Blood pressure-independent cardiac hypertrophy induced by locally activated renin-angiotensin system

Area of Science:

• Cardiovascular Biology
• Molecular Endocrinology
• Renal Physiology

Background:

• Cardiac hypertrophy is a common complication of chronic hypertension.
• The renin-angiotensin system (RAS) effector, angiotensin II (Ang II), regulates blood pressure and hypertension.
• Ang II is increasingly recognized for its role as a growth factor in the heart.

Purpose of the Study:

• To investigate whether local Ang II production can induce cardiac hypertrophy independently of elevated blood pressure.
• To elucidate the role of the cardiac RAS in mediating hypertrophic responses in vivo.

Main Methods:

• Generation of transgenic mice with cardiac-specific overexpression of the rat angiotensinogen gene.
• Assessment of cardiac morphology, including hypertrophy and fibrosis.
• Monitoring of blood pressure to differentiate effects of Ang II from hypertension.

Main Results:

• Transgenic mice developed significant myocardial hypertrophy.
• Cardiac hypertrophy occurred without evidence of cardiac fibrosis.
• The observed hypertrophy was independent of elevated blood pressure, indicating a direct trophic effect of local Ang II.

Conclusions:

• Local production of Ang II in the heart is sufficient to induce cardiac hypertrophy.
• Ang II acts as a direct growth factor in the myocardium, irrespective of systemic blood pressure.
• Targeting local cardiac RAS may offer new therapeutic strategies for cardiac hypertrophy in non-hypertensive conditions.