UC SANFRANCISCO Scientist has published a study conducted on MICE  in journal  "NATURE " that Lung has a complete new role in formation of Platelets from Stem cells .The  the researchers found that the lungs produced more than half of the platelets blood components required for the clotting that stanches bleeding in the mouse circulation. In another surprise finding, the scientists also identified a previously unknown pool of blood stem cells capable of restoring blood production when the stem cells of the bone marrow, previously thought to be the principal site of blood production, are depleted. "This finding definitely suggests a more sophisticated view of the lungs that they're not just for respiration but also a key partner in formation of crucial aspects of the blood," said pulmonologist Mark R. Looney, MD, a professor of medicine and of laboratory medicine at UCSF and the new paper's senior author. "What we've observed here in mice strongly suggests the lung may play a key role in blood formation in humans as well." The findings could have major implications for understanding human diseases in which patients suffer from low platelet counts, or thrombocytopenia, which afflicts millions of people and increases the risk of dangerous uncontrolled bleeding. The findings also raise questions about how blood stem cells residing in the lungs may affect the recipients of lung transplants. More detailed imaging sessions soon revealed megakaryocytes in the act of producing more than 10 million platelets per hour within the lung vasculature, suggesting that more than half of a mouse's total platelet production occurs in the lung, not the bone marrow, as researchers had long presumed. Video microscopy experiments also revealed a wide variety of previously overlooked megakaryocyte progenitor cells and blood stem cells sitting quietly outside the lung vasculature estimated at 1 million per mouse lung. "It's fascinating that megakaryocytes travel all the way from the bone marrow to the lungs to produce platelets," said Guadalupe Ortiz-Muñoz, PhD, also a postdoctoral researcher in the Looney lab and the paper's other co-first author. "It's possible that the lung is an ideal bioreactor for platelet production because of the mechanical force of the blood, or perhaps because of some molecular signaling we don't yet know about."