Epithelial Renewal Research Articles

The loss of antioxidant activities impairs intestinal epithelium homeostasis by altering lipid metabolism

Reactive oxygens species (ROS) are common byproducts of metabolic reactions and could be at the origin of many diseases of the elderly. Here we investigated the role of ROS in the renewal of the intestinal epithelium in mice lacking catalase (CAT) and/or nicotinamide nucleotide transhydrogenase (NNT) activities. Cat−/− mice have delayed intestinal epithelium renewal and were prone to develop necrotizing enterocolitis upon starvation. Interestingly, crypts lacking CAT showed fewer intestinal stem cells (ISC) and lower stem cell activity than wild-type. In contrast, crypts lacking NNT showed a similar number of ISCs as wild-type but increased stem cell activity, which was also impaired by the loss of CAT. No alteration in the number of Paneth cells (PCs) was observed in crypts of either Cat−/− or Nnt−/− mice, but they showed an evident decline in the amount of lysozyme. Cat deficiency caused fat accumulation in crypts, and a fall in the remarkable high amount of adipose triglyceride lipase (ATGL) in PCs. Notably, the low levels of ATGL in the intestine of Cat −/− mice increased after a treatment with the antioxidant N-acetyl-L-cysteine. Supporting a role of ATGL in the regulation of ISC activity, its inhibition halt intestinal organoid development. These data suggest that the reduction in the renewal capacity of intestine originates from fatty acid metabolic alterations caused by peroxisomal ROS.

A14 ABLATION OF THE INTESTINAL EPITHELIAL SIALOME PREDISPOSES TO SPONTANEOUS COLITIS AND COLITIS-ASSOCIATED TUMORIGENESIS VIA MUCUS-DEPENDENT AND -INDEPENDENT MECHANISMS IN MICE

Abstract Background Recent work suggests epithelial sialylation (capping of glycoconjugates with the acidic sugar sialic acid) can protect the gut mucosa from inflammatory bowel disease by promoting mucus function. However, these studies are based on partial sialylation knockouts, potentially underestimating the role of glycoconjugate sialylation in mucosal homeostasis. Aims We sought to uncover how the complete intestinal epithelial sialome (the total glycan sialylation repetoire) regulates colitis susceptibility in vivo. Methods We generated a model of total gut epithelial sialylation deficiency by conditionally and inducibly (via tamoxifen, TM) targeting the CMP-Sia transporter, Slc35a1, in epithelial cells using Cre-Lox technology (Slc35a1f/f; VillinCre(ERT2) or (TM-)IEC Slc35a1-/- mice). We analyzed phenotypes clinically, histologicaly, and via multi-omic apporaches at baseline and in response to challenge. Results We confirmed the ablation of mucus sialylation via lectin staining, epithelial Slc35a1 gene expression, and O-glycomics of extracted mucins. In contrast to partial sialylation deficiencies, we found that IEC Slc35a1-/- mice developed mild spontaneous microbiota-dependent chronic colitis that was associated with tumorigenesis in the rectum in 30% of aged mice (>12 mo.). TM-IEC Slc35a1-/- mice developed less severe spontaneous colitis, but were susceptible to acute injury with 1% DSS. Ablation of the gut epithelial sialome led to reduced mucus thickness on fecal sections and within tissues, although the b1/b2 barrier layers were still intact. TM-IEC Slc35a1-/- mice showed altered microbiota composition with an increase in Clostridium spp. at the expense of a global reduction in the abundance of at least 20 unique taxa; however metabolomic analysis did not show any significant differences in short-chain fatty acid levels. IEC Slc35a1-/- Muc2 was more susceptible to fecal protease degradation vs.WT Muc2. While no spontaneous phenotype was observed in the small intestine (SI), treatment with 5-fluorouracil led to worsened SI mucositis and morbidity vs. WT littermates. This was traced to impaired stem cell activities via reduced Lgr5+ cell representation in small intestinal crypts in IEC Slc35a1-/-;Lgr5GFP mice. Conclusions Ablation of the intestinal epithelial sialome impacts the mucus-microbiota-stem cell axis with consequences on colonic mucosal homeostasis based on the type of injury. At baseline, loss of sialylation impairs mucus stability and the stem cell niche leading to microbiota-dependent spontaneous colitis and tumorigenesis. However, these same epithelial defects impair epithelial renewal and worsen colitis following acute injury likely due to the cytotoxic environment caused by the chemical agent. Funding Agencies CCC

A23 IMPAIRMENT OF INTESTINAL CRYPTAL STEM CELL CYCLE AND PANETH CELL PROLIFERATION BY CHRONIC STRESS

Abstract Background The small intestine’s epithelial barrier is essential for intestinal homeostasis and host defense. It consists of epithelial cells that are constantly renewed by crypt stem cells and their progeny, which have different functions in the gut. Chronic stress can impair the barrier by modulating the gut-brain axis, which involves the hypothalamic-pituitary-adrenal (HPA) axis, the vagus nerve, and the immune system. Chronic stress can also alter the gut microbiota, which can further influence the barrier and immune system. Aims The present study examines how chronic stress affects the crypt stem cell niche and function in the small intestine. Methods Restraint stress was applied to 6-8 weeks old mice in a plastic container for 1 hour daily for 7 days. The dark/light transition box test was used to evaluate the stress-induced behavior change. The Ussing chamber technique was used to assess the paracellular permeability of the small intestine. RNA was extracted from the mucosa and submucosa layers of the small intestine, after removing the muscle layer, and RNA sequencing analysis was performed. Immunofluorescence analysis was also performed on the small intestinal tissues to detect the expression of various markers. To assess the in vivo effect of cortisol, dexamethasone (a synthetic steroid activating same receptors as cortisol), or metyrapone (an 11β-hydroxylation blocker to inhibit cortisol production), was applied to the mice. Results We found that restraint stress induced anxiety-like behavior, increased small intestinal epithelial permeability, and reduced villus and crypt length in mice. RNA sequencing analysis revealed that restraint stress upregulated steroid-driven pathways and downregulated cell cycle and cell mitosis pathways in the small intestinal mucosa, suggesting increased cortisol production and decreased stem cell activity. Immunofluorescence analysis confirmed that restraint stress reduced the expression of stem cell marker Olfm-4 and proliferation markers Ki-67 and p-H3 in the small intestinal crypts. Dexamethasone, a synthetic glucocorticoid, mimicked the effects of restraint stress on crypt stem cell proliferation, while metyrapone, a steroid synthesis inhibitor, attenuated the effects of restraint stress on crypt stem cell proliferation. Restraint stress and dexamethasone also reduced Paneth cell RNA expression and marker in the small intestine. Conclusions Chronic stress induces anxiety, barrier dysfunction, and epithelial shortening. Chronic stress also alters crypt stem cell and Paneth cell expression. These findings show how chronic stress impacts intestinal epithelial renewal and differentiation, which may affect intestinal health and disease. Funding Agencies JSPS

Death receptor 5 is required for intestinal stem cell activity during intestinal epithelial renewal at homoeostasis

Intestinal epithelial renewal, which depends on the proliferation and differentiation of intestinal stem cells (ISCs), is essential for epithelial homoeostasis. Understanding the mechanism controlling ISC activity is important. We found that death receptor 5 (DR5) gene deletion (DR5-/-) mice had impaired epithelial absorption and barrier function, resulting in delayed weight gain, which might be related to the general reduction of differentiated epithelial cells. In DR5-/- mice, the expression of ISC marker genes, the number of Olfm4+ ISCs, and the number of Ki67+ and BrdU+ cells in crypt were reduced. Furthermore, DR5 deletion inhibited the expression of lineage differentiation genes driving ISC differentiation into enterocytes, goblet cells, enteroendocrine cells, and Paneth cells. Therefore, DR5 gene loss may inhibit the intestinal epithelial renewal by dampening ISC activity. The ability of crypts from DR5-/- mice to form organoids decreased, and selective DR5 activation by Bioymifi promoted organoid growth and the expression of ISC and intestinal epithelial cell marker genes. Silencing of endogenous DR5 ligand TRAIL in organoids down-regulated the expression of ISC and intestinal epithelial cell marker genes. So, DR5 expressed in intestinal crypts was involved in the regulation of ISC activity. DR5 deletion in vivo or activation in organoids inhibited or enhanced the activity of Wnt, Notch, and BMP signalling through regulating the production of Paneth cell-derived ISC niche factors. DR5 gene deletion caused apoptosis and DNA damage in transit amplifying cells by inhibiting ERK1/2 activity in intestinal crypts. Inhibition of ERK1/2 with PD0325901 dampened the ISC activity and epithelial regeneration. In organoids, when Bioymifi’s effect in activating ERK1/2 activity was completely blocked by PD0325901, its role in stimulating ISC activity and promoting epithelial regeneration was also eliminated. In summary, DR5 in intestinal crypts is essential for ISC activity during epithelial renewal under homoeostasis.

Molecular Mechanisms of Reelin in the Enteric Nervous System and the Microbiota-Gut-Brain Axis: Implications for Depression and Antidepressant Therapy.

Current pharmacological treatments for depression fail to produce adequate remission in a significant proportion of patients. Increasingly, other systems, such as the microbiome-gut-brain axis, are being looked at as putative novel avenues for depression treatment. Dysbiosis and dysregulation along this axis are highly comorbid with the severity of depression symptoms. The endogenous extracellular matrix protein reelin is present in all intestinal layers as well as in myenteric and submucosal ganglia, and its receptors are also present in the gut. Reelin secretion from subepithelial myofibroblasts regulates cellular migration along the crypt-villus axis in the small intestine and colon. Reelin brain expression is downregulated in mood and psychotic disorders, and reelin injections have fast antidepressant-like effects in animal models of depression. This review seeks to discuss the roles of reelin in the gastrointestinal system and propose a putative role for reelin actions in the microbiota-gut-brain axis in the pathogenesis and treatment of depression, primarily reflecting on alterations in gut epithelial cell renewal and in the clustering of serotonin transporters.

The aryl hydrocarbon receptor pathway: a linking bridge between the gut microbiome and neurodegenerative diseases.

The Aryl hydrocarbon receptor (AHR) is a cytosolic receptor and ligand-activated transcription factor widely expressed across various cell types in the body. Its signaling is vital for host responses at barrier sites, regulating epithelial renewal, barrier integrity, and the activities of several types of immune cells. This makes AHR essential for various cellular responses during aging, especially those governing inflammation and immunity. In this review, we provided an overview of the mechanisms by which the AHR mediates inflammatory response at gut and brain level through signals from intestinal microbes. The age-related reduction of gut microbiota functions is perceived as a trigger of aberrant immune responses linking gut and brain inflammation to neurodegeneration. Thus, we explored gut microbiome impact on the nature and availability of AHR ligands and outcomes for several signaling pathways involved in neurodegenerative diseases and age-associated decline of brain functions, with an insight on Parkinson's and Alzheimer's diseases, the most common neurodegenerative diseases in the elderly. Specifically, we focused on microbial tryptophan catabolism responsible for the production of several AHR ligands. Perspectives for the development of microbiota-based interventions targeting AHR activity are presented for a healthy aging.

Curcumin promotes renewal of intestinal epithelium by miR-195-3p

Ethnopharmacological relevanceTurmeric (Curcuma longa) has been used to treat gastrointestinal disorders in the Indian Ayurvedic medical system. According to the theory behind traditional Chinese medicine, turmeric can be distributed in the spleen meridian, for which it has been used as a digestive aid. Curcumin (Cur), a natural polyphenol compound originally derived from turmeric, has anti-inflammatory activity and can assist in treating inflammatory bowel disease. Aims of the studyTo investigate curcumin's protective effects on intestinal epithelium and explore the underlying miR-195-3p-related mechanisms. Materials and methodsThe miR-195-3p mimics were used to over-express miR-195-3p. The in vitro effects of Cur and miR-195-3p on the intestine were shown utilizing intestinal cryptlike epithelial cell line-6 (IEC-6) cells. By fasting for 48 h, an intestinal mucosal atrophy model of SD rats was created in vivo. Cur (25 or 50 mg/kg) was assessed for its protective effect on intestinal epithelium. Glycyrrhetinic acid (GA) with an intestinal protective effect reported in our previous research was adopted as a positive drug for the in vivo and in vitro bioactivity evaluation since there is no universally positive drug for either intestinal mucosal restitution or miR-195-3p modulation. ResultsCur protects the intestinal epithelium and promotes its repair after injury via down-regulating miR-195-3p. In vitro experiments showed that Cur inhibited the apoptosis of IEC-6 cells, stimulated their growth, and down-regulated the level of miR-195-3p in cells. When miR-195-3p was overexpressed, the viability of IEC-6 cells decreased while the apoptosis rate increased. All the above detrimental effects were alleviated after curcumin intervention. Moreover, Cur reversed the effect of miR-195-3p on its downstream occludin. In vivo, results showed that 48-h fasting impaired the integrity of the small intestinal mucosa (abnormal crypt structure and reduced goblet cell number), which was ameliorated by Cur treatment. In addition, the Cur treatment reversed both the increased expression level of miR-195-3p and decreased levels of ki-67 and occludin caused by fasting. ConclusionsCur could promote the proliferation and repair after injury of the intestinal mucosa by down-regulating miR-195-3p.

The Role of Mitochondrial in Intestinal Epithelial Barrier Dysfunction during Inflammatory Bowel Disease

Inflammatory bowel diseases are widely spread in industrial countries with every 20th citizen being affected. Dysregulation of epithelial barrier function is considered to play a key role in the development of inflammatory bowel diseases. Intestinal epithelium permeability depends mostly on the condition of intercellular contacts and epithelial cells' renewal ability. Mitochondria participate in the regulation of various intracellular processes besides performing the energetic function. Recent data indicate the potential role of mitochondria in intestinal epithelial barrier regulation and inflammatory bowel diseases onset. Mitochondrial dysfunction may be one of the reasons for disruption of the structure of tight junctions and the cytoskeleton of intestinal epithelial cells, as well as a decrease in the ability of the epithelial lining to self-renewal. All this leads to a decrease in the barrier function of the intestinal epithelium and the development of inflammatory bowel diseases. Nevertheless, the mechanisms of these processes are still unclear and further research is required.

Heterogeneous murine peribiliary glands orchestrate compartmentalized epithelial renewal

The extrahepatic branches of the biliary tree have glands that connect to the surface epithelium through narrow pits. The duct epithelia undergo homeostatic renewal, yet the identity and multiplicity of cells that maintain this tissue is unknown. Using marker-free and targeted clonal fate mapping in mice, we provide evidence that the extrahepatic bile duct is compartmentalized. Pit cholangiocytes of extramural glands renewed the surface epithelium, whereas basally oriented cholangiocytes maintained the gland itself. In contrast, basally positioned cholangiocytes replenished the surface epithelium in mural glands. Single-cell sequencing identified genes enriched in the base and surface epithelial populations, with trajectory analysis showing graded gene expression between these compartments. Epithelia were plastic, changing cellular identity upon fasting and refeeding. Gain of canonical Wnt signaling caused basal cell expansion, gastric chief cell marker expression, and a decrease in surface epithelial markers. Our results identify the cellular hierarchy governing extrahepatic biliary epithelial renewal.

Maternal Folic Acid Supplementation Improves the Intestinal Health of Offspring Porcine by Promoting the Proliferation and Differentiation of Intestinal Stem Cells.

Maternal folic acid intake has important effects on offspring growth and development. The mechanism involved in the renewal of intestinal epithelial cells remains unclear. Thus, this study aimed to investigate the potential effect of maternal folic acid supplementation during gestation and lactation on the structural and functional development of the small intestine in piglet offspring. Twenty-four Duroc sows were assigned to a control group (CON) and a folic-acid-supplemented group (CON + FA, supplemented with 15 mg/kg of folic acid). The results showed that maternal folic acid supplementation throughout gestation and lactation significantly increased the body weight, serum folate level, and intestinal folate metabolism in piglets. It also improved the villus length, villus height-to-crypt depth ratio, and transcript levels of nutrient transporters (GLUT4, SNAT2, FABP2, and SLC7A5) in piglets' duodenum and jejunum. In addition, maternal folic acid supplementation increased Ki67-positive cells and the expression of proliferation-related marker genes (C-Myc, CyclinD1, and PCNA) in piglets' intestinal stem cells. It also boosted the expression of genes associated with mature secreted cells (ChrA, Muc2, Lyz, Vil1), indicating enhanced proliferation and differentiation of intestinal stem cells. These findings demonstrate that maternal folic acid supplementation enhances growth performance and gut health in piglet offspring by promoting epithelial cell renewal equilibrium.

MRTF-A gain-of-function in mice impairs homeostatic renewal of the intestinal epithelium

The actin-regulated transcription factor MRTF-A represents a central relay in mechanotransduction and controls a subset of SRF-dependent target genes. However, gain-of-function studies in vivo are lacking. Here we characterize a conditional MRTF-A transgenic mouse model. While MRTF-A gain-of-function impaired embryonic development, induced expression of constitutively active MRTF-A provoked rapid hepatocyte ballooning and liver failure in adult mice. Specific expression in the intestinal epithelium caused an erosive architectural distortion, villus blunting, cryptal hyperplasia and colonic inflammation, resulting in transient weight loss. Organoids from transgenic mice repeatedly induced in vitro showed impaired self-renewal and defective cryptal compartments. Mechanistically, MRTF-A gain-of-function decreased proliferation and increased apoptosis, but did not induce fibrosis. MRTF-A targets including Acta2 and Pai-1 were induced, whereas markers of stem cells and differentiated cells were reduced. Our results suggest that activated MRTF-A in the intestinal epithelium shifts the balance between proliferation, differentiation and apoptosis.

Ocular Surface Regeneration by Limbal Stem Cells Therapies: State of the Art, Challenges, and Perspectives.

Limbal stem cells (LSCs) are adult stem cells located at the limbus ensuring the continuous renewal of the corneal epithelium, critical to maintain an optimal visual function. Damages to the LSCs or their niche microenvironment lead to limbal stem cell deficiency (LSCD), a potentially blinding disease. Transplantation of LSCs as a treatment for severe to total LSCD has gained popularity since 1980s, owing to the clinical success of the first direct limbal autograft transplantation. Recent advances in the understanding of the LSCs' molecular identity and regulation have enabled preclinical and clinical advancements of promising LSCs therapies. However, lack of standardization of the diagnostic methods, staging of the disease severity, manufacturing process, and clinical outcome measures have hindered the advancement of the therapy. To move these therapies to the clinic, optimization and standardization of the diagnostic strategy, cell product manufacturing, and assessment of clinical efficacy with potency assays are key points to the development of customized therapies. Recent findings suggest that residual LSCs exist in eyes presenting with clinical signs of total LSCD, which opens new therapeutic strategies for eyes with partial LSCD. Prospective, randomized, multicentric controlled clinical trials are necessary to determine the efficacy of different LSCs therapies for different stages of LSCD using a set of standardized outcome measures.

Control of Paneth cell function by HuR regulates gut mucosal growth by altering stem cell activity.

Rapid self-renewal of the intestinal epithelium requires the activity of intestinal stem cells (ISCs) that are intermingled with Paneth cells (PCs) at the crypt base. PCs provide multiple secreted and surface-bound niche signals and play an important role in the regulation of ISC proliferation. Here, we show that control of PC function by RNA-binding protein HuR via mitochondria affects intestinal mucosal growth by altering ISC activity. Targeted deletion of HuR in mice disrupted PC gene expression profiles, reduced PC-derived niche factors, and impaired ISC function, leading to inhibited renewal of the intestinal epithelium. Human intestinal mucosa from patients with critical surgical disorders exhibited decreased levels of tissue HuR and PC/ISC niche dysfunction, along with disrupted mucosal growth. HuR deletion led to mitochondrial impairment by decreasing the levels of several mitochondrial-associated proteins including prohibitin 1 (PHB1) in the intestinal epithelium, whereas HuR enhanced PHB1 expression by preventing microRNA-195 binding to the Phb1 mRNA. These results indicate that HuR is essential for maintaining the integrity of the PC/ISC niche and highlight a novel role for a defective PC/ISC niche in the pathogenesis of intestinal mucosa atrophy.

L-Malic Acid Facilitates Stem Cell-Driven Intestinal Epithelial Renewal through the Amplification of β-Catenin Signaling by Targeting Frizzled7 in Chicks.

l-Malic acid (l-MA) contributes to energy metabolism and nutrient digestion, which is an alternative to antibiotics for livestock; however, it is not clear whether l-MA can replace antibiotics to promote intestinal development in chicks. To investigate the effects of l-MA on intestinal stem cells (ISCs) driving epithelial renewal, we employed in vivo chick feeding experiments, chick intestinal organoid (IO) models, and in vitro chick intestinal epithelial cell models. The results showed that the feed conversion rate and diarrhea scores were decreased with improved jejunal morphology and barrier function in the 0.5% l-MA group. l-MA promoted the proliferation and differentiation of ISCs, inhibited the cell apoptosis, increased the IO formation efficiency, surface area, budding efficiency, and number of buds, suggesting that l-MA promoted the expansion of ISCs. Furthermore, l-MA treatment dramatically upregulated the Wnt/β-catenin signaling pathway in the jejunum. Importantly, Wnt transmembrane receptor Frizzled7 (FZD7) mRNA abundance was increased in response to dietary 0.5% l-MA. In addition, molecular docking analysis using Autodock software and isothermal titration calorimetry revealed that l-MA binds to Lys91 of FZD7 with high affinity, indicating a spontaneous interaction. The chick intestinal epithelial cells treated with 10 μM l-MA significantly increased cell viability, and the Wnt/β-catenin signaling pathway was activated, but l-MA failed to upregulate the Wnt/β-catenin signaling when treated with the FZD7-specific inhibitor Fz7-21 in chick intestinal epithelial cells, indicating that FZD7 is indispensable for l-MA activation of the Wnt/β-catenin signaling. Collectively, l-MA stimulated β-catenin signaling by targeting transmembrane receptor FZD7, which promoted ISC expansion and inhibited cell apoptosis to accelerate intestinal epithelial renewal in chicks.

Production and limbal lineage commitment of aniridia patient-derived induced pluripotent stem cells.

Congenital aniridia is caused by heterozygous mutations on the PAX6 gene leading to reduced amount of PAX6 protein (haploinsufficiency), abnormal eye development and aniridia-associated keratopathy (AAK). This progressive corneal opacification resembles late-onset limbal stem cell (LSC) deficiency, leading to disrupted corneal epithelial renewal. The factors leading to AAK are not known and defects in native LSC differentiation and/or features leading to ocular surface dysfunction like inflammation and loss of innervation could contribute to development of AAK. Here, we produced induced pluripotent stem cells (hiPSC) from three AAK patients and examined whether PAX6 haploinsufficiency affects LSC lineage commitment. During LSC differentiation, characterization of the AAK lines showed lowered PAX6 expression as compared to wild type (WT) controls and expression peak of PAX6 during early phase of differentiation was detected only in the WT hiPSC lines. Whether it reflects developmental regulation remains to be studied further. Nevertheless, the AAK-hiPSCs successfully differentiated towards LSC lineage, in line with the presence of LSCs in young patients before cell loss later in life. In addition, patient specific LSCs showed similar wound healing capacity as WT cells. However, extensive batch-related variation in the LSC marker expression and wound healing efficacy was detected without clear correlation to AAK. As development and maintenance of corneal epithelium involves an interplay between LSCs and their environment, the AAK-hiPSCs generated here can be further used to study the crosstalk between LSCs and limbal niche including e.g. corneal immune cells, stroma cells and neurons.

Licochalcone A promotes renewal of intestinal mucosa through modulating uc.173

Ethnopharmacological relevanceLicorice can nourish Pi (spleen) and thereby strengthening the digestive system according to the theory of traditional Chinese medicine. Licorice has been generally used in the compound prescription to treat intestinal inflammatory disease. Licochalcone A (Lico A) is one of the characteristic molecules from licorice. T-UCRs, which are transcribed from ultraconserved regions, are a new class of long noncoding RNAs related to the renewal of intestinal epithelial renewal. Aim of the studyThis study aimed to investigate the effect and the uc.173-related mechanism of Lico A on intestinal epithelial renewal. Materials and methodsIE-6 and Caco-2 cells were used to evaluate the effect of Lico A on apoptosis, proliferation, and migration of IECs. The intestinal organoid was used to investigate ex vivo effect and mechanism of Lico A promoting intestinal organoid development. C57BL/6J mice (both normal and uc.173-deficient ones) were used to examine the in vivo effect of Lico A on the renewal of intestinal mucosa. ResultsThe expression of three T-UCRs related to the intestinal mucosa renewal was altered in Lico A-treated IECs. Lico A promoted the proliferation and inhibited the apoptosis of IECs through uc.173/miR-195 pathway. The development of intestinal organoids and the renewal of intestinal mucosa of mice subjected to the 48-h FAST were all promoted by the treatment of Lico A. Moreover, the growth arrest of uc.173-deficient intestinal organoids and the atrophy of intestinal mucosa in uc.173-deficient mice could be rescued by the Lico A administration. ConclusionResults in this paper suggest that targeting T-UCRs may be the novel therapeutic approach for the promotion of epithelial regeneration, and through stimulating the regeneration of intestinal mucosa, Lico A may become a new therapeutic agent for the maintenance of intestinal epithelial integrity.

The Role of Sensory Innervation in Homeostatic and Injury-Induced Corneal Epithelial Renewal.

The cornea is the window through which we see the world. Corneal clarity is required for vision, and blindness occurs when the cornea becomes opaque. The cornea is covered by unique transparent epithelial cells that serve as an outermost cellular barrier bordering between the cornea and the external environment. Corneal sensory nerves protect the cornea from injury by triggering tearing and blink reflexes, and are also thought to regulate corneal epithelial renewal via unknown mechanism(s). When protective corneal sensory innervation is absent due to infection, trauma, intracranial tumors, surgery, or congenital causes, permanent blindness results from repetitive epithelial microtraumas and failure to heal. The condition is termed neurotrophic keratopathy (NK), with an incidence of 5:10,000 people worldwide. In this report, we review the currently available therapeutic solutions for NK and discuss the progress in our understanding of how the sensory nerves induce corneal epithelial renewal.

Toward Corneal Limbus In Vitro Model: Regulation of hPSC-LSC Phenotype by Matrix Stiffness and Topography During Cell Differentiation Process.

A functional limbal epithelial stem cells (LSC) niche is a vital element in the regular renewal of the corneal epithelium by LSCs and maintenance of good vision. However, little is known about its unique structure and mechanical properties on LSC regulation, creating a significant gap in development of LSC-based therapies. Herein, the effect of mechanical and architectural elements of the niche on human pluripotent derived LSCs (hPSC-LSC) phenotype and growth is investigated in vitro. Specifically, three formulations of polyacrylamide gels with different controlled stiffnesses are used for culture and characterization of hPSC-LSCs from different stages of differentiation. In addition, limbal mimicking topography in polydimethylsiloxane is utilized for culturing hPSC-LSCs at early time point of differentiation. For comparison, the expression of selected key proteins of the corneal cells is analyzed in their native environment through whole mount staining of human donor corneas. The results suggest that mechanical response and substrate preference of the cells is highly dependent on their developmental stage. In addition, data indicate that cells may carry possible mechanical memory from previous culture matrix, both highlighting the importance of mechanical design of a functional in vitro limbus model.

RAB11A and RAB11B control mitotic spindle function in intestinal epithelial progenitor cells.

RAB11 small GTPases and associated recycling endosome have been localized to mitotic spindles and implicated in regulating mitosis. However, the physiological significance of such regulation has not been observed in mammalian tissues. We have used newly engineered mouse models to investigate intestinal epithelial renewal in the absence of single or double isoforms of RAB11 family members: Rab11a and Rab11b. Comparing with single knockouts, mice with compound ablation demonstrate a defective cell cycle entry and robust mitotic arrest followed by apoptosis, leading to a total penetrance of lethality within 3 days of gene ablation. Upon Rab11 deletion ex vivo, enteroids show abnormal mitotic spindle formation and cell death. Untargeted proteomic profiling of Rab11a and Rab11b immunoprecipitates has uncovered a shared interactome containing mitotic spindle microtubule regulators. Disrupting Rab11 alters kinesin motor KIF11 function and impairs bipolar spindle formation and cell division. These data demonstrate that RAB11A and RAB11B redundantly control mitotic spindle function and intestinal progenitor cell division, a mechanism that may be utilized to govern the homeostasis and renewal of other mammalian tissues.

Metabolism of alimentary compounds by the intestinal microbiota and consequences for gut health

The intestinal microbiota in the mammalian large intestine metabolizes numerous alimentary compounds that are not digested and absorbed in the small intestine. By doing so, microbiota produces metabolites that accumulate in the luminal fluid. Several bacterial metabolites have been shown to be involved in communication between microbes and to act on the colonic epithelial cell metabolism and physiology. In fact, effects of bacterial metabolites on energy metabolism in colonic epithelial cells, water and electrolyte movements across the colonic epithelium, and epithelial renewal and barrier function have been reported. In this review, the consequences of such interkingdom metabolic interactions are summarized by presenting typical examples of bacterial metabolites that are known to affect communication between intestinal microbes and/or between microbes and the intestinal epithelial cells. Current studies indicate that the bacterial metabolites derived from alimentary compounds affect the colonic epithelial cells either positively or negatively. These findings pave the way for further experimental and clinical studies aiming at establishing what can be done in terms of alimentary intervention to optimize host-microbe communication for beneficial effects on gut health.