Impact of bone marrow on respiratory disease.

The bone marrow is not only a site of haematopoiesis but also serves as an important reservoir for mature granulocytes and stem cells, including haematopoietic stem cells, mesenchymal stem cells and fibrocytes. In respiratory diseases, such as asthma and idiopathic pulmonary fibrosis these cells are mobilised from the bone marrow in response to blood-borne mediators and subsequently recruited to the lungs. Although the granulocytes contribute to the inflammatory reaction, stem cells may promote tissue repair or remodelling. Understanding the factors and molecular mechanisms that regulate the mobilisation of granulocytes and stem cells from the bone marrow may lead to the identification of novel therapeutic targets for the treatment of a wide range of respiratory disorders.