Pericytes and their role in microvasculature homeostasis.

Background: The microvascular pericyte was first described in 1873, though it is a cell that has largely been ignored in the clinical literature. Pericytes are multifunctional, polymorphic, perivascular cells that lie within, and contribute to the production of the microvessel basil lamina.

Materials: The pericyte is the second cell that comprises the capillary wall, and is in a prime location to be involved with microvascular permeability. The exact sequence of events in Acute Respiratory Distress Syndrome (ARDS) is unknown, though increased permeability (pulmonary edema) is the primary physiological abnormality seen in the early stages. Pericytes are crucial in the development of capillary leak and pulmonary edema seen in ARDS. Pericytes regulate permeability through contractility and apoptosis.

Results: Changes in pericyte contractility alter the physical capillary barrier by opening the endothelial junctional space, and are reversible. Pericyte apoptosis leads to a compromise of the barrier effect of the capillary wall, and is a more permanent change.

Conclusions: The purpose of this paper is to review publications of pericyte physiological and pathophysiologic interactions in regards to contractility, apoptosis, and permeability.