Myocyte DNA synthesis with aging: correlation with ventricular loading in rats

Area of Science:

• Cardiovascular Biology
• Cardiac Aging
• Molecular Cardiology

Background:

• Aging leads to detrimental mechanical and anatomical changes in both ventricles.
• These age-related cardiac changes are associated with impaired heart function.

Purpose of the Study:

• To investigate the association between age-related cardiac mechanical changes and DNA synthesis activation in cardiac myocytes.
• To explore the relationship between hemodynamic performance, loading conditions, and myocyte cell cycle progression during aging.

Main Methods:

• Flow cytometric analysis of myocyte nuclei from rat left and right ventricles at various ages (4, 12, 20, 29 months).
• Assessment of heart weight, ventricular function (left ventricular failure, right ventricular dysfunction), diastolic wall stress, and systolic wall stress.
• Linear regression analysis to correlate cell cycle markers with hemodynamic parameters.

Main Results:

• Significant increase in heart weight with age, correlating with left ventricular failure and right ventricular dysfunction.
• Elevated diastolic wall stress and increased percentage of myocyte nuclei in S+G2M phase in both ventricles.
• Direct correlation between cell cycle entry and diastolic pressure/wall stress; inverse correlation with +dP/dt and systolic wall stress.

Conclusions:

• Age-related cardiac remodeling involves increased DNA synthesis in cardiac myocytes.
• Depressed hemodynamic performance and altered loading conditions contribute to enhanced DNA synthesis in aging cardiac myocytes.
• These findings suggest a link between cardiac aging, mechanical stress, and cellular responses involving DNA replication.