Histological Scoring of Lung and Colon Injury

We obtained partial sections of lung tissues and colon tissues. We routinely fixed the tissue with 4% paraformaldehyde and then gradient dehydration. The samples were cut, embedded in paraffin, bleached, and stained in hematoxylin and eosin (H&E). The score of lung injury and colon injury was performed by other investigators who were blinded to the study. For the lung injury, scoring principles were as follows: (1) alveolar congestion, (2) hemorrhage, (3) infiltration of neutrophils in the airspace or vessel wall, and (4) thickness of the alveolar wall formation. Each lung injury item was scored as follows: no damage or minimal damage = 0, mild damage = 1, moderate damage = 2, severe damage = 3, and diffuse injury = 4. Then, the lung injury was scored according to previous study and all scores were added up to obtain a total score [23 (link), 24 (link)]. Besides, the total histological score for colon injury ranges from 0 to 8 according to previous study as follows: epithelium: normal morphology = 0, loss of goblet cells = 1, loss of goblet cells in large areas = 2, loss of crypts = 3, and loss of crypts in large areas = 4; infiltration: no infiltrate = 0, infiltrate around crypts = 1, infiltrate into the lamina muscularis mucosae = 2, extensive infiltration into the lamina muscularis mucosae and thickening of the mucosa = 3, and infiltration of the submucosal layer = 4 [25 (link)].