Intestinal histology and mucosal function

Histomorphology of the intestine and measurement of enzyme activity formalin-fixed tissue samples from distal jejunum were dehydrated in ethanol and embedded in paraffin, and stained with hematoxylin and eosin. Morphometric analysis of villus height (µm), crypt depth (µm), enterocyte height (µm), number of infiltrating epithelium lymphocytes per 100 enterocytes (IEL/100E), number of goblet cells per 100 enterocytes (goblet cells/100E) were done with Zen Blue 3.0 software at ALAB Weterynaria (Warsaw, Poland). Histopathological lesions (infiltration of the stromal mucosa, mucosal epithelium, brush border, intestinal blunting, cell detritus rich in eosinophils, eosin, edema of stromal mucosa, vessel dilation in stromal mucosa of villi, infiltration of submucosa, edema of submucosa, hyperplasia of enterocytes, cell detritus in the villi surface, number of mitoses in intestinal crypts, hyperemia, vacuolization of neurons) were assigned to a 5-point scale (0 = no pathological changes, 1 = minimal, 2 = mild, 3 = moderate and 4 = marked). The gut-associated lymphoid tissue evaluation included the number of lymphoid follicles visible in intestinal sections.

As a marker of gut mucosal function, we measured the activity of aminopeptidase N, aminopeptidase A, dipeptidyl IV, maltase, sucrase, and lactase in distal jejunum SI, using the assay as described in Sangild et al. [31].