Histological sections of lung tissue were stained with Masson’s-Trichrome as described in Materials and Methods. Representative photomicrographs (4 x, 10 x, and 20 x) of lung sections from Bleo +vehicle (panels A-C), Bleo +control exosome injected mice (panels D-F), from Bleo +U-IPFexo injected mice (panels G-I) or from non-fibrotic inducing exosomes (Bronchiectasis, panels J-L). Fibrotic score (M), collagen content (N), αvintegrin (O) increased after Bleo +U-IPFexo treatment. (M) Ashcroft scores were used to evaluate the degree of fibrosis. Data are graphed as the mean score of 32 fields/section of lung. (N) Collagen content was estimated by hydroxyproline assay as described in Methods. Data are graphed as μg/mg of lung tissue. (O) αv-integrin mRNA expression was determined by RT-PCR as a marker of fibrosis. Data are graphed normalized for 18 S content. Each data point represents an individual mouse, n=4–11 technical replicates/group and two biological replicates/group (Figure 9—source data 1) *p<0.05 compared to control exosome treatment or compared to Bleo +vehicle treatment. Data were analyzed using one-way analysis of variance (ANOVA) and Mann-Whitney U test. Scale bar panels A, D, G, J, 200 µm; panels B, E,H, K,100 µm; panels C, F,I,L, 50 µm.