This project will investigate if a deficiency DNA Polymerase Beta (PolB), an enzyme involved in Base Excision Repair (BER), will accelerate age-related remodeling in the heart and the vascular system. The mechanical properties of the vascular system are controlled by its microarchitecture. The largest artery is the aorta, which is composed of four main components: collagen fibrils, elastic fibers, vascular smooth muscle (VSMC) and endothelial cells and these are organized into three layers known as the tunica intima, tunica media and tunica adventitia. In the aorta, there is progressive stiffening with advancing age, but the molecular mechanism responsible for this phenomenon is not well understood. An age comparison between WT and PolB HT mice will be undertaken to interrogate the cardiovasculature in this mouse model and determine if there are any major anatomical differences between the WT (C57BL/6 background) and the PolB HT strains. The aortas of young (4-6 m old) and old (18-20 m old) male mice, 7-10 mice per group, will be stained with: Hematoxylin and eosin (H&E); elastic Van Gieson (EVG), Masson's trichrome, silver and Sirius red stains. The intima-media thickness increases while the elastic fraction of the aorta typically declines with age. All of these variables will be investigated between WT and PolB HT young and old mice. We will also calculate smooth muscle nuclei density within the intima-media area. This also typically declines with age. Vascular smooth muscle cells (VSMCs) will be cultured in vitro and we will quantify markers of senescence, stress responses and extracellular matrix marker changes. We have repeatedly isolated vascular smooth muscle cells (VSMCs) from both young and old WT and PolB HT mice and consistently find that PolB HT have about half as many viable cells. We are analyzing the phenotype of the VSMCs for proliferation, senescence, apoptosis, and extracellular matrix metalloproteases, and will also explore the relevant signaling pathways. It is expected that there will be higher levels of damaged and dying cells in the PolB HT mice.
