Examination of the mechanism of Piezo ion channel in 5-HT synthesis in the enterochromaffin cell and its association with gut motility.

In the gastrointestinal tract, serotonin (5-hydroxytryptamine, 5-HT) is an important monoamine that regulates intestinal dynamics. QGP-1 cells are human-derived enterochromaffin cells that secrete 5-HT and functionally express Piezo ion channels associated with cellular mechanosensation. Piezo ion channels can be blocked by Grammostola spatulata mechanotoxin 4 (GsMTx4), a spider venom peptide that inhibits cationic mechanosensitive channels. The primary aim of this study was to explore the effects of GsMTx4 on 5-HT secretion in QGP-1 cells in vitro. We investigated the transcript and protein levels of the Piezo1/2 ion channel, tryptophan hydroxylase 1 (TPH1), and mitogen-activated protein kinase signaling pathways. In addition, we observed that GsMTx4 affected mouse intestinal motility in vivo. Furthermore, GsMTx4 blocked the response of QGP-1 cells to ultrasound, a mechanical stimulus.The prolonged presence of GsMTx4 increased the 5-HT levels in the QGP-1 cell culture system, whereas Piezo1/2 expression decreased, and TPH1 expression increased. This effect was accompanied by the increased phosphorylation of the p38 protein. GsMTx4 increased the entire intestinal passage time of carmine without altering intestinal inflammation. Taken together, inhibition of Piezo1/2 can mediate an increase in 5-HT, which is associated with TPH1, a key enzyme for 5-HT synthesis. It is also accompanied by the activation of the p38 signaling pathway. Inhibitors of Piezo1/2 can modulate 5-HT secretion and influence intestinal motility.

Adrenergic nerves regulate intestinal regeneration through IL-22 signaling from type 3 innate lymphoid cells.

The intestinal epithelium has high intrinsic turnover rate, and the precise renewal of the epithelium is dependent on the microenvironment. The intestine is innervated by a dense network of peripheral nerves that controls various aspects of intestinal physiology. However, the role of neurons in regulating epithelial cell regeneration remains largely unknown. Here, we investigated the effects of gut-innervating adrenergic nerves on epithelial cell repair following irradiation (IR)-induced injury. We observed that adrenergic nerve density in the small intestine increased post IR, while chemical adrenergic denervation impaired epithelial regeneration. Single-cell RNA sequencing experiments revealed a decrease in IL-22 signaling post IR in denervated animals. Combining pharmacologic and genetic tools, we demonstrate that ß-adrenergic receptor signaling drives IL-22 production from type 3 innate lymphoid cells (ILC3s) post IR, which in turn promotes epithelial regeneration. These results define an adrenergic-ILC3 axis important for intestinal regeneration.

Microbial experience through housing in a farmyard-type environment alters intestinal barrier properties in mouse colons.

To close the gap between ultra-hygienic research mouse models and the much more environmentally exposed conditions of humans, we have established a system where laboratory mice are raised under a full set of environmental factors present in a naturalistic, farmyard-type habitat-a process we have called feralization. In previous studies we have shown that feralized (Fer) mice were protected against colorectal cancer when compared to conventionally reared laboratory mice (Lab). However, the protective mechanisms remain to be elucidated. Disruption of the protective intestinal barrier is an acknowledged player in colorectal carcinogenesis, and in the current study we assessed colonic mucosal barrier properties in healthy, feralized C57BL/6JRj male mice. While we found no effect of feralization on mucus layer properties, higher expression of genes encoding the mucus components Fcgbp and Clca1 still suggested mucus enforcement due to feralization. Genes encoding other proteins known to be involved in bacterial defense (Itln1, Ang1, Retnlb) and inflammatory mechanisms (Zbp1, Gsdmc2) were also higher expressed in feralized mice, further suggesting that the Fer mice have an altered intestinal mucosal barrier. These findings demonstrate that microbial experience conferred by housing in a farmyard-type environment alters the intestinal barrier properties in mice possibly leading to a more robust protection against disease. Future studies to unravel regulatory roles of feralization on intestinal barrier should aim to conduct proteomic analyses and in vivo performance of the feralized mice intestinal barrier.

Glutamine boosts intestinal stem cell-mediated small intestinal epithelial development during early weaning: Involvement of WNT signaling.

Early weaning usually causes small intestine epithelial development abnormality, increasing the risk of gastrointestinal diseases. Glutamine (Gln), enriching in plasma and milk, is widely reported to benefit intestinal health. However, whether Gln affects intestinal stem cell (ISC) activity in response to early weaning is unclear. Here, both the early weaning mice and intestinal organoids were used to study the role of Gln in regulating ISC activities. Results showed that Gln ameliorated early weaning-induced epithelial atrophy and augmented the ISC-mediated epithelial regeneration. Gln deprivation disabled ISC-mediated epithelial regeneration and crypt fission in vitro. Mechanistically, Gln augmented WNT signaling in a dose-dependent manner to regulate ISC activity, while WNT signaling blockage abolished the effects of Gln on ISCs. Together, Gln accelerates stem cell-mediated intestinal epithelial development associated with the augmentation of WNT signaling, which provides novel insights into the mechanism by which Gln promotes intestinal health.

Intestinal mucus components and secretion mechanisms: what we do and do not know.

Damage to the colon mucus barrier, the first line of defense against microorganisms, is an important determinant of intestinal diseases such as inflammatory bowel disease and colorectal cancer, and disorder in extraintestinal organs. The mucus layer has attracted the attention of the scientific community in recent years, and with the discovery of new mucosal components, it has become increasingly clear that the mucosal barrier is a complex system composed of many components. Moreover, certain components are jointly involved in regulating the structure and function of the mucus barrier. Therefore, a comprehensive and systematic understanding of the functional components of the mucus layer is clearly warranted. In this review, we summarize the various functional components of the mucus layer identified thus far and describe their unique roles in shaping mucosal structure and function. Furthermore, we detail the mechanisms underlying mucus secretion, including baseline and stimulated secretion. In our opinion, baseline secretion can be categorized into spontaneous Ca2+ oscillation-mediated slow and continuous secretion and stimulated secretion, which is mediated by massive Ca2+ influx induced by exogenous stimuli. This review extends the current understanding of the intestinal mucus barrier, with an emphasis on host defense strategies based on fortification of the mucus layer.

Microbe-mediated intestinal NOD2 stimulation improves linear growth of undernourished infant mice.

The intestinal microbiota is known to influence postnatal growth. We previously found that a strain of Lactiplantibacillus plantarum (strain LpWJL) buffers the adverse effects of chronic undernutrition on the growth of juvenile germ-free mice. Here, we report that LpWJL sustains the postnatal growth of malnourished conventional animals and supports both insulin-like growth factor-1 (IGF-1) and insulin production and activity. We have identified cell walls isolated from LpWJL, as well as muramyl dipeptide and mifamurtide, as sufficient cues to stimulate animal growth despite undernutrition. Further, we found that NOD2 is necessary in intestinal epithelial cells for LpWJL-mediated IGF-1 production and for postnatal growth promotion in malnourished conventional animals. These findings indicate that, coupled with renutrition, bacteria cell walls or purified NOD2 ligands have the potential to alleviate stunting.

Claudin-3 is a novel intestinal integrity marker in patients with alopecia areata: Correlation with the disease severity.

BACKGROUND: The development of alopecia areata is suggested to be influenced by intestinal permeability and gut dysbiosis. Claudin-3, an essential component of tight junctions which may act as an indicator of intestinal barrier integrity. AIMS: The study's objective was to evaluate the plasma concentration level of Claudin-3 in alopecia areata patients and its relationship to the severity of the condition. PATIENTS AND METHODS: In this case-control study, 50 alopecia areata patients and 30 healthy age and sex controls were involved. An enzyme-linked immunosorbent assay was used to determine the concentration of claudin-3 in the blood. RESULTS: Patients with alopecia areata had significantly higher plasma claudin-3 concentrations than healthy controls [median (interquartile range), 7.73 ng/ml (4.49-33.7) vs. 6.14 ng/ml (4.45-15.6), p < 0.005]. Positive relations were found between claudin-3 and SALT score (r = 0.675 & p-value < 0.001). CONCLUSIONS: Claudin-3, a gut permeability biomarker, is elevated in alopecia areata and correlates with disease severity.

Maresin-2 promotes mucosal repair and has therapeutic potential when encapsulated in thermostable nanoparticles.

Resolution of inflammation and mucosal wound healing are crucial processes required to re-establish homeostasis following injury of mucosal tissues. Maresin-2 (MaR2), a lipid specialized pro-resolving mediator derived from omega-3 polyunsaturated fatty acid, has been reported to promote resolution of inflammation. However, a potential role for MaR2 in regulating mucosal repair remains undefined. Using lipidomic analyses, we demonstrate biosynthesis of MaR2 in healing intestinal mucosal wounds in vivo. Importantly, administration of exogenous MaR2 promoted mucosal repair following dextran sulfate sodium-induced colitis or biopsy-induced colonic mucosal injury. Functional analyses revealed that MaR2 promotes mucosal wound repair by driving intestinal epithelial migration through activation of focal cell-matrix adhesion signaling in primary human intestinal epithelial cells. Because of its labile nature, MaR2 is easily degradable and requires ultracold storage to maintain functionality. Thus, we created thermostable polylactic acid MaR2 nanoparticles that retain biological activity following extended storage at 4 °C or above. Taken together, these results establish MaR2 as a potent pro-repair lipid mediator with broad therapeutic potential for use in promoting mucosal repair in inflammatory diseases.

Noncoding RNA circBtnl1 suppresses self-renewal of intestinal stem cells via disruption of Atf4 mRNA stability.

Intestinal stem cells (ISCs) at the crypt base are responsible for the regeneration of the intestinal epithelium. However, how ISC self-renewal is regulated still remains unclear. Here we identified a circular RNA, circBtnl1, that is highly expressed in ISCs. Loss of circBtnl1 in mice enhanced ISC self-renewal capacity and epithelial regeneration, without changes in mRNA and protein levels of its parental gene Btnl1. Mechanistically, circBtnl1 and Atf4 mRNA competitively bound the ATP-dependent RNA helicase Ddx3y to impair the stability of Atf4 mRNA in wild-type ISCs. Furthermore, ATF4 activated Sox9 transcription by binding to its promoter via a unique motif, to enhance the self-renewal capacity and epithelial regeneration of ISCs. In contrast, circBtnl1 knockout promoted Atf4 mRNA stability and enhanced ATF4 expression, which caused Sox9 transcription to potentiate ISC stemness. These data indicate that circBtnl1-mediated Atf4 mRNA decay suppresses Sox9 transcription that negatively modulates self-renewal maintenance of ISCs.

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.

Proteolipid protein 1 is involved in the regulation of intestinal motility and barrier function in the mouse.

Proteolipid protein 1 (Plp1) is highly expressed in enteric glia, labeling cells throughout the mucosa, muscularis, and the extrinsic innervation. Plp1 is a major constituent of myelin in the central and peripheral nervous systems, but the absence of myelin in the enteric nervous system (ENS) suggests another role for Plp1 in the gut. Although the functions of enteric glia are still being established, there is strong evidence that they regulate intestinal motility and permeability. To interrogate the role of Plp1 in enteric glia, we investigated gut motility, secretomotor function and permeability, and evaluated the ENS in mice lacking Plp1. We studied two time points: ∼3 mo (young) and >1 yr (old). Old Plp1 null mice exhibited increased fecal output, decreased fecal water content, faster whole gut transit times, reduced intestinal permeability, and faster colonic migrating motor complexes. Interestingly, in both young and old mice, the ENS exhibited normal glial and neuronal numbers as well as glial arborization density in the absence of Plp1. As Plp1-associated functions involve mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 (Mapk/Erk1/2) signaling and Mapk/Erk1/2 are reported to have a regulatory role in intestinal motility, we measured protein expression of Erk1/2 and its active form in the small intestine. Old Plp1 null mice had reduced levels of phosphorylated-Erk1/2. Although Plp1 is not required for the normal appearance of enteric glial cells, it has a regulatory role in intestinal motility and barrier function. Our results suggest that functional changes mediated by Plp1-expressing enteric glia may involve Erk1/2 activation.NEW & NOTEWORTHY Here, we describe that Plp1 regulates gut motility and barrier function. The functional effects of Plp1 eradication are only seen in old mice, not young. The effects of Plp1 appear to be mediated through the Erk1/2 pathway.

Outcome of a novel porcine-derived UBM/SIS composite biological mesh in a rabbit vaginal defect model.

INTRODUCTION AND HYPOTHESIS: To investigate the tissue reactions of a novel porcine-derived urinary bladder matrix/small intestinal submucosa (UBM/SIS) biological mesh and SIS mesh implanted in a rabbit vaginal defect model. METHODS: Thirty-two rabbits were implanted with UBM/SIS mesh (Group A) and SIS mesh (Group B), respectively. Rabbits were sacrificed at 7, 14, 60, and 180 days after implantation. The tensile strength, elongation at break, and elastic modulus of the tissue were measured using biomechanical methods. The inflammatory response, cell infiltration, vascularization, and collagen fibers were observed. RESULTS: Compared with Group B, the tensile strength and elongation at break of group A was higher at 14, 60, and 180 days. The elastic modulus of group A was lower at 180 days. Inflammatory response of group A was milder at 14, 60, and 180 days. There was more cell infiltration in group A at 7 and 14 days. Vascularization was higher in group A at 7 days and 14 days. The order of collagen in group A was better at 14, 60, and 180 days. The proportion of thick red fibers in both groups showed an increasing trend. At 14 days, group A had more thick red fibers. CONCLUSIONS: The novel UBM/SIS composite mesh had a milder inflammatory response; earlier induction of cell infiltration, angiogenesis, and collagen regeneration. Collagen fibers had a better order. It has a higher tensile strength and greater elongation at break, and can be used as a potential material for the treatment of pelvic organ prolapse.

Epithelial RAC1-dependent cytoskeleton dynamics controls cell mechanics, cell shedding and barrier integrity in intestinal inflammation.

OBJECTIVE: Increased apoptotic shedding has been linked to intestinal barrier dysfunction and development of inflammatory bowel diseases (IBD). In contrast, physiological cell shedding allows the renewal of the epithelial monolayer without compromising the barrier function. Here, we investigated the role of live cell extrusion in epithelial barrier alterations in IBD. DESIGN: Taking advantage of conditional GGTase and RAC1 knockout mice in intestinal epithelial cells (Pggt1b iΔIEC and Rac1 iΔIEC mice), intravital microscopy, immunostaining, mechanobiology, organoid techniques and RNA sequencing, we analysed cell shedding alterations within the intestinal epithelium. Moreover, we examined human gut tissue and intestinal organoids from patients with IBD for cell shedding alterations and RAC1 function. RESULTS: Epithelial Pggt1b deletion led to cytoskeleton rearrangement and tight junction redistribution, causing cell overcrowding due to arresting of cell shedding that finally resulted in epithelial leakage and spontaneous mucosal inflammation in the small and to a lesser extent in the large intestine. Both in vivo and in vitro studies (knockout mice, organoids) identified RAC1 as a GGTase target critically involved in prenylation-dependent cytoskeleton dynamics, cell mechanics and epithelial cell shedding. Moreover, inflamed areas of gut tissue from patients with IBD exhibited funnel-like structures, signs of arrested cell shedding and impaired RAC1 function. RAC1 inhibition in human intestinal organoids caused actin alterations compatible with arresting of cell shedding. CONCLUSION: Impaired epithelial RAC1 function causes cell overcrowding and epithelial leakage thus inducing chronic intestinal inflammation. Epithelial RAC1 emerges as key regulator of cytoskeletal dynamics, cell mechanics and intestinal cell shedding. Modulation of RAC1 might be exploited for restoration of epithelial integrity in the gut of patients with IBD.

Regulation of homeostasis and regeneration in the adult intestinal epithelium by the TGF-ß superfamily.

The delicate balance between the homeostatic maintenance and regenerative capacity of the intestine makes this a fascinating tissue of study. The intestinal epithelium undergoes continuous homeostatic renewal but is also exposed to a diverse array of stresses that can range from physiological processes such as digestion to exposure to infectious agents, drugs, radiation therapy, and inflammatory stimuli. The intestinal epithelium has thus evolved to efficiently maintain and reinstate proper barrier function that is essential for intestinal integrity and function. Factors governing homeostatic epithelial turnover are well described; however, the dynamic regenerative mechanisms that occur following injury are the subject of intense ongoing investigations. The TGF-ß superfamily is a key regulator of both homeostatic renewal and regenerative processes of the intestine. Here, we review the roles of TGF-ß and BMP on the adult intestinal epithelium during self-renewal and injury to provide a framework for understanding how this major family of morphogens can tip the scale between intestinal health and disease.

Lactobacillus reuteri 1 Enhances Intestinal Epithelial Barrier Function and Alleviates the Inflammatory Response Induced by Enterotoxigenic Escherichia coli K88 via Suppressing the MLCK Signaling Pathway in IPEC-J2 Cells.

Intestinal epithelial barrier injury disrupts immune homeostasis and leads to many intestinal disorders. Lactobacillus reuteri (L. reuteri) strains can influence immune system development and intestinal function. However, the underlying mechanisms of L. reuteri LR1 that regulate inflammatory response and intestinal integrity are still unknown. The present study aimed to determine the effects of LR1 on the ETEC K88-induced intestinal epithelial injury on the inflammatory response, intestinal epithelial barrier function, and the MLCK signal pathway and its underlying mechanism. Here, we showed that the 1 × 109 cfu/ml LR1 treatment for 4 h dramatically decreased interleukin-8 (IL-8) and IL-6 expression. Then, the data indicated that the 1 × 108 cfu/ml ETEC K88 treatment for 4 h dramatically enhanced IL-8, IL-6, and tumor necrosis factor-α (TNF-α) expression. Furthermore, scanning electron microscope (SEM) data indicated that pretreatment with LR1 inhibited the ETEC K88 that adhered on IPEC-J2 and alleviated the scratch injury of IPEC J2 cells. Moreover, LR1 pretreatment significantly reversed the declined transepithelial electrical resistance (TER) and tight junction protein level, and enhanced the induction by ETEC K88 treatment. Additionally, LR1 pretreatment dramatically declined IL-8, IL-17A, IL-6, and TNF-α levels compared with the ETEC K88 group. Then, ETEC K88-treated IPEC-J2 cells had a higher level of myosin light-chain kinase (MLCK), higher MLC levels, and a lower Rho-associated kinase (ROCK) level than the control group, while LR1 pretreatment significantly declined the MLCK and MLC expression and enhanced ROCK level in the ETEC K88-challenged IPEC-J2 cells. Mechanistically, depletion of MLCK significantly declined MLC expression in IPEC-J2 challenged with ETEC K88 compared to the si NC+ETEC K88 group. On the other hand, the TER of the si MLCK+ETEC K88 group was higher and the FD4 flux in the si MLCK+ETEC K88 group was lower compared with the si NC+ETEC K88 group. In addition, depletion of MLCK significantly enhanced Claudin-1 level and declined IL-8 and TNF-α levels in IPEC-J2 pretreated with LR1 followed by challenging with ETEC K88. In conclusion, our work indicated that L. reuteri LR1 can decline inflammatory response and improve intestinal epithelial barrier function through suppressing the MLCK signal pathway in the ETEC K88-challenged IPEC-J2.

Role of CB1 receptors in the acute regulation of small intestinal permeability: effects of high-fat diet.

The endocannabinoid system of the gastrointestinal tract is involved in the control of intestinal barrier function. Whether the cannabinoid 1 (CB1) receptor is expressed on the intestinal epithelium and acutely regulates barrier function has not been determined. Here, we tested the hypothesis that ligands of the CB1 receptor acutely modulate small intestinal permeability and that this is associated with altered distribution of tight junction proteins. We examined the acute effects of CB1 receptor ligands on small intestinal permeability both in chow-fed and 2-wk high-fat diet (HFD)-fed mice using Ussing chambers. We assessed the distribution of CB1 receptor and tight junction proteins using immunofluorescence and the expression of CB1 receptor using PCR. A low level of CB1 expression was found on the intestinal epithelium. CB1 receptor was highly expressed on enteric nerves in the lamina propria. Neither the CB1/CB2 agonist CP55,940 nor the CB1 neutral antagonist AM6545 altered the flux of 4kDa FITC dextran (FD4) across the jejunum or ileum of chow-fed mice. Remarkably, both CP55,940 and AM6545 reduced FD4 flux across the jejunum and ileum in HFD-fed mice that have elevated baseline intestinal permeability. These effects were absent in CB1 knockout mice. CP55,940 reduced the expression of claudin-2, whereas AM6545 had little effect on claudin-2 expression. Neither ligand altered the expression of ZO-1. Our data suggest that CB1 receptor on the intestinal epithelium regulates tight junction protein expression and restores barrier function when it is increased following exposure to a HFD for 2 wk.NEW & NOTEWORTHY The endocannabinoid system of the gastrointestinal tract regulates homeostasis by acting as brake on motility and secretion. Here we show that when exposed to a high fat diet, intestinal permeability is increased and activation of the CB1 receptor on the intestinal epithelium restores barrier function. This work further highlights the role of the endocannabinoid system in regulating intestinal homeostasis when it is perturbed.

Foodborne compounds that alter plasma membrane architecture can modify the response of intestinal cells to shear stress in vitro.

In order to ensure barrier function, intestinal cells need to respond promptly to biomechanical stimulation and to adapt constantly to physical cues. To this aim, cell membranes are essential and rely extensively on lipid metabolism and turnover. These can be tuned via nutrition, pharmacological treatment, or exposure to xenobiotics, however, knowledge on the impact of lifestyle and diet on intestinal cells' biomechanical compliance is relatively limited. Building on this, two intestinal cell models (non-transformed human colon epithelial cells HCEC-1CT and the colon adenocarcinoma cell line HT-29) were systematically compared in terms of cholesterol content, membrane fluidity, actin cytoskeletal organization, expression of mechano-gated PIEZO1 channels and caveolin-1. Biomechanical compliance was evaluated with the application of fluid shear stress (force response 0.75-1.5 dyn/cm2). As model substances the food contaminant mycotoxin alternariol (AOH, 0.01-10 µM) was chosen in virtue of its putative structural analogy with cholesterol. AOH was compared to the cholesterol lowering agent lovastatin (LOVA, 0.01-10 µM) and to water-soluble cholesterol (MßCD-CHOL, 0.01-10 µg/ml). Exposure to AOH, LOVA and MßCD-CHOL coherently modulated membrane cholesterol, expression of PIEZO1 and caveolin-1 as well as the formation of actin stress fibers. These effects were functionally relevant since they modified the force response profile to fluid shear stress (morphological adaption and [Ca2+]i). In sum, we could demonstrate a novel role for exogenous or endogenous molecules in shaping intestinal mechanotransduction via regulation of cholesterol homeostasis and plasma membrane architecture.

Thyroid hormone receptor α controls larval intestinal epithelial cell death by regulating the CDK1 pathway.

Thyroid hormone (T3) regulates adult intestine development through T3 receptors (TRs). It is difficult to study TR function during postembryonic intestinal maturation in mammals due to maternal influence. We chose intestinal remodeling during Xenopus tropicalis metamorphosis as a model to study TR function in adult organ development. By using ChIP (chromatin immunoprecipitation)-Seq, we identified over 3000 TR-bound genes in the intestine of premetamorphic wild type or TRα (the major TR expressed during premetamorphosis)-knockout tadpoles. Surprisingly, cell cycle-related GO (gene ontology) terms and biological pathways were highly enriched among TR target genes even though the first major event during intestinal metamorphosis is larval epithelial cell death, and TRα knockout drastically reduced this enrichment. More importantly, treatment of tadpoles with cell cycle inhibitors blocked T3-induced intestinal remodeling, especially larval epithelial cell death, suggesting that TRα-dependent activation of cell cycle is important for T3-induced apoptosis during intestinal remodeling.

Nfatc1+ colonic stem cells contribute to regeneration upon colitis.

BACKGROUND AND AIM: Colonic stem cells play important roles in both normal epithelial turnover and injury repair. Lgr5+ colonic stem cells are highly susceptible to DSS-induced damage. However, it is still unclear how colonic stem cells regenerate injured epithelium during colitis. Here, we explored the functions of a new population of NFATc1+ colonic stem cells in experimental colitis. METHODS: Nfatc1+ colonic stem cells were labeled using Nfatc1CreERT2 ;R26mTmG reporter mice. Immunostaining assays were used to detect Goblet cells, enteroendocrine cells, and intestinal stem/progenitor cells. We performed lineage tracing assay to investigate whether Nfatc1+ cells are real colonic stem cells using Nfatc1CreERT2 ;R26mTmG mice. The contribution of Nfatc1+ stem cells on epithelial regeneration was detected in experimental colitis induced by DSS. RESULTS: Nfatc1-reporter marked cells are enriched for +3 to +5 position in colonic crypts, and they are overlapped with Sox9+ cells and Hopx+ cells that have been identified as stem cells in small intestine. However, Nfatc1-reporter marked cells are not overlapped with Lgr5+ colonic stem cells, as well as differentiated goblet cells and enteroendocrine cells. Furthermore, Nfatc1-reporter marked cells are able to give rise to all lineages of the colonic epithelium, and they preferentially contribute to the regeneration of colonic epithelium in DSS-induced experimental colitis. CONCLUSION: Nfatc1+ cells were identified as a novel population of colonic stem cells that are primarily located at +3 to +5 position and contribute to epithelial regeneration during colitis.