Role of Notch Signaling in the Maintenance of Human Mesenchymal Stem Cells Under Hypoxic Conditions

Abstract

Human adipose tissue-derived multilineage progenitor cells (hADMPCs) are attractive for cell therapy and tissue engineering because of their multipotency and ease of isolation without serial ethical issues. However, their limited in vitro lifespan in culture systems hinders their therapeutic application. Some somatic stem cells, including hADMPCs, are known to be localized in hypoxic regions; thus, hypoxia may be beneficial for ex vivo culture of these stem cells. These cells exhibit a high level of glycolytic metabolism in the presence of high oxygen levels and further increase their glycolysis rate under hypoxia. However, the physiological role of glycolytic activation and its regulatory mechanisms are still incompletely understood. Here, we show that Notch signaling is required for glycolysis regulation under hypoxic conditions. Our results demonstrate that 5% O 2 dramatically increased the glycolysis rate, improved the proliferation efficiency, prevented senescence, and maintained the multipotency of hADMPCs. Intriguingly, these effects were not mediated by hypoxia-inducible factor (HIF), but rather by the Notch signaling pathway. Five percent O 2 significantly increased the level of activated Notch1 and expression of its downstream gene, HES1. Furthermore, 5% O 2 markedly increased glucose consumption and lactate production of hADMPCs, which decreased back to normoxic levels on treatment with a g-secretase inhibitor. We also found that HES1 was involved in induction of GLUT3, TPI, and PGK1 in addition to reduction of TIGAR and SCO2 expression. These results clearly suggest that Notch signaling regulates glycolysis under hypoxic conditions and, thus, likely affects the cell lifespan via glycolysis.

Hypoxia Inhibits De Novo Vascular Assembly of Adipose-Derived Stromal/Stem Cell Populations, but Promotes Growth of Preformed Vessels

“…The cells may have compensated for reduced oxygen availability by shifting their metabolism more toward anaerobic glycolysis as glucose consumption and lactate production were both significantly higher in hypoxia. Similar hypoxic resiliency and metabolic shifts have been demonstrated in ASCs 26 and other cell types. 27,28 This finding is promising regarding the ability of ASCs to endure harsh ischemic environments after transplantation.…”

MicroRNA and mRNA cargo of extracellular vesicles from porcine adipose tissue-derived mesenchymal stem cells

“…HES1 is a critical downstream effector of the Notch signaling pathway, and its activation regulates vascular remodeling and arterial fate of endothelial cells 38 . Importantly, activation of the Notch signaling pathway also increases human MSC survival 39 . Similarly, TCF4 is a key downstream effector of Wnt signaling, a canonical pathway that plays a central role in vascular development 40 and in determining and maintaining the phenotype and functional properties of human stem cells 41 .…”

Low Oxygen Modulates Multiple Signaling Pathways, Increasing Self-Renewal, While Decreasing Differentiation, Senescence, and Apoptosis in Stromal MIAMI Cells

“…Physiologic oxygen tension ranges from £1% in cartilage and regions of the bone marrow to 10%-13% in the main arteries of most tissues [6]. Increasing evidence suggests that oxygen tension is a key regulator of cell growth, proliferation, senescence, and differentiation of stem and progenitor cells [4,[7][8][9][10][11][12][13]. We reported that low oxygen enhances MIAMI cell pluripotency, proliferation, and maintenance of osteoblastic differentiation capability [4].…”

“…Stem cell self-renewal involves several pathways, including Notch, Wnt, repressor element (RE)-1-silencing transcription factor (REST), Sirtuin, and the PI3K/Akt/mTOR pathway [13][14][15][16][17][18]. The highly conserved Notch pathway can regulate stem cell self-renewal [13,19].…”

“…The highly conserved Notch pathway can regulate stem cell self-renewal [13,19]. Notch releases an intracellular fragment (notch intracellular domain, NICD) [20] that migrates to the nucleus where it regulates expression of target genes.…”