Valproic acid-expanded cord blood CD34+CD90+ cells are functionally distinct based on their origin

Al Rabee Kassis; Amudha Ganapathy; Amal Mechaal; Seungwon An; John G Quigley; Dolores Mahmud; Nadim Mahmud

doi:10.1093/stmcls/sxaf079

Valproic acid-expanded cord blood CD34+CD90+ cells are functionally distinct based on their origin

Stem Cells. 2025 Dec 13:sxaf079. doi: 10.1093/stmcls/sxaf079. Online ahead of print.

Authors

Al Rabee Kassis¹, Amudha Ganapathy¹, Amal Mechaal¹, Seungwon An², John G Quigley^{1

3}, Dolores Mahmud¹, Nadim Mahmud^{1

2

3}

Affiliations

¹ Division of Hematology/Oncology, Department of Medicine, University of Illinois College of Medicine, Chicago, IL, 60612, USA.
² Clinical Stem Cell Laboratory, UI Health, Chicago, IL, 60612, USA.
³ University of Illinois Cancer Center, Chicago, IL, 60612, USA.

PMID: 41389838
DOI: 10.1093/stmcls/sxaf079

Abstract

Hematopoietic stem cell (HSC) transplantation is a potentially curative option for patients with hematologic malignancies, but donor shortages impact graft availability. Umbilical cord blood (UCB) is a viable alternative source of HSC, however the limited numbers present in a single unit have spurred efforts to expand HSC ex vivo. We previously demonstrated that the addition of valproic acid (VPA), an anti-convulsive drug, to CB cell cultures promotes maintenance of functional HSC, but not expansion. However, it has been proposed that VPA primarily induces mitochondrial reprogramming of mature CD34+CD90- cells to more primitive CD34+CD90+ cells, rather than the replication of CD34+CD90+ cells in culture. To determine which fraction of the CD34+CD90+ cells present after culture in VPA were derived from CD34+CD90- vs. CD34+CD90+ cells, we examined the functionality of CD34+CD90+ cells derived from each flow cytometry-sorted population. During culture in VPA there was a significant increase in CD34+CD90+ cell number; the majority arising from pre-existing CD34+CD90+ cells, with minimal contribution from CD34+CD90- cells. Colony-forming unit (CFU) assays revealed reduced plating efficiency and xeno-transplantation studies demonstrated diminished in vivo hematopoietic reconstitution potential of CD34+CD90+ cells derived from relatively committed CD34+CD90- cells. Our findings indicate that while VPA supports CD34+CD90+ cell expansion, the CD34+CD90+ cells derived from CD34+CD90- cells are functionally more differentiated than those derived directly from CD34+CD90+ cells, with increased mitochondrial mass and membrane potential, but reduced regenerative potential. These results emphasize the need for functional assessments of culture-expanded HSCs to accurately determine their therapeutic potential.

Keywords: epigenetic; phenotype-function discordance; reprogramming; self-renewal; stem cell expansion; umbilical cord blood.

© The Author(s) 2025. Published by Oxford University Press. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.