Long-lived lung megakaryocytes contribute to platelet recovery in thrombocytopenia models
Alison C. Livada, … , James Palis, Craig N. Morrell
Alison C. Livada, … , James Palis, Craig N. Morrell
Published September 20, 2024
Citation Information: J Clin Invest. 2024;134(22):e181111. https://doi.org/10.1172/JCI181111.
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Long-lived lung megakaryocytes contribute to platelet recovery in thrombocytopenia models

Abstract

Lung megakaryocytes (Mks) are largely extravascular with an immune phenotype (1). Because bone marrow (BM) Mks are short lived, it has been assumed that extravascular lung Mks are constantly “seeded” from the BM. To investigate lung Mk origins and how origin affects their functions, we developed methods to specifically label lung Mks using CFSE dye and biotin delivered via the oropharyngeal route. Labeled lung Mks were present for up to 4 months, while BM Mks had a lifespan of less than 1 week. In a parabiosis model, lung Mks were partially replaced over 1 month from a circulating source. Unlike tissue-resident macrophages, using MDS1-Cre-ERT2 TdTomato mice, we found that lung Mks arose from hematopoietic stem cells. However, studies with FlkSwitch mTmG mice showed that lung Mks were derived from a Flt3-independent lineage that did not go through a multipotent progenitor. CFSE labeling to track lung Mk–derived platelets showed that approximately 10% of circulating platelets were derived from lung-resident Mks at steady state, but in sterile thrombocytopenia this was doubled (~20%). Lung-derived platelets were similarly increased in a malaria infection model (Plasmodium yoelii) typified by thrombocytopenia. These studies indicate that lung Mks arise from a Flt3– BM source, are long-lived, and contribute more platelets during thrombocytopenia.

Authors

Alison C. Livada, Kathleen E. McGrath, Michael W. Malloy, Chen Li, Sara K. Ture, Paul D. Kingsley, Anne D. Koniski, Leah A. Vit, Katherine E. Nolan, Deanne Mickelsen, Grace E. Monette, Preeti Maurya, James Palis, Craig N. Morrell

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Figure 2

Lung Mks are derived from BM HSCs.

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Lung Mks are derived from BM HSCs. (A) mTmG and Bl6/J mice were given CF...
(A) mTmG and Bl6/J mice were given CFSE o.p., and parabiosis surgeries performed 1 week later. Lung Mks were partially replaced by a BM source (n = 8–10 from 2 independent experiments). (B) Mice were given CFSE o.p. and biotin i.p., and 6 hours (n = 2 from 1 experiment), 7 days (n = 3 from 1 experiment), and 28 days (n = 5 from 1 experiment) later, BM and lung Mks were assessed. BM Mks were replaced within 7 days, but lung-resident Mks were detected at each time point. (C) MDS1-TdTomatoCre-ERT2 mice were treated with tamoxifen (TAM) to label HSCs and HSC-derived cells (n = 4–5; results are representative of 2 independent experiments). Lung Mks were HSC derived. (D) BM, splenic, and lung Mks in FlkSwitch mice were assessed at multiple ages (n = 5 per age time point; results are representative of 2 independent experiments) to determine whether Mk differentiation was Flt3 dependent. Lung Mks were largely Tomato+Flt3–, indicating an HSC-to-Mk differentiation that was distinct from BM and splenic Flt3-dependent differentiation. Data indicate the mean ± SEM. *P < 0.05, ***P < 0.001, and ****P < 0.0001, by (B) 1-way ANOVA with Šidák multiple-comparison correction and (C and D) 2-way ANOVA with Tukey’s multiple-comparison correction and (A) 1-way ANOVA with Šidák multiple comparisons correction.