Sickle cell anemia mice develop a unique cardiomyopathy with restrictive physiology

Area of Science:

• Cardiology
• Hematology
• Molecular Biology

Background:

• Cardiopulmonary complications are the primary cause of mortality in sickle cell anemia (SCA).
• Existing research describes elevated tricuspid regurgitant jet velocity, pulmonary hypertension, diastolic, and autonomic dysfunction in SCA, but a unifying pathophysiology remains elusive.
• The propensity for sudden death in SCA patients necessitates a deeper understanding of cardiac dysfunction.

Purpose of the Study:

• To determine the underlying basis of cardiac dysfunction in sickle cell anemia (SCA).
• To identify a unifying pathophysiology that explains the poor prognosis and sudden death observed in SCA patients.
• To investigate the transition from hyperdynamic to restrictive physiology in the SCA heart.

Main Methods:

• Longitudinal comprehensive cardiac analysis in SCA mice.
• Integration of advanced cardiac imaging (including cardiac MRI), electrocardiography, histopathology, and molecular analysis.
• Transcriptome analysis to identify gene expression changes associated with cardiac dysfunction.

Main Results:

• SCA mice exhibited a gradual transition from anemia-induced hyperdynamic physiology to restrictive physiology, characterized by left atrial enlargement and diastolic dysfunction with preserved systolic function.
• Restrictive physiology was linked to cardiomyocyte loss, secondary fibrosis, increased extracellular volume, and ultrastructural mitochondrial damage indicative of chronic hypoxia/ischemia.
• Gene expression analysis revealed dysregulation of pathways involved in angiogenesis, extracellular matrix remodeling, circadian rhythm, oxidative stress, hypoxia, ion-channel transport, and cardiac conduction.
• Progressive corrected QT prolongation, arrhythmias, and ischemic changes were observed in SCA mice preceding sudden death.

Conclusions:

• The study identifies a unifying cardiac pathophysiology for sickle cell anemia (SCA), explaining diverse cardiac abnormalities and sudden death.
• The findings suggest that progressive restrictive physiology, driven by cardiomyocyte loss and fibrosis, underlies the cardiac complications in SCA.
• The observed cardiac dysfunction and arrhythmias in SCA mice may mirror the mechanisms leading to sudden cardiac death in human restrictive cardiomyopathies and long QT syndromes.