PF4CreTgfb1f/fmice are partially protected from developing CCl4-induced liver fibrosis. (A) Homozygous PF4CreTgfb1f/f mice had >90% less TGF-β1 in their platelets than did their littermate controls, as measured with a Duo-Set enzyme-linked immunosorbent assay (ELISA) kit (n = 7; P < .0001). (B) Depiction of the experimental protocol showing CCl4 or oil challenge time points (indicated by arrows) for the duration of the 36-day experiment. (C) Picrosirius red staining was performed on liver sections of oil- or CCl4-challenged WT or PF4CreTgfb1f/f mice according to the protocol shown in panel B. Fibrotic areas in red (images taken under a normal light microscope) and a mixture of green, red, and yellow fluorescent color pictures (taken under polarized light) showed collagen accumulation (representative images are shown). (D) Quantification of fibrotic areas from images taken with a polarized light microscope showed that PF4CreTgfb1f/f mice had smaller fibrotic areas than those of C57Bl/6 (WT) or littermate control (Tgfb1f/f) mice (percentage of picrosirius red–stained fibrosis areas was 2.5% ± 0.5% in PF4CreTgfb1f/f mice, 3.3% ± 0.7% in WT mice, 3.5% ± 1.7% in Tgfb1f/f mice, and 1.0% ± 0.3% in oil-challenged WT controls; P = .002 for PF4CreTgfb1f/f mice vs WT mice; P = .05 for PF4CreTgfb1f/f vs Tgfb1f/f mice; P < .0001 for CCl4-challenged vs oil-challenged WT mice). (E) Total collagen content in liver tissue was measured by the hydroxyproline assay, with lower collagen levels found in PF4CreTgfb1f/f mice (n = 11) than in WT (n = 9) and Tgfb1f/f (n=-5) mice after CCl4 challenge (P = .1 WT vs PF4CreTgfb1f/f mice; P = .06 Tgfb1f/f vs PF4CreTgfb1f/f mice).
