Immune Cell Populations within the Duodenal Mucosa of Dogs with Enteropathies

Epithelial barrier dysfunction and associated diseases in companion animals: Differences and similarities between humans and animals and research needs

Since the 1960s, more than 350,000 new chemicals have been introduced into the lives of humans and domestic animals. Many of them have become part of modern life and some are affecting nature as pollutants. Yet, our comprehension of their potential health risks for both humans and animals remains partial. The "epithelial barrier theory" suggests that genetic predisposition and exposure to diverse factors damaging the epithelial barriers contribute to the emergence of allergic and autoimmune conditions. Impaired epithelial barriers, microbial dysbiosis, and tissue inflammation have been observed in a high number of mucosal inflammatory, autoimmune and neuropsychiatric diseases, many of which showed increased prevalence in the last decades. Pets, especially cats and dogs, share living spaces with humans and are exposed to household cleaners, personal care products, air pollutants, and microplastics. The utilisation of cosmetic products and food additives for pets is on the rise, unfortunately, accompanied by less rigorous safety regulations than those governing human products. In this review, we explore the implications of disruptions in epithelial barriers on the well-being of companion animals, drawing comparisons with humans, and endeavour to elucidate the spectrum of diseases that afflict them. In addition, future research areas with the interconnectedness of human, animal, and environmental well-being are highlighted in line with the "One Health" concept.

Single cell transcriptomic analysis of the canine duodenum in chronic inflammatory enteropathy and health

Chronic inflammatory enteropathy (CIE) is a common condition in dogs causing recurrent or persistent gastrointestinal clinical signs. Pathogenesis is thought to involve intestinal mucosal inflammatory infiltrates, but histopathological evaluation of intestinal biopsies from dogs with CIE fails to guide treatment, inform prognosis, or correlate with clinical remission. We employed single-cell RNA sequencing to catalog and compare the diversity of cells present in duodenal mucosal endoscopic biopsies from 3 healthy dogs and 4 dogs with CIE. Through characterization of 35,668 cells, we identified 31 transcriptomically distinct cell populations, including T cells, epithelial cells, and myeloid cells. Both healthy and CIE samples contributed to each cell population. T cells were broadly subdivided into GZMAhigh (putatively annotated as tissue resident) and IL7Rhigh (putatively annotated as non-resident) T cell categories, with evidence of a skewed proportion favoring an increase in the relative proportion of IL7Rhigh T cells in CIE dogs. Among the myeloid cells, neutrophils from CIE samples exhibited inflammatory (SOD2 and IL1A) gene expression signatures. Numerous differentially expressed genes were identified in epithelial cells, with gene set enrichment analysis suggesting enterocytes from CIE dogs may be undergoing stress responses and have altered metabolic properties. Overall, this work reveals the previously unappreciated cellular heterogeneity in canine duodenal mucosa and provides new insights into molecular mechanisms which may contribute to intestinal dysfunction in CIE. The cell type gene signatures developed through this study may also be used to better understand the subtleties of canine intestinal physiology in health and disease.

Pro-inflammatory cytokine expression and the STAT1/3 pathway in canine chronic enteropathy and intestinal T-cell lymphoma

The accumulation of intraepithelial lymphocytes (IELs) is a histopathological feature of canine chronic enteropathy (CE), and IELs are considered the cells of origin of intestinal T-cell lymphoma (ITCL). However, the pathogenic mechanism of IEL activation in CE remains unclear. This study hypothesized that the expression of proinflammatory cytokines, associated with cytotoxic T/NK-cell activation, is upregulated in CE and ITCL, and examined the expression of IFN-γ, IL-2, IL-12p35, IL-12p40, IL-15, and IL-21 and the downstream signal transducers and activators of transcription (STAT) pathway in the duodenal mucosa of dogs without lesions (n = 11; NC), with IEL-CE (n = 19; CE without intraepithelial lymphocytosis), IEL+CE (n = 29; CE with intraepithelial lymphocytosis), and with ITCL (n = 60). Quantitative polymerase chain reaction (PCR) revealed that IFN-γ and IL-21 were higher in IEL+CE than in IEL-CE or NC. Western blot revealed upregulation of STAT1 and STAT3 in IEL+CE. Double-labeling immunohistochemistry revealed a positive correlation between the Ki67 index of CD3+ T-cells and IFN-γ expression levels. Immunohistochemistry revealed a higher ratio of p-STAT1-positive villi in IEL+CE and ITCL than IEL-CE and NC, which positively correlated with IFN-γ expression levels. Among the 60 ITCL cases, neoplastic lymphocytes were immunopositive for p-STAT1 in 28 cases and p-STAT3 in 29 cases. These results suggest that IFN-γ and IL-21 contribute to the pathogenesis of IEL+CE, and IFN-γ may be involved in T-cell activation and mucosal injury in CE. STAT1 and STAT3 activation in ITCL cells suggests a role for the upregulation of the STAT pathway in the pathogenesis of ITCL.

Updating the Classification of Chronic Inflammatory Enteropathies in Dogs

Chronic inflammatory enteropathies (CIEs) in dogs are currently classified based on response to sequential treatment trials into food-responsive (FREs); antibiotic-responsive (AREs); immunosuppressant-responsive (IREs); and non-responsive enteropathies (NREs). Recent studies have reported that a proportion of NRE dogs ultimately respond to further dietary trials and are subsequently misclassified. The FRE subset among CIEs is therefore probably underestimated. Moreover, alterations in the gut microbiota composition and function (dysbiosis) have been shown to be involved in CIE pathogenesis in recent research on dogs. Metronidazole and other antibiotics that have been used for decades for dogs with AREs have been demonstrated to result in increased antimicrobial resistance and deleterious effects on the gut microbiota. As a consequence, the clinical approach to CIEs has evolved in recent years toward the gradual abandonment of the use of antibiotics and their replacement by other treatments with the aim of restoring a diverse and functional gut microbiota. We propose here to refine the classification of canine CIEs by replacing the AREs category with a microbiota-related modulation-responsive enteropathies (MrMREs) category.

Canine chronic enteropathy—Current state-of-the-art and emerging concepts

Over the last decade, chronic inflammatory enteropathies (CIE) in dogs have received great attention in the basic and clinical research arena. The 2010 ACVIM Consensus Statement, including guidelines for the diagnostic criteria for canine and feline CIE, was an important milestone to a more standardized approach to patients suspected of a CIE diagnosis. Great strides have been made since understanding the pathogenesis and classification of CIE in dogs, and novel diagnostic and treatment options have evolved. New concepts in the microbiome-host-interaction, metabolic pathways, crosstalk within the mucosal immune system, and extension to the gut-brain axis have emerged. Novel diagnostics have been developed, the clinical utility of which remains to be critically evaluated in the next coming years. New directions are also expected to lead to a larger spectrum of treatment options tailored to the individual patient. This review offers insights into emerging concepts and future directions proposed for further CIE research in dogs for the next decade to come.

Elucidating the Role of Innate and Adaptive Immune Responses in the Pathogenesis of Canine Chronic Inflammatory Enteropathy-A Search for Potential Biomarkers

Simple Summary

Canine chronic inflammatory enteropathy (CIE) is a chronic disease affecting the small or large intestine and, in some cases, the stomach of dogs. This gastrointestinal disorder is common and is characterized by recurrent vomiting, diarrhea, and weight loss in affected dogs. The pathogenesis of IBD is not completely understood. Similar to human IBD, potential disease factors include genetics, environmental exposures, and dysregulation of the microbiota and the immune response. Some important components of the innate and adaptive immune response involved in CIE pathogenesis have been described. However, the immunopathogenesis of the disease has not been fully elucidated. In this review, we summarized the literature associated with the different cell types and molecules involved in the immunopathogenesis of CIE, with the aim of advancing the search for biomarkers with possible diagnostic, prognostic, or therapeutic utility.

Abstract

Canine chronic inflammatory enteropathy (CIE) is one of the most common chronic gastrointestinal diseases affecting dogs worldwide. Genetic and environmental factors, as well as intestinal microbiota and dysregulated host immune responses, participate in this multifactorial disease. Despite advances explaining the immunological and molecular mechanisms involved in CIE development, the exact pathogenesis is still unknown. This review compiles the latest reports and advances that describe the main molecular and cellular mechanisms of both the innate and adaptive immune responses involved in canine CIE pathogenesis. Future studies should focus research on the characterization of the immunopathogenesis of canine CIE in order to advance the establishment of biomarkers and molecular targets of diagnostic, prognostic, or therapeutic utility.

Nonhypoalbuminemic Inflammatory Bowel Disease in Dogs as Disease Model

BACKGROUND

The incidence of inflammatory bowel disease (IBD) is increasing worldwide, emphasizing the need of relevant models, as dogs spontaneously affected by IBD may be, for better knowledge of the disease's physiopathology.

METHODS

We studied 22 client-owned dogs suffering from IBD without protein loss and 14 control dogs. Biopsies were obtained from the duodenum, ileum, and colon. Inflammatory grade was assessed by histopathology, immunohistochemistry, and chemokine analysis. The expression of Toll-like receptors (TLR) in mucosa was immunohistochemically evaluated. Antibody levels against bacterial ligands (lipopolysaccharide [LPS] and flagellin) were measured in sera using enzyme-linked immunoassay.

RESULTS

Dogs with IBD showed low to severe clinical disease. Histopathologically, the gut of dogs with IBD did not exhibit significant alterations compared with controls except in the colon. The number of CD3+ T lymphocytes was decreased in the ileum and colon of dogs with IBD compared with controls, whereas the numbers of Foxp3+, CD20+, and CD204+ cells were similar in the 2 groups. Three chemokines, but no cytokines, were detected at the protein level in the mucosa, and the disease poorly affected their tissue concentrations. Dogs with IBD exhibited higher serum reactivity against LPS and flagellin than controls but similar immunoreactivity against the receptors TLR4 and TLR5. In addition, TLR2 and TLR9 showed similar expression patterns in both groups of dogs.

CONCLUSIONS

Our data described dysregulated immune responses in dogs affected by IBD without protein loss. Despite fairly homogeneous dog cohorts, we were still faced with interindividual variability, and new studies with larger cohorts are needed to validate the dog as a model.

Genomic association and further characterisation of faecal immunoglobulin A deficiency in German Shepherd dogs

BACKGROUND

Immunoglobulin A (IgA) deficiency, chronic enteropathies and exocrine pancreatic insufficiency (EPI) have a high prevalence in German Shepherd dogs (GSD). This prospective study determined the prevalence of faecal IgA deficiency (IgAD) in GSD and investigated several candidate genes and the canine genome for a region or locus co-segregating with IgAD in GSD. Faecal IgA concentrations were quantified and genomic DNA was extracted from 8 GSD with an undetectable faecal IgA (classified as IgAD) and 80 non-IgAD GSD. The canine minimal screening set II microsatellite markers were genotyped, with evidence of an association at p < 1.0 × 10-3 . Faecal IgA concentrations were also tested for an association with patient clinical and biochemical variables.

RESULTS

Allele frequencies observed using the candidate gene approach were not associated with faecal IgAD in GSD. In the genome-wide association study (GWAS), the microsatellite marker FH2361 on canine chromosome 33 approached statistical significance for a link with IgAD in GSD (p = 1.2 × 10-3 ). A subsequent GWAS in 11 GSD with EPI and 80 control GSD revealed a significant association between EPI and FH2361 (p = 8.2 × 10-4 ).

CONCLUSIONS

The lack of an association with the phenotype of faecal IgAD in GSD using the candidate gene approach and GWAS might suggests that faecal IgAD in GSD is a relative or transient state of deficiency. However, the prevalence of faecal IgAD in GSD appears to be low (<3%). The relationship between faecal IgAD, EPI and loci close to FH2361 on canine chromosome 33 in GSD warrants further investigation.

Isolation and immunophenotyping by flow cytometry of canine peripheral blood and intraepithelial and lamina propria duodenal T lymphocytes

The gut associated lymphoid tissue (GALT) effector sites play a crucial role on the pathogenesis of many immune-mediated gastrointestinal diseases. The lymphocytes at these effector sites are principally T cells which present important morphological, phenotypical and functional differences. Flow cytometry (FC) is one of the most commonly used techniques to characterize intestinal lymphocytes in human and animal models. Published studies with a focus on dogs for intraepithelial lymphocytes (IEL) immunophenotyping exist in very limited numbers. Moreover, no lamina propria lymphocytes (LPL) isolation protocols in the canine species have been described for FC evaluation. In addition to immune intestinal dysregulation, imbalances in the peripheral blood immune system have been described in both human and animal gastrointestinal disorders. The aim of this study was to provide a protocol for canine IEL and LPL isolation for FC immunophenotyping of T cells subsets. Specifically, T helper, T cytotoxic, activated Th and Tc lymphocytes, regulatory, double negative, double positive, IFN-γ and IL-4 producing T cells, and to compare their respective populations between these effector sites and with the blood stream compartment in healthy dogs. The potential relationship of these cells distributions with age, sex and breed was also evaluated. This study included sixteen healthy dogs of different sexes and breeds with a mean age of 4.55 ± 2.93 years old. The selected protocols for the three immune compartments showed proper cell yield, purity, viability, and the absence of phenotypic and functional disturbances. Histologically, an adequate separation of the duodenal epithelium from the lamina propria was also observed. All the proposed T cells subsets were identified in the three immune compartments studied, showing some statistically significant differences in their distributions at these locations that highlight the importance of their individual evaluation. This study provides an adequate method for canine small intestine IEL and LPL isolation for FC immunophenotyping and is key for future studies on the gastrointestinal immune system associated with different canine diseases.

Upregulation of signal transducer and activator of transcription 3 in dogs with chronic inflammatory enteropathies

Background

In inflammatory bowel disease (IBD) in humans, phosphorylated signal transducer and activator of transcription 3 (pSTAT3) is upregulated in mucosal epithelial cells and correlates with clinical severity.

Hypothesis/Objective

To investigate the expression pattern of pSTAT3 in the mucosa of dogs with chronic inflammatory enteropathy (CIE) and explore correlations between its expression and clinical and histopathological severity scoring.

Animals

Twenty‐eight canine CIE patients grouped into food‐responsive enteropathy (FRE;  9), steroid‐responsive enteropathy (SRE;  10), and protein‐losing enteropathy (PLE;  9). Ten healthy beagle dogs served as controls (CO).

Methods

Retrospective case control study. Immunohistochemistry was used to detect pSTAT3 in canine duodenal mucosa samples.

Results

Compared to CO, SRE (P < .001) and PLE (P < .001) dogs had significantly higher pSTAT3 expression in the villus epithelium. The SRE group had a significantly higher expression in the villus lamina propria (VLP) compared to controls (P = .009). In the crypt epithelium (CE), all CIE dogs had significantly higher pSTAT3 expression (FRE, P = .002; SRE, P = .003; PLE, P < .001) compared to CO. In the lamina propria crypt region (CLP), dogs with FRE (P = .04) and SRE (P = .03) had significantly upregulated pSTAT3 compared to controls. A positive correlation was found between canine chronic enteropathy clinical activity index (CCECAI) scoring and pSTAT3 expression for both epithelial (rho = .541; P < .001) and crypt regions (rho = .32; P = .02).

Conclusions and Clinical Importance

pSTAT3 is upregulated in CIE in dogs, correlates with clinical severity, and may be helpful as a clinical marker in dogs with CIE.

Deepening the Mechanisms of Visceral Pain Persistence: An Evaluation of the Gut-Spinal Cord Relationship

The management of visceral pain is a major clinical problem in patients affected by gastrointestinal disorders. The poor knowledge about pain chronicization mechanisms prompted us to study the functional and morphological alterations of the gut and nervous system in the animal model of persistent visceral pain caused by 2,4-dinitrobenzenesulfonic acid (DNBS). This agent, injected intrarectally, induced a colonic inflammation peaking on day 3 and remitting progressively from day 7. In concomitance with bowel inflammation, the animals developed visceral hypersensitivity, which persisted after colitis remission for up to three months. On day 14, the administration of pain-relieving drugs (injected intraperitoneally and intrathecally) revealed a mixed nociceptive, inflammatory and neuropathic pain originating from both the peripheral and central nervous system. At this time point, the colonic histological analysis highlighted a partial restitution of the tunica mucosa, transmural collagen deposition, infiltration of mast cells and eosinophils, and upregulation of substance P (SP)-positive nerve fibers, which were surrounded by eosinophils and MHC-II-positive macrophages. A significant activation of microglia and astrocytes was observed in the dorsal and ventral horns of spinal cord. These results suggest that the persistence of visceral pain induced by colitis results from maladaptive plasticity of the enteric, peripheral and central nervous systems.

Study of Correlations between Clinical Signs and Morphological Features Identified in Dogs Affected with Inflammatory Bowel Disease

This paper evaluates possible relations between the clinical activity and the histopathological findings of the entire intestine in dogs with inflammatory bowel disease (IBD). To perform this study, hospital records of 64 dogs of different sex and breed diagnosed with IBD were evaluated. The results of this study did not show a statistically significant correlation between clinical activity and the histopathological assessment of dogs with IBD. Certain connections were found between diarrhea and lacteal dilation in duodenum, and hematochezia and villous epithelial injury in colon but no other associations were found between the rest of the lesions and symptoms.

Proposed grading scheme for inflammatory bowel disease in ferrets and correlation with clinical signs

Inflammatory bowel disease (IBD) is an idiopathic, chronic, inflammatory disease of the gastrointestinal tract of companion animals, including ferrets (Mustela putorius furo). Clinical signs of IBD are nonspecific, and intestinal biopsies are necessary for a definitive diagnosis. A grading scheme has not been established for ferrets. Additionally, the association between histologic severity and clinical signs in ferrets is unknown. We evaluated enteric samples from ferrets diagnosed with IBD, compared histologic grading schemes, and correlated the results with the severity of clinical signs. Enteric sections from 23 ferrets with IBD were analyzed using grading schemes for intestinal inflammation in cats and dogs, and a correlation with clinical signs was evaluated. After dividing the histologic samples into groups based on the severity of clinical signs, main histologic differences were identified. Age and sex were also assessed for correlation with clinical signs. No significant correlation was found between the 2 grading schemes and clinical signs (rho = 0.02, p = 0.89; rho = 0.26, p = 0.18, respectively). Degree of villus fusion, hemorrhage and/or fibrin, epithelial damage, inflammation density, and crypt abscess formation were used retrospectively to create a ferret IBD grading scheme, which was significantly correlated with the severity of clinical signs (rho = 0.48, p = 0.01). A positive correlation was observed between age (p = 0.04) and females (p = 0.007) with severity of clinical signs. Our ferret grading scheme may have clinical utility in providing a more objective, consistent evaluation of IBD in ferrets.

Humoral immune responses against gut bacteria in dogs with inflammatory bowel disease

Inflammatory bowel disease (IBD) in dogs is associated with clinical signs of intestinal dysfunction, as well as abnormal lymphocytic and myeloid cell infiltrates in the small and/or large intestine. Thus, in many respects IBD in dogs resembles IBD in humans. However, the factors that trigger intestinal inflammation in dogs with IBD are not well understood and have been variously attributed to immune responses against dietary antigens or intestinal antigens. Previous studies in humans with IBD have documented increased production of IgG and IgA antibodies specific to intestinal bacteria, and this abnormal immune response has been linked to disease pathogenesis. Therefore, we investigated the humoral immune response against gut bacteria in dogs with IBD, using flow cytometry to quantitate IgG and IgA binding. Studies were also done to investigate the source of these antibodies (locally produced versus systemic production) and whether greater antibody binding to bacteria is associated with increased inflammatory responses. We found that dogs with IBD had significantly higher percentages and overall amounts of IgG bound to their intestinal bacteria compared to healthy dogs. Similarly, significantly higher percentages of bacteria were IgA+ bacteria were also found in dogs with IBD. Serum antibody recognition of gut bacteria was not different between healthy dogs and dogs with IBD, suggesting that anti-bacterial antibodies were primarily produced locally in the gut rather than systemically. Importantly, bacteria in the Actinobacteria phylum and in particular the genus Collinsella had significantly greater levels of antibody binding in dogs with IBD. Based on these findings, we concluded that antibody binding to commensal gut bacteria was significantly increased in dogs with IBD, that particular phyla were preferential targets for gut antibodies, and that anti-bacterial antibody responses may play an important role in regulating gut inflammation.

Sphingosine-1-phosphate (S1P) signaling regulates the production of intestinal IgA and its potential role in the pathogenesis of canine inflammatory bowel disease

Inflammatory bowel disease (IBD) is a common gastrointestinal disease in dogs. Decreased production of intestinal immunoglobulin A (IgA) has been suggested as a possible pathogenesis in a subset of canine IBD; however, the underlying cause remains unclear. Sphingosine-1-phosphate (S1P) is a lipid mediator that regulates intestinal IgA production by controlling lymphocyte trafficking in mice. The objectives of this study were to clarify the role of S1P in IgA production in dogs and to evaluate the expression of S1P-related molecules in dogs with IBD. First, an S1P receptor antagonist was administrated to five healthy dogs. The S1P receptor antagonist significantly decreased the IgA concentration in sera and feces but did not affect the IgG concentration. Moreover, the immunoreactivity of intestinal IgA was significantly decreased by S1P signal blockade. These results indicate that S1P signaling specifically regulates the intestinal IgA production in dogs. Subsequently, the intestinal S1P concentration and the expression of S1P-related molecules were measured in dogs with IBD and healthy dogs. The intestinal concentration of S1P was significantly lower in dogs with IBD than in healthy dogs. In addition, the gene expression levels of S1P receptor (S1P1) and S1P synthase (SK1) were significantly lower in dogs with IBD than in healthy dogs. Taken together, these observations suggest that decreased S1P production, likely caused by a lower expression of S1P synthetase, leads to attenuation of S1P/S1P1 signaling pathway and the production of intestinal IgA in dogs with IBD.

Treatment response and long term follow up in nineteen dogs diagnosed with chronic enteropathy in Australia

Chronic enteropathy (CE) in dogs is common worldwide, but little data is available from Australia. The aim of this study was to describe treatment response and long-term outcome in a cohort of dogs with CE. Dogs were prospectively enrolled at Murdoch University and the University of Melbourne. After diagnostic investigation to rule out diseases other than CE, dogs underwent sequential therapeutic trials until achieving a clinical response (diet then antibiotics, and finally immunosuppressants). Success was defined as 75% reduction of clinical severity for a minimum of five weeks. A total of 21 dogs were enrolled, and 19 completed the study. One dog was euthanised for lack of response to treatment and one excluded for lack of owner compliance. Most dogs responded to diet (n = 10), followed by antibiotics (n = 7) and immunosuppressants (n = 2). Long-term remission (median 21.1 months, [3.0-44.7]) was achieved in eight out of ten dietary responders without additional treatment. In contrast, only two dogs with antibiotic response remained in long-term remission, of which one needed on-going antibiotic treatment. Longer term remission was achieved in the two dogs treated with immunosuppressants with on-going low dose therapy. This study concludes that most dogs referred for CE in Australia respond to dietary treatment (even after previous dietary interventions), and remission is long-term compared to dogs treated with an antibiotic. Furthermore, the need for long-term antibiotics in some dogs to maintain response may lead to antibiotic resistance. This study supports adequate dietary trials for CE in dogs, and a need for alternative second-line treatments.

Correlation between toll-like receptor 4 and nucleotide-binding oligomerization domain 2 (NOD2) and pathological severity in dogs with chronic gastrointestinal diseases

Toll-like receptor 4 (TLR4), nucleotide-binding oligomerization domain 2 (NOD2), and TNF-α play important roles in human inflammatory bowel diseases. The aim of this study was to elucidate the relationship between Toll-like receptor 4, NOD2, and TNF-α and the severity of chronic gastrointestinal diseases in dogs. We examined the expression levels of TLR4, NOD2, and TNF-α in the stomach, duodenum, ileum, colon, and rectum obtained from 21 dogs with chronic gastrointestinal disease, including inflammatory bowel disease, high-grade lymphoma, food responsive enteropathy, chronic pancreatitis, low-grade lymphoma, inflammatory colorectal polyp, and chronic colitis. Next, we demonstrated whether there is good correlation between the expression levels of TLR4, NOD2, and TNF-α and the histopathological analysis of each sample. We found that the level of TLR4 expression in the ileum of dogs with chronic gastrointestinal disease was positively associated with the histopathological severity. We also found that the level of NOD2 expression in the duodenum, stomach, and rectum was positively associated with the histopathological severity. However, there was no correlation between TNF-α expression in the 5 regions tested in this study and the histopathological severity. These findings indicate that TLR4 and NOD2 are remarkably associated with the severity of chronic gastrointestinal disease in dogs.

Correlating Gastrointestinal Histopathologic Changes to Clinical Disease Activity in Dogs With Idiopathic Inflammatory Bowel Disease

Prior studies have failed to detect a convincing association between histologic lesions of inflammation and clinical activity in dogs with inflammatory bowel disease (IBD). We hypothesized that use of a simplified histopathologic scoring system would improve the consistency of interpretation among pathologists when describing histologic lesions of gastrointestinal inflammation. Our aim was to evaluate the correlation of histopathologic changes to clinical activity in dogs with IBD using this new system. Forty-two dogs with IBD and 19 healthy control dogs were enrolled in this retrospective study. Endoscopic biopsies from the stomach, duodenum, ileum, and colon were independently scored by 8 pathologists. Clinical disease activity was scored using the Canine Inflammatory Bowel Disease Activity Index (CIBDAI) or the Canine Chronic Enteropathy Clinical Activity Index (CCECAI), depending on the individual study center. Summative histopathological scores and clinical activity were calculated for each tissue (stomach, duodenum, ileum, and colon) and each tissue histologic score (inflammatory/morphologic feature). The correlation between CCECAI/CIBDAI and summative histopathologic score was significant ( P < .05) for duodenum ( r = 0.42) and colon ( r = 0.33). In evaluating the relationship between histopathologic scores and clinical activity, significant ( P < .05) correlations were observed for crypt dilation ( r = 0.42), lamina propria (LP) lymphocytes ( r = 0.40), LP neutrophils ( r = 0.45), mucosal fibrosis ( r = 0.47), lacteal dilation ( r = 0.39), and villus stunting ( r = 0.43). Compared to earlier grading schemes, the simplified scoring system shows improved utility in correlating histopathologic features (both summative histology scores and select histologic scores) to IBD clinical activity.

Mucosal immunity and gut microbiota in dogs with chronic enteropathy

Chronic enteropathy (CE) in dogs is a chronic and relapsing immunopathology, of unknown etiology, that usually manifests with a plethora of clinical signs reflecting the underlying heterogeneity in its pathogenesis. Alterations of the mucosal immune responses and the gut microbiota composition are thought to play an essential role in CE. Similar to humans, it is hypothesized that the breakdown in mucosal tolerance leads to aberrant and pathological immune responses toward the gut microbiota, that in turn, may contribute to the severity of disease, at least for certain CE subsets. Therefore, in this review, we discuss some of the most relevant and recent insights microbiological and immunological aspects characterizing CE in dogs.

Changes in duodenal CD163-positive cells in dogs with chronic enteropathy after successful treatment

Chronic enteropathy (CE) in dogs is characterized retrospectively per treatment response as food-responsive enteropathy (FRE), antibiotic-responsive enteropathy (ARE), and immunosuppressant-responsive enteropathy (IRE) - the latter most resembling inflammatory bowel disease in people. The aim of this study was to characterize duodenal macrophages (Mϕ) in CE using immunohistochemistry; with calprotectin (CAL) as a marker of early differentiated Mϕ and CD163 expression as a marker for resident Mϕ in the duodenum before and after treatment. Prior to treatment, dogs with FRE and IRE had a lower CD163⁺/CAL⁺ ratio than control dogs (CTRL) in crypts; this increased significantly and normalized compared with CTRL after treatment. Conversely, the CD163⁺/CAL⁺ ratio in dogs with ARE was comparable to that in healthy dogs before and after treatment. In summary, these results suggest that Mϕ play a role in the pathogenesis of CE in FRE and IRE, with a decrease in resident Mϕ and an increase in early differentiated Mϕ, but not in ARE dogs. Mϕ normalize after successful treatment.

Association of fecal calprotectin concentrations with disease severity, response to treatment, and other biomarkers in dogs with chronic inflammatory enteropathies

BACKGROUND

Calprotectin is a marker of inflammation, but its clinical utility in dogs with chronic inflammatory enteropathies (CIE) is unknown.

OBJECTIVE

Evaluation of fecal calprotectin in dogs with biopsy-confirmed CIE.

ANIMALS

127 dogs.

METHODS

Prospective case-control study. Dogs were assigned a canine chronic enteropathy clinical activity index (CCECAI) score, and histologic lesions severity was assessed. Fecal calprotectin, fecal S100A12, and serum C-reactive protein (CRP) were measured. Food- or antibiotic-responsive cases (FRE/ARE, n = 13) were distinguished from steroid-/immunosuppressant-responsive or -refractory cases (SRE/IRE, n = 20). Clinical response to treatment in SRE/IRE dogs was classified as complete remission (CR), partial response (PR), or no response (NR).

RESULTS

Fecal calprotectin correlated with CCECAI (ρ = 0.27, P = .0065) and fecal S100A12 (ρ = 0.90, P < .0001), some inflammatory criteria, and cumulative inflammation scores, but not serum CRP (ρ = 0.16, P = .12). Dogs with SRE/IRE had higher fecal calprotectin concentrations (median: 2.0 μg/g) than FRE/ARE dogs (median: 1.4 μg/g), and within the SRE/IRE group, dogs with PR/NR had higher fecal calprotectin (median: 37.0 μg/g) than dogs with CR (median: 1.6 μg/g). However, both differences did not reach statistical significance (both P = .10). A fecal calprotectin ≥15.2 μg/g separated both groups with 80% sensitivity (95% confidence interval [95%CI]: 28%-100%) and 75% specificity (95%CI: 43%-95%).

CONCLUSIONS AND CLINICAL IMPORTANCE

Fecal calprotectin could be a useful surrogate marker of disease severity in dogs with CIE, but larger longitudinal studies are needed to evaluate its utility in predicting the response to treatment.

Intestinal Stem Cells to Advance Drug Development, Precision, and Regenerative Medicine: A Paradigm Shift in Translational Research

Recent advances in our understanding of the intestinal stem cell niche and the role of key signaling pathways on cell growth and maintenance have allowed the development of fully differentiated epithelial cells in 3D organoids. Stem cell-derived organoids carry significant levels of proteins that are natively expressed in the gut and have important roles in drug transport and metabolism. They are, therefore, particularly relevant to study the gastrointestinal (GI) absorption of oral medications. In addition, organoids have the potential to serve as a robust preclinical model for demonstrating the effectiveness of new drugs more rapidly, with more certainty, and at lower costs compared with live animal studies. Importantly, because they are derived from individuals with different genotypes, environmental risk factors and drug sensitivity profiles, organoids are a highly relevant screening system for personalized therapy in both human and veterinary medicine. Lastly, and in the context of patient-specific congenital diseases, orthotopic transplantation of engineered organoids could repair and/or replace damaged epithelial tissues reported in various GI diseases, such as inflammatory bowel disease, cystic fibrosis, and tuft enteropathy. Ongoing translational research on organoids derived from dogs with naturally occurring digestive disorders has the potential to improve the predictability of preclinical models used for optimizing the therapeutic management of severe chronic enteropathies in human patients.

Immunophenotype of Peripheral Blood Lymphocytes in Dogs with Inflammatory Bowel Disease

Background

Inflammatory bowel disease (IBD) is common in dogs. Despite the known importance of intestinal lymphocytes in its pathogenesis, little is known about the role of peripheral blood lymphocytes (PBLs) in IBD.

Objectives

The aims of this study were (1) comparison of PBLs analyzed by flow cytometry (FCM) in IBD dogs and healthy controls and (2) comparison of PBLs in IBD dogs at the time of diagnosis and in dogs in clinical remission.

Animals

Whole blood samples of 19 IBD dogs at the time of diagnosis and blood samples of 6 dogs in clinical remission were collected. Ten healthy dogs served as controls.

Methods

In this prospective observational study, PBLs were analyzed with multicolor FCM by staining with a panel of anticanine and cross‐reactive monoclonal antibodies against T‐ and B‐cell differentiation antigens, including CD45, CD3, CD4, CD8α, CD8β, TCRαβ, TCRγδ, CD79αcy, and CD21.

Results

The IBD patients’ PBLs had significantly decreased percentages of TCRγδ⁺ T lymphocytes (median: healthy dogs, 3.32; IBD dogs, 0.97; P = 0.03) and CD21⁺ B cells (median: healthy dogs, 27.61; IBD dogs, 17.26; P = 0.04). There were no significant differences in PBLs between pretreatment and follow‐up samples.

Conclusions and Clinical Importance

The differences between PBLs in healthy and IBD dogs analyzed by FCM indicate an imbalance of lymphocytes with different immunologic functions and emphasize the potential value of this technique in a larger cohort of dogs. The PBLs did not differ between IBD dogs before treatment and clinically well‐controlled dogs after treatment.

Lung Inflammation Associated With Clinical Acute Necrotizing Pancreatitis in Dogs

Although dogs with acute necrotizing pancreatitis (ANP) can develop respiratory complications, there are no data describing lung injury in clinical cases of ANP in dogs. Therefore, we conducted a study to characterize lung injury and determine if pulmonary intravascular macrophages (PIMs) are induced in dogs with ANP ( n = 21) compared with control dogs ( n = 6). Two pathologists independently graded histologic sections of pancreas from clinical cases to characterize the severity of ANP (total scores of 3–10) compared with controls showing histologically normal pancreas (total scores of 0). Based on histological grading, lungs from dogs with ANP showed inflammation (median score, 1.5; range, 0–3), but the scores did not differ statistically from the control lungs (median score, 0.5; range, 0–2). A grid intersects-counting method showed an increase in the numbers of MAC387-positive alveolar septal mononuclear phagocyte profiles in lungs of dogs with ANP (ratio median, 0.0243; range, 0.0093–0.0734, with 2 outliers at 0.1523 and 0.1978) compared with controls (ratio median, 0.0019; range, 0.0017–0.0031; P < .0001). Only dogs with ANP showed labeling for von Willebrand factor in alveolar septal capillary endothelial cells, septal inflammatory cells, and alveolar macrophages. Toll-like receptor 4 and interleukin 6 were variably expressed in alveolar macrophages and septal inflammatory cells in lungs from both ANP and control dogs. Inducible nitric oxide synthase was detected in alveolar macrophages of dogs with ANP only. These data show that dogs with ANP have lung inflammation, including the recruitment of PIMs and expression of inflammatory mediators.

Cats are not small dogs: is there an immunological explanation for why cats are less affected by arthropod-borne disease than dogs?

It is widely recognized that cats appear to be less frequently affected by arthropod-borne infectious diseases than dogs and share fewer zoonotic pathogens with man. This impression is supported by the relative lack of scientific publications related to feline vector-borne infections. This review explores the possible reasons for the difference between the two most common small companion animal species, including the hypothesis that cats might have a genetically-determined immunological resistance to arthropod vectors or the microparasites they transmit. A number of simple possibilities might account for the lower prevalence of these diseases in cats, including factors related to the lifestyle and behaviour of the cat, lesser spend on preventative healthcare for cats and reduced opportunities for research funding for these animals. The dog and cat have substantially similar immune system components, but differences in immune function might in part account for the markedly distinct prevalence and clinicopathological appearance of autoimmune, allergic, idiopathic inflammatory, immunodeficiency, neoplastic and infectious diseases in the two species. Cats have greater genetic diversity than dogs with much lower linkage disequilibrium in feline compared with canine breed groups. Immune function is intrinsically related to the nature of the intestinal microbiome and subtle differences between the canine and feline microbial populations might also impact on immune function and disease resistance. The reasons for the apparent lesser susceptibility of cats to arthropod-borne infectious diseases are likely to be complex, but warrant further investigation.

Histamine Receptor Expression in the Gastrointestinal Tract of Dogs

Histamine is an important mediator of many physiological processes including gastrointestinal function that acts via four different histamine receptors (H1R to H4R). Elevated histamine levels and increased HR messenger ribonucleic acid (mRNA) have been shown in humans with gastrointestinal disorders such as irritable bowel syndrome or allergic intestinal diseases. As there is limited knowledge concerning the distribution of histamine receptors (HR) in dogs, one aim of this study was to investigate the expression of histamine 1 receptor (H1R), histamine 2 receptor (H2R) and histamine 4 receptor (H4R) in the canine gastrointestinal tract at protein level using immunohistochemistry. Histamine 1 receptor, H2R and H4R were widely expressed throughout the canine gastrointestinal tract including epithelial, mesenchymal, neuronal and immune cells. In addition, in situ hybridisation was established for detecting canine H4R mRNA. Results showed H4R mRNA to be present in enterocytes, lamina propria immune cells and submucosal plexus in the duodenum and colon of nearly all investigated animals. The results elucidate the importance of HR in the canine gut and represent the basis for investigating their possible impact on canine inflammatory gastrointestinal disorders.

S100A12 concentrations and myeloperoxidase activity in the intestinal mucosa of healthy dogs

BACKGROUND

Relatively few laboratory markers have been evaluated for the detection or monitoring of intestinal inflammation in canine chronic enteropathies, including inflammatory bowel disease (IBD). Previous research found that the intestinal mucosal levels of S100A12 and myeloperoxidase (MPO), as biomarkers of gut inflammation, were elevated in human patients with IBD. To date, the S100A12 and MPO levels in intestinal mucosal samples from either healthy dogs or from dogs suffering from IBD remain unreported. Therefore, this study aimed to evaluate the mucosal S100A12 and MPO levels in four different parts of the intestine (duodenum, jejunum, ileum and colon) in 12 healthy laboratory Beagle dogs using the ELISA and spectrophotometric methods, respectively.

RESULTS

Based on histological examinations, the recorded findings for all the samples were considered normal. The mucosal concentration of S100A12 in the ileum was significantly higher than in all other segments of the intestine (p < 0.05). MPO activity was significantly higher in the ileal, jejunal and duodenal than in colonic mucosal samples (p < 0.05). Moreover, its concentration was higher in the jejunum than in the duodenum.

CONCLUSIONS

This study showed that S100A12 and MPO are reliably detectable in canine intestinal mucosa. The assays used appeared to be sufficient to further evaluate the role of S100A12 and MPO in the pathogenesis of canine chronic enteropathies, including IBD. These biomarkers may play a role in the initial detection of gut inflammation suggesting the need for further investigations to confirm IBD or to differentiate between IBD subtypes. Understanding the role of S100A12 and MPO in the pathogenesis of chronic intestinal inflammation in future may result in an improved understanding of canine chronic intestinal inflammation.

Urinary and faecal N-methylhistamine concentrations do not serve as markers for mast cell activation or clinical disease activity in dogs with chronic enteropathies

Background

This study sought to correlate faecal and urinary N-methylhistamine (NMH) concentrations with resting versus degranulated duodenal mast cell numbers in dogs with chronic enteropathies (CE), and investigate correlations between intestinal mast cell activation and clinical severity of disease as assessed by canine chronic enteropathy clinical activity index (CCECAI), and between urinary and faecal NMH concentrations, mast cell numbers, and histopathological scores. Twenty-eight dogs with CE were included. Duodenal biopsies were stained with haematoxylin and eosin (H&E), toluidine blue, and by immunohistochemical labelling for tryptase. Duodenal biopsies were assigned a histopathological severity score, and duodenal mast cell numbers were counted in five high-power fields after metachromatic and immunohistochemical staining. Faecal and urinary NMH concentrations were measured by gas chromatography–mass spectrometry.

Results

There was no correlation between the CCECAI and faecal or urinary NMH concentrations, mast cell numbers, or histopathological score – or between faecal or urinary NMH concentration and mast cell numbers. Post hoc analysis revealed a statistically significant difference in toluidine blue positive mast cells between two treatment groups (exclusion diet with/without metronidazole versus immunosuppression (IS)), with higher numbers among dogs not requiring IS.

Conclusion

Faecal and urinary NMH concentrations and duodenal mast cell numbers were not useful indicators of severity of disease as assessed by the CCECAI or histological evaluation. The number of duodenal mast cells was higher in dogs that did not need IS, i.e. in dogs responding to an exclusion diet (with/without metronidazole), than in dogs requiring IS. Further studies comparing the role of mast cells in dogs with different forms of CE are needed.

Phenotypic characterization of canine intestinal intraepithelial lymphocytes in dogs with inflammatory bowel disease

Background

Many dogs suffering from inflammatory bowel disease (IBD) are presented to veterinary clinics. These patients are diagnosed based on a history of chronic gastrointestinal signs and biopsy‐confirmed histopathologic intestinal inflammation. Intestinal intraepithelial lymphocytes (IEL) are part of the first line of defense in the gastrointestinal immune system. Alterations in IEL subsets may play a role in the pathogenesis of IBD.

Hypothesis

The aim of this study was to characterize the phenotypes of IEL in dogs with IBD compared with healthy control dogs.

Animals

Intestinal intraepithelial lymphocytes subpopulations of control dogs (n = 5) obtained from endoscopic biopsies (EB) were compared to those obtained from full thickness biopsies (FTB) on the same day. In addition, the phenotypes of IEL from FTB of control dogs (n = 10) were compared with EB of IBD dogs (n = 10). Each participant was scored clinically using the canine inflammatory bowel disease activity index (CIBDAI), and all samples were graded histopathologically. Three‐color flow cytometry of isolated IEL was performed using monoclonal antibodies against T‐ and B‐lymphocyte subpopulations.

Results

No significant differences in the composition of IEL subpopulations were found in control dogs based on method of biopsy. The IBD dogs had significantly higher CIBDAI and histopathologic scores compared with control dogs and their IEL contained a significantly higher frequency TCRγδ T‐cells.

Conclusions and Clinical Importance

Endoscopic biopsies provide suitable samples for 3‐color flow cytometry when studying canine intestinal IEL and IBD patients show significant changes of major T‐cell subsets compared to healthy control dogs.

Fecal and urinary N-methylhistamine concentrations in dogs with chronic gastrointestinal disease

Due to their ability to release inflammatory mediators, such as histamine, mast cells are potentially important in gastrointestinal disease. The purpose of this study was to measure N-methylhistamine (NMH), a histamine metabolite, in fecal and urine samples from dogs with chronic gastrointestinal disease. Fecal and urinary NMH concentrations were compared between dogs with chronic gastrointestinal disease and control dogs, and/or to control ranges. Correlation between fecal and urinary NMH concentrations, serum C-reactive protein (CRP) concentration, the clinical disease activity index (CCECAI), and gastrointestinal mucosal mast cell numbers (where available) in dogs with gastrointestinal disease was evaluated. Seven of 16 dogs with gastrointestinal disease had increased urinary or fecal NMH concentrations, but there was no correlation between NMH concentrations and the CCECAI or mucosal mast cells numbers. Urinary NMH concentrations were positively associated with histological grading and serum CRP concentrations. The lack of correlation between NMH concentrations and the CCECAI suggests that NMH may not be a good marker for clinical disease activity in dogs as determined by the CCECAI. Based on their association with severity of intestinal mucosal inflammation, urinary NMH concentrations may potentially have clinical utility as a marker of intestinal inflammation in certain groups of dogs with chronic gastrointestinal disease, but future studies in a larger number of dogs are necessary to further characterize the role of mast cell-mediated inflammation in dogs with chronic gastrointestinal disease.

Intestinal protease-activated receptor-2 and fecal serine protease activity are increased in canine inflammatory bowel disease and may contribute to intestinal cytokine expression

Serine proteases elicit cellular responses via protease-activated receptor-2 (PAR-2) which is known to regulate inflammation and the immune response. Although the gastrointestinal tract is exposed to large amounts of proteolytic enzymes, the role of PAR-2 in canine inflammatory bowel disease (IBD) remains unclear. The objective of this study was to investigate the effects of PAR-2 activation on inflammatory cytokine/chemokine gene expression in canine intestine and the expression of intestinal PAR-2 and fecal serine protease activity in dogs with IBD. Duodenal biopsies from healthy dogs were cultured and treated ex vivo with trypsin or PAR-2 agonist peptide, and inflammatory cytokine/chemokine gene expression in the tissues was then quantified by real-time PCR. PAR-2 mRNA and protein expression levels in the duodenal mucosa were examined by real-time PCR and immunohistochemistry, respectively. Fecal serine protease activity was determined by azocasein assay. In ex vivo-cultured duodenum, trypsin and PAR-2 agonist peptide induced significant up-regulation of mRNA expression levels of interleukin-1 β (IL-1β), IL-8, mucosae-associated epithelial chemokine (MEC) and fractalkine, and this up-regulation was inhibited by a serine protease inhibitor. Duodenal PAR-2 mRNA and protein expression levels were higher in dogs with IBD than in healthy control dogs. Fecal serine protease activity was significantly elevated in dogs with IBD, and the level of activity correlated positively with the clinical severity score. These results suggest that PAR-2 may contribute to the pathogenesis of canine IBD by inducing expression of inflammatory mediators in response to luminal serine proteases.

Immunohistochemical and morphometric analysis of intestinal full-thickness biopsy samples from cats with lymphoplasmacytic inflammatory bowel disease

The distribution and numbers of CD3(+) T lymphocytes, immunoglobulin(+) plasma cells and calprotectin (L1)(+) macrophages was analyzed in full-thickness, formalin-fixed biopsy samples from the small intestine (duodenum, jejunum and ileum) and from the colon from nine cats with clinical signs of inflammatory bowel disease (IBD). All animals had lymphoplasmacytic enteritis or lymphoplasmacytic enterocolitis. Equivalent samples from the same intestinal regions from 12 healthy pet cats served as controls. Labelled cells in the lamina propria were counted by computer-aided morphometry. The different cell types were similarly distributed in both groups, but there were differences in their numbers. There were more CD3(+) T cells in the duodenum and jejunum of cats with IBD; however, the difference was only significant for the duodenum. There were significantly more IgA(+) cells in the duodenal crypt region. There were significantly more IgG(+) cells in the lower jejunal crypt region. Plasma cells expressing IgM were decreased in cats with IBD, but the difference was not significant. L1(+) macrophages were significantly decreased in the lower crypt area of the colon in cats with IBD and there was a trend to decreased L1(+) cells in the upper crypt area of the duodenum and jejunum. Comparison of the results of this study with previous findings on endoscopically-obtained duodenal biopsy samples from cats with IBD revealed some differences. These discrepancies might relate to differences between control cat populations, types of biopsy samples, methodological factors such as different counting techniques and the activity of the disease at the time of sampling.

Bcl-2/caspase 3 mucosal imbalance favors T cell resistance to apoptosis in dogs with inflammatory bowel disease

Canine idiopathic inflammatory bowel disease (IBD) is believed to result from complex interplay between genetic, microbial, and immunologic factors. Abnormal cell death by apoptosis may result in the persistence of activated intestinal T cells that contribute to mucosal inflammation and clinical severity. To test this hypothesis, we investigated the mucosal expression of pro- and anti-apoptotic proteins in different intestinal compartments and their association with inflammatory indices in dogs with IBD. Apoptosis of lamina propria (LP) T cells in duodenal, ileal, and colonic tissues in control and IBD dogs was analyzed by caspase 3/Bcl-2 immunohistochemistry and TUNEL assays. Densities and distributions of LP caspase 3 and Bcl-2 cells were correlated to histopathologic lesions and the clinical activity index (CIBDAI). Compared to control tissues, IBD dogs had significantly (P<0.01) fewer caspase 3 cells in colonic mucosa. Double immunostaining identified the majority of apoptotic cells as TUNEL(+)/caspase 3(+). Within intestinal mucosa of IBD dogs, there were significantly greater numbers of Bcl-2 cells at the apical and basilar villus in the duodenum as compared to the colon and to the apical and basilar villus in the ileum (P<0.001 for all comparisons). There were significantly greater numbers of Bcl-2 cells at the apical and basilar villus of the duodenum but significantly fewer numbers of Bcl-2 cells at the apical villus of the ileum in IBD dogs compared with controls (P<0.001, P<0.001, and P<0.02, respectively). There was a significant association between the number of Bcl-2 cells in the duodenum of IBD dogs and the CIBDAI (P<0.001 each for mild, moderate and severe clinical IBD). In conclusion, apoptosis of T lymphocytes varies within intestinal compartments of dogs with IBD. Mucosal imbalance of Bcl-2/caspase 3 expression favors T cell resistance to apoptosis which may contribute to T cell accumulation and chronic intestinal inflammation, similar to human IBD.

Biomarkers in canine inflammatory bowel disease diagnostics

Canine inflammatory bowel disease (IBD) is a heterogeneous group of chronic gastrointestinal disorders. The etiology, similar to human IBD, remains unknown. Canine IBD is diagnosed by exclusion, which is a long, time and money-consuming process due to the need of elimination of other diseases presenting with similar symptoms. Therefore, a search for a specific and sensitive marker is needed to overcome these difficulties. The article is divided into 3 sections presenting up-to-date information about laboratory markers, immunohistochemical markers and changes in the neurochemical coding of the enteric nervous system, concentrating on their usefulness and future applications. Data concerning laboratory and immunohistochemical markers is based mainly on canine IBD, while the neuroimmunohistochemistry section presents knowledge from human IBD due to the lack of such studies in veterinary medicine.

CD4⁺ T cell cytokine gene and protein expression in duodenal mucosa of dogs with inflammatory bowel disease

Inflammatory bowel disease (IBD) is a common cause of chronic gastrointestinal signs in dogs. In humans, T helper cells have important roles in the pathogenesis of IBD. In contrast, no specific involvement of a distinct T cell subset has been described in canine IBD. The present study evaluated the gene and protein expression of cytokines of T cell subsets in duodenal mucosa from dogs with IBD. Relative quantification of interleukin (IL)-17A, interferon (IFN)-γ, IL-4 and IL-10 mRNA transcription was performed using duodenal mucosa from 27 IBD dogs and 8 controls. Duodenal mucosal IL-17A, IFN-γ and IL-10 protein levels were determined by ELISA in 15 IBD dogs and 8 controls. There was no significant difference in each cytokines mRNA transcription level between groups. There was no significant difference in IL-17A, IFN-γ and IL-10 protein expression levels between groups. Thus, there is no clear evidence for the involvement of distinct Th cytokine in the pathogenesis of canine IBD.

Measurement of IL-12 (p40, p35), IL-23p19, and IFN-γ mRNA in duodenal biopsies of cats with inflammatory enteropathy

Background

Dietary hypersensitivity and inflammatory bowel disease (IBD) are important causes of chronic vomiting and diarrhea in cats. IL‐23 has been recently found to be a key factor in the immunopathogenesis of IBD in humans but the involvement in IBD has not been investigated in cats.

Hypothesis/Objectives

Expression of genes encoding Il‐12p35 and p40, IL‐23p19, and IFN‐γ may be up‐regulated in duodenal biopsy specimens taken from cats with histologic evidence of inflammation.

Animals and Methods

Duodenal biopsy specimens were collected from control cats (n = 21) and cats with inflammatory enteropathy (n = 13). Routine histopathology, immunohistochemistry (IHC), and qRT‐PCR were used to assess expression of MHC class II and to measure gene transcripts encoding the p35, p40, and p19 subunits of the IL‐12 family of cytokines and IFN‐γ.

Results

There were significant differences in expression of mRNA encoding IL‐12p35 and IL‐23p19 between healthy cats and cats with inflammatory enteropathy. IL‐12p35 mRNA was lower in the duodenal mucosa of cats with inflammatory enteropathy compared with the mucosa of healthy cats (P = .001). In contrast, IL‐23p19 mRNA expression was higher in duodenal biopsy specimens from cats with inflammatory enteropathy than in those from healthy controls (P = .001). There was no difference in expression of IL‐12p40 and IFN‐γ mRNA (P > .05). The majority of cats with inflammatory enteropathy had histologic evidence of moderate to severe colitis (score 2).

Conclusions and Clinical Importance

The results of this preliminary study suggest that IL‐23 plays a role in the pathogenesis of feline inflammatory enteropathy.

Somatostatin as an Active Substance of Enteroendocrine Cells in the Canine Digestive Tract in Physiological Conditions and during Inflammatory Bowel Disease

The aim of the present investigation is to examine the changes in the number of somatostatin-like immunoreactive (SOM-LI) enteroendocrine cells in various parts of the canine gastrointestinal (GI) tract during canine inflammatory bowel disease (IBD). The distribution of SOM-LI enteroendocrine cells was studied using the double-labeling immunofluorescence technique with antisera against chromogranin A (CgA; used here as a marker of enteroendocrine cells) and somatostatin (SOM). Evaluation of the number of CgA-positive cells, which also contained SOM in the mucosal layer of canine stomach, duodenum, jejunum and descending colon was based on the counting of such cells per unit area (0.1 mm2). In physiological conditions, the number of SOM-LI enteroendocrine cells has been shown to constitute 5.30±2.07 in the stomach, 2.23±0.56 in the duodenum, 1.86±0.48 in the jejunum and 1.19±0.36 in the descending colon. Canine IBD caused an increase in the number of cells studied in the stomach (to 9.55±1.46) and the jejunum (to 3.84±1.16), while the changes observed in the duodenum and the descending colon have not been statistically significant. The obtained results suggest that SOM-LI enteroendocrine cells, as well as somatostatin, may be involved in pathological processes during canine IBD. Moreover, this study can be treated as the first step of application of SOM and/or its analogues in the treatment of canine IBD in the future.

Canine gut dendritic cells in the steady state and in inflammatory bowel disease

Alongside the intestinal border, dendritic cells (DCs) sample large amounts of endogenous and potentially pathogenic antigens followed by initiation of protective immune responses or induction of tolerance. Breakdown of oral tolerance towards commensal bacteria is suggested to be crucial for the development of both human and canine inflammatory bowel disease (IBD). The aim of this study was to investigate canine intestinal DCs in the steady state and in dogs with IBD using multicolour immunofluorescence. In the healthy gut, DC-like cells expressed MHC II, CD1a8.2 and CD11c, and, in lower amounts, CD11b, within lamina propria, Peyer's patches (PPs) and mesenteric lymph nodes (MLNs), whereas those expressing CD80 and CD86 were only present in PPs and MLNs. Occasionally, DC-like cells were in contact with the intestinal lumen through transepithelial projections. In canine IBD, CD1a8.2+, CD11b+ and CD11c+ DC-like cells were decreased within the stomach, duodenum and colon, whereas the colonic mucosa revealed elevation of CD86+ DC-like cells. The complex network of DC-like cells in the gut indicates their important role in canine mucosal immunity, including active sampling of luminal antigens. Furthermore, their shift in diseased dogs suggests a pathogenetic significance for canine IBD.

Serum calprotectin concentrations in dogs with idiopathic inflammatory bowel disease

OBJECTIVE

To measure serum calprotectin concentration in dogs with inflammatory bowel disease (IBD) before and after initiation of treatment and evaluate its correlation with a clinical scoring system (canine IBD activity index), serum canine C-reactive protein concentration, and severity of histopathologic changes.

ANIMALS

34 dogs with idiopathic IBD and 139 healthy control dogs.

PROCEDURES

From dogs with IBD, blood samples were collected immediately before (baseline) and 3 weeks after initiation of 1 of 2 treatments: prednisone (1 mg/kg, PO, q 12 h; n = 21) or a combination of prednisone and metronidazole (10 mg/kg, PO, q 12 h; 13). Blood samples were collected once from each of the control dogs. For all samples, serum calprotectin concentration was determined via radioimmunoassay.

RESULTS

Mean serum calprotectin concentrations for dogs with IBD at baseline (431.1 μg/L) and 3 weeks after initiation of treatment (676.9 μg/L) were significantly higher, compared with that (219.4 μg/L) for control dogs, and were not significantly correlated with the canine IBD activity index, serum C-reactive protein concentration, or severity of histopathologic changes. The use of a serum calprotectin concentration of ≥ 296.0 μg/L as a cutoff had a sensitivity of 82.4% (95% confidence interval, 65.5% to 93.2%) and specificity of 68.4% (95% confidence interval, 59.9% to 76.0%) for distinguishing dogs with idiopathic IBD from healthy dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum calprotectin concentration may be a useful biomarker for the detection of inflammation in dogs, but the use of certain drugs (eg, glucocorticoids) appears to limit its clinical usefulness.

Cytokines in canine inflammatory bowel disease

Canine inflammatory bowel disease is a group of chronic enteropathies characterized by persistent or recurring gastric symptoms with an unknown etiology which are related to histopathological changes in the mucosa of the small and large bowel in the form of cellular infiltration in the mucosal lamina propria. Recent years have witnessed a growing number of investigations into the role of the immune system and, in particular, cytokines in the development of IBD. In this article, the expression of pro-inflammatory (IL-1, IL-2, IL-5, IL-6, IL-12, IL-18, IFN-γ, TNF-α) and anti-inflammatory cytokines (IL-4, IL-10) was compared in canine patients with IBD based on clinical presentation, breed, lamina propria cell infiltrate and histopathological grade. Only selected studies confirmed higher mRNA expression levels of cytokines IL-2, IL-4, IL-5, IL-12p40, IFN-γ, TNF-α and TGF-β in dogs with IBD in comparison with healthy subjects. GSD were strongly represented in most study populations. Dogs with LPE were characterized by elevated levels of IL-1α, IL-1β, IL-2, IL-5, IL-6, IL-12, TNF-α, TGF-β. The present studies of canine patients with LPC revealed the mRNA expression of cytokines IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p35, IL-12p40, IFN-γ, TNF-α, TGF-β. In the reviewed studies, the progression of IBD was not accompanied by changes in the mRNA expression of IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, IL-18, TNF-α, IFN-γ or TGF-β.

Decreased immunoglobulin A concentrations in feces, duodenum, and peripheral blood mononuclear cells of dogs with inflammatory bowel disease

BACKGROUND

Although immunoglobulin A (IgA) plays a key role in regulating gut homeostasis, its role in canine inflammatory bowel disease (IBD) is unknown.

HYPOTHESIS

IgA expression may be altered in dogs with IBD, unlike that observed in healthy dogs and dogs with other gastrointestinal diseases.

ANIMALS

Thirty-seven dogs with IBD, 10 dogs with intestinal lymphoma, and 20 healthy dogs.

METHODS

Prospective study. IgA and IgG concentrations in serum, feces, and duodenal samples were measured by ELISA. IgA(+) cells in duodenal lamina propria and IgA(+) CD21(+) peripheral blood mononuclear cells (PBMCs) were examined by immunohistochemistry and flow cytometry, respectively. Duodenal expression of the IgA-inducing cytokine transforming growth factor β (TGF-β), B cell activating factor (BAFF), and a proliferation-inducing ligand (APRIL) was quantified by real-time RT-PCR.

RESULTS

Compared to healthy dogs, dogs with IBD had significantly decreased concentrations of IgA in fecal and duodenal samples. The number of IgA(+) CD21(+) PBMCs and IgA(+) cells in duodenal lamina propria was significantly lower in dogs with IBD than in healthy dogs or dogs with intestinal lymphoma. Duodenal BAFF and APRIL mRNA expression was significantly higher in IBD dogs than in the healthy controls. Duodenal TGF-β mRNA expression was significantly lower in dogs with IBD than in healthy dogs and dogs with intestinal lymphoma.

CONCLUSIONS AND CLINICAL IMPORTANCE

IBD dogs have decreased IgA concentrations in feces and duodenum and fewer IgA(+) PBMCs, which might contribute to development of chronic enteritis in dogs with IBD.

Gene expression in intestinal mucosal biopsy specimens obtained from dogs with chronic enteropathy

OBJECTIVE

To characterize mucosal gene expression in dogs with chronic enteropathy (CE).

ANIMALS

18 dogs with CE and 6 healthy control dogs.

PROCEDURES

Small intestinal mucosal biopsy specimens were endoscopically obtained from dogs. Disease severity in dogs with CE was determined via inflammatory bowel index scores and histologic grading of biopsy specimens. Total RNA was extracted from biopsy specimens and microchip array analysis (approx 43,000 probe sets) and quantitative reverse transcriptase PCR assays were performed.

RESULTS

1,875 genes were differentially expressed between dogs with CE and healthy control dogs; 1,582 (85%) genes were downregulated in dogs with CE, including neurotensin, fatty acid-binding protein 6, fatty acid synthase, aldehyde dehydrogenase 1 family member B1, metallothionein, and claudin 8, whereas few genes were upregulated in dogs with CE, including genes encoding products involved in extracellular matrix degradation (matrix metallopeptidases 1, 3, and 13), inflammation (tumor necrosis factor, interleukin-8, peroxisome proliferator-activated receptor γ, and S100 calcium-binding protein G), iron transport (solute carrier family 40 member 1), and immunity (CD96 and carcinoembryonic antigen-related cell adhesion molecule [CEACAM] 18). Dogs with CE and protein-losing enteropathy had the greatest number of differentially expressed genes. Results of quantitative reverse transcriptase PCR assay for select genes were similar to those for microchip array analysis.

CONCLUSIONS AND CLINICAL RELEVANCE

Expression of genes encoding products regulating mucosal inflammation was altered in dogs with CE and varied with disease severity. Impact for Human Medicine-Molecular pathogenesis of CE in dogs may be similar to that in humans with inflammatory bowel disease.