Fibrocytes in health and disease

Fibrocytes are circulating mesenchymal progenitor cells that participate in tissue responses to injury and invasion. Accumulating knowledge from animal models regarding the differentiation, trafficking, and function of these cells implicates them in the development of diseases characterized by chronic inflammation and excessive collagen deposition. Recent data obtained from the clinical setting suggests that the enumeration of circulating fibrocytes may be a biomarker for disease progression in chronic lung diseases including asthma and pulmonary fibrosis. A greater understanding of the immunologic mediators that influence fibrocyte biology suggests new opportunities for therapeutic manipulation of these cells in fibrogenesis. This review integrates new developments in the cellular and molecular biology of fibrocytes with current concepts regarding the etiopathogenesis of fibrosing disorders.