Combinatorial Effects of Boron Compounds on Immunophenotypic Modulation of Mouse Hematopoietic Stem Cell Subsets Ex Vivo

Background/Objectives: Hematopoietic stem cells (HSCs) sustain lifelong blood cell production and hold therapeutic promise, yet their ex vivo expansion remains constrained by an incomplete understanding of the metabolic and cellular mechanisms governing self-renewal. In this study, we investigated whether boron compounds boric acid (BA), sodium pentaborate pentahydrate (NaB), and sodium 2-pentaborate pentahydrate-8 (Na2B8) can promote the expansion of mouse HSCs by modulating key stem cell populations linked to metabolic fitness. Methods: Lineage-negative (Lin-) cells were magnetically isolated and treated with each boron compound for four days, followed by flow cytometric analysis of c-Kit, Sca-1, Lin-c-Kit+Sca-1+ (LSK), and LSKCD34low HSC-enriched subsets. Results: Our results show that boron derivatives exert distinct effects on these cellular markers. Notably, NaB treatment significantly increased the Lin-Sca-1+ cell fraction, while Na2B8 elevated both LSK and LSKCD34low ratios. Furthermore, the BA+NaB combination produced a statistically significant proliferative effect on Sca-1+ and c-Kit+ (CD117) cells. Conclusions: These findings indicate that specific boron compounds enhance ex vivo HSC expansion through yet-to-be-defined mechanisms that underpin HSC self-renewal. Further mechanistic studies are warranted to delineate the precise metabolic targets, but these results highlight boron compounds as promising tools for improving HSC expansion strategies.