A pericyte is a mesenchymal-like cell, associated with the walls of small blood vessels. As a relatively undifferentiated cell, it serves to support these vessels, but it can differentiate into a fibroblast, smooth muscle cell, or macrophage as well if required. In order to migrate into the interstitium, the pericyte has to break the barrier, formed by the basement membrane, which can be accomplished by fusion with the membrane. They are important in blood brain barrier stability as well as angiogenesis. They have been implicated in blood flow regulation at the capillary level. Their expression of smooth muscule actin (SMA) as well as desmin, two proteins found in smooth muscle cells as well as their adherence to the endovascular cells makes them very strong candidates for blood flow regulators in the microvasculature.