*Purpose: Myeloid-derived suppressor cells (MDSC) are expanded in inflammation conditions and can control alloreactive T cell responses. Granulocyte-colony stimulating factor (GCSF) is known to induce MDSCs. The molecular profile of GCSF-induced MDSCs remain unexplored and may have significant relevance for transplantation.

*Methods: MDSCs were sorted from spleens of mice treated with mouse recombinant GCSF (200 ng/kg/d for 4 d) or PBS as naïve control. Microarrays (Affymetrix, mouse Clariom S GeneChip) were performed using total RNAs from each group and followed by bioinformatics analyses using Transcriptome Analysis Console (TAC) to identify differentially expressed genes (DEGs). Functional annotation of these DEGs and mining of key genes and potential molecular mechanisms were then performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID).

*Results: GCSF induced MDSCs suppressed CD4⁺ T cell proliferation in vitro, while naïve MDSC did not. Amongst GCSF induced MDSCs, 2,499 DEGs were identified, with 903 upregulated and 1,596 downregulated genes (Fold Change >2, p<0.05) between naïve and GCSF MDSC. Differential expression of 5 top genes (c-Kit, Saa3, Cdh1, Nos 2, Ccl2) was verified by qRT-PCR. Per Gene Ontology (GO), these DEGs primarily involved in immune system processes, innate immune responses, inflammatory responses, cell cycle, and cellular proliferation. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that these DEGs were primarily associated with metabolic pathways, HIF-1, RIG-1 -like receptor, Toll-like receptor, tumor necrosis factor (TNF), and NF-kappa B signaling pathway. BioCarta Pathway analysis revealed genes related to NO2-dependent IL-12 pathway, known for activation of macrophages and NK cells were differentially regulated by GCSF treatment.

*Conclusions: We obtained a list of consistent DEGs in immunosuppressive GCSF MDSC, which especially 93 genes, including cell adhesion molecule 1 (Cadm1), toll-like receptor 1, 3, 7, and 11 (Tlr1, Tlr3, Tlr7, Tlr11), myeloid differentiation primary response 88 (MYD88), janus kinase 2 and 3 (Jak2, Jak3), retinoic acid early inducible 1 (Rae-1) were categorized in innate immune response. These results may offer potential targets for further studies to understand molecular mechanism responsible for immune suppressive function of MDSCs.

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