Western array analysis of cell cycle protein changes during the hyperplastic to hypertrophic transition in heart development.

Cardiac myocytes proliferate most rapidly during the hyperplastic phase of heart development; however, the level of cell cycle activity is drastically down regulated after birth. Further growth of the heart is achieved by hypertrophic growth of cardiac myocytes. The mechanism that controls the switch from hyperplastic proliferation to hypertrophic growth in cardiac myocytes is unknown. Understanding this fundamental mechanism of cardiac myocyte biology would be most beneficial for studies directed towards myocardial regeneration. In this study, we identified changes in the expression of proteins involved in cell cycle regulation during the hyperplastic to hypertrophic transition of cardiac myocytes. Using a high-throughput immunoblotting technique, we examined 200+ proteins in primary cultures of cardiac myocytes at different developmental time points to determine the important regulators of this transition. In addition, we also analyzed samples from an immortalized cardiac myocyte cell line to compare expression levels of cell cycle regulatory proteins to our primary cultures. Our findings by this uncovered proteomic screen identified several potential key regulatory proteins and provide insight into the important components of cardiac myocyte cell cycle regulation.