When the proportion of alpha myosin heavy chain is reduced in isolated cells, the contraction speed is slower. There's no doubt that some genes change their activity with aging. We just don't know why or how yet. In general, though, the expression of genes in the aging heart tends to revert back to patterns of gene expression seen in the fetus. Atherosclerosis significantly increases the risk of heart disease and stroke.
Blood vessels consist of several kinds of cells.
Lining the inner surface are endothelial cells which are attached to a basement membrane. Moving toward the outer surface, a layer of tissue called the intima comes next, followed by the inner elastic membrane. In the normal process of aging, some vascular smooth muscle cells migrate to the intima, which grows larger. The process seems to be triggered, at least partly, by the build-up of fatty streaks with cholesterol along the artery walls. This much was known by 1992 when Rebecca Pauly, Michael Crow, and others at NIA set out to learn what happened in the vascular smooth muscle cells during atherosclerosis.