The Science of Sustainability

Newly Discovered Stem Cells Cause Clogged Arteries

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UCB researchers exam vascular stem cells in the microscope

Zhenyu Tang (seated at microscope) examines vascular stem cells in culture along with Aijun Wang (left) and Song Li (right). (Zoey Huang photo.)

Odds are that you know someone who’s had a heart attack. One American suffers a coronary event every 25 seconds and about every minute someone dies from one.

Doctors thought they understood artery-hardening diseases, such as atherosclerosis, that lead to heart attacks, strokes and death. But these generally accepted theories are contradicted by new research performed at the University of California, Berkeley. According to a new study published in Nature Communications, a previously unknown type of stem cell is actually the underlying cause for clogged arteries.

For decades, scientists believed that heart disease was caused by the smooth muscle cells that line artery walls. It was thought that bad (LDL) cholesterol damaged the arteries and triggered smooth muscle cells to rapidly reproduce. This led to a build up of fibrous scar tissue that narrowed and hardened the arteries, restricting blood flow. As a result, most therapies focus on physically widening the inside of the blood vessels or replacing the damaged area with a graft.

These beliefs are challenged by new research performed by principle investigator Song Li, a professor of bioengineering and researcher at the Berkeley Stem Cell Center, and his colleagues.

“For the first time, we are showing evidence that vascular diseases are actually a kind of stem cell disease,” said Song Li in a university news release. “This work should revolutionize therapies for vascular diseases because we now know that stem cells rather than smooth muscle cells are the correct therapeutic target.”

Analyzing cells from arteries and veins of transgenic mice, the researchers were able to trace the lineage of the cells that rapidly reproduced in the vessel walls to prove that they were not smooth muscle cells as current theory predicted. Further experiments discovered that they are actually multipotent vascular stem cells, meaning that they can become various specialized cells – smooth muscle, nerve, cartilage, bone and fat cells. The same type of stem cells were also identified in human blood vessels.

This explains why previous studies mistook the multipotent vascular stem cells as smooth muscle cells. It also explains how a soft artery can calcify and harden, since the multipotent stem cells can also form bone and cartilage.

Within walls of blood vessels are smooth muscle cells and newly discovered vascular stem cells. The stem cells are able to differentiate into smooth muscle cells, fat, cartilage and bone cells. UC Berkeley researchers provide evidence that these stem cells are contributing to clogged and hardened arteries.

Within the walls of blood vessels are smooth muscle cells and newly discovered vascular stem cells. The stem cells are able to differentiate into smooth muscle, fat, cartilage and bone cells. UC Berkeley researchers provide evidence that these stem cells are contributing to clogged and hardened arteries. (Song Li illustration)

When new research dramatically challenges existing scientific beliefs, often people resist the new ideas. Dr. Jill Helms, a professor in the Department of Surgery at Stanford School of Medicine and co-author of the study, explained in an NPR interview, “There is resistance oftentimes, but there can be moments where there’s great clarity and I think Song’s work certainly falls within that category.”

However, the research still needs to be repeated by other research groups, as well as verified in other animals and humans. Song Li’s collaboration is already studying human cells from healthy and diseased arteries. They are also developing techniques to rapidly screen drugs that specifically target these stem cells without affecting the normal (endothelial) cells that line a blood vessel, which could ultimately lead to new therapies.

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Category: Biology, Blog, Health

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Jennifer Huber

About the Author ()

Jennifer Huber is a medical imaging scientist at the Lawrence Berkeley National Laboratory with more than 20 years of experience in academic science writing. She received her Ph.D. in Physics from the University of California Santa Barbara. She is also a freelance science writer, editor and blogger, as well as a science-writing instructor for the University of California Berkeley Extension. Jennifer has lived in the San Francisco Bay Area most of her life and she frequently enjoys the eclectic cultural, culinary and outdoor activities available in the area. Read her previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.