expression of TLR2/4 and NF-κB was detected by RT-PCR and immunohistochemistry, respectively.

RESULTS: The structure of the small intestine of rats in the control group was normal. Inflammatory cell infiltration and interstitial/epithelial edema were observed in rats in the LPS group and LPS + ITF group, and the pathological changes were significantly milder in the LPS + ITF group than in the LPS group. The expression of TLR2 mRNA and protein in the LPS + ITF group was significantly higher than that in the LPS group (7.453 ± 1.90 vs 3.069 ± 0.08, 52.125 ± 4.1 vs 20.688 ± 2.4, both P < 0.01). The expression of TLR4 and NF-κB mRNAs and proteins in the LPS + ITF group was significantly lower than that in the LPS group (TLR4 mRNA: 5.373 ± 1.18 vs 16.711 ± 1.28, P< 0.01; TLR4 protein: 16.338 ± 4.98 vs 22.760 ± 3.68, P< 0.01; NF-κB mRNA: 0.533 ± 0.05 vs 2.228 ± 0.72, P< 0.01; NF-κB protein: 36.526 ± 9.18 vs 50.433 ± 3.37, P< 0.05).

CONCLUSION: Treatment with ITF protects against LPS-induced intestinal injury in rats possibly via mechanisms associated with down-regulation of TLR4 and NF-κB expression.

Trefoil factor family peptides are increased in the saliva of children with mucositis

BACKGROUND

Mucositis is a painful ulcerative condition of the oral cavity and gastrointestinal tract, occurring in association with chemotherapy and radiotherapy regimes. Trefoil factor family peptides (TFF, trefoil peptides), present in saliva, contribute to epithelial restitution and repair and are therefore potentially important in the healing phase of mucositis. This study aimed to assess any changes in the levels of trefoil peptides in oncology patients with and without mucositis.

METHODS

Saliva was collected from healthy children, pretreatment oncology patients, neutropenic patients on treatment with no oral disease and mucositic patients. TFF1, 2 and 3 were quantified using ELISA.

RESULTS

In healthy children TFF2 and 3 were positively correlated with age (r = 0.454, p = 0.01 for TFF2; r = 0.410, p = 0.05 for TFF3 Spearman rank correlation). TFF3 was higher in mucositis compared to all other groups. A linear regression prediction model indicated that TFF3, but not TFF1 and TFF2, was significantly different in mucositic and healthy controls, suggesting an altered pattern of trefoil peptide secretion (p = 0.021).

CONCLUSIONS

This study is the first to focus on trefoil peptides in paediatric saliva. It shows the correlation between TFF2, TFF3 and age in healthy children. Paediatric mucositis disease occurs in the presence of increased concentrations and an altered pattern of trefoil peptides.

Bifidobacterium bifidum improves intestinal integrity in a rat model of necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) is a major cause of morbidity and mortality in premature infants. Oral administration of probiotics has been suggested as a promising strategy for prevention of NEC. However, little is known about the mechanism(s) of probiotic-mediated protection against NEC. The aim of this study was to evaluate the effects of Bifidobacterium bifidum treatment on development of NEC, cytokine regulation, and intestinal integrity in a rat model of NEC. Premature rats were divided into three groups: dam fed (DF), hand fed with formula (NEC), or hand fed with formula supplemented with 5 x 10(6) CFU B. bifidum per day (B. bifidum). All groups were exposed to asphyxia and cold stress to develop NEC. Intestinal injury, mucin and trefoil factor 3 (Tff3) production, cytokine levels, and composition of tight junction (TJ) and adherens junction (AJ) proteins were evaluated in the terminal ileum. B. bifidum decreased the incidence of NEC from 57 to 17%. Increased levels of IL-6, mucin-3, and Tff3 in the ileum of NEC rats was normalized in B. bifidum treated rats. Reduced mucin-2 production in the NEC rats was not affected by B. bifidum. Administration of B. bifidum normalized the expression and localization of TJ and AJ proteins in the ileum compared with animals with NEC. In conclusion, administration of B. bifidum protects against NEC in the neonatal rat model. This protective effect is associated with reduction of inflammatory reaction in the ileum, regulation of main components of mucus layer, and improvement of intestinal integrity.

Epithelial functions of the residual bowel after surgery for necrotising enterocolitis in human infants

OBJECTIVES

Information on epithelial functions of the residual small or colonic bowel after resection for necrotising enterocolitis (NEC) in human infants is scarce. Our aim is to evaluate epithelial functions in the intestinal resection margins of tissue obtained at bowel resection for acute NEC and consecutive stoma closure.

MATERIALS AND METHODS

Epithelial morphology, proliferation, and protein expression were (immuno)histochemically studied.

RESULTS

Acute NEC was associated with severe and mild epithelial damage varying from epithelial loss to fairly unaffected epithelium. Epithelial proliferation was increased both at acute NEC and at stoma closure. In acute NEC, lactase, glucose transporter-2 and -5 expression was down-regulated in severely affected epithelium, whereas sucrase-isomaltase and intestinal fatty acid binding protein expression was maintained. Goblet cells continued to express mucin 2 and trefoil factor 3, however, their numbers were decreased. Moreover, in acute NEC, Paneth cells were weakly lysozyme positive and were reduced in number. At stoma closure, expression of the above cell type-specific markers had completely been re-established.

CONCLUSIONS

Residual bowel after resection for acute NEC shows a disturbed epithelial proliferation/differentiation balance. Acute NEC was associated with downregulation of distinct enterocyte-specific proteins. Because of goblet cell and Paneth cell loss in acute NEC, mucosal barrier, and defense functions may be impaired.

Intrauterine growth restriction alters postnatal colonic barrier maturation in rats

Intrauterine growth restriction (IUGR) is a leading cause of perinatal mortality and morbidity and increases the risk for necrotizing enterocolitis. We hypothesized that colonic barrier disruption could be responsible for intestinal frailty in infants and adults born with IUGR. Mucins and trefoil factor family 3 (TFF3) actively contribute to epithelium protection and healing. Our aim was to determine whether IUGR affects colonic mucosa maturation. IUGR was induced by dietary protein restriction in pregnant dams. Mucins and Tff3 expression and morphologic maturation of the colonic mucosa were followed during postnatal development of the offspring. Before weaning, mucin 2 and Tff3 protein levels were reduced in colonic mucosa of rats with IUGR compared with controls. After weaning, expression of mucin 2 (mRNA and protein) and mucin 4 (mRNA) were lower in colonic mucosa of rats with IUGR. At the same time, IUGR was associated with a reduction of crypt depth and a higher percentage of crypts in fission. We conclude that IUGR impairs mucus barrier development and is associated with long-term alterations of mucin expression. The lack of an efficient colonic barrier induced by IUGR may predispose to colonic injury not only in neonatal life but also in later life.

Gene expression in Barrett's esophagus: laser capture versus whole tissue

OBJECTIVE

Diagnosis of Barrett's esophagus (BE) is typically done through morphologic analysis of esophageal tissue biopsy. Such samples contain several cell types. Laser capture microdissection (LCM) allows the isolation of specific cells from heterogeneous cell populations. The purpose of this study was to determine the degree of overlap of the two sample types and to define a set of genes that might serve as biochemical markers for BE.

MATERIAL AND METHODS

Biopsies were obtained from regions of the glandular tissue of BE and normal esophagus from 9 subjects with BE. Samples from 5 subjects were examined as whole tissue (BE [whole]; E [whole]), and in 4 subjects the glandular epithelium of BE was isolated using LCM (BE [LCM]) and compared with the averaged values (E [LCM]) for both basal cell (B [LCM]) and squamous cell (S [LCM]) epithelium.

RESULTS

Gene expression revealed 1797 probe sets between BE [whole] and E [whole] (fold change > 2.0; p<0.001). Most of these genes (74%) were also differentially expressed between BE [LCM] and E [LCM], showing that there was high concordance between the two sampling methods. LCM provided a great deal of additional information (2113 genes) about the alterations in gene expression that may represent the BE phenotype.

CONCLUSIONS

There are differences in gene expression profiles depending on whether specimens are whole tissue biopsies or LCM dissected. Whole tissue biopsies should prove satisfactory for diagnostic purposes. Because the data from LCM samples delineated many more Barrett's-specific genes, this procedure might provide more information regarding pathogenesis than would whole tissue material.

Trefoil factors in human milk

We measured concentrations of the gastrointestinal protective peptides Trefoil factors in human milk. By the use of in-house ELISA we detected high amounts of TFF3, less TFF1 and virtually no TFF2 in human breast milk obtained from 46 mothers with infants born extremely preterm (24-27 wk gestation), preterm (28-37 wk gestation), and full term (38-42 wk gestation). Samples were collected during the first, second, third to fourth weeks and more than 4 wks postpartum. Median (range) TFF1 [TFF3] concentrations in human milk were 320 (30-34000) [1500 (150-27,000)] pmol/L in wk 1, 120 (30-720) [310 (50-7100)] pmol/L in wk 2, 70 (20-670) [120 (20-650)] pmol/L in wks 3 to 4, and 60 (30-2500) [80 (20-540)] pmol/L in >4 wks after delivery. The lowest concentrations of TFF1 and TFF3 were found later than 2 wks after birth. In conclusion, TFF was present in term and preterm human milk with rapidly declining concentrations during the first weeks post partum. The clinical significance of TFF present in human milk remains to be explored, both regarding development of the fetal gut and protection against necrotizing enterocolitis.

Necrotizing enterocolitis: A multifactorial disease with no cure

Necrotizing enterocolitis is an inflammatory bowel disease of neonates with significant morbidity and mortality in preterm infants. Due to the multifactorial nature of the disease and limitations in disease models, early diagnosis remains challenging and the pathogenesis elusive. Although preterm birth, hypoxic-ischemic events, formula feeding, and abnormal bacteria colonization are established risk factors, the role of genetics and vasoactive/inflammatory mediators is unclear. Consequently, treatments do not target the specific underlying disease processes and are symptomatic and surgically invasive. Breast-feeding is the most effective preventative measure. Recent advances in the prevention of necrotizing enterocolitis have focused on bioactive nutrients and trophic factors in human milk. Development of new disease models including the aspect of prematurity that consistently predisposes neonates to the disease with multiple risk factors will improve our understanding of the pathogenesis and lead to discovery of innovative therapeutics.

Understanding the susceptibility of the premature infant to necrotizing enterocolitis (NEC)

Necrotizing enterocolitis (NEC) is the most common life-threatening gastrointestinal emergency encountered in the neonatal intensive care unit. Despite advances in neonatal care, NEC remains a leading cause of morbidity and mortality among premature infants. Epidemiologic studies have identified multiple factors that increase an infant's risk for the development of NEC, although premature birth, bacterial colonization, and enteral feeding are thought to play central roles in disease pathogenesis. Appreciating factors that underlie the susceptibility of prematurely born infants to NEC is important for the development of new strategies aimed at the prevention and treatment of disease. In this review, we discuss defense mechanisms in the intestine and discuss how these systems may be insufficient in the prematurely born infant and thereby further contribute to initiation of NEC. In addition, based on a review of the literature, we suggest that, although numerous bacterial and viral pathogens have been associated with NEC, no individual organism is known to be responsible for disease. Finally, we comment on the possible role for probiotics in promoting maturation of intestinal defense mechanisms thereby attenuating or preventing the sequence of events that lead to NEC.

Inhibition of estrogen-mediated uterine gene expression responses by dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exhibits antiestrogenic properties, including the inhibition of estrogen-induced uterine growth and proliferation. The inhibition of estrogen-mediated gene expression through ER/AhR cross-talk has been proposed as a plausible mechanism; however, only a limited number of inhibited responses have been investigated that are unlikely to fully account for the antiuterotrophic effects of TCDD. Therefore, the effects of TCDD on ethynyl estradiol (EE)-mediated uterine gene expression were investigated using cDNA microarrays with complementary physiological and histological phenotypic anchoring. Mice were gavaged with vehicle, 3 daily doses of 10 mug/kg EE, a single dose of 30 mug/kg TCDD, or a combination of EE plus TCDD and sacrificed after 4, 12, 24, and 72 h. TCDD cotreatment inhibited EE-induced uterine wet weight by 37, 23, and 45% at 12, 24, and 72 h, respectively. TCDD cotreatment also reduced EE-mediated stromal edema, hypertrophy, and hyperplasia and induced marked luminal epithelial cell apoptosis. A 2 x 2 factorial microarray design was used to identify EE- and TCDD-specific differential gene expression responses as well as their interactive effects. Only 133 of the 2753 EE-mediated differentially expressed genes were significantly modulated by TCDD cotreatment, indicating a gene-specific inhibitory response. The EE-mediated induction of many genes, including trefoil factor 1 and keratin 14, were inhibited by greater than 90% by TCDD. Functional annotation of inhibited responses was associated with cell proliferation, water and ion transport, and maintenance of cellular structure and integrity. These inhibited responses correlate with the observed histological alterations and may contribute to the antiuterotrophic effects of TCDD.

High-dose erythropoietin inhibits apoptosis and stimulates proliferation in neonatal rat intestine

BACKGROUND

Erythropoietin (Epo) receptors are widely expressed in the small bowel of neonatal rats and evidence suggests Epo has important trophic effects in developing bowel.

OBJECTIVE

To compliment in vitro data, we directly examine in vivo the hypotheses that systemic Epo treatment can promote cell division and enterocyte migration, and arrest apoptosis in the ileum of neonatal rats.

DESIGN

Epo (5000 U/kg s.c.) or vehicle treatments were given to one week old Sprague-Dawley rats (n = 86) along with timed injections of the thymidine analog 5-bromo-2-deoxyuridine (BrdU, 50mg/kg s.c.) to label DNA synthesis and track newly proliferating cells. To characterize the time course of effects, animals were killed at scheduled times from 30 min to 24 h after treatment. BrdU-containing cells were immunostained and counted in intestinal crypts, villi, and muscle wall of ileum. Effects of Epo on apoptosis were analyzed by TUNEL staining. Calibrated measurements were made to determine the density or relative proportion of BrdU- and TUNEL-positive cells.

RESULTS

Systemic high-dose Epo promoted cell division in intestinal smooth muscle and enterocytes, stimulated migration of intestinal epithelial cells, and arrested apoptosis of enterocytes at the villous tips.

CONCLUSION

These data provide in vivo evidence that Epo functions trophically in developing intestine tissues.

Cellular localization, binding sites, and pharmacologic effects of TFF3 in experimental colitis in mice

Trefoil factors (TFFs) are essential for protection and restitution of the gastrointestinal mucosa but many aspects of TFF biology are unclear. Our aim was to compare the localization of endogenous TFFs and binding sites for injected TFF3 in the colon of healthy and colitic mice and to study the effect of TFF3 on dextrane sulfate sodium (DSS)-induced colitis in mice. Expression of endogenous TFF1-3 was examined by in situ hybridization and immunohistochemistry, and the distribution of intravenously, intraperitoneally, and subcutaneously administered (125)I-TFF3 by autoradiography and gamma-counting. The effect of systemically administered TFF3 on DSS-induced colitis was assessed. We found increased expression of endogenous TFF3 and increased binding of injected (125)I-TFF3 in the colon of animals with DSS-induced colitis. The distribution of intraperitoneally and subcutaneously administered (125)I-TFF3 was comparable. Systemic administration of the peptides reduced the severity of colitis. Expression of endogenous TFF3 and binding of systemically administered TFF3 are increased in DSS-induced colitis. Systemic administration of TFF3 attenuates the disease. These findings suggest a role of TFF3 in mucosal protection.

Necrotizing Enterocolitis: Review of State-of-the-Art Imaging Findings with Pathologic Correlation

Plain abdominal radiography is the current standard imaging modality for evaluation of necrotizing enterocolitis (NEC). Sonography is still not routinely used for diagnosis and follow-up, as it is not widely recognized that it can provide information that is not provided by plain abdominal radiography and that may affect the management of NEC. Like plain abdominal radiography, sonography can depict intramural gas, portal venous gas, and free intraperitoneal gas. However, the major advantages of abdominal sonography over plain abdominal radiography are that it can depict intraabdominal fluid, bowel wall thickness, and bowel wall perfusion. Sonography may depict changes consistent with NEC when the plain abdominal radiographic findings are nonspecific and inconclusive. Thinning of the bowel wall and lack of perfusion at sonography are highly suggestive of nonviable bowel and may be seen before visualization of pneumoperitoneum at plain abdominal radiography. The mortality rate is higher after perforation; thus, earlier detection of severely ischemic or necrotic bowel loops, before perforation occurs, could potentially improve the morbidity and mortality in NEC. The information provided by sonography allows a more complete understanding of the state of the bowel in patients with NEC and may thus make management decisions easier and potentially change outcome.

Gut responses to enteral nutrition in preterm infants and animals

Preterm birth is associated with immature digestive function that may require the use of total parenteral nutrition and special oral feeding regimens. Little is known about the responses to oral food in the preterm neonate and how enteral nutrients affect the immature gastrointestinal tract (GIT). In vivo studies are difficult to perform in laboratory rodents because of their small body size and that of immature organs at birth, and this makes the large farm animals (e.g., pigs, cattle, sheep) more attractive models in this field. In these species, preterm delivery at 88%-95% gestation is associated clinical complications and degrees of GIT immaturity similar to those in infants born at 70%-90% gestation. Studies in both animals and infants indicate that the immature GIT responds to the first enteral food with rapid increases in gut mass and surface area, blood flow, motility, digestive capacity, and nutrient absorption. To a large extent, the enteral food responses are birth independent, and can be elicited also in utero, at least during late gestation. Nevertheless, preterm neonates show compromised GIT structure, function, and immunology, particularly when delivered by caesarean section and fed diets other than mother's milk. Formula-fed preterm infants are thus at increased risk of developing diseases such as necrotizing enterocolitis, unless special care is taken to avoid excessive nutrient fermentation and bacterial overgrowth. The extent to which results obtained in preterm animals (most notably the pig) can be used to reflect similar conditions in preterm infants is discussed.

Heparin-binding epidermal growth factor-like growth factor promotes enterocyte migration and proliferation in neonatal rats with necrotizing enterocolitis

PURPOSE

We have shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF) decreases experimental necrotizing enterocolitis (NEC). Intestinal epithelial cell (IEC) migration (restitution) and proliferation are key elements in recovery from intestinal injury. Here, we investigated whether the beneficial effects of HB-EGF are mediated, in part, by its ability to affect these processes.

METHODS

Necrotizing enterocolitis was induced in newborn rats by exposure to stress (hypoxia, hypothermia, hypertonic feedings, and lipopolysaccharide), with pups receiving different doses of HB-EGF (0, 25, 50, 100, 200, 400, 600, and 800 microg/kg). To investigate the effect of HB-EGF on enterocyte proliferation and migration, bromodeoxyuridine was administered intraperitoneally 18 hours before sacrifice, with intestine subjected to bromodeoxy-uridine immunohistochemistry.

RESULTS

The incidence and severity of experimental NEC decreased, and the survival rate increased, with increasing doses of HB-EGF. Results were confirmed using scanning electron microscopy. Migration of IEC in breast-fed pups was 7.07 microm/h, decreased significantly to 2.29 microm/h in stressed pups, and was significantly improved at 5.95 microm/h in pups subjected to stress but treated with HB-EGF (P < .05). Quantification of IEC proliferation revealed 208 (+) cells per high-power field (HPF) in breast-fed pups, which decreased significantly to 99 (+) cells per HPF in stressed pups and increased to 190 (+) cells per HPF in stressed pups treated with HB-EGF (P < .05).

CONCLUSIONS

These results demonstrate that HB-EGF protects newborn rats from experimental NEC in a dose-dependent fashion. The ability of HB-EGF to protect the intestines from NEC is due, in part, to the ability of HB-EGF to preserve enterocyte migration and proliferation.

Using LongSAGE to Detect Biomarkers of Cervical Cancer Potentially Amenable to Optical Contrast Agent Labelling

Sixteen longSAGE libraries from four different clinical stages of cervical intraepithelial neoplasia have enabled us to identify novel cell-surface biomarkers indicative of CIN stage. By comparing gene expression profiles of cervical tissue at early and advanced stages of CIN, several genes are identified to be novel genetic markers. We present fifty-six cell-surface gene products differentially expressed during progression of CIN. These cell surface proteins are being examined to establish their capacity for optical contrast agent binding. Contrast agent visualization will allow real-time assessment of the physiological state of the disease process bringing vast benefit to cancer care. The data discussed in this publication have been submitted to NCBIs Gene Expression Omnibus (GEO, http://www.ncbi.nlm.nih.gov/geo/ ) and are accessible through GEO Series accession number GSE6252.

Proliferative response in necrotising enterocolitis is insufficient to prevent disease progression

Necrotising enterocolitis (NEC) is characterised by severe mucosal loss and therefore gastrointestinal (GI) cell proliferation is essential for survival, epithelial repair and recovery of function. Trefoil peptides play a key role in epithelial restitution and repair, and we previously reported a down-regulation of these peptides in NEC. Oral administration of epidermal growth factor has a protective effect in a rat model of colitis. These observations raised the question of a link between the pathogenesis of NEC and decreased mucosal cell proliferation. This study investigates the pattern of mucosal cell proliferation in the GI tract of fetuses, normal neonatal controls, infants with NEC and those recovering from NEC. Parents of neonates up to 44 weeks' gestation undergoing laparotomy and bowel resection were approached for consent. Bowel samples from resection specimens, and GI tract extractions from products of conception at termination of pregnancy, were fixed in formalin and then embedded in paraffin blocks. Patterns of small and large bowel mucosal proliferation were assessed by immunohistochemical staining for Ki67. Seventeen foetal and 58 postnatal bowel samples [34 with NEC (22 acute, 12 recovery) and 24 controls] were analysed. The pattern of proliferation seen in the fetus and normal neonate was identical to that in mature bowel. In NEC severe mucosal necrosis was observed, but in viable crypts remaining, there was crypt hyperplasia and a relative increase in the proportion of cells staining positive for Ki67. In those patients recovering from NEC the pattern of proliferation was returning towards the normal range. In those patients with post-NEC strictures the recovery of normal bowel morphology was delayed. In NEC there is massive loss of potential proliferative tissue. The remaining viable tissue shows an increase in proliferative activity in the small and large bowel. Failure of rapid regeneration of functional mucosa may therefore be related to an inability of increased proliferative activity to match the losses from the surface; alternatively there may be rapid production of immature, short-lived cells. This study shows that the proliferative response, although present, is insufficient to rapidly reverse the mucosal insult observed in NEC.