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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Research Article Hematology

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 5

Lung-resident Mks respond to infection-associated thrombocytopenia.

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Lung-resident Mks respond to infection-associated thrombocytopenia. (A) ...
(A) Lung-resident, Mk-derived platelet counts were increased with PYnL infection–associated thrombocytopenia. Mice infected with PYnL had reduced platelet counts (n = 5–15 per group from 2 independent experiments) and (B) increased percentages of lung-derived CFSE+ platelets (n = 4–5 per group; results are representative of 2 independent experiments) in the first 2 weeks after infection. (C) Following PYnL infection, the number of BM Mks declined over the first 2 weeks, but the number of lung Mks increased (n = 4–5 per group per time point; results are representative of 2 independent experiments). The proportion of platelets that were CFSE+ was reduced early after infection, indicating an influx of new Mks from an extrapulmonary source. After infection recovery, the relative percentage of CFSE+ Mks in the lung were similar to that of control mice at the same time after CFSE. (D) Lung-resident Mks make platelets upon increased demand. Mice were treated with CFSE o.p. and infected 3 weeks later with PYnL. CFSE+ platelets were increased 1 week after infection (4 weeks after CFSE) (n = 5 per group; results are representative of 2 independent experiments). Data indicate the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001; (A) platelets and (B) CFSE percentage of platelets and (C) CFSE+ Mks: multiple t tests with Holm-Šidák multiple-comparison correction; (C) total Mks: 2-way ANOVA with Holm-Šidák multiple-comparison correction; (D) CFSE percentage and normalized CFSE: unpaired, 2-tailed t test.