Background: Intestinal macrophages are key regulators of gastrointestinal homeostasis and inflammation in several species, but their role in equine IBD remains poorly understood.
Objectives: The study aimed to 1) Compare macrophage count between duodenal biopsies and their full thickness counterpart, 2) Quantify duodenal macrophages in horses with IBD. Animals: Five horses were examined postmortem and 30 horses (with and without IBD) underwent duodenal biopsies at the equine hospital (CHUV).
Methods: Full-thickness and endoscopic biopsies of the duodenum were obtained postmortem. Duodenal biopsies were performed in 30 horses by gastroduodenoscopy with endoscopic forceps. Tissues were stained immunohistochemically to identify M2 macrophages (CD204) and pan-macrophages (Iba-1). Histomorphometric analysis quantified macrophages within the lamina propria of villi (a), the deep lamina propria (b) and the sub-cryptal area (c). Agreement between biopsies and full-thickness tissues was assessed with intra-class correlation, while T-tests compared macrophage count between IBD and non-IBD horses.
Results: Data revealed that biopsies tend to underestimate CD204 and Iba-1 positive macrophages compared to full-thickness tissues. T-tests indicates significant differences in macrophage count between horses with and without IBD. IBD horses showed significantly higher number of Iba-1 positive macrophages in the lamina propria of villi (t = 3.44, p = 0.003) and in all three lamina propria layers combined (a+b+c; t = 2.34, p = 0.028), compared to horses without IBD. Conclusions and Clinical importance: IBD horses have significantly higher numbers of duodenal mucosal macrophages, which highlights their potential importance in the diagnostic process and clinical management.
