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.

Background: T cells play a key role in the pathogenesis of chronic inflammatory enteropathy (CIE) in dogs. Cluster of differentiation 3 (CD3) antigen serves as a marker for T cells. In human medicine, Ki-67 is an indicator for cell growth but there are only a few studies in dogs with CIE.Objective: To investigate Ki-67 in relation to T cells as a marker for CIE in dogs.Animals: Eleven dogs with CIE and 6 healthy beagle controls (CO). Methods: Retrospective case-control study. Dogs were clinically assessed by the Canine Chronic Enteropathy Clinical Activity Index (CCECAI). Duodenal mucosal biopsy samples were endoscopically obtained for histopathologic examination by means of the World Small Animal Veterinary Association score. Double-labeled immunofluorescence was used to investigate colocalization of Ki-67 and CD3 in epithelium and lamina propria (LP) of villi and crypts.Results: Dogs with CIE had significantly higher clinical score (median, 5.0; interquartile range [IQR], 3-7) compared to CO (all 0; P < .001). The Ki-67/CD3 doublepositive cells were significantly increased in the LP of the crypt region of CIE dogs (0.63 cells/mm 2 ; IQR, 0-0.54) versus CO (0.08 cells/mm 2 ; IQR, 0-0.26; P = .044). A significant correlation was found between CCECAI and the Ki-67/CD3 ratio in the LP of the crypt region (r = 0.670; P = .012) in dogs with CIE.Conclusions and Clinical Importance: The Ki-67/CD3 ratio is upregulated in the LP crypt region of dogs with CIE and it correlates with clinical severity. Therefore, Ki-67/CD3 could be a useful tool for detection of CIE.

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