Experimental Modeling of Necrotizing Enterocolitis in Human Infant Intestinal Enteroids

Despite Recovery from Necrotizing Enterocolitis Infants Retain a Hyperinflammatory Response to Injury

Background

Necrotizing enterocolitis (NEC) is the leading gastrointestinal cause of death of premature neonates. NEC is associated with prematurity, a hyperinflammatory response, and dysregulation of intestinal barrier function. We hypothesize that patients with NEC will have, and continue to have after recovery, an increased hyperinflammatory intestinal response compared to those patients without NEC.

Methods

Neonates with NEC, those that have recovered from NEC, and those without NEC undergoing intestinal resections had specimens collected and snap frozen or generated into enteroids. The enteroids were treated with 100ug/mL lipopolysaccharide (LPS) and subjected to 24 hr of hypoxia together, then compared with untreated controls. Expression of Tumor Necrosis Factor (TNF-α) and interleukin 8 (IL-8) were evaluated via RT-qPCR and ELISA to measure inflammatory response. ANOVA determined statistical significance (p<0.05).

Results

There was no difference in inflammatory markers in recovered NEC tissue compared to non-NEC tissue on RTqPCR (p=0.701 TNF-α and 0.861 IL-8). However, recovered NEC enteroids demonstrate elevated levels of inflammatory markers after treatment compared to non-NEC enteroids after treatment on RTqPCR (p=0.0485 TNF-α, p=0.0057 IL-8) and ELISA (p=0.0354 TNF-α, p=0.0011 IL-8). Recovered NEC enteroids that underwent treatment demonstrated increased inflammatory markers compared to recovered NEC enteroids without treatment on RTqPCR (p=0.0045 TNF-α, p=0.0002 IL-8) and ELISA (p=0.034 TNF-α, p=0.0002 IL-8) suggesting a heightened inflammatory response to a second hit.

Conclusion

Intestinal tissue resected from neonates with NEC has an elevated hyperinflammatory response compared to neonates recovered from NEC and neonates without NEC. Enteroids generated from patients that have recovered from NEC have a heightened inflammatory response in response to NEC inducing stimuli compared to controls. This tendency towards an increased hyperinflammatory state may be correlated with an infant's proclivity to develop NEC and demonstrates the significance of a second hit on this tissue creating a heightened inflammatory response. This could be correlated with the impact and trajectory of an illness post recovery from NEC.

Research Models to Mimic Necrotizing Enterocolitis and Inflammatory Bowel Diseases: Focus on Extracellular Vesicles Action

This review focuses on the crucial role of the intestinal epithelium in maintaining intestinal homeostasis and its significance in the pathogenesis of necrotizing enterocolitis (NEC) and inflammatory bowel diseases (IBD). NEC is a devastating neonatal disease, while IBD represents a global healthcare problem with increasing incidence. The breakdown of the intestinal barrier in neonates is considered pivotal in the development and progression of both disorders. This review provides an overview of the current state of in vitro, ex vivo, and animal models to study epithelial injury in NEC and IBD, addressing pertinent questions that engage clinicians and researchers alike. Despite significant advancements in early recognition and aggressive treatment, no single therapy has been conclusively proven effective in reducing the severity of these disorders. Although early interventions have improved clinical outcomes, NEC and IBD continue to impose substantial morbidity, mortality, and economic burdens on affected individuals and society. Consequently, exploring alternative therapeutic options capable of preventing and treating the sequelae of NEC and IBD has become a pressing necessity. In recent decades, extracellular vehicles (EVs) have emerged as a potential solution to modulate the pathogenic mechanism in these multifactorial and complex disorders. Despite the diverse array of proposed models, a comprehensive model to investigate and decelerate the progression of NEC and IBD remains to be established. To bridge the translational gap between preclinical studies and clinical applications, enhancements in the technical development of gut-on-a-chip models and EVs hold considerable promise.

Persistent Proclivity to a Proinflammatory State in a Human Enteroid Model of Necrotizing Enterocolitis

Background: Necrotizing enterocolitis (NEC) is a devastating disease of premature neonates with substantial morbidity and mortality. Necrotizing enterocolitis is associated with prematurity, a hyperinflammatory response, and dysregulation of intestinal barrier function. We hypothesize that patients with NEC will have an increased hyperinflammatory intestinal response compared with those without NEC. Patients and Methods: Enteroids were generated from intestinal tissue from neonates undergoing resection. They were treated with 100 mcg/mL lipopolysaccharide (LPS), subjected to 24 hours of hypoxia inducing experimental NEC, then compared with untreated controls. Expression of tumor necrosis factor (TNF-α) and interleukin 8 (IL-8) were evaluated via reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) to measure inflammatory response. Analysis of variance (ANOVA) determined statistical significance (p < 0.05). Results: Treated NEC-derived enteroids expressed significantly higher levels of IL-8 (RT-qPCR, p = 0.003; ELISA, p = 0.0002) compared with untreated NEC-derived enteroids with an increase in inflammatory marker concentration in those with a greater degree of prematurity (ELISA, p = 0.0015). A higher level of IL-8 was seen in NEC-derived enteroids compared with control after treatment (RT-qPCR, p = 0.024). Tumor necrosis factor-α levels were elevated in treated NEC-derived enteroids compared with untreated NEC-derived enteroids (RT-qPCR, p = 0.006; ELISA, p = 0.002) and compared with treated non-NEC-derived enteroids (RT-qPCR, p = 0.025; ELISA, p < 0.0001). Conclusions: Enteroids generated from neonates with NEC have an elevated hyperinflammatory response in response to NEC-inducing stimuli compared with controls. Enteroids generated from neonates with NEC with a greater degree of prematurity have a larger increase in inflammatory markers. This tendency toward a hyperinflammatory state may be correlated with an infant's proclivity to develop NEC and further demonstrates the hyperinflammatory state of prematurity.

Apical-Out Enteroids as an Innovative Model for Necrotizing Enterocolitis

INTRODUCTION

Necrotizing enterocolitis (NEC) is a gastrointestinal disease of premature neonates. We previously validated a NEC enteroid model derived from human infant intestinal tissue. Typical enteroid configuration is basolateral-out (BO) without direct access to the luminal (apical) surface. Apical access is necessary to allow physiologic comparison of pathogen interaction with the intestinal epithelial barrier. We hypothesize that apical-out (AO) enteroids will provide a relevant NEC model to study this relationship.

METHODS

Following the institutional review board approval (#11610-11611), neonatal intestinal tissue was collected from surgical specimens. Stem cells were collected; enteroids were generated and grown to maturity in BO conformation then everted to AO. Enteroids were untreated or treated for 24 h with 100 μg/mL lipopolysaccharide and hypoxia. Protein and gene expression were analyzed for inflammatory markers, tight junction (TJ) proteins and permeability characteristic of NEC.

RESULTS

Apical TJ protein zonula occludens-1 and basolateral protein β-catenin immunofluorescence confirmed AO configuration. Treated AO enteroids had significantly increased messenger RNA (P = 0.001) and protein levels (P < 0.0001) of tumor necrosis factor-α compared to controls. Corrected total cell fluorescence of toll-like receptor 4 was significantly increased in treated AO enteroids compared to control (P = 0.002). Occludin was found to have significantly decreased messenger RNA in treated AO enteroids (P = 0.003). Expression of other TJ proteins claudins-1, -4 and zonula occludens-1 was significantly decreased in treated AO enteroids (P < 0.05).

CONCLUSIONS

AO enteroids present an innovative model for NEC with increased inflammation and gut barrier restructuring. This model allows for a biologically relevant investigation of the interaction between the pathogen and the intestinal epithelial barrier in NEC.

Understanding disruption of the gut barrier during inflammation: Should we abandon traditional epithelial cell lines and switch to intestinal organoids?

Disruption of the intestinal epithelial barrier is a hallmark of mucosal inflammation. It increases exposure of the immune system to luminal microbes, triggering a perpetuating inflammatory response. For several decades, the inflammatory stimuli-induced breakdown of the human gut barrier was studied in vitro by using colon cancer derived epithelial cell lines. While providing a wealth of important data, these cell lines do not completely mimic the morphology and function of normal human intestinal epithelial cells (IEC) due to cancer-related chromosomal abnormalities and oncogenic mutations. The development of human intestinal organoids provided a physiologically-relevant experimental platform to study homeostatic regulation and disease-dependent dysfunctions of the intestinal epithelial barrier. There is need to align and integrate the emerging data obtained with intestinal organoids and classical studies that utilized colon cancer cell lines. This review discusses the utilization of human intestinal organoids to dissect the roles and mechanisms of gut barrier disruption during mucosal inflammation. We summarize available data generated with two major types of organoids derived from either intestinal crypts or induced pluripotent stem cells and compare them to the results of earlier studies with conventional cell lines. We identify research areas where the complementary use of colon cancer-derived cell lines and organoids advance our understanding of epithelial barrier dysfunctions in the inflamed gut and identify unique questions that could be addressed only by using the intestinal organoid platforms.