The super-healing MRL strain promotes muscle growth in muscular dystrophy through a regenerative extracellular matrix
Joseph G. O’Brien, … , Alexis R. Demonbreun, Elizabeth M. McNally
Joseph G. O’Brien, … , Alexis R. Demonbreun, Elizabeth M. McNally
Published January 4, 2024
Citation Information: JCI Insight. 2024;9(3):e173246. https://doi.org/10.1172/jci.insight.173246.
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Research Article Muscle biology Stem cells

The super-healing MRL strain promotes muscle growth in muscular dystrophy through a regenerative extracellular matrix

Abstract

The Murphy Roths Large (MRL) mouse strain has “super-healing” properties that enhance recovery from injury. In mice, the DBA/2J strain intensifies many aspects of muscular dystrophy, so we evaluated the ability of the MRL strain to suppress muscular dystrophy in the Sgcg-null mouse model of limb girdle muscular dystrophy. A comparative analysis of Sgcg-null mice in the DBA/2J versus MRL strains showed greater myofiber regeneration, with reduced structural degradation of muscle in the MRL strain. Transcriptomic profiling of dystrophic muscle indicated strain-dependent expression of extracellular matrix (ECM) and TGF-β signaling genes. To investigate the MRL ECM, cellular components were removed from dystrophic muscle sections to generate decellularized myoscaffolds. Decellularized myoscaffolds from dystrophic mice in the protective MRL strain had significantly less deposition of collagen and matrix-bound TGF-β1 and TGF-β3 throughout the matrix. Dystrophic myoscaffolds from the MRL background, but not the DBA/2J background, were enriched in myokines like IGF-1 and IL-6. C2C12 myoblasts seeded onto decellularized matrices from Sgcg–/– MRL and Sgcg–/– DBA/2J muscles showed the MRL background induced greater myoblast differentiation compared with dystrophic DBA/2J myoscaffolds. Thus, the MRL background imparts its effect through a highly regenerative ECM, which is active even in muscular dystrophy.

Authors

Joseph G. O’Brien, Alexander B. Willis, Ashlee M. Long, Jason Kwon, GaHyun Lee, Frank W. Li, Patrick G.T. Page, Andy H. Vo, Michele Hadhazy, Melissa J. Spencer, Rachelle H. Crosbie, Alexis R. Demonbreun, Elizabeth M. McNally

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Figure 4

Reduction in TGF-β proteins in decellularized matrices from Sgcg-MRL muscle compared with Sgcg-D2 muscle.

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Reduction in TGF-β proteins in decellularized matrices from Sgcg-MRL mus...
Decellularized extracellular (dECM) myoscaffolds were generated from Sgcg-MRL and Sgcg-D2 quadriceps muscles. Myoscaffold sections were stained with (A) H&E and (B) Sirius Red, demonstrating removal of cellular content following detergent treatment (1% SDS) with maintenance of matrix components. Control samples were incubated in PBS only (0% SDS). (C) Representative IFM images of dECM myoscaffolds costained with antibodies to detect TGF-β1 (red) and LAMA2 (green). Extracellular TGF-β1 protein expression was dramatically reduced in the MRL background. (D) Z-stack images of TGF-β1 (red) and LAMA2 (green) demonstrate excess TGF-β1 distributed throughout the matrix in the dystrophic D2 model. Original magnification, ×100. (E) Representative IFM images of dECM sections, costained with antibodies to detect TGF-β3 (red) and LAMA2 (green), showing reduction in TGF-β3 in Sgcg-MRL myoscaffolds. (F) dECM myoscaffolds from Sgcg-MRL (top) and Sgcg-D2 (bottom) showed reduced thrombospondin-4 (THBS4, red) and LAMA2 (green) in the Sgcg-MRL muscle. Scale bars: 100 μm (A), 50 μm (left images in C, E, and F), and 20 μm (B, D, and right images in C, E, and F).