Comparison of Differential microRNA Expression Profiles between CD34⁺CD38⁻ and CD34⁺CD38⁺ Cells in Both Umbilical Cord Blood and Acute Myeloid Leukemia.

Recent studies demonstrated that some miRNAs played an important role in human normal and malignant hematopoiesis. MicroRNA expression is tissue and developmental stage restricted. Therefore, in order to address the roles of miRNAs in the regulation and maintenance of normal hematopoietiesis and leukemogenesis, in this study, we performed an analysis of differential genome-wide miRNA expressions of CD34⁺CD38⁻ and CD34⁺CD38⁺ cells from human umbilical cord blood(CB) and acute myeloid leukemia(AML) bone marrow, respectively.

Methods Mononuclear cells from cord blood (CB) and AML bone marrow were stained with monoclonal antibodies. CD34⁺CD38⁻ and CD34⁺CD38⁺ cells were sorted using FACSVantageSE. The mRNA were extracted and hybridized to miRCUURY array chip (Exiqon). The data were analyzed with GeneSpring and informatics technique. Real-time PCR for several miRNAs were performed to confirm the results obtained by miRNA chip analysis.

Results Based on the criteria of two or more fold changes of miRNA expression level, 73 miRNA overexpressions and 14 miRNA downexpressions were observed within CD34⁺CD38⁺ cells in comparison with CD34⁺CD38⁻ cells in CB. Interestingly, only one overexpression and10 downexpressions of miRNAs were found within CD34⁺CD38⁺ cells as compared with CD34⁺CD38⁻ cells in AML. This might suggest the less differential and maturational activities during the transition from CD34⁺CD38⁻ cells to CD34⁺CD38⁺ cells in AML as compared with their normal counterpart. In comparison between CB and AML, 94 over-expressed and 28 down-expressed miRNAs were displayed in AML CD34⁺CD38⁻ cells. More specifically, miR-155, -190 were down-expressed in both CB and leukemic CD34⁺CD38⁺ subsets, while miR-220, -499 were over-expressed in CB CD34⁺CD38⁺ cells and down-expressed in leukemic CD34⁺CD38⁺ cells. Putative hematopoiesis-specific target genes were analyzed with informatics technique. We found that each miRNA had several hundred genes as putative targets and each target gene had more than one miRNA predicted to be its regulator. For example, hsa-miR-509 has 561 putative target genes, of which IL1A, IL3RA1, FGFR2, SMAD2 are hematopoiesis-specific, and SMAD2 has 34 miRNAs as its regulators.

Conclusion: The miRNAs play important roles in the developments of both hematopoiesis and leukemogenesis. The analysis of differential microRNA expression profiles may be a powerful tool to allow us insight on the mechanisms of regulations of hematopoietic stem cells and leukemic stem cells.