TGF-β–driven muscle degeneration and failed regeneration underlie disease onset in a DMD mouse model
Davi A.G. Mázala, James S. Novak, Marshall W. Hogarth, Marie Nearing, Prabhat Adusumalli, Christopher B. Tully, Nayab F. Habib, Heather Gordish-Dressman, Yi-Wen Chen, Jyoti K. Jaiswal, Terence A. Partridge
Davi A.G. Mázala, James S. Novak, Marshall W. Hogarth, Marie Nearing, Prabhat Adusumalli, Christopher B. Tully, Nayab F. Habib, Heather Gordish-Dressman, Yi-Wen Chen, Jyoti K. Jaiswal, Terence A. Partridge
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Research Article Cell biology Muscle biology

TGF-β–driven muscle degeneration and failed regeneration underlie disease onset in a DMD mouse model

Abstract

Duchenne muscular dystrophy (DMD) is a chronic muscle disease characterized by poor myogenesis and replacement of muscle by extracellular matrix. Despite the shared genetic basis, severity of these deficits varies among patients. One source of these variations is the genetic modifier that leads to increased TGF-β activity. While anti–TGF-β therapies are being developed to target muscle fibrosis, their effect on the myogenic deficit is underexplored. Our analysis of in vivo myogenesis in mild (C57BL/10ScSn-mdx/J and C57BL/6J-mdxΔ52) and severe DBA/2J-mdx (D2-mdx) dystrophic models reveals no defects in developmental myogenesis in these mice. However, muscle damage at the onset of disease pathology, or by experimental injury, drives up TGF-β activity in the severe, but not in the mild, dystrophic models. Increased TGF-β activity is accompanied by increased accumulation of fibroadipogenic progenitors (FAPs) leading to fibro-calcification of muscle, together with failure of regenerative myogenesis. Inhibition of TGF-β signaling reduces muscle degeneration by blocking FAP accumulation without rescuing regenerative myogenesis. These findings provide in vivo evidence of early-stage deficit in regenerative myogenesis in D2-mdx mice and implicates TGF-β as a major component of a pathogenic positive feedback loop in this model, identifying this feedback loop as a therapeutic target.

Authors

Davi A.G. Mázala, James S. Novak, Marshall W. Hogarth, Marie Nearing, Prabhat Adusumalli, Christopher B. Tully, Nayab F. Habib, Heather Gordish-Dressman, Yi-Wen Chen, Jyoti K. Jaiswal, Terence A. Partridge

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Figure 5

Staggered BrdU labeling after synchronized NTX-induced injury in TA muscles from B10-mdx and D2-mdx mice.

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Staggered BrdU labeling after synchronized NTX-induced injury in TA musc...
(A) IF images from B10-mdx and D2-mdx NTX-injected TAs labeled with BrdU from 24 to 48 hours postinjury (day 1 labeling). White arrowheads, BrdU+ CNFs. (B) Percentage of BrdU+ CNFs across the 6-day labeling period after NTX-injury: B10-mdx (n = 5 for day 1; n = 5 for day 2; n = 4 for days 3 and 4; n = 4 for days 5 and 6 post-BrdU) and D2-mdx (n = 4 for day 1; n = 4 for day 2; n = 4 for days 3 and 4; n = 4 for days 5 and 6 post-BrdU). (C) IF images stained for labeling Pax7+ cells in NTX-injured TAs from B10-mdx and D2-mdx mice. White arrowheads, Pax7+ cells. (D) Quantification of the total number of Pax7+ cells per area (mm2) at 5–6 days postinjury in NTX-injured TAs from B10-mdx (n = 7) and D2-mdx (n = 8). (E–G) Percentage of CNFs, calcification, and total area of degeneration from B10-mdx (n = 4 for CTL, and n = 5 for NTX TAs) and D2-mdx (n = 4 for CTL, and n = 5 for NTX TAs). (H–J) Quantification and IF images for PDGFRα+ cells 14 days after NTX injury of TA muscles from B10-mdx and D2-mdx mice (injury was performed at 24 days of age). (H) Quantification of PDGFRα+ areas shown as a percentage of total muscle section from B10-mdx (n = 6) and D2-mdx mice (n = 5). For B and D–H, *P < 0.05, **P < 0.01, and ***P < 0.001; 2-tailed, nonparametric Mann-Whitney U test (B, D, and H); **P < 0.01, and ****P < 0.0001; 1-way ANOVA with Tukey’s post hoc comparison (E–G). Scale bars: 50 μm.