Fig 1: Chitinase 3-like-1 (Chi3l1)/CD44 signaling in M?s upregulates podoplanin expression and platelet adhesion.(A) Male WT, Chil1-/-, Cd44-/- mice were treated with acetaminophen (APAP) (n = 4 mice/group). After 3 hr, mice were sacrificed and M?s were isolated to measure mRNA levels of various adhesion molecules, including selectin P ligand (Selplg), Cd40, melanoma cell adhesion molecule (Mcam), Fc receptor (Fcr), intercellular adhesion molecule 1 (Icam1), lymphocyte function-associated antigen 1 (Lfa1), von Willebrand factor (Vwf), and podoplanin (Pdpn). (B, C) Wild-type (WT) mice were treated with APAP. Chil1-/- and Cd44-/- mice were treated with PBS or rmChi3l1 followed by APAP challenge simultaneously and mice were sacrificed 3 hr after APAP (n = 3 mice/group). (B) M?s were isolated and mRNA levels of Pdpn in M?s were analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). (C) Immunofluorescence (IF) staining of liver sections for podoplanin and F4/80 is shown and the proportions of M?s that express Pdpn were quantified, Scale bar, 25 µm. (D–F) Chil1-/- mice reconstituted with rmChi3l1 were treated with either Ctrl IgG or a-podoplanin Ab for 16 hr and subsequently challenged with APAP. (D) Serum levels of ALT and (E) liver histology were evaluated 24 hr after APAP treatment (n = 6 mice/group). Scale bar, 250 µm. (F) IF staining for intrahepatic platelets (CD41+) and M?s (F4/80+) was performed 3 hr after APAP (n = 3 mice/group). Scale bar, 25 µm. One-way ANOVA were performed in A–C. Two-tailed, unpaired Student’s t-test was performed in D.