Objectives: The lung was recently re-discovered as a hematopoietic organ for platelet production in mice. However, evidence for the role of the lung in thrombopoiesis in humans is still limited. In this study, we examined megakaryocytes in the pulmonary and systemic circulation, specifically in pulmonary arterial blood (PAB), venous blood (PVB) and peripheral blood using a newly developed microfluidic platform for rare cell isolation.
Materials and methods: We analyzed 23 lung cancer patients who underwent surgery in our institute. PAB and PVB were obtained from the resected lung immediately after surgery. Blood samples were size-selected using a filtration-based microfluidic device and enriched rare cells on glass slide specimens were stained with Papanicolaou (Pap), immunocytochemistry (ICC), and immunofluorescence (IF). Lung tissues were also analyzed by immunohistochemistry.
Results: Pap/ICC/IF showed the presence of abundant CD61+/cytokeratin- giant cells with a megakaryocyte lineage in PAB, but only a few in PVB. These megakaryocytes were found to consist of CD61+/CD41+ immature megakaryocytes and CD61+/CD41- mature megakaryocytes with the potential to produce platelets. These findings were confirmed by the conventional hematological analysis of blood smears stained with Giemsa. In analysis of lung cancer, CD61+ megakaryocytes were observed exclusively in the capillaries of non-cancerous tissue, whereas platelets were selectively observed in the tumor blood vessels of cancerous tissue.
Conclusions: These results indicate that numerous megakaryocytes migrate from systemic bone marrows to accumulate in PAs and arrest of mature megakaryocytes in the capillaries of normal lung, suggesting the possibility that the lung plays a physiological role in the systemic thrombopoiesis in lung cancer patients.
Keywords: Circulating megakaryocytes; Lung cancer patients; Microfluidic device; Pulmonary arterial blood; Thrombopoiesis.
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