Breast Milk Enhances Growth of Enteroids: An Ex Vivo Model of Cell Proliferation

Research progress on the relationship between Paneth cells-susceptibility genes, intestinal microecology and inflammatory bowel disease

Inflammatory bowel disease (IBD) is a disorder of the immune system and intestinal microecosystem caused by environmental factors in genetically susceptible people. Paneth cells (PCs) play a central role in IBD pathogenesis, especially in Crohn's disease development, and their morphology, number and function are regulated by susceptibility genes. In the intestine, PCs participate in the formation of the stem cell microenvironment by secreting antibacterial particles and play a role in helping maintain the intestinal microecology and intestinal mucosal homeostasis. Moreover, PC proliferation and maturation depend on symbiotic flora in the intestine. This paper describes the interactions among susceptibility genes, PCs and intestinal microecology and their effects on IBD occurrence and development.

Effects of human donor milk on gut barrier function and inflammation: in vitro study of the beneficial properties to the newborn

Introduction

The gastrointestinal and immune systems of premature infants are not fully developed, rendering them more vulnerable to severe complications like necrotizing enterocolitis. Human milk offers a rich array of bioactive factors that collectively contribute to reducing the incidence of gut infections and inflammatory conditions. When a mother's milk is unavailable, preterm infants are often provided with donor human milk processed in Human Milk Banks. However, it remains uncertain whether pasteurized milk confers the same level of risk reduction as unprocessed milk. This uncertainty may stem from the well-documented adverse effects of heat treatment on milk composition. Yet, our understanding of the comprehensive impact on protective mechanisms is limited.

Methods

In this study, we conducted a comparative analysis of the effects of raw versus pasteurized milk and colostrum versus mature milk on cellular functions associated with the gut epithelial barrier and responses to inflammatory stimuli. We utilized THP-1 and HT-29 cell lines, representing monocyte/macrophages and gut epithelial cells, respectively.

Results

Our observations revealed that all milk types stimulated epithelial cell proliferation. However, only raw colostrum increased cell migration and interfered with the interaction between E. coli and epithelial cells. Furthermore, the response of epithelial and macrophage cells to lipopolysaccharide (LPS) was enhanced solely by raw colostrum, with a milder effect observed with mature milk. In contrast, both raw and pasteurized milk diminished the LPS induced response in monocytes. Lastly, we examined how milk affected the differentiation of monocytes into macrophages, finding that milk reduced the subsequent inflammatory response of macrophages to LPS.

Discussion

Our study sheds light on the impact of human milk on certain mechanisms that potentially account for its protective effects against necrotizing enterocolitis, highlighting the detrimental influence of pasteurization on some of these mechanisms. Our findings emphasize the urgency of developing alternative pasteurization methods to better preserve milk properties. Moreover, identifying the key components critically affected by these protective mechanisms could enable their inclusion in donor milk or formula, thereby enhancing immunological benefits for vulnerable newborns.

Short-chain fatty acids ameliorate necrotizing enterocolitis-like intestinal injury through enhancing Notch1-mediated single immunoglobulin interleukin-1-related receptor, toll-interacting protein, and A20 induction

Single immunoglobulin interleukin-1-related receptor (SIGIRR), toll-interacting protein (TOLLIP), and A20 are major inhibitors of toll-like receptor (TLR) signaling induced postnatally in the neonatal intestine. Short-chain fatty acids (SCFAs), fermentation products of indigestible carbohydrates produced by symbiotic bacteria, inhibit intestinal inflammation. Herein, we investigated the mechanisms by which SCFAs regulate SIGIRR, A20, and TOLLIP expression and mitigate experimental necrotizing enterocolitis (NEC). Butyrate induced NOTCH activation by repressing sirtuin 1 (SIRT1)-mediated deacetylation of the Notch intracellular domain (NICD) in human intestinal epithelial cells (HIECs). Overexpression of NICD induced SIGIRR, A20, and TOLLIP expression. Chromatin immunoprecipitation revealed that butyrate-induced NICD binds to the SIGIRR, A20, and TOLLIP gene promoters. Notch1-shRNA suppressed butyrate-induced SIGIRR/A20 upregulation in mouse enteroids and HIEC. Flagellin (TLR5 agonist)-induced inflammation in HIEC was inhibited by butyrate in a SIGIRR-dependent manner. Neonatal mice fed butyrate had increased NICD, A20, SIGIRR, and TOLLIP expression in the ileal epithelium. Butyrate inhibited experimental NEC-induced intestinal apoptosis, cytokine expression, and histological injury. Our data suggest that SCFAs can regulate the expression of the major negative regulators of TLR signaling in the neonatal intestine through Notch1 and ameliorate experimental NEC. Enteral SCFAs supplementation in preterm infants provides a promising bacteria-free, therapeutic option for NEC.NEW & NOTEWORTHY Short-chain fatty acids (SCFAs), such as propionate and butyrate, metabolites produced by symbiotic gut bacteria are known to be anti-inflammatory, but the mechanisms by which they protect against NEC are not fully understood. In this study, we reveal that SCFAs regulate intestinal inflammation by inducing the key TLR and IL1R inhibitors, SIGIRR and A20, through activation of the pluripotent transcriptional factor NOTCH1. Butyrate-mediated SIGIRR and A20 induction represses experimental NEC in the neonatal intestine.

Necrotizing Enterocolitis: Overview on In Vitro Models

Necrotizing enterocolitis (NEC) is a gut inflammatory disorder which constitutes one of the leading causes of morbidity and mortality for preterm infants. The pathophysiology of NEC is yet to be fully understood; several observational studies have led to the identification of multiple factors involved in the pathophysiology of the disease, including gut immaturity and dysbiosis of the intestinal microbiome. Given the complex interactions between microbiota, enterocytes, and immune cells, and the limited access to fetal human tissues for experimental studies, animal models have long been essential to describe NEC mechanisms. However, at present there is no animal model perfectly mimicking human NEC; furthermore, the disease mechanisms appear too complex to be studied in single-cell cultures. Thus, researchers have developed new approaches in which intestinal epithelial cells are exposed to a combination of environmental and microbial factors which can potentially trigger NEC. In addition, organoids have gained increasing attention as promising models for studying NEC development. Currently, several in vitro models have been proposed and have contributed to describe the disease in deeper detail. In this paper, we will provide an updated review of available in vitro models of NEC and an overview of current knowledge regarding its molecular underpinnings.

Breast milk stem cells: Are they magic bullets in neonatology?

Each mammal produces milk specific to its newborn that meets all nutritional needs. Breast milk is not only a secretory product but is also a complex liquid containing several components that provide enteral nutrition. The stage of lactation, the fullness of the breast, the feeding of the baby, and the health of the mother during the breastfeeding period cause differences in the composition of breast milk. Although the positive effects of breast milk on the physical and intellectual development of a child in the short and long term have been known for centuries, its mechanism has not been elucidated. Stem cells are defined as the cells that possess specific markers and have not undergone differentiation. Under suitable conditions and stimuli, they can differentiate into desired cells. The detection of stem cells, whose exact origin is not known, in breast milk and their demonstration in the baby's body have prompted the necessity of exploring the possible role of stem cells in the treatment of diseases. In this review, breast milk-derived stem cells and their possible role in neonatology are discussed.

The Role of Human Milk Oligosaccharides and Probiotics on the Neonatal Microbiome and Risk of Necrotizing Enterocolitis: A Narrative Review

Preterm infants are a vulnerable population at risk of intestinal dysbiosis. The newborn microbiome is dominated by Bifidobacterium species, though abnormal microbial colonization can occur by exogenous factors such as mode of delivery, formula feeding, and exposure to antibiotics. Therefore, preterm infants are predisposed to sepsis and necrotizing enterocolitis (NEC), a fatal gastrointestinal disorder, due to an impaired intestinal barrier, immature immunity, and a dysbiotic gut microbiome. Properties of human milk serve as protection in the prevention of NEC. Human milk oligosaccharides (HMOs) and the microbiome of breast milk are immunomodulatory components that provide intestinal homeostasis through regulation of the microbiome and protection of the intestinal barrier. Enteral probiotic supplements have been trialed to evaluate their impact on establishing intestinal homeostasis. Here, we review the protective role of HMOs, probiotics, and synbiotic combinations in protecting a vulnerable population from the pathogenic features associated with necrotizing enterocolitis.

Synchronization of mothers and offspring promotes tolerance and limits allergy

Allergic disorders, characterized by Th2 immune responses to environmental substances, are increasingly common in children in Western societies. Multiple studies indicate that breastfeeding, early complementary introduction of food allergens, and antibiotic avoidance in the first year of life reduces allergic outcomes in at-risk children. Why the benefit of these practices is restricted to early life is largely unknown. We identified a preweaning interval during which dietary antigens are assimilated by the colonic immune system. This interval is under maternal control via temporal changes in breast milk, coincides with an influx of naive T cells into the colon, and is followed by the development of a long-lived population of colonic peripherally derived Tregs (pTregs) that can be specific for dietary antigens encountered during this interval. Desynchronization of mothers and offspring produced durable deficits in these pTregs, impaired tolerance to dietary antigens introduced during and after this preweaning interval, and resulted in spontaneous Th2 responses. These effects could be rescued by pTregs from the periweaning colon or by Tregs generated in vitro using periweaning colonic antigen-presenting cells. These findings demonstrate that mothers and their offspring are synchronized for the development of a balanced immune system.

New directions in necrotizing enterocolitis with early-stage investigators

The 2019 Necrotizing Enterocolitis (NEC) Symposium expanded upon the NEC Society's goals of bringing stakeholders together to discuss cutting-edge science, potential therapeutics and preventative measures, as well as the patient-family perspectives of NEC. The Symposium facilitated discussions and shared knowledge with the overarching goal of creating "A World Without NEC." To accomplish this goal, new research to advance the state of the science is necessary. Over the last decade, several established investigators have significantly improved our understanding of the pathophysiology of NEC and they have paved the way for the next generation of clinician-scientists funded to perform NEC research. This article will serve to highlight the contributions of these young clinician-scientists that seek to elucidate how immune, microbial and nervous system dysregulation contributes to the pathophysiology of NEC.

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.

Maternal activation of the EGFR prevents translocation of gut-residing pathogenic Escherichia coli in a model of late-onset neonatal sepsis

Late-onset sepsis (LOS) is a highly consequential complication of preterm birth and is defined by a positive blood culture obtained after 72 h of age. The causative bacteria can be found in patients' intestinal tracts days before dissemination, and cohort studies suggest reduced LOS risk in breastfed preterm infants through unknown mechanisms. Reduced concentrations of epidermal growth factor (EGF) of maternal origin within the intestinal tract of mice correlated to the translocation of a gut-resident human pathogen Escherichia coli, which spreads systemically and caused a rapid, fatal disease in pups. Translocation of Escherichia coli was associated with the formation of colonic goblet cell-associated antigen passages (GAPs), which translocate enteric bacteria across the intestinal epithelium. Thus, maternally derived EGF, and potentially other EGFR ligands, prevents dissemination of a gut-resident pathogen by inhibiting goblet cell-mediated bacterial translocation. Through manipulation of maternally derived EGF and alteration of the earliest gut defenses, we have developed an animal model of pathogen dissemination which recapitulates gut-origin neonatal LOS.

A comparison of exosomes derived from different periods breast milk on protecting against intestinal organoid injury

AIM OF THE STUDY

Human breast milk reduces the risk and severity of necrotizing enterocolitis (NEC). Exosomes are extracellular vesicles (EVs) found in high concentrations in milk, and they mediate intercellular communication and immune responses. The aim of this study is to compare the protective effects of exosomes that are derived from different time periods of breast milk production against intestinal injury using an ex vivo intestinal organoid model.

METHODS

Colostrum, transitional and mature breast milk samples from healthy lactating mothers were collected. Exosomes were isolated using serial ultracentrifugation and filtration. Exosomes' presence was confirmed using transmission electron microscopy (TEM) and western blot. To form the intestinal organoids, terminal ileum was harvested from neonatal mice pups at postnatal day 9, crypts were isolated and organoids were cultured in matrigel. Organoids were either cultured with exposure to lipopolysaccharide (LPS), or in treatment groups where both LPS and exosomes were added in the culturing medium. Inflammatory markers and organoids viability were evaluated.

MAIN RESULTS

Human milk-derived exosomes were successfully isolated and characterized. LPS administration reduced the size of intestinal organoids, induced inflammation through increasing TNFα and TLR4 expression, and stimulated intestinal regeneration. Colostrum, transitional and mature human milk-derived exosome treatment all prevented inflammatory injury, while exosomes derived from colostrum were most effective at reducing inflammatory cytokine.

CONCLUSIONS

Human breast milk-derived exosomes were able to protect intestine organoids against epithelial injury induced by LPS. Colostrum exosomes offer the best protective effect among the breast-milk derived exosomes. Human milk exosomes can be protective against the development of intestinal injury such as that seen in NEC.

Stem cells in human breast milk

Recent studies have demonstrated that breast milk contains a population of cells displaying many of the properties typical of stem cells. This review outlines progress made in this newly emerging field of stem cell biology and provides an analysis of the available data on purification, propagation and differentiation of certain types of progenitor cells from breast milk. The possible fates of breast milk cells, including microchimerism caused by their transmission to the distant organs of the infant, are also discussed. Unique properties of breast milk-derived stem cells, such as their unusually low tumorigenic potential and their negligible ability to form teratomas, are highlighted as obvious advantages for using these cells in regenerative therapy.

A Novel Human Epithelial Enteroid Model of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a devastating disease of newborn infants. It is characterized by multiple pathophysiologic alterations in the human intestinal epithelium, leading to increased intestinal permeability, impaired restitution, and increased cell death. Although there are numerous animal models of NEC, response to injury and therapeutic interventions may be highly variable between species. Furthermore, it is ethically challenging to study disease pathophysiology or novel therapeutic agents directly in human subjects, especially children. Therefore, it is highly desirable to develop a novel model of NEC using human tissue. Enteroids are 3-dimensional organoids derived from intestinal epithelial cells. They are ideal for the study of complex physiologic interactions, cell signaling, and host-pathogen defense. In this manuscript we describe a protocol that cultures human enteroids after isolating intestinal stem cells from patients undergoing bowel resection. The crypt cells are cultured in media containing growth factors that encourage differentiation into the various cell types native of the human intestinal epithelium. These cells are grown in a synthetic, collagenous mix of proteins that serve as a scaffold, mimicking the extra-cellular basement membrane. As a result, enteroids develop apical-basolateral polarity. Co-administration of lipopolysaccharide (LPS) in media causes an inflammatory response in the enteroids, leading to histologic, genetic, and protein expression alterations similar to those seen in human NEC. An experimental model of NEC using human tissue may provide a more accurate platform for drug and treatment testing prior to human trials, as we strive to identify a cure for this disease.