Assessment of tumor development and wound healing using endoscopic techniques in mice

Reprogramming of Treg cell-derived small extracellular vesicles effectively prevents intestinal inflammation from PANoptosis by blocking mitochondrial oxidative stress

Inflammatory bowel disease (IBD) is a chronic relapsing immune-mediated inflammatory disorder of the alimentary tract without exact etiology. Mitochondrial reactive oxygen species (mtROS) derived from mitochondrial dysfunction impair intestinal barrier function, increase gut permeability, and facilitate immune cell invasion, and, therefore, are considered to have a pivotal role in the pathogenesis of IBD. Here, we reprogrammed regulatory T cell (Treg)-derived exosomes loaded with the antioxidant trace element selenium (Se) and decorated them with the synthetic mitochondria-targeting SS-31 tetrapeptide via a peptide linker. This linker can be cleaved by matrix metalloproteinases (MMPs) in inflammatory lesions. This actively targetable exosome-derived delivery system is protected from intestinal inflammation by scavenging excessive mtROS and preventing immunologically programmed cell death pyroptosis, necroptosis, and apoptosis, known as PANoptosis. Our results suggest that this engineered exosome delivery platform represents a promising targeted therapeutic strategy for the treatment of IBDs.

The role of efferocytosis in inflammatory bowel disease

Efferocytosis is the process by which various phagocytes clear apoptotic cells. In recent years, an increasing body of evidence has emphasized the importance of efferocytosis in maintaining internal homeostasis. Intestinal macrophages play a crucial role in modulating intestinal inflammation and promoting tissue repair. Inflammatory bowel disease (IBD) is a chronic, progressive, and relapsing condition, primarily marked by the presence of ulcers in the digestive tract. The exact mechanisms underlying IBD are not yet fully understood, and current treatment approaches mainly aim at repairing the damaged intestinal mucosa and reducing inflammatory responses to ease symptoms.This article provides new perspectives on IBD treatment and clinical management by examining the expression of macrophage efferocytosis-related molecules, the effects of efferocytosis on IBD development, the various roles of macrophage efferocytosis in IBD, and treatment strategies for IBD that focus on efferocytosis.

Intestinal epithelial Gasdermin C is induced by IL-4R/STAT6 signaling but is dispensable for gut immune homeostasis

Gasdermin C is one of the least studied members of the gasdermin family of proteins, known for their critical involvement in pyroptosis and host defense. Furthermore, evidence for the role of Gasdermin C in the intestine is scarce and partly controversial. Here, we tested the functional role of Gasdermin C in intestinal homeostasis, inflammation and tumorigenesis. : We studied Gasdermin C in response to cytokines in intestinal organoids. We evaluated epithelial differentiation, cell death and immune infiltration under steady state conditions in a new mouse line deficient in Gasdermin C. The role of Gasdermin C was analyzed in acute colitis, infection and colitis-associated cancer. Gasdemin C is highly expressed in the intestinal epithelium and strongly induced by the type 2 cytokines IL-4 and IL-13 in a STAT6-dependent manner. Gasdermin C-deficient mice show no changes in tissue architecture and epithelial homeostasis. Epithelial organoids deficient in Gasdermin C develop normally and show no alterations in proliferation or cell death. No changes were found in models of acute colitis, type 2 intestinal infection and colitis-associated cancer. Gasdermin C genes are upregulated by type 2 immunity, yet appear dispensable for the development of intestinal inflammation, infection and colitis-associated cancer.

Neutrophils prevent rectal bleeding in ulcerative colitis by peptidyl-arginine deiminase-4-dependent immunothrombosis

OBJECTIVE

Bleeding ulcers and erosions are hallmarks of active ulcerative colitis (UC). However, the mechanisms controlling bleeding and mucosal haemostasis remain elusive.

DESIGN

We used high-resolution endoscopy and colon tissue samples of active UC (n = 36) as well as experimental models of physical and chemical mucosal damage in mice deficient for peptidyl-arginine deiminase-4 (PAD4), gnotobiotic mice and controls. We employed endoscopy, histochemistry, live-cell microscopy and flow cytometry to study eroded mucosal surfaces during mucosal haemostasis.

RESULTS

Erosions and ulcerations in UC were covered by fresh blood, haematin or fibrin visible by endoscopy. Fibrin layers rather than fresh blood or haematin on erosions were inversely correlated with rectal bleeding in UC. Fibrin layers contained ample amounts of neutrophils coaggregated with neutrophil extracellular traps (NETs) with detectable activity of PAD. Transcriptome analyses showed significantly elevated PAD4 expression in active UC. In experimentally inflicted wounds, we found that neutrophils underwent NET formation in a PAD4-dependent manner hours after formation of primary blood clots, and remodelled clots to immunothrombi containing citrullinated histones, even in the absence of microbiota. PAD4-deficient mice experienced an exacerbated course of dextrane sodium sulfate-induced colitis with markedly increased rectal bleeding (96 % vs 10 %) as compared with controls. PAD4-deficient mice failed to remodel blood clots on mucosal wounds eliciting impaired healing. Thus, NET-associated immunothrombi are protective in acute colitis, while insufficient immunothrombosis is associated with rectal bleeding.

CONCLUSION

Our findings uncover that neutrophils induce secondary immunothrombosis by PAD4-dependent mechanisms. Insufficient immunothrombosis may favour rectal bleeding in UC.

Epithelial presenilin-1 drives colorectal tumour growth by controlling EGFR-COX2 signalling

OBJECTIVE

Psen1 was previously characterised as a crucial factor in the pathogenesis of neurodegeneration in patients with Alzheimer's disease. Little, if any, is known about its function in the gut. Here, we uncovered an unexpected functional role of Psen1 in gut epithelial cells during intestinal tumourigenesis.

DESIGN

Human colorectal cancer (CRC) and control samples were investigated for PSEN1 and proteins of theγ-secretase complex. Tumour formation was analysed in the AOM-DSS and Apc ^min/+ mouse models using newly generated epithelial-specific Psen1 deficient mice. Psen1 deficient human CRC cells were studied in a xenograft tumour model. Tumour-derived organoids were analysed for growth and RNA-Seq was performed to identify Psen1-regulated pathways. Tumouroids were generated to study EGFR activation and evaluation of the influence of prostanoids.

RESULTS

PSEN1 is expressed in the intestinal epithelium and its level is increased in human CRC. Psen1-deficient mice developed only small tumours and human cancer cell lines deficient in Psen1 had a reduced tumourigenicity. Tumouroids derived from Psen1-deficient Apc ^min/+ mice exhibited stunted growth and reduced cell proliferation. On a molecular level, PSEN1 potentiated tumour cell proliferation via enhanced EGFR signalling and COX-2 production. Exogenous administration of PGE₂ reversed the slow growth of PSEN1 deficient tumour cells via PGE₂ receptor 4 (EP4) receptor signalling.

CONCLUSIONS

Psen1 drives tumour development by increasing EGFR signalling via NOTCH1 processing, and by activating the COX-2-PGE₂ pathway. PSEN1 inhibition could be a useful strategy in treatment of CRC.

In vivo multi spectral colonoscopy in mice

Multi- and hyperspectral endoscopy are possibilities to improve the endoscopic detection of neoplastic lesions in the colon and rectum during colonoscopy. However, most studies in this context are performed on histological samples/biopsies or ex vivo. This leads to the question if previous results can be transferred to an in vivo setting. Therefore, the current study evaluated the usefulness of multispectral endoscopy in identifying neoplastic lesions in the colon. The data set consists of 25 mice with colonic neoplastic lesions and the data analysis is performed by machine learning. Another question addressed was whether adding additional spatial features based on Gauss-Laguerre polynomials leads to an improved detection rate. As a result, detection of neoplastic lesions was achieved with an MCC of 0.47. Therefore, the classification accuracy of multispectral colonoscopy is comparable with hyperspectral colonoscopy in the same spectral range when additional spatial features are used. Moreover, this paper strongly supports the current path towards the application of multi/hyperspectral endoscopy in clinical settings and shows that the challenges from transferring results from ex vivo to in vivo endoscopy can be solved.

Targeting STAT3 Signaling in COL1+ Fibroblasts Controls Colitis-Associated Cancer in Mice

Colorectal cancer (CRC) is a common disease and has limited treatment options. The importance of cancer-associated fibroblasts (CAFs) within the tumor microenvironment (TME) in CRC has been increasingly recognized. However, the role of CAF subsets in CRC is hardly understood and opposing functions of type I (COL1+) vs. type VI (COL6+) collagen-expressing subsets were reported before with respect to NFκB-related signaling. Here, we have focused on COL1+ fibroblasts, which represent a frequent CAF population in CRC and studied their role upon STAT3 activation in vivo. Using a dual strategy with a conditional gain-of-function and a conditional loss-of-function approach in an in vivo model of colitis-associated cancer, tumor development was evaluated by different readouts, including advanced imaging methodologies, e.g., light sheet microscopy and CT-scan. Our data demonstrate that the inhibition of STAT3 activation in COL1+ fibroblasts reduces tumor burden, whereas the constitutive activation of STAT3 promotes the development of inflammation-driven CRC. In addition, our work characterizes the co-expression and distribution of type I and type VI collagen by CAFs in inflammation-associated colorectal cancer using reporter mice. This work indicates a critical contribution of STAT3 signaling in COL1+ CAFs, suggesting that the blockade of STAT3 activation in type I collagen-expressing fibroblasts could serve as promising therapeutic targets in colitis-associated CRC. In combination with previous work by others and us, our current findings highlight the context-dependent roles of COL1+ CAFs and COL6+ CAFs that might be variable according to the specific pathway activated.

SMYD2 targets RIPK1 and restricts TNF-induced apoptosis and necroptosis to support colon tumor growth

SMYD2 is a histone methyltransferase, which methylates both histone H3K4 as well as a number of non-histone proteins. Dysregulation of SMYD2 has been associated with several diseases including cancer. In the present study, we investigated whether and how SMYD2 might contribute to colorectal cancer. Increased expression levels of SMYD2 were detected in human and murine colon tumor tissues compared to tumor-free tissues. SMYD2 deficiency in colonic tumor cells strongly decreased tumor growth in two independent experimental cancer models. On a molecular level, SMYD2 deficiency sensitized colonic tumor cells to TNF-induced apoptosis and necroptosis without affecting cell proliferation. Moreover, we found that SMYD2 targeted RIPK1 and inhibited the phosphorylation of RIPK1. Finally, in a translational approach, pharmacological inhibition of SMYD2 attenuated colonic tumor growth. Collectively, our data show that SMYD2 is crucial for colon tumor growth and inhibits TNF-induced apoptosis and necroptosis.

Pro-Resolving Factors Released by Macrophages After Efferocytosis Promote Mucosal Wound Healing in Inflammatory Bowel Disease

Nonresolving inflammation is a critical driver of several chronic inflammatory diseases, including inflammatory bowel diseases (IBD). This unresolved inflammation may result from the persistence of an initiating stimulus or from the alteration of the resolution phase of inflammation. Elimination of apoptotic cells by macrophages (a process called efferocytosis) is a critical step in the resolution phase of inflammation. Efferocytosis participates in macrophage reprogramming and favors the release of numerous pro-resolving factors. These pro-resolving factors exert therapeutic effects in experimental autoimmune arthritis. Here, we propose to evaluate the efficacy of pro-resolving factors produced by macrophages after efferocytosis, a secretome called SuperMApo, in two IBD models, namely dextran sodium sulfate (DSS)-induced and T cell transfer-induced colitis. Reintroducing these pro-resolving factors was sufficient to decrease clinical, endoscopic and histological colitis scores in ongoing naive T cell-transfer-induced colitis and in DSS-induced colitis. Mouse primary fibroblasts isolated from the colon demonstrated enhanced healing properties in the presence of SuperMApo, as attested by their increased migratory, proliferative and contractive properties. This was confirmed by the use of human fibroblasts isolated from patients with IBD. Exposure of an intestinal epithelial cell (IEC) line to these pro-resolving factors increased their proliferative properties and IEC acquired the capacity to capture apoptotic cells. The improvement of wound healing properties induced by SuperMApo was confirmed in vivo in a biopsy forceps-wound colonic mucosa model. Further in vivo analysis in naive T cell transfer-induced colitis model demonstrated an improvement of intestinal barrier permeability after administration of SuperMApo, an intestinal cell proliferation and an increase of α-SMA expression by fibroblasts, as well as a reduction of the transcript coding for fibronectin (Fn1). Finally, we identified TGF-β, IGF-I and VEGF among SuperMApo as necessary to favor mucosal healing and confirmed their role both in vitro (using neutralizing antibodies) and in vivo by depleting these factors from efferocytic macrophage secretome using antibody-coated microbeads. These growth factors only explained some of the beneficial effects induced by factors released by efferocytic macrophages. Overall, the administration of pro-resolving factors released by efferocytic macrophages limits intestinal inflammation and enhance tissue repair, which represents an innovative treatment of IBD.

Therapeutic Potential of a Self-Assembling Peptide Hydrogel to Treat Colonic Injuries Associated with Inflammatory Bowel Disease

BACKGROUND AND AIMS

The Self-assembling Peptide Hydrogel [SAPH, PuraMatrix], a fully synthetic peptide solution designed to replace collagen, has recently been used to promote mucosal regeneration in iatrogenic ulcers following endoscopic submucosal dissection. Herein, we evaluated its utility in ulcer repair using a rat model of topical trinitrobenzene sulphonic acid [TNBS]-induced colonic injuries.

METHODS

Colonic injuries were generated in 7-week-old rats by injecting an ethanol solution [35%, 0.2 mL] containing 0.15 M TNBS into the colonic lumen. At 2 and 4 days post-injury, the rats were subjected to endoscopy, and SAPH [or vehicle] was topically applied to the ulcerative lesion. Time-of-flight secondary ion mass spectrometry [TOF-SIMS] was used to detect SAPH. Colonic expression of cytokines and wound healing-related factors were assessed using real-time polymerase chain reaction or immunohistochemistry.

RESULTS

SAPH treatment significantly reduced ulcer length [p = 0.0014] and area [p = 0.045], while decreasing colonic weight [p = 0.0375] and histological score [p = 0.0005] 7 days after injury. SAPH treatment also decreased colonic expression of interleukin [IL]-1α [p = 0.0233] and IL-6[p = 0.0343] and increased that of claudin-1 [p = 0.0486] and villin [p = 0.0183], and β-catenin staining [p = 0.0237]. TOF-SIMS revealed lesional retention of SAPH on day 7 post-injury. Furthermore, SAPH significantly promoted healing in in vivo mechanical intestinal wound models.

CONCLUSIONS

SAPH application effectively suppressed colonic injury, downregulated inflammatory cytokine expression, and upregulated wound healing-related factor expression in the rat model; thus, it may represent a promising therapeutic strategy for IBD-related colonic ulcers.

Inducible mouse models of colon cancer for the analysis of sporadic and inflammation-driven tumor progression and lymph node metastasis

Despite advances in the detection and therapy of colorectal cancer (CRC) in recent years, CRC has remained a major challenge in clinical practice. Although alternative methods for modeling CRC have been developed, animal models of CRC remain helpful when analyzing molecular aspects of pathogenesis and are often used to perform preclinical in vivo studies of potential therapeutics. This protocol updates our protocol published in 2007, which provided an azoxymethane (AOM)-based setup for investigations into sporadic (Step 5A) and, when combined with dextran sodium sulfate (Step 5B), inflammation-associated tumor growth. This update also extends the applications beyond those of the original protocol by including an option in which AOM is serially applied to mice with p53 deficiency in the intestinal epithelium (Step 5C). In this model, the combination of p53 deficiency and AOM promotes tumor development, including growth of invasive cancers and lymph node metastasis. It also provides details on analysis of colorectal tumor growth and metastasis, including analysis of partial epithelial-to-mesenchymal transition, cell isolation and co-culture studies, high-resolution mini-endoscopy, light-sheet fluorescence microscopy and micro-CT imaging in mice. The target audience for our protocol is researchers who plan in vivo studies to address mechanisms influencing sporadic or inflammation-driven tumor development, including the analysis of local invasiveness and lymph node metastasis. It is suitable for preclinical in vivo testing of novel drugs and other interventional strategies for clinical translation, plus the evaluation of emerging imaging devices/modalities. It can be completed within 24 weeks (using Step 5A/C) or 10 weeks (using Step 5B).

Experimental Model of Rectal Carcinogenesis Induced by N-Methyl-N-Nitrosoguanidine in Mice with Endoscopic Evaluation

Background and purpose: The discovery of chemical substances with carcinogenic properties has allowed the development of several experimental models of colorectal cancer (CRC). Classically, experimental models of CRC in mice have been evaluated through clinical or serial euthanasia. The present study aims to investigate the role of low endoscopy in the analysis of carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Methods: Thirty C57BL6 mice were divided into two groups: a control group with fifteen animals that underwent rectal instillation of saline solution on day 0 and a carcinogen group with fifteen animals that underwent a 100 mg/kg MNNG rectal instillation on day 0. In both groups, low endoscopies were performed on weeks 4 and 8. We used a validated endoscopic scoring system to evaluate the severity of colitis and colorectal tumor. Euthanasia was carried out at week 12. Results: We observed higher inflammation scores (p <0.001) and a higher number of tumors (p <0.05) in the MNNG group than the control group, both at weeks 4 and 8. A worsening of inflammation scores from the first to the second endoscopy was also noticeable in the MNNG group. There were no bowel perforations related to the procedure, and there was one death in the control group. Conclusion: Low endoscopy in experimental animals allows safe macroscopic evaluation of colorectal carcinogenesis without the need for euthanasia.

Topical application of Chlorin e6-PVP (Ce6-PVP) for improved endoscopic detection of neoplastic lesions in a murine colitis-associated cancer model

Screening colonoscopy is crucial in reducing the mortality of colorectal cancer. However, detecting adenomas against the backdrop of an inflamed mucosa (e.g. in ulcerative colitis) remains exceedingly difficult. Therefore, we aimed to improve neoplastic lesion detection by employing a fluorescence-based endoscopic approach. We used the well-established murine AOM/DSS model to induce inflammation-driven carcinogenesis in the colon. In our diagnostic approach, we evaluated Chlorin e6 polyvinylpyrrolidone (Ce6-PVP)-based fluorescence endoscopy in comparison to standard white-light endoscopy. A specialized pathologist then analyzed the histology of the detected lesions. Complementary in vitro studies were performed using human cell lines and a murine organoid system. Ce6-PVP-based fluorescence endoscopy had an improved detection rate of 100% (8/8) in detecting high-grade dysplasias and carcinomas over white-light detection alone with 75% (6/8). Trade-off for this superior detection rate was an increased rate of false positive lesions with an increase in the false discovery rate from 45% for white-light endoscopy to 81% for fluorescence endoscopy. We demonstrate in a proof-of-concept study that Ce6-PVP-based fluorescence endoscopy is a highly sensitive red flag technology to identify biopsy-worthy lesions in the colon.

Non-classical monocyte homing to the gut via α4β7 integrin mediates macrophage-dependent intestinal wound healing

OBJECTIVE

To study the role of α4β7 integrin for gut homing of monocytes and to explore the biological consequences of therapeutic α4β7 inhibition with regard to intestinal wound healing.

DESIGN

We studied the expression of homing markers on monocyte subsets in the peripheral blood and on macrophage subsets in the gut of patients with IBD and controls with flow cytometry and immunohistochemistry. Integrin function was addressed with dynamic adhesion assays and in vivo gut homing assays. In vivo wound healing was studied in mice deficient for or depleted of α4β7 integrin.

RESULTS

Classical and non-classical monocytes were clearly dichotomous regarding homing marker expression including relevant expression of α4β7 integrin on human and mouse non-classical monocytes but not on classical monocytes. Monocyte-expressed α4β7 integrin was functionally important for dynamic adhesion to mucosal vascular addressin cell adhesion molecule 1 and in vivo gut homing. Impaired α4β7-dependent gut homing was associated with reduced (effect size about 20%) and delayed wound healing and suppressed perilesional presence of wound healing macrophages. Non-classical monocytes in the peripheral blood were increased in patients with IBD under clinical treatment with vedolizumab.

CONCLUSION

In addition to reported effects on lymphocytes, anti-α4β7 therapy in IBD also targets non-classical monocytes. Impaired gut homing of such monocytes might lead to a reduction of wound healing macrophages and could potentially explain increased rates of postoperative complications in vedolizumab-treated patients, which have been observed in some studies.

Environmental Microbial Factors Determine the Pattern of Inflammatory Lesions in a Murine Model of Crohn's Disease-Like Inflammation

Crohn's disease (CD) patients can be grouped into patients suffering from ileitis, ileocolitis, jejunoileitis, and colitis. The pathophysiological mechanism underlying this regional inflammation is still unknown. Although most murine models of inflammatory bowel disease (IBD) develop inflammation in the colon, there is an unmet need for novel models that recapitulate the spontaneous and fluctuating nature of inflammation as seen in CD. Recently, mice with an intestinal epithelial cell-specific deletion for Caspase-8 (Casp8ΔIEC mice), which are characterized by cell death-driven ileitis and disrupted Paneth cell homeostasis, have been identified as a novel model of CD-like ileitis. Here we uncovered that genetic susceptibility alone is sufficient to drive ileitis in Casp8ΔIEC mice. In sharp contrast, environmental factors, such as a disease-relevant microbial flora, determine colonic inflammation. Accordingly, depending on the microbial environment, isogenic Casp8ΔIEC mice either exclusively developed ileitis or suffered from pathologies in several parts of the gastrointestinal tract. Colitis in these mice was characterized by massive epithelial cell death, leading to spread of commensal gut microbes to the extra-intestinal space and hence an aberrant activation of the systemic immunity. We further uncovered that Casp8ΔIEC mice show qualitative and quantitative changes in the intestinal microbiome associated with an altered mucosal and systemic immune response. In summary, we identified that inflammation in this murine model of CD-like inflammation is characterized by an immune reaction, presumably directed against a disease-relevant microbiota in a genetically susceptible host, with impaired mucosal barrier function and bacterial clearance at the epithelial interface.

Label-Free Multiphoton Endomicroscopy for Minimally Invasive In Vivo Imaging

Multiphoton microscopy of cellular autofluorescence and second harmonic generation from collagen facilitates imaging of living cells and tissues without the need for additional fluorescent labels. Here, a compact multiphoton endomicroscope for label-free in vivo imaging in small animals via side-viewing needle objectives is presented. Minimal invasive imaging at cellular resolution is performed in colonoscopy of mice without surgical measures and without fluorescent dyes as a contrast agent. The colon mucosa is imaged repeatedly in the same animal in a mouse model of acute intestinal inflammation to study the process of inflammation at the tissue level within a time period of ten days, demonstrating the capabilities of label-free endomicroscopy for longitudinal studies for the first time.

Inhibiting Interleukin 36 Receptor Signaling Reduces Fibrosis in Mice With Chronic Intestinal Inflammation

BACKGROUND & AIMS

Intestinal fibrosis is a long-term complication in inflammatory bowel diseases (IBD) that frequently results in functional damage, bowel obstruction, and surgery. Interleukin (IL) 36 is a group of cytokines in the IL1 family with inflammatory effects. We studied the expression of IL36 and its receptor, interleukin 1 receptor like 2 (IL1RL2 or IL36R) in the development of intestinal fibrosis in human tissues and mice.

METHODS

We obtained intestinal tissues from 92 patients with Crohn's disease (CD), 48 patients with ulcerative colitis, and 26 patients without inflammatory bowel diseases (control individuals). Tissues were analyzed by histology to detect fibrosis and by immunohistochemistry to determine the distribution of fibroblasts and levels of IL36R ligands. Human and mouse fibroblasts were incubated with IL36 or control medium, and transcriptome-wide RNA sequences were analyzed. Mice were given neutralizing antibodies against IL36R, and we studied intestinal tissues from Il1rl2-/- mice; colitis and fibrosis were induced in mice by repetitive administration of DSS or TNBS. Bone marrow cells were transplanted from Il1rl2-/- to irradiated wild-type mice and intestinal tissues were analyzed. Antibodies against IL36R were applied to mice with established chronic colitis and fibrosis and intestinal tissues were studied.

RESULTS

Mucosal and submucosal tissue from patients with CD or ulcerative colitis had higher levels of collagens, including type VI collagen, compared with tissue from control individuals. In tissues from patients with fibrostenotic CD, significantly higher levels of IL36A were noted, which correlated with high numbers of activated fibroblasts that expressed α-smooth muscle actin. IL36R activation of mouse and human fibroblasts resulted in expression of genes that regulate fibrosis and tissue remodeling, as well as expression of collagen type VI. Il1rl2-/- mice and mice given injections of an antibody against IL36R developed less severe colitis and fibrosis after administration of DSS or TNBS, but bone marrow cells from Il1rl2-/- mice did not prevent induction of colitis and fibrosis. Injection of antibodies against IL36R significantly reduced established fibrosis in mice with chronic intestinal inflammation.

CONCLUSION

We found higher levels of IL36A in fibrotic intestinal tissues from patients with IBD compared with control individuals. IL36 induced expression of genes that regulate fibrogenesis in fibroblasts. Inhibition or knockout of the IL36R gene in mice reduces chronic colitis and intestinal fibrosis. Agents designed to block IL36R signaling could be developed for prevention and treatment of intestinal fibrosis in patients with IBD.

Colonoscopic-Guided Pinch Biopsies in Mice as a Useful Model for Evaluating the Roles of Host and Luminal Factors in Colonic Inflammation

Colonic inflammation, a hallmark of inflammatory bowel disease, can be influenced by host intrinsic and extrinsic factors. There continues to be a need for models of colonic inflammation that can both provide insights into disease pathogenesis and be used to investigate potential therapies. Herein, we tested the utility of colonoscopic-guided pinch biopsies in mice for studying colonic inflammation and its treatment. Gene expression profiling of colonic wound beds after injury showed marked changes, including increased expression of genes important for the inflammatory response. Interestingly, many of these gene expression changes mimicked those alterations found in inflammatory bowel disease patients. Biopsy-induced inflammation was associated with increases in neutrophils, macrophages, and natural killer cells. Injury also led to elevated levels of sphingosine-1-phosphate (S1P), a bioactive lipid that is an important mediator of inflammation mainly through its receptor, S1P₁. Genetic deletion of S1P₁ in the endothelium did not alter the inflammatory response but led to increased colonic bleeding. Bacteria invaded into the wound beds, raising the possibility that microbes contributed to the observed changes in mucosal gene expression. In support of this, reducing bacterial abundance markedly attenuated the inflammatory response to wounding. Taken together, this study demonstrates the utility of the pinch biopsy model of colonic injury to elucidate the molecular underpinnings of colonic inflammation and its treatment.

Endoscopic submucosal injection of adipose-derived mesenchymal stem cells ameliorates TNBS-induced colitis in rats and prevents stenosis

Background

Mesenchymal stem cells have potential applications in inflammatory bowel disease due to their immunomodulatory properties. Our aim was to evaluate the feasibility, safety and efficacy of endoscopic administration of adipose-derived mesenchymal stem cells (ASCs) in a colitis model in rats.

Methods

Colitis was induced in rats by rectal trinitrobenzenesulfonic acid (TNBS). After 24 h ASCs (10⁷ cells) or saline vehicle were endoscopically injected into the distal colon. Rats were followed for 11 days. Daily weight, endoscopic score at days 1 and 11, macroscopic appearance at necropsy, colon length and mRNA expression of Foxp3 and IL-10 in mesenteric lymph nodes (MLN) were analyzed.

Results

Endoscopic injection was successful in all the animals. No significant adverse events or mortality due to the procedure occurred. Weight evolution was significantly better in the ASC group, recovering initial weight by day 11 (− 0.8% ± 10.1%, mean ± SD), whereas the vehicle group remained in weight loss (− 6.7% ± 9.2%, p = 0.024). The endoscopic score improved in the ASC group by 47.1% ± 5.3% vs. 21.8% ± 6.6% in the vehicle group (p < 0.01). Stenosis was less frequent in the ASC group (4.8% vs. 41.2%, p < 0.01). Colon length significantly recovered in the ASC group versus the vehicle group (222.6 ± 17.3 mm vs. 193.6 ± 17.9 mm, p < 0.001). The endoscopic score significantly correlated with weight change, macroscopic necropsy score and colon length. Foxp3 and IL-10 mRNA levels in MLN recovered with ASC treatment.

Conclusions

ASC submucosal endoscopic injection is feasible, safe and ameliorates TNBS-induced colitis in rats, especially stenosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0837-x) contains supplementary material, which is available to authorized users.

Activation of Epithelial Signal Transducer and Activator of Transcription 1 by Interleukin 28 Controls Mucosal Healing in Mice With Colitis and Is Increased in Mucosa of Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS

We investigated the roles of interleukin 28A (also called IL28A or interferon λ2) in intestinal epithelial cell (IEC) activation, studying its effects in mouse models of inflammatory bowel diseases (IBD) and intestinal mucosal healing.

METHODS

Colitis was induced in C57BL/6JCrl mice (controls), mice with IEC-specific disruption of Stat1 (Stat1IEC-KO), mice with disruption of the interferon λ receptor 1 gene (Il28ra-/-), and mice with disruption of the interferon regulatory factor 3 gene (Irf3-/-), with or without disruption of Irf7 (Irf7-/-). We used high-resolution mini-endoscopy and in vivo imaging methods to assess colitis progression. We used 3-dimensional small intestine and colon organoids, along with RNA-Seq and gene ontology methods, to characterize the effects of IL28 on primary IECs. We studied the effects of IL28 on the human intestinal cancer cell line Caco-2 in a wound-healing assay, and in mice colon wounds. Colonic biopsies and resected tissue from patients with IBD (n = 62) and patients without colon inflammation (controls, n = 23) were analyzed by quantitative polymerase chain rection to measure expression of IL28A, IL28RA, and other related cytokines; biopsy samples were also analyzed by immunofluorescence to identify sources of IL28 production. IECs were isolated from patient tissues and incubated with IL28; signal transducer and activator of transcription 1 (STAT1) phosphorylation was measured by immunoblots and confocal imaging.

RESULTS

Lamina propria cells in colon tissues of patients with IBD, and mice with colitis, had increased expression of IL28 compared with controls; levels of IL28R were increased in the colonic epithelium of patients with IBD and mice with colitis. Administration of IL28 induced phosphorylation of STAT1 in primary human and mouse IECs, increasing with dose. Il28ra-/-, Irf3-/-, Irf3-/-Irf7-/-, as well as Stat1IEC-KO mice, developed more severe colitis after administration of dextran sulfate sodium than control mice, with reduced epithelial restitution. Il28ra-/- and Stat1IEC-KO mice also developed more severe colitis in response to oxazolone than control mice. We found IL28 to induce phosphorylation (activation) of STAT1 in epithelial cells, leading to their proliferation in organoid culture. Administration of IL28 to mice with induced colonic wounds promoted mucosal healing.

CONCLUSIONS

IL28 controls proliferation of IECs in mice with colitis and accelerates mucosal healing by activating STAT1. IL28 might be developed as a therapeutic agent for patients with IBD.

Regression of apoptosis-resistant colorectal tumors by induction of necroptosis in mice

He et al. demonstrate that SMAC mimetic is efficient to target caspase-8–deficient colorectal cancer by induction of necroptosis. This study represents an attractive strategy for overcoming apoptosis resistance in colorectal cancer for the development of more effective personalized therapy.

Cancer cells often acquire capabilities to evade cell death induced by current chemotherapeutic treatment approaches. Caspase-8, a central initiator of death receptor–mediated apoptosis, for example, is frequently inactivated in human cancers via multiple mechanisms such as mutation. Here, we show an approach to overcome cell death resistance in caspase-8–deficient colorectal cancer (CRC) by induction of necroptosis. In both a hereditary and a xenograft mouse model of caspase-8–deficient CRC, second mitochondria-derived activator of caspase (SMAC) mimetic treatment induced massive cell death and led to regression of tumors. We further demonstrate that receptor-interacting protein kinase 3 (RIP3), which is highly expressed in mouse models of CRC and in a subset of human CRC cell lines, is the deciding factor of cancer cell susceptibility to SMAC mimetic–induced necroptosis. Thus, our data implicate that it may be worthwhile to selectively evaluate the efficacy of SMAC mimetic treatment in CRC patients with caspase-8 deficiency in clinical trials for the development of more effective personalized therapy.

VEGFR2 Signaling Prevents Colorectal Cancer Cell Senescence to Promote Tumorigenesis in Mice With Colitis

BACKGROUND & AIMS

Senescence prevents cellular transformation. We investigated whether vascular endothelial growth factor (VEGF) signaling via its receptor, VEGFR2, regulates senescence and proliferation of tumor cells in mice with colitis-associated cancer (CAC).

METHODS

CAC was induced in VEGFR2(ΔIEC) mice, which do not express VEGFR2 in the intestinal epithelium, and VEGFR2(fl/fl) mice (controls) by administration of azoxymethane followed by dextran sodium sulfate. Tumor development and inflammation were determined by endoscopy. Colorectal tissues were collected for immunoblot, immunohistochemical, and quantitative polymerase chain reaction analyses. Findings from mouse tissues were confirmed in human HCT116 colorectal cancer cells. We analyzed colorectal tumor samples from patients before and after treatment with bevacizumab.

RESULTS

After colitis induction, VEGFR2(ΔIEC) mice developed significantly fewer tumors than control mice. A greater number of intestinal tumor cells from VEGFR2(ΔIEC) mice were in senescence than tumor cells from control mice. We found VEGFR2 to activate phosphatidylinositol-4,5-bisphosphate-3-kinase and AKT, resulting in inactivation of p21 in HCT116 cells. Inhibitors of VEGFR2 and AKT induced senescence in HCT116 cells. Tumor cell senescence promoted an anti-tumor immune response by CD8(+) T cells in mice. Patients whose tumor samples showed an increase in the proportion of senescent cells after treatment with bevacizumab had longer progression-free survival than patients in which the proportion of senescent tumor cells did not change before and after treatment.

CONCLUSIONS

Inhibition of VEGFR2 signaling leads to senescence of human and mouse colorectal cancer cells. VEGFR2 interacts with phosphatidylinositol-4,5-bisphosphate-3-kinase and AKT to inactivate p21. Colorectal tumor senescence and p21 level correlate with patient survival during treatment with bevacizumab.

In-vivo monitoring of acute DSS-Colitis using Colonoscopy, high resolution Ultrasound and bench-top Magnetic Resonance Imaging in Mice

OBJECTIVE

The aim of this study was to establish and evaluate (colour Doppler-) high-resolution-ultrasound (hrUS) and bench-top magnetic resonance imaging (btMRI) as new methods to monitor experimental colitis.

MATERIALS AND METHODS

hrUS, btMRI and endoscopy were performed in mice without colitis (n = 15), in mice with acute colitis (n = 14) and in mice with acute colitis and simultaneous treatment with infliximab (n = 19).

RESULTS

Determination of colon wall thickness using hrUS (32 MHz) and measurement of the cross-sectional colonic areas by btMRI allowed discrimination between the treatment groups (mean a vs. b vs. c - btMRI: 922 vs. 2051 vs. 1472 pixel, hrUS: 0.26 vs. 0.45 vs. 0.31 mm). btMRI, endoscopy, hrUS and colour Doppler-hrUS correlated to histological scoring (p < 0.05), while endoscopy and btMRI correlated to post-mortem colon length (p < 0.05).

CONCLUSIONS

The innovative in vivo techniques btMRI and hrUS are safe and technically feasible. They differentiate between distinct grades of colitis in an experimental setting, and correlate with established post-mortem parameters. In addition to endoscopic procedures, these techniques provide information regarding colon wall thickness and perfusion. Depending on the availability of these techniques, their application increases the value of in vivo monitoring in experimental acute colitis in small rodents.

KEY POINTS

• Improved in vivo monitoring might balance interindividual differences in murine colitis. • In monitoring murine colitis, btMRI and hrUS are safe and technically feasible. • Very short examination times underline the usefulness especially of hrUS. • Results of btMRI and hrUS correlate with endoscopic and post-mortem findings.

Activation of intestinal epithelial Stat3 orchestrates tissue defense during gastrointestinal infection

Gastrointestinal infections with EHEC and EPEC are responsible for outbreaks of diarrheal diseases and represent a global health problem. Innate first-line-defense mechanisms such as production of mucus and antimicrobial peptides by intestinal epithelial cells are of utmost importance for host control of gastrointestinal infections. For the first time, we directly demonstrate a critical role for Stat3 activation in intestinal epithelial cells upon infection of mice with Citrobacter rodentium – a murine pathogen that mimics human infections with attaching and effacing Escherichia coli. C. rodentium induced transcription of IL-6 and IL-22 in gut samples of mice and was associated with activation of the transcription factor Stat3 in intestinal epithelial cells. C. rodentium infection induced expression of several antimicrobial peptides such as RegIIIγ and Pla2g2a in the intestine which was critically dependent on Stat3 activation. Consequently, mice with specific deletion of Stat3 in intestinal epithelial cells showed increased susceptibility to C. rodentium infection as indicated by high bacterial load, severe gut inflammation, pronounced intestinal epithelial cell death and dissemination of bacteria to distant organs. Together, our data implicate an essential role for Stat3 activation in intestinal epithelial cells during C. rodentium infection. Stat3 concerts the host response to bacterial infection by controlling bacterial growth and suppression of apoptosis to maintain intestinal epithelial barrier function.

C/EBP homologous protein inhibits tissue repair in response to gut injury and is inversely regulated with chronic inflammation

Loss of intestinal epithelial cell (IEC) homeostasis and apoptosis negatively affect intestinal barrier function. Uncontrolled activation of the unfolded protein response (UPR) in IEC contributes to an impaired barrier and is implicated in the pathogenesis of inflammatory bowel diseases. However, the contribution of the UPR target gene C/EBP homologous protein (CHOP), an apoptosis-associated transcription factor, to inflammation-related disease susceptibility remains unclear. Consistent with observations in patients with ulcerative colitis, we show that despite UPR activation in the epithelium, CHOP expression was reduced in mouse models of T-cell-mediated and bacteria-driven colitis. To elucidate the molecular mechanisms of IEC-specific CHOP expression, we generated a conditional transgenic mouse model (Chop(IEC Tg/Tg)). Chop overexpression increased the susceptibility toward dextran sodium sulfate (DSS)-induced intestinal inflammation and mucosal tissue injury. Furthermore, a delayed recovery from DSS-induced colitis and impaired closure of mechanically induced mucosal wounds was observed. Interestingly, these findings seemed to be independent of CHOP-mediated apoptosis. In vitro and in vivo cell cycle analyses rather indicated a role for CHOP in epithelial cell proliferation. In conclusion, these data show that IEC-specific overexpression impairs epithelial cell proliferation and mucosal tissue regeneration, suggesting an important role for CHOP beyond mediating apoptosis.

Quantitative stain-free and continuous multimodal monitoring of wound healing in vitro with digital holographic microscopy

Impaired epithelial wound healing has significant pathophysiological implications in several conditions including gastrointestinal ulcers, anastomotic leakage and venous or diabetic skin ulcers. Promising drug candidates for accelerating wound closure are commonly evaluated in in vitro wound assays. However, staining procedures and discontinuous monitoring are major drawbacks hampering accurate assessment of wound assays. We therefore investigated digital holographic microscopy (DHM) to appropriately monitor wound healing in vitro and secondly, to provide multimodal quantitative information on morphological and functional cell alterations as well as on motility changes upon cytokine stimulation. Wound closure as reflected by proliferation and migration of Caco-2 cells in wound healing assays was studied and assessed in time-lapse series for 40 h in the presence of stimulating epidermal growth factor (EGF) and inhibiting mitomycin c. Therefore, digital holograms were recorded continuously every thirty minutes. Morphological changes including cell thickness, dry mass and tissue density were analyzed by data from quantitative digital holographic phase microscopy. Stimulation of Caco-2 cells with EGF or mitomycin c resulted in significant morphological changes during wound healing compared to control cells. In conclusion, DHM allows accurate, stain-free and continuous multimodal quantitative monitoring of wound healing in vitro and could be a promising new technique for assessment of wound healing.

Murine endoscopy for in vivo multimodal imaging of carcinogenesis and assessment of intestinal wound healing and inflammation

Mouse models are widely used to study pathogenesis of human diseases and to evaluate diagnostic procedures as well as therapeutic interventions preclinically. However, valid assessment of pathological alterations often requires histological analysis, and when performed ex vivo, necessitates death of the animal. Therefore in conventional experimental settings, intra-individual follow-up examinations are rarely possible. Thus, development of murine endoscopy in live mice enables investigators for the first time to both directly visualize the gastrointestinal mucosa and also repeat the procedure to monitor for alterations. Numerous applications for in vivo murine endoscopy exist, including studying intestinal inflammation or wound healing, obtaining mucosal biopsies repeatedly, and to locally administer diagnostic or therapeutic agents using miniature injection catheters. Most recently, molecular imaging has extended diagnostic imaging modalities allowing specific detection of distinct target molecules using specific photoprobes. In conclusion, murine endoscopy has emerged as a novel cutting-edge technology for diagnostic experimental in vivo imaging and may significantly impact on preclinical research in various fields.

Combination PI3K/MEK inhibition promotes tumor apoptosis and regression in PIK3CA wild-type, KRAS mutant colorectal cancer

PI3K inhibition in combination with other agents has not been studied in the context of PIK3CA wild-type, KRAS mutant cancer. In a screen of phospho-kinases, PI3K inhibition of KRAS mutant colorectal cancer cells activated the MAPK pathway. Combination PI3K/MEK inhibition with NVP-BKM120 and PD-0325901 induced tumor regression in a mouse model of PIK3CA wild-type, KRAS mutant colorectal cancer, which was mediated by inhibition of mTORC1, inhibition of MCL-1, and activation of BIM. These findings implicate mitochondrial-dependent apoptotic mechanisms as determinants for the efficacy of PI3K/MEK inhibition in the treatment of PIK3CA wild-type, KRAS mutant cancer.

Death-associated protein kinase controls STAT3 activity in intestinal epithelial cells

The TNF-IL-6-STAT3 pathway plays a crucial role in promoting ulcerative colitis-associated carcinoma (UCC). To date, the negative regulation of STAT3 is poorly understood. Interestingly, intestinal epithelial cells of UCC in comparison to ulcerative colitis show high expression levels of anti-inflammatory death-associated protein kinase (DAPK) and low levels of pSTAT3. Accordingly, epithelial DAPK expression was enhanced in STAT3(IEC-KO) mice. To unravel a possible regulatory mechanism, we used an in vitro TNF-treated intestinal epithelial cell model. We identified a new function of DAPK in suppressing TNF-induced STAT3 activation as DAPK siRNA knockdown and treatment with a DAPK inhibitor potentiated STAT3 activation, IL-6 mRNA expression, and secretion. DAPK attenuated STAT3 activity directly by physical interaction shown in three-dimensional structural modeling. This model suggests that DAPK-induced conformational changes in the STAT3 dimer masked its nuclear localization signal. Alternatively, pharmacological inactivation of STAT3 led to an increase in DAPK mRNA and protein levels. Chromatin immunoprecipitation showed that STAT3 restricted DAPK expression by promoter binding, thereby reinforcing its own activation by inducing IL-6. This novel negative regulation principle might balance TNF-induced inflammation and seems to play an important role in the inflammation-associated transformation process as confirmed in an AOM+DSS colon carcinogenesis mouse model. DAPK as a negative regulator of STAT3 emerges as therapeutic option in the treatment of ulcerative colitis and UCC.

Tumor fibroblast-derived epiregulin promotes growth of colitis-associated neoplasms through ERK

Molecular mechanisms specific to colitis-associated cancers have been poorly characterized. Using comparative whole-genome expression profiling, we observed differential expression of epiregulin (EREG) in mouse models of colitis-associated, but not sporadic, colorectal cancer. Similarly, EREG expression was significantly upregulated in cohorts of patients with colitis-associated cancer. Furthermore, tumor-associated fibroblasts were identified as a major source of EREG in colitis-associated neoplasms. Functional studies showed that Ereg-deficient mice, although more prone to colitis, were strongly protected from colitis-associated tumors. Serial endoscopic studies revealed that EREG promoted tumor growth rather than initiation. Additionally, we demonstrated that fibroblast-derived EREG requires ERK activation to induce proliferation of intestinal epithelial cells (IEC) and tumor development in vivo. To demonstrate the functional relevance of EREG-producing tumor-associated fibroblasts, we developed a novel system for adoptive transfer of these cells via mini-endoscopic local injection. It was found that transfer of EREG-producing, but not Ereg-deficient, fibroblasts from tumors significantly augmented growth of colitis-associated neoplasms in vivo. In conclusion, our data indicate that EREG and tumor-associated fibroblasts play a crucial role in controlling tumor growth in colitis-associated neoplasms.

Lack of intestinal epithelial atg7 affects paneth cell granule formation but does not compromise immune homeostasis in the gut

Genetic polymorphisms of autophagy-related genes have been associated with an increased risk to develop inflammatory bowel disease (IBD). Autophagy is an elementary process participating in several cellular events such as cellular clearance and nonapoptotic programmed cell death. Furthermore, autophagy may be involved in intestinal immune homeostasis due to its participation in the digestion of intracellular pathogens and in antigen presentation. In the present study, the role of autophagy in the intestinal epithelial layer was investigated. The intestinal epithelium is essential to maintain gut homeostasis, and defects within this barrier have been associated with the pathogenesis of IBD. Therefore, mice with intestinal epithelial deletion of Atg7 were generated and investigated in different mouse models. Knockout mice showed reduced size of granules and decreased levels of lysozyme in Paneth cells. However, this was dispensable for gut immune homeostasis and had no effect on susceptibility in mouse models of experimentally induced colitis.

Utilization of murine colonoscopy for orthotopic implantation of colorectal cancer

Background

Colorectal-cancer (CRC) research has greatly benefited from the availability of small animal tumor models. Spontaneous and chemically-induced CRC models are widely used yet limited in their resemblance to human disease and are often prolonged, not accurately repetitive, and associated with inflammatory side effects. In-situ murine or human tumor implantation in the gastrointestinal tract of mice is extremely challenging, and limited by inter-animal variability and procedure-related complications and mortality. As a result, in frequent studies CRC is implanted in distal sites, most commonly the subcutaneous region, an approach that is greatly limited by the absence of normal gastrointestinal tumor milieu and has substantial effects on tumor development.

Aims

In this study we aimed to develop a well-tolerated repetitive tool to study CRC in small animals by adapting the murine colonoscopy system to serve as a platform for colonic sub-mucosal orthotopic implantation of human and murine CRC tumor cells.

Results

We report the establishment of a novel small-animal CRC model that is minimally invasive, rapid, well-tolerated, highly reproducible, and confers precise control of tumor number, location and growth rate. Moreover, we show that this model uniquely allows the side-by-side induction of distinct genetically manipulated tumors, enabling the mechanistic study of tumor interaction and cross-talk within the native intestinal microenvironment.

Conclusions

Employment of this new approach may represent a major technical advance for the in-vivo study of CRC.

The mammalian intestinal epithelium as integral player in the establishment and maintenance of host-microbial homeostasis

Only one single layer of epithelial cells separates the densely colonized and environmentally exposed intestinal lumen from the largely sterile subepithelial tissue. Together with the overlaying mucus and the subepithelial mucosal immune system the epithelium has evolved to maintain homeostasis in the presence of the enteric microbiota. It also contributes to rapid and efficient antimicrobial host defence in the event of infection with pathogenic microorganisms. Both, epithelial antimicrobial host defence and homeostasis rely on signalling pathways induced by innate immune receptors demonstrating the active role of epithelial cells in the host-microbial interplay. The interaction of epithelial cells with professional immune cells illustrates the integrated function within the mucosal tissue. In the present review we focus on structural and functional changes of the intestinal epithelium during the fetal-neonatal transition and infancy and try to delineate its role in the induction and maintenance of host-microbial homeostasis. We also address factors that impair epithelial functions and may lead to disruption of the mucosal barrier, tissue damage and the development of symptomatic disease.