Figure 2.

Histological grading of NEC severity in a NEC neonatal mouse model. Pups were subjected to NEC induction protocol and euthanized after 72 h or earlier in case of distress symptoms. Intestines were harvested, fixed in 10% formalin, and stained with hematoxylin–eosin. The severity of experimental NEC was classified from 0 to 4 according to a previously validated scoring system [66], as follows: (A) grade 0: intact villi; (B) grade 1: superficial epithelial cell sloughing; (C) grade 2: partially compromised villi structure, basal cells still present; (D) grade 3: complete villous necrosis, with basal cells still appreciable; (E) grade 4: transmural necrosis, basal membrane destroyed. Samples with histological scores of 2 or higher were considered positive for NEC. An injury score of 3 or 4 defines severe NEC. NEC: necrotizing enterocolitis. Image magnification 100×.