Cadherin-11 Is a Regulator of Intestinal Fibrosis

Pdgfrα+ stromal cells, a key regulator for tissue homeostasis and dysfunction in distinct organs

Pdgfrα+ stromal cells are a group of cells specifically expressing Pdgfrα, which may be mentioned with distinct names in different tissues. Importantly, the findings from numerous studies suggest that these cells share exactly similar biomarkers and properties, show complex functions in regulating the microenvironment, and are critical to tissue regeneration, repair, and degeneration. Comparing the similarities and differences between distinct tissue-resident Pdgfrα+ stromal cells is helpful for us to more comprehensively and deeply understand the behaviors of these cells and to explore some common regulating mechanisms and therapeutical targets. In this review, we summarize previous and current findings on Pdgfrα+ stromal cells in various tissues and discuss the crosstalk between Pdgfrα+ stromal cells and microenvironment.

Anti-fibrotics in inflammatory bowel diseases: Challenges and successes

Stricture formation leading to obstruction in Crohn's disease (CD) remains one of the largest unmet needs in the field of inflammatory bowel diseases (IBD). Despite this need no selective anti-stricture drug has been approved for use in CD patients. This contrasts with other fibrotic diseases, such as in the lung, liver or kidney, where multiple drug development programs crossed the starting line and two anti-fibrotics are now being approved for pulmonary fibrosis. Strictures are composed of a mix of inflammation, excessive deposition of extracellular matrix (ECM) and smooth muscle hyperplasia, likely all ultimately being responsible for the luminal narrowing driving patient symptoms. Our understanding of the pathogenesis of stricturing CD has evolved and indicates a multifactorial process involving immune and non-immune cells and their soluble mediators. This understanding has rendered target pathways for anti-stricture drug development. Significant progress was made in creating consensus definitions and tools to enable clinical trials with two clinical development programs having been conceived to date. In this chapter, we discuss stricture pathogenesis with a focus on the pathways being tested in clinical trials, and clinical trial endpoints developed for this indication.

Ustekinumab affects myofibroblast metabolism to alleviate intestinal fibrosis by targeting KDELC1 in Crohn's disease through multi-machine learning combined with single-cell sequencing analysis

Background

Ustekinumab (UST), a biologic against interleukin (IL)-12/23, is commonly used to treat Crohn's disease (CD). Myofibroblast (MF) is known as one of the most important factors causing intestinal fibrosis, and UST has been reported to alleviate this condition. However, the genetic mechanisms underlying UST's effects on CD remain unclear. This study uses bioinformatics tools to analyze the genes and potential pathways affected by UST in CD, with a focus on its anti-fibrosis effects, providing insights into new therapeutic targets.

Methods

The data downloaded from the Gene Expression Omnibus (GEO) database were analyzed to screen for differentially expressed genes (DEGs). Various machine learning strategies, including the least absolute shrinkage and selection operator (LASSO), support vector machine (SVM), and random forest (RF), were employed to screen for key genes among the DEGs. Functional and pathway enrichment analyses were conducted, and key genes associated with myofibroblast (MF) activity were screened. Finally, endoscopic surgical specimens from CD patients and healthy participants were collected to assess the expression levels of collagen and key genes in intestinal tissues using hematoxylin-eosin (H&E), Masson staining, and immunohistochemistry.

Results

A total of 1,341 DEGs associated with CD were identified. Among them, 738 genes showed low expression in healthy populations but high expression in patients with CD, reduced expression after the treatment of UST. In contrast, 603 genes exhibited high expression in healthy individuals, showed low expression in CD patients, and increased expression after UST treatment. Functional and pathway analysis showed that DEGs were mainly concentrated in response to foreign biological stimuli and bacterial-derived molecules. DEGs are mainly enriched in chemokines, TNF, IL-17, and other signaling pathways. Seven key genes were identified: NCRNA00236, LOC730101, ORP3, XG, UBFD1, KDELC1, and RBP7. Single-cell analysis revealed that KDELC1 was closely related to MF activity. MFs with high KDELC1 expression were significantly enriched in biological functions, signaling pathways, and metabolic processes that promote fibrosis. The experiment showed that UST treatment helped maintain the integrity of intestinal tissue structure, reducing the expression levels of collagen I, KDELC1, and the severity of intestinal fibrosis. The functional and pathway analysis reiterated that DEGs were largely focused on responses to foreign biological stimuli and bacterial-derived molecules, as well as signaling pathways such as chemokines, TNF, and IL-17. Of the identified genes, KDELC1 showed a particularly strong correlation with MF activity in single-cell analysis (R = 0.33, p = 3.2e-07). MFs with high KDELC1 expression were closely linked to pathways promoting fibrosis progression, including TGF-β, epithelial-mesenchymal transformation, TNF/NF-κB, and related metabolic pathways such as vitamin B6 and arginine.

Conclusion

KDELC1 plays a key role in regulating multiple biological functions, including signaling pathways related to MF. UST alleviates intestinal fibrosis by targeting KDELC1, thereby influencing intramuscular fat metabolism and intercellular communication.

Intestinal Stromal Cells in the Turmoil of Inflammation and Defective Connective Tissue Remodeling in Inflammatory Bowel Disease

In steady state, intestinal subepithelial myofibroblasts form a thin layer below the basement membrane. Unlike the rest of the stromal cells in the lamina propria, they express tensile proteins, guide epithelial regeneration, and sense luminal microbiota. Upon inflammation in inflammatory bowel disease (IBD), they express activation markers, accept trophic signaling by infiltrating neutrophils and macrophages, and are activated by cytokines from helper T cells to produce a narrow spectrum of cytokines and a wider spectrum of chemokines, attract cells of innate and adaptive immunity, orchestrate inflammatory responses, and qualitatively and quantitatively modify the extracellular matrix. Thus, beyond being structural tissue components, they assume active roles in the pathogenesis of complicated IBD. Discrimination between myofibroblasts and fibroblasts may be an oversimplification in light of single-cell sequencing data unveiling the complexity of multiple phenotypes of stromal cells with distinct roles and plasticity. Spatial transcriptomics revealed distinct phenotypes by histologic localization and, more intriguingly, the assembly of mucosal neighborhoods that support spatially distinct functions. Current IBD treatments target inflammation but fail in fibrostenotic or fistulizing disease. Baseline and recent findings on stromal cells, molecules, and pathways involved in disrupted extracellular matrix homeostasis are reviewed to provide relevant pharmacologic targets.

Preventing fibrosis in IBD: update on immune pathways and clinical strategies

INTRODUCTION

Intestinal fibrosis is a common and serious complication of inflammatory bowel diseases (IBD) driving stricture formation in Crohn's disease patients and leading to submucosal damage in ulcerative colitis. Recent studies provided novel insights into the role of immune and nonimmune components in the pathogenesis of intestinal fibrosis. Those new findings may accelerate the development of anti-fibrotic treatment in IBD patients.

AREAS COVERED

This review is designed to cover the recent progress in mechanistic research and therapeutic developments on intestinal fibrosis in IBD patients, including new cell clusters, cytokines, proteins, microbiota, creeping fat, and anti-fibrotic therapies.

EXPERT OPINION

Due to the previously existing major obstacle of missing consensus on stricture definitions and the absence of clinical trial endpoints, testing of drugs with an anti-fibrotic mechanism is just starting in stricturing Crohn's disease (CD). A biomarker to stratify CD patients at diagnosis without any complications into at-risk populations for future strictures would be highly desirable. Further investigations are needed to identify novel mechanisms of fibrogenesis in the intestine that are targetable and ideally gut specific.

Fibrosis in IBD: from pathogenesis to therapeutic targets

BACKGROUND

Intestinal fibrosis resulting in stricture formation and obstruction in Crohn's disease (CD) and increased wall stiffness leading to symptoms in ulcerative colitis (UC) is among the largest unmet needs in inflammatory bowel disease (IBD). Fibrosis is caused by a multifactorial and complex process involving immune and non-immune cells, their soluble mediators and exposure to luminal contents, such as microbiota and environmental factors. To date, no antifibrotic therapy is available. Some progress has been made in creating consensus definitions and measurements to quantify stricture morphology for clinical practice and trials, but approaches to determine the degree of fibrosis within a stricture are still lacking.

OBJECTIVE

We herein describe the current state of stricture pathogenesis, measuring tools and clinical trial endpoints development.

DESIGN

Data presented and discussed in this review derive from the past and recent literature and the authors' own research and experience.

RESULTS AND CONCLUSIONS

Significant progress has been made in better understanding the pathogenesis of fibrosis, but additional studies and preclinical developments are needed to define specific therapeutic targets.

Tissue markers may predict treatment response to antitumor necrosis factor-α agents in children with Crohn's disease

OBJECTIVES

Patients with moderate-severe Crohn's disease (CD) who are treated with antitumor necrosis factor alpha (TNF-α) agents may be subjected to primary nonresponse or partial response. We aimed to identify tissue markers that may predict response to these agents.

METHODS

Pediatric patients (6-18 years) with either ileal or ileo-colonic CD who were treated with anti-TNF-α were stratified into three different groups based on their overall response to therapy at the end of induction including clinical and laboratory parameters (group 1-full responders [FR], group 2-partial responders [PR], group 3-nonresponders [NR]). Seven tissue markers (fibronectin, interleukin [IL]-23R, IL-23, TNF-α, collagen-III, IL-13R, and hypoxia-inducible factors [HIF]-1α) were evaluated. Immunofluorescence (IF) analyses were performed on biopsies from the terminal ileum, which were retrieved up to 6 months before treatment initiation.

RESULTS

Twenty-six CD patients (16 [61.5%] males; age 13.9 ± 2.9 years), including 8 (30.8%) with ileal disease and 18 (69.2%) with ileo-colonic disease, were enrolled. Terminal ileum biopsies from nine patients from group 1, nine from group 2, and eight from group 3 were evaluated. Three antibodies were found to be significantly different between NR and FR groups; Collagen III and fibronectin stains were significantly more prominent in NR patients, while TNF-α stain was significantly more pronounced in FR, p < 0.05 for each. PR could not have been predicted with neither of markers.

CONCLUSIONS

Decreased tissue IF intensity of fibronectin and collagen III and increased intensity of TNF-α may predict response to anti-TNF-α treatment.

Cdh11: Roles in different diseases and potential value in disease diagnosis and treatment

Cadherin is a homophilic, Ca2+-dependent cell adhesion glycoprotein that mediates cell-cell adhesion. Among them, Cadherin-11 (CDH11), as a classical cadherin, participates in and influences many crucial aspects of human growth and development. Furthermore, The involvement of CDH11 has been identified in an increasing number of diseases, primarily including various tumorous diseases, fibrotic diseases, autoimmune diseases, neurodevelopmental disorders, and more. In various tumorous diseases, CDH11 acts not only as a tumor suppressor but can also promote migration and invasion of certain tumors through various mechanisms. Likewise, in non-tumorous diseases, CDH11 remains a pivotal factor in disease progression. In this context, we summarize the specific functionalities and mechanisms of CDH11 in various diseases, aiming to gain a more comprehensive understanding of the potential value of CDH11 in disease diagnosis and treatment. This endeavor seeks to provide more effective diagnostic and therapeutic strategies for clinical management across diverse diseases.

Stricturing Crohn's Disease Single-Cell RNA Sequencing Reveals Fibroblast Heterogeneity and Intercellular Interactions

BACKGROUND & AIMS

Fibroblasts play a key role in stricture formation in Crohn's disease (CD) but understanding its pathogenesis requires a systems-level investigation to uncover new treatment targets. We studied full-thickness CD tissues to characterize fibroblast heterogeneity and function by generating the first single-cell RNA sequencing (scRNAseq) atlas of strictured bowel and providing proof of principle for therapeutic target validation.

METHODS

We performed scRNAseq of 13 fresh full-thickness CD resections containing noninvolved, inflamed nonstrictured, and strictured segments as well as 7 normal non-CD bowel segments. Each segment was separated into mucosa/submucosa or muscularis propria and analyzed separately for a total of 99 tissue samples and 409,001 cells. We validated cadherin-11 (CDH11) as a potential therapeutic target by using whole tissues, isolated intestinal cells, NanoString nCounter, next-generation sequencing, proteomics, and animal models.

RESULTS

Our integrated dataset revealed fibroblast heterogeneity in strictured CD with the majority of stricture-selective changes detected in the mucosa/submucosa, but not the muscle layer. Cell-cell interaction modeling revealed CXCL14+ as well as MMP/WNT5A+ fibroblasts displaying a central signaling role in CD strictures. CDH11, a fibroblast cell-cell adhesion molecule, was broadly expressed and up-regulated, and its profibrotic function was validated using NanoString nCounter, RNA sequencing, tissue target expression, in vitro gain- and loss-of-function experiments, proteomics, and knock-out and antibody-mediated CDH11 blockade in experimental colitis.

CONCLUSIONS

A full-thickness bowel scRNAseq atlas revealed previously unrecognized fibroblast heterogeneity and interactions in CD strictures and CDH11 was validated as a potential therapeutic target. These results provide a new resource for a better understanding of CD stricture formation and open potential therapeutic developments. This work has been posted as a preprint on Biorxiv under doi: 10.1101/2023.04.03.534781.

Novel approaches to target fibroblast mechanotransduction in fibroproliferative diseases

The ability of cells to sense and respond to changes in mechanical environment is vital in conditions of organ injury when the architecture of normal tissues is disturbed or lost. Among the various cellular players that respond to injury, fibroblasts take center stage in re-establishing tissue integrity by secreting and organizing extracellular matrix into stabilizing scar tissue. Activation, activity, survival, and death of scar-forming fibroblasts are tightly controlled by mechanical environment and proper mechanotransduction ensures that fibroblast activities cease after completion of the tissue repair process. Conversely, dysregulated mechanotransduction often results in fibroblast over-activation or persistence beyond the state of normal repair. The resulting pathological accumulation of extracellular matrix is called fibrosis, a condition that has been associated with over 40% of all deaths in the industrialized countries. Consequently, elements in fibroblast mechanotransduction are scrutinized for their suitability as anti-fibrotic therapeutic targets. We review the current knowledge on mechanically relevant factors in the fibroblast extracellular environment, cell-matrix and cell-cell adhesion structures, stretch-activated membrane channels, stress-regulated cytoskeletal structures, and co-transcription factors. We critically discuss the targetability of these elements in therapeutic approaches and their progress in pre-clinical and/or clinical trials to treat organ fibrosis.

Effect of Cadherin-11 on the Proliferation, Migration, and ECM Synthesis of Chondrocyte

Nonsyndromic microtia is a kind of congenital ear malformation with unclear pathogenic genes. Cadherin-11 (CDH11, OB-cadherin) is a member of the cadherin family, which has been demonstrated to play important roles in controlling morphogenesis and cell biological characteristics during multiple developmental processes. In the present study, we found low expression of CDH11 in microtia cartilage compared with the normal one for the first time. For a more comprehensive and in-depth understanding of CDH11 in microtia development, we performed both gain- and loss-of-function experiments to detect the effect of CDH11 on chondrocytes. CDH11 promoted chondrocyte proliferation by increasing S-phase cell numbers and increasing cell migration, which is important for tissue morphogenesis. Additionally, knockdown of CDH11 in chondrocytes reduced the quality of engineered cartilage by decreasing the key transcription factors of chondrogenesis, SOX9 expression, and cartilage ECM production, including collagen type II (COL2A) and elastin (ELN), compared to the control group. Furthermore, RNA-Seq on CDH11 knockdown chondrocytes showed that it was highly related to HOX family genes, which have been reported to be important regulatory genes patterning craniofacial tissue formation. This study identified CDH11 as a candidate pathogenic gene of microtia and supported the potential key role of CDH11 in craniofacial malformations.

Stricturing Crohn's disease single-cell RNA sequencing reveals fibroblast heterogeneity and intercellular interactions

Background

Fibroblasts play a key role in stricture formation in Crohn's disease (CD) but understanding it's pathogenesis requires a systems-level investigation to uncover new treatment targets. We studied full thickness CD tissues to characterize fibroblast heterogeneity and function by generating the first single cell RNA sequencing (scRNAseq) atlas of strictured bowel and providing proof of principle for therapeutic target validation.

Methods

We performed scRNAseq of 13 fresh full thickness CD resections containing non-involved, inflamed non-strictured, and strictured segments as well as 7 normal non-CD bowel segments. Each segment was separated into mucosa/submucosa or muscularis propria and analyzed separately for a total of 99 tissue samples and 409,001 cells. We validated cadherin-11 (CDH11) as a potential therapeutic target by using whole tissues, isolated intestinal cells, NanoString nCounter, next generation sequencing, proteomics and animal models.

Results

Our integrated dataset revealed fibroblast heterogeneity in strictured CD with the majority of stricture-selective changes detected in the mucosa/submucosa, but not the muscle layer. Cell-cell interaction modeling revealed CXCL14+ as well as MMP/WNT5A+ fibroblasts displaying a central signaling role in CD strictures. CDH11, a fibroblast cell-cell adhesion molecule, was broadly expressed and upregulated, and its pro-fibrotic function was validated by NanoString nCounter, RNA sequencing, tissue target expression, in vitro gain- and loss-of-function experiments, proteomics, and two animal models of experimental colitis.

Conclusion

A full-thickness bowel scRNAseq atlas revealed previously unrecognized fibroblast heterogeneity and interactions in CD strictures and CDH11 was validated as a potential therapeutic target. These results provide a new resource for a better understanding of CD stricture formation and opens potential therapeutic developments.

Regulation and functions of cell division in the intestinal tissue

In multicellular organisms, epithelial cells are key elements of tissue organization. In developing epithelial tissues, cellular proliferation and differentiation are under the tight regulation of morphogenetic programs to ensure correct organ formation and functioning. In these processes, proliferation rates and division orientation regulate the speed, timing and direction of tissue expansion but also its proper patterning. Moreover, tissue homeostasis relies on spatio-temporal modulations of daughter cell behavior and arrangement. These aspects are particularly crucial in the intestine, which is one of the most proliferative tissues in adults, making it a very attractive adult organ system to study the role of cell division on epithelial morphogenesis and organ function. Although epithelial cell division has been the subject of intense research for many years in multiple models, it still remains in its infancy in the context of the intestinal tissue. In this review, we focus on the current knowledge on cell division and regulatory mechanisms at play in the intestinal epithelial tissue, as well as their importance in developmental biology and physiopathology.

Inflammatory bowel disease-associated intestinal fibrosis

Fibrosis is characterized by a proliferation of fibroblasts and excessive extracellular matrix following chronic inflammation, and this replacement of organ tissue with fibrotic tissue causes a loss of function. Inflammatory bowel disease (IBD) is a chronic inflammation of the gastrointestinal tract, and intestinal fibrosis is common in IBD patients, resulting in several complications that require surgery, such as a stricture or penetration. This review describes the pathogenesis and various factors involved in intestinal fibrosis in IBD, including cytokines, growth factors, epithelial-mesenchymal and endothelial-mesenchymal transitions, and gut microbiota. Furthermore, histopathologic findings and scoring systems used for stenosis in IBD are discussed, and differences in the fibrosis patterns of ulcerative colitis and Crohn's disease are compared. Biomarkers and therapeutic agents targeting intestinal fibrosis are briefly mentioned at the end.

Myofibroblast specific targeting approaches to improve fibrosis treatment

Fibrosis has been shown to develop in individuals with underlying health conditions, especially chronic inflammatory diseases. Fibrosis is often diagnosed in various organs, including the liver, lungs, kidneys, heart, and skin, and has been described as excessive accumulation of extracellular matrix that can affect specific organs in the body or systemically throughout the body. Fibrosis as a chronic condition can result in organ failure and result in death of the individual. Understanding and identification of specific biomarkers associated with fibrosis has emerging potential in the development of diagnosis and targeting treatment modalities. Therefore, in this review, we will discuss multiple signaling pathways such as TGF-β, collagen, angiotensin, and cadherin and outline the chemical nature of the different signaling pathways involved in fibrogenesis as well as the mechanisms. Although it has been well established that TGF-β is the main catalyst initiating and driving multiple pathways for fibrosis, targeting TGF-β can be challenging as this molecule regulates essential functions throughout the body that help to keep the body in homeostasis. We also discuss collagen, angiotensin, and cadherins and their role in fibrosis. We comprehensively discuss the various delivery systems used to target collagen, angiotensin, and cadherins to manage fibrosis. Nevertheless, understanding the steps by which this molecule drives fibrosis development can aid in the development of specific targets of its cascading mechanism. Throughout the review, we will demonstrate the mechanism of fibrosis targeting to improve targeting delivery and therapy.

Upregulation of cadherin-11 contributes to cholestatic liver fibrosis

Importance

Cadherin-11 (CDH11), a cell-to-cell adhesion molecule, is implicated in the fibrotic process of several organs. Biliary atresia (BA) is a common cholestatic liver disease featuring cholestasis and progressive liver fibrosis in children. Cholestatic liver fibrosis may progress to liver cirrhosis and lacks effective therapeutic strategies. Currently, the role of CDH11 in cholestatic liver fibrosis remains unclear.

Objective

This study aimed to explore the functions of CDH11 in cholestatic liver fibrosis.

Methods

The expression of CDH11 in BA livers was evaluated by database analysis and immunostaining. Seven BA liver samples were used for immunostaining. The wild type (Wt) and CDH11 knockout (CDH11-/- ) mice were subjected to bile duct ligation (BDL) to induce cholestatic liver fibrosis. The serum biochemical analysis, liver histology, and western blotting were used to assess the extent of liver injury and fibrosis as well as activation of transforming growth factor-β (TGF-β)/Smad pathway. The effect of CDH11 on the activation of hepatic stellate cell line LX-2 cells was investigated.

Results

Analysis of public RNA-seq datasets showed that CDH11 expression levels were significantly increased in livers of BA, and CDH11 was correlated with liver fibrosis in BA. BDL-induced liver injury and liver fibrosis were attenuated in CDH11-/- mice compared to Wt mice. The protein expression levels of phosphorylated Smad2/3 were decreased in livers of CDH11-/- BDL mice compared to Wt BDL mice. CDH11 knockdown inhibited the activation of LX-2 cells.

Interpretation

CDH11 plays an important role in cholestatic liver fibrosis and may represent a potential therapeutic target for cholestatic liver disease, such as BA.

Cadherin-11 Regulates Macrophage Development and Function

Cadherin-11 (CDH11) is a cell-cell adhesion protein that has previously been reported to play an important role in the pathogenesis of pulmonary fibrosis. It is expressed on macrophages in the fibrotic lung. However, the role of CDH11 on macrophage biology has not yet been studied. We show using immunophenotypic analyses that Cdh11^-/- mice have fewer recruited monocyte-derived macrophages and Ly6C^hi monocytes in the lungs compared to wild-type mice in the intraperitoneal bleomycin-induced pulmonary fibrosis model. Additionally, fewer Ly6C^hi monocytes were detected in the bone marrow and peripheral blood of naive Cdh11^-/- mice. Given that macrophages are derived from monocytes, we investigated the precursors of the monocyte/macrophage lineage in the bone marrow. We found increased numbers of CMPs and reduced numbers of GMPs and MPs/cMoPs in Cdh11^-/- mice compared to wild-type mice, suggesting decreased differentiation towards the myeloid lineage in Cdh11^-/- mice. Furthermore, we show using bone marrow cells that loss of CDH11 impaired monocyte to macrophage differentiation. We also demonstrate that CDH11 deficiency repressed the M2 program and impaired the phagocytic function of bone marrow-derived macrophages. Overall, our findings demonstrate a role for CDH11 in macrophage development, M2 polarization, and phagocytic function.

Revisiting fibrosis in inflammatory bowel disease: the gut thickens

Intestinal fibrosis, which is usually the consequence of chronic inflammation, is a common complication of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis. In the past few years, substantial advances have been made in the areas of pathogenesis, diagnosis and management of intestinal fibrosis. Of particular interest have been inflammation-independent mechanisms behind the gut fibrotic process, genetic and environmental risk factors (such as the role of the microbiota), and the generation of new in vitro and in vivo systems to study fibrogenesis in the gut. A huge amount of work has also been done in the area of biomarkers to predict or detect intestinal fibrosis, including novel cross-sectional imaging techniques. In parallel, researchers are embarking on developing and validating clinical trial end points and protocols to test novel antifibrotic agents, although no antifibrotic therapies are currently available. This Review presents the state of the art on the most recently identified pathogenic mechanisms of this serious IBD-related complication, focusing on possible targets of antifibrotic therapies, management strategies, and factors that might predict fibrosis progression or response to treatment.

From the Matrix to the Nucleus and Back: Mechanobiology in the Light of Health, Pathologies, and Regeneration of Oral Periodontal Tissues

Among oral tissues, the periodontium is permanently subjected to mechanical forces resulting from chewing, mastication, or orthodontic appliances. Molecularly, these movements induce a series of subsequent signaling processes, which are embedded in the biological concept of cellular mechanotransduction (MT). Cell and tissue structures, ranging from the extracellular matrix (ECM) to the plasma membrane, the cytosol and the nucleus, are involved in MT. Dysregulation of the diverse, fine-tuned interaction of molecular players responsible for transmitting biophysical environmental information into the cell's inner milieu can lead to and promote serious diseases, such as periodontitis or oral squamous cell carcinoma (OSCC). Therefore, periodontal integrity and regeneration is highly dependent on the proper integration and regulation of mechanobiological signals in the context of cell behavior. Recent experimental findings have increased the understanding of classical cellular mechanosensing mechanisms by both integrating exogenic factors such as bacterial gingipain proteases and newly discovered cell-inherent functions of mechanoresponsive co-transcriptional regulators such as the Yes-associated protein 1 (YAP1) or the nuclear cytoskeleton. Regarding periodontal MT research, this review offers insights into the current trends and open aspects. Concerning oral regenerative medicine or weakening of periodontal tissue diseases, perspectives on future applications of mechanobiological principles are discussed.

Novel mechanisms and clinical trial endpoints in intestinal fibrosis

The incidence of inflammatory bowel diseases (IBD) worldwide has resulted in a global public health challenge. Intestinal fibrosis leading to stricture formation and bowel obstruction is a frequent complication in Crohn's disease (CD), and the lack of anti-fibrotic therapies makes elucidation of fibrosis mechanisms a priority. Progress has shown that mesenchymal cells, cytokines, microbial products, and mesenteric adipocytes are jointly implicated in the pathogenesis of intestinal fibrosis. This recent information puts prevention or reversal of intestinal strictures within reach through innovative therapies validated by reliable clinical trial endpoints. Here, we review the role of immune and non-immune components of the pathogenesis of intestinal fibrosis, including new cell clusters, cytokine networks, host-microbiome interactions, creeping fat, and their translation for endpoint development in anti-fibrotic clinical trials.

Molecular targets and the use of biologics in the management of small bowel fibrosis in inflammatory bowel disease

PURPOSE OF REVIEW

Small bowel fibrosis is a significant burden on Crohn's disease patients with limited effective medical treatments that then requires surgery. A better understanding of the molecular mechanisms causing fibrosis and the evidence of benefit of available biologics will potentially lighten this burden and avoid the need for surgery.

RECENT FINDINGS

Transforming growth factor-beta and it's associated pathways remain the central cog in the wheel of fibrosis formation. Various new enzymes, cellular pathways, interleukins and molecules have been associated with beneficial modification of the fibrotic process. Licensed biologics such as antitumour necrosis factors continue to show evidence of efficacy in the treatment of fibrostenotic small bowel disease as well as the newer biologics ustekinumab and vedolizumab.

SUMMARY

Fibrostenotic disease of the small bowel is a significant and common debilitating complication in Crohn's disease patients. Multiple new molecular targets have been identified that may prove to become effective therapies in future. Antitumour necrosis factors remain the treatment with the best available evidence to date in fibrostenotic Crohn's disease.

Fibrotic Strictures in Crohn's Disease: Mechanisms and Predictive Factors

Fibrotic strictures are one of the most severe complications of Crohn's Disease (CD). They occur in about 50% of patients at five years and in 70% at ten years of the diagnosis. The only treatment available for symptomatic fibrotic strictures is surgical resection and endoscopic dilation. Both strategies are associated with a high rate of recurrence, and with multiple surgical resections, which pose the threat of surgical morbidity and short bowel syndrome. Therefore, it is crucial to identify, early, the patients more prone to develop intestinal fibrosis to intensify follow-ups, switch to more aggressive treatments, and suggest lifestyle modifications. Scarce data are available concerning biomarkers and genetic determinants to predict which patient will develop intestinal fibrosis. Biologic or clinical markers would be useful to determine this subgroup of CD patients and to predict the onset of intestinal fibrosis and, ideally, its severity. Furthermore, the identification of environmental risk factors may suggest lifestyle changes aimed at modifying the natural course, thus decreasing the risk of complicated CD. In this review, we will critically revise clinical, environmental, genetic, and serologic factors that have been associated with a complicated CD course with a particular focus on the fibrostenosing phenotype and their possible implications as predictive factors of intestinal fibrosis.

Lactic acid promotes metastatic niche formation in bone metastasis of colorectal cancer

BACKGROUND

To investigate the effect of lactic acid (LA) on the progression of bone metastasis from colorectal cancer (CRC) and its regulatory effects on primary CD115 (+) osteoclast (OC) precursors.

METHODS

The BrdU assay, Annexin-V/PI assay, TRAP staining and immunofluorescence were performed to explore the effect of LA on the proliferation, apoptosis and differentiation of OC precursors in vitro and in vivo. Flow cytometry was performed to sort primary osteoclast precursors and CD4(+) T cells and to analyze the change in the expression of target proteins in osteoclast precursors. A recruitment assay was used to test how LA and Cadhein-11 regulate the recruitment of OC precursors. RT-PCR and Western blotting were performed to analyze the changes in the mRNA and protein expression of genes related to the PI3K-AKT pathway and profibrotic genes. Safranin O-fast green staining, H&E staining and TRAP staining were performed to analyze the severity of bone resorption and accumulation of osteoclasts.

RESULTS

LA promoted the expression of CXCL10 and Cadherin-11 in CD115(+) precursors through the PI3K-AKT pathway. We found that CXCL10 and Cadherin-11 were regulated by the activation of CREB and mTOR, respectively. LA-induced overexpression of CXCL10 in CD115(+) precursors indirectly promoted the differentiation of osteoclast precursors through the recruitment of CD4(+) T cells, and the crosstalk between these two cells promoted bone resorption in bone metastasis from CRC. On the other hand, Cadherin-11 mediated the adhesion between osteoclast precursors and upregulated the production of specific collagens, especially Collagen 5, which facilitated fibrotic changes in the tumor microenvironment. Blockade of the PI3K-AKT pathway efficiently prevented the progression of bone metastasis caused by lactate.

CONCLUSION

LA promoted metastatic niche formation in the tumor microenvironment through the PI3K-AKT pathway. Our study provides new insight into the role of LA in the progression of bone metastasis from CRC. Video Abstract.

Research progress in the role and mechanism of Cadherin-11 in different diseases

Cadherin is an important cell-cell adhesion molecule, which mediates intercellular adhesion through calcium dependent affinity interaction. Cadherin-11 (CDH11, OB-cadherin) is a member of cadherin family, and its gene is situated on chromosome 16q22.1. Increasing lines of researches have proved that CDH11 plays important roles in the occurrence and development of a lot of diseases, such as tumors, arthritis and so on. CDH11 often leads to promoter methylation inactivation, which can induce cancer cell apoptosis, suppress cell motility and invasion, and can inhibit cancer through Wnt/β-catenin, AKT/Rho A and NF-κB signaling pathways. This review focused on the current knowledge of CDH11, including its function and mechanism in different diseases. In this article, we aimed to have a more comprehensive and in-depth understanding of CDH11 and to provide new ideas for the treatment of some diseases.

Mechanism of fibrosis and stricture formation in Crohn's disease

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract that leads to substantial suffering for millions of patients. In some patients, the chronic inflammation leads to remodelling of the extracellular matrix and fibrosis. Fibrosis, in combination with expansion of smooth muscle layers, leaves the bowel segment narrowed and stiff resulting in strictures, which often require urgent medical intervention. Although stricture development is associated with inflammation in the affected segment, anti‐inflammatory therapies fall far short of treating strictures. At best, current therapies might allow some patients to avoid surgery in a shorter perspective and no anti‐fibrotic therapy is yet available. This likely relates to our poor understanding of the mechanism underlying stricture development. Chronic inflammation is a prerequisite, but progression to strictures involves changes in fibroblasts, myofibroblasts and smooth muscle cells in a poorly understood interplay with immune cells and environmental cues. Much of the experimental evidence available is from animal models, cell lines or non‐strictured patient tissue. Accordingly, these limitations create the basis for many previously published reviews covering the topic. Although this information has contributed to the understanding of fibrotic mechanisms in general, in the end, data must be validated in strictured tissue from patients. As stricture formation is a serious complication of CD, we endeavoured to summarize findings exclusively performed using strictured tissue from patients. Here, we give an update of the mechanism driving this serious complication in patients, and how the strictured tissue differs from adjacent unaffected tissue and controls.

No effect of a liquid diet in the management of patients with stricturing Crohn's disease

PURPOSE

Patients with stricturing Crohn's disease (CD) may experience episodes of intestinal sub-occlusions, which in many cases lead to surgery. The aim of this study was to examine whether adding a liquid diet to medical therapy could improve the management of patients with stricturing CD.

METHODS

Medical records of CD outpatients with a small bowel stricture, either receiving (group 1) or not (group 2) a 24-h liquid diet every 10-14 days, were retrospectively analyzed. Number of sub-occlusive episodes, frequency, and timing of intestinal resections for strictures were analyzed.

RESULTS

During the 12-month follow-up, there was no significant difference in the occurrence of new sub-occlusive episodes between the 2 groups (10/37 patients (27%) in group 1 vs 9/45 patients (20%) in group 2). Similarly, the number of patients undergoing bowel resections for sub-occlusive episodes non-responsive to medical therapy did not statistically differ between the two groups (9 patients (24.3%) in group 1 vs 7 patients (15.5%) in group 2). In group 1, surgeries were equally distributed along the 12-months of follow-up, while 85.7% of patients in group 2 underwent intestinal resection within the first 3 months of follow-up.

CONCLUSION

Adding a liquid diet to medical therapy does not help management of patients with stricturing CD.