(A) Quadriceps muscles from 8-week old animals were sectioned and stained with hematoxylin and eosin, showing improved histopathology of TG+ mdx mice compared to mdx controls. The region selected for imaging was selected from the image in S8 Fig (boxed). (B) The fibrosis content of TG+ mdx animals was assessed at 20 weeks using an assay for hydroxyproline, a modified amino acid found in collagen. Shown is hydroxyproline content from quadriceps, gluteus/hamstrings and triceps muscles, each showing reduction in hydroxyproline content in TG+ mdx (n = 7) compared to mdx (n = 8). (C) HEK293T cells were transfected to express heterologously mouse LTBP4 and either TGFβ1, TGFβ2, or TGFβ3. Co-immunoprecipitation was performed on cell lysates by immunoprecipitating with anti-LTBP4 antibody followed by immunoblotting with anti-myc antibody detecting TGFβ1, 2, and 3. A co-IP control for each experiment was performed without adding IP antibody. LTBP4 associated with all three TGFβ isoforms in vitro. Scale bar = 100μm.