The development of certain vascular diseases involves the division and migration of blood vessel cells. These seem to arise from stem cells in the vessel wall, not from smooth muscle cells as previously thought.
Song Li at the University of California, Berkeley, and his team isolated the stem cells from rat, mouse and human arteries and showed that the cells can specialize into other cell types including smooth muscle and fat cells. To identify the origin of the dividing vascular cells, the authors fluorescently tagged smooth muscle cells in mice; they found, however, that the dividing vascular cells did not fluoresce but instead expressed stem-cell markers. Vascular cells isolated from an injured mouse carotid artery consisted mainly of these stem cells, suggesting that it is stem cells that divide upon injury, not smooth muscle cells.
Nature Commun. http://dx.doi.org/10.1038/ncomms1867 (2012)