Fig. 2

αv integrins on PDGFRβ⁺ cells regulate skeletal muscle fibrosis via TGFβ activation. a αv expression on PDGFRβ⁺ cells from control and Itgav ^flox/flox;Pdgfrb-Cre (αv Cre) mice using flow cytometry (n = 3). b αv Cre and control mice received intramuscular CTX with muscles harvested at day 21. c Representative images of picrosirius red stained sections 21 days after CTX. Upper panels: scale bar 25 μm, Lower panels: 400 μm. d Digital image analysis quantification of picrosirius red staining in control and αv Cre mice day 21 post CTX or control injection (n = 7). e qPCR of Col1a1 in control and αv Cre PDGFRβ⁺ cells culture-activated for 5 days (n = 7). f qPCR of TGFβ1 in control and αv Cre PDGFRβ⁺ cells culture-activated for 5 days (n = 7). g qPCR of Col1a1 in GFP⁺ cells from mTmG;Pdgfrb-Cre mice cultured with CWHM 12 and control for 5 days (n = 3). h TGFβ activation by control- or CWHM 12-treated GFP⁺ cells from mTmG;Pdgfrb-Cre mice (n = 6). TGFβ activation was assessed alone, with TGFβ–blocking antibody (Anti–TGFβ), and with recombinant human TGFβ1 (rhTGFβ). i Representative images of picrosirius red stained sections from mice treated with CWHM12 or control from the time of CTX. Mice received rhTGFβ1 (lower panels) to the region of injured muscle every 72 h up to 21 days. j Digital image analysis quantitation of picrosirius red stained sections from CWHM12 or control treated mice that received rhTGFβ1 or PBS to the region of injured muscle (n = 5). k Representative images of phospho-SMAD 3 stained sections from control or CWHM12-treated mice. Scale bar 30 μm. l Quantitation of phospho-SMAD 3 stained sections from mice treated with control or CWHM12 from the time of CTX (n = 10). m Force required for passive elongation of muscles 21 days following intramuscular CTX in mice treated with CWHM 12 or control (n = 9). n Laceration-induced skeletal muscle fibrosis model dosing regime. o Representative images of picrosirius red stained sections from control and CWHM 12 treated mice. Scale bar 25 μm. p Digital image analysis quantitation of picrosirius red staining in CWHM12 and control treated mice (n = 10). Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01 (Student’s t-test)