Intestinal Regeneration: Regulation by the Microenvironment

Bioengineering of Intestinal Grafts

Intestinal failure manifests as an impaired capacity of the intestine to sufficiently absorb vital nutrients and electrolytes essential for growth and well-being in pediatric and adult populations. Although parenteral nutrition remains the mainstay therapeutic approach, the pursuit of a definitive and curative strategy, such as regenerative medicine, is imperative. Substantial advancements in the field of engineered intestinal tissues present a promising avenue for addressing intestinal failure; nevertheless, extensive research is still necessary for effective translation from experimental benchwork to clinical bedside applications.

Microenvironment-sensitive nanozymes for tissue regeneration

Tissue defect is one of the significant challenges encountered in clinical practice. Nanomaterials, including nanoparticles, nanofibers, and metal-organic frameworks, have demonstrated an extensive potential in tissue regeneration, offering a promising avenue for future clinical applications. Nonetheless, the intricate landscape of the inflammatory tissue microenvironment has engendered challenges to the efficacy of nanomaterial-based therapies. This quandary has spurred researchers to pivot towards advanced nanotechnological remedies for overcoming these therapeutic constraints. Among these solutions, microenvironment-sensitive nanozymes have emerged as a compelling instrument with the capacity to reshape the tissue microenvironment and enhance the intricate process of tissue regeneration. In this review, we summarize the microenvironmental characteristics of damaged tissues, offer insights into the rationale guiding the design and engineering of microenvironment-sensitive nanozymes, and explore the underlying mechanisms that underpin these nanozymes' responsiveness. This analysis includes their roles in orchestrating cellular signaling, modulating immune responses, and promoting the delicate process of tissue remodeling. Furthermore, we discuss the diverse applications of microenvironment-sensitive nanozymes in tissue regeneration, including bone, soft tissue, and cartilage regeneration. Finally, we shed our sights on envisioning the forthcoming milestones in this field, prospecting a future where microenvironment-sensitive nanozymes contribute significantly to the development of tissue regeneration and improved clinical outcomes.

Aryl hydrocarbon receptor activity in intestinal epithelial cells in the formation of colonic tertiary lymphoid tissues

After birth, the development of secondary lymphoid tissues (SLTs) in the colon is dependent on the expression of the aryl hydrocarbon receptor (AhR) in immune cells as a response to the availability of AhR ligands. However, little is known about how AhR activity from intestinal epithelial cells (IECs) may influence the development of tertiary lymphoid tissues (TLTs). As organized structures that develop at sites of inflammation or infection during adulthood, TLTs serve as localized centers of adaptive immune responses, and their presence has been associated with the resolution of inflammation and tumorigenesis in the colon. Here, we investigated the effect of the conditional loss of AhR activity in IECs in the formation and immune cell composition of TLTs in a model of acute inflammation. In females, loss of AhR activity in IECs reduced the formation of TLTs without significantly changing disease outcomes or immune cell composition within TLTs. In males lacking AhR expression in IECs, increased disease activity index, lower expression of functional-IEC genes, increased number of TLTs, increased T-cell density, and lower B- to T-cell ratio were observed. These findings may represent an unfavorable prognosis when exposed to dextran sodium sulfate (DSS)-induced epithelial damage compared with females. Sex and loss of IEC AhR also resulted in changes in microbial populations in the gut. Collectively, these data suggest that the formation of TLTs in the colon is influenced by sex and AhR expression in IECs.NEW & NOTEWORTHY This is the first research of its kind to demonstrate a clear connection between biological sex and the development of tertiary lymphoid tissues (TLT) in the colon. In addition, the research finds that in a preclinical model of inflammatory bowel disease, the expression of the aryl hydrocarbon receptor (AhR) influences the development of these structures in a sex-specific manner.

Cell competition in primary and metastatic colorectal cancer

Adult tissues set the scene for a continuous battle between cells, where a comparison of cellular fitness results in the elimination of weaker "loser" cells. This phenomenon, named cell competition, is beneficial for tissue integrity and homeostasis. In fact, cell competition plays a crucial role in tumor suppression, through elimination of early malignant cells, as part of Epithelial Defense Against Cancer. However, it is increasingly apparent that cell competition doubles as a tumor-promoting mechanism. The comparative nature of cell competition means that mutational background, proliferation rate and polarity all factor in to determine the outcome of these processes. In this review, we explore the intricate and context-dependent involvement of cell competition in homeostasis and regeneration, as well as during initiation and progression of primary and metastasized colorectal cancer. We provide a comprehensive overview of molecular and cellular mechanisms governing cell competition and its parallels with regeneration.

Mechanisms of regeneration: to what extent do they recapitulate development?

One of the enduring debates in regeneration biology is the degree to which regeneration mirrors development. Recent technical advances, such as single-cell transcriptomics and the broad applicability of CRISPR systems, coupled with new model organisms in research, have led to the exploration of this longstanding concept from a broader perspective. In this Review, I outline the historical parallels between development and regeneration before focusing on recent research that highlights how dissecting the divergence between these processes can uncover previously unreported biological mechanisms. Finally, I discuss how these advances position regeneration as a more dynamic and variable process with expanded possibilities for morphogenesis compared with development. Collectively, these insights into mechanisms that orchestrate morphogenesis may reshape our understanding of the evolution of regeneration, reveal hidden biology activated by injury, and offer non-developmental strategies for restoring lost or damaged organs and tissues.

Discovery and Validation of Ferroptosis-Associated Genes of Ulcerative Colitis

Background

Ulcerative colitis (UC) is a long-lasting idiopathic condition, but its precise mechanisms remain unclear. Meanwhile, evidence has demonstrated that ferroptosis seems to interlock with the progress of UC. This research sought to identify hub genes of UC related to ferroptosis.

Methods

First, the relevant profiles for this article were obtained from GEO database. From the FerrDb, 479 genes linked to ferroptosis were retrieved. Using analysis of the difference and WGCNA on colonic samples from GSE73661, the remaining six hub genes linked to ferroptosis and UC were discovered. Through logistic regression analyses, the diagnostic model was constructed and was then evaluated by external validation using dataset GSE92415. Afterwards, the correlation between immune cell filtration in UC and hub genes was examined. Finally, a mice model of colitis was established, and the results were verified using qRT-PCR.

Results

We acquired six hub genes linked to ferroptosis and UC. In order to create a diagnostic model for UC, we used logistic regression analysis to screen three of the six ferroptosis related genes (HIF1A, SLC7A11, and LPIN1). The ROC curve showed that the three hub genes had outstanding potential for disease diagnosis (AUC = 0.976), which was subsequently validated in samples from GSE92415 (AUC = 0.962) and blood samples from GSE3365 (AUC = 0.847) and GSE94648 (AUC = 0.769). These genes might be crucial for UC immunity based upon the results on the immune system. Furthermore, mouse samples examined using qRT-PCR also verified our findings.

Conclusion

In conclusion, the findings have important implications for ferroptosis and UC, and these hub genes may also offer fresh perspectives on the aetiology and therapeutic approaches of UC.

Total ginsenosides extend healthspan of aging Drosophila by suppressing imbalances in intestinal stem cells and microbiota

BACKGROUND

Disruption of stem cell and microbial homeostasis accelerates the aging process. Hence, maintaining these balances effectively delays aging and alleviates the symptoms of age-related diseases. Recent research indicates that targeting endoplasmic reticulum (ER) stress and immune deficiency (IMD) signalling may play a positive role in maintaining homeostasis in aging intestinal stem cells (ISC) and microbial equilibrium. Previous research has suggested that total ginsenosides (TG) derived from Panax ginseng C. A. Meyer may exhibit potential anti-aging properties by mitigating ER stress and mediating the IMD pathway. Nevertheless, it remains unclear whether TG improve ISC and microbial homeostasis by modulating ER stress and the IMD pathway to promote healthy aging.

PURPOSE

To elucidate whether TG promotes healthspan in Drosophila and its underlying molecular mechanisms, focusing on its role in regulating ER stress and the IMD pathway to maintain ISC and intestinal microbiota homeostasis.

METHODS

High performance liquid chromatography was performed to detect the main saponin monomer in TG. Survival rate, gut length, barrier function, and feeding/excretion behaviour assays were used to evaluate the effects of TG on the lifespan and gut health of Drosophila. At the stem cell level, "esg-luciferase" reporter system, esg-GFP/delta stem cell fluorescent labelling, and phospho-histone H3+ mitotic activity assays were employed to determine whether TG prevented natural aging or oxidative stress-associated ISC over-proliferation in Drosophila. Immunofluorescence staining was used to detect the effects of TG on ER stress during aging. Overexpression or interference of ER stress target genes and their related c-Jun N-terminal kinase (JNK) gene was manipulated using gene editing technology to verify the molecular mechanism by which TG maintains age-related ISC proliferation homeostasis. Molecular docking and isothermal titration calorimetry were used to verify the direct interactions between TG and ER stress target genes. In addition, at the intestinal flora level, 16S rDNA sequencing was used to analyse the effect of TG on the diversity and abundance of Drosophila intestinal flora and the possible functional pathways involved. RT-qPCR was performed to determine whether TG mediated the expression of target genes in the IMD pathway. A dominant bacterial species-specific mono-association analysis were performed to verify whether the effects of TG on IMD target genes and ISC proliferation depended on the direct control of the dominant bacterial species.

RESULTS

Our results suggest that administration of TG delays the decline in gut morphology and function in aging Drosophila. TG prevents age-associated ISC hyperproliferation by inhibiting ER stress IRE1-mediated JNK signaling. Furthermore, oral TG prevented aging-associated ISC and gut microbiota dysbiosis by remodelling the gut microbiota and inhibiting Acetobacter-mediated activation of IMD target genes.

CONCLUSION

TG promotes healthy aging by inhibiting the excessive proliferation of ISC and alleviating intestinal microbial imbalance, thereby providing new insights for the research and development of anti-aging TG products.

Non-TGFβ profibrotic signaling in ulcerative colitis after in vivo experimental intestinal injury in humans

Although impaired regeneration is important in many gastrointestinal diseases including ulcerative colitis (UC), the dynamics of mucosal regeneration in humans are poorly investigated. We have developed a model to study these processes in vivo in humans. Epithelial restitution (ER) and extracellular matrix (ECM) regulation after an experimental injury of the sigmoid colonic mucosa was assessed by repeated high-resolution endoscopic imaging, histological assessment, RNA sequencing, deconvolution analysis, and 16S rDNA sequencing of the injury niche microbiome of 19 patients with UC in remission and 20 control subjects. Human ER had a 48-h lag before induction of regenerative epithelial cells [wound-associated epithelial (WAE) and transit amplifying (TA) cells] along with the increase of fibroblast-derived stem cell growth factor gremlin 1 mRNA (GREM1). However, UC deconvolution data showed rapid induction of inflammatory fibroblasts and upregulation of major structural ECM collagen mRNAs along with tissue inhibitor of metalloproteinase 1 (TIMP1), suggesting increased profibrotic ECM deposition. No change was seen in transforming growth factor β (TGFβ) mRNA, whereas the profibrotic cytokines interleukin 13 (IL13) and IL11 were upregulated in UC, suggesting that human postinjury responses could be TGFβ-independent. In conclusion, we found distinct regulatory layers of regeneration in the normal human colon and a potential targetable profibrotic dysregulation in UC that could lead to long-term end-organ failure, i.e., intestinal damage.NEW & NOTEWORTHY The study reveals the regulatory dynamics of epithelial regeneration and extracellular matrix remodeling after experimental injury of the human colon in vivo and shows that human intestinal regeneration is different from data obtained from animals. A lag phase in epithelial restitution is associated with induction of stromal cell-derived epithelial growth factors. Postinjury regeneration is transforming growth factor β-independent, and we find a profibrotic response in patients with ulcerative colitis despite being in remission.

Dark force rising: Reawakening and targeting of fetal-like stem cells in colorectal cancer

Stem cells play pivotal roles in maintaining intestinal homeostasis, orchestrating regeneration, and in key steps of colorectal cancer (CRC) initiation and progression. Intriguingly, adult stem cells are reduced during many of these processes. On the contrary, primitive fetal programs, commonly detected in development, emerge during tissue repair, CRC metastasis, and therapy resistance. Recent findings indicate a dynamic continuum between adult and fetal stem cell programs. We discuss critical mechanisms facilitating the plasticity between stem cell states and highlight the heterogeneity observed upon the appearance of fetal-like states. We focus on therapeutic opportunities that arise by targeting fetal-like CRC cells and how those concepts can be translated into the clinic.

Design principles and therapeutic applications of novel synthetic WNT signaling agonists

Wingless-related integration site or Wingless and Int-1 or Wingless-Int (WNT) signaling is crucial for embryonic development, and adult tissue homeostasis and regeneration, through its essential roles in cell fate, patterning, and stem cell regulation. The biophysical characteristics of WNT ligands have hindered efforts to interrogate ligand activity in vivo and prevented their development as therapeutics. Recent breakthroughs have enabled the generation of synthetic WNT signaling molecules that possess characteristics of natural ligands and potently activate the pathway, while also providing distinct advantages for therapeutic development and manufacturing. This review provides a detailed discussion of the protein engineering of these molecular platforms for WNT signaling agonism. We discuss the importance of WNT signaling in several organs and share insights from the initial application of these new classes of molecules in vitro and in vivo. These molecules offer a unique opportunity to enhance our understanding of how WNT signaling agonism promotes tissue repair, enabling targeted development of tailored therapeutics.

Development and characterization of Polycaprolactone/chitosan-based scaffolds for tissue engineering of various organs: A review

Research in creating 3D structures mirroring the extracellular matrix (ECM) with accurate environmental cues holds paramount significance in biological applications.Biomaterials that replicate ECM properties-mechanical, physicochemical, and biological-emerge as pivotal tools in mimicking ECM behavior.Incorporating synthetic and natural biomaterials is widely used to produce scaffolds suitable for the intended organs.Polycaprolactone (PCL), a synthetic biomaterial, boasts commendable mechanical properties, albeit with relatively modest biological attributes due to its hydrophobic nature.Chitosan (CTS) exhibits strong biological traits but lacks mechanical resilience for complex tissue regeneration.Notably, both PCL and CTS have demonstrated their application in tissue engineering for diverse types of tissues.Their combination across varying PCL:CTS ratios has increased the likelihood of fabricating scaffolds to address defects in sturdy and pliable tissues.This comprehensive analysis aspires to accentuate their distinct attributes within tissue engineering across different organs.The central focus resides in the role of PCL:CTS-based scaffolds, elucidating their contribution to the evolution of advanced functional 3D frameworks tailored for tissue engineering across diverse organs.Moreover, this discourse delves into the considerations pertinent to each organ.

Current understanding of the interplay between extracellular matrix remodelling and gut permeability in health and disease

The intestinal wall represents an interactive network regulated by the intestinal epithelium, extracellular matrix (ECM) and mesenchymal compartment. Under healthy physiological conditions, the epithelium undergoes constant renewal and forms an integral and selective barrier. Following damage, the healthy epithelium is restored via a series of signalling pathways that result in remodelling of the scaffolding tissue through finely-regulated proteolysis of the ECM by proteases such as matrix metalloproteinases (MMPs). However, chronic inflammation of the gastrointestinal tract, as occurs in Inflammatory Bowel Disease (IBD), is associated with prolonged disruption of the epithelial barrier and persistent damage to the intestinal mucosa. Increased barrier permeability exhibits distinctive signatures of inflammatory, immunological and ECM components, accompanied by increased ECM proteolytic activity. This narrative review aims to bring together the current knowledge of the interplay between gut barrier, immune and ECM features in health and disease, discussing the role of barrier permeability as a discriminant between homoeostasis and IBD.

Tryptophan metabolites relieve intestinal Candida albicans infection by altering the gut microbiota to reduce IL-22 release from group 3 innate lymphoid cells of the colon lamina propria

Invasive candidiasis may be caused by Candida albicans (C. albicans) colonization of the intestinal tract. Preventing intestinal damage caused by Candida albicans infection and protecting intestinal barrier function have become a critical issue. Integrated analyses of the microbiome with metabolome revealed a remarkable shift of the gut microbiota and tryptophan metabolites, kynurenic acid (KynA), and indolacrylic acid (IA) in mice infected with C. albicans. The transcriptome sequencing indicated that differentially expressed genes were significantly associated with innate immune responses and inflammatory responses. The results of this study suggest that KynA and IA (KI) can alleviate intestinal damage caused by Candida albicans infection in mice by reducing intestinal permeability, increasing intestinal firmness, alleviating intestinal inflammation, and reducing the secretion of interleukin-22 (IL-22) in the 3 groups of colon innate lymphoid cells (ILC3). We performed a fecal microbiota transplantation (FMT) experiment and found that the intestinal barrier function, inflammation, and IL-22 secretion of ILC3 in the colon lamina propria of the recipient mice subjected to C. albicans infection and KI treatment were consistent with the trends of the donor mice. Our results suggest that tryptophan metabolites may directly regulate colon lamina ILC3 to promote intestinal resistance to C. albicans invasion, or indirectly regulate the ILC3 secretion of IL-22 to play a protective role in the intestinal barrier by affecting intestinal microorganisms, which may become a potential target for alleviating intestine borne C. albicans infection.

Mulberry Leaf-Derived Morin Activates β-Catenin by Binding to Frizzled7 to Promote Intestinal Stem Cell Expansion upon Heat-Stable Enterotoxin b Injury

Intestinal stem cells (ISCs) sustain epithelial renewal by dynamically altering behaviors of proliferation and differentiation in response to various nutrition and stress inputs. However, how ISCs integrate bioactive substance morin cues to protect against heat-stable enterotoxin b (STb) produced by Escherichia coli remains an uncertain question with implications for treating bacterial diarrhea. Our recent work showed that oral mulberry leaf-derived morin improved the growth performance in STb-challenged mice. Furthermore, morin supplementation reinstated the impaired small-intestinal epithelial structure and barrier function by stimulating ISC proliferation and differentiation as well as supporting intestinal organoid expansion ex vivo. Importantly, the Wnt/β-catenin pathway, an ISC fate commitment signal, was reactivated by morin to restore the jejunal crypt-villus architecture in response to STb stimulation. Mechanically, the extracellular morin-initiated β-catenin axis is dependent or partially dependent on the Wnt membrane receptor Frizzled7 (FZD7). Our data reveal an unexpected role of leaf-derived morin, which represents molecular signaling targeting the FZD7 platform instrumental for controlling ISC regeneration upon STb injury.

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

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

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

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

SIRT4 loss reprograms intestinal nucleotide metabolism to support proliferation following perturbation of homeostasis

The intestine is a highly metabolic tissue, but the metabolic programs that influence intestinal crypt proliferation, differentiation, and regeneration are still emerging. Here, we investigate how mitochondrial sirtuin 4 (SIRT4) affects intestinal homeostasis. Intestinal SIRT4 loss promotes cell proliferation in the intestine following ionizing radiation (IR). SIRT4 functions as a tumor suppressor in a mouse model of intestinal cancer, and SIRT4 loss drives dysregulated glutamine and nucleotide metabolism in intestinal adenomas. Intestinal organoids lacking SIRT4 display increased proliferation after IR stress, along with increased glutamine uptake and a shift toward de novo nucleotide biosynthesis over salvage pathways. Inhibition of de novo nucleotide biosynthesis diminishes the growth advantage of SIRT4-deficient organoids after IR stress. This work establishes SIRT4 as a modulator of intestinal metabolism and homeostasis in the setting of DNA-damaging stress.

Discovery and Optimization of Novel Nonbile Acid FXR Agonists as Preclinical Candidates for the Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a multifactorial chronic inflammation of the intestine and has become a global public health concern. A farnesoid X receptor (FXR) was recently reported to play a key role in hepatic-intestinal circulation, intestinal metabolism, immunity, and microbial regulation, and thus, it becomes a promising therapeutic target for IBD. In this study, we identified a series of nonbile acid FXR agonists, in which 33 novel compounds were designed and synthesized by the structure-based drug design strategy from our previously identified hit compound. Compound 33 exhibited a potent FXR agonistic activity, high intestinal distribution, good anti-inflammatory activity, and the ability to repair the colon epithelium in a DSS-induced acute enteritis model. Based on the results of RNA-seq analysis, we further investigated the therapeutic potential of the combination of compound 33 with 5-ASA. Overall, the results indicated that compound 33 is a promising drug candidate for IBD treatment.

NIBR-LTSi is a selective LATS kinase inhibitor activating YAP signaling and expanding tissue stem cells in vitro and in vivo

The YAP/Hippo pathway is an organ growth and size regulation rheostat safeguarding multiple tissue stem cell compartments. LATS kinases phosphorylate and thereby inactivate YAP, thus representing a potential direct drug target for promoting tissue regeneration. Here, we report the identification and characterization of the selective small-molecule LATS kinase inhibitor NIBR-LTSi. NIBR-LTSi activates YAP signaling, shows good oral bioavailability, and expands organoids derived from several mouse and human tissues. In tissue stem cells, NIBR-LTSi promotes proliferation, maintains stemness, and blocks differentiation in vitro and in vivo. NIBR-LTSi accelerates liver regeneration following extended hepatectomy in mice. However, increased proliferation and cell dedifferentiation in multiple organs prevent prolonged systemic LATS inhibition, thus limiting potential therapeutic benefit. Together, we report a selective LATS kinase inhibitor agonizing YAP signaling and promoting tissue regeneration in vitro and in vivo, enabling future research on the regenerative potential of the YAP/Hippo pathway.

LINC MIR503HG Controls SC-β Cell Differentiation and Insulin Production by Targeting CDH1 and HES1

Stem cell-derived pancreatic progenitors (SC-PPs), as an unlimited source of SC-derived β (SC-β) cells, offers a robust tool for diabetes treatment in stem cell-based transplantation, disease modeling, and drug screening. Whereas, PDX1+/NKX6.1+ PPs enhances the subsequent endocrine lineage specification and gives rise to glucose-responsive SC-β cells in vivo and in vitro. To identify the regulators that promote induction efficiency and cellular function maturation, single-cell RNA-sequencing is performed to decipher the transcriptional landscape during PPs differentiation. The comprehensive evaluation of functionality demonstrated that manipulating LINC MIR503HG using CRISPR in PP cell fate decision can improve insulin synthesis and secretion in mature SC-β cells, without effects on liver lineage specification. Importantly, transplantation of MIR503HG-/- SC-β cells in recipients significantly restored blood glucose homeostasis, accompanied by serum C-peptide release and an increase in body weight. Mechanistically, by releasing CtBP1 occupying the CDH1 and HES1 promoters, the decrease in MIR503HG expression levels provided an excellent extracellular niche and appropriate Notch signaling activation for PPs following differentiation. Furthermore, this exhibited higher crucial transcription factors and mature epithelial markers in CDH1High expressed clusters. Altogether, these findings highlighted MIR503HG as an essential and exclusive PP cell fate specification regulator with promising therapeutic potential for patients with diabetes.

Reversible Host-Guest Crosslinks in Supramolecular Hydrogels for On-Demand Mechanical Stimulation of Human Mesenchymal Stem Cells

Stem cells are regulated not only by biochemical signals but also by biophysical properties of extracellular matrix (ECM). The ECM is constantly monitored and remodeled because the fate of stem cells can be misdirected when the mechanical interaction between cells and ECM is imbalanced. A well-defined ECM model for bone marrow-derived human mesenchymal stem cells (hMSCs) based on supramolecular hydrogels containing reversible host-guest crosslinks is fabricated. The stiffness (Young's modulus E) of the hydrogels can be switched reversibly by altering the concentration of non-cytotoxic, free guest molecules dissolved in the culture medium. Fine-adjustment of substrate stiffness enables the authors to determine the critical stiffness level E* at which hMSCs turn the mechano-sensory machinery on or off. Next, the substrate stiffness across E* is switched and the dynamic adaptation characteristics such as morphology, traction force, and YAP/TAZ signaling of hMSCs are monitored. These data demonstrate the instantaneous switching of traction force, which is followed by YAP/TAZ signaling and morphological adaptation. Periodical switching of the substrate stiffness across E* proves that frequent applications of mechanical stimuli drastically suppress hMSC proliferation. Mechanical stimulation across E* level using dynamic hydrogels is a promising strategy for the on-demand control of hMSC transcription and proliferation.

Telocytes in the Luminal GI Tract

Telocytes are unique mesenchymal cells characterized by multiple remarkably long cytoplasmic extensions that extend hundreds of micron away from the cell body. Through these extensions, telocytes establish a 3-dimensional network by connecting with other telocytes and various cell types within the tissue. In the intestine, telocytes have emerged as an essential component of the stem cell niche, providing Wnt proteins that are critical for the proliferation of stem and progenitor cells. However, the analysis of single-cell RNA sequencing has revealed other stromal populations and mechanisms for niche organization, raising questions about the role of telocytes as a component of the stem cell niche. This review explores the current state-of-the-art, existing controversies, and potential future directions related to telocytes in the luminal gastrointestinal tract.

Host-microbiota interaction in intestinal stem cell homeostasis

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

Evidence of interactions among apoptosis, cell proliferation, and dedifferentiation in the rudiment during whole-organ intestinal regeneration in the sea cucumber

Sea cucumbers have an extraordinary regenerative capability. Under stressful conditions, Holothuria glaberrima can eviscerate their internal organs, including the digestive tract. From the mesentery, a rudiment grows and gives rise to a new intestine within a few weeks. In the last decades, the cellular events that occur during intestinal regeneration have been characterized, including apoptosis, cell proliferation, and muscle cell dedifferentiation. Nevertheless, their contribution to the formation and early growth of the rudiment is still unknown. Furthermore, these cellular events' relationship and potential interdependence remain a mystery. Using modulators to inhibit apoptosis and cell proliferation, we tested whether rudiment growth or other regenerative cellular events like muscle cell dedifferentiation were affected. We found that inhibition of apoptosis by zVAD and cell proliferation by aphidicolin and mitomycin did not affect the overall size of the rudiment seven days post-evisceration (7-dpe). Interestingly, animals treated with aphidicolin showed higher levels of muscle cell dedifferentiation in the distal mesentery, which could act as a compensatory mechanism. On the other hand, inhibition of apoptosis led to a decrease in cell proliferation in the rudiment and a delay in the spatiotemporal progression of muscle cell dedifferentiation throughout the rudiment-mesentery structure. Our findings suggest that neither apoptosis nor cell proliferation significantly contributes to early rudiment growth during intestinal regeneration in the sea cucumber. Nevertheless, apoptosis may play an essential role in modulating cell proliferation in the rudiment (a process known as apoptosis-induced proliferation) and the timing for the progression of muscle cell dedifferentiation. These findings provide new insights into the role and relationship of cellular events during intestinal regeneration in an emerging regeneration model.

Homeostasis, injury, and recovery dynamics at multiple scales in a self-organizing mouse intestinal crypt

The maintenance of the functional integrity of the intestinal epithelium requires a tight coordination between cell production, migration, and shedding along the crypt-villus axis. Dysregulation of these processes may result in loss of the intestinal barrier and disease. With the aim of generating a more complete and integrated understanding of how the epithelium maintains homeostasis and recovers after injury, we have built a multi-scale agent-based model (ABM) of the mouse intestinal epithelium. We demonstrate that stable, self-organizing behaviour in the crypt emerges from the dynamic interaction of multiple signalling pathways, such as Wnt, Notch, BMP, ZNRF3/RNF43, and YAP-Hippo pathways, which regulate proliferation and differentiation, respond to environmental mechanical cues, form feedback mechanisms, and modulate the dynamics of the cell cycle protein network. The model recapitulates the crypt phenotype reported after persistent stem cell ablation and after the inhibition of the CDK1 cycle protein. Moreover, we simulated 5-fluorouracil (5-FU)-induced toxicity at multiple scales starting from DNA and RNA damage, which disrupts the cell cycle, cell signalling, proliferation, differentiation, and migration and leads to loss of barrier integrity. During recovery, our in silico crypt regenerates its structure in a self-organizing, dynamic fashion driven by dedifferentiation and enhanced by negative feedback loops. Thus, the model enables the simulation of xenobiotic-, in particular chemotherapy-, induced mechanisms of intestinal toxicity and epithelial recovery. Overall, we present a systems model able to simulate the disruption of molecular events and its impact across multiple levels of epithelial organization and demonstrate its application to epithelial research and drug development.

Decellularized small intestine scaffolds: a potential xenograft for restoration of intestinal perforation

Small intestine perforation is a serious medical condition that requires immediate medical attention. The traditional course of treatment entails resection followed by anastomosis; however, it has complications such as small bowel syndrome (SBS), anastomotic leakage, and fistula formation. Here, a novel strategy is demonstrated, that utilizes the xenogeneic, decellularized goat small intestine as a patch for small intestine regeneration in cases of intestinal perforation. The goat small intestine scaffold underwent sodium dodecyl sulfate decellularization, which revealed consistent, quick, and effective decellularization. Decellularization contributed the least amount of extracellular matrix degradation while maintaining the intestinal architecture. By implanting the decellularized goat small intestine scaffolds (DGSIS) on the chorioallantoic membrane (CAM), no discernible loss of angiogenesis was seen in the CAM region, and this enabled the DGSIS to be evaluated for biocompatibility in ovo. The DGSIS was then xeno-transplanted as a patch on a small intestine perforation rat model. After 30 days post transplant, barium salt used as contrast gastrointestinal X-ray imaging revealed no leakage or obstruction in the small intestine. Histology, scanning electron microscopy, and immunohistochemistry assisted in analyzing the engraftment of host cells into the xeno patch. The xeno-patch expressed high levels of E-cadherin, α-smooth muscle actin (α-SMA), Occludin, Zonnula occluden (ZO-1), Ki 67, and Na+/K+-ATPase. The xeno-patch was consequently recellularized and incorporated into the host without causing an inflammatory reaction. As an outcome, decellularized goat small intestine was employed as a xenograft and could be suitable for regeneration of the perforated small intestine.

MicroRNA-200 Loaded Lipid Nanoparticles Promote Intestinal Epithelium Regeneration in Canonical MicroRNA-Deficient Mice

Intestinal epithelium undergoes regeneration after injuries, and the disruption of this process can lead to inflammatory bowel disease and tumorigenesis. Intestinal stem cells (ISCs) residing in the crypts are crucial for maintaining the intestinal epithelium's homeostasis and promoting regeneration upon injury. However, the precise role of DGCR8, a critical component in microRNA (miRNA) biogenesis, in intestinal regeneration remains poorly understood. In this study, we provide compelling evidence demonstrating the indispensable role of epithelial miRNAs in the regeneration of the intestine in mice subjected to 5-FU or irradiation-induced injury. Through a comprehensive pooled screen of miRNA function in Dgcr8-deficient organoids, we observe that the loss of the miR-200 family leads to the hyperactivation of the p53 pathway, thereby reducing ISCs and impairing epithelial regeneration. Notably, downregulation of the miR-200 family and hyperactivation of the p53 pathway are verified in colonic tissues from patients with active ulcerative colitis (UC). Most importantly, the transient supply of miR-200 through the oral delivery of lipid nanoparticles (LNPs) carrying miR-200 restores ISCs and promotes intestinal regeneration in mice following acute injury. Our study implies the miR-200/p53 pathway as a promising therapeutic target for active UC patients with diminished levels of the miR-200 family. Furthermore, our findings suggest that the clinical application of LNP-miRNAs could enhance the efficacy, safety, and acceptability of existing therapeutic modalities for intestinal diseases.

Similar proteome expression profiles of the aggregated lymphoid nodules area and Peyer's patches in Bactrian camel

BACKGROUND

The presence of Aggregated Lymphoid Nodules Area (ALNA) is a notable anatomical characteristic observed in the abomasum of Bactrian camels. This area is comprised of two separate regions, namely the Reticular Mucosal Folds Region (RMFR) and the Longitudinal Mucosal Folds Region (LMFR). The histological properties of ALNA exhibit significant similarities to those of Peyer's patches (PPs) found in the gastrointestinal system. The functional characteristics of ALNA were examined in relation to mucosal immunity in the gastrointestinal system.

RESULTS

We used iTRAQ-based proteomic analysis on twelve Bactrian camels to measure the amount of proteins expressed in ALNA. In the experiment, we sampled the RMFR and LMFR separately from the ALNA and compared their proteomic quantification results with samples from the PPs. A total of 1253 proteins were identified, among which 39 differentially expressed proteins (DEPs) were found between RMFR and PPs, 33 DEPs were found between LMFR and PPs, and 22 DEPs were found between LMFR and RMFR. The proteins FLNA, MYH11, and HSPB1 were chosen for validation using the enzyme-linked immunosorbent assay (ELISA), and the observed expression profiles were found to be in agreement with the results obtained from the iTRAQ study. The InnateDB database was utilized to get data pertaining to immune-associated proteins in ALNA. It was observed that a significant proportion, specifically 76.6%, of these proteins were found to be associated with the same orthogroups as human immune-related genes. These proteins are acknowledged to be associated with a diverse range of functions, encompassing the uptake, processing and presentation of antigens, activation of lymphocytes, the signaling pathways of T-cell and B-cell receptors, and the control of actin polymerization.

CONCLUSIONS

The experimental results suggest that there are parallels in the immune-related proteins found in ALNA and PPs. Although there are variations in the structures of LMFR and RMFR, the proteins produced in both structures exhibit a high degree of similarity and perform comparable functions in the context of mucosal immune responses.

Krüppel-like factor 5 activates chick intestinal stem cell and promotes mucosal repair after impairment

The mucosal renewal, which depends on the intestinal stem cell (ISC) activity, is the foundation of mucosal repairment. Importantly, activation of reserve ISCs (rISCs) plays a vital role in initiating mucosal repair after injury. However, the underlying regulatory mechanism of rISCs activation in chickens remains unclear. In this study, immediately after lipopolysaccharide (LPS) challenge, mitochondrial morphological destruction and dysfunction appeared in the crypt, accompanied by decreased epithelial secretion (decreased Muc2 mRNA abundance and LYSOZYME protein level). However, immediately after mucosal injury, the mucosal renewal accelerated, as indicated by the increased BrdU positive rate, proliferating cell nuclear antigen (PCNA) protein level and mRNA abundance of cell cycle markers (Ccnd1, Cdk2). Concerning the ISCs activity, during the early period of injury, there appeared a reduction of active ISCs (aISCs) marker Lgr5 mRNA and protein, and an increasing of rISCs marker Hopx mRNA and protein. Strikingly, upon LPS challenge, increased mRNA transcriptional level of Krüppel-like factor 5 (Klf5) was detected in the crypt. Moreover, under LPS treatment in organoids, the KLF5 inhibitor (ML264) would decrease the mRNA and protein levels of Stat5a and Hopx, the STAT5A inhibitor (AC-4-130) would suppress the Lgr5 mRNA and protein levels. Furthermore, the Dual-Luciferase Reporter assay confirmed that, KLF5 would bind to Hopx promoter and activate the rISCs, STAT5A would trigger Lgr5 promoter and activate the aISCs. Collectively, KLF5 was upregulated during the early period of injury, further activate the rISCs directly and activate aISCs via STAT5A indirectly, thus initiate mucosal repair after injury.

Advanced Progression for the Heterogeneity and Homeostasis of Intestinal Stem Cells

Current understanding of the leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) in intestinal stem cells (ISCs) is well established, however, the implications of ISC heterogeneity and homeostasis are poorly understood. Prior studies have provided important evidence for the association between heterogeneity of ISC pools with pathogenesis and therapeutic response of malignant disease. Leveraging the advantages of organoids and single cell RNA sequencing (scRNA-seq), glandular development has been simulated and cell heterogeneity has been clarified. Based on this research, several potential ISCs were identified, such as LGR5 + p27 + quiescent ISCs, LGR5 + Mex3a + slowly proliferating stem cells, and CLU + reverse stem cells. We also illustrated major factors responsible for ISC homeostasis including metabolism-related (LKB1, TGR5, HMGCS2), inflammation-related (IFB-b, IFN2, TNF), and Wnt signaling-related (CREPT, Mex3a, MTG16) factors. ISCs play complex roles in intestinal tumorigenesis, chemoresistance and occasional relapse of colon cancer, which bear discussion. In this review, we focus on novel technical challenges in ISCs fate drawing upon recent research with the goals of clarifying our understanding of complex ISCs, elucidating the integrated intestinal crypt niche, and creating new opportunities for therapeutic development.

Nutrient-driven dedifferentiation of enteroendocrine cells promotes adaptive intestinal growth in Drosophila

Post-developmental organ resizing improves organismal fitness under constantly changing nutrient environments. Although stem cell abundance is a fundamental determinant of adaptive resizing, our understanding of its underlying mechanisms remains primarily limited to the regulation of stem cell division. Here, we demonstrate that nutrient fluctuation induces dedifferentiation in the Drosophila adult midgut to drive adaptive intestinal growth. From lineage tracing and single-cell RNA sequencing, we identify a subpopulation of enteroendocrine (EE) cells that convert into functional intestinal stem cells (ISCs) in response to dietary glucose and amino acids by activating the JAK-STAT pathway. Genetic ablation of EE-derived ISCs severely impairs ISC expansion and midgut growth despite the retention of resident ISCs, and in silico modeling further indicates that EE dedifferentiation enables an efficient increase in the midgut cell number while maintaining epithelial cell composition. Our findings identify a physiologically induced dedifferentiation that ensures ISC expansion during adaptive organ growth in concert with nutrient conditions.

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 β-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.

The cyclooxygenase-expressing mesenchyme resists intestinal epithelial injury by paracrine signaling

Paracrine signals play pivotal roles in organ homeostasis. Mesenchymal stromal cells (MSCs) play a key role in regulating epithelium homeostasis in the intestine while their paracrine effects are poorly characterized. Here, we identified prostaglandin E2 (PGE2) secreted by cyclooxygenase (COX)-expressing MSCs as a vital factor to maintain the intestinal mucosal barrier. We found that MSCs-induced organoid swelling through paracrine effect in vitro, a process due to enhanced water adsorption and is mediated by the COX-PGE2-EP4 axis. To further explore the regulatory effect of this axis on the intestinal epithelial barrier in vivo, we established the conditional knockout mouse model to specifically delete COX in MSCs and found that PGE2 reduction downregulated the gene Muc2 and induced a gastric metaplasia-like phenotype. Moreover, PGE2 defects increased the susceptibility of intestinal epithelium to colitis. Our study uncovers the paracrine signaling of COX-expressing MSCs in intestinal mucosal barrier maintenance, providing a basis for understanding the role of mesenchymal cells in the pathophysiological function of the intestine.

Fetal Muse-based therapy prevents lethal radio-induced gastrointestinal syndrome by intestinal regeneration

BACKGROUND

Human multilineage-differentiating stress enduring (Muse) cells are nontumorigenic endogenous pluripotent-like stem cells that can be easily obtained from various adult or fetal tissues. Regenerative effects of Muse cells have been shown in some disease models. Muse cells specifically home in damaged tissues where they exert pleiotropic effects. Exposition of the small intestine to high doses of irradiation (IR) delivered after radiotherapy or nuclear accident results in a lethal gastrointestinal syndrome (GIS) characterized by acute loss of intestinal stem cells, impaired epithelial regeneration and subsequent loss of the mucosal barrier resulting in sepsis and death. To date, there is no effective medical treatment for GIS. Here, we investigate whether Muse cells can prevent lethal GIS and study how they act on intestinal stem cell microenvironment to promote intestinal regeneration.

METHODS

Human Muse cells from Wharton's jelly matrix of umbilical cord (WJ-Muse) were sorted by flow cytometry using the SSEA-3 marker, characterized and compared to bone-marrow derived Muse cells (BM-Muse). Under gas anesthesia, GIS mice were treated or not through an intravenous retro-orbital injection of 50,000 WJ-Muse, freshly isolated or cryopreserved, shortly after an 18 Gy-abdominal IR. No immunosuppressant was delivered to the mice. Mice were euthanized either 24 h post-IR to assess early small intestine tissue response, or 7 days post-IR to assess any regenerative response. Mouse survival, histological stainings, apoptosis and cell proliferation were studied and measurement of cytokines, recruitment of immune cells and barrier functional assay were performed.

RESULTS

Injection of WJ-Muse shortly after abdominal IR highly improved mouse survival as a result of a rapid regeneration of intestinal epithelium with the rescue of the impaired epithelial barrier. In small intestine of Muse-treated mice, an early enhanced secretion of IL-6 and MCP-1 cytokines was observed associated with (1) recruitment of monocytes/M2-like macrophages and (2) proliferation of Paneth cells through activation of the IL-6/Stat3 pathway.

CONCLUSION

Our findings indicate that a single injection of a small quantity of WJ-Muse may be a new and easy therapeutic strategy for treating lethal GIS.

Mesenchymal Stem Cell-Derived Exosomes are Effective for Radiation Enteritis and Essential for the Proliferation and Differentiation of Lgr5+ Intestinal Epithelial Stem Cells by Regulating Mir-195/Akt/β-Catenin Pathway

BACKGROUND

Radiation enteritis (RE) is a common complication of abdominal or pelvic radiotherapy, which when severe, could be life-threatening. Currently, there are no effective treatments. Studies have shown that mesenchymal stem cells (MSCs)-derived exosomes (MSC-exos) exhibit promising therapeutic effects in inflammatory diseases. However, the specific role of MSC-exos in RE and the regulatory mechanisms remain elusive.

METHODS

In vivo assay was carried out by injecting MSC-exos into the total abdominal irradiation (TAI)-induced RE mouse model. For in vitro assay, Lgr5-positive intestinal epithelial stem cells (Lgr5+ IESC) were extracted from mice, followed by irradiation along with MSC-exos treatment. HE staining was performed to measure histopathological changes. mRNA expression of inflammatory factors TNF-α and IL-6 and stem cell markers LGR5, and OCT4 were quantified by RT-qPCR. EdU and TUNEL staining was performed to estimate cell proliferation and apoptosis. MiR-195 expression in TAI mice and radiation-induced Lgr5+ IESC was tested.

RESULTS

We found that the injection of MSC-exos inhibited inflammatory reaction, increased stem cell marker expression, and maintained intestinal epithelial integrity in TAI mice. Furthermore, MSC-exos treatment increased the proliferation and simultaneously suppressed apoptosis in radiation-stimulated Lgr5+ IESC. MiR-195 expression increased by radiation exposure was decreased by MSC-exos therapy. MiR-195 overexpression facilitated the progress of RE by counteracting the effect of MSC-exos. Mechanistically, the Akt and Wnt/β-catenin pathways inhibited by MSC-exos were activated by miR-195 upregulation.

CONCLUSION

MSC-Exos are effective in treating RE and are essential for the proliferation and differentiation of Lgr5+ IESCs. Moreover, MSC-exos mediates its function by regulating miR-195 Akt β-catenin pathways.

Sonic Hedgehog and WNT Signaling Regulate a Positive Feedback Loop Between Intestinal Epithelial and Stromal Cells to Promote Epithelial Regeneration

BACKGROUND AND AIMS

Active intestinal stem cells are prone to injury by ionizing radiation. We previously showed that upon radiation-induced injury, normally quiescent reserve intestinal stem cells (rISCs) (marked by BMI1) are activated by Musashi-1 (MSI1) and exit from the quiescent state to regenerate the intestinal epithelium. This study aims to further establish the mechanism that regulates activation of Bmi1-CreER;Rosa26eYFP (Bmi1-CreER) rISCs following γ radiation-induced injury.

METHODS

Bmi1-CreER mice were treated with tamoxifen to initiate lineage tracing of BMI1 (eYFP+) cells and exposed to 12 Gy of total body γ irradiation or sham. Intestinal tissues were collected and analyzed by immunofluorescence, Western blot, reverse-transcription quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and chromatin immunoprecipitation real-time polymerase chain reaction.

RESULTS

After irradiation, increased expression of Msi1 in eYFP+ cells was accompanied by increased expression of Axin2, a WNT marker. Promoter studies of the Msi1 gene indicated that Msi1 is a WNT target gene. Coculture of stromal cells isolated from irradiated mice stimulated Bmi1-CreER-derived organoid regeneration more effectively than those from sham mice. Expression of WNT ligands, including Wnt2b, Wnt4, Wnt5a, and Rspo3, was increased in irradiated stromal cells compared with sham-treated stromal cells. Moreover, expression of the Sonic hedgehog (SHH) effector Gli1 was increased in stromal cells from irradiated mice. This was correlated with an increased expression of SHH in epithelial cells postirradiation, indicating epithelial-stromal interaction. Finally, preinjury treatment with SHH inhibitor cyclopamine significantly reduced intestinal epithelial regeneration and Msi1 expression postirradiation.

CONCLUSIONS

Upon ionizing radiation-induced injury, intestinal epithelial cells increase SHH secretion, stimulating stromal cells to secrete WNT ligands. WNT activators induce Msi1 expression in the Bmi1-CreER cells. This stromal-epithelial interaction leads to Bmi1-CreER rISCs induction and epithelial regeneration.

Endothelial FOXC1 and FOXC2 promote intestinal regeneration after ischemia-reperfusion injury

Intestinal ischemia underlies several clinical conditions and can result in the loss of the intestinal mucosal barrier. Ischemia-induced damage to the intestinal epithelium is repaired by stimulation of intestinal stem cells (ISCs), and paracrine signaling from the vascular niche regulates intestinal regeneration. Here, we identify FOXC1 and FOXC2 as essential regulators of paracrine signaling in intestinal regeneration after ischemia-reperfusion (I/R) injury. Vascular endothelial cell (EC)- and lymphatic EC (LEC)-specific deletions of Foxc1, Foxc2, or both in mice worsen I/R-induced intestinal damage by causing defects in vascular regrowth, expression of chemokine CXCL12 and Wnt activator R-spondin 3 (RSPO3) in blood ECs (BECs) and LECs, respectively, and activation of Wnt signaling in ISCs. Both FOXC1 and FOXC2 directly bind to regulatory elements of the CXCL12 and RSPO3 loci in BECs and LECs, respectively. Treatment with CXCL12 and RSPO3 rescues the I/R-induced intestinal damage in EC- and LEC-Foxc mutant mice, respectively. This study provides evidence that FOXC1 and FOXC2 are required for intestinal regeneration by stimulating paracrine CXCL12 and Wnt signaling.

Extensive jejunal injury is repaired by migration and transdifferentiation of ileal enterocytes in zebrafish

A major cause of intestinal failure (IF) is intestinal epithelium necrosis and massive loss of enterocytes, especially in the jejunum, the major intestinal segment in charge of nutrient absorption. However, mechanisms underlying jejunal epithelial regeneration after extensive loss of enterocytes remain elusive. Here, we apply a genetic ablation system to induce extensive damage to jejunal enterocytes in zebrafish, mimicking the jejunal epithelium necrosis that causes IF. In response to injury, proliferation and filopodia/lamellipodia drive anterior migration of the ileal enterocytes into the injured jejunum. The migrated fabp6⁺ ileal enterocytes transdifferentiate into fabp2⁺ jejunal enterocytes to fulfill the regeneration, consisting of dedifferentiation to precursor status followed by redifferentiation. The dedifferentiation is activated by the IL1β-NFκB axis, whose agonist promotes regeneration. Extensive jejunal epithelial damage is repaired by the migration and transdifferentiation of ileal enterocytes, revealing an intersegmental migration mechanism of intestinal regeneration and providing potential therapeutic targets for IF caused by jejunal epithelium necrosis.

Integrative analysis reveals marker genes for intestinal mucosa barrier repairing in clinical patients

This study aims to identify biomarkers of intestinal repair and provide potential therapeutic clues for improving functional recovery and prognostic performance after intestinal inflammation or injury. Here, we conducted a large-scale screening of multiple transcriptomic and scRNA-seq datasets of patients with inflammatory bowel disease (IBD), and identified 10 marker genes that potentially contribute to intestinal barrier repairing: AQP8, SULT1A1, HSD17B2, PADI2, SLC26A2, SELENBP1, FAM162A, TNNC2, ACADS, and TST. Analysis of a published scRNA-seq dataset revealed that expression of these healing markers were specific to absorptive cell types in intestinal epithelium. Furthermore, we conducted a clinical study where 11 patients underwent ileum resection demonstrating that upregulation of post-operative AQP8 and SULT1A1 expression were associated with improved recovery of bowel functions after surgery-induced intestinal injury, making them confident biomarkers of intestinal healing as well as potential prognostic markers and therapeutic targets for patients with impaired intestinal barrier functions.

Modulation of stem cell fate in intestinal homeostasis, injury and repair

The mammalian intestinal epithelium constitutes the largest barrier against the external environment and makes flexible responses to various types of stimuli. Epithelial cells are fast-renewed to counteract constant damage and disrupted barrier function to maintain their integrity. The homeostatic repair and regeneration of the intestinal epithelium are governed by the Lgr5⁺ intestinal stem cells (ISCs) located at the base of crypts, which fuel rapid renewal and give rise to the different epithelial cell types. Protracted biological and physicochemical stress may challenge epithelial integrity and the function of ISCs. The field of ISCs is thus of interest for complete mucosal healing, given its relevance to diseases of intestinal injury and inflammation such as inflammatory bowel diseases. Here, we review the current understanding of the signals and mechanisms that control homeostasis and regeneration of the intestinal epithelium. We focus on recent insights into the intrinsic and extrinsic elements involved in the process of intestinal homeostasis, injury, and repair, which fine-tune the balance between self-renewal and cell fate specification in ISCs. Deciphering the regulatory machinery that modulates stem cell fate would aid in the development of novel therapeutics that facilitate mucosal healing and restore epithelial barrier function.

HucMSC-Exo Promote Mucosal Healing in Experimental Colitis by Accelerating Intestinal Stem Cells and Epithelium Regeneration via Wnt Signaling Pathway

Background

Mucosal healing has emerged as a crucial therapeutic goal for inflammatory bowel diseases (IBD). Exosomes (Exo) as a potential acellular candidate for stem cell therapy might be competent to promote mucosal healing, while its mechanism remains unexplored.

Methods

Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSCs) were subjected to experimental colitis mice intraperitoneally to estimate the role in mucosal healing and the regeneration of intestinal stem cells (ISCs) and epithelium. The intestinal organoid model of IBD was constructed utilizing tumor necrosis factor (TNF)-α for subsequent function analysis in vitro. Transcriptome sequencing was performed to decipher the underlying mechanism and Wnt-C59, an oral Wnt inhibitor, was used to confirm that further. Finally, the potential specific components of hucMSC‑exo were investigated based on several existing miRNA expression datasets.

Results

HucMSC-exo showed striking potential for mucosal healing in colitis mice, characterized by decreased histopathological injuries and neutrophil infiltration as well as improved epithelial integrity. HucMSC-exo up-regulated the expression of leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5), a specific marker for ISCs and accelerated the proliferation of intestinal epithelium. HucMSC-exo endowed intestinal organoids with more excellent capacity to grow and bud under TNF-α stimulation. More than that, the fact that hucMSC-exo activated the canonical Wnt signaling pathway to promote mucosal healing was uncovered by not only RNA-sequencing but also relevant experimental data. Finally, bioinformatics analysis of the existing miRNA expression datasets indicated that several miRNAs abundant in hucMSC-exo involved widely in regeneration or repair related biological processes and Wnt signaling pathway might be one of the most important signal transduction pathways.

Conclusion

Our results suggested that hucMSC-exo could facilitate mucosal healing in experimental colitis by accelerating ISCs and intestinal epithelium regeneration via transferring key miRNAs, which was dependent on the activation of Wnt/β-catenin signaling pathway.

Key elements determining the intestinal region-specific environment of enteric neurons in type 1 diabetes

Diabetes, as a metabolic disorder, is accompanied with several gastrointestinal (GI) symptoms, like abdominal pain, gastroparesis, diarrhoea or constipation. Serious and complex enteric nervous system damage is confirmed in the background of these diabetic motility complaints. The anatomical length of the GI tract, as well as genetic, developmental, structural and functional differences between its segments contribute to the distinct, intestinal region-specific effects of hyperglycemia. These observations support and highlight the importance of a regional approach in diabetes-related enteric neuropathy. Intestinal large and microvessels are essential for the blood supply of enteric ganglia. Bidirectional morpho-functional linkage exists between enteric neurons and enteroglia, however, there is also a reciprocal communication between enteric neurons and immune cells on which intestinal microbial composition has crucial influence. From this point of view, it is more appropriate to say that enteric neurons partake in multidirectional communication and interact with these key players of the intestinal wall. These interplays may differ from segment to segment, thus, the microenvironment of enteric neurons could be considered strictly regional. The goal of this review is to summarize the main tissue components and molecular factors, such as enteric glia cells, interstitial cells of Cajal, gut vasculature, intestinal epithelium, gut microbiota, immune cells, enteroendocrine cells, pro-oxidants, antioxidant molecules and extracellular matrix, which create and determine a gut region-dependent neuronal environment in diabetes.

Histological assessment of intestinal injury by ionizing radiation

Given the potential risk of radiological terrorism and disasters, it is essential to develop plans to prepare for such events. In these hazardous scenarios, radiation-induced gastrointestinal (GI) syndrome is one of the many manifestations that may happen after the organism is exposed to a lethal dose of ionizing radiation. Therefore, it is critical to better understand how the intestinal tissues initiate and orchestrate regeneration following severe radiation injury. In this chapter, we aimed to provide several key considerations for researchers who utilize histological assessment to study radiation-induced intestinal injury. Rigor and reproducibility are critical in experimental design and can be achieved by maintaining proper radiation administration, maintaining consistency in sample collection, and selecting and using appropriate controls. We also provided technical details of histological preparation of the intestines with tips on dissecting, cleaning, fixing, and preserving. Step-by-step descriptions of both bundling and Swiss rolling are provided with discussion on how to choose between the two approaches. In the following section, we detailed several histological assessment methods and then provided suggestions on how to use histological assessment to study cellular dynamics in the small intestines. Finally, we touched on some non-histological assessments. We hope that the information provided in this chapter will contribute to the research society of radiation-induced intestinal injury with an ultimate goal of promoting the development of radiation countermeasures against the GI acute radiation syndrome.

Metabolites as signalling molecules

Traditional views of cellular metabolism imply that it is passively adapted to meet the demands of the cell. It is becoming increasingly clear, however, that metabolites do more than simply supply the substrates for biological processes; they also provide critical signals, either through effects on metabolic pathways or via modulation of other regulatory proteins. Recent investigation has also uncovered novel roles for several metabolites that expand their signalling influence to processes outside metabolism, including nutrient sensing and storage, embryonic development, cell survival and differentiation, and immune activation and cytokine secretion. Together, these studies suggest that, in contrast to the prevailing notion, the biochemistry of a cell is frequently governed by its underlying metabolism rather than vice versa. This important shift in perspective places common metabolites as key regulators of cell phenotype and behaviour. Yet the signalling metabolites, and the cognate targets and transducers through which they signal, are only beginning to be uncovered. In this Review, we discuss the emerging links between metabolism and cellular behaviour. We hope this will inspire further dissection of the mechanisms through which metabolic pathways and intermediates modulate cell function and will suggest possible drug targets for diseases linked to metabolic deregulation.

Potential Effect of Glutamine in the Improvement of Intestinal Stem Cell Proliferation and the Alleviation of Burn-Induced Intestinal Injury via Activating YAP: A Preliminary Study

Burn injury is a common form of traumatic injury that leads to high mortality worldwide. A severe burn injury usually induces gut barrier dysfunction, partially resulting from the impairment in the proliferation and self-renewal of intestinal stem cells (ISCs) post burns. As a main energy substance of small intestinal enterocytes, glutamine (Gln) is important for intestinal cell viability and growth, while its roles in ISCs-induced regeneration after burns are still unclear. To demonstrate the potential effects of Gln in improving ISCs proliferation and alleviating burn-induced intestinal injury, in this study, we verified that Gln significantly alleviated small intestine injury in burned mice model. It showed that Gln could significantly decrease the ferroptosis of crypt cells in the ileum, promote the proliferation of ISCs, and repair the crypt. These effects of Gln were also confirmed in the mouse small intestine organoids model. Further research found that Yes-associated protein (YAP) is suppressed after burn injury, and Gln could improve cell proliferation and accelerate the renewal of the damaged intestinal mucosal barrier after burns by activating YAP. YAP is closely associated with the changes in intestinal stem cell proliferation after burn injury and could be served as a potential target for severe burns.

Insights into radiation carcinogenesis based on dose-rate effects in tissue stem cells

PURPOSE

Increasing epidemiological and biological evidence suggests that radiation exposure enhances cancer risk in a dose-dependent manner. This can be attributed to the 'dose-rate effect,' where the biological effect of low dose-rate radiation is lower than that of the same dose at a high dose-rate. This effect has been reported in epidemiological studies and experimental biology, although the underlying biological mechanisms are not completely understood. In this review, we aim to propose a suitable model for radiation carcinogenesis based on the dose-rate effect in tissue stem cells.

METHODS

We surveyed and summarized the latest studies on the mechanisms of carcinogenesis. Next, we summarized the radiosensitivity of intestinal stem cells and the role of dose-rate in the modulation of stem-cell dynamics after irradiation.

RESULTS

Consistently, driver mutations can be detected in most cancers from past to present, supporting the hypothesis that cancer progression is initiated by the accumulation of driver mutations. Recent reports demonstrated that driver mutations can be observed even in normal tissues, which suggests that the accumulation of mutations is a necessary condition for cancer progression. In addition, driver mutations in tissue stem cells can cause tumors, whereas they are not sufficient when they occur in non-stem cells. For non-stem cells, tissue remodeling induced by marked inflammation after the loss of tissue cells is important in addition to the accumulation of mutations. Therefore, the mechanism of carcinogenesis differs according to the cell type and magnitude of stress. In addition, our results indicated that non-irradiated stem cells tend to be eliminated from three-dimensional cultures of intestinal stem cells (organoids) composed of irradiated and non-irradiated stem cells, supporting the stem-cell competition.

CONCLUSIONS

We propose a unique scheme in which the dose-rate dependent response of intestinal stem cells incorporates the concept of the threshold of stem-cell competition and context-dependent target shift from stem cells to whole tissue. The concept highlights four key issues that should be considered in radiation carcinogenesis: i.e. accumulation of mutations; tissue reconstitution; stem-cell competition; and environmental factors like epigenetic modifications.

Mesenchymal stem cells: Emerging concepts and recent advances in their roles in organismal homeostasis and therapy

Stem cells play a crucial role in re-establishing homeostasis in the body, and the search for mechanisms by which they interact with the host to exert their therapeutic effects remains a key question currently being addressed. Considering their significant regenerative/therapeutic potential, research on mesenchymal stem cells (MSCs) has experienced an unprecedented advance in recent years, becoming the focus of extensive works worldwide to develop cell-based approaches for a variety of diseases. Initial evidence for the effectiveness of MSCs therapy comes from the restoration of dynamic microenvironmental homeostasis and endogenous stem cell function in recipient tissues by systemically delivered MSCs. The specific mechanisms by which the effects are exerted remain to be investigated in depth. Importantly, the profound cell-host interplay leaves persistent therapeutic benefits that remain detectable long after the disappearance of transplanted MSCs. In this review, we summarize recent advances on the role of MSCs in multiple disease models, provide insights into the mechanisms by which MSCs interact with endogenous stem cells to exert therapeutic effects, and refine the interconnections between MSCs and cells fused to damaged sites or differentiated into functional cells early in therapy.

Dendrobium fimbriatum polysaccharide ameliorates DSS-induced intestinal mucosal injury by IL-22-regulated intestinal stem cell regeneration

Ulcerative colitis (UC) is a chronic inflammatory bowel disease with unknown etiology and difficult treatment. In this study, the intervention effect of Dendrobium fimbriatum Hook polysaccharide (cDFPW1) on UC was verified by constructing a dextran sulfate sodium (DSS)-induced colitis mouse model, and the protective effect of cDFPW1 on intestinal mucosal integrity in UC was explored by the co-culture system consisting of intestinal organoids and lamina propria lymphocytes (LPLs) combined with the experiment of microbial depletion mice. Results showed that cDFPW1 significantly alleviated UC symptoms in mice and promoted the proliferation of intestinal epithelial cells. Importantly, cDFPW1 could directly improve DSS-induced morphological damage of intestinal organoids and increase the number of epithelial cells, which was validated in mice. During repair, an increase in the number of Lgr5⁺ cells in intestinal organoids and mouse intestines was promoted by cDFPW1. Meanwhile, cDFPW1 promoted intestinal stem cells (ISCs)-mediated intestinal epithelial regeneration by significantly upregulating IL-22 expression. We further confirmed that the secretion of IL-22 was mediated by LPLs. Together, these findings suggest that cDFPW1 promotes ISCs regeneration by LPLs-mediated up-regulation of IL-22 to protect the intestinal mucosal integrity, thereby playing an important role in improving UC.

Obligate role for Rock1 and Rock2 in adult stem cell viability and function

The ability of stem cells to rapidly proliferate and differentiate is integral to the steady-state maintenance of tissues with high turnover such as the blood and intestine. Mutations that alter these processes can cause primary immunodeficiencies, malignancies and defects in barrier function. The Rho-kinases, Rock1 and Rock2, regulate cell shape and cytoskeletal rearrangement, activities essential to mitosis. Here, we use inducible gene targeting to ablate Rock1 and Rock2 in adult mice, and identify an obligate requirement for these enzymes in the preservation of the hematopoietic and gastrointestinal systems. Hematopoietic cell progenitors devoid of Rho-kinases display cell cycle arrest, blocking the differentiation to mature blood lineages. Similarly, these mice exhibit impaired epithelial cell renewal in the small intestine, which is ultimately fatal. Our data reveal a novel role for these kinases in the proliferation and viability of stem cells and their progenitors, which is vital to maintaining the steady-state integrity of these organ systems.

General transcription factor TAF4 antagonizes epigenetic silencing by Polycomb to maintain intestine stem cell functions

Taf4 (TATA-box binding protein-associated factor 4) is a subunit of the general transcription factor TFIID, a component of the RNA polymerase II pre-initiation complex that interacts with tissue-specific transcription factors to regulate gene expression. Properly regulated gene expression is particularly important in the intestinal epithelium that is constantly renewed from stem cells. Tissue-specific inactivation of Taf4 in murine intestinal epithelium during embryogenesis compromised gut morphogenesis and the emergence of adult-type stem cells. In adults, Taf4 loss impacted the stem cell compartment and associated Paneth cells in the stem cell niche, epithelial turnover and differentiation of mature cells, thus exacerbating the response to inflammatory challenge. Taf4 inactivation ex vivo in enteroids prevented budding formation and maintenance and caused broad chromatin remodeling and a strong reduction in the numbers of stem and progenitor cells with a concomitant increase in an undifferentiated cell population that displayed high activity of the Ezh2 and Suz12 components of Polycomb Repressive Complex 2 (PRC2). Treatment of Taf4-mutant enteroids with a specific Ezh2 inhibitor restored buddings, cell proliferation and the stem/progenitor compartment. Taf4 loss also led to increased PRC2 activity in cells of adult crypts associated with modification of the immune/inflammatory microenvironment that potentiated Apc-driven tumorigenesis. Our results reveal a novel function of Taf4 in antagonizing PRC2-mediated repression of the stem cell gene expression program to assure normal development, homeostasis, and immune-microenvironment of the intestinal epithelium.