Various HA surface receptors contribute to HA clearance in the lung with different outcomes on pulmonary fibrosis. (A) H&E histology on lung tissue of mice treated with bleomycin (Bleo; 10 mg/kg body weight twice a week intraperitoneally) or with bleomycin + Lyve1 antibody (Bleo + Lyve1-AB; (10 mg/kg body weight twice a week intraperitoneally; 100 μg Lyve1-AB 5 times every other day intraperitoneally, starting at day 15 after the first bleomycin injection) at day 28 (Bleo n = 5, Bleo + Lyve1-AB n = 5, control n = 2). Scale bars equal 200 μm. (B) Quantitative analysis of the percentage increase in the area of lung tissue of bleomycin and bleomycin + Lyve1 antibody-treated mice above PBS-treated control (100 μL twice a week intraperitoneally) mice. (C) Quantitative analysis of FSP-positive cells on lung tissue Bleo and Bleo + Lyve1-AB–treated mice in comparison to control mice. (D) Immunodetection of CD44-positive cells (CD44) and Mac-2–positive macrophages (Mac-2) in lungs of PBS- (control) and bleomycin-treated (Bleo) mice at day 28. Scale bars equal 100 μm. (E) Quantitative analysis of the percentage increase in the area of lung tissue of mice that first received either wild-type (WT-BM Bleo) or CD44-deficient (CD44^−/− BM Bleo) BM (recipients were irradiated with 10 gray, after 24 hours 5 × 10⁶ BM cells of WT or CD44-deficient donor mice were injected intravenously into the tail vein) and were then treated with bleomycin (10 mg/kg body weight twice a week intraperitoneally, starting day 21 after transplantation) above PBS-treated control mice (control; recipients were irradiated with 10 gray, after 24 hours 5 × 10⁶ BM cells of CD44-deficient donor mice were injected intravenously into the tail vein); 100 μL PBS twice a week intraperitoneally, starting day 21 after transplantation) mice (WT-BM Bleo n = 5, CD44^−/− BM Bleo n = 7, CD44^−/− BM PBS n = 4). (F) Quantitative analysis of FSP-positive cells on lung tissue of WT-BM Bleo and CD44^−/− BM Bleo mice in comparison with control mice. (G) Quantitative analysis of hyaluronan-levels (HA) in plasma at day 28 of PBS, Bleo, WT-BM Bleo, CD44^−/− BM Bleo and Bleo + Lyve1-AB–treated mice. (H) Quantitative analysis of hyaluronan-levels (HA) in lungs at day 28 of PBS, Bleo, WT-BM Bleo, CD44^−/− BM Bleo and Bleo + Lyve1-AB–treated mice. Error bars show SEM.