Stabilizing Ryanodine Receptors Improves Left Ventricular Function in Juvenile Dogs With Duchenne Muscular Dystrophy

Area of Science:

• Cardiology
• Molecular Biology
• Genetics

Background:

• Duchenne muscular dystrophy causes progressive left ventricular (LV) dysfunction.
• Golden Retriever Muscular Dystrophy (GRMD) dogs model this condition, showing early LV dysfunction.
• GRMD dogs exhibit progressive deterioration in cardiac function from an early age.

Purpose of the Study:

• To evaluate the cardioprotective effects of ARM036 in young GRMD dogs.
• ARM036 stabilizes the cardiac sarcoplasmic reticulum ryanodine receptor/calcium release channel (RyR2).
• Investigate ARM036's impact on cardiac function and cellular mechanisms in GRMD dogs.

Main Methods:

• GRMD dogs and healthy controls were treated with ARM036 or placebo for 4 months.
• Cardiac function assessed using echocardiography (conventional and 2D speckle-tracking).
• Cellular and molecular analyses included single-channel measurements and myofilament studies.

Main Results:

• GRMD dogs showed reduced global longitudinal strain and hypokinetic segments, indicating early LV dysfunction.
• GRMD cardiomyocytes exhibited increased RyR2 open probability and altered cross-bridge cycling kinetics.
• ARM036 treatment prevented these cardiac dysfunctions and normalized myocyte function.

Conclusions:

• GRMD dogs develop early LV dysfunction linked to altered myofilament properties.
• Pharmacological stabilization of RyR2 with ARM036 effectively prevented these cardiac abnormalities.
• ARM036 demonstrates potential as a therapeutic agent for muscular dystrophy-associated cardiomyopathy.