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Oxygen tension influences the differentiation, maturation and apoptosis of human megakaryocytes
S S Mostafa1, W M Miller, E T Papoutsakis
1Department of Chemical Engineering, Northwestern University, Evanston, IL 60208-3120, USA.
Abstract:
Megakaryocytes (Mks) mature adjacent to bone marrow (BM) sinus walls and subsequently release platelets within the sinusoidal space or in lung capillaries. As the sites for platelet release have higher levels of oxygen tension (pO(2)) than the core of the BM where stem and progenitor cells reside, we investigated whether pO(2) influences Mk maturation. Mks were generated from CD34(+) cells (from mobilized peripheral blood from cancer patients) under 5% and 20% O(2). At day 15, CD41(+) Mk expansion in 20% and 5% O(2) cultures was 85-fold and 31-fold respectively. Twenty percent O(2) cultures also had higher levels of high ploidy (> or = 8N, eightfold higher) and proplatelet-forming (fivefold higher) Mks. At day 21, 20% O(2) cultures had a fivefold higher number of apoptotic Mks. In contrast, 5% O(2) promoted Mk colony-forming unit (CFU-Mk) generation and maintenance. Similar results were observed in cultures initiated with CD41(+) Mks, indicating that pO(2) directly affects Mks. The change from 20% to 5% O(2) on day 5 and day 7 delayed both maturation and apoptosis, suggesting that these two processes are closely linked. These results were confirmed in CD34(+) cultures from normal BM samples. These data may provide insights into in vivo Mk maturation, such as an explanation for hypoxia-induced thrombocytopenia in animals.
Insights
Oxygen levels (pO2) significantly impact megakaryocyte (Mk) maturation and platelet production. Higher oxygen promotes Mk expansion and ploidy, while lower oxygen supports colony formation, influencing thrombopoiesis.
Area of Science:
- Hematology
- Cell Biology
- Physiology
Background:
- Megakaryocytes (Mks) mature near bone marrow sinus walls, releasing platelets into circulation.
- Oxygen tension (pO2) varies within the bone marrow, with higher levels near sinusoids where Mks mature.
Purpose of the Study:
- To investigate the influence of varying oxygen tension (pO2) on megakaryocyte (Mk) maturation and platelet production.
- To determine if pO2 directly affects Mk development and function.
Main Methods:
- Culturing CD34+ cells and CD41+ Mks from peripheral blood and bone marrow samples under 5% and 20% O2.
- Assessing Mk expansion, ploidy, proplatelet formation, and apoptosis at different time points (day 15 and 21).
- Evaluating Mk colony-forming unit (CFU-Mk) generation and maintenance.
Main Results:
- Higher oxygen (20% O2) significantly increased Mk expansion (85-fold vs. 31-fold), high ploidy, and proplatelet formation compared to lower oxygen (5% O2).
- 20% O2 cultures showed increased Mk apoptosis at day 21, while 5% O2 promoted CFU-Mk generation and maintenance.
- Altering oxygen levels during culture delayed both Mk maturation and apoptosis, indicating a close link between these processes.
Conclusions:
- Oxygen tension directly influences megakaryocyte maturation, ploidy, and platelet release.
- Physiological oxygen levels in the bone marrow microenvironment are critical for regulating thrombopoiesis.
- These findings may explain hypoxia-induced thrombocytopenia and offer insights into in vivo Mk development.