Intestinal Stem Cell Function Research Articles

Lgr5+ intestinal stem cells are required for organoid survival after genotoxic injury.

Progenitors and mature cells can maintain the intestinal epithelium by dedifferentiation and facultative intestinal stem cell (fISC) function when active ISCs (aISCs) are lost to damage. Here, we modeled fISC activation in intestinal organoids with doxorubicin (DXR), a chemotherapeutic known to ablate Lgr5+ aISCs in vivo. Similar fISC gene activation was observed between organoids treated with low vs high DXR, despite significantly decreased survival at the higher dose. aISCs exhibit dose-dependent loss after DXR but survive at doses compatible with organoid survival. We ablated residual aISCs after DXR using a Lgr52A-DTR allele and observed that aISC survival of the initial genotoxic insult is required for organoid survival following DXR. These results suggest that while typical fISC genes are activated by DXR injury in organoids, functional stemness remains dependent on the aISC pool. Finally, we show that human intestinal organoids require higher doses of DXR to induce loss of survival and downregulation of LGR5. Our data establish a reproducible model of DXR injury in intestinal organoids and reveal differences in in vitro responses to an established in vivo damage modality.

Gelsolin regulates intestinal stem cell regeneration and Th17 cellular function

Intestinal stem cells (ISCs) are responsible for intestinal homeostasis and are important for the regeneration of damaged intestine. We established an ionizing radiation (IR)-induced intestinal injury model and observed that Gelsolin KO mice had increased radiosensitivity. The deletion of Gelsolin aggravated intestinal damage and reduced the number of ISCs after lethal IR. The intestinal organoid experiments showed that Gelsolin deletion inhibited ISCs function after IR. Notably, RNA sequencing and RT-PCR results showed IL-17 signaling pathway was down-regulated and Th17 cells differentiation was inhibited in Gelsolin KO mice. Moreover, recombinant IL-17 A ameliorated IR-induced intestinal injury and promoted ISCs regeneration. To figure out the role of Gelsolin in Th17 cells differentiation, flow cytometry was used and we found that Gelsolin targets Th17 cells functionality via the p-STAT3/RORγt axis. By establishing the co-culture system, we proved that Th17 cells promoted self-renewal and budding abilities in Gelsolin-deficient organoids. Finally, we found that Gelsolin was protective against DSS-induced colitis and that this protective effect was not specific or limited to the IR induced intestinal injury model. Based on these results, we proved Gelsolin maintained the regeneration of ISCs by sustaining Th17 cells functions via the p-STAT3/RORγt axis.Graphical abstract

Dietary titanium dioxide nanoparticles impair intestinal epithelial regeneration by perturbating the function of intestinal stem cells

Intestinal health is closely linked to intestinal stem cells (ISCs), which are highly sensitive to the harmful substances in the lumen. However, there is limited knowledge regarding the effects of food additives on ISCs. This study aims to investigate the impact of dietary titanium dioxide nanoparticles (TiO2 NPs) compared with titanium dioxide microparticles (TiO2 MPs) on intestinal health associated with ISCs in response to dextran sodium sulfate (DSS)-induced enteritis in mice, as well as the related mechanism. We found that exposure to 1% (w/w) TiO2 NPs aggravated DSS-induced enteritis in mice, while this effect could not be observed under exposure to TiO2 MPs. Additionally, 1% (w/w) TiO2 NPs exposure under DSS-induced enteritis worsened the ISC-mediated regeneration of intestinal epithelium by decreasing the epithelial cell proliferation and epithelial turnover rate while increasing epithelial cell death. Meanwhile, using a 3D intestinal organoid model, we discovered that 20 μg/mL TiO2 NPs impaired ISC function and disrupted ISC fate specification both ex vivo and in vitro. Furthermore, TiO2 NPs hindered the nuclear translocation of β-catenin, reducing the overall output of Wnt signaling. Together, TiO2 NPs deteriorated the intestinal epithelial regeneration of mice with DSS-induced enteritis by perturbating ISC function and fate specification through a mechanism involving Wnt signaling. These findings highlight the adverse effect of dietary TiO2 NPs on ISCs and shed light on the particle size optimization of TiO2 food additive.

Regulation of Mitochondrial Quality Control of Intestinal Stem Cells in Homeostasis and Diseases.

Significance: Intestinal stem cells (ISCs) are crucial for the continuous renewal and regeneration of the small intestinal epithelium. ISC fate decisions are strictly controlled by metabolism. Mitochondria act as the central hubs of energetic metabolism and dynamically remodel their morphology to perform required metabolic functions. Mitochondrial dysfunction is closely associated with a variety of gastrointestinal diseases. Recent Advances: In recent years, several studies have reported that mitochondria are potential therapeutic targets for regulating ISC function to alleviate intestinal diseases. However, how mitochondrial quality control mediates ISCs under physiological conditions and protects against intestinal injury remains to be comprehensively reviewed. Critical Issues: In this review, we summarize the available studies about how mitochondrial metabolism, redox state, dynamics, autophagy, and proteostasis impact ISC proliferation, differentiation, and regeneration, respectively. Future Directions: We propose that remodeling the function of mitochondria in ISCs may be a promising potential future direction for the treatment of intestinal diseases. This review may provide new strategies for therapeutically targeting the mitochondria of ISCs in intestinal diseases.

1,25-Dihydroxyvitamin D Enhances the Regenerative Function of Lgr5+ Intestinal Stem Cells In Vitro and In Vivo.

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder in the intestines without a cure. Current therapies suppress inflammation to prevent further intestinal damage. However, healing already damaged intestinal epithelia is still an unmet medical need. Under physiological conditions, Lgr5+ intestinal stem cells (ISCs) in the intestinal crypts replenish the epithelia every 3-5 days. Therefore, understanding the regulation of Lgr5+ ISCs is essential. Previous data suggest vitamin D signaling is essential to maintain normal Lgr5+ ISC function in vivo. Our recent data indicate that to execute its functions in the intestines optimally, 1,25(OH)2D requires high concentrations that, if present systemically, can cause hypercalcemia (i.e., blood calcium levels significantly higher than physiological levels), leading to severe consequences. Using 5-bromo-2'-deoxyuridine (BrdU) to label the actively proliferating ISCs, our previous data suggested that de novo synthesized locally high 1,25(OH)2D concentrations effectively enhanced the migration and differentiation of ISCs without causing hypercalcemia. However, although sparse in the crypts, other proliferating cells other than Lgr5+ ISCs could also be labeled with BrdU. This current study used high-purity Lgr5+ ISC lines and a mouse strain, in which Lgr5+ ISCs and their progeny could be specifically tracked, to investigate the effects of de novo synthesized locally high 1,25(OH)2D concentrations on Lgr5+ ISC function. Our data showed that 1,25(OH)2D at concentrations significantly higher than physiological levels augmented Lgr5+ ISC differentiation in vitro. In vivo, de novo synthesized locally high 1,25(OH)2D concentrations significantly elevated local 1α-hydroxylase expression, robustly suppressed experimental colitis, and promoted Lgr5+ ISC differentiation. For the first time, this study definitively demonstrated 1,25(OH)2D's role in Lgr5+ ISCs, underpinning 1,25(OH)2D's promise in IBD therapy.

Impaired intestinal FXR signaling is involved in aberrant stem cell function leading to intestinal failure-associated liver disease in pediatric patients with short bowel syndrome.

Intestinal failure-associated liver disease (IFALD) is a serious complication of long-term parenteral nutrition in patients with short bowel syndrome (SBS), and is the main cause of death in SBS patients. Prevention of IFALD is one of the major challenges in the treatment of SBS. Impairment of intestinal barrier function is a key factor in triggering IFALD, therefore promoting intestinal repair is particularly important. Intestinal repair mainly relies on the function of intestinal stem cells (ISC), which require robust mitochondrial fatty acid oxidation (FAO) for self-renewal. Herein, we report that aberrant LGR5+ ISC function in IFALD may be attributed to impaired farnesoid X receptor (FXR) signaling, a transcriptional factor activated by steroids and bile acids. In both surgical biopsies and patient-derived organoids (PDOs), SBS patients with IFALD represented lower population of LGR5+ cells and decreased FXR expression. Moreover, treatment with T-βMCA in PDOs (an antagonist for FXR) dose-dependently reduced the population of LGR5+ cells and the proliferation rate of enterocytes, concomitant with decreased key genes involved in FAO including CPT1a. Interestingly, however, treatment with Tropifexor in PDOs (an agonist for FXR) only enhanced FAO capacity, without improvement in ISC function and enterocyte proliferation. In conclusion, these findings suggested that impaired FXR may accelerate the depletion of LGR5 + ISC population through disrupted FAO processes, which may serve as a new potential target of preventive interventions against IFALD for SBS patients.

Enteroendocrine cells regulate intestinal homeostasis and epithelial function

Enteroendocrine cells (EECs) are well-known for their systemic hormonal effects, especially in the regulation of appetite and glycemia. Much less is known about how the products made by EECs regulate their local environment within the intestine. Here, we focus on paracrine interactions between EECs and other intestinal cells as they regulate three essential aspects of intestinal homeostasis and physiology: 1) intestinal stem cell function and proliferation; 2) nutrient absorption; and 3) mucosal barrier function. We also discuss the ability of EECs to express multiple hormones, describe in vitro and in vivo models to study EECs, and consider how EECs are altered in GI disease.

MTGR1 is required to maintain small intestinal stem cell populations

Undifferentiated intestinal stem cells (ISCs) are crucial for maintaining homeostasis and resolving injury. Lgr5+ cells in the crypt base constantly divide, pushing daughter cells upward along the crypt axis where they differentiate into specialized cell types. Coordinated execution of complex transcriptional programs is necessary to allow for the maintenance of undifferentiated stem cells while permitting differentiation of the wide array of intestinal cells necessary for homeostasis. Previously, members of the myeloid translocation gene (MTG) family have been identified as transcriptional co-repressors that regulate stem cell maintenance and differentiation programs in multiple organ systems, including the intestine. One MTG family member, myeloid translocation gene related 1 (MTGR1), has been recognized as a crucial regulator of secretory cell differentiation and response to injury. However, whether MTGR1 contributes to the function of ISCs has not yet been examined. Here, using Mtgr1−/− mice, we have assessed the effects of MTGR1 loss specifically in ISC biology. Interestingly, loss of MTGR1 increased the total number of cells expressing Lgr5, the canonical marker of cycling ISCs, suggesting higher overall stem cell numbers. However, expanded transcriptomic and functional analyses revealed deficiencies in Mtgr1-null ISCs, including deregulated ISC-associated transcriptional programs. Ex vivo, intestinal organoids established from Mtgr1-null mice were unable to survive and expand due to aberrant differentiation and loss of stem and proliferative cells. Together, these results indicate that the role of MTGR1 in intestinal differentiation is likely stem cell intrinsic and identify a novel role for MTGR1 in maintaining ISC function.

Lactoferrin promotes intestinal stem cell‐mediated epithelial regeneration by activating Wnt signaling

AbstractNutritional intervention can greatly benefit people who suffer from side effects of medical treatments by improving intestinal post‐damage recovery. The recovery process is dependent on the regeneration of intestinal epithelial cells, which is driven by Lgr5+ intestinal stem cells (ISCs). Lactoferrin (LF) is a natural milk‐abundant protein with several gut health‐related functions such as antibacterial and immunoregulation activities, thus protecting intestine from damage. However, it is unclear whether LF also plays a role in the repair of the injured intestine, despite limited clues on its ability to modulate intestinal epithelial cell growth in vitro. Here, we show that LF accelerates intestinal epithelial recovery after both dextran sulfate sodium challenge on mice and TNF‐α treatment on intestinal organoids. Furthermore, we find LF gives rise to ISC‐mediated epithelial regeneration by directly activating the Lgr5+ stem cells. Finally, we identify Lrp5/Wnt signaling as the key pathway for LF‐enhancing ISC stemness and function. Overall, our study reveals the potential of LF as a nutrient that can be applied to promote intestinal healing.

Natural flavonoid glycosides Chrysosplenosides I & A rejuvenate intestinal stem cell aging via activation of PPARγ signaling

Abstract The decline in intestinal stem cell (ISC) function is a hallmark of aging, contributing to compromised intestinal regeneration and increased incidence of age-associated diseases. Novel therapeutic agents that can rejuvenate aged ISCs are of paramount importance for extending healthspan. Here, we report on the discovery of Chrysosplenosides I and A (CAs 1 & 2), flavonol glycosides from the Xizang medicinal plant Chrysosplenium axillare Maxim., which exhibit potent anti-aging effects on ISCs. Our research, using Drosophila models, reveals that CAs 1 & 2 treatments not only restrain excessive ISC proliferation, thereby preserving intestinal homeostasis, but also extend the lifespan of aging Drosophila. In aged mouse intestinal organoids, CAs 1 & 2 enhance the growth and budding of intestinal organoids, indicating improved regenerative capacity. Mechanistic investigations show that CAs 1 & 2 exert their effects by activating the peroxisome proliferator-activated receptor-gamma (PPARγ) and concurrently inhibiting the epidermal growth factor receptor (EGFR) signaling pathways. Our findings position CAs 1 & 2 as promising candidates for ameliorating ISC aging and suggest that targeting PPARγ, in particular, may offer a therapeutic strategy to counteract age-related intestinal dysfunction.

Enterococcus-derived tyramine hijacks α2A-adrenergic receptor in intestinal stem cells to exacerbate colitis

Inflammatory bowel disease (IBD) is characterized by dysbiosis of the gut microbiota and dysfunction of intestinal stem cells (ISCs). However, the direct interactions between IBD microbial factors and ISCs are undescribed. Here, we identify α2A-adrenergic receptor (ADRA2A) as a highly expressed GPCR in ISCs. Through PRESTO-Tango screening, we demonstrate that tyramine, primarily produced by Enterococcus via tyrosine decarboxylase (tyrDC), serves as a microbial ligand for ADRA2A. Using an engineered tyrDC-deficient Enterococcus faecalis strain and intestinal epithelial cell-specific Adra2a knockout mice, we show that Enterococcus-derived tyramine suppresses ISC proliferation, thereby impairing epithelial regeneration and exacerbating DSS-induced colitis through ADRA2A. Importantly, blocking the axis with an ADRA2A antagonist, yohimbine, disrupts tyramine-mediated suppression on ISCs and alleviates colitis. Our findings highlight a microbial ligand-GPCR pair in ISCs, revealing a causal link between microbial regulation of ISCs and colitis exacerbation and yielding a targeted therapeutic approach to restore ISC function in colitis.

Host-microbiota interaction in intestinal stem cell homeostasis.

Intestinal stem cells (ISCs) play a pivotal role in gut physiology by governing intestinal epithelium renewal through the precise regulation of proliferation and differentiation. The gut microbiota interacts closely with the epithelium through myriad of actions, including immune and metabolic interactions, which translate into tight connections between microbial activity and ISC function. Given the diverse functions of the gut microbiota in affecting the metabolism of macronutrients and micronutrients, dietary nutrients exert pronounced effects on host-microbiota interactions and, consequently, the ISC fate. Therefore, understanding the intricate host-microbiota interaction in regulating ISC homeostasis is imperative for improving gut health. Here, we review recent advances in understanding host-microbiota immune and metabolic interactions that shape ISC function, such as the role of pattern-recognition receptors and microbial metabolites, including lactate and indole metabolites. Additionally, the diverse regulatory effects of the microbiota on dietary nutrients, including proteins, carbohydrates, vitamins, and minerals (e.g. iron and zinc), are thoroughly explored in relation to their impact on ISCs. Thus, we highlight the multifaceted mechanisms governing host-microbiota interactions in ISC homeostasis. Insights gained from this review provide strategies for the development of dietary or microbiota-based interventions to foster gut health.

Establishment of Anoxia/cytokine-induced Injury and Regeneration in Colonoids

Intestinal epithelial cells (IECs) play key roles in nutrient absorption and fluid secretion, providing a barrier to protect cells. IECs, derived from intestinal stem cells (ISCs), are crucial in maintaining intestinal homeostasis and regeneration, which is crucial in gastrointestinal diseases such as inflammatory bowel disease (IBD). To study epithelial injury/regeneration, primary cultured colonoids were utilized as a model system to mimic injury. They retain the composition and differentiation of the tissue, making it a suitable model for studying homeostasis and regeneration of ISCs in vitro. Anoxia and proinflammatory cytokines frequently coexist and exacerbate one another during intestinal injury. However, anoxic conditions have been mainly ignored in previous research. Thus, we developed a regeneration model using cytokines/anoxia injury to better recapitulate intestinal inflammation. Colonoids were treated with cytokines TNF-α and IFN-γ (5 ng/μL) in anoxic conditions for 24 hours to provoke an injury. After 24 hours of injury, the colonoids were exposed to normal oxygen and media conditions for regeneration. Regeneration was observed for 24, 48, and 72 hours and documented using photomicrographs. Morphological analysis detailed that injury was most severe 24 hours post-injury with the combined induction of cytokines and anoxia resulting in decreased colonoid area and number of buds compared to control groups. RT-PCR analysis detailed mRNA expression of stem cell markers ( Lgr5, Bmi1, and Hopx), Wnt ( Axin2, Myc2, and Ascl2), and YAP target genes ( Sca1 and Ctgf) were increased at peak injury and returned to pre-injury levels at 72 hours of recovery. Regeneration of the colonoids is consistent with in vivo observations, thus confirming the validity of the model. This versatile model can be used to study responses to injury and regeneration of intestinal epithelium and the function of ISCs with applications in intestinal disease therapeutics. University of Maryland College of Agriculture and Natural Resources and the Maryland Agricultural Experiment Station Undergraduate Research Grant Grant #4307572 from the Maryland Stem Cell Research Fund. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Intestinal Stem Cells Remodel in Response to Acute Notch Inhibition and Paneth Cell Loss

INTRODUCTION: Intestinal epithelial cells are rapidly renewed throughout life by intestinal stem cells (ISCs). ISC function is regulated by niche factors that orchestrate cellular proliferation and differentiation. Of these, Notch signaling is essential for ISC self-renewal and regulates the cell fate choice between absorptive cells (enterocyte) vs secretory (Paneth, goblet, enteroendocrine, and tuft) cells. Yet, the Notch niche is not fully defined. In the mature small intestine, Paneth cells neighbor each ISC and act as Notch niche cells, providing the Notch signal by expressing the Notch ligands DLL1 and DLL4 on their surface. However, studies in mice have shown that ISCs can function in the immature intestine before Paneth cells are formed, and when Paneth cells are depleted in the adult intestine. We previously observed that acute Notch inhibition via the inhibitor dibenzazepine (DBZ) resulted in Paneth cell apoptosis with intact ISCs displaying transient dysfunction. Here, we aimed to define the Notch niche after Paneth cell apoptosis in adult mice and in the developing intestine. We hypothesized that during acute Notch inhibition, ISCs remodel to compensate for Paneth cell loss by activating Notch ligand expression, and that this remodeling mimics the state of immature ISCs prior to Paneth cell emergence. METHODS: We isolated Lgr5+ ISCs by FACS from Lgr5-GFP-CreERT2 mice 24 hours after DBZ or vehicle treatment and performed bulk RNAseq analysis. To define the Notch niche during development, we analyzed postnatal intestines from Notch ligand reporter mice (Dll1-mCherry and Dll4-mCherry) crossed with the ISC reporter mice (Lgr5-GFP-CreERT2). RESULTS: ISCs isolated from Paneth cell-depleted intestines upregulated expression of Notch ligands Dll4 and Dll4 and various secretory cell markers, with expected downregulation of Notch target genes, but no alteration of other stem cell genes. This suggests that after acute Notch inhibition, Lgr5+ ISCs maintain partial stem cell identity while acquiring a signature resembling that of secretory progenitors. In the immature intestine, we showed by immunohistology that sporadic cells expressing secretory cell markers (LYZ, MUC2, and CHGA) localized to the intervillus region and co-stained with Dll1- or Dll4-mCherry+. This suggests that multiple differentiated cell types could provide the Notch signal to immature ISCs. We also observed occasional Lgr5-GFP+ ISCs that were co-positive for Dll1-mCherry, suggesting that immature ISCs can express Notch ligands at homeostasis. Further experimentation will determine whether these Dll1+ ISCs are similar to the remodeled adult ISCs after Paneth cell depletion. CONCLUSIONS: Acute Notch inhibition directly remodels ISCs to express the Notch ligands, Dll1 and Dll4 in the adult intestine. In the immature intestine, multiple secretory cell types appear to comprise the immature Notch niche. This project was funded by NIH R01 DK118023 awarded to Dr. Linda Samuelson. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Claudin-7 is essential for the maintenance of colonic stem cell homoeostasis via the modulation of Wnt/Notch signalling

Intestinal stem cells (ISCs) play a crucial role in the continuous self-renewal and recovery of the intestinal epithelium. In previous studies, we have revealed that the specific absence of Claudin-7 (Cldn-7) in intestinal epithelial cells (IECs) can lead to the development of spontaneous colitis. However, the mechanisms by which Cldn-7 maintains homeostasis in the colonic epithelium remain unclear. Therefore, in the present study, we used IEC- and ISC-specific Cldn-7 knockout mice to investigate the regulatory effects of Cldn-7 on colonic Lgr5+ stem cells in the mediation of colonic epithelial injury and repair under physiological and inflammatory conditions. Notably, our findings reveal that Cldn-7 deletion disrupts the self-renewal and differentiation of colonic stem cells alongside the formation of colonic organoids in vitro. Additionally, these Cldn-7 knockout models exhibited heightened susceptibility to experimental colitis, limited epithelial repair and regeneration, and increased differentiation toward the secretory lineage. Mechanistically, we also established that Cldn-7 facilitates the proliferation, differentiation, and organoid formation of Lgr5+ stem cells through the maintenance of Wnt and Notch signalling pathways in the colonic epithelium. Overall, our study provides new insights into the maintenance of ISC function and colonic epithelial homoeostasis.

Colonic crypt stem cell functions are controlled by tight junction protein claudin-7 through Notch/Hippo signaling.

The tight junction protein claudin-7 is essential for tight junction function and intestinal homeostasis. Cldn7 deletion in mice leads to an inflammatory bowel disease-like phenotype exhibiting severe intestinal epithelial damage, weight loss, inflammation, mucosal ulcerations, and epithelial hyperplasia. Claudin-7 has also been shown to be involved in cancer metastasis and invasion. Here, we test our hypothesis that claudin-7 plays an important role in regulating colonic intestinal stem cell function. Conditional knockout of Cldn7 in the colon led to impaired epithelial cell differentiation, hyperproliferative epithelium, a decrease in active stem cells, and dramatically altered gene expression profiles. In 3D colonoid culture, claudin-7-deficient crypts were unable to survive and form spheroids, emphasizing the importance of claudin-7 in stem cell survival. Inhibition of the Hippo pathway or activation of Notch signaling partially rescued the defective stem cell behavior. Concurrent Notch activation and Hippo inhibition resulted in restored colonoid survival, growth, and differentiation to the level comparable to those of wild-type derived crypts. In this study, we highlight the essential role of claudin-7 in regulating Notch and Hippo signaling-dependent colonic stem cell functions, including survival, self-renewal, and differentiation. These new findings may shed light on potential avenues to explore for drug development in colorectal cancer.

DHX9 maintains epithelial homeostasis by restraining R-loop-mediated genomic instability in intestinal stem cells

Epithelial barrier dysfunction and crypt destruction are hallmarks of inflammatory bowel disease (IBD). Intestinal stem cells (ISCs) residing in the crypts play a crucial role in the continuous self-renewal and rapid recovery of intestinal epithelial cells (IECs). However, how ISCs are dysregulated in IBD remains poorly understood. Here, we observe reduced DHX9 protein levels in IBD patients, and mice with conditional DHX9 depletion in the intestinal epithelium (Dhx9ΔIEC) exhibit an increased susceptibility to experimental colitis. Notably, Dhx9ΔIEC mice display a significant reduction in the numbers of ISCs and Paneth cells. Further investigation using ISC-specific or Paneth cell-specific Dhx9-deficient mice demonstrates the involvement of ISC-expressed DHX9 in maintaining epithelial homeostasis. Mechanistically, DHX9 deficiency leads to abnormal R-loop accumulation, resulting in genomic instability and the cGAS-STING-mediated inflammatory response, which together impair ISC function and contribute to the pathogenesis of IBD. Collectively, our findings highlight R-loop-mediated genomic instability in ISCs as a risk factor in IBD.

Intestinal Inflammation and Regeneration-Interdigitating Processes Controlled by Dietary Lipids in Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a disease of chronic inflammatory conditions of the intestinal tract due to disturbance of the inflammation and immune system. Symptoms of IBD include abdominal pain, diarrhea, bleeding, reduced weight, and fatigue. In IBD, the immune system attacks the intestinal tract's inner wall, causing chronic inflammation and tissue damage. In particular, interlukin-6 and interlukin-17 act on immune cells, including T cells and macrophages, to amplify the immune responses so that tissue damage and morphological changes occur. Of note, excessive calorie intake and obesity also affect the immune system due to inflammation caused by lipotoxicity and changes in lipids supply. Similarly, individuals with IBD have alterations in liver function after sustained high-fat diet feeding. In addition, excess dietary fat intake, along with alterations in primary and secondary bile acids in the colon, can affect the onset and progression of IBD because inflammatory cytokines contribute to insulin resistance; the factors include the release of inflammatory cytokines, oxidative stress, and changes in intestinal microflora, which may also contribute to disease progression. However, interfering with de novo fatty acid synthase by deleting the enzyme acetyl-CoA-carboxylase 1 in intestinal epithelial cells (IEC) leads to the deficiency of epithelial crypt structures and tissue regeneration, which seems to be due to Lgr5+ intestinal stem cell function. Thus, conflicting reports exist regarding high-fat diet effects on IBD animal models. This review will focus on the pathological basis of the link between dietary lipids intake and IBD and will cover the currently available pharmacological approaches.

P53 suppresses MHC class II presentation by intestinal epithelium to protect against radiation-induced gastrointestinal syndrome

Radiation-induced gastrointestinal syndrome is a major complication and limiting factor for radiotherapy. Tumor suppressor p53 has a protective role in radiation-induced gastrointestinal toxicity. However, its underlying mechanism remains unclear. Here we report that regulating the IL12-p40/MHC class II signaling pathway is a critical mechanism by which p53 protects against radiation-induced gastrointestinal syndrome. p53 inhibits the expression of inflammatory cytokine IL12-p40, which in turn suppresses the expression of MHC class II on intestinal epithelial cells to suppress T cell activation and inflammation post-irradiation that causes intestinal stem cell damage. Anti-IL12-p40 neutralizing antibody inhibits inflammation and rescues the defects in intestinal epithelial regeneration post-irradiation in p53-deficient mice and prolongs mouse survival. These results uncover that the IL12-p40/MHC class II signaling mediates the essential role of p53 in ensuring intestinal stem cell function and proper immune reaction in response to radiation to protect mucosal epithelium, and suggest a potential therapeutic strategy to protect against radiation-induced gastrointestinal syndrome.

Fut2 Deficiency Promotes Intestinal Stem Cell Aging by Damaging Mitochondrial Functions via Down-Regulating α1,2-Fucosylation of Asah2 and Npc1.

Fut2-mediated α1,2-fucosylation is important for gut homeostasis, including the intestinal stem cell (ISC). The stemness of ISC declines with age, and aging-associated ISC dysfunction is closely related to many age-related intestinal diseases. We previously found intestinal epithelial dysfunction in some aged Fut2 knockout mice. However, how Fut2-mediated α1,2-fucosylation affects ISC aging is still unknown. On this basis, the herein study aims to investigate the role of Fut2-mediated α1,2-fucosylation in ISC aging. Aging models in ISC-specific Fut2 knockout mice were established. ISCs were isolated for proteomics and N-glycoproteomics analysis. ISC functions and mitochondrial functions were examined in mice and organoids. Ulex europaeus agglutinin I chromatography and site-directed mutagenesis were used to validate the key target fucosylated proteins of Fut2. As a result, Fut2 knockout impaired ISC stemness and promoted aging marker expression in aged mice. Proteomics analysis indicated mitochondrial dysfunction in Fut2 knockout ISC. More injured mitochondria, elevated levels of reactive oxygen species, and decreased levels of adenosine 5'-triphosphate (ATP) in Fut2 knockout ISC were found. Moreover, respiratory chain complex impairment and mitophagy dysfunction in Fut2 knockout ISC were further noted. Finally, Fut2 was demonstrated to regulate mitochondrial functions mainly by regulating the α1,2-fucosylation of N-acyl sphingosine amidohydrolase 2 (Asah2) and Niemann-Pick type C intracellular cholesterol transporter 1 (Npc1). In conclusion, this study demonstrated the substantial role of Fut2 in regulating ISC functions during aging by affecting mitochondrial function. These findings provide novel insights into the molecular mechanisms of ISC aging and therapeutic strategies for age-related intestinal diseases.