Vitamin D is a determinant of mouse intestinal Lgr5 stem cell functions

Dietary and metabolic effects on intestinal stem cells in health and disease

Diet and nutritional metabolites exhibit wide-ranging effects on health and disease partly by altering tissue composition and function. With rapidly rising rates of obesity, there is particular interest in how obesogenic diets influence tissue homeostasis and risk of tumorigenesis; epidemiologically, these diets have a positive correlation with various cancers, including colorectal cancer. The gastrointestinal tract is a highly specialized, continuously renewing tissue with a fundamental role in nutrient uptake and is, in turn, influenced by diet composition and host metabolic state. Intestinal stem cells are found at the base of the intestinal crypt and can generate all mature lineages that comprise the intestinal epithelium and are uniquely influenced by host diet, metabolic by-products and energy dynamics. Similarly, tumour growth and metabolism can also be shaped by nutrient availability and host diet. In this Review, we discuss how different diets and metabolic changes influence intestinal stem cells in homeostatic and pathological conditions, as well as tumorigenesis. We also discuss how dietary changes and composition affect the intestinal epithelium and its surrounding microenvironment.

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.

Nutrigenomic underpinnings of intestinal stem cells in inflammatory bowel disease and colorectal cancer development

Food-gene interaction has been identified as a leading risk factor for inflammatory bowel disease (IBD) and colorectal cancer (CRC). Accordingly, nutrigenomics emerges as a new approach to identify biomarkers and therapeutic targets for these two strongly associated gastrointestinal diseases. Recent studies in stem cell biology have further shown that diet and nutrition signal to intestinal stem cells (ISC) by altering nutrient-sensing transcriptional activities, thereby influencing barrier integrity and susceptibility to inflammation and tumorigenesis. This review recognizes the dietary factors related to both CRC and IBD and investigates their impact on the overlapping transcription factors governing stem cell activities in homeostasis and post-injury responses. Our objective is to provide a framework to study the food-gene regulatory network of disease-contributing cells and inspire new nutrigenomic approaches for detecting and treating diet-related IBD and CRC.

Non-stem cell lineages as an alternative origin of intestinal tumorigenesis in the context of inflammation

According to conventional views, colon cancer originates from stem cells. However, inflammation, a key risk factor for colon cancer, has been shown to suppress intestinal stemness. Here, we used Paneth cells as a model to assess the capacity of differentiated lineages to trigger tumorigenesis in the context of inflammation in mice. Upon inflammation, Paneth cell-specific Apc mutations led to intestinal tumors reminiscent not only of those arising in patients with inflammatory bowel disease, but also of a larger fraction of human sporadic colon cancers. The latter is possibly because of the inflammatory consequences of western-style dietary habits, a major colon cancer risk factor. Machine learning methods designed to predict the cell-of-origin of cancer from patient-derived tumor samples confirmed that, in a substantial fraction of sporadic cases, the origins of colon cancer reside in secretory lineages and not in stem cells.

Host-diet-microbiota interplay in intestinal nutrition and health

The intestine is populated by a complex and dynamic assortment of microbes, collectively called gut microbiota, that interact with the host and contribute to its metabolism and physiology. Diet is considered a key regulator of intestinal microbiota, as ingested nutrients interact with and shape the resident microbiota composition. Furthermore, recent studies underscore the interplay of dietary and microbiota-derived nutrients, which directly impinge on intestinal stem cells regulating their turnover to ensure a healthy gut barrier. Although advanced sequencing methodologies have allowed the characterization of the human gut microbiome, mechanistic studies assessing diet-microbiota-host interactions depend on the use of genetically tractable models, such as Drosophila melanogaster. In this review, we first discuss the similarities between the human and fly intestines and then we focus on the effects of diet and microbiota on nutrient-sensing signaling cascades controlling intestinal stem cell self-renewal and differentiation, as well as disease. Finally, we underline the use of the Drosophila model in assessing the role of microbiota in gut-related pathologies and in understanding the mechanisms that mediate different whole-body manifestations of gut dysfunction.

Nutrient metabolism in regulating intestinal stem cell homeostasis

Intestinal stem cells (ISCs) are known for their remarkable proliferative capacity, making them one of the most active cell populations in the body. However, a high turnover rate of intestinal epithelium raises the likelihood of dysregulated homeostasis, which is known to cause various diseases, including cancer. Maintaining precise control over the homeostasis of ISCs is crucial to preserve the intestinal epithelium's integrity during homeostasis or stressed conditions. Recent research has indicated that nutrients and metabolic pathways can extensively modulate the fate of ISCs. This review will explore recent findings concerning the influence of various nutrients, including lipids, carbohydrates, and vitamin D, on the delicate balance between ISC proliferation and differentiation.

From molecular basis to clinical insights: a challenging future for the vitamin D endocrine system in colorectal cancer

Colorectal cancer (CRC) is one of the most life-threatening neoplasias in terms of incidence and mortality worldwide. Vitamin D deficiency has been associated with an increased risk of CRC. 1α,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the most active vitamin D metabolite, is a pleiotropic hormone that, through its binding to a transcription factor of the nuclear receptor superfamily, is a major regulator of the human genome. 1,25(OH)2D3 acts on colon carcinoma and stromal cells and displays tumor protective actions. Here, we review the variety of molecular mechanisms underlying the effects of 1,25(OH)2D3 in CRC, which affect multiple processes that are dysregulated during tumor initiation and progression. Additionally, we discuss the epidemiological data that associate vitamin D deficiency and CRC, and the most relevant randomized controlled trials of vitamin D3 supplementation conducted in both healthy individuals and CRC patients.

Vitamin D opposes multilineage cell differentiation induced by Notch inhibition and BMP4 pathway activation in human colon organoids

Understanding the mechanisms involved in colonic epithelial differentiation is key to unraveling the alterations causing inflammatory conditions and cancer. Organoid cultures provide an unique tool to address these questions but studies are scarce. We report a differentiation system toward enterocytes and goblet cells, the two major colonic epithelial cell lineages, using colon organoids generated from healthy tissue of colorectal cancer patients. Culture of these organoids in medium lacking stemness agents resulted in a modest ultrastructural differentiation phenotype with low-level expression of enterocyte (KLF4, KRT20, CA1, FABP2) and goblet cell (TFF2, TFF3, AGR2) lineage markers. BMP pathway activation through depletion of Noggin and addition of BMP4 resulted in enterocyte-biased differentiation. Contrarily, blockade of the Notch pathway using the γ-secretase inhibitor dibenzazepine (DBZ) favored goblet cell differentiation. Combination treatment with BMP4 and DBZ caused a balanced strong induction of both lineages. In contrast, colon tumor organoids responded poorly to BMP4 showing only weak signals of cell differentiation, and were unresponsive to DBZ. We also investigated the effects of 1α,25-dihydroxyvitamin D3 (calcitriol) on differentiation. Calcitriol attenuated the effects of BMP4 and DBZ on colon normal organoids, with reduced expression of differentiation genes and phenotype. Consistently, in normal organoids, calcitriol inhibited early signaling by BMP4 as assessed by reduction of the level of phospho-SMAD1/5/8. Our results show that BMP and Notch signaling play key roles in human colon stem cell differentiation to the enterocytic and goblet cell lineages and that calcitriol modulates these processes favoring stemness features.

Intestinal stem cells: guardians of homeostasis in health and aging amid environmental challenges

The intestinal epithelium is the first line of defense and acts as an interface between the vast microbial world within the gastrointestinal tract and the body's internal milieu. The intestinal epithelium not only facilitates nutrient absorption but also plays a key role in defending against pathogens and regulating the immune system. Central to maintaining a healthy epithelium are intestinal stem cells (ISCs), which are essential for replenishing the intestinal epithelium throughout an individual's lifespan. Recent research has unveiled the intricate interplay between ISCs and their niche, which includes various cell types, extracellular components, and signaling molecules. In this review, we delve into the most recent advances in ISC research, with a focus on the roles of ISCs in maintaining mucosal homeostasis and how ISC functionality is influenced by the niche environment. In this review, we explored the regulatory mechanisms that govern ISC behavior, emphasizing the dynamic adaptability of the intestinal epithelium in the face of various challenges. Understanding the intricate regulation of ISCs and the impact of aging and environmental factors is crucial for advancing our knowledge and developing translational approaches. Future studies should investigate the interactive effects of different risk factors on intestinal function and develop strategies for improving the regenerative capacity of the gut.

Vitamin D3 induces stem cell activation via Lgr5-Bmi1 expression and improving mouse colitis histology index

Conventional therapy for inflammatory bowel disease using long-term anti-inflammatory drugs does not seem to provide optimal results. Adjuvant therapy using vitamin D3 is believed to have an essential role in repairing the colonic mucosa through the activation of colonic stem cells. The aim of this study was to demonstrate the effect of vitamin D3 in mucosal repair through stem cell activation, marked by leucin-rich repeat-containing G protein-coupled receptor 5 (Lgr5) and B lymphoma Mo-MLV insertion region 1 (Bmi1) expression and decrease the mouse colitis histology index (MCHI) score. In this study, 50 Mus musculus strain BALB/c were divided into five groups: negative control group, colitis group, and colitis groups with vitamin D3 administration of 0.2 mcg, 0.4 mcg, and 0.6 mcg per 25 g body weight for seven days. Dextran sulfate sodium (DSS) 5% was used to induce colitis. Lgr5-Bmi1 expression was measured using immunodoublestain fluorescent labeling method. Our data suggested that administration of vitamin D3 significantly increased expression of Lgr5-Bmi1 in the colonic mucosa. The colitis group treated with the highest dose of vitamin D3 (0.6 mcg/25 gram) showed the lowest MCHI score (3.60±0.64) while the lowest dose of vitamin D3 had the highest MCHI score (12.60±1.47). In conclusion, by stimulating stem cells, vitamin D3 administration stimulates mucosal regeneration, as demonstrated by upregulated expression of Lgr5-Bmi-1.

Dietary regulation of intestinal stem cells in health and disease

Diet is a critical regulator for physiological metabolism and tissue homeostasis, with a close relation to health and disease. As an important organ for digestion and absorption, the intestine comes into direct contact with many dietary components. The rapid renewal of its mucosal epithelium depends on the continuous proliferation and differentiation of intestinal stem cells (ISCs). The function and metabolism of ISCs can be controlled by a variety of dietary patterns including calorie restriction, fasting, high-fat, ketogenic, and high-sugar diets, as well as different nutrients including vitamins, amino acids, dietary fibre, and probiotics. Therefore, dietary interventions targeting ISCs may make it possible to prevent and treat intestinal disorders such as colon cancer, inflammatory bowel disease, and radiation enteritis. This review summarised recent research on the role and mechanism of diet in regulating ISCs, and discussed the potential of dietary modulation for intestinal diseases.

The origin of intestinal cancer in the context of inflammation

According to conventional views, colon cancer originates from stem cells. However, inflammation, a key risk factor for colon cancer, was shown to suppress intestinal stemness. Here, we employed Paneth cells (PCs) as a model to assess the capacity of differentiated lineages to trigger tumorigenesis in the context of inflammation. Upon inflammation, PC-specific Apc mutations led to intestinal tumors reminiscent not only of those arising in inflammatory bowel disease (IBD) patients but also of a larger fraction of sporadic colon cancers. The latter is likely due to the inflammatory consequences of Western-style dietary habits, the major colon cancer risk factor. Computational methods designed to predict the cell-of-origin of cancer confirmed that, in a substantial fraction of sporadic colon cancers the cells-of-origin are secretory lineages and not stem cells.

Key regulators of intestinal stem cells: diet, microbiota, and microbial metabolites

Interactions between diet and the intestinal microbiome play an important role in human health and disease development. It is well known that such interactions, whether direct or indirect, trigger a series of metabolic reactions in the body. Evidence suggests that intestinal stem cells (ISCs), which are phenotypic precursors of various intestinal epithelial cells, play a significant role in the regulation of intestinal barrier function and homeostasis. The advent and evolution of intestinal organoid culture techniques have presented a key opportunity to study the association between the intestinal microenvironment and ISCs. As a result, the effects exerted by dietary factors, intestinal microbiomes, and their metabolites on the metabolic regulation of ISCs and the potential mechanisms underlying such effects are being gradually revealed. This review summarises the effects of different dietary patterns on the behaviour and functioning of ISCs and focuses on the crosstalk between intestinal microbiota, related metabolites, and ISCs, with the aim of fully understanding the relationship between these three factors and providing further insights into the complex mechanisms associated with ISCs in the human body. Gaining an understanding of these mechanisms may lead to the development of novel dietary interventions or drugs conducive to intestinal health.

Dynamic Intestinal Stem Cell Plasticity and Lineage Remodeling by a Nutritional Environment Relevant to Human Risk for Tumorigenesis

New Western-style diet 1 (NWD1), a purified diet establishing mouse exposure to key nutrients recapitulating levels that increase human risk for intestinal cancer, reproducibly causes mouse sporadic intestinal and colonic tumors reflecting human etiology, incidence, frequency, and lag with developmental age. Complex NWD1 stem cell and lineage reprogramming was deconvolved by bulk and single-cell RNA sequencing, single-cell Assay for Transposase-Accessible Chromatin using sequencing, functional genomics, and imaging. NWD1 extensively, rapidly, and reversibly, reprogrammed Lgr5hi stem cells, epigenetically downregulating Ppargc1a expression, altering mitochondrial structure and function. This suppressed Lgr5hi stem cell functions and developmental maturation of Lgr5hi cell progeny as cells progressed through progenitor cell compartments, recapitulated by Ppargc1a genetic inactivation in Lgr5hi cells in vivo. Mobilized Bmi1+, Ascl2hi cells adapted lineages to the nutritional environment and elevated antigen processing and presentation pathways, especially in mature enterocytes, causing chronic, protumorigenic low-level inflammation. There were multiple parallels between NWD1 remodeling of stem cells and lineages with pathogenic mechanisms in human inflammatory bowel disease, also protumorigenic. Moreover, the shift to alternate stem cells reflects that the balance between Lgr5-positive and -negative stem cells in supporting human colon tumors is determined by environmental influences. Stem cell and lineage plasticity in response to nutrients supports historic concepts of homeostasis as a continual adaptation to environment, with the human mucosa likely in constant flux in response to changing nutrient exposures.

IMPLICATIONS

Although oncogenic mutations provide a competitive advantage to intestinal epithelial cells in clonal expansion, the competition is on a playing field dynamically sculpted by the nutritional environment, influencing which cells dominate in mucosal maintenance and tumorigenesis.

Building better barriers: how nutrition and undernutrition impact pediatric intestinal health

Chronic undernutrition is a major cause of death for children under five, leaving survivors at risk for adverse long-term consequences. This review focuses on the role of nutrients in normal intestinal development and function, from the intestinal epithelium, to the closely-associated mucosal immune system and intestinal microbiota. We examine what is known about the impacts of undernutrition on intestinal physiology, with focus again on the same systems. We provide a discussion of existing animal models of undernutrition, and review the evidence demonstrating that correcting undernutrition alone does not fully ameliorate effects on intestinal function, the microbiome, or growth. We review efforts to treat undernutrition that incorporate data indicating that improved recovery is possible with interventions focused not only on delivery of sufficient energy, macronutrients, and micronutrients, but also on efforts to correct the abnormal intestinal microbiome that is a consequence of undernutrition. Understanding of the role of the intestinal microbiome in the undernourished state and correction of the phenotype is both complex and a subject that holds great potential to improve recovery. We conclude with critical unanswered questions in the field, including the need for greater mechanistic research, improved models for the impacts of undernourishment, and new interventions that incorporate recent research gains. This review highlights the importance of understanding the mechanistic effects of undernutrition on the intestinal ecosystem to better treat and improve long-term outcomes for survivors.

Chlorogenic acid improves intestinal morphology by enhancing intestinal stem-cell activity

BACKGROUND

Chlorogenic acid (CGA), as one of the most abundant naturally occurring phenolic acids, has been documented to be beneficial for intestinal health. However, the underlying mechanism is still not fully understood. The adult intestinal stem cell is the critical driver of epithelial homeostasis and regeneration.

RESULTS

This study hypothesized that CGA exerted intestinal health effects by modulating intestinal stem-cell functions. Lgr5-EGFP mice were treated for 14 days, and intestinal organoids derived from these mice were treated for 3 days, using CGA solution. In comparison with the control group, CGA treatment increased intestinal villous height and crypt depth in mice and augmented the area expansion and the number of budding intestinal organoids. Quantitative polymerase chain reaction (qPCR) analysis revealed that CGA treatment significantly increased the expression of genes coding intestinal stem-cell markers in intestinal tissue and organoids, and upregulated the expression of genes coding secretory cell lineages and enterocytes, although not statistically significantly. Fluorescence-activated cell-sorting analysis further confirmed that CGA augmented the number of stem cells. 5-Ethynyl-2'-deoxyuridine (EdU) incorporation and Ki67 immunostaining results also demonstrated that CGA treatment enhanced intestinal stem-cell proliferation.

CONCLUSION

Altogether, our findings indicate that CGA could activate intestinal stem-cell and epithelial regeneration, which could contribute to the improvement of intestinal morphology or organoid growth of mice. This highlights a promising mechanism for CGA as an excellent candidate for the formulation of dietary supplements and functional foods for intestinal protection. © 2023 Society of Chemical Industry.

Alveolar-Capillary Barrier Protection In Vitro: Lung Cell Type-Specific Effects and Molecular Mechanisms Induced by 1α, 25-Dihydroxyvitamin D3

Low serum levels of 1α, 25-dihydroxyvitamin D3 (VD3) are associated with a higher mortality in trauma patients with sepsis or ARDS. However, the molecular mechanisms behind this observation are not yet understood. VD₃ is known to stimulate lung maturity, alveolar type II cell differentiation, or pulmonary surfactant synthesis and guides epithelial defense during infection. In this study, we investigated the impact of VD₃ on the alveolar-capillary barrier in a co-culture model of alveolar epithelial cells and microvascular endothelial cells respectively in the individual cell types. After stimulation with bacterial LPS (lipopolysaccharide), gene expression of inflammatory cytokines, surfactant proteins, transport proteins, antimicrobial peptide, and doublecortin-like kinase 1 (DCLK1) were analyzed by real-time PCR, while corresponding proteins were evaluated by ELISA, immune-fluorescence, or Western blot. The effect of VD3 on the intracellular protein composition in H441 cells was analyzed by quantitative liquid chromatography-mass spectrometry-based proteomics. VD₃ effectively protected the alveolar-capillary barrier against LPS treatment, as indicated by TEER measurement and morphological assessment. VD₃ did not inhibit the IL-6 secretion by H441 and OEC but restricted the diffusion of IL-6 to the epithelial compartment. Further, VD₃ could significantly suppress the surfactant protein A expression induced in the co-culture system by LPS treatment. VD₃ induced high levels of the antimicrobial peptide LL-37, which counteracted effects by LPS and strengthened the barrier. Quantitative proteomics identified VD3-dependent protein abundance changes ranging from constitutional extracellular matrix components and surfactant-associated proteins to immune-regulatory molecules. DCLK1, as a newly described target molecule for VD₃, was prominently stimulated by VD₃ (10 nM) and seems to influence the alveolar-epithelial cell barrier and regeneration.

Perturbation of intestinal stem cell homeostasis and radiation enteritis recovery via dietary titanium dioxide nanoparticles

Small intestinal health and enteritis incidence are tightly coupled to the homeostasis of intestinal stem cells (ISCs), which are sensitive to dietary alterations. However, little is known about the impact of food additives on ISC pool. Here, we demonstrate that chronic exposure to low-dose TiO₂ NPs, a commonly used food additive, significantly hampers primary human and mouse ISC-derived organoid formation and growth by specifically attenuating Wnt signal transduction. Mechanistically, TiO₂ NPs alter the endocytic trafficking of the Wnt receptor LRP6 and prevent the nuclear entry of β-catenin. Notably, dietary TiO₂ NPs elicit modest chronic stress in healthy intestines and considerably impede the recovery of radiation enteritis by perturbing the homeostasis of ISCs in vivo. Our results identify a health concern of TiO₂ NP exposure on ISC homeostasis and radiation enteritis recovery. These findings suggest extra precaution during the treatment of radiation enteritis and provide new insights into food additive-ISC interaction.

Paneth cells as the origin of intestinal cancer in the context of inflammation

Paneth cells (PCs), responsible for the secretion of antimicrobial peptides in the small intestine and for niche support to Lgr5+ crypt-base columnar stem cells (CBCs), have been shown to respond to inflammation by dedifferentiating into stem-like cells in order to sustain a regenerative response1,2. Therefore, PCs may represent the cells-of-origin of intestinal cancer in the context of inflammation. To test this hypothesis, we targeted Apc, Kras, and Tp53 mutations in Paneth cells by Cre-Lox technology and modelled inflammation by dextran sodium sulfate (DSS) administration. PC-specific loss of Apc resulted in multiple small intestinal tumors, whereas Kras or Tp53 mutations did not. Compound Apc and Kras mutations in PCs resulted in a striking increase in tumor multiplicity even in the absence of the inflammatory insult. By combining scRNAseq with lineage tracing to capture the conversion of PCs into bona fide tumor cells, we show that they progress through a "revival stem cell" (RSC) state characterized by high Clusterin (Clu) expression and Yap1 signaling, reminiscent of what has been previously observed upon irradiation of the mouse digestive tract3. Accordingly, comparison of PC- and Lgr5-derived murine intestinal tumors revealed differences related to Wnt signaling and inflammatory pathways which match the dichotomy of CBCs and injury-induced RSCs4 between human sporadic colon cancers and those arising in the context of inflammatory bowel diseases. Last, we show that western-style dietary habits, known to trigger a low-grade inflammation throughout the intestinal tract, underlie the analogous dedifferentiation of Paneth cells and their acquisition of stem-like features. Taken together, our results show that intestinal cancer arises in the context of inflammation through the dedifferentiation of committed secretory lineages such as Paneth cells and the activation of the revival stem cell state. As such, a true quiescent stem cell identity may be hidden in fully committed and postmitotic lineages which, upon inflammation, support the regenerative response by re-entering the cell cycle and dedifferentiating into RSCs. The chronic nature of the tissue insult in inflammatory bowel diseases and even in the context of western-style dietary habits is likely to result in the expansion of cell targets for tumor initiation and progression.

Fluorescence Intensity and Fluorescence Lifetime Imaging Microscopies (FLIM) of Cell Differentiation in the Small Intestinal Organoids Using Cholera Toxin

Live cell microscopies of in vitro, ex vivo, and in vivo experimental intestinal models enable visualizing cell proliferation, differentiation, and functional cellular status in response to intrinsic and extrinsic (e.g., in the presence of microbiota) factors. While the use of transgenic animal models expressing biosensor fluorescent proteins can be laborious and not compatible with clinical samples and patient-derived organoids, the use of fluorescent dye tracers is an attractive alternative. In this protocol, we describe how the differentiation-dependent intestinal cell membrane composition can be labeled using fluorescent cholera toxin subunit B (CTX) derivatives. By using the culture of mouse adult stem cell-derived small intestinal organoids, we show that CTX can bind specific plasma membrane domains in differentiation-dependent manner. Green (Alexa Fluor 488) and red (Alexa Fluor 555) fluorescent CTX derivatives also display additional contrast in a fluorescence lifetime domain, when probed by the fluorescence lifetime imaging microscopy (FLIM), and can be used together with other fluorescent dyes and cell tracers. Importantly, CTX staining remains confined to specific regions in the organoids after fixation, which enables using it in both live cell and fixed tissue immunofluorescence microscopies.

Vitamin D3 and Lactobacillus rhamnosus GG/p40 Synergize to Protect Mice From Colitis by Promoting Vitamin D Receptor Expression and Epithelial Proliferation

BACKGROUND

While vitamin D (VitD) levels are negatively correlated with inflammatory bowel disease (IBD) activity, VitD supplementation does not reduce IBD severity. The probiotic Lactobacillus rhamnosus GG (LGG), which secretes p40, can upregulate colonic VitD receptor (VDR) expression. We therefore evaluated synergy between VitD3 and LGG/p40 in the treatment of mouse colitis.

METHODS

A dextran sulfate sodium (DSS) colitis model was established in Vdr+/+ and Vdr-/- mice, and mice were treated with VitD3, LGG, or p40 alone or in combination for 7 to 14 days. Colitis severity was assessed by weight loss, disease activity index (DAI), colon length, histology, and inflammatory cytokine expression together with VDR expression, proliferation, and apoptosis. In vitro, VDR expression and cell viability were assessed in HCT116 cells after stimulation with p40.

RESULTS

Total and nuclear VDR protein expression were lower in DSS-treated Vdr+/+ mice compared with control mice (P < .05). Compared with the DSS group, VitD3 + LGG alleviated colitis as assessed by significantly improved DAI and histological scores, increased colon length, decreased colonic Tnf, and increased Il10 expression together with increased colonic VDR gene and protein expression and increased Ki-67 proliferation index (P < .05). In Vdr-/- mice, VitD3 + LGG had no effect on DSS colitis. In Vdr+/+ mice, VitD3 + p40 also reduced colitis severity according to clinicopathological and immunological metrics and increased VDR expression and epithelial proliferation (P < .05). In HCT116 cells, p40 stimulation increased VDR protein expression and viability (P < .05).

CONCLUSIONS

VitD3 and LGG/p40 synergistically improve the severity of colitis by increasing colonic VDR expression and promoting colonic epithelial proliferation.

Downregulation of the vitamin D receptor expression during acute gastrointestinal graft versus host disease is associated with poor outcome after allogeneic stem cell transplantation

The vitamin D receptor (VDR) is critical in regulating intestinal homeostasis and emerging evidence demonstrates that VDR deficiency is a critical factor in inflammatory bowel disease pathology. However, no clinical data exist regarding the intestinal expression of VDR in patients after allogeneic haematopoietic stem cell transplantation (HSCT). Analyzing intestinal biopsies from 90 patients undergoing HSCT with mortality follow-up, we demonstrated that patients with severe acute gastrointestinal graft versus host disease (GI-GvHD) showed significant downregulation of VDR gene expression compared to mild or no acute GI-GvHD patients (p = 0.007). Reduced VDR expression was already detectable at acute GI-GvHD onset compared to GvHD-free patients (p = 0.01). These results were confirmed by immunohistochemistry (IHC) where patients with severe acute GI-GvHD showed fewer VDR+ cells (p = 0.03) and a reduced VDR staining score (p = 0.02) as compared to mild or no acute GI-GvHD patients. Accordingly, low VDR gene expression was associated with a higher cumulative incidence of treatment-related mortality (TRM) (p = 1.6x10-6) but not with relapse-related mortality (RRM). A multivariate Cox regression analysis identified low VDR as an independent risk factor for TRM (p = 0.001, hazard ratio 4.14, 95% CI 1.78-9.63). Furthermore, VDR gene expression significantly correlated with anti-microbial peptides (AMPs) gene expression (DEFA5: r = 0.637, p = 7x10-5, DEFA6: r 0 0.546, p = 0.001). In conclusion, our findings suggest an essential role of the VDR in the pathogenesis of gut GvHD and the prognosis of patients undergoing HSCT.

Genomic analysis of 1,25-dihydroxyvitamin D3 action in mouse intestine reveals compartment and segment-specific gene regulatory effects

1,25-dihydroxyvitamin D (VD) regulates intestinal calcium absorption in the small intestine (SI) and also reduces risk of colonic inflammation and cancer. However, the intestine compartment-specific target genes of VD signaling are unknown. Here, we examined VD action across three functional compartments of the intestine using RNA-seq to measure VD-induced changes in gene expression and Chromatin Immunoprecipitation with next generation sequencing to measure vitamin D receptor (VDR) genomic binding. We found that VD regulated the expression of 55 shared transcripts in the SI crypt, SI villi, and in the colon, including Cyp24a1, S100g, Trpv6, and Slc30a10. Other VD-regulated transcripts were unique to the SI crypt (162 up, 210 down), villi (199 up, 63 down), or colon (102 up, 28 down), but this did not correlate with mRNA levels of the VDR. Furthermore, bioinformatic analysis identified unique VD-regulated biological functions in each compartment. VDR-binding sites were found in 70% of upregulated genes from the colon and SI villi but were less common in upregulated genes from the SI crypt and among downregulated genes, suggesting some transcript-level VD effects are likely indirect. Consistent with this, we show that VD regulated the expression of other transcription factors and their downstream targets. Finally, we demonstrate that compartment-specific VD-mediated gene expression was associated with compartment-specific VDR-binding sites (<30% of targets) and enrichment of intestinal transcription factor-binding motifs within VDR-binding peaks. Taken together, our data reveal unique spatial patterns of VD action in the intestine and suggest novel mechanisms that could account for compartment-specific functions of this hormone.

Metabolic regulation of somatic stem cells in vivo

Metabolism has been studied mainly in cultured cells or at the level of whole tissues or whole organisms in vivo. Consequently, our understanding of metabolic heterogeneity among cells within tissues is limited, particularly when it comes to rare cells with biologically distinct properties, such as stem cells. Stem cell function, tissue regeneration and cancer suppression are all metabolically regulated, although it is not yet clear whether there are metabolic mechanisms unique to stem cells that regulate their activity and function. Recent work has, however, provided evidence that stem cells do have a metabolic signature that is distinct from that of restricted progenitors and that metabolic changes influence tissue homeostasis and regeneration. Stem cell maintenance throughout life in many tissues depends upon minimizing anabolic pathway activation and cell division. Consequently, stem cell activation by tissue injury is associated with changes in mitochondrial function, lysosome activity and lipid metabolism, potentially at the cost of eroding self-renewal potential. Stem cell metabolism is also regulated by the environment: stem cells metabolically interact with other cells in their niches and are able to sense and adapt to dietary changes. The accelerating understanding of stem cell metabolism is revealing new aspects of tissue homeostasis with the potential to promote tissue regeneration and cancer suppression.

Vitamin D and Gut Health

Vitamin D is a conditionally required nutrient that can either be obtained from skin synthesis following UVB exposure from the diet. Once in the body, it is metabolized to produce the endocrine hormone, 1,25 dihydroxyvitamin D (1,25(OH)2D), that regulates gene expression in target tissues by interacting with a ligand-activated transcription factor, the vitamin D receptor (VDR). The first, and most responsive, vitamin D target tissue is the intestine. The classical intestinal role for vitamin D is the control of calcium metabolism through the regulation of intestinal calcium absorption. However, studies clearly show that other functions of the intestine are regulated by the molecular actions of 1,25(OH)2 D that are mediated through the VDR. This includes enhancing gut barrier function, regulation of intestinal stem cells, suppression of colon carcinogenesis, and inhibiting intestinal inflammation. While research demonstrates that there are both classical, calcium-regulating and non-calcium regulating roles for vitamin D in the intestine, the challenge facing biomedical researchers is how to translate these findings in ways that optimize human intestinal health.

Therapeutic effects of vitamin D and IL-22 on methotrexate-induced mucositis in mice

Mucositis is a common side effect of cancer therapies and transplant conditioning regimens. Management of mucositis involves multiple approaches from oral hygiene, anti-inflammatory, anti-apoptotic, cytoprotective, and antioxidant agents, to cryo-therapy, physical therapy, and growth factors. There is room for novel, affordable treatment options, or improvement of currently available therapies. Vitamin D has been shown to regulate mucosa-resident cell populations such as Th17 or innate lymphoid cells and critical mucosal cytokine IL-22; however, their therapeutic potential has not been put to test in preclinical mouse models. In this study, we aimed to test the therapeutic potential of vitamin D injections and IL-22 overexpression in a murine model of chemotherapy-induced mucositis. Balb/c mice were given daily intraperitoneal injections of vitamin D. Mucositis was induced by methotrexate. Another group received IL-22 plasmid via hydrodynamic gene delivery. Weight loss and intestinal histopathology, intestinal levels of cytokines IL-22, IL-17A, GM-CSF, IL-23, IFN-γ, TNF-α, and IL-10, and number of intestinal lamina propria B cell, neutrophil, and total innate lymphoid cells were quantified. Daily vitamin D injections ameliorated intestinal inflammation and elevated intestinal IL-22 levels compared with control groups. Temporal overexpression of IL-22 by hydrodynamic gene delivery slightly increased intestinal IL-22 but failed to confer significant protection from mucositis. To our knowledge, this is the first experimental demonstration in an animal model of mucositis of therapeutic use of vitamin D and IL-22 supplementation and our results with vitamin D suggest it may have merit in further trials in human mucositis patients.

Vitamin D: A Critical Regulator of Intestinal Physiology

Calcium is required for the functioning of numerous biological processes and is essential for skeletal health. The major source of new calcium is from the diet. The central role of vitamin D in the maintenance of calcium homeostasis is to increase the absorption of ingested calcium from the intestine. The critical importance of vitamin D in this process is noted in the causal link between vitamin D deficiency and rickets, as well as in studies using genetically modified mice including mice deficient in the vitamin D receptor (Vdr null mice) or in the cytochrome P‐450 enzyme, 25‐hydroxyvitamin D₃‐1α‐ hydroxylase (CYP27B1) that converts 25‐hydroxyvitamin D₃ to the hormonally active form of vitamin D, 1,25‐dihydroxyvitamin D₃ [1,25(OH)₂D₃] (Cyp27b1 null mice). When these mice are fed diets with high calcium and lactose, rickets is prevented. The studies using mouse models provide supporting evidence indicating that the major physiological function of 1,25(OH)₂D₃/VDR is intestinal calcium absorption. This review summarizes what is known about mechanisms involved in vitamin D‐regulated intestinal calcium absorption. Recent studies suggest that vitamin D does not affect a single entity, but that a complex network of calcium‐regulating components is involved in the process of 1,25(OH)₂D₃‐mediated active intestinal calcium absorption. In addition, numerous 1,25(OH)₂D₃ actions in the intestine have been described independent of calcium absorption. Although the translatability to humans requires further definition, an overview is presented that provides compelling evidence from the laboratory of 1,25(OH)₂D₃ intestinal effects, which include the regulation of adhesion molecules to enhance barrier function, the regulation of intestinal stem cell function, cellular homeostasis of other divalent cations, the regulation of drug metabolizing enzymes, and anti‐inflammatory effects. © 2021 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Short-Chain Fatty Acids Produced by Ruminococcaceae Mediate α-Linolenic Acid Promote Intestinal Stem Cells Proliferation

SCOPE

The proliferation and differentiation of intestinal stem cells (ISCs) are the basis of intestinal renewal and regeneration, and gut microbiota plays an important role in it. Dietary nutrition has the effect of regulating the activity of ISCs; however, the regulation effect of α-linolenic acid (ALA) has seldom been reported.

METHODS AND RESULTS

After intervening mice with different doses of ALA for 30 days, it is found that ALA (0.5 g kg^-1 ) promotes small intestinal and villus growth by activating the Wnt/β-catenin signaling pathway to stimulate the proliferation of ISCs. Furthermore, ALA administration increases the abundance of the Ruminococcaceae and Prevotellaceae, and promotes the production of short-chain fatty acids (SCFAs). Subsequent fecal transplantation and antibiotic experiments demonstrate that ALA on the proliferation of ISCs are gut microbiota dependent, among them, the functional microorganism may be derived from Ruminococcaceae. Administration of isobutyrate shows a similar effect to ALA in terms of promoting ISCs proliferation. Furthermore, ALA mitigates 5-fluorouracil-induced intestinal mucosal damage by promoting ISCs proliferation.

CONCLUSION

These results indicate that SCFAs produced by Ruminococcaceae mediate ALA promote ISCs proliferation by activating the Wnt/β-catenin signaling pathway, and suggest the possibility of ALA as a prebiotic agent for the prevention and treatment of intestinal mucositis.

The Potential of Vitamin D3 to Repaired Mucosal Injury in Dextran Sulfate Sodium Induced Acute Colitis in Mice

BACKGROUND: Inflammatory Bowel Disease (IBD) has become an emerging disease worldwide. The treatment of IBD involves two basic principles: Inflammation control and mucosal repair. AIM: This study evaluates the potential effect of Vitamin D3 in mucosal repair through colon stem cell activation and proliferation. METHODS: Dextran sulfate sodium (DSS; 5%) was used to induce colitis in mice. Vitamin D3 at various dosages was then administered as a treatment. The mice were divided into five groups: Control (C-); DSS only (C+); and DSS (5%) plus Vitamin D3 at 0.2 μg (VD1), 0.4 μg (VD2), or 0.6 μg (VD3) per 25 g body weight as the treatment groups. Immunofluorescence analyses of Lgr5+ expression indicated stem cell activation, and Ki67 expression indicated stem cell proliferation. The disease activity index (DAI), colon length, and histopathological index scores were determined after treatment to assess the inflammation and severity of colitis. RESULTS: Immunofluorescence analyses showed a gradually increasing expression of Lgr5+ also Ki67 in proportion with high doses group of Vitamin D3 (p < 0.05). The colon length, DAI scores, and histopathological index scores improved in all groups after Vitamin D3 treatment (p = 0.05; p = 0.026; and p = 0.029, respectively). CONCLUSION: Vitamin D3 has a potential beneficial effect on amplifying intestinal stem cells regulated by Wnt/B-catenin signaling. It is also reduced the inflammatory process proved by the evaluation severity of colitis. It might play an essential role in mucosal repair in IBD.

Inflammation- and Gut-Homing Macrophages, Engineered to De Novo Overexpress Active Vitamin D, Promoted the Regenerative Function of Intestinal Stem Cells

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gut. Available drugs aim to suppress gut inflammation. These drugs have significantly delayed disease progression and improved patients’ quality of life. However, the disease continues to progress, underscoring the need to develop novel therapies. Aside from chronic gut inflammation, IBD patients also experience a leaky gut problem due to damage to the intestinal epithelial layer. In this regard, epithelial regeneration and repair are mediated by intestinal stem cells. However, no therapies are available to directly enhance the intestinal stem cells’ regenerative and repair function. Recently, it was shown that active vitamin D, i.e., 1,25-dihydroxyvitamin D or 1,25(OH)₂D, was necessary to maintain Lgr5⁺ intestinal stem cells, actively cycling under physiological conditions. In this study, we used two strategies to investigate the role of 1,25(OH)₂D in intestinal stem cells’ regenerative function. First, to avoid the side effects of systemic high 1,25(OH)₂D conditions, we used our recently developed novel strategy to deliver locally high 1,25(OH)₂D concentrations specifically to inflamed intestines. Second, because of the Lgr5⁺ intestinal stem cells’ active cycling status, we used a pulse-and-chase strategy via 5-bromo-2′-deoxyuridine (BrdU) labeling to trace the Lgr5⁺ stem cells through the whole epithelial regeneration process. Our data showed that locally high 1,25(OH)₂D concentrations enhanced intestinal stem cell migration. Additionally, the migrated cells differentiated into mature epithelial cells. Our data, therefore, suggest that local delivery of high 1,25(OH)₂D concentrations is a promising strategy to augment intestinal epithelial repair in IBD patients.

Vitamin D Receptor Protects against Radiation-Induced Intestinal Injury in Mice via Inhibition of Intestinal Crypt Stem/Progenitor Cell Apoptosis

It is urgent to seek new potential targets for the prevention or relief of gastrointestinal syndrome in clinical radiation therapy for cancers. Vitamin D, mediated through the vitamin D receptor (VDR), has been identified as a protective nutrient against ionizing radiation (IR)-induced damage. This study investigated whether VDR could inhibit IR-induced intestinal injury and explored underlying mechanism. We first found that vitamin D induced VDR expression and inhibited IR-induced DNA damage and apoptosis in vitro. VDR was highly expressed in intestinal crypts and was critical for crypt stem/progenitor cell proliferation under physiological conditions. Next, VDR-deficient mice exposed to IR significantly increased DNA damage and crypt stem/progenitor cell apoptosis, leading to impaired intestinal regeneration as well as shorter survival time. Furthermore, VDR deficiency activated the Pmaip1-mediated apoptotic pathway of intestinal crypt stem/progenitor cells in IR-treated mice, whereas inhibition of Pmaip1 expression by siRNA transfection protected against IR-induced cell apoptosis. Therefore, VDR protects against IR-induced intestinal injury through inhibition of crypt stem/progenitor cell apoptosis via the Pmaip1-mediated pathway. Our results reveal the importance of VDR level in clinical radiation therapy, and targeting VDR may be a useful strategy for treatment of gastrointestinal syndrome.

1,25-Dihydroxyvitamin D3 and dietary vitamin D reduce inflammation in mice lacking intestinal epithelial cell Rab11a

A number of studies have examined the effects of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂ D₃ ) on intestinal inflammation driven by immune cells, while little information is currently available about its impact on inflammation caused by intestinal epithelial cell (IEC) defects. Mice lacking IEC-specific Rab11a a recycling endosome small GTPase resulted in increased epithelial cell production of inflammatory cytokines, notably IL-6 and early onset of enteritis. To determine whether vitamin D supplementation may benefit hosts with epithelial cell-originated mucosal inflammation, we evaluated in vivo effects of injected 1,25(OH)₂ D₃ or dietary supplement of a high dose of vitamin D on the gut phenotypes of IEC-specific Rab11a knockout mice (Rab11a^ΔIEC ). 1,25(OH)₂ D₃ administered at 25 ng, two doses per mouse, by intraperitoneal injection, reduced inflammatory cytokine production in knockout mice compared to vehicle-injected mice. Remarkably, feeding mice with dietary vitamin D supplementation at 20,000 IU/kg spanning fetal and postnatal developmental stages led to improved bodyweights, reduced immune cell infiltration, and decreased inflammatory cytokines. We found that these vitamin D effects were accompanied by decreased NF-κB (p65) in the knockout intestinal epithelia, reduced tissue-resident macrophages, and partial restoration of epithelial morphology. Our study suggests that dietary vitamin D supplementation may prevent and limit intestinal inflammation in hosts with high susceptibility to chronic inflammation.

The Interplay between Nutrition, Innate Immunity, and the Commensal Microbiota in Adaptive Intestinal Morphogenesis

The gastrointestinal tract is a functionally and anatomically segmented organ that is colonized by microbial communities from birth. While the genetics of mouse gut development is increasingly understood, how nutritional factors and the commensal gut microbiota act in concert to shape tissue organization and morphology of this rapidly renewing organ remains enigmatic. Here, we provide an overview of embryonic mouse gut development, with a focus on the intestinal vasculature and the enteric nervous system. We review how nutrition and the gut microbiota affect the adaptation of cellular and morphologic properties of the intestine, and how these processes are interconnected with innate immunity. Furthermore, we discuss how nutritional and microbial factors impact the renewal and differentiation of the epithelial lineage, influence the adaptation of capillary networks organized in villus structures, and shape the enteric nervous system and the intestinal smooth muscle layers. Intriguingly, the anatomy of the gut shows remarkable flexibility to nutritional and microbial challenges in the adult organism.

High-fat diet-activated fatty acid oxidation mediates intestinal stemness and tumorigenicity

Obesity is an established risk factor for cancer in many tissues. In the mammalian intestine, a pro-obesity high-fat diet (HFD) promotes regeneration and tumorigenesis by enhancing intestinal stem cell (ISC) numbers, proliferation, and function. Although PPAR (peroxisome proliferator-activated receptor) nuclear receptor activity has been proposed to facilitate these effects, their exact role is unclear. Here we find that, in loss-of-function in vivo models, PPARα and PPARδ contribute to the HFD response in ISCs. Mechanistically, both PPARs do so by robustly inducing a downstream fatty acid oxidation (FAO) metabolic program. Pharmacologic and genetic disruption of CPT1A (the rate-controlling enzyme of mitochondrial FAO) blunts the HFD phenotype in ISCs. Furthermore, inhibition of CPT1A dampens the pro-tumorigenic consequences of a HFD on early tumor incidence and progression. These findings demonstrate that inhibition of a HFD-activated FAO program creates a therapeutic opportunity to counter the effects of a HFD on ISCs and intestinal tumorigenesis.

Modulation of intestinal stem cell homeostasis by nutrients: a novel therapeutic option for intestinal diseases

Intestinal stem cells, which are capable of both self-renewal and differentiation to mature cell types, are responsible for maintaining intestinal epithelial homeostasis. Recent evidence indicates that these processes are mediated, in part, through nutritional status in response to diet. Diverse dietary patterns including caloric restriction, fasting, high-fat diets, ketogenic diets and high-carbohydrate diets as well as other nutrients control intestinal stem cell self-renewal and differentiation through nutrient-sensing pathways such as mammalian target of rapamycin and AMP-activated kinase. Herein, we summarise the current understanding of how intestinal stem cells contribute to intestinal epithelial homeostasis and diseases. We also discuss the effects of diet and nutrient-sensing pathways on intestinal stem cell self-renewal and differentiation, as well as their potential application in the prevention and treatment of intestinal diseases.

Vitamin D3 suppresses intestinal epithelial stemness via ER stress induction in intestinal organoids

BACKGROUND

Vitamin D₃ is important for normal function of the intestinal epithelial cells (IECs). In this study, we aimed to investigate the effects of vitamin D₃ on the differentiation, stemness, and viability of healthy IECs in intestinal organoids.

METHODS

Intestinal organoids derived from mouse small intestine were treated with vitamin D₃, and the effects on intestinal stemness and differentiation were evaluated using real-time PCR and immunofluorescence staining of the distinct lineage markers. Cell viability was analyzed using viability and apoptosis assays.

RESULTS

Vitamin D₃ enhanced IEC differentiation into the distinct lineages of specialized IECs, including Paneth, goblet, and enteroendocrine cells and absorptive enterocytes. Decreased expression levels of leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) and the presence of several LGR5-green fluorescent protein (GFP)-positive cells were observed in vitamin D₃-treated organoids derived from LGR5-GFP mice. The formation of the crypt-villus structure was also inhibited by vitamin D₃, suggesting that vitamin D₃ suppresses intestinal cell stemness. Furthermore, the expression levels of unfolded protein response genes, C/EBP homologous protein (CHOP), and activating transcription factor 6 (ATF6) were upregulated in vitamin D₃-treated organoids. Moreover, vitamin D₃ promoted apoptotic cell death in intestinal cells, which may be associated with the decrease in intestinal stemness. LGR5 gene expression, ISC number, and apoptotic cell death were partially recovered in the presence of the ER stress inhibitor tauroursodeoxycholic acid (TUDCA), suggesting that intestinal stemness suppression and intestinal apoptosis occurred via ER stress activation.

CONCLUSIONS

Our study provides important insights into the effects of vitamin D₃ on the induction of IEC differentiation and apoptotic cell death, and inhibition of intestinal stemness accompanied by ER stress augmentation.

Subversion of Niche-Signalling Pathways in Colorectal Cancer: What Makes and Breaks the Intestinal Stem Cell

The intestinal epithelium fulfils pleiotropic functions in nutrient uptake, waste elimination, and immune surveillance while also forming a barrier against luminal toxins and gut-resident microbiota. Incessantly barraged by extraneous stresses, the intestine must continuously replenish its epithelial lining and regenerate the full gamut of specialized cell types that underpin its functions. Homeostatic remodelling is orchestrated by the intestinal stem cell (ISC) niche: a convergence of epithelial- and stromal-derived cues, which maintains ISCs in a multipotent state. Following demise of homeostatic ISCs post injury, plasticity is pervasive among multiple populations of reserve stem-like cells, lineage-committed progenitors, and/or fully differentiated cell types, all of which can contribute to regeneration and repair. Failure to restore the epithelial barrier risks seepage of toxic luminal contents, resulting in inflammation and likely predisposing to tumour formation. Here, we explore how homeostatic niche-signalling pathways are subverted in tumorigenesis, enabling ISCs to gain autonomy from niche restraints ("ISC emancipation") and transform into cancer stem cells capable of driving tumour initiation, progression, and therapy resistance. We further consider the implications of the pervasive plasticity of the intestinal epithelium for the trajectory of colorectal cancer, the emergence of distinct molecular subtypes, the propensity to metastasize, and the development of effective therapeutic strategies.

Vitamin D sufficiency enhances differentiation of patient-derived prostate epithelial organoids

Vitamin D is an essential steroid hormone that regulates systemic calcium homeostasis and cell fate decisions. The prostate gland is hormonally regulated, requiring steroids for proliferation and differentiation of secretory luminal cells. Vitamin D deficiency is associated with an increased risk of lethal prostate cancer, which exhibits a dedifferentiated pathology, linking vitamin D sufficiency to epithelial differentiation. To determine vitamin D regulation of prostatic epithelial differentiation, patient-derived benign prostate epithelial organoids were grown in vitamin D-deficient or -sufficient conditions. Organoids were assessed by phenotype and single-cell RNA sequencing. Mechanistic validation demonstrated that vitamin D sufficiency promoted organoid growth and accelerated differentiation by inhibiting canonical Wnt activity and suppressing Wnt family member DKK3. Wnt and DKK3 were also reduced by vitamin D in prostate tissue explants by spatial transcriptomics. Wnt dysregulation is a known contributor to aggressive prostate cancer, thus findings further link vitamin D deficiency to lethal disease.

Nutritional Control of Intestinal Stem Cells in Homeostasis and Tumorigenesis

Food and nutrition have a profound impact on organismal health and diseases, and tissue-specific adult stem cells play a crucial role in coordinating tissue maintenance by responding to dietary cues. Emerging evidence indicates that adult intestinal stem cells (ISCs) actively adjust their fate decisions in response to diets and nutritional states to drive intestinal adaptation. Here, we review the signaling mechanisms mediating the dietary responses imposed by caloric intake and nutritional composition (i.e., macronutrients and micronutrients), fasting-feeding patterns, diet-induced growth factors, and microbiota on ISCs and their relevance to the beginnings of intestinal tumors.

Analysis of 1,25-Dihydroxyvitamin D3 Genomic Action Reveals Calcium-Regulating and Calcium-Independent Effects in Mouse Intestine and Human Enteroids

Although vitamin D is critical for the function of the intestine, most studies have focused on the duodenum. We show that transgenic expression of the vitamin D receptor (VDR) only in the distal intestine of VDR null mice (KO/TG mice) results in the normalization of serum calcium and rescue of rickets. Although it had been suggested that calcium transport in the distal intestine involves a paracellular process, we found that the 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-activated genes in the proximal intestine associated with active calcium transport (Trpv6, S100g, and Atp2b1) are also induced by 1,25(OH)2D3 in the distal intestine of KO/TG mice. In addition, Slc30a10, encoding a manganese efflux transporter, was one of the genes most induced by 1,25(OH)2D3 in both proximal and distal intestine. Both villus and crypt were found to express Vdr and VDR target genes. RNA sequence (RNA-seq) analysis of human enteroids indicated that the effects of 1,25(OH)2D3 observed in mice are conserved in humans. Using Slc30a10-/- mice, a loss of cortical bone and a marked decrease in S100g and Trpv6 in the intestine was observed. Our findings suggest an interrelationship between vitamin D and intestinal Mn efflux and indicate the importance of distal intestinal segments to vitamin D action.

Exogenous L-arginine increases intestinal stem cell function through CD90+ stromal cells producing mTORC1-induced Wnt2b

The renewal and repair of intestinal epithelium depend on the self-renewal of intestinal stem cells (ISCs) under physiological and pathological conditions. Although previous work has established that exogenous nutrients regulate adult stem cell activity, little is known about the regulatory effect of L-arginine on ISCs. In this study we utilize mice and small intestinal (SI) organoid models to clarify the role of L-arginine on epithelial differentiation of ISCs. We show that L-arginine increases expansion of ISCs in mice. Furthermore, CD90⁺ intestinal stromal cells augment stem-cell function in response to L-arginine in co-culture experiments. Mechanistically, we find that L-arginine stimulates Wnt2b secretion by CD90⁺ stromal cells through the mammalian target of rapamycin complex 1 (mTORC1) and that blocking Wnt2b production prevents L-arginine-induced ISC expansion. Finally, we show that L-arginine treatment protects the gut in response to injury. Our findings highlight an important role for CD90+ stromal cells in L-arginine-stimulated ISC expansion.

Vitamin D Effects on Cell Differentiation and Stemness in Cancer

Vitamin D₃ is the precursor of 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), a pleiotropic hormone that is a major regulator of the human genome. 1,25(OH)₂D₃ modulates the phenotype and physiology of many cell types by controlling the expression of hundreds of genes in a tissue- and cell-specific fashion. Vitamin D deficiency is common among cancer patients and numerous studies have reported that 1,25(OH)₂D₃ promotes the differentiation of a wide panel of cultured carcinoma cells, frequently associated with a reduction in cell proliferation and survival. A major mechanism of this action is inhibition of the epithelial–mesenchymal transition, which in turn is largely based on antagonism of the Wnt/β-catenin, TGF-β and EGF signaling pathways. In addition, 1,25(OH)₂D₃ controls the gene expression profile and phenotype of cancer-associated fibroblasts (CAFs), which are important players in the tumorigenic process. Moreover, recent data suggest a regulatory role of 1,25(OH)₂D₃ in the biology of normal and cancer stem cells (CSCs). Here, we revise the current knowledge of the molecular and genetic basis of the regulation by 1,25(OH)₂D₃ of the differentiation and stemness of human carcinoma cells, CAFs and CSCs. These effects support a homeostatic non-cytotoxic anticancer action of 1,25(OH)₂D₃ based on reprogramming of the phenotype of several cell types.

Plasticity of Paneth cells and their ability to regulate intestinal stem cells

Paneth cells (PCs) are located at the bottom of small intestinal crypts and play an important role in maintaining the stability of the intestinal tract. Previous studies reported on how PCs shape the intestinal microbiota or the response to the immune system. Recent studies have determined that PCs play an important role in the regulation of the homeostasis of intestinal epithelial cells. PCs can regulate the function and homeostasis of intestinal stem cells through several mechanisms. On the one hand, under pathological conditions, PCs can be dedifferentiated into stem cells to promote the repair of intestinal tissues. On the other hand, PCs can regulate stem cell proliferation by secreting a variety of hormones (such as wnt3a) or metabolic intermediates. In addition, we summarise key signalling pathways that affect PC differentiation and mutual effect with intestinal stem cells. In this review, we introduce the diverse functions of PCs in the intestine.

Plasticity of Paneth cells and their ability to regulate intestinal stem cells

Paneth cells (PCs) are located at the bottom of small intestinal crypts and play an important role in maintaining the stability of the intestinal tract. Previous studies reported on how PCs shape the intestinal microbiota or the response to the immune system. Recent studies have determined that PCs play an important role in the regulation of the homeostasis of intestinal epithelial cells. PCs can regulate the function and homeostasis of intestinal stem cells through several mechanisms. On the one hand, under pathological conditions, PCs can be dedifferentiated into stem cells to promote the repair of intestinal tissues. On the other hand, PCs can regulate stem cell proliferation by secreting a variety of hormones (such as wnt3a) or metabolic intermediates. In addition, we summarise key signalling pathways that affect PC differentiation and mutual effect with intestinal stem cells. In this review, we introduce the diverse functions of PCs in the intestine.

Regulation of the Paneth cell niche by exogenous L-arginine couples the intestinal stem cell function

Although previous studies show that exogenous nutrients regulate the stem cell function, little is known about the effects of L-arginine on intestinal stem cells (ISCs). In this study, we utilize mice, small intestinal (SI) organoids, and ISC-Paneth cell co-cultured models to clarify the role of L-arginine in ISC function. We find that exogenous L-arginine is essential for ISCs proliferation and intestinal epithelial renewal. Our data show that Paneth cells, a critical component of the ISCs niche, augment the ISCs function in response to L-arginine. Moreover, enhanced the expression of Wnt3a in Paneth cells, which is a ligand of the Wnt/β-catenin signaling pathway, mediates the effects of L-arginine on ISCs function. Pre-treatment with L-arginine enhances the ISCs pool and protects the gut in response to injury provoked by murine tumor necrosis factor α (TNF-α) and 5-Fluorouracil (5-FU). Our findings establish that the regulation of Wnt3a in the Paneth cell niche by exogenous L-arginine couples ISCs function and favours a model in which the ISCs niche couples the nutrient levels to ISCs function.

The nutritional environment determines which and how intestinal stem cells contribute to homeostasis and tumorigenesis

Sporadic colon cancer accounts for approximately 80% of colorectal cancer (CRC) with high incidence in Western societies strongly linked to long-term dietary patterns. A unique mouse model for sporadic CRC results from feeding a purified rodent Western-style diet (NWD1) recapitulating intake for the mouse of common nutrient risk factors each at its level consumed in higher risk Western populations. This causes sporadic large and small intestinal tumors in wild-type mice at an incidence and frequency similar to that in humans. NWD1 perturbs intestinal cell maturation and Wnt signaling throughout villi and colonic crypts and decreases mouse Lgr5hi intestinal stem cell contribution to homeostasis and tumor development. Here we establish that NWD1 transcriptionally reprograms Lgr5hi cells, and that nutrients are interactive in reprogramming. Furthermore, the DNA mismatch repair pathway is elevated in Lgr5hi cells by lower vitamin D3 and/or calcium in NWD1, paralleled by reduced accumulation of relevant somatic mutations detected by single-cell exome sequencing. In compensation, NWD1 also reprograms Bmi1+ cells to function and persist as stem-like cells in mucosal homeostasis and tumor development. The data establish the key role of the nutrient environment in defining the contribution of two different stem cell populations to both mucosal homeostasis and tumorigenesis. This raises important questions regarding impact of variable human diets on which and how stem cell populations function in the human mucosa and give rise to tumors. Moreover, major differences reported in turnover of human and mouse crypt base stem cells may be linked to their very different nutrient exposures.

Vitamin D and the nutritional environment in functions of intestinal stem cells: Implications for tumorigenesis and prevention

Sporadic colon cancer accounts for ∼80% of CRC, with high incidence in western societies strongly linked to dietary patterns. The only mouse model for sporadic CRC results from feeding mice a purified rodent western-style diet (NWD1), establishing mouse intake of several common nutrients that mimic for each its level consumed in western populations at higher risk for colon cancer (higher fat, lower vitamin D3, calcium, methyl donors and fiber). This causes sporadic colon and small intestinal tumors at an incidence and frequency similar to that of humans. NWD1 perturbs intestinal cell maturation and Wnt signaling throughout villi and colonic crypts before tumors are detected. Surprisingly, feeding NWD1 decreases mouse Lgr5hi intestinal stem cell contribution to homeostasis and tumorigenesis, associated with extensive Lgr5hi cell transcriptional reprogramming, with nutrient levels interactive in these effects. There is a key impact of the lower vitamin D3 in NWD1 and its signaling through the Vdr. The DNA mismatch repair pathway is elevated in Lgr5hi cells by lower vitamin D3 and/or calcium in NWD1, reducing accumulation of relevant somatic mutations detected by single cell exome sequencing. There are also alterations in metabolic pathways, including down-regulation of oxidative phosphorylation. In compensation for compromise of Lgr5hi cells, NWD1 also reprograms cells derived from the Bmi1+ population, defined as those cells marked in Bmi1creERT2, Rosa26tom mice following tamoxifen injection, and at least a portion of these cells then function and persist as stem-like cells in mucosal homeostasis and tumorigenesis. The data establish a key role of the nutrient environment, and vitamin D signaling, in defining contribution of at least two different stem cell populations to mucosal homeostasis and tumorigenesis. This raises significant questions regarding impact of variable human diets on which and how multiple potential intestinal stem cell populations function in the human and give rise to tumors. Moreover, genetic and epigenetic changes in long-lived stem cells have important implications for understanding the effects of vitamin D and other nutrients on intestinal homeostasis and on intervention strategies for altering probability of tumor development.