Intestinal mucus barrier disruption may occur with chronic inflammatory enteropathies. The lack of studies evaluating mucus health in dogs with chronic colitis arises from inherent challenges with assessment of the intestinal mucus layer. It is therefore unknown if reduced goblet cell (GBC) numbers and/or mucin 2 (MUC2) expression, which are responsible for mucus production and secretion, correlate with inflammation severity in dogs with granulomatous colitis (GC) or lymphocytic-plasmacytic colitis (LPC). It is undetermined if Ki-67 immunoreactivity, which has been evaluated in dogs with small intestinal inflammation, similarly correlates to histologic severity in GC and LPC. Study objectives included comparing Ki-67 immunoreactivity, GBC population and MUC2 expression in dogs with GC, LPC and non-inflamed colon; and exploring the use of ribonucleic acid (RNAscope®) in-situ hybridization (ISH) to evaluate MUC2 expression in canine colon. Formalin-fixed endoscopic colonic biopsies were obtained from 48 dogs over an eight-year period. A blinded pathologist reviewed all biopsies. Dogs were classified into the GC (n=19), LPC (n=19) or no colitis (NC) (n=10) group based on final histopathological diagnosis. Ki-67 immunohistochemistry, Alcian-Blue/PAS staining to highlight GBCs, and RNAscope® ISH using customized canine MUC2-targeted probes were performed. At least five microscopic fields per dog were selected to measure Ki-67 labelling index (KI67%), GBC staining percentage (GBC%) and MUC2 expression (MUC2%) using image analysis software. Spearman’s correlation coefficients were used to determine associations between World Small Animal Veterinary Association histologic score (WHS) and measured variables. Linear regression models were used to compare relationships between WHS with KI67%, GBC%, and MUC2%; and between GBC% and MUC2%. Median WHS was highest in dogs with GC. Median KI67% normalised to WHS was highest in the NC group (6.69%; range, 1.70–23.60%). Median GBC% did not correlate with colonic inflammation overall. Median MUC2% normalised to WHS in the NC group (10.02%; range, 3.05–39.09%) was two- and three-fold higher than in the GC and LPC groups respectively. With increased colonic inflammation, despite minimal changes in GBC% overall, MUC2 expression markedly declined in the LPC group (-27.4%; 95%-CI, −49.8, 5.9%) and mildly declined in the GC and NC groups. Granulomatous colitis and LPC likely involve different pathways regulating MUC2 expression. Decreased MUC2 gene expression is observed in dogs with chronic colitis compared to dogs without colonic signs. Changes in MUC2 expression appear influenced by GBC activity rather than quantity in GC and LPC.

中文翻译：

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淋巴浆细胞性结肠炎和肉芽肿性结肠炎犬中 Ki-67、杯状细胞和 MUC2 粘蛋白 RNA 表达的评估

慢性炎症性肠病可能会导致肠道粘液屏障破坏。缺乏评估患有慢性结肠炎的狗的粘液健康状况的研究是由于评估肠道粘液层的固有挑战所致。因此，尚不清楚负责粘液产生和分泌的杯状细胞 (GBC) 数量和/或粘蛋白 2 (MUC2) 表达的减少是否与患有肉芽肿性结肠炎 (GC) 或淋巴细胞浆细胞性结肠炎 (LPC) 的狗的炎症严重程度相关）。 Ki-67 免疫反应性（已在患有小肠炎症的狗中进行过评估）尚未确定是否与 GC 和 LPC 的组织学严重程度相关。研究目标包括比较患有 GC、LPC 和非发炎结肠的狗的 Ki-67 免疫反应性、GBC 群体和 MUC2 表达；并探索使用核糖核酸 (RNAscope®) 原位杂交 (ISH) 评估犬结肠中 MUC2 的表达。在八年的时间里，从 48 只狗身上获得了福尔马林固定的内窥镜结肠活检样本。一位不知情的病理学家审查了所有活组织检查。根据最终的组织病理学诊断，将狗分为 GC (n=19)、LPC (n=19) 或无结肠炎 (NC) (n=10) 组。进行了 Ki-67 免疫组织化学、Alcian-Blue/PAS 染色以突出 GBC，以及使用定制的犬 MUC2 靶向探针进行 RNAscope® ISH。每只狗至少选择5个显微视野，使用图像分析软件测量Ki-67标记指数（KI67%）、GBC染色百分比（GBC%）和MUC2表达（MUC2%）。 Spearman 相关系数用于确定世界小动物兽医协会组织学评分 (WHS) 与测量变量之间的关联。使用线性回归模型比较WHS与KI67%、GBC%和MUC2%之间的关系；且介于 GBC% 和 MUC2% 之间。 GC 犬的 WHS 中位数最高。标准化为 WHS 的中位 KI67% 在 NC 组中最高（6.69%；范围，1.70–23.60%）。总体 GBC% 中位数与结肠炎症无关。 NC 组中按 WHS 归一化的中位 MUC2%（10.02%；范围，3.05-39.09%）分别比 GC 组和 LPC 组高两倍和三倍。随着结肠炎症的增加，尽管 GBC% 总体变化很小，但 MUC2 表达在 LPC 组中显着下降（-27.4%；95%-CI，-49.8，5.9%），在 GC 和 NC 组中略有下降。肉芽肿性结肠炎和 LPC 可能涉及调节 MUC2 表达的不同途径。与没有结肠症状的狗相比，患有慢性结肠炎的狗中观察到 MUC2 基因表达降低。 MUC2 表达的变化似乎受到 GBC 活性的影响，而不是 GC 和 LPC 中数量的影响。