Lung as a Niche for Hematopoietic Progenitors

Abstract

Platelets are released from megakaryocytes. The bone marrow has been proposed to be the major site where this process occurs. Lefrançais et al. (2017) using state-of-the-art techniques including two-photon microscopy, in vivo lineage-tracing technologies, and sophisticated lung transplants reveal that the lung is also a primary site for platelet biogenesis. Strikingly, lung megakaryocytes can completely reconstitute platelet counts in the blood in mice with thrombocytopenia. This study also shows that hematopoietic progenitors, with capacity to repopulate the bone marrow after irradiation, are present in the lungs. This work brings a novel unexpected role for the lung as a niche for hematopoiesis. The emerging knowledge from this research may be important for the treatment of several disorders.

Keywords: Hematopoietic stem cells; Lung; Niche; Origin.

Fig. 1

Lung as a Primary Site for Platelet Production and Hematopoiesis. It is well accepted that bone marrow is an important site for platelet biogenesis and hematopoiesis. Extramedular hematopoiesis can occur in other organs, such as liver and spleen. The study of Lefrançais and colleagues now reveales that megakaryocytes circulate through the lungs and release platelets [115]. Platelet biogenesis in the lung represents 50% of its total production. Lefrançais and colleagues also showed that the lung is a reservoir for hematopoietic progenitors, including HSCs. With the appearance of state of art technologies, future studies will reveal in detail the components of the lung hematopoietic niche