Environmental oxygen affects ex vivo growth and proliferation of mesenchymal progenitors by modulating mitogen-activated protein kinase and mammalian target of rapamycin signaling.

Background Aims: Stem and progenitor cells of hematopoietic and mesenchymal lineages reside in the bone marrow under low oxygen (O ₂ ) saturation. O ₂ levels used in ex vivo expansion of multipotent mesenchymal stromal cells (MSCs) affect proliferation, metabolism and differentiation.
Methods: Using cell-based assays and transcriptome and proteome data, the authors compared MSC cultures simultaneously grown under a conventional 19.95% O ₂ atmosphere or at 5% O ₂ .
Results: In 5% O ₂ , MSCs showed better proliferation and higher self-renewal ability, most probably sustained by enhanced signaling activity of mitogen-activated protein kinase and mammalian target of rapamycin pathways. Non-oxidative glycolysis-based energy metabolism supported growth and proliferation in 5% O ₂ cultures, whereas MSCs grown under 19.95% O ₂ also utilized oxidative phosphorylation. Cytoprotection mechanisms used by cells under 5% O ₂  differed from 19.95% O ₂   suggesting differences in the triggers of cell stress between these two O ₂   conditions.
Conclusions: Based on the potential benefits for the growth and metabolism of MSCs, the authors propose the use of 5% O ₂ for MSC culture.
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