Pressure overload induced in newborn rats: effects on left ventricular growth, morphology, and function

Area of Science:

• Cardiovascular Physiology
• Developmental Biology
• Cardiac Remodeling

Background:

• Cardiac hypertrophy is a response to increased workload.
• Understanding the developmental impact of pressure overload is crucial for pediatric cardiology.
• Early-life cardiac stress can influence long-term heart function.

Purpose of the Study:

• To investigate the effects of early-life abdominal aortic constriction on cardiac hypertrophy and function in rats.
• To compare the cardiac remodeling response to pressure overload induced at different early postnatal ages.
• To assess the relationship between hypertrophy, contractile performance, and microvascular/collagen changes.

Main Methods:

• Induction of gradual pressure overload via abdominal aortic constriction in male rats at postnatal day 2 (AC2) or day 6 (AC6).
• Assessment of systemic blood pressure, left ventricular (LV) contractile performance, and right ventricular weight at 8 weeks.
• Histomorphometric analysis of LV myocytes, capillaries, and collagen concentration.

Main Results:

• Aortic constriction induced significant LV hypertrophy, more pronounced in the AC2 group (71%) than AC6 (34%).
• Contractile performance was elevated, but functional reserve remained unchanged in both groups.
• Myocyte density decreased, myocyte size increased, while capillary density and collagen concentration remained constant, adapting proportionally to hypertrophy.

Conclusions:

• Early-life pressure overload leads to proportional cardiac growth and remodeling, with unchanged functional reserve.
• Capillary and collagen adaptations are proportional to ventricular hypertrophy, indicating they are not limiting factors.
• This model is valuable for studying myocardial growth, differentiation, and the transition to decompensated hypertrophy.