Myofibroblasts. II. Intestinal subepithelial myofibroblasts

Prognostic Impact of Stromal Profiles Educated by Gastric Cancer

BACKGROUND

Cancer-associated fibroblasts exhibit diversity and have several subtypes. The underlying relationship between the diversity of cancer-associated fibroblasts and their effect on gastric cancer progression remains unclear. In this study, mesenchymal stem cells were differentiated into cancer-associated fibroblasts with gastric cancer cell lines; clinical specimens were used to further investigate the impact of cancer-associated fibroblast diversity on cancer progression.

METHODS

Nine gastric cancer cell lines (NUGC3, NUGC4, MKN7, MKN45, MKN74, FU97, OCUM1, NCI-N87, and KATOIII) were used to induce mesenchymal stem cell differentiation into cancer-associated fibroblasts. The cancer-associated fibroblasts were classified based on ACTA2 and PDPN expression. Cell function analysis was used to examine the impact of cancer-associated fibroblast subtypes on cancer cell phenotype. Tissue samples from 97gastric patients who underwent gastrectomy were used to examine the clinical significance of each subtype classified according to cancer-associated fibroblast expression.

RESULTS

Co-culture of mesenchymal stem cells with nine gastric cancer cell lines revealed different subtypes of ACTA2 and PDPN expression in differentiated cancer-associated fibroblasts. Cancer-associated fibroblast subtypes with high ACTA2 plus PDPN expression levels significantly increased gastric cancer cell migration, invasion, and proliferation. The cancer-associated fibroblast subtype with ACTA2 plus PDPN expression was an independent prognostic factor along with lymph node metastasis for patients who had gastric cancer and were undergoing surgery.

CONCLUSIONS

Cancer-associated fibroblasts are educated by gastric cancer cells during the development of cancer-associated fibroblast diversity. Differentiated cancer-associated fibroblasts with distinct expression patterns could affect gastric cancer progression and enable prognostic stratification for gastric cancer.

Colorectal Cancer-Associated Myofibroblasts Exhibit Enhanced Angiogenin Expression and Signaling via the PLXNB2 Receptor

INTRODUCTION

Dynamic cell-cell interactions shape the tumor microenvironment to regulate tumor growth and invasiveness. Myofibroblasts are gastrointestinal stromal cells that are upregulated in the setting of colorectal cancer (CRC) and may play an important role in tumor-stromal cell communication. Angiogenin is a 14-kDa ribonuclease that regulates myofibroblast function and has been implicated in myofibroblast-CRC cell communication in mouse models. However, its role in human patients has not been well established.

METHODS

Open access, annotated single-cell RNA sequencing data of paired normal human colon and CRC tissue were available in the National Center for Biotechnology Information Gene Expression Omnibus Database. We supplemented and verified these data by analyzing scRNA-seq data from an independent set of paired normal human colon and CRC tissue. CellChat was used to quantitatively infer biologically meaningful cell-cell communication networks from scRNA-seq data. PLXNB2 and α-2 actin (ACTA2) are cell surface angiogenin receptors that regulate angiogenin signaling. Ligand-receptor interactions involving angiogenin, PLXNB2, and ACTA2 were analyzed between cell populations in each sample.

RESULTS

We found no difference in overall angiogenin expression comparing normal colon and CRC tissue. In normal colon tissue, myofibroblasts do not express angiogenin or the PLXNB2 receptor. In the presence of CRC, there was a striking increase in the number of myofibroblast cells within the surrounding stroma. CRC-associated myofibroblasts were characterized by a significant upregulation of both angiogenin and PLXNB2 receptor expression (P < 0.05), while no difference was seen in ACTA2. CRC cells not only use angiogenin for autocrine signaling but also communicate with myofibroblasts via the PLXNB2 receptor.

CONCLUSIONS

Compared to normal human colon tissue, CRC tissue is associated with an enrichment of myofibroblasts that exhibit upregulated expression of angiogenin and the angiogenin receptor PLXNB2. CRC cells engage in autocrine signaling via angiogenin and paracrine signaling with myofibroblasts via PLXNB2. Angiogenin appears to be directly involved in tumor-stromal cell communication in human CRC tissue and may play an important role in disease progression.

Towards Full Thickness Small Intestinal Models: Incorporation of Stromal Cells

INTRODUCTION

Since small intestine is one of the major barriers of the human body, there is a need to develop reliable in vitro human small intestinal models. These models should incorporate both the epithelial and lamina propria compartments and have similar barrier properties compared to that of the human tissue. These properties are essential for various applications, such as studying cell-cell interaction, intestinal diseases and testing permeability and metabolism of drugs and other compounds. The small intestinal lamina propria contains multiple stromal cell populations with several important functions, such as secretion of extracellular matrix proteins and soluble mediators. In addition, stromal cells influence the intestinal epithelial barrier, support the intestinal stem cell niche and interact with immune cells.

METHODS

In this review, we provide an extensive overview on the different types of lamina propria stromal cells found in small intestine and describe a combination of molecular markers that can be used to distinguish each different stromal cell type. We focus on studies that incorporated stromal cells into human representative small intestine models cultured on transwells.

RESULTS AND CONCLUSION

These models display enhanced epithelial morphology, increased cell proliferation and human-like barrier properties, such as low transepithelial electrical resistance (TEER) and intermediate permeability, thus better mimicking the native human small intestine than models only consisting of an epithelium which generally show high TEER and low permeability.

Human intestinal organoid-derived PDGFRα + mesenchymal stroma enables proliferation and maintenance of LGR4 + epithelial stem cells

BACKGROUND

Intestinal epithelial cells derived from human pluripotent stem cells (hPSCs) are generally maintained and cultured as organoids in vitro because they do not exhibit adhesion when cultured. However, the three-dimensional structure of organoids makes their use in regenerative medicine and drug discovery difficult. Mesenchymal stromal cells are found near intestinal stem cells in vivo and provide trophic factors to regulate stem cell maintenance and proliferation, such as BMP inhibitors, WNT, and R-spondin. In this study, we aimed to use mesenchymal stromal cells isolated from hPSC-derived intestinal organoids to establish an in vitro culture system that enables stable proliferation and maintenance of hPSC-derived intestinal epithelial cells in adhesion culture.

METHODS

We established an isolation protocol for intestinal epithelial cells and mesenchymal stromal cells from hPSCs-derived intestinal organoids and a co-culture system for these cells. We then evaluated the intestinal epithelial cells and mesenchymal stromal cells' morphology, proliferative capacity, chromosomal stability, tumorigenicity, and gene expression profiles. We also evaluated the usefulness of the cells for pharmacokinetic and toxicity studies.

RESULTS

The proliferating intestinal epithelial cells exhibited a columnar form, microvilli and glycocalyx formation, cell polarity, and expression of drug-metabolizing enzymes and transporters. The intestinal epithelial cells also showed barrier function, transporter activity, and drug-metabolizing capacity. Notably, small intestinal epithelial stem cells cannot be cultured in adherent culture without mesenchymal stromal cells and cannot replaced by other feeder cells. Organoid-derived mesenchymal stromal cells resemble the trophocytes essential for maintaining small intestinal epithelial stem cells and play a crucial role in adherent culture.

CONCLUSIONS

The high proliferative expansion, productivity, and functionality of hPSC-derived intestinal epithelial cells may have potential applications in pharmacokinetic and toxicity studies and regenerative medicine.

Downregulation of Heat Shock Protein 72 Contributes to Fibrostenosis in Crohn's Disease

Background/Aims

Crohn's disease (CD) with recurrent inflammation can cause intestinal fibrostenosis due to dysregulated deposition of extracellular matrix. However, little is known about the pathogenesis of fibrostenosis. Here, we performed a differential proteomic analysis between normal, inflamed, and fibrostenotic specimens of patients with CD and investigated the roles of the candidate proteins in myofibroblast activation and fibrosis.

Methods

We performed two-dimensional difference gel electrophoresis and identified candidate proteins using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and orbitrap liquid chromatography-mass spectrometry. We also verified the levels of candidate proteins in clinical specimens and examined their effects on 18Co myofibroblasts and Caco-2 intestinal epithelial cells.

Results

We identified five of 30 proteins (HSP72, HSPA5, KRT8, PEPCK-M, and FABP6) differentially expressed in fibrostenotic CD. Among these proteins, the knockdown of heat shock protein 72 (HSP72) promoted the activation and wound healing of myofibroblasts. Moreover, knockdown of HSP72 induced the epithelial-mesenchymal transition of intestinal epithelial cells by reducing E-cadherin and inducing fibronectin and α-smooth muscle actin, which contribute to fibrosis.

Conclusions

HSP72 is an important mediator that regulates myofibroblasts and epithelial-mesenchymal transition in fibrosis of CD, suggesting that HSP72 can serve as a target for antifibrotic therapy.

In Vivo Regeneration of Tubular Small Intestine With Motility: A Novel Approach by Orthotopic Transplantation of Decellularized Scaffold

BACKGROUND

Whole-intestine engineering can provide a therapeutic alternative to bowel transplantation. Intestinal components including the mucosa, muscular layer, enteric nervous system, and vasculature must be reestablished as a tubular organ to generate an artificial small intestine. This study proposes a novel approach to produce a transplantable, well-organized tubular small intestine using a decellularized scaffold.

METHODS

Male Lewis rat intestines were used to generate decellularized scaffolds. Patch or tubular grafts were prepared from the decellularized intestine and transplanted into the rat intestine orthotopically. Histological analysis of the decellularized intestine was performed up to 12 wk after transplantation.

RESULTS

Histological examination revealed abundant vascularization into the decellularized patch graft 1 wk after transplantation. Muscular and nervous components, as well as cryptogenesis, were observed in the decellularized patch graft 2 wk after transplantation. Sixteen of the 18 rats survived with normal intake of food and water after the decellularized tubular graft transplantation. Compared with silicone tube grafts, the decellularized tubular grafts significantly promoted the infiltration and growth of intestinal components including the mucosa, muscular layer, and nerve plexus from the recipients. Circular and longitudinal muscle with a well-developed myenteric plexus was regenerated, and intestinal motility was confirmed in the decellularized tubular graft 12 wk after transplantation.

CONCLUSIONS

Orthotopic transplantation of decellularized intestine enhanced the reconstruction of the well-organized tubular small intestine with an enteric nervous system in vivo. Our method using a decellularized scaffold represents a promising approach toward whole-intestine engineering and provides a therapeutic alternative for the irreversible intestinal failure.

Alternative splicing of CEACAM1 by hypoxia-inducible factor-1α enhances tolerance to hepatic ischemia in mice and humans

Although alternative splicing (AS) drives transcriptional responses and cellular adaptation to environmental stresses, its contributions in organ transplantation have not been appreciated. We have shown that carcinoembryonic antigen-related cell adhesion molecule (Ceacam1; CD66a), a transmembrane biliary glycoprotein expressed in epithelial, endothelial, and immune cells, determines donor liver transplant quality. Here, we studied how AS of Ceacam1 affects ischemia-reperfusion injury (IRI) in mouse and human livers. We found that the short cytoplasmic isoform Ceacam1-S increased during early acute and late resolution phases of warm IRI injury in mice. Transfection of Ceacam1-deficient mouse hepatocytes with adenoviral Ceacam1-S mitigated hypoxia-induced loss of cellular adhesion by repressing the Ask1/p-p38 cell death pathway. Nucleic acid-blocking morpholinos, designed to selectively induce Ceacam1-S, protected hepatocyte cultures against temperature-induced stress in vitro. Luciferase and chromatin immunoprecipitation assays identified direct binding of hypoxia-inducible factor-1α (Hif-1α) to the mouse polypyrimidine tract binding protein 1 (Ptbp1) promoter region. Dimethyloxalylglycine protected mouse livers from warm IR stress and hepatocellular damage by inhibiting prolyl hydroxylase domain-containing protein 1 and promoting AS of Ceacam1-S. Last, analysis of 46 human donor liver grafts revealed that CEACAM1-S positively correlated with pretransplant HIF1A expression. This also correlated with better transplant outcomes, including reduced TIMP1, total bilirubin, proinflammatory MCP1, CXCL10 cytokines, immune activation markers IL17A, and incidence of delayed complications from biliary anastomosis. This translational study identified mouse Hif-1α-controlled AS of Ceacam1, through transcriptional regulation of Ptbp1 promoter region, as a functional underpinning of hepatoprotection against IR stress and tissue damage in liver transplantation.

Loss of alcohol dehydrogenase 1B in cancer-associated fibroblasts: contribution to the increase of tumor-promoting IL-6 in colon cancer

BACKGROUND

Increases in IL-6 by cancer-associated fibroblasts (CAFs) contribute to colon cancer progression, but the mechanisms involved in the increase of this tumor-promoting cytokine are unknown. The aim of this study was to identify novel targets involved in the dysregulation of IL-6 expression by CAFs in colon cancer.

METHODS

Colonic normal (N), hyperplastic, tubular adenoma, adenocarcinoma tissues, and tissue-derived myo-/fibroblasts (MFs) were used in these studies.

RESULTS

Transcriptomic analysis demonstrated a striking decrease in alcohol dehydrogenase 1B (ADH1B) expression, a gene potentially involved in IL-6 dysregulation in CAFs. ADH1B expression was downregulated in approximately 50% of studied tubular adenomas and all T1-4 colon tumors, but not in hyperplastic polyps. ADH1B metabolizes alcohols, including retinol (RO), and is involved in the generation of all-trans retinoic acid (atRA). LPS-induced IL-6 production was inhibited by either RO or its byproduct atRA in N-MFs, but only atRA was effective in CAFs. Silencing ADH1B in N-MFs significantly upregulated LPS-induced IL-6 similar to those observed in CAFs and lead to the loss of RO inhibitory effect on inducible IL-6 expression.

CONCLUSION

Our data identify ADH1B as a novel potential mesenchymal tumor suppressor, which plays a critical role in ADH1B/retinoid-mediated regulation of tumor-promoting IL-6.

Thrombin Induced Apoptosis through Calcium-Mediated Activation of Cytosolic Phospholipase A2 in Intestinal Myofibroblasts

Thrombin is a serine protease that participates in a variety of biological signaling through protease-activated receptors. Intestinal myofibroblasts play central roles in maintaining intestinal homeostasis. In this study, we found that thrombin-induced apoptosis is mediated by the calcium-mediated activation of cytosolic phospholipase A₂ in the CCD-18Co cell. Thrombin reduced cell viability by inducing apoptosis and proteinase-activated receptor-1 antagonist attenuated thrombin-induced cell death. Endogenous ceramide did not affect the cell viability itself, but a ceramide-mediated pathway was involved in thrombin-induced cell death. Thrombin increased intracellular calcium levels and cytosolic phospholipase A₂ activity. The ceramide synthase inhibitor Fumonisin B₁, intracellular calcium chelator BAPTA-AM, and cytosolic phospholipase A₂ inhibitor AACOCF₃ inhibited thrombin-induced cell death. Thrombin stimulated arachidonic acid release and reactive oxygen species generation, which was blocked by AACOCF₃, BAPTA-AM, and the antioxidant reagent Trolox. Taken together, thrombin triggered apoptosis through calcium-mediated activation of cytosolic phospholipase A₂ in intestinal myofibroblasts.

Gut homeostasis at a glance

The intestine, a rapidly self-renewing organ, is part of the gastrointestinal system. Its major roles are to absorb food-derived nutrients and water, process waste and act as a barrier against potentially harmful substances. Here, we will give a brief overview of the primary functions of the intestine, its structure and the luminal gradients along its length. We will discuss the dynamics of the intestinal epithelium, its turnover, and the maintenance of homeostasis. Finally, we will focus on the characteristics and functions of intestinal mesenchymal and immune cells. In this Cell Science at a Glance article and the accompanying poster, we aim to present the most recent information about gut cell biology and physiology, providing a resource for further exploration.

Region specificity of fibroblast-like cells in the mucosa of the rat large intestine

Our previous studies using immunohistochemistry and serial block-face scanning electron microscopy (SBF-SEM) clarified that fibroblast-like cells (FBLCs) in the rat ileal mucosa are classifiable into several subtypes, but their characteristics throughout the large intestine remain unknown. In this study, we investigated the region-specific characteristics of FBLCs in the rat large intestine using histological analysis including SBF-SEM. Immunohistochemistry revealed that CD34⁺CD31^- FBLCs were localized in the lamina propria beneath the crypt bases throughout the large intestine and were more abundant in the descending colon than in the other regions. In addition, platelet-derived growth factor receptor α (PDGFRα)⁺ FBLCs were ubiquitously present just below the epithelium throughout the large intestine, and those at the crypt base were slightly more abundant in the descending colon than in the other regions. SBF-SEM analysis revealed that there were two types of FBLCs around the crypt base in both the cecum and the descending colon: sub-epithelial FBLCs localizing just beneath the epithelium in the manner of PDGFRα⁺ FBLCs, and lamina propria FBLCs localizing farther away from the epithelium than sub-epithelial FBLCs in the manner of CD34⁺CD31^- FBLCs. The lamina propria FBLCs were closely apposed to various immune cells in the lamina propria, and their endoplasmic reticulum in the descending colon exhibited various dilatation levels, unlike that in the cecum. These findings indicate that FBLCs, especially around the crypt base, differed in each region of the large intestine with respect to localization, abundance, and ultrastructure, which could lead to the region-specific microenvironment around the crypt base.

From the intestinal mucosal barrier to the enteric neuromuscular compartment: an integrated overview on the morphological changes in Parkinson's disease

Gastrointestinal dysfunctions represent the most common non-motor symptoms in Parkinson’s disease (PD). Of note, changes in gut microbiota, impairments of intestinal epithelial barrier (IEB), bowel inflammation and neuroplastic rearrangements of the enteric nervous system (ENS) could be involved in the pathophysiology of the intestinal disturbances in PD. In this context, although several review articles have pooled together evidence on the alterations of enteric bacteria-neuro-immune network in PD, a revision of the literature on the specific morphological changes occurring in the intestinal mucosal barrier, the ENS and enteric muscular layers in PD, is lacking. The present review provides a complete appraisal of the available knowledge on the morphological alterations of intestinal mucosal barrier, with particular focus on IEB, ENS and enteric muscular layers in PD. In particular, our intent was to critically discuss whether, based on evidence from translational studies and preclinical models, morphological changes in the intestinal barrier and enteric neuromuscular compartment contribute to the pathophysiology of intestinal dysfunctions occurring in PD.

Multitargeting Effects of Calebin A on Malignancy of CRC Cells in Multicellular Tumor Microenvironment

Background

Tumor microenvironment (TME) provides the essential prerequisite niche for promoting cancer progression and metastasis. Calebin A, a component of Curcuma longa, has long been investigated as a safe multitargeted agent with antitumor and anti-inflammatory properties. However, the multicellular-TME-induced malignancy and the antitumorigenic potential of Calebin A on colorectal cancer (CRC) cells in 3D-alginate cultures are not yet understood, and more in-depth research is needed.

Methods

3D-alginate tumor cultures (HCT116 cells) in the multicellular proinflammatory TME (fibroblast cells/T lymphocytes), tumor necrosis factor beta (TNF-β)-TME (fibroblast cells/TNF-β) were treated with/without Calebin A to address the pleiotropic actions of Calebin A in the CRC.

Results

We found that Calebin A downmodulated proliferation, vitality, and migration of HCT116 cells in 3D-alginate cultures in multicellular proinflammatory TME or TNF-β-TME. In addition, Calebin A suppressed TNF-β-, similar to multicellular-TME-induced phosphorylation of nuclear factor kappa B (NF-κB) in a concentration-dependent manner. NF-κB-promoting proinflammatory mediators, associated with tumor growth and antiapoptotic molecules (i.e.,MMP-9, CXCR4, Ki-67, β1-integrin, and Caspase-3) and its translocation to the nucleus in HCT116 cells, were increased in both TME cultures. The multicellular-TME cultures further induced the survival of cancer stem cells (CSCs) (upregulation of CD133, CD44, and ALDH1). Last but not the least, Calebin A suppressed multicellular-, similar to TNF-β-TME-induced rigorous upregulation of NF-κB phosphorylation, various NF-κB-regulated gene products, CSCs activation, and survival in 3D-alginate tumor cultures.

Conclusions

The downmodulation of multicellular proinflammatory-, similar to TNF-β-TME-induced CRC proliferation, survival, and migration by the multitargeting agent Calebin A could be a new therapeutic strategy to suppress inflammation and CRC tumorigenesis.

Intestinal mesenchymal cells regulate immune responses and promote epithelial regeneration in vitro and in dextran sulfate sodium-induced experimental colitis in mice

AIM

Disruption of the intestinal mucosal tolerance, that is, the immunological unresponsiveness to innocuous food antigens and the commensal microbiota, in the colon is associated with several chronic diseases including inflammatory bowel disease (IBD). Understanding the mechanisms responsible for intestinal mucosal tolerance has potential translational value for its therapy and management. Human intestinal mesenchymal cells (iMCs) play important roles in colonic mucosal tolerance, but further studies on their tissue regenerative and immunomodulatory capacities are necessary in order to fully understand their function in health and disease.

METHODS

In this study, we have isolated and analysed the capacity of human iMCs to promote wound healing and modulate immune responses in vitro and in vivo, using the dextran sulfate sodium (DSS)-induced colitis model.

RESULTS

Cultured iMCs were CD45^- CD73⁺ CD90⁺ CD105⁺ and accelerated the wound closure in a normal colon mucosa (NCM) 356 human epithelial cell wound healing assay. Furthermore, iMCs blocked the LPS-mediated induction of TNF-α in THP-1 macrophages and inhibited the proliferation of peripheral blood mononuclear cells, partly through the induction of indoleamine-2,3-dioxygenase. In DSS colitic mice, iMCs administration reduced the disease activity index and ameliorated intestinal tissue damage and permeability. Furthermore, iMCs reduced intestinal inflammation, evidenced by a decreased mRNA expression of pro-inflammatory cytokines, reduced IL-1β secretion by intestinal explants and inhibited colonic iNOS protein expression.

CONCLUSIONS

Our data show that human iMCs isolated from the noninflamed intestine possess tissue-regenerative and immunomodulatory capacities that could potentially be harnessed/restored in order to reduce IBD severity.

Pathogenesis and management of gastrointestinal inflammation and fibrosis: from inflammatory bowel diseases to endoscopic surgery

Gastrointestinal fibrosis is a state of accumulated biological entropy caused by a dysregulated tissue repair response. Acute or chronic inflammation in the gastrointestinal tract, including inflammatory bowel disease, particularly Crohn’s disease, induces fibrosis and strictures, which often require surgical or endoscopic intervention. Recent technical advances in endoscopic surgical techniques raise the possibility of gastrointestinal stricture after an extended resection. Compared to recent progress in controlling inflammation, our understanding of the pathogenesis of gastrointestinal fibrosis is limited, which requires the development of prevention and treatment strategies. Here, we focus on gastrointestinal fibrosis in Crohn’s disease and post-endoscopic submucosal dissection (ESD) stricture, and we review the relevant literature.

Elimination of NF-κB signaling in Vimentin+ stromal cells attenuates tumorigenesis in a mouse model of Barrett's Esophagus

Chronic inflammation induces Barrett's Esophagus (BE) which can advance to esophageal adenocarcinoma. Elevated levels of interleukin (IL)-1b, IL-6 and IL-8 together with activated nuclear factor-kappaB (NF-κB), have been identified as important mediators of tumorigenesis. The inflammatory milieu apart from cancer cells and infiltrating immune cells contains myofibroblasts (MFs) that express aSMA and Vimentin. As we observed that increased NF-κB activation and inflammation correlates with increased MF recruitment and an accelerated phenotype we here analyze the role of NF-κB in MF during esophageal carcinogenesis in our L2-IL-1B mouse model. To analyze the effect of NF-κB signaling in MFs, we crossed L2-IL-1B mice to tamoxifen inducible Vim-Cre (Vim-CreTm) mice and floxed RelA (p65fl/fl) mice to specifically eliminate NF-κB signaling in MF (IL-1b.Vim-CreTm.p65fl/fl). The interaction of epithelial cells and stromal cells was further analyzed in mouse BE organoids and patient-derived human organoids. Histological scoring of IL-1b.Vim-CreTm.p65fl/fl mice showed a significantly attenuated phenotype compared with L2-IL-1B mice, with mild inflammation, decreased metaplasia and no dysplasia. This correlated with decreased proliferation and increased differentiation in cardia tissue of IL-1b.Vim-CreTm.p65fl/fl compared with L2-IL-1B mice. Distinct changes of cytokines and chemokines within the local microenvironment in IL-1b.Vim-CreTm.p65fl/fl mice reflected the histopathological abrogated phenotype. Co-cultured NF-κB inhibitor treated MF with mouse BE organoids demonstrated NF-κB-dependent growth and migration. MFs are essential to form an inflammatory and procarcinogenic microenvironment and NF-κB signaling in stromal cells emerges as an important driver of esophageal carcinogenesis. Our data suggest anti-inflammatory approaches as preventive strategies during surveillance of BE patients.

[Corneal wound healing-Pathophysiology and principles]

The cornea forms the anterior border of the eye and significantly contributes to a sharp optical image quality on the retina through its transparency, avascular nature and curvature. Because of its anatomical structure and as a barrier to the environment, the cornea is particularly exposed to various external factors, such as injuries and pathogens. A correct wound healing without the formation of light diverging scarring is therefore essential to preserve the integrity and function of the cornea. Misguided wound healing is of outstanding clinical relevance and can lead to corneal fibrogenesis. Corneal fibrosis results in scarring with a loss of optical transparency, which significantly reduces eyesight and can lead to blindness. Understanding the pathophysiological mechanisms of wound healing and fibrogenesis is of great importance for the diagnostics, treatment and evaluation of the subsequent healing process in order to prevent permanent damage as far as possible.

AXL Is a Potential Target for the Treatment of Intestinal Fibrosis

BACKGROUND

Fibrosis is the final common pathway to intestinal failure in Crohn's disease, but no medical therapies exist to treat intestinal fibrosis. Activated myofibroblasts are key effector cells of fibrosis in multiple organ systems, including the intestine. AXL is a receptor tyrosine kinase that has been implicated in fibrogenic pathways involving myofibroblast activation. We aimed to investigate the AXL pathway as a potential target for the treatment of intestinal fibrosis.

METHODS

To establish proof of concept, we first analyzed AXL gene expression in 2 in vivo models of intestinal fibrosis and 3 in vitro models of intestinal fibrosis. We then tested whether pharmacological inhibition of AXL signaling could reduce fibrogenesis in 3 in vitro models of intestinal fibrosis. In vitro testing included 2 distinct cell culture models of intestinal fibrosis (matrix stiffness and TGF-β1 treatment) and a human intestinal organoid model using TGF-β1 cytokine stimulation.

RESULTS

Our findings suggest that the AXL pathway is induced in models of intestinal fibrosis. We demonstrate that inhibition of AXL signaling with the small molecule inhibitor BGB324 abrogates both matrix-stiffness and transforming growth factor beta (TGF-β1)-induced fibrogenesis in human colonic myofibroblasts. AXL inhibition with BGB324 sensitizes myofibroblasts to apoptosis. Finally, AXL inhibition with BGB324 blocks TGF-β1-induced fibrogenic gene and protein expression in human intestinal organoids.

CONCLUSIONS

The AXL pathway is active in multiple models of intestinal fibrosis. In vitro experiments suggest that inhibiting AXL signaling could represent a novel approach to antifibrotic therapy for intestinal fibrosis such as in Crohn's disease.

Developing an advanced gut on chip model enabling the study of epithelial cell/fibroblast interactions

Organoids are widely used as a model system to study gut pathophysiology; however, they fail to fully reproduce the complex, multi-component structure of the intestinal wall. We present here a new gut on chip model that allows the co-culture of primary epithelial and stromal cells. The device has the topography and dimensions of the mouse gut and is based on a 3D collagen I scaffold. The scaffold is coated with a thin layer of laminin to mimic the basement membrane. To maintain the scaffold structure while preserving its cytocompatibility, the collagen scaffold was rigidified by threose-based post-polymerization treatment. This treatment being cytocompatible enabled the incorporation of primary intestinal fibroblasts inside the scaffold, reproducing the gut stromal compartment. We observed that mouse organoids, when deposited into crypts, opened up and epithelialized the scaffold, generating a polarized epithelial monolayer. Proper segregation of dividing and differentiated cells along the crypt-villus axis was achieved under these conditions. Finally, we show that the application of fluid shear stress allows the long-term culture of this intestinal epithelium. Our device represents a new biomimetic tool that captures key features of the gut complexity and could be used to study gut pathophysiology.

Mast Cell Tryptase Promotes Inflammatory Bowel Disease-Induced Intestinal Fibrosis

BACKGROUND

Intestinal fibrosis is the final pathological outcome of chronic intestinal inflammation without specific therapeutic drugs, which leads to ileus and surgical intervention. Intestinal fibrosis is characterized by excessive deposition of extracellular matrix (ECM). The role of mast cells (MCs), which are members of the sentinel immune cell population, is unknown in intestinal fibrosis.

METHODS

In this study, we analyzed changes in MCs, tryptase proteins, and ECM components in human fibrotic and control patient intestines. We constructed dextran sodium sulfate-induced intestinal fibrosis models using wild-type mice, MC-reconstituted mice, and MC-deficient mice to explore the role of MCs and tryptase in intestinal fibrosis. The roles and mechanisms of MCs and tryptase on fibroblasts were evaluated using human MCs (HMC-1 and LAD-2), commercial tryptase proteins, human colon fibroblasts (CCD-18Co fibroblasts), the tryptase inhibitor APC366, and the protease-activated receptor-2 (PAR-2) antagonist ENMD-1068.

RESULTS

Regardless of whether the colon was a human colon or a mouse colon, the fibrotic intestinal tissue had increased MC infiltration and a higher expression of ECM proteins or genes than that of the control group. The dextran sodium sulfate-induced intestinal fibrosis in MC-deficient mice was alleviated compared with that in wild-type mice. After MC reconstruction in MC-deficient mice, the alleviating effect disappeared. Tryptase, as a content stored in MC granules, was released into fibrotic intestinal tissues in the form of degranulation, resulting in an increased expression of tryptase. Compared with the control group, the tryptase inhibition group (the APC366 group) had reduced intestinal fibrosis. The CCD-18Co fibroblasts, when cocultured with MCs or treated with tryptase proteins, were activated to differentiate into myofibroblasts and secrete more ECM proteins (such as collagen and fibronectin). The underlying mechanism of fibroblast activation by tryptase was the activation of the PAR-2/Akt/mTOR pathway.

CONCLUSIONS

We found that MC tryptase promotes inflammatory bowel disease-induced intestinal fibrosis. The underlying mechanism is that tryptase promotes the differentiation of fibroblasts into fibrotic-phenotype myofibroblasts by activating the PAR-2/Akt/ mTOR pathway of fibroblasts.

Fibroblast Subsets in Intestinal Homeostasis, Carcinogenesis, Tumor Progression, and Metastasis

Simple Summary

Colorectal cancer often develops via the adenoma–carcinoma sequence, a process which is accompanied by (epi) genetic alterations in epithelial cells and gradual phenotypic changes in fibroblast populations. Recent studies have made it clear that these fibroblast populations which, in the context of invasive cancers are termed cancer-associated fibroblasts (CAFs), play an important role in intestinal tumor progression. This review provides an overview on the emerging role of fibroblasts in various stages of colorectal cancer development, ranging from adenoma initiation to metastatic spread of tumor cells. As fibroblasts show considerable heterogeneity in subsets and phenotypes during cancer development, a better functional understanding of stage-specific (alterations in) fibroblast/CAF populations is key to increase the effectiveness of fibroblast-based prognosticators and therapies.

Abstract

In intestinal homeostasis, continuous renewal of the epithelium is crucial to withstand the plethora of stimuli which can damage the structural integrity of the intestines. Fibroblasts contribute to this renewal by facilitating epithelial cell differentiation as well as providing the structural framework in which epithelial cells can regenerate. Upon dysregulation of intestinal homeostasis, (pre-) malignant neoplasms develop, a process which is accompanied by (epi) genetic alterations in epithelial cells as well as phenotypic changes in fibroblast populations. In the context of invasive carcinomas, these fibroblast populations are termed cancer-associated fibroblasts (CAFs). CAFs are the most abundant cell type in the tumor microenvironment of colorectal cancer (CRC) and consist of various functionally heterogeneous subsets which can promote or restrain cancer progression. Although most previous research has focused on the biology of epithelial cells, accumulating evidence shows that certain fibroblast subsets can also importantly contribute to tumor initiation and progression, thereby possibly providing avenues for improvement of clinical care for CRC patients. In this review, we summarized the current literature on the emerging role of fibroblasts in various stages of CRC development, ranging from adenoma initiation to the metastatic spread of cancer cells. In addition, we highlighted translational and therapeutic perspectives of fibroblasts in the different stages of intestinal tumor progression.

Water intake accelerates ATP release from myofibroblast cells in rats: ATP-mediated podoplanin-dependent control for physiological function and immunity

We previously demonstrated that water intake increased mesenteric lymph flow and the total flux of IL-22 in rat jejunum. The drained water and the higher permeability of albumin in the jejunal microcirculation contributed to increase the lymph flow and IL-22 transport via the activation of great bulk flow in the jejunal villi. To address the effects of water intake-mediated great bulk flow-dependent mechanical force on jejunal physiological function and immunological regulation of innate lymphoid cells (ILC)-3, we examined the effects of shear stress stimulation on cultured rat myofibroblast cells. Next, we investigated the effects of water intake on podoplanin and IL-22 expressions in cultured human intestinal epithelial cells and rat in vivo jejunal preparations, respectively. Shear stress stimulation of the myofibroblast cells induced ATP release via an activation of cell surface F₁/F₀ ATP synthase. ATP produced podoplanin expression in the intestinal epithelial cells. Water intake accelerated immunohistochemical expressions of podoplanin and IL-22 in the interepithelial layers and lamina propria of the jejunum. ATP dose-dependently increased IL-22 mRNA expression in ILC-3, which are housed in the lamina propria. Water intake also increased immunohistochemical and mRNA expressions of ecto-nucleoside triphosphate diphosphohydrolases 2 and 5 in jejunal villi. In conclusion, water intake-mediated shear stress stimulation-dependent ATP release from myofibroblast cells maintains higher tissue colloid osmotic pressure in the jejunal microcirculation through podoplanin upregulation in the interepithelial layers. ATP induces IL-22 mRNA expression in ILC-3 in jejunal villi, which may contribute to regulation of mucosal immunity in small intestine.NEW & NOTEWORTHY We investigated effects of shear stress stimulation on cultured myofibroblast cells and water intake on podoplanin and IL-22 expressions in rat jejunal villi. The stimulation induced ATP release from the cells. Water intake accelerated podoplanin and IL-22 expression levels. ATP increased IL-22 mRNA expression in innate lymphoid cells (ILC)-3. Hence, water intake maintains higher osmotic pressure in the jejunal villi through ATP release and podoplanin upregulation. Water intake may regulate the mucosal immunity.

Application of Human Induced Pluripotent Stem Cell-Derived Intestinal Organoids as a Model of Epithelial Damage and Fibrosis in Inflammatory Bowel Disease

Inflammatory bowel disease, which typically manifests as Crohn's disease and ulcerative colitis, is caused by the abnormal production of cytokines such as tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β. These cytokines damage intestinal epithelial cells and trigger fibrosis, respectively, for which the current in vitro models have many limitations. Therefore, we tested whether human induced pluripotent stem cell-derived intestinal organoids (HiOs) can mimic inflammatory bowel disease (IBD), and whether such a model is suitable for drug screening. HiOs were treated with TNF-α and TGF-β to construct mucosal damage and fibrosis models. TNF-α diminished the mRNA expression of intestinal epithelial cell and goblet cell markers in HiOs. TNF-α also induced epithelial cell damage and degradation of tight junctions but not in the presence of infliximab, an antibody used in the clinic to deplete TNF-α. Furthermore, permeation of the non-absorbable marker FD-4 was observed in HiOs treated with TNF-α or ethylene glycol tetraacetic acid (EGTA), but not in the presence of infliximab. In contrast, TNF-α and TGF-β induced mRNA expression of mesenchymal and fibrosis markers, as well as epithelial-mesenchymal transition. SB431542, a TGF-β inhibitor, significantly reversed these events. The data indicate that HiOs mimic mucosal damage and fibrosis due to IBD and are thus suitable models for drug screening.

Stratified layer analysis reveals intrinsic leptin stimulates cryptal mesenchymal cells for controlling mucosal inflammation

Mesenchymal cells in the crypt play indispensable roles in the maintenance of intestinal epithelial homeostasis through their contribution to the preservation of stem cells. However, the acquisition properties of the production of stem cell niche factors by the mesenchymal cells have not been well elucidated, due to technical limitations regarding the isolation and subsequent molecular and cellular analyses of cryptal mesenchymal cells. To evaluate the function of mesenchymal cells located at the large intestinal crypt, we established a novel method through which cells are harvested according to the histologic layers of mouse colon, and we compared cellular properties between microenvironmental niches, the luminal mucosa and crypts. The gene expression pattern in the cryptal mesenchymal cells showed that receptors of the hormone/cytokine leptin were highly expressed, and we found a decrease in Wnt2b expression under conditions of leptin receptor deficiency, which also induced a delay in cryptal epithelial proliferation. Our novel stratified layer isolation strategies thus revealed new microenvironmental characteristics of colonic mesenchymal cells, including the intrinsic involvement of leptin in the control of mucosal homeostasis.

Stromal Cells in the Pathogenesis of Inflammatory Bowel Disease

Up till now, research on inflammatory bowel disease [IBD] has mainly been focused on the immune cells present in the gastrointestinal tract. However, recent insights indicate that stromal cells also play an important and significant role in IBD pathogenesis. Stromal cells in the intestines regulate both intestinal epithelial and immune cell homeostasis. Different subsets of stromal cells have been found to play a role in other inflammatory diseases [e.g. rheumatoid arthritis], and these various stromal subsets now appear to carry out also specific functions in the inflamed gut in IBD. Novel potential therapies for IBD utilize, as well as target, these pathogenic stromal cells. Injection of mesenchymal stromal cells [MSCs] into fistula tracts of Crohn's disease patients is already approved and used in clinical settings. In this review we discuss the current knowledge of the role of stromal cells in IBD pathogenesis. We further outline recent attempts to modify the stromal compartment in IBD with agents that target or replace the pathogenic stroma.

Rapid Prototyping of Multilayer Microphysiological Systems

Microfluidic organs-on-chips aim to realize more biorelevant in vitro experiments compared to traditional two-dimensional (2D) static cell culture. Often such devices are fabricated via poly(dimethylsiloxane) (PDMS) soft lithography, which offers benefits (e.g., high feature resolution) along with drawbacks (e.g., prototyping time/costs). Here, we report benchtop fabrication of multilayer, PDMS-free, thermoplastic organs-on-chips via laser cut and assembly with double-sided adhesives that overcome some limitations of traditional PDMS lithography. Cut and assembled chips are economical to prototype ($2 per chip), can be fabricated in parallel within hours, and are Luer compatible. Biocompatibility was demonstrated with epithelial line Caco-2 cells and primary human small intestinal organoids. Comparable to control static Transwell cultures, Caco-2 and organoids cultured on chips formed confluent monolayers expressing tight junctions with low permeability. Caco-2 cells-on-chip differentiated ∼4 times faster, including increased mucus, compared to controls. To demonstrate the robustness of cut and assemble, we fabricated a dual membrane, trilayer chip integrating 2D and 3D compartments with accessible apical and basolateral flow chambers. As proof of concept, we cocultured a human, differentiated monolayer and intact 3D organoids within multilayered contacting compartments. The epithelium exhibited 3D tissue structure and organoids expanded close to the adjacent monolayer, retaining proliferative stem cells over 10 days. Taken together, cut and assemble offers the capability to rapidly and economically manufacture microfluidic devices, thereby presenting a compelling fabrication technique for developing organs-on-chips of various geometries to study multicellular tissues.

Endoplasmic Reticulum Stress in Subepithelial Myofibroblasts Increases the TGF-β1 Activity That Regulates Fibrosis in Crohn's Disease

BACKGROUND

Endoplasmic reticulum (ER) stress is an essential response of epithelial and immune cells to inflammation in Crohn's disease. The presence and mechanisms that might regulate the ER stress response in subepithelial myofibroblasts (SEMFs) and its role in the development of fibrosis in patients with Crohn's disease have not been examined.

METHODS

Subepithelial myofibroblasts were isolated from the affected ileum and normal ileum of patients with each Montreal phenotype of Crohn's disease and from normal ileum in non-Crohn's subjects. Binding of GRP78 to latent TGF-β1 and its subcellular trafficking was examined using proximity ligation-hybridization assay (PLA). The effects of XBP1 and ATF6 on TGF-β1 expression were measured using DNA-ChIP and luciferase reporter assay. Endoplasmic reticulum stress components, TGF-β1, and collagen levels were analyzed in SEMF transfected with siRNA-mediated knockdown of DNMT1 and GRP78 or with DNMT1 inhibitor 5-Azacytidine or with overexpression of miR-199a-5p.

RESULTS

In SEMF of strictured ileum from patients with B2 Crohn's disease, expression of ER stress sensors increased significantly. Tunicamycin elicited time-dependent increase in GRP78 protein levels, direct interaction with latent TGF-β1, and activated TGF-β1 signaling. The TGFB1 DNA-binding activity of ATF-6α and XBP1 were significantly increased and elicited increased TGFB1 transcription in SEMF-isolated from affected ileum. The levels of ER stress components, TGF-β1, and collagen expression in SEMF were significantly decreased following knockdown of DNMT1 or GRP78 by 5-Azacytidine treatment or overexpression of miR-199a-5p.

CONCLUSIONS

Endoplasmic reticulum stress is present in SEMF of patients susceptible to fibrostenotic Crohn's disease and can contribute to development of fibrosis. Targeting ER stress may represent a novel therapeutic target to prevent fibrosis in patients with fibrostenotic Crohn's disease.

Immunological roles of intestinal mesenchymal cells

The intestine is continuously exposed to an enormous variety and quantity of antigens and innate immune stimuli derived from both pathogens and harmless materials, such as food and commensal bacteria. Accordingly, the intestinal immune system is uniquely adapted to ensure appropriate responses to the different kinds of challenge; maintaining tolerance to harmless antigens in the steady-state, whilst remaining poised to deal with potential pathogens. To accomplish this, leucocytes of the intestinal immune system have to adapt to a constantly changing environment and interact with many different non-leucocytic intestinal cell types, including epithelial and endothelial cells, neurons, and a heterogenous network of intestinal mesenchymal cells (iMC). These interactions are intricately involved in the generation of protective immunity, the elaboration of inflammatory responses, and the development of inflammatory conditions, such as inflammatory bowel diseases. Here we discuss recent insights into the immunological functions of iMC under homeostatic and inflammatory conditions, focusing particularly on iMC in the mucosa and submucosa, and highlighting how an appreciation of the immunology of iMC may help understand the pathogenesis and treatment of disease.

Fibrostenotic strictures in Crohn's disease

The use of biologic agents including anti-tumor necrosis factor monoclonal antibodies followed by anti-integrins and anti-interleukins has drastically changed the treatment paradigm of Crohn’s disease (CD) by improving clinical symptoms and mucosal healing. However, up to 70% of CD patients still eventually undergo surgery mainly due to fibrostenotic strictures. There are no specific anti-fibrotic drugs yet. This review comprehensively addresses the mechanism, prediction, diagnosis and treatment of the fibrostenotic strictures in CD. We also introduce promising anti-fibrotic agents which may be available in the near future and summarize challenges in developing novel therapies to treat fibrostenotic strictures in CD.

GLP-2, EGF, and the Intestinal Epithelial IGF-1 Receptor Interactions in the Regulation of Crypt Cell Proliferation

Glucagon-like peptide-2 (GLP-2) is an intestinotrophic hormone that promotes intestinal growth and proliferation through downstream mediators, including epidermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1). EGF synergistically enhances the proliferative actions of IGF-1 in intestinal cell lines, and both of these factors are known to be essential for the trophic effects of GLP-2 in vivo. However, whether EGF and IGF-1 interact to mediate the proliferative actions of GLP-2 in vivo remains unknown. Normal and knockout (KO) mice lacking the intestinal epithelial IGF-1 receptor (IE-IGF-1R) were therefore treated chronically with EGF and/or long-acting human hGly2GLP-2, followed by determination of intestinal growth parameters. Intestines from control and IE-IGF-1R KO mice were also used to generate organoids (which lack the GLP-2 receptor) and were treated with EGF and/or IGF-1. Combination treatment with EGF and hGly2GLP-2 increased small intestinal weight and crypt-villus height in C57Bl/6 mice in an additive manner, whereas only hGly2GLP-2 treatment increased crypt cell proliferation. However, although combination treatment also increased small intestinal weight and crypt-villus height in IE-IGF-1R KO mice, the proliferative responses to hGly2GLP-2 alone or with EGF were diminished in these animals. Finally, IGF-1 treatment of organoids undergoing EGF withdrawal was not additive to the effect of EGF replacement on proliferation, but could restore normal proliferation in the absence of EGF. Together, these findings demonstrate that the intestinal proliferative effects of hGly2GLP-2 are augmented by exogenous EGF in a manner that is partially dependent upon IE-IGF-1R signaling.

Diminished Vitamin D Receptor Protein Levels in Crohn's Disease Fibroblasts: Effects of Vitamin D

Vitamin D (VD) deficiency has been associated to Crohn’s disease (CD) pathogenesis, and the exogenous administration of VD improves the course of the disease, but the mechanistic basis of these observations remains unknown. Vitamin D receptor (VDR) mediates most of the biological functions of this hormone, and we aim to analyze here the expression of VDR in intestinal tissue, epithelial cells, and fibroblasts from CD patients. The effects of VD on a fibroblast wound healing assay and murine intestinal fibrosis are also analyzed. Our data show diminished VDR protein levels in surgical resections and epithelial cells from CD patients. In intestinal fibroblasts isolated from damaged tissue of CD patients, we detected enhanced migration and decreased VDR expression compared with both fibroblasts from non-damaged tissue of the same CD patient or control fibroblasts. Treatment with VD increased VDR protein levels, avoided the accelerated migration in CD fibroblasts, and prevented murine intestinal fibrosis induced by the heterotopic transplant model. In conclusion, our study demonstrates diminished VDR protein levels associated with enhanced migration in intestinal fibroblasts from damaged tissue of CD patients. In these cells, VD accumulates VDR and normalizes migration, which supports that CD patients would benefit from the VD anti-fibrotic therapeutic value that we demonstrate in a murine experimental model.

Participation of Somatic Stem Cells, Recognized by a Unique A3 Antibody, in Mucosal Epithelial Regeneration in Dextran Sulfate Sodium (DSS)-Induced Rat Colonic Lesions

A3, generated as a monoclonal antibody against rat malignant fibrous histiocytoma cells, recognizes somatic stem cells in rats. We analyzed the distribution of A3-positive cells in dextran sulfate sodium (DSS)-induced colonic lesions consisting of regenerating mucosa and fibrosis. Male 6-week-old F344 rats were administered 5% DSS in drinking water for 5 to 7 days, and lesions at recovery stage were also examined. In untreated control adult colons, A3-positive cells are localized around the crypts where stem cell niche is formed. Histopathologically, in colons of DSS-administered rats, mucosal atrophy, inflammatory cell infiltration, and fibrosis were observed in the lamina propria; thereafter, mucosal epithelia were desquamated, and crypts were decreased gradually with decrease in surrounding A3-positive cells. At the early recovery stage, crypts showed regeneration with reappearance of A3-positive cells. Interestingly, A3-positive cells aggregated in desquamated mucosa surface of fibrosis. Aggregated A3-positive cells coexpressed with vimentin, Thy-1, and partly CK19 but did not react simultaneously with α-SMA. Likely, aggregated A3-positive cells may be rescue cells with nature of both mesenchymal and epithelial cells to maintain self-renewal after injury in the colon. A3 antibody would become a useful tool to investigate the participation of stem cells in rat colonic lesions.

The John F. Maher Recipient Lecture 2004: Rage in the Peritoneum

Several conditions in the peritoneal membrane of peritoneal dialysis (PD) patients promote the accumulation of advanced glycation end-products (AGEs), that is, the uremic state, exposure to high glucose concentrations, and exposure to glucose degradation products (GDPs). AGEs exert some of their biologic actions through binding with a cell surface receptor, termed RAGE. Interaction of AGEs with RAGE induces sustained cellular activation, including the production of the fibrogenic growth factor, transforming growth factor-beta (TGF-β). TGF-β is pivotal in the process of epithelial-to-mesenchymal transition, through which cells of epithelial origin acquire myofibroblastic characteristics. Myofibroblasts are involved in virtually all conditions of pathological fibrosis. Submesothelial fibrosis is an important feature in peritoneal biopsies of PD patients, especially of those with clinical problems. We therefore examined the role of RAGE in peritoneal fibrosis, in an animal model of uremia, of high glucose exposure, and of peritoneal dialysate exposure.

All three models were characterized by accumulation of AGEs, upregulation of RAGE, and fibrosis. Antagonism of RAGE prevented the upregulation of TGF-β and fibrosis in the peritoneal membrane. We further examined the underlying mechanism of peritoneal fibrosis in the uremic model. Prominent myofibroblast transdifferentiation of mesothelial cells was identified by co-localization of cytokeratin and α-smooth muscle actin in submesothelial and interstitial fibrotic tissue. Antagonism of RAGE prevented conversion of mesothelial cells to myofibroblasts in uremia.

In conclusion, we hypothesize that accumulation of AGEs in the peritoneal membrane, as a consequence of the uremic environment, chronic exposure to high glucose, and exposure to GDPs, results in an increased expression of RAGE. The interaction of AGEs with RAGE induces peritoneal fibrosis by virtue of upregulation of TGF-β and subsequent conversion of mesothelial cells into myofibroblasts.

Intrinsic Control of Surface Immune and Epithelial Homeostasis by Tissue-Resident Gut Stromal Cells

The epithelial layer creates a chemical and physical barrier at the forefront of intestinal mucosa, and immune cells beneath the surface epithelium are poised to react to extrinsic factors, to maintain tissue homeostasis. Importantly, the nexus of epithelial-immune responses at mucosal surfaces is dexterously modulated by intrinsic stromal-mesenchymal cells. First, organogenesis of lymphoid tissues, including Peyer's patches, requires dynamic interplay between lymphoid cells and stromal cells, which have become known as "lymphoid organizers." Second, correct spatiotemporal interaction between these cell populations is essential to generate the infrastructure for gut immune responses. Moreover, immune cells at the intestinal barrier are functionally modulated by stromal cells; one such example is the stromal cell-mediated differentiation of innate immune cells, including innate lymphoid cells and mast cells. Ultimately, mucosal stromal cells orchestrate the destinations of epithelial and immune cells to maintain intestinal immune homeostasis.

Development and characterization of a stable bovine intestinal sub-epithelial myofibroblast cell line from ileum of a young calf

Intestinal sub-epithelial myofibroblasts (ISEMFs) are mesenchymal cells that do not express cytokeratin but express α-smooth muscle actin and vimentin. Despite being cells with diverse functions, there is a paucity of knowledge about their origin and functions primarily due to the absence of a stable cell line. Although myofibroblast in vitro models for human, mouse, and pig are available, there is no ISEMF cell line available from young calves. We isolated and developed an ileal ISEMF cell line from a 2-d-old calf that expressed α-smooth muscle actin and vimentin but no cytokeratin indicating true myofibroblast cells. To overcome replicative senescence, we immortalized primary cells with SV40 large T antigen. We characterized and compared both primary and immortalized ileal ISEMF cells for surface glycan and Toll-like-receptor (TLR) expression by lectin-binding assay and real-time quantitative PCR (RT-qPCR) assay respectively. SV40 immortalization significantly decreased surface lectin binding for lectins GSL-I, PHA-L, ECL, Jacalin, Con-A, LCA, and LEL. Both cell types expressed TLRs 1-9 and showed no significant differences in TLR expression. Thus, these cells can be useful in vitro model to study ISEMF's origin, physiology, and functions.

Effect of transforming growth factor -β1 on α-smooth muscle actin and collagen expression in equine endometrial fibroblasts

Transforming growth factor (TGF)-β1 not only regulates cell growth, development, and tissue remodeling, but it also participates in the pathogenesis of tissue fibrosis. In the equine endometrium, the concentration of TGF-β1 is correlated with endometrosis (equine endometrial fibrosis). In other tissues, TGF-β1 induces differentiation of many cell types into myofibroblasts. These cells are characterized by α-smooth muscle actin (α-SMA) expression and an ability to deposit excessive amounts of extracellular matrix (ECM) components. The aim of the study was to determine whether TGF-β1 plays a role in the development of equine endometrosis. In Exp. 1, endometrial expression of α-SMA in different stages of endometrosis was determined. In endometrial tissues from the mid luteal phase (n = 6 for each stages of endometrosis) and the follicular phase of the estrous cycle (n = 5 for each stages of endometrosis), mRNA transcription and protein expression of α-Sma were evaluated by Real-time PCR and Western-blot, respectively. The α-Sma mRNA transcription and protein expression levels were correlated with the severity of endometrosis (P < 0.05). In both phases of the estrous cycle, α-SMA protein expression was up-regulated in final stage of endometrosis compared to initial stage (P < 0.05). In Exp. 2, the dose- and time-dependent effects of TGF-β1 on expression of α-SMA and ECM components were determined, as well as cell proliferation of equine fibroblasts. Equine endometrial fibroblasts (n = 6, Kenney and Doig category I) were stimulated with vehicle or TGF-β1 (1, 5, 10 ng/ml) for 24, 48 or 72 h. Then, mRNA transcription of α-Sma, collagen type I (Col1a1), collagen type III (Col3a1) and fibronectin 1 (Fn1) were determined by Real-time PCR. The production of ECM components was determined by ELISA. Transforming growth factor-β1 increased the mRNA transcription of α-Sma and ECM components in a dose- and time-dependent manner in cultured endometrial fibroblasts (P < 0.05). Additionally, TGF-β1 at a dose of 10 ng/ml increased α-SMA protein expression and COL1, COL3, FN production after 72 h of stimulation (P < 0.05). The data showed a positive linkage between the presence of myofibroblasts and severity of endometrosis. We conclude that TGF-β1 may participate in pathological fibrotic changes in equine endometrial tissue by induction of myofibroblast differentiation, increased production of ECM components and fibroblast proliferation.

Cellular Interactions in the Intestinal Stem Cell Niche

Epithelial cells are one of the most actively cycling cells in a mammalian organism and therefore are prone to malignant transformation. Already during organogenesis, the connective tissue (mesenchyme) provides instructive signals for the epithelium. In an adult organism, the mesenchyme is believed to provide crucial regulatory signals for the maintenance and regeneration of epithelial cells. Here, we discuss the role of intestinal myofibroblasts, α-smooth muscle actin-positive stromal (mesenchymal) cells, as an important regulatory part of the intestinal stem cell niche. Better understanding of the cross-talk between myofibroblasts and the epithelium in the intestine has implications for advances in regenerative medicine, and improved therapeutic strategies for inflammatory bowel disease, intestinal fibrosis and colorectal cancer.

The localization and distribution of cells labeled by a somatic stem cell-recognizing antibody (A3) in rat colon development; possible presence of a new cell type forming the intestinal stem cell niche

A3, generated as a monoclonal antibody against rat malignant fibrous histiocytoma (MFH)-derived cloned cells, recognizes somatic stem cells (bone-marrow/hair follicle stem cells). We investigated the distribution of cells immunoreactive to A3 in the developing rat intestine (particularly, the colon), focusing on the ontogenic kinetics of A3-positive cells. In the rat intestine, A3 labeled spindle-shaped stromal cells localized in the submucosa and labeled endothelial cells of capillaries in the lamina propria forming villi in the early development stage. With development progression, A3-positive cells were exclusively localized around the crypts of the colon. Double immunofluorescence revealed that A3-positive cells around the crypts reacted to vimentin (for mesenchymal cells) and Thy-1 (for mesenchymal stromal cells) but not to α-SMA (for mesenchymal myofibroblastic cells) or CD34 (for hematopoietic stem cells), indicating that A3-positive cells around the crypts may have characteristics of immature mesenchymal cells. In addition, A3 labeled a few epithelial cells at the base of colon crypts. Furthermore, immunoelectron microscopy revealed that A3-positive cells lay inside myofibroblasts adjacent to the epithelium of the crypts. A3-positive cells were regarded as a new type of immature mesenchymal cells around the crypts. Collectively, A3-positive cells might take part in the stem cell niche in the colon, which is formed through epithelial-mesenchymal interaction.

Review article: pathogenesis of Crohn's perianal fistula-understanding factors impacting on success and failure of treatment strategies

BACKGROUND

Evidence from groups who have studied fistula aetiology and extrapolation from interventional studies supports a multifactorial hypothesis of Crohn's perianal fistula, with several pathophysiological elements that may contribute to fistula formation, persistence and resistance to treatment.

AIM

An evidence synthesis of current understanding of pathophysiological factors underlying Crohn's perianal fistula is presented, exploring the fundamental reasons why some treatments succeed and others fail, as a means of focussing clinical knowledge on improving treatment of Crohn's perianal fistula.

METHODS

Evidence to support this review was gathered via the Pubmed database. Studies discussing pathophysiological factors underpinning perianal fistula, particularly in Crohn's disease, were reviewed and cross-referenced for additional reports.

RESULTS

Pathophysiological factors that impact on success or failure of interventions for Crohn's perianal fistulae include the high-pressure zone, obliterating the dead space, disconnecting the track from the anus, removing epithelialisation, eradicating sepsis and by-products of bacterial colonisation, correcting abnormalities in wound repair and removing the pro-inflammatory environment which allows fistula persistence. Most current interventions for Crohn's perianal fistulae tend to focus on a single, or at best two, aspects of the pathophysiology of Crohn's anal fistulae; as a result, failure to heal fully is common.

CONCLUSIONS

For an intervention or combination of interventions to succeed, multiple factors must be addressed. We hypothesise that correct, timely and complete attention to all of these factors in a multimodal approach represents a new direction that may enable the creation of an effective treatment algorithm for Crohn's anal fistula.

Lactobacillus rhamnosus GG increases cyclooxygenase-2 expression and prostaglandin E2 secretion in colonic myofibroblasts via a MyD88-dependent mechanism during homeostasis

Prostaglandin E2 (PGE₂ ) plays a critical role in intestinal mucosal tolerance and barrier integrity. Cyclooxygenase-2 (COX-2)-dependent PGE₂ production involves mobilisation of arachidonic acid. Lactobacillus rhamnosus GG (LbGG) is one of the most widely used probiotics reported to colonise the colonic mucosa. LbGG contributes to the protection of the small intestine against radiation injury through the repositioning of mucosal COX-2 expressing cells. However, it is unknown if LbGG modulates PGE₂ production in the colonic mucosa under homeostasis and the major cellular elements involved in these processes. Colonic epithelial and CD90⁺ mesenchymal stromal cells, also known as (myo) fibroblasts (CMFs), are abundant innate immune cells in normal colonic mucosa able to produce PGE₂ . Herein, we tested the hypothesis that under colonic mucosal homeostasis, LbGG modulates the eicosanoid pathway resulting in increased PGE₂ production in both epithelial and stromal cells. Among the five tested human colonic epithelial cell lines, only exposure of Caco-2 to LbGG for 24 hr led to the mobilisation of arachidonic acid with concomitant increase in the components within the leukotriene and COX-2-dependent PGE₂ pathways. By contrast, CMFs isolated from the normal human colonic mucosa responded to LbGG with increased expression of COX-2 and PGE₂ in the prostaglandin pathway, but not 5-LO in the leukotriene pathway. Oral gavage of C57BL/6 mice for 5 days with LbGG (5 × 10⁸ Colony-Forming Unit (CFU)/dose) increased COX-2 expression in the colonic mucosa. The majority of cells upregulating COX-2 protein expression were located in the colonic lamina propria and colocalised with α-SMA⁺ cells corresponding to the CMF phenotype. This process was myeloid differentiation factor-88-dependent, because silencing of myeloid differentiation factor-88 expression in CMFs abrogated LbGG-induced upregulation of COX-2 in culture and in vivo. Taken together, our data suggest that LbGG increases release of COX-2-mediated PGE₂ , contributing to the maintenance of mucosal homeostasis in the colon and CMFs are among the major contributors to this process.

Resveratrol Chemosensitizes TNF-β-Induced Survival of 5-FU-Treated Colorectal Cancer Cells

Objective: Resveratrol, a safe and multitargeted natural agent, has been linked with inhibition of survival and invasion of tumor cells. Tumor Necrosis Factor-β (TNF-β) (Lymphotoxin α) is known as an inflammatory cytokine, however, the underlying mechanisms for its pro-carcinogenic effects and whether resveratrol can suppress these effects in the tumor microenvironment are poorly understood. Methods: We investigated whether resveratrol modulates the effects of 5-Fluorouracil (5-FU) and TNF-β on the malignant potential of human colorectal cancer (CRC) cells (HCT116) and their corresponding isogenic 5-FU-chemoresistant derived clones (HCT116R) in 3D-alginate tumor microenvironment. Results: CRC cells cultured in alginate were able to migrate from alginate and the numbers of migrated cells were significantly increased in the presence of TNF-β, similar to TNF-α, and dramatically decreased by resveratrol. We found that TNF-β promoted chemoresistance in CRC cells to 5-FU compared to control cultures and resveratrol chemosensitizes TNF-β-induced increased capacity for survival and invasion of HCT116 and HCT116R cells to 5-FU. Furthermore, TNF-β induced a more pronounced cancer stem cell-like (CSC) phenotype (CD133, CD44, ALDH1) and resveratrol suppressed formation of CSC cells in two different CRC cells and this was accompanied with a significant increase in apoptosis (caspase-3). It is noteworthy that resveratrol strongly suppressed TNF-β-induced activation of tumor-promoting factors (NF-κB, MMP-9, CXCR4) and epithelial-to-mesenchymal-transition-factors (increased vimentin and slug, decreased E-cadherin) in CRC cells. Conclusion: Our results clearly demonstrate for the first time that resveratrol modulates the TNF-β signaling pathway, induces apoptosis, suppresses NF-κB activation, epithelial-to-mesenchymal-transition (EMT), CSCs formation and chemosensitizes CRC cells to 5-FU in a tumor microenvironment.

Colon organoid formation and cryptogenesis are stimulated by growth factors secreted from myofibroblasts

Although small intestinal epithelial stem cells form crypts when using intestinal culture conditions, colon stem cells usually form colonospheres. Colon mesenchymal cell feeder layers can stimulate colon crypts to form organoids and produce crypts. We have investigated whether conditioned medium from colon mesenchymal cells can also stimulate colonosphere and organoid cryptogenesis. We prepared conditioned medium (CM) from WEHI-YH2 cells (mouse colon myofibroblasts); the CM stimulated both colonosphere formation and organoid cryptogenesis in vitro. The colon organoid-stimulating factors in WEHI-YH2 CM are inactivated by heating and trypsin digestion and proteins can be concentrated by ultrafiltration. Both the colonosphere- and organoid cryptogenesis- stimulatory effects of the CM are independent of canonical Wnt and Notch signaling. In contrast, bone morphogenetic protein 4 (BMP4) abolishes colonosphere formation and organoid cryptogenesis. The Transforming Growth Factor beta (TGFβ) Type I receptor kinase inhibitor (A83-01) stimulates colonosphere formation, whereas the Epidermal Growth Factor receptor (EGFR) kinase inhibitor (AG1478) reduces the formation of colonospheres, but in the presence of EGF, a “just-right” concentration of AG1478 increases colon organoid cryptogenesis.

Combined activity of COX-1 and COX-2 is increased in non-neoplastic colonic mucosa from colorectal neoplasia patients

Background

Cyclooxygenase (COX) activity is increased in endoscopic normal colonic mucosa from patients with colorectal neoplasia (CRN). COX-2 is thought to be the predominant COX isozyme involved in neoplasia. Meanwhile, relative contributions of COX-1 and COX-2 isoforms are unknown. Knowledge about their mutual activity in colonic mucosa is important for diagnostics and targeted therapy for CRN. The aim of this study was to assess the relative function, expression and localization of COX-1 and COX-2 enzymes in colonic non-neoplastic human mucosa and thereby to potentially reveal a mucosal disease predisposition for better treatment.

Methods

Biopsies were pinched from normal appearing colonic mucosa in patients undergoing endoscopy. Ussing chamber technique was applied for an indirect assessment of epithelial activity, RT-qPCR for expression and immunohistochemistry for localization of COX-1 and COX-2 enzymes in patients without (ctrls) and with a history of CRN (CRN-pts).

Results

Combined COX-1 and COX-2 activity was higher in CRN-pts, p = 0.036. COX-2 was primarily localized in absorptive cells, while COX-1 appeared to be restricted to nonenteroendocrine tuft cells of the colonic epithelium.

Conclusions

In biopsies from endoscopic normal appearing colonic mucosa, combined activity of COX-1 and COX-2 enzymes is increased in CRN-pts compared with ctrls. This indicates that COX-1 and COX-2 together contribute to an increased proliferation process. Of note, in colonic epithelial cell lining, the COX-1 enzyme seems localized in tuft cells.

PDGF in organ fibrosis

Fibrosis is part of a tissue repair response to injury, defined as increased deposition of extracellular matrix. In some instances, fibrosis is beneficial; however, in the majority of diseases fibrosis is detrimental. Virtually all chronic progressive diseases are associated with fibrosis, representing a huge number of patients worldwide. Fibrosis occurs in all organs and tissues, becomes irreversible with time and further drives loss of tissue function. Various cells types initiate and perpetuate pathological fibrosis by paracrine activation of the principal cellular executors of fibrosis, i.e. stromal mesenchymal cells like fibroblasts, pericytes and myofibroblasts. Multiple pathways are involved in fibrosis, platelet-derived growth factor (PDGF)-signaling being one of the central mediators. Stromal mesenchymal cells express both PDGF receptors (PDGFR) α and β, activation of which drives proliferation, migration and production of extracellular matrix, i.e. the principal processes of fibrosis. Here, we review the role of PDGF signaling in organ fibrosis, with particular focus on the more recently described ligands PDGF-C and -D. We discuss the potential challenges, opportunities and open questions in using PDGF as a potential target for anti-fibrotic therapies.