Exponential expansion of CD34+ cells in response to StemRegenin-1 occurs with minimal changes in gene expression

Hematopoietic stem/progenitor cell transplantation (HSCT) is a well-established treatment option for hematological and other disorders. Umbilical cord blood (UCB) is a rich source of hematopoietic stem and progenitor cells (HSPCs). Cluster of Differentiation (CD)34 is commonly used as a cell surface marker to identify and isolate HSPCs. Transplantation using a single UCB unit may be associated with delayed hematopoietic reconstitution as it may not contain a sufficient number of HSPCs required for adult transplantation. One way of overcoming this limitation is through ex vivo expansion of UCB-derived HSPCs using the aryl hydrocarbon receptor (AhR) antagonist, StemRegenin-1 (SR1), which promotes the expansion of HSPCs. Our study investigated the effects of SR1 on the transcriptome of expanded CD34+ cells from UCB, and we also report on a comparison between the transcriptome profiles of 7-day expanded and non-expanded CD34+ cells. CD34+ HSPCs expanded with SR1 for 7 days displayed two significantly downregulated genes, cytochrome P450, family 1, subfamily B, polypeptide 1 (CYP1B1) and erythrocyte membrane protein band 4.1-like 3 (EPB41L3), when compared to controls (without SR1). Transcriptome analysis of CD34+ HSPCs expanded for 7 days using SR1 revealed that 391 genes were significantly upregulated, while 456 genes were significantly downregulated when compared to non-expanded CD34+ cells. In conclusion, though hundreds of genes were differentially expressed between SR1-expanded and non-expanded CD34+ HSPCs, only two genes were significantly downregulated in cells expanded for 7 days with SR1 versus control at the same time point (without SR1). RNA was extracted from freshly isolated CD34+ cells (Day0, D0) and 7-day expanded CD34+ cells (Day 7, D7) with and without SR1.