Fig. 5.

TLR4 blockade during recovery from DSS colitis impairs mucosal healing and epithelial proliferation. A: treatment schedule for anti-TLR4 antibody and isotype control during recovery from DSS colitis. Mice were injected intraperitoneally (ip) at the indicated time points. B: there were no clinical differences between mice treated with anti-TLR4 antibody or isotype control during recovery from DSS colitis as measured by DAI. Data represent the mean ± SE of 2 independent experiments with a total of 22 mice (n = 12 for anti-TLR4 and n = 10 for isotype control-treated mice). C: histological assessment of colitis severity in anti-TLR4 antibody- and isotype control-treated mice. Data represent the mean histological score ± SE for mice from 2 independent experiments (n = 4 for anti-TLR4 and n = 4 for isotype). Anti-TLR4 antibody-treated mice failed to recover from DSS-induced damage with higher total histological damage scores at day 14. Specifically, whereas isotype control mice had begun to repair mucosal damage caused by DSS, the anti-TLR4 antibody-treated mice had persistent crypt damage and ulceration at day 14. *P < 0.05. D: representative microscopic pictures of hematoxylin and eosin (H&E) staining of colon sections from anti-TLR4 antibody and isotype control-treated mice. Arrows indicate areas of persistent crypt damage and ulceration in an anti-TLR4-treated mouse colon section. E: epithelial proliferation was measured by bromodeoxyuridine (BrdU) labeling index (number of BrdU-positive cells per crypt at ×400 magnification). Data represent means ± SE for mice from 2 independent experiments (n = 4 for anti-TLR4 and n = 4 for isotype). *P < 0.05. F: representative photo of immunohistochemical staining of incorporated BrdU into colonic epithelium. Proliferating cells labeled with BrdU have brown nuclei as indicated by the arrows.