AAV9 gene transfer of cMyBPC N-terminal domains ameliorates cardiomyopathy in cMyBPC-deficient mice
Jiayang Li, … , Rajesh Ramachandran, Julian E. Stelzer
Jiayang Li, … , Rajesh Ramachandran, Julian E. Stelzer
Published August 4, 2020
Citation Information: JCI Insight. 2020;5(17):e130182. https://doi.org/10.1172/jci.insight.130182.
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Research Article Cardiology

AAV9 gene transfer of cMyBPC N-terminal domains ameliorates cardiomyopathy in cMyBPC-deficient mice

Abstract

Decreased cardiac myosin-binding protein C (cMyBPC) expression due to inheritable mutations is thought to contribute to the hypertrophic cardiomyopathy (HCM) phenotype, suggesting that increasing cMyBPC content is of therapeutic benefit. In vitro assays show that cMyBPC N-terminal domains (NTDs) contain structural elements necessary and sufficient to modulate actomyosin interactions, but it is unknown if they can regulate in vivo myocardial function. To test whether NTDs can recapitulate the effects of full-length (FL) cMyBPC in rescuing cardiac function in a cMyBPC-null mouse model of HCM, we assessed the efficacy of AAV9 gene transfer of a cMyBPC NTD that contained domains C0C2 and compared its therapeutic potential with AAV9-FL gene replacement. AAV9 vectors were administered systemically at neonatal day 1, when early-onset disease phenotypes begin to manifest. A comprehensive analysis of in vivo and in vitro function was performed following cMyBPC gene transfer. Our results show that a systemic injection of AAV9-C0C2 significantly improved cardiac function (e.g., 52.24 ± 1.69 ejection fraction in the C0C2-treated group compared with 40.07 ± 1.97 in the control cMyBPC–/– group, P < 0.05) and reduced the histopathologic signs of cardiomyopathy. Furthermore, C0C2 significantly slowed and normalized the accelerated cross-bridge kinetics found in cMyBPC–/– control myocardium, as evidenced by a 32.41% decrease in the rate of cross-bridge detachment (krel). Results indicate that C0C2 can rescue biomechanical defects of cMyBPC deficiency and that the NTD may be a target region for therapeutic myofilament kinetic manipulation.

Authors

Jiayang Li, Ranganath Mamidi, Chang Yoon Doh, Joshua B. Holmes, Nikhil Bharambe, Rajesh Ramachandran, Julian E. Stelzer

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Figure 7

Stretch activation responses in WT and cMyBPC–/– myocardial preparations before and following C0C2 peptide incubation.

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Stretch activation responses in WT and cMyBPC–/– myocardial preparations...
(A) Shown is a typical force trace in response to a sudden 2% stretch in muscle length (ML) in an isometrically contracting WT cardiac muscle preparation at a SL of 2.1 μm. Highlighted are the important phases of the force response and various stretch activation parameters that are derived from the response. Phase 1 shows the immediate increase in force in response to the sudden 2% stretch in ML. P1 is the magnitude of the immediate force response that is measured from the prestretch isometric steady-state force to the peak of phase 1. Phase 2 represents the rapid decline in the force with a dynamic rate constant krel, an index of XB detachment rate. Phase 3 represents the delayed force development with a dynamic rate constant kdf, an index of XB recruitment rate (please see Methods for further details). Measurements in the skinned ventricular preparations were first made under basal conditions (no peptide incubation). Measurements were again made on the same preparations following a 10-minute incubation with 1.0 μM C0C2 peptide incubation. (B and C) Percent decreases in the rates of XB detachment (krel) and XB recruitment (kdf) following a 10-minute incubation with 1.0 μM C0C2 peptide incubation. n = 4 hearts per group. Incubation with C0C2 peptide resulted in significant slowing of krel and kdf in cMyBPC–/– but not in the WT preparations. (D and F) Representative WT (D) and in cMyBPC–/– (F) stretch activation traces highlighting the changes in kdf, which was significantly slowed in cMyBPC–/– group, as indicated by a delay in the achievement of peak of XB recruitment phase (red arrow) for trace obtained after C0C2 incubation versus black arrow for trace obtained before C0C2 incubation. No such delay in the achievement of peak of XB recruitment phase was observed in the WT group. (E and G) Expanded views are shown below to demonstrate that krel is significantly slowed following C0C2 peptide incubation in the cMyBPC–/– group but not in the WT group, as indicated by delayed achievement of the nadir of the force decay in cMyBPC–/– preparations following C0C2 incubation. Values are expressed as mean ± SEM. Significance was determined by 1-way ANOVA with Tukey’s multiple comparisons test. *P < 0.05 by paired t test comparing krel and kdf rates before and after incubation with C0C2 peptide.