The Laboratory of Cardiovascular Science has a strong commitment to identifying and studying the process of aging in the myocardium. To identify gene products in heart potentially involved in aging, cDNA microarrays have been analyzed with mRNA from left ventricles of Fisher 344 rats, CBA mice treated with biopeptides thought to be important 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. 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 have been studied in CBA mice, in collaboration with the Russian Academy of Medical Science, in St. Petersburg. Comparative analysis of cDNA gene expression arrays hybridized with heart RNA samples from control and experimental mice (vilon and epitalon) revealed 300 clones (1,97% of the total number of clones) with >2-fold change in expression for Vilon and Epitalon groups. Of these, expression of 36 transcripts was uniquely altered by Vilon and 105 by Epitalon. Vilon and Epitalon led to conserved and significant changes in expression in 159 transcripts. The analysis identified multiple genes involved at cell division (14 for Vilon or Epitalon), cell signaling/communication (15 and 14, respectively), cell structure/motility (7 and 6), cell/organism defense (16 and 13), gene/protein expression (24 and 17), metabolism (19 and 11), and genes encoded by mitochondrial DNA (5 and 5). 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. Similar studies have been performed with melatonin. These gene products that can explain the molecular basis for the geroprotective effects of these peptides. We are currently completing the analysis of an aging Fisher 344 aging rat model. Only 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 also employed cDNA 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. The data from each of these projects are being compared in an effort to identify candidate genes implicated not only in aging, but also in disease.
