Study: Surprising Cause for Hardening of the Arteries

My mother’s death certificate read: “Heart arrest due to atherosclerotic disease.” Arteriosclerosis or atherosclerosis, commonly called “hardening of the arteries”, causes blood vessels to become stiff, narrow, and blocked and leads to heart disease and stroke The narrowing and loss of elasticity of the arteries is caused by both lipid (fat) build-up and multiplication and growth of cells inside the arteries. Previously, scientists suspected, but had no real evidence, that smooth muscle cells, lining the arteries, were responsible for hardening of the arteries. A study by researchers from the University of California, Berkeley, showed for the first time that stem cells, embedded in the arteries, cause calcification and hardening of the arteries.

Hardening of the arteries: arteriosclerosis or atherosclerosis

Arteriosclerosis and atherosclerosis are of often used interchangeable, but according to Stedman’s Medical Dictionary, atherosclerosis is a specific type of arteriosclerosis. Atherosclerosis is associated with irregular deposits of lipids or fats inside the arteries.

Who is at risk for hardening of the arteries?

Hardening and narrowing of the arteries is a slow progressive process. Although heart disease and strokes don’t set in until a later age (My mother started having heart problems at age 70.), hardening and plaque build-up, made up of fats and cells, start already during the teenage years, according to a study, published in the Journal of the American Heart Association. By age 35, two out of three people already have some plaque build-up in their arteries. Risk factors for developing hardening of the arteries are a mix of genes and lifestyle-related factors such as weight gain, type 2 diabetes, physical inactivity, smoking, and a high blood lipid profile.

A game-changing study

Because clogged arteries are filled with smooth muscle cells in the areas with plaque, scientists assumed that smooth muscle cell growth contributes to atherosclerosis. But the researchers at the University of California found that while 90 percent of the cells in the arteries were smooth muscle cells, smooth muscle cells are not the cells that multiply and cause hardening of the arteries. It is stem cells, which only make up a tiny fraction of blood vessel cells, which respond to blood vessel injury and multiply. These vascular stem cells, in accordance with their stem cell character, have the ability to turn into all kinds of different cells, including nerve, smooth muscle, cartilage, and bone cells. The ability of the stem cells to become bone cells may explain the calcification and loss of flexibility of arteries in atherosclerosis. Researchers used mice in most of their studies, but also showed that the same kinds of stem cells are present in human carotid arteries. “For the first time, we are showing that vascular diseases are actually a kind of stem cell disease”, said Song Li, professor of bioengineering (University of California, Berkeley, press release).

New therapies

The identification of vascular stem cells as part of the cause of hardening of the arteries may produce new and better therapies. The study also leads to new questions. What triggers activate these stem cells to harden arteries? How can inappropriate activation of stem cells be inhibited? Are there other diseases that are caused by stem cells?

Sources

Tang, Z. et a. Differentiation of multipotent vascular stem cells contributes to vascular disease. Nature Communication (2012) doi: 10.1038/ncomms1867

http://jama.jamanetwork.com/article.aspx?articleid=188840

http://newscenter.berkeley.edu/2012/06/06/stem-cells-vascular-disease/