Figure 2. CHI3L1 levels are increased in the lungs of pale ear mice, and it does not regulate apoptosis but does regulate fibroproliferative repair in HPS.
WT and pale ear (Hps1ep) mice were employed. One group of WT and pale ear mice was sacrificed at day 3 (after administration of intratracheal PBS). Another cohort of WT and pale ear mice was given intratracheal bleomycin, and CHI3L1 was assessed 3, 7, 10, and 14 days later. (A) Chi3l1 transcript was measured in whole-lung RNA extracts from WT and pale ear mice using qRT-PCR. (B) CHI3L1 protein levels in BAL fluid were quantified using ELISA. (C) TUNEL staining was performed on day 7, and TUNEL-positive type II epithelial cells were counted. (D) Total lung collagen was quantified using Sircol assay on day 14. (E and F) WT, Chi3l1–/–, pale ear, and Hps1ep CHI3L1–/– double mutant mice were subjected to intratracheal bleomycin administration. (E) All TUNEL-positive cells were counted on day 7. (F) Total lung collagen was quantified using Sircol assay on day 14. (G and H) WT, CHI3L1 Tg, pale ear, and Hps1ep CHI3L1 Tg mice were subjected to intratracheal bleomycin administration. (G) CHI3L1 Tg was turned on from day 0 to day 5. All TUNEL-positive cells were counted on day 7. (H) CHI3L1 Tg was turned on from day 5 to day 14. Total lung collagen was quantified using Sircol assay on day 14. Values are mean ± SEM, with 6 mice in each group. Comparisons between groups were conducted by two-way ANOVA with Bonferroni’s post hoc test. **P ≤ 0.01, *P ≤ 0.05. Dox, doxycycline.