Growth and macrophage analysis in mice treated with CSF-1 during concurrent hyperoxia exposure. Body weights of mice treated with CSF-1 (Hyp + CSF-1; purple line) or PBS (Hyp + PBS; blue line) during hyperoxia exposure compared to normoxic mice (Norm; red line) (A). n = 4-13 mice/time point. Data were analysed using a two-way ANOVA and Bonferonni post-hoc test. `b’ represents significant difference between Norm and Hyp + CSF-1, `c’ represents significant difference between Hyp + PBS and Hyp + CSF-1. ***p < 0.001. Flow cytometric analysis of littermate lungs at P5 following treatment with CSF-1 or PBS during hyperoxia. Total lung cells (B) were gated on csf1r-EGFP+ CD45+ cells to quantitate CSF-1R+ cell number and proportion (C) after CSF-1 (E) and PBS treatment (D). F4/80 expression demarcates mature macrophages within the CSF-1R+ population (F-H). Histograms revealing gating procedure for F4/80 expression in representative PBS (G) and CSF-1-treated lungs (H). Staining (blue) is overlayed with an isotype control (red). n = 3 littermate lungs/treatment. Data were analysed using two-tailed unpaired t-tests. Photomicrographs of Norm (I), Hyp + PBS (J) and Hyp + CSF-1 (K) lungs at P35 stained with H&E demonstrated fewer, larger alveoli with hyperoxia exposure (J & K).