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 6

Decellularized myoscaffolds from Sgcg-MRL muscle promote differentiation of C2C12 myoblasts into myotubes.

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Decellularized myoscaffolds from Sgcg-MRL muscle promote differentiation...
Experiments similar to those in Figure 5 were conducted, except that myoblasts were seeded at higher density to promote fusion to myotubes. (A) C2C12 myoblasts were seeded at high density onto myoscaffolds and differentiated. (B) Imaging of C2C12 myoblasts seeded onto Sgcg-MRL (top) and Sgcg-D2 (bottom) dECM myoscaffolds costained with antibodies against MyHC-2B (red) and LAMA2 (green), and with Hoechst (blue). Myoblasts were seeded onto 3 biological replicates per cohort and 6 images were analyzed. Original magnification, ×20. Scale bars: 50 μm. (C) The area of MyHC-2B was significantly greater on Sgcg-MRL myoscaffolds (Sgcg-MRL 2,736 and Sgcg-D2 1,143 μm2). (D) Singly nucleated myofibers were increased on Sgcg-D2 dECMs (69.2%) compared with Sgcg-MRL dECMs (42.8%). There was significantly more myofibers with 3 or more nuclei on Sgcg-MRL dECMs (33.7%) compared with Sgcg-D2 dECMs (11.1%), indicating enhanced myotube formation. Data are presented as mean ± SD. ****P < 0.0001 by 2-tailed Student’s t test (C) or 2-way ANOVA with Tukey’s multiple-comparison test (D).