The β_IV-Spectrin/STAT3 Complex Regulates the Orientation of Cardiac Hypertrophic Growth

Area of Science:

• Cardiovascular Biology
• Cellular Mechanics
• Molecular Cardiology

Background:

• Cardiac hypertrophy, an increase in heart size due to stress, elevates risks for heart failure and arrhythmia.
• The orientation of cardiac cell growth during hypertrophy significantly impacts cardiac function, but regulatory mechanisms remain unclear.
• β_IV-spectrin and signal transducer and activator of transcription 3 (STAT3) signaling are investigated for their roles in directing hypertrophic growth orientation.

Purpose of the Study:

• To investigate the role of β_IV-spectrin and STAT3 in regulating the orientation of cardiac hypertrophy.
• To determine how altered STAT3 signaling and β_IV-spectrin interaction influence myocyte geometry and cardiac function under stress.
• To explore therapeutic strategies targeting STAT3 for managing cardiac remodeling.

Main Methods:

• Utilized transgenic mouse models with modified STAT3 signaling and β_IV-spectrin interactions.
• Evaluated cardiac structure and function at baseline and after induced stress (transaortic constriction, aortocaval fistula).
• Performed unbiased gene expression screening and in vitro/in vivo assays to identify pathways regulating myocyte length/width and test therapeutic interventions.

Main Results:

• Loss of β_IV-spectrin or STAT3 activation led to eccentric hypertrophy (increased myocyte length, chamber dilation, decreased function).
• Preservation of β_IV-spectrin promoted concentric hypertrophy (increased myocyte width, preserved function) in response to stress.
• Identified KIF20A and microtubule alterations in different hypertrophy types; β_IV-spectrin/STAT3 signaling impacts KIF20A, microtubules, and sarcomeric gene distribution.
• Pharmacological STAT3 inhibition reversed eccentric to concentric growth and improved systolic function after chronic stress.

Conclusions:

• β_IV-spectrin and STAT3 signaling are critical for directing myocyte geometry by modifying microtubule properties and sarcomeric transcript distribution during cardiac remodeling.
• Cardiac hypertrophy growth and orientation are distinct pathways that can be therapeutically modulated.
• Targeting β_IV-spectrin/STAT3 signaling offers a potential therapeutic avenue for improving cardiac function in hypertrophic conditions.