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 3

Satellite cells from D2-mdx mice show limited myogenic capacity during spontaneous muscle regeneration.

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Satellite cells from D2-mdx mice show limited myogenic capacity during s...
(A–C) Gene expression of Pax7, MyoD, and myogenin from 21- and 38-day-old D2-WT (n = 3 per age), D2-mdx (n = 4 per age), and B10-mdx (n = 3 per age) mice. (D) Immunofluorescence (IF) images stained for labeling Pax7+ satellite cells in intact areas of the triceps muscle from 38-day-old B10-mdx and D2-mdx mice. White arrowheads, Pax7+ cells. (E) Quantification of the total number of Pax7+ cells per area (mm2) in B10-mdx (n = 8) and D2-mdx (n = 8) muscles. (F) IF images stained for labeling Pax7+ satellite cells in damaged areas of the triceps muscle from 38-day-old B10-mdx and D2-mdx mice. White arrowheads, Pax7+ cells. (G) Quantification of the total number of Pax7+ cells per area (mm2) in muscles from B10-mdx (n = 6) and D2-mdx (n = 9). (H) Schematic figure demonstrating the pattern for pulsed 5′-bromo-2′-deoxyuridine (BrdU) labeling of proliferating satellite cells. (I) Quantification of BrdU+ CNFs relative to total fibers per muscle section (n = 3 for each labeling period per genotype). (J) IF images from the triceps muscle from 38-day-old B10-mdx and D2-mdx mice labeled with BrdU for 9 days. White arrowheads, BrdU+ CNFs. (K) Quantification of the total number of BrdU+ CNFs after 6–9 days of BrdU labeling in muscle sections from 38-day-old B10-mdx (n = 6) and D2-mdx (n = 6) mice. For A, B, and C, *P < 0.05, ***P < 0.001, and ****P < 0.000; 1-way ANOVA with Tukey’s post hoc comparison; for E, G, I, and K, **P < 0.01, ***P < 0.001, and ****P < 0.0001; 2-tailed, nonparametric Mann-Whitney U test. Scale bars: 50 µm (D, F, and J).