What are Pericytes?

A pericyte, also known as a mural cell, a rouget cell or adventitial cell, is a connective tissue cell that is found in blood vessels. Pericytes are adjacent to endothelial cells, the cells that line the entire circulatory system, of blood vessels. They are known to stabilize the walls of blood vessels and to participate in the regulation of blood flow. These cells influence the maturation, migration and survival of endothelial cells and play an important role in angiogenesis, the growth and development of new blood vessels.

Pericytes are relatively undifferentiated cells. They can, however, differentiate into a fibroblast, macrophage or smooth muscle cell as well. Various pericytes from various anatomical locations also differ physiologically, morphologically and biochemically.

Identification of a pericyte is generally done by its anatomical location. Molecular markers, used to identify an organism's deoxyribonucleic acid (DNA) using a DNA probe, are also commonly used to identify them. The expression of markers varies in different anatomical locations.

One of the important roles of a pericyte is maintaining the stability of the blood-brain barrier in the brain. The blood-brain barrier stops toxic substances from leaking out of capillaries and into the surrounding brain tissue. Research shows that reducing the number of mural cells in mice results in impaired learning and memory as well as damage to the neurons — signs generally associated with people as they age. Regulating the flow of blood in the brain is another important role played by these cells.

Another important function of a pericyte is in the maintenance of homeostasis and hemostasis. When pericytes from the pancreas are taken and re-injected into an injured muscle cell, the cells immediately begin to regenerate muscle tissue. These cells are also able to function as multipotent cells giving rise to cells of multiple lineages. This suggests that they might influence tissue repair, wound healing and other developmental processes under various conditions.

Damage to pericytes in the retinal vessels is associated with symptoms of diabetic retinopathy. Another condition, known as hemangiopericytoma, is a type of malignant tumor originating in mural cells inside the walls of capillaries. It is an exceedingly rare tumor. Treatment generally includes radiotherapy, chemotherapy and/or surgery. There are reports of recurrence and metastasis in patients years after treatment.

The role that pericytes have in the development of cancer is unclear. Evidence, however, suggests that aberrations in pericyte-endothelial cell signaling networks could contribute to tumors and metastasis. Researchers have been working to gain a better understanding of the precise role of these cells under normal and pathological conditions.

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