Vascular smooth muscle and arterial calcification

Smooth muscle cultures can calcify under certain circumstances. As a model system these cultures therefore provide information on why calcification oc curs in atherosclerotic plaques. Whether all smooth muscle cells (under cer tain conditions), or only specific populations, can produce this mineraliza tion has not been resolved. Demer's group has cloned calcifying vascular ce lls from subcultured bovine aorta and studied them in detail. They have spe culated on whether the cells are smooth muscle which have altered in phenot ype, or whether they are derived from a stem cell population within the art ery wall. The article argues that while the normal process of smooth muscle phenotypi c modulation seen in arterial repair could account for the observations, th is view may be two simplistic considering the complex nature of the artery wall. Certainly there is evidence for heterogeneity of smooth muscle cells in the artery wall and recent evidence suggests that stem cells can circula te in the blood and repopulate tissues. Further studies are required to res olve the important question as to the origin of cells which produce mineral ization in atheroma.