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Breathing and Making Blood? – A new Role for the Lungs

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Review of “The lung is a site of platelet biogenesis and a reservoir for haematopoietic progenitors” from Nature by Stuart P. Atkinson

Researchers from the laboratory of Mark R. Looney (UCSF, USA) knew of indirect evidence suggesting that platelet biogenesis by megakaryocytes could occur in the lungs as well as the bone marrow [1-3]. To confirm this hypothesis, the laboratory turned to 2-photon intravital microscopy (2PIVM) of the lungs of engineered reporter mouse strains. However, in confirming platelet production in the lungs, the team also found evidence of a lung-resident hematopoietic progenitor population in what could represent a paradigm shift in our understanding of the hematopoietic system [4].

Employing GFP to mark both megakaryocytes and platelets in mice, single cell imaging data confirmed that megakaryocytes migrated out of the bone marrow space, circulated through the lungs, and contributed to approximately 50% of total platelet production in the mouse. The study identified mature and immature megakaryocyte populations within the extravascular spaces of the lungs, and during this analysis, the authors also discovered the presence of hematopoietic progenitors. Importantly, these progenitors could migrate from the lungs to repopulate the bone marrow where they contribute to the production of platelets and other hematopoietic lineages following bone marrow depletion.

But why does platelet production occur in the lungs? The authors suggest that mechanical forces could enhance platelet maturation and provide signals that promote platelet release and the delineation of these mechanisms may contribute to the treatment of conditions such as low platelet counts (thrombocytopenia). Furthermore, activating the unexpected lung-resident hematopoietic progenitors could also represent an important means to battle other hematopoietic diseases and disorders.

Breathing and making blood - will we ever look at the lungs in the same way again? Keep tuned to the Stem Cells Portal to find out!

References

  1. Howell WH and Donahue DD. The Production of Blood Platelets in the Lungs. J Exp Med 1937;65:177-203.
  2. Aschoff L. Ueber capilläre Embolie von riesenkernhaltigen Zellen. Archiv für pathologische Anatomie und Physiologie und für klinische Medicin 1893;134:11-25.
  3. Kallinikos-Maniatis A. Megakaryocytes and platelets in central venous and arterial blood. Acta Haematol 1969;42:330-335.
  4. Lefrançais E, Ortiz-Muñoz G, Caudrillier A, et al. The lung is a site of platelet biogenesis and a reservoir for haematopoietic progenitors. Nature 2017;544:105-109.