Changes in Gene Expression during G-CSF-Induced Emergency Granulopoiesis in Humans

Emergency granulopoiesis refers to the increased production of neutrophils in bone marrow and their release into circulation induced by severe infection. Several studies point to a critical role for granulocyte colony-stimulating factor (G-CSF) as the main mediator of emergency granulopoiesis. However, the consequences of G-CSF stimulation on the transcriptome of neutrophils and their precursors have not yet been elucidated in humans. Here, we investigate the changes in mRNA and miRNA expression in successive stages of neutrophil development following in vivo administration of G-CSF in humans, mimicking emergency granulopoiesis. Blood samples were collected from healthy individuals after five days of G-CSF administration. Neutrophil precursors were sorted into discrete stages of maturation by flow cytometry and extracted RNA was subjected to microarray analysis. mRNA levels were compared to previously published expression levels in corresponding populations of neutrophil precursors isolated from bone marrow of untreated, healthy individuals. miRNA expression was investigated in the most mature cell population to determine G-CSF-induced changes in circulating neutrophils. G-CSF substantially affected mRNA and miRNA expression patterns, demonstrating significant impact on neutrophil development and function. 1110 mRNAs were differentially expressed more than 2-fold with G-CSF while the treatment induced changes in the levels of 73 miRNAs in the mature population. In addition, G-CSF treatment reduced the levels of four out of five measured granule proteins in mature neutrophils including hCAP-18, which was completely deficient in neutrophils from G-CSF-treated donors. Cell cycle analysis pointed towards an induced proliferative capacity of myelocytes. These results indicate that multiple biological processes are altered in order to satisfy the increased demand for neutrophils during G-CSF-induced emergency granulopoiesis.