Thin-filament-based modulation of contractile performance in human heart failure

Area of Science:

• Cardiovascular Biology
• Muscle Physiology
• Cardiac Pathophysiology

Background:

• The role of the sarcomere's thin filament in human cardiomyopathy contractile dysfunction remains unclear.
• Understanding thin filament alterations is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the functional characteristics of native thin filaments in human failing and nonfailing hearts.
• To determine the impact of left ventricular assist device (LVAD) support on thin filament function.
• To elucidate the molecular mechanisms, particularly phosphorylation, underlying thin filament dysfunction in cardiomyopathy.

Main Methods:

• Isolation and functional characterization of intact (native) thin filaments from human ventricular tissue.
• Utilized in vitro motility and force assays to assess thin filament performance.
• Analyzed protein kinase C (PKC) isoform expression in myocardial tissue.

Main Results:

• Failing human ventricular thin filaments showed increased maximal velocity but decreased maximal contractile force.
• Thin filaments from hearts supported by LVAD exhibited significantly increased contractile force.
• Dephosphorylation of failing thin filaments largely restored normal function, indicating a phosphorylation-dependent mechanism.
• Increased expression of PKC isoforms alpha, beta1, and beta2 was observed in failing myocardium, decreasing after LVAD support.

Conclusions:

• The thin filament is a critical determinant of contractile performance in the failing human heart.
• LVAD support effectively restores near-normal thin filament function.
• Phosphorylation, likely mediated by protein kinase C, is the primary mechanism driving thin filament dysfunction in human cardiomyopathy.