ex-vivo-expansion-hematopoietic-stem-cells-from-human-umbilical-cord

Ex Vivo Expansion of Hematopoietic Stem Cells from Human Umbilical Cord Blood-derived CD34<sup>+</sup> Cells Using Valproic Acid

Umbilical cord blood (UCB) units provide an alternative source of human hematopoietic stem cells (HSCs) for patients who require allogeneic bone marrow ...

Icahn School of Medicine at Mount Sinai

The limited number of hematopoietic stem cells (HSCs) in umbilical cord blood (UCB) units restricts their use for stem cell transplantation. Ex vivo treatment of UCB-CD34 cells with valproic acid (VPA) increases the number of transplantable HSCs. In this study, we demonstrate that HSC expansion is not merely a result of proliferation of the existing stem cells but, rather, a result of a rapid reprogramming of CD34CD90 cells into CD34CD90 cells, which is accompanied by limited numbers of cell divisions. Beyond this phenotypic switch, the treated cells acquire and retain a transcriptomic and mitochondrial profile, reminiscent of primary HSCs. Single and bulk RNA-seq revealed a signature highly enriched for transcripts characteristic of primary HSCs. The acquisition of this HSC signature is linked to mitochondrial remodeling accompanied by a reduced activity and enhanced glycolytic potential. These events act in concert with a modest upregulation of p53 activity to limit the levels of reactive oxygen species (ROS). Inhibition of either glycolysis or p53 activity impairs HSC expansion. This study indicates that a complex interplay of events is required for effective ex vivo expansion of UCB-HSCs.

Ex vivo human HSC expansion requires coordination of cellular reprogramming with mitochondrial remodeling and p53 activation.

Quiescent and self-renewing hematopoietic stem cells (HSCs) rely on glycolysis rather than on mitochondrial oxidative phosphorylation (OxPHOS) for energy production. HSC reliance on glycolysis is considered an adaptation to the hypoxic environment of the bone marrow (BM) and reflects the low energetic demands of HSCs. Metabolic rewiring from glycolysis to mitochondrial-based energy generation accompanies HSC differentiation and lineage commitment. Recent evidence, however, highlights that alterations in mitochondrial metabolism and activity are not simply passive consequences but active drivers of HSC fate decisions. Modulation of mitochondrial activity and metabolism is therefore critical for maintaining the self-renewal potential of primitive HSCs and might be beneficial for ex vivo expansion of transplantable HSCs. In this review, we emphasize recent advances in the emerging role of mitochondria in hematopoiesis, cellular reprograming, and HSC fate decisions.

Article	Year
Ex vivo human HSC expansion requires coordination of cellular reprogramming with mitochondrial remodeling and p53 activation. Blood advances\| PubMed ID: 30348672	2018
Mitochondrial Role in Stemness and Differentiation of Hematopoietic Stem Cells. Stem cells international\| PubMed ID: 30881461	2019

Mansour Djedaini

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