Platelet HYAL2 mediates susceptibility to colitis. Mice received adoptive transfer of 8 × 10⁸ WT or KO platelets as indicated at the onset of DSS treatment. (A) Cross-sections of distal colon collected from mice after 7 days of 2.5% DSS. Hematoxylin-eosin staining reveals the cellular and structural changes in the intestine, including inflammatory leukocyte infiltration. Boxed regions are enlarged in adjacent panels. Scale bars indicate 500 μm. L denotes the intestinal lumen, triangles indicate the epithelial layer, S denotes the submucosa, and arrows indicate the muscularis mucosae. (B) The percentage of platelets expressing HYAL2 in KO mice receiving WT platelets assessed by using flow cytometry. (C) Body weight was measured on day 7 and compared with starting weight. (D) Mice were scored for outward signs of disease, including weight loss, hunched posture, ruffled fur, bloody stools, and rectal prolapse. (E) Distal colon sections from mice after 7 days of DSS were scored for pathologic changes, including erosion of the epithelial layer, leukocyte infiltration, submucosal swelling, muscularis mucosae hyperplasia, and increased vascularization. (F) Colons from mice euthanized after 7 days of DSS were measured for distance (centimeters) from the distal end of the cecum to the rectum. Symbols indicate genotypes and treatment: (∇) KO mice transfused with WT platelets, n = 8; and (♦) KO mice transfused with KO platelets, n = 8. Data are reported as mean ± SEM. *P < .05; **P < .01.