Artery wall stem cells can form tissues, including bone

American Heart Association
Tuesday, 28 October 2003

Artery walls contain a type of stem cell that can form bone, smooth muscle, cartilage, or marrow – a discovery that may lead to new forms of cellular transplant and treatments, researchers report in today's rapid access issue of Circulation: Journal of the American Heart Association.

The study identifies a specific cell in arteries that can potentially develop into one of several cell types. Stem cells are beginning cells that have the potential to become any type of cell. They do this through a process called differentiation.

The findings here may help explain how growths made of bone and certain other biological materials end up in artery-narrowing deposits called plaques, which can lead to heart attacks, strokes, and severe leg pain, said senior author Linda L. Demer, M.D., Ph.D.

"The finding fits a lot of important things. It explains the unusual pathology that we see in plaques, and it opens up the possibility that adult vascular tissue could be used as a source of a certain type of stem cell," said Demer, the Guthman Professor of Medicine and Physiology and Vice Chair of the Department of Medicine at the University of California, Los Angeles.

During the past decade, many heart specialists have accepted the concept – ignored for most of the 20th century – that the calcium in plaques is actually bone material, Demer said.

"Now that we have molecular techniques, we can show that the calcium in plaque is the same as bone," she said. "The reason that arteries harden is that bone is forming in them."

Several years ago, Demer and her co-workers demonstrated that calcifying vascular cells (CVCs) found in artery walls can create bone. But they also noticed aspects that suggested the cells could become other tissue as well.

In this study, the team cultured smooth muscle cells and observed them in the lab. They used cell markers to identify the specific types of cells that differentiated from the artery walls.

"We have now shown clearly that CVCs not only become bone but cartilage, marrow and smooth muscle as well," Demer said.

"The findings indicate that the adult artery wall contains cells with lineage plasticity and self-renewal capacity. These cells, previously termed calcifying vascular cells, are a type of mesenchymal progenitor cell of the artery wall," the authors write.

The cells, however, do not become fat cells – which indicates they could be used to regenerate tissue, including bone.

While this is preliminary research, the potential of the new findings for treating osteoporosis is intriguing, Demer said.

"Older women who are losing bone in their skeletons are still forming fresh new bone in their aorta. That suggests they have the capacity to create bone. It may be possible to harness that process to create a therapy for bone loss," she said.

Co-authors are Yin Tintut, Ph.D.; Zeni Alfonso, Ph.D.; Trishal Saini, B.S.; Kristen Radcliff, A.B.; Karol Watson, M.D., Ph.D.; and Kristina Bostrom, M.D., Ph.D.

The study was funded by the National Institutes of Health.

For more information, or to contact American Heart Association, see their website at: www.americanheart.org