Intestinal Epithelial Regeneration Research Articles

Qingchang Wenzhong Decoction Accelerates Intestinal Mucosal Healing Through Modulation of Dysregulated Gut Microbiome, Intestinal Barrier and Immune Responses in Mice.

Inflammatory bowel disease (IBD), a group of multifactorial and inflammatory infirmities, is closely associated with dysregulation of gut microbiota and host metabolome, but effective treatments are currently limited. Qingchang Wenzhong Decoction (QCWZD) is an effective and classical traditional herbal prescription for the treatment of IBD and has been proved to attenuate intestinal inflammation in a model of acute colitis. However, the role of QCWZD in recovery phase of colitis is unclear. Here, we demonstrated that mice treated with QCWZD showed a faster recovery from dextran sulfate sodium (DSS)-induced epithelial injury, accompanied by reduced mucosal inflammation and attenuated intestinal dysbiosis using bacterial 16S rRNA amplicon sequencing compared to those receiving sterile water. The protective effects of QCWZD are gut microbiota dependent, as demonstrated by fecal microbiome transplantation and antibiotics treatment. Gut microbes transferred from QCWZD-treated mice displayed a similar role in mucosal protection and epithelial regeneration as QCWZD on colitis in mice, and depletion of the gut microbiota through antibiotics treatments diminished the beneficial effects of QCWZD on colitis mice. Moreover, metabolomic analysis revealed metabolic profiles alternations in response to the gut microbiota reprogrammed by QCWZD intervention, especially enhanced tryptophan metabolism, which may further accelerate intestinal stem cells-mediated epithelial regeneration to protect the integrity of intestinal mucosa through activation of Wnt/β-catenin signals. Collectively, our results suggested that orally administrated QCWZD accelerates intestinal mucosal healing through the modulation of dysregulated gut microbiota and metabolism, thus regulating intestinal stem cells-mediated epithelial proliferation, and hold promise for novel microbial-based therapies in the treatment of IBD.

Glucomannan from Aloe vera Gel Promotes Intestinal Stem Cell-Mediated Epithelial Regeneration via the Wnt/β-Catenin Pathway.

Intestinal stem cells (ISCs) are essential to maintain intestinal epithelial regeneration and barrier function. Our previous work showed that glucomannan from Aloe vera gel (AGP) alleviated epithelial damage, but the mechanism was still elusive. Herein, RNA-sequencing analysis showed that proliferation and differentiation of intestinal epithelial cells as well as the canonical Wnt pathway were involved in this process. Further experiments exhibited that AGP promoted nuclear translocation of β-catenin and expression of transcription factor 7, increased the number of Lgr5+ ISCs, and differentiated epithelial cells in mice colon. Intriguingly, AGP reversed the inhibition of IEC-6 cells proliferation induced by an inhibitor of the canonical Wnt pathway. Hence, this study implied that AGP promoted proliferation and differentiation of colon stem cells via Wnt/β-catenin signaling, which subsequently facilitated the regeneration of epithelial cells and alleviated colitis in mice. It may provide new insights into the role of polysaccharides in regulating intestinal homeostasis and relieving intestinal injury.

Source and Impact of the EGF Family of Ligands on Intestinal Stem Cells.

Epidermal Growth Factor (EGF) has long been known for its role in promoting proliferation of intestinal epithelial cells. EGF is produced by epithelial niche cells at the base of crypts in vivo and is routinely added to the culture medium to support the growth of intestinal organoids ex vivo. The recent identification of diverse stromal cell populations that reside underneath intestinal crypts has enabled the characterization of key growth factor cues supplied by these cells. The nature of these signals and how they are delivered to drive intestinal epithelial development, daily homeostasis and tissue regeneration following injury are being investigated. It is clear that aside from EGF, other ligands of the family, including Neuregulin 1 (NRG1), have distinct roles in supporting the function of intestinal stem cells through the ErbB pathway.

L-Carnosine Protects Against Deoxynivalenol-Induced Oxidative Stress in Intestinal Stem Cells by Regulating the Keap1/Nrf2 Signaling Pathway.

The intestinal epithelium is nourished by various nutrients and subjected to persistent and widespread feed-derived mycotoxin stress. l-Carnosine (LC) possesses robust antioxidant activity; however, its role in protecting intestinal mucosa against deoxynivalenol (DON) is still unclear. In this study, 300mg kg-1 BW LC and 3mg kg-1 BW DON are orally administered to mice either alone or in combination for 10 days to investigate the role of LC in protecting the intestine against DON. This study found that LC alleviates the growth retardation of mice and repairs the damaged jejunal structure and barrier functions under DON exposure. LC rescues the intestinal stem cells (ISCs), increases the growth advantage in enteroids derived from jejunal crypts of mice in each group ex vivo, improves the proliferation and apoptosis of intestinal cells, and promotes ISC differentiation into absorptive cells, goblet cells, and Paneth cells. Furthermore, LC activates Nrf2 signaling by binding to Keap1 to reverse the striking DON-induced increase in ROS levels. The study findings unveil that LC potentiates the antioxidant capacity of ISCs by regulating the Keap1/Nrf2 signaling pathway, which contributes to the intestinal epithelial regeneration response to DON insult.

Exopolysaccharides from Lactobacillus plantarum NCU116 Facilitate Intestinal Homeostasis by Modulating Intestinal Epithelial Regeneration and Microbiota.

Regeneration of epithelia is crucial for maintaining the intestinal barrier and homeostasis. Our previous work showed that exopolysaccharides from Lactobacillus plantarum NCU116 (EPS116) regulated the barrier function and homeostasis of the intestine; however, the relevant mechanisms remain obscure. Therefore, we sought to explore the role of EPS116 in promoting intestinal epithelial regeneration. Our data showed that the administration of EPS116 markedly ameliorated inflammatory bowel disease-related phenotypes and promoted the regeneration of crypts in the colon of colitis mice. The results of immunofluorescence and reverse transcription-quantitative polymerase chain reaction experiments indicated that EPS116 strikingly increased the number of intestinal stem cells (ISCs) and the expression of differentiation markers for goblet cells, enterocytes, and enteroendocrine cells in the mouse colon. Intestinal microbiota analysis showed that EPS116 increased microbial populations associated with intestinal regeneration and glycan metabolism. Therefore, the present study revealed a novel model that EPS116 promoted the intestinal homeostasis through modulating the proliferation and differentiation of ISCs and altering the gut microbiota profile.

Aging-related upregulation of the homeobox gene caudal represses intestinal stem cell differentiation in Drosophila.

The differentiation efficiency of adult stem cells undergoes a significant decline in aged animals, which is closely related to the decline in organ function and age-associated diseases. However, the underlying mechanisms that ultimately lead to this observed decline of the differentiation efficiency of stem cells remain largely unclear. This study investigated Drosophila midguts and identified an obvious upregulation of caudal (cad), which encodes a homeobox transcription factor. This factor is traditionally known as a central regulator of embryonic anterior-posterior body axis patterning. This study reports that depletion of cad in intestinal stem/progenitor cells promotes quiescent intestinal stem cells (ISCs) to become activate and produce enterocytes in the midgut under normal gut homeostasis conditions. However, overexpression of cad results in the failure of ISC differentiation and intestinal epithelial regeneration after injury. Moreover, this study suggests that cad prevents intestinal stem/progenitor cell differentiation by modulating the Janus kinase/signal transducers and activators of the transcription pathway and Sox21a-GATAe signaling cascade. Importantly, the reduction of cad expression in intestinal stem/progenitor cells restrained age-associated gut hyperplasia in Drosophila. This study identified a function of the homeobox gene cad in the modulation of adult stem cell differentiation and suggested a potential gene target for the treatment of age-related diseases induced by age-related stem cell dysfunction.

Cytokine therapy in necrotizing enterocolitis: A promising treatment for preterm infants

Necrotizing enterocolitis (NEC) is an intestinal disorder that disproportionately affects premature infants and lacks in effective therapeutics. Mihi and colleagues1 demonstrated that the cytokine interleukin-22 promotes intestinal epithelial regeneration and reduces disease severity in an experimental model of NEC.

P016 SZN-1326, a Wnt signal activator, is more efficacious than cyclosporine A in an acute DSS model

Abstract Background Current Inflammatory bowel disease (IBD) treatments focus on inhibition of excessive inflammation, and clinical remission rates have reached a plateau. There is a clear unmet need for agents that directly repair and regenerate the intestinal epithelial barrier as mucosal healing has been associated with reduced hospitalizations and long-term remission. Wnt/β-catenin signaling promotes intestinal stem cell renewal and is crucial for intestinal epithelial homeostasis and regeneration. Fzd5, a Wnt receptor, is highly expressed in intestinal epithelium. We have engineered a FZD5,8 and LRP6 bi-specific IgG1 antibody, SZN-1326, which potently induced Wnt signaling in a Super Top Flash (STF) Luciferase reporter assay, stimulated intestinal organoid growth, increased Wnt target gene Axin2 expression in the colon tissue and ameliorated Dextran Sulfate Sodium (DSS)-induced colitis in mice. The objective of the current studies was to compare the efficacy of SZN-1326, a Wnt signal activator, to Cyclosporine A, which has been shown to have activity in an acute DSS-induced colitis mouse model. Methods To induce acute colitis, 7- to 8-week-old female C57BL/6 mice were given drinking water containing 4.0% (w/v) DSS for 7 days followed by 1.0% DSS for 3 days. Groups of mice were treated either with an isotype control antibody (anti-GFP), one intraperitoneal (IP) injection of SZN-1326 at 2, 6, 20 mg/kg on day 4 or two injections of SZN-1326 at 1, 3, 10 mg/kg on days 4 and 7, or treated daily with Cyclosporine A by oral gavage at 80 mg/kg on days 0–9, and the mice were taken down on day 10. Results Mice subjected to DSS developed severe colitis characterized by profound and sustained weight loss and bloody diarrhea, resulting in the increase of disease activity index (DAI). SZN-1326 treatments improved body weight, decreased fecal score, and reduced DAI much more effectively than Cyclosporine A. Histological evaluation showed SZN-1326 treatments repaired the damaged colon epithelium, decreased colon histology scores of inflammation, mucosal erosion, and goblet cell loss, at doses as low as 1 mg/kg dosed twice or a single dose of 2 mg/kg. In addition, SZN-1326 treatments significantly decreased serum levels of inflammatory cytokines, Lipocalin-2, IL-6 and IL-8, while Cyclosporine A treatment led only to a reduction of Lipocalin-2. Conclusion In an acute mouse IBD model, SZN-1326 at various dosing regimen stimulated intestinal epithelial regeneration, induced mucosal healing and restored the epithelial barrier resulting in reduced inflammation, improved body weight and reduced disease activity. In contrast, Cyclosporine A showed only a mild effect on reducing DAI and lipocalin-2.

P023 SZN-1326, a Wnt agonist, improved epithelial healing and ameliorated colitis in a chronic DSS model, in stark contrast to anti-TNF and anti-IL-12/23p40 antibodies

Abstract Background All currently approved treatments for Inflammatory bowel disease (IBD) and the majority of drugs in the pipeline are anti-inflammatory agents. Clinical remission rates have reached a plateau, and there is an unmet need for agents that directly repair and regenerate the intestinal epithelial barrier as mucosal healing has been associated with improved clinical outcomes. Wnt/β-catenin signaling promotes intestinal stem cell renewal and epithelial regeneration. We have engineered a Wnt activator, SZN-1326, which increased Wnt target gene expression in the colon of mice treated with Dextran Sulfate Sodium (DSS), an animal model of IBD and demonstrated efficacy in the acute and chronic forms of this model. The goal of this study was to compare the efficacy of SZN-1326 to the anti-inflammatory agents anti-TNFα or anti-IL-12/23p40 antibodies in a chronic DSS model. Methods 7- to 8-week old female C57BL6/J mice were administered 3% DSS for three 7-day cycles separated by 7-days off, followed by a 3-day 1% DSS wash-out period. SZN-1326 was injected intraperitoneally (I.P.) at 1, 3, or 10 mg/kg for 2, 4 or 6 doses. Anti-TNFa (MP6-XT22, Biolegend) was injected I.P. at 5 or 25 mg/kg for 4 or 7 doses, and the mice were euthanized on day 38. A separate study examined the efficacy of SZN-1326 relative to anti-IL-12/23p40 (C17.8, Bioxcell) in the same model. Anti-IL12/23p40 antibody at 3 or 10 mg/kg for 4 or 8 doses was given on days 23 or 7 respectively. Results During each cycle of DSS treatment, animals exhibited a marked increase in disease activity index (DAI), characterized by body weight loss, diarrhea and bleeding. SZN-1326 at various dosing regimen (1 mg/kg for 4 doses to 10 mg/kg for 2, 4 or 6 doses) significantly improved body weights and decreased DAI compared to isotype control, while anti-TNFa or anti-IL12/23p40 had no efficacy on body weight restoration or DAI. The antibodies could be detected in the serum in accordance with their doses. Treatment with SZN-1326, but not with anti-TNFα significantly decreased colon inflammation, mucosal erosion and overall histopathological score. Further, SZN-1326 treatment significantly reduced serum levels of IL-6 and lipocalin-2, while anti-TNFa decreased only lipocalin-2 levels and anti-IL12/23p40 reduced serum IL-6 level. Conclusion In a chronic mouse IBD model, SZN-1326 at various dosing regimens stimulated intestinal epithelial regeneration, induced mucosal healing and restored the epithelial barrier resulting in reduced inflammation, improved body weight and reduced disease activity. In contrast, treatment with anti-TNFα or anti-IL-12/23p40 antibodies led to reduction only in certain serum inflammatory cytokines but had no efficacy on DAI or colon histology in this model.

Regulation of IL-6/STAT-3/Wnt axis by nifuroxazide dampens colon ulcer in acetic acid-induced ulcerative colitis model: Novel mechanistic insight

AimUlcerative colitis (UC) is a common intestinal problem characterized by the diffusion of colon inflammation and immunity dysregulation. Nifuroxazide, a potent STAT-3 inhibitor, exhibits diverse pharmacological properties. The present study aimed to elucidate a novel anti-colitis mechanism of nifuroxazide against the acetic acid-induced UC model. MethodsRats were grouped into control (received vehicle), UC (2 ml of 5% acetic acid by intrarectal infusion), UC plus sulfasalazine (100 mg/kg/day, P.O.), UC plus nifuroxazide (25 mg/kg/day, P.O.), and UC plus nifuroxazide (50 mg/kg/day, P.O.) and lasted for 6 days. ResultsThe present study revealed that nifuroxazide significantly reduced UC measures, hematological changes, and histological alteration. In addition, treatment with nifuroxazide significantly down-regulated serum CRP as well as the colonic expressions of MPO, IL-6, TNF-α, TLR-4, NF-κB-p65, JAK1, STAT-3, DKK1 in a dose-dependent manner. Besides, our results showed that the colonic Wnt expression was up-regulated with nifuroxazide treatment. In a dose-dependent manner, nifuroxazide markedly alleviated acetic acid-induced cellular infiltration and improved ulcer healing by increasing intestinal epithelial cell regeneration. SignificanceOur results collectively indicate that nifuroxazide is an effective anti-colitis agent through regulation of colon inflammation and proliferation via modulation IL-6/STAT-3/Wnt signaling pathway.

Suppression of elevated Cdc42 activity promotes the regenerative potential of aged intestinal stem cells

SummaryHomeostasis in the intestinal epithelium is maintained by Lgr5-positive intestinal stem cells (ISCs) located at the base of the crypt. The function of ISCs is reduced upon aging which leads to a decline of regeneration of the intestinal epithelium. We report that aged intestinal crypts present with an elevated activity of the small RhoGTPase Cdc42. Elevation of Cdc42 activity in young animals by genetic means causes premature ISC aging, whereas pharmacological suppression of elevated Cdc42 activity restores organoid formation potential in vitro. Consistent with a critical role of elevated Cdc42 activity in aged ISCs for a reduced regenerative capacity of aged ISCs, suppression of Cdc42 activity in vivo improves crypt regeneration in aged mice. Thus, pharmacological reduction of Cdc42 activity can improve the regeneration of aged intestinal epithelium.

Prostaglandin E2 receptor PTGER4-expressing macrophages promote intestinal epithelial barrier regeneration upon inflammation

ObjectiveDysfunctional resolution of intestinal inflammation and altered mucosal healing are essential features in the pathogenesis of inflammatory bowel disease (IBD). Intestinal macrophages are vital in the process of inflammation resolution,...

Mucin degrader Akkermansia muciniphila accelerates intestinal stem cell-mediated epithelial development

ABSTRACT Mucin-degrading bacteria are densely populated in the intestinal epithelium; however, their interaction with intestinal stem cells (ISCs) and their progeny have not been elucidated. To determine whether mucin-degrading bacteria play a role in gut homeostasis, mice were treated with Akkermansia muciniphila, a specialized species that degrades mucin. Administration of A. muciniphila for 4 weeks accelerated the proliferation of Lgr5+ ISCs and promoted the differentiation of Paneth cells and goblet cells in the small intestine (SI). We found similar effects of A. muciniphila in the colon. The levels of acetic and propionic acids were higher in the cecal contents of A. muciniphila-treated mice than in PBS-treated mice. SI organoids treated with cecal contents obtained from A. muciniphila-treated mice were larger and could be diminished by treatment with G protein-coupled receptor (Gpr) 41/43 antagonists. Pre-treatment of mice with A. muciniphila reduced gut damage caused by radiation and methotrexate. Further, a novel isotype of the A. muciniphila strain was isolated from heathy human feces that showed enhanced function in intestinal epithelial regeneration. These findings suggest that mucin-degrading bacteria (e.g., A. muciniphila) may play a crucial role in promoting ISC-mediated epithelial development and contribute to intestinal homeostasis maintenance.

Bach2 Deficiency Promotes Intestinal Epithelial Regeneration by Accelerating DNA Repair in Intestinal Stem Cells.

SummaryEpithelial regeneration is critical for barrier maintenance and organ function after intestinal injury, although the repair mechanisms are unclear. Here, we found that Bach2 deficiency promotes intestinal epithelial cell proliferation during homeostasis. Moreover, genetic inactivation of Bach2 in mouse intestinal epithelium facilitated crypt regeneration after irradiation, resulting in a reduction in mortality. RNA-sequencing analysis of isolated crypts revealed that Bach2 deficiency altered the expression of numerous genes, including those regulating double-strand break repair. Mechanistic characterizations indicated that Bach2 deletion facilitated DNA repair in intestinal crypt cells, as evidenced by faster resolution of γ-H2AX and 53BP1 foci in Bach2−/− crypt cells, compared with Bach2+/+ control. Together, our studies highlight that Bach2 deficiency promotes intestinal regeneration by accelerating DNA repair in intestinal stem cells after radiation damage.

Upregulation of complement C1q reflects mucosal regeneration in a mouse model of colitis.

Confirming mucosal healing is important in inflammatory bowel disease treatment. Complement C1q-mediated Wnt signaling activation has recently been suggested to mediate tissue repair and mucosal regeneration. We investigated the involvement of complement C1q and Wnt signaling in intestinal mucosal regeneration using a murine colitis model. The colitis model was established by providing C57BL/6J mice with 4% dextran sodium sulfate (DSS) for 1week (inflammation phase) followed by regular water for 2weeks (recovery phase). After 3weeks, we investigated the relationship between C1q in serum and colonic tissue during the inflammation and recovery phases. We assessed Wnt signaling activity by evaluating β-catenin expression in mouse intestinal tissue. Serum C1q levels were elevated during the recovery phase. C1q-specific staining indicated high C1q expression in pathological intestinal tissue during the inflammation and recovery phases. C1q mRNA and protein expression was increased during both phases. Interestingly, C1q-expressing cells were consistent with macrophages (F4/80-positive cells). Moreover, the expression of β-catenin increased in the colonic tissues during the recovery phase of DSS-induced colitis but decreased during the inflammation phase of DSS-induced colitis. C1q expression may mediate Wnt signaling activity and intestinal epithelial regeneration.

Elevating EGFR-MAPK program by a nonconventional Cdc42 enhances intestinal epithelial survival and regeneration.

The regulatory mechanisms enabling the intestinal epithelium to maintain a high degree of regenerative capacity during mucosal injury remain unclear. Ex vivo survival and clonogenicity of intestinal stem cells (ISCs) strictly required growth response mediated by cell division control 42 (Cdc42) and Cdc42-deficient enteroids to undergo rapid apoptosis. Mechanistically, Cdc42 engaging with EGFR was required for EGF-stimulated, receptor-mediated endocytosis and sufficient to promote MAPK signaling. Proteomics and kinase analysis revealed that a physiologically, but nonconventionally, spliced Cdc42 variant 2 (V2) exhibited stronger MAPK-activating capability. Human CDC42-V2 is transcriptionally elevated in some colon tumor tissues. Accordingly, mice engineered to overexpress Cdc42-V2 in intestinal epithelium showed elevated MAPK signaling, enhanced regeneration, and reduced mucosal damage in response to irradiation. Overproducing Cdc42-V2 specifically in mouse ISCs enhanced intestinal regeneration following injury. Thus, the intrinsic Cdc42-MAPK program is required for intestinal epithelial regeneration, and elevating this signaling cascade is capable of initiating protection from genotoxic injury.

Adipose-derived mesenchymal stem cells alleviate TNBS-induced colitis in rats by influencing intestinal epithelial cell regeneration, Wnt signaling, and T cell immunity.

BACKGROUNDConventional Crohn’s disease (CD) treatments are supportive rather than curative and have serious side effects. Adipose-derived mesenchymal stem cells (ADSCs) have been gradually applied to treat various diseases. The therapeutic effect and underlying mechanism of ADSCs on CD are still not clear.AIMTo investigate the effect of ADSC administration on CD and explore the potential mechanisms.METHODSWistar rats were administered with 2,4,6-trinitrobenzene sulfonic acid (TNBS) to establish a rat model of CD, followed by tail injections of green fluorescent protein (GFP)-modified ADSCs. Flow cytometry, qRT-PCR, and Western blot were used to detect changes in the Wnt signaling pathway, T cell subtypes, and their related cytokines.RESULTSThe isolated cells showed the characteristics of ADSCs, including spindle-shaped morphology, high expression of CD29, CD44, and CD90, low expression of CD34 and CD45, and osteogenic/adipogenic ability. ADSC therapy markedly reduced disease activity index and ameliorated colitis severity in the TNBS-induced rat model of CD. Furthermore, serum anti-sacchromyces cerevisiae antibody and p-anti-neutrophil cytoplasmic antibody levels were significantly reduced in ADSC-treated rats. Mechanistically, the GFP-ADSCs were colocalized with intestinal epithelial cells (IECs) in the CD rat model. GFP-ADSC delivery significantly antagonized TNBS-induced increased canonical Wnt pathway expression, decreased noncanonical Wnt signaling pathway expression, and increased apoptosis rates and protein level of cleaved caspase-3 in rats. In addition, ADSCs attenuated TNBS-induced abnormal inflammatory cytokine production, disturbed T cell subtypes, and their related markers in rats.CONCLUSIONSuccessfully isolated ADSCs show therapeutic effects in CD by regulating IEC proliferation, the Wnt signaling pathway, and T cell immunity.

Weissella paramesenteroides WpK4 ameliorate the experimental amoebic colitis by increasing the expression of MUC-2 and the intestinal epithelial regeneration.

This study evaluates the action of Weissella paramesenteroides WpK4 on amoebic colitis. Weissella paramesenteroides WpK4 was administered in Entamoeba dispar infected and noninfected mice and clinical parameters were evaluated. Following 7days, the caeca were collected for histopathology, morphometry and immunohistochemical staining of MUC-2, CDC-47 and IgA. The treatment reduced diarrhoea and the presence of blood in the faeces and diminished the area of necrosis, also causing weight gain. Also, the addition of this bacterium enhanced the expression of the mucin (MUC-2). The reduction in necrosis and increased CDC-47 expression indicates significant epithelial regeneration. The negative correlation between CDC-47 and the necrosis area reveals that the bacterium favoured the recovery of the necrotic regions and the positive correlation found between the expression of MUC-2 and CDC-47 indicates that the epithelial regeneration also supports the synthesis of MUC-2. Weissella paramesenteroides WpK4 was able to increase the protection of the intestinal mucosa against experimental amoebic colitis through the increase of MUC-2 and epithelial regeneration. Weissella paramesenteroides WpK4 presents the potential to become a complementary tool in the treatment of amoebic colitis.

LIF is essential for ISC function and protects against radiation-induced gastrointestinal syndrome

Leukemia inhibitory factor (LIF) is a cytokine essential for maintaining pluripotency of mouse embryonic stem cells. However, its role in adult intestinal stem cells (ISCs) is unclear. The adult intestinal epithelium has a high self-renewal rate driven by ISCs in crypts. Here, we find that LIF is present in the ISC niche in crypts and critical for the function of ISCs in maintaining the intestinal epithelial homeostasis and regeneration. Mechanistically, LIF maintains β-catenin activity through the AKT/GSK3β signaling to regulate ISC functions. LIF deficiency in mice impairs the renewal of the intestinal epithelium under the physiological condition. Further, LIF deficiency in mice impairs the regeneration of intestinal epithelium in response to radiation and shortens the lifespan of mice after high doses of radiation due to gastrointestinal (GI) syndrome, which can be rescued by administering recombinant LIF (rLIF). Importantly, LIF exhibits a radioprotective role in wild-type (WT) mice by protecting mice from lethal radiation-induced GI syndrome; administering rLIF promotes intestinal epithelial regeneration and prolongs survival in WT mice after radiation. These results reveal a previously unidentified and a crucial role of LIF in ensuring ISC function, promoting regeneration of the intestinal epithelium in response to radiation and protecting against radiation-induced GI syndrome.

Bile Acids Signal via TGR5 to Activate Intestinal Stem Cells and Epithelial Regeneration

Renewal and patterning of the intestinal epithelium is coordinated by intestinal stem cells (ISCs); dietary and metabolic factors provide signals to the niche that control ISC activity. Bile acids (BAs), metabolites in the gut, signal nutrient availability by activating the G protein-coupled bile acid receptor 1 (GPBAR1, also called TGR5). TGR5 is expressed in the intestinal epithelium, but it is not clearhowitsactivation affects ISCs and regeneration of the intestinal epithelium. We studied the role of BAs and TGR5 inintestinal renewal, and regulation of ISC function in mice and intestinal organoids. We derived intestinal organoids from wild-type mice and Tgr5-/- mice, incubated them with BAs or the TGR5 agonist INT-777, and monitored ISC function by morphologic analyses and colony-forming assays. We disrupted Tgr5 specifically in Lgr5-positive ISCs in mice (Tgr5ISC-/- mice) and analyzed ISC number, proliferation, and differentiation by flow cytometry, immunofluorescence, and organoid assays. Tgr5ISC-/- mice were given cholecystokinin; we measured the effects of BA release into the intestinal lumen and on cell renewal. We induced colitis in Tgr5ISC-/- mice by administration of dextran sulfate sodium; disease severity was determined based on body weight, colon length, and histopathology analysis of colon biopsies. BAs and TGR5 agonists promoted growth of intestinal organoids. Administration of cholecystokinin to mice resulted in acute release of BAs into the intestinal lumen and increased proliferation of the intestinal epithelium. BAs and Tgr5 expression in ISCs were required for homeostatic intestinal epithelial renewal and fate specification, and for regeneration after colitis induction. Tgr5ISC-/- mice developed more severe colitis than mice without Tgr5 disruption in ISCs. ISCs incubated with INT-777 increased activation of yes-associated protein 1 (YAP1) andofits upstream regulator SRC. Inhibitors of YAP1 and SRC prevented organoid growth induced by TGR5 activation. BAs promote regeneration of the intestinal epithelium via activation of TGR5 in ISCs, resulting in activation of SRC and YAP and activation of their target genes.Release of endogenous BAs in the intestinal lumenissufficient to promote ISC renewal and drives regeneration in response to injury.