PDGF-α stimulates intestinal epithelial cell turnover after massive small bowel resection in a rat

Epithelial-specific loss of Smad4 alleviates the fibrotic response in an acute colitis mouse model

Mucosal healing is associated with better clinical outcomes in patients with inflammatory bowel disease. But the epithelial-specific contribution to mucosal healing in vivo is poorly understood. We evaluated mucosal healing in an acute dextran sulfate sodium mouse model that shows an alleviated colitis response after epithelial-specific loss of Smad4. We find that enhanced epithelial wound healing alleviates the fibrotic response. Dextran sulfate sodium caused increased mesenchymal collagen deposition-indicative of fibrosis-within a week in the WT but not in the Smad4 KO colon. The fibrotic response correlated with decreased epithelial proliferation in the WT, whereas uninterrupted proliferation and an expanded zone of proliferation were observed in the Smad4 KO colon epithelium. Furthermore, the Smad4 KO colon showed epithelial extracellular matrix alterations that promote epithelial regeneration. Our data suggest that epithelium is a key determinant of the mucosal healing response in vivo, implicating mucosal healing as a strategy against fibrosis in inflammatory bowel disease patients.

Smad4 Loss in the Mouse Intestinal Epithelium Alleviates the Pathological Fibrotic Response to Injury in the Colon

Mucosal healing is associated with better clinical outcomes in patients with inflammatory bowel diseases (IBDs). Unresolved injury and inflammation, on the other hand, increases pathological fibrosis and the predisposition to cancer. Loss of Smad4, a tumor suppressor, is known to increase colitis-associated cancer in mouse models of chronic IBD. Since common biological processes are involved in both injury repair and tumor growth, we sought to investigate the effect of Smad4 loss on the response to epithelial injury. To this end, Smad4 was knocked out specifically in the intestinal epithelium and transcriptomic and morphological changes compared between wild type mice and Smad4 knock out mice after DSS-induced injury. We find that Smad4 loss alleviates pathological fibrosis and enhances mucosal repair. The transcriptomic changes specific to epithelium indicate molecular changes that affect epithelial extracellular matrix (ECM) and promote enhanced mucosal repair. These findings suggest that the biological processes that promote wound healing alleviate the pathological fibrotic response to DSS. Therefore, these mucosal repair processes could be exploited to develop therapies that promote normal wound healing and prevent fibrosis.

NEW AND NOTEWORTHY

We show that transcriptomic changes due to Smad4 loss in the colonic epithelium alleviates the pathological fibrotic response to DSS in an IBD mouse model of acute inflammation. Most notably, we find that collagen deposition in the epithelial ECM, as opposed to that in the lamina propria, correlates with epithelial changes that enhance wound healing. This is the first report on a mouse model providing alleviated fibrotic response in a DSS-IBD mouse model in vivo .

The effect of hepatocyte growth factor on intestinal adaption in an experimental model of short bowel syndrome

PURPOSE

Nowadays, the standard therapy for patients with short bowel syndrome is parenteral nutrition (PN). Various growth factors have been tested to achieve weaning from prolonged PN administration. We evaluated the effect of hepatocyte growth factor (HGF) on structural intestinal adaptation and cell proliferation in a rat model of SBS.

METHODS

Thirty Sprague-Dawley rats were divided into three groups; group A rats (sham) underwent bowel transection, group B rats underwent a 75% bowel resection, and group C rats underwent the same procedure but were treated postoperatively with HGF. Histopathologic parameters of intestinal adaptation were determined, while microarray and rt-PCR analyses of ileal RNA were also performed.

RESULTS

Treatment with HGF resulted in significant increase in body weight, while the jejunal and ileal villus height and crypt depth were increased in HGF rats (36%, p < 0.05 and 27%, p < 0.05 respectively). Enterocyte proliferation was also significantly increased in HGF rats (21% p < 0.05). Microarray and quantitative rt-PCR analyses showed that the genes hgfac, rac 1, cdc42, and akt 1 were more than twofold up-regulated after HGF treatment.

CONCLUSION

HGF emerges as a growth factor that enhances intestinal adaptation. The future use of HGF may potentially reduce the requirement for PN in SBS patients.

Two cases of nintedanib-induced diarrhoea treated using a 5-HT type 3 receptor antagonist

Nintedanib has been used in the management of patients with idiopathic pulmonary fibrosis (IPF) and progressive pulmonary fibrosis (PPF) [1, 2]. The most common adverse event associated with nintedanib is diarrhoea. In the INPULSIS and INBUILD trials, >60% of patients reported diarrhoea [1, 2]. Antidiarrhoeal medications, including loperamide, are usually administered and are adequate in some patients. However, a significant proportion of patients continue to experience frequent diarrhoea, even after antidiarrhoeal treatment. In the INBUILD trial, ∼30% of patients who experienced diarrhoea at least once required dose reduction or discontinuation of nintedanib [2]. Hence, new treatments for diarrhoea are needed to improve quality of life in these patients. Ramosetron, a serotonin (5-hydroxytryptamine) type 3 (5-HT₃) receptor inhibitor used for diarrhoea-predominant irritable bowel syndrome (IBS-D), might be a suitable treatment for nintedanib-induced diarrhoea [3], and has a low risk of hard stool (1.11%) and constipation (1.11%) [4].

Nintedanib-induced diarrhoea may be controlled by ramosetron by modulation of intestinal motility as for irritable bowel syndrome #pulmonaryfibrosishttps://bit.ly/3OQVAII

The Charming World of the Extracellular Matrix: A Dynamic and Protective Network of the Intestinal Wall

The intestinal extracellular matrix (ECM) represents a complex network of proteins that not only forms a support structure for resident cells but also interacts closely with them by modulating their phenotypes and functions. More than 300 molecules have been identified, each of them with unique biochemical properties and exclusive biological functions. ECM components not only provide a scaffold for the tissue but also afford tensile strength and limit overstretch of the organ. The ECM holds water, ensures suitable hydration of the tissue, and participates in a selective barrier to the external environment. ECM-to-cells interaction is crucial for morphogenesis and cell differentiation, proliferation, and apoptosis. The ECM is a dynamic and multifunctional structure. The ECM is constantly renewed and remodeled by coordinated action among ECM-producing cells, degrading enzymes, and their specific inhibitors. During this process, several growth factors are released in the ECM, and they, in turn, modulate the deposition of new ECM. In this review, we describe the main components and functions of intestinal ECM and we discuss their role in maintaining the structure and function of the intestinal barrier. Achieving complete knowledge of the ECM world is an important goal to understand the mechanisms leading to the onset and the progression of several intestinal diseases related to alterations in ECM remodeling.

Digestive enzyme expression in the large intestine of children with short bowel syndrome in a late stage of adaptation

BACKGROUND AND AIMS

Intestinal adaptation in short bowel syndrome (SBS) includes morphologic processes and functional mechanisms. This study investigated whether digestive enzyme expression in the duodenum and colon is upregulated in SBS patients.

METHOD

Sucrase-isomaltase (SI), lactase-phlorizin hydrolase (LPH), and neutral Aminopeptidase N (ApN) were analyzed in duodenal and colonic biopsies from nine SBS patients in a late stage of adaptation as well as healthy and disease controls by immunoelectron microscopy (IEM), Western blots, and enzyme activities. Furthermore, proliferation rates and intestinal microbiota were analyzed in the mucosal specimen.

RESULTS

We found significantly increased amounts of SI, LPH, and ApN in colonocytes in most SBS patients with large variation and strongest effect for SI and ApN. Digestive enzyme expression was only partially elevated in duodenal enterocytes due to a low proliferation level measured by Ki-67 staining. Microbiome analysis revealed high amounts of Lactobacillus resp. low amounts of Proteobacteria in SBS patients with preservation of colon and ileocecal valve. Colonic expression was associated with a better clinical course in single cases.

CONCLUSION

In SBS patients disaccharidases and peptidases can be upregulated in the colon. Stimulation of this colonic intestinalization process by drugs, nutrients, and pre- or probiotics might offer better therapeutic approaches.

Upregulation of VEGFR1 in a rat model of esophagogastric anastomotic healing

INTRODUCTION

Anastomotic leakage after gastrointestinal surgery is a significant cause of morbidity and mortality. Esophagogastric and colorectal anastomoses are vulnerable to leakage. Extended knowledge of growth factors and their receptors is needed to understand anatomic healing.

METHODS

The expression pattern of vascular growth factor receptor (VEGFR1-3), epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFRα/β) and keratinocyte growth factor receptor (KGFR) were analyzed by semiquantitative-PCR in the rat intestinal tract and in esophagogastric anastomosis 5d after surgery.

RESULTS

VEGFR1, VEGFR2, EGFR, KGFR and PDGFRα expression was observed throughout the intestinal tract including esophagus, stomach, small bowl and colon. VEGFR3 was not found in gastric samples and PDGFRβ expression was not detected in the small bowl. Semiquantitative analyses of the VEGFR1, PDGFRα and EGFR expression in esophagogastric anastomotic tissues revealed a 2-fold upregulation of the VEGFR1 in gastric samples, while no change was observed in the esophageal anastomotic side.

CONCLUSION

Our results revealed a distinct expression pattern of the investigated growth factor receptors in rat intestinal tract. Showing higher expression levels of growth factor receptors at the gastric anastomotic tissue at the fifth postoperative day suggests a different contribution of the gastric and the esophageal side to the anastomotic healing.

Effect of bowel resection on TLR signaling during intestinal adaptation in a rat model

BACKGROUND

Bacterial overgrowth is common complication of short bowel syndrome (SBS) and is a result of an impaired gut barrier function. Toll-like receptor 4 (TLR4) is crucial in maintaining intestinal epithelial homeostasis, participates in a vigorous signaling process and heightens inflammatory cytokine output. The objective of this study was to determine the effects of bowel resection on TLR4 signaling in intestinal mucosa in a rat model.

METHODS

Male Sprague-Dawley rats were randomly assigned to one of the two experimental groups of eight rats each: Sham rats underwent bowel transection and re-anastomosis and SBS rats underwent 75 % small bowel resection. Rats were killed on day 14. Bacterial translocation (BT) to mesenteric lymph nodes, liver, portal blood and peripheral blood was determined at the kill. The expression of TLR4, MyD88 and TRAF6 in the intestinal mucosa was determined using real-time PCR, Western blot and immunohistochemistry.

RESULTS

SBS rats demonstrated a 100 % BT to lymph nodes and to liver (Level I), 80 % translocation to portal blood (Level II) and 60 % translocation to peripheral blood (Level III) at day 7 as well as a 100 % BT to lymph nodes and liver, and 40 % translocation to peripheral blood at day 14. Microarray expression profiling demonstrated that most of the TLR signaling-related genes were up-regulated in resected rats compared to control animals. SBS rats showed a significant increase in TLR4 and TRAF6 mRNA in jejunum and ileum, TLR4 and MyD88 protein expression in jejunum and ileum, and a significant increase in the number of TLR4 and TRAF6 positive cells (immunohistochemistry) compared to sham animals.

CONCLUSIONS

In a rat model of SBS, elevated intestinal BT is associated with a stimulated TLR4 signaling.

Vasopressin regulation of epithelial colonic proliferation and permeability is mediated by pericryptal platelet-derived growth factor A

Arginine vasopressin (AVP) has trophic effects on the rat distal colon, increasing the growth of pericryptal myofibroblasts and reducing the colonic crypt wall permeability. This study aimed to reproduce in vitro the effects of AVP observed in vivo using cultures of human CCD-18Co myofibroblasts and T84 colonic epithelial cells. Proliferation of myofibroblasts was quantified by bromodeoxyuridine incorporation; the expression of platelet-derived growth factor A (PDGFA), platelet-derived growth factor B, epidermal growth factor, transforming growth factor-β and vascular endothelial growth factor was measured by PCR and the expression of epithelial junction proteins by Western blot. Arginine vasopressin stimulated myofibroblast proliferation and the expression of PDGFA without affecting the expression of platelet-derived growth factor B, epidermal growth factor, transforming growth factor-β or vascular endothelial growth factor. These effects were prevented when AVP receptor inhibitors were present in the medium. Pre-incubation of CCD-18Co cells with anti-PDGF antibody or with an inhibitor of the PDGF receptor abolished the effects of AVP. When colonocytes were incubated with medium obtained from myofibroblasts incubated with AVP, both cell proliferation and the expression of epithelial junction proteins increased; however, direct incubation of colonocytes with AVP did not modify these variables. These results demonstrate that AVP stimulates myofibroblast proliferation and induces PDGFA secretion, implying that PDGFA mediates local myofibroblast proliferation by an autocrine feedback loop and regulates epithelial proliferation and permeability by a paracrine mechanism.

Distraction-induced intestinal growth: the role of mechanotransduction mechanisms in a mouse model of short bowel syndrome

Novel strategies are needed to address the problem of patients with short bowel syndrome. We previously demonstrated a three-fold lengthening of pig bowel after 2 weeks of applied distractive forces, but we have not elucidated the mechanisms facilitating this growth. We used a mouse model of distraction-induced enterogenesis. High molecular weight polyethylene glycol (PEG) osmotically stretched an isolated small bowel segment (PEG-stretch). Significant increases in villus height and crypt depth and in intestinal epithelial cell length and numbers suggested epithelial remodeling in addition to proliferation during enterogenesis. LC-MS/MS analysis showed a two-fold upregulation of α-actinin-1 and -4. We also demonstrated that p-focal adhesion kinase (FAK), FAK, α-actinin, and Rac1 were significantly upregulated and that F-actin was relocalized in PEG-stretch versus controls. Blockade of the phosphotidyl inositol 3' kinase pathway failed to influence the increase in proliferation or decline in apoptosis after stretch, suggesting alternative signaling pathways are used, including MEK and P38MAPK, which were both upregulated during enterogenesis. Our data suggests that several known mechanotransduction pathways drive distraction-induced enterogenesis.

Time- and segment-related changes of postresected intestine: a 4-dimensional model of intestinal adaptation

OBJECTIVES

The aim of the present study was to investigate the segment- and time-related changes in rat short bowel syndrome and construct a 4-dimensional (4D) geometrical model of intestinal adaptation.

METHODS

Sprague-Dawley rats were divided into 3 groups: 2-day, 7-day, and 15-day postresection groups in which 75% of the jejunoileum was removed. Histological and morphometrical parameters in the remaining proximal to distal intestinal segments, from the jejunum to the distal colon, were comparatively evaluated in the groups. The data were used to construct a 4D geometric model in which villi were considered as cylinders, and their surface area was expressed as cylinder lateral area.

RESULTS

Major adaptive changes were observed in the ileum consisting of an increase in both the diameter of base and the height of villi. A parallel reduction in their number/mm was observed. The resulting ileal architecture was characterized by a limited number of large villi. An opposite pattern was observed in the jejunum whose postresection structure consisted of an increased number of villi. No changes were observed in the colon. Postresection restructuring was early and faster in the ileum than in the jejunum resulting in an increase in absorptive area of 81.5% and 22.5% in the ileum and jejunum, respectively.

CONCLUSIONS

Postresection adaptation is intestinal segment-specific because all of the major changes occur in the ileum rather than in the jejunum. Sparing ileal segments during resection may improve the outcome of patients undergoing extensive intestinal resection. Our 4D model can be used to test interventions aimed at optimizing postresection intestinal adaptation.

Intestinal mucosal atrophy and adaptation

Mucosal adaptation is an essential process in gut homeostasis. The intestinal mucosa adapts to a range of pathological conditions including starvation, short-gut syndrome, obesity, and bariatric surgery. Broadly, these adaptive functions can be grouped into proliferation and differentiation. These are influenced by diverse interactions with hormonal, immune, dietary, nervous, and mechanical stimuli. It seems likely that clinical outcomes can be improved by manipulating the physiology of adaptation. This review will summarize current understanding of the basic science surrounding adaptation, delineate the wide range of potential targets for therapeutic intervention, and discuss how these might be incorporated into an overall treatment plan. Deeper insight into the physiologic basis of adaptation will identify further targets for intervention to improve clinical outcomes.