The lungs play an important role in producing blood. Until this discovery, lungs were only associated with breathing, and the bone marrow was thought to be the one responsible for blood production.
New research carried out at the University of California San Francisco has found that most of the platelets are actually produced in the lungs, and not in the bone marrow. The study was conducted on mice and it suggests that the lungs have a reservoir of blood stem cells that exist for backup, in case the bone marrow runs dry.
The findings have been published in the journal Nature.
Lungs Responsible For Blood Production
Scientists have believed for a long time that the only cells responsible for blood production can be found in the bone marrow, as part of a process called hematopoiesis.
This process supplies the body with the oxygen-carrying red blood cells that it needs in order to function normally, as well as the white blood cells that help the body against infection. Additionally, there are other components of blood production, such as the platelets, which are responsible with the blood clots formed after an injury to stop the bleeding.
Megakaryocytes are the cells responsible for the production of platelets. While they have been found in lung tissue before, it was believed that they mainly live and carry out their platelets-producing process in the bone marrow.
The research spotted the newly found function while they were imaging the lungs of living mice in an attempt to investigate the way platelets circulate through the lungs, interacting with the immune system.
The mice had been modified so that their platelets were glowing and green. This process turned out to highlight a great number of megakaryocytes in the lungs, which was beyond the researchers's expectation.
"When we discovered this massive population of megakaryocytes that appeared to be living in the lung, we realized we had to follow this up," noted Emma Lefrançais, co-first author of the study.
Upon closer inspection, the team found that the megakaryocytes in the lungs were creating more than 10 million platelets an hour, this number accounting for more than a half of the total amount of platelets produced by a mouse. The population of platelets seems to be fed by megakaryocyte progenitor cells, as well as blood stem cells which live immediately outside of the lung vasculature.
As part of the research, the team of scientists used video microscopy techniques to better analyze the population of platelets living in the lung area.
"These results identify the lungs as a primary site of terminal platelet production and an organ with considerable hematopoietic potential," noted the research.
Lungs Help The Bone Marrow In Producing Blood
The lungs seem to be responsible for a massive part of the work associated with blood production, while working with the bone marrow to do so. In an attempt to understand how the stem cells are carried from one place to another, the scientists transplanted lungs from normal animals into mice whose megakaryocytes were fluorescent.
Shortly after the transplant, the "normal" lungs started to show glowing spots, which showed that megakaryocytes are only transported into the lungs, but they are born inside the bone marrow.
