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Updated: Apr 17, 2026
Isolation, Culture, and Functional Characterization of Adult Mouse Cardiomyoctyes
Published on: September 24, 2013
Irreversible triggers for hypertrophic cardiomyopathy are established in the early postnatal period
Leah Cannon1, Ze-Yan Yu2, Tadeusz Marciniec1
1Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, Australia.
Insights
Early genetic defects in hypertrophic cardiomyopathy (HCM) cause irreversible heart muscle changes. Intervening early is crucial for preventing pathological left ventricular hypertrophy (LVH) in HCM.
Area of Science:
- Cardiovascular Medicine
- Genetics
- Molecular Biology
Background:
- Hypertrophic cardiomyopathy (HCM) stems from sarcomere protein gene mutations.
- Left ventricular hypertrophy (LVH) is an adaptive response to sarcomere dysfunction.
- The role of persistent mutant gene expression versus early inductive triggers in LVH remains unclear.
Purpose of the Study:
- Investigate the reversibility of pathological LVH in a murine model of HCM.
- Determine the impact of early versus late intervention on HCM progression.
Main Methods:
- Generated a regulatable double-transgenic mouse model (tTAxαMHCR403Q) for conditional expression of the α-myosin heavy chain (MHC) Arg403Gln mutation.
- Administered doxycycline to inhibit transgene expression at various developmental stages (0-40 weeks).
- Assessed cardiac structure, function, fibrosis, and myofibrillar disarray.
Main Results:
- Untreated mice developed significant LVH, contractile dysfunction, disarray, and fibrosis.
- Early doxycycline treatment (conception to 6 weeks) markedly reduced LVH and fibrosis at 40 weeks.
- Late transgene inhibition (from 20 weeks) did not alter LV parameters compared to continuous expression, and inhibition from 6 weeks only reduced fibrosis, not LVH.
Conclusions:
- Early postnatal gene expression is critical for HCM pathogenesis.
- Mutant sarcomeres induce irreversible cardiomyocyte defects leading to LVH.
- Mutation-silencing therapies for HCM are likely ineffective for regression and must be initiated very early to prevent hypertrophy.
Background:
Hypertrophic cardiomyopathy (HCM) is caused by mutations in sarcomere protein genes, and left ventricular hypertrophy (LVH) develops as an adaptive response to sarcomere dysfunction. It remains unclear whether persistent expression of the mutant gene is required for LVH or whether early gene expression acts as an immutable inductive trigger.
Objectives:
The aim of this study was to use a regulatable murine model of HCM to study the reversibility of pathological LVH.
Methods:
The authors generated a double-transgenic mouse model, tTAxαMHCR403Q, in which expression of the HCM-causing Arg403Gln mutation in the α-myosin heavy chain (MHC) gene is inhibited by doxycycline administration. Cardiac structure and function were evaluated in groups of mice that received doxycycline for varying periods from 0 to 40 weeks of age.
Results:
Untreated tTAxαMHCR403Q mice showed increased left ventricular (LV) mass, contractile dysfunction, myofibrillar disarray, and fibrosis. In contrast, mice treated with doxycycline from conception to 6 weeks had markedly less LVH and fibrosis at 40 weeks. Transgene inhibition from 6 weeks reduced fibrosis but did not prevent LVH or functional changes. There were no differences in LV parameters at 40 weeks between mice with transgene inhibition from 20 weeks and mice with continuous transgene expression.
Conclusions:
These findings highlight the critical role of the early postnatal period in HCM pathogenesis and suggest that mutant sarcomeres manifest irreversible cardiomyocyte defects that induce LVH. In HCM, mutation-silencing therapies are likely to be ineffective for hypertrophy regression and would have to be administered very early in life to prevent hypertrophy development.
