Pericytes in Chronic Lung Disease.

Pericytes are supportive mesenchymal cells located on the abluminal surface of the microvasculature, with key roles in regulating microvascular homeostasis, leukocyte extravasation, and angiogenesis. A subpopulation of pericytes with progenitor cell function has recently been identified, with evidence demonstrating the capacity of tissue-resident pericytes to differentiate into the classic MSC triad, i.e., osteocytes, chondrocytes, and adipocytes. Beyond the regenerative capacity of these cells, studies have shown that pericytes play crucial roles in various pathologies in the lung, both acute (acute respiratory distress syndrome and sepsis-related pulmonary edema) and chronic (pulmonary hypertension, lung tumors, idiopathic pulmonary fibrosis, asthma, and chronic obstructive pulmonary disease). Taken together, this body of evidence suggests that, in the presence of acute and chronic pulmonary inflammation, pericytes are not associated with tissue regeneration and repair, but rather transform into scar-forming myofibroblasts, with devastating outcomes regarding lung structure and function. It is hoped that further studies into the mechanisms of pericyte-to-myofibroblast transition and migration to fibrotic foci will clarify the roles of pericytes in chronic lung disease and open up new avenues in the search for novel treatments for human pulmonary pathologies.