The Laboratory of Cardiovascular Science has a strong commitment to the study of aging myocardium. To identify gene products in heart potentially involved in aging, functional genomic analyses (cDNA microarrays and Serial Analysis of Gene Expression) have been employed to analyze mRNA from left ventricles of Fisher 344 rats with or without caloric restriction, Wistar rats, C57Bl/6 mice during the perinatal period and with aging, CBA mice treated with biopeptides implicated in gerontoprotection, and human biopsies from failing and non-failing myocardium.
The aim of these projects are to determine which gene products are regulated as a function of age or disease, and then use independent methods to determine the underlying mechanisms responsible for the altered changes in gene expression. In 2002, we published a reference dataset (SAGE analysis) of the mouse myocardium that is publicly available, and we have expanded these studies to examine male versus female mice and young versus old mice. This work is on-going, but will soon be expanded to include a number of transgenic mouse lines with phenotypes of premature aging. To identify early molecular events regulated by biopeptides (synthetic thymic dipeptide Vilon (Lys-Glu) or with pineal tetrapeptide Epitalon (Ala-Glu-Asp-Gly)), gene expression profiles were studied in CBA mice, in collaboration with the Russian Academy of Medical Science, in St. Petersburg. Comparative analysis demonstrated both general and unique features of Vilon and Epitalon effects on cardiac gene expression. About 22% of transcripts demonstrated altered gene expression for both experimental groups, and this work is being followed up by our collaborators. Similar studies have also been performed with melatonin. We have completed a large-scale transcriptome analysis of an aging Fisher 344 aging rat model and have added a caloric restriction model for comparisons. In ad libitum Fisher 344 rats, 4.3% of the transcripts showed age-dependent alterations, most of which occurred late in life (64%, 249/388 occurred at 30 months). We are completing an extensive quantitative-PCR analysis to validate these data, and by independent techniques, to determine the significance of the changes in gene expression with the aging process. We have expanded our aging studies in rodent to include in vitro analyses of cultured cardiomyoyctes and fibroblasts to delineate mechanisms underlying the aging response of cardiac genes. Finally, we have employed functional genomic techniques (microarrays) to examine the transcriptomes of LVs from failing (n=8) and non-failing human myocardium (n=7). Following identification of a pool of HF-responsive candidate genes by microarrays and statistical methods, we employed Q-PCR on a larger sample population (n=34) to validate and examine the role of contributing biological variables (age and gender). We find that most of the HF-candidate genes (including transcription factors, modifying enzymes, ECM proteins and metabolic enzymes) demonstrated significant changes in gene expression; however, the majority of the putative changes depended on variables such as sex and age, and not on HF alone. Additionally, some putative HF-responsive gene products demonstrated highly significant changes in expression as a function of age and/or sex, but independent of HF. These studies with human samples have now expanded to include hypertension, and we have begun a meta analysis of human heart failure data. The data from each of these projects are being compared in an effort to identify and analyze the function of candidate genes in aging and disease.
