Objective: MicroRNA (miRNA) expression profiling was performed on ex vivo differentiating erythroid cultures derived from human umbilical cord blood (UCB) CD34 cells and K562 cells to identify miRNAs involved in erythropoiesis.
Materials and methods: Both cell types were subjected to growth factor cocktails stimulating erythroid differentiation and were harvested for small RNA extraction at regular intervals. miRNAs with at least a 1.5-fold expression increase or decrease compared to unstimulated (day 0) cells were identified by array hybridization. Validity of the expression array was confirmed by quantitative real-time polymerase chain reaction on randomly selected miRNAs.
Results: Hierarchical clustering analysis and comparison between stimulated UCB-derived CD34 cells and K562 cells revealed miRNAs that are critical for erythroid development and maturation. Correlation analysis on UCB-derived CD34 cells shows that miR-15b, miR-16, miR-22, and miR-185 have strong positive correlation to the appearance of erythroid surface antigens (CD71, CD36, and CD235a) and hemoglobin synthesis, while miR-28 has an inverse relationship to the expression of these markers. Signature miRNAs associated with common myeloid/erythroid progenitor commitment (e.g., miR-181 family, miR-221, miR-154), early erythroid commitment (e.g., miR-32, miR-136, miR-137), and maturation (miR-22, miR-28, miR-185) were also identified by temporal correlation analysis. These miRNAs are predicted to target genes involved in cell development and differentiation.
Conclusion: Probable signature miRNAs for erythropoiesis are identified. Further experimentations are needed to define the roles of these miRNAs in regulating erythroid commitment.