Fig 2: CNS YKL-40 changes following surgery in mice and humans. Mouse brains were collected from aged mice 24 h following tibial fracture or from naïve unoperated control mice. A) Representative immunohistochemical images of YKL-40 protein expression in the dentate gyrus of the hippocampus. B) The percent area of YKL-40 immunostaining was lower in the tibial surgery mice vs naïve controls. C) RT-PCR of Ykl-40 mRNA expression expressed as log2 of fold changes in the hippocampus found that Ykl-40 levels were reduced following tibial fracture. Interestingly, RT-PCR Il1-B log 2 of fold change in the hippocampus analysis showed increased Il1-B levels following tibial fracture. D) YKL-40 levels in CSF samples from human surgery patients examined before and 24 h after surgery revealed a significant decrease in YKL-40 in the CSF following surgery. E) Individual patient's preoperative and postoperative levels are represented in grey (normal) or colored (patients with delirium). F) Patients were divided into 2 groups: normal and patients with delirium. CSF YKL-40 change levels (24 h vs preoperative) between normal and patients with delirium. Mouse data are expressed as mean ± SEM, and human data as mean ± SD except for CSF YKL-40 data, which are expressed as Median ± (interquartile range). Analyses were performed as follows: Unpaired Student's t-test, Wilcoxon Rank Sum Test when appropriate, *p < 0.05. Representative scale for A) is 50 µm. Note: Individual dot colors represent the same patient with delirium across panels E and F. . (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)