Pro-Angiogenic Activity of Monocytic-Type Myeloid-Derived Suppressor Cells from Balb/C Mice Infected with Echinococcus Granulosus and the Regulatory Role of miRNAs

Abstract

Background/aims: This study aims to predict the pro-angiogenic functions of monocytic-type myeloid-derived suppressor cells (M-MDSCs) derived from mice infected with Echinococcus granulosus.

Methods: M-MDSCs were collected from Balb/c mice infected with E. granulosus and normal mice (control) and cultured in vitro. Human umbilical vein endothelial cells (HUVECs) were stimulated with the cell supernatant, and angiogenesis was investigated and analysed by the Angiogenesis module of the software NIH Image J. RNA was extracted from fresh isolated M-MDSCs and analysed with miRNA microarray; differentially expressed miRNAs and their potential functions were analysed through several bioinformatics tools. Finally, quantitative PCR was used to confirm the results of microarray analysis.

Results: M-MDSCs from mice infected with E. granulosus could promote the formation of tubes from HUVECs in vitro. Moreover, vascular endothelial growth factor (VEGF) showed significantly high expression, whereas soluble fms-like tyrosine kinase-1 (sFlt-1) showed low expression at the transcriptional level in M-MDSCs from mice infected with E. granulosus. Microarray analysis of miRNAs showed that 28 miRNAs were differentially expressed in M-MDSCs from the two experimental mice groups, and 272 target genes were predicted using the microRNA databases TargetScan, PITA and microRNAorg. These target genes were mainly involved in the biological processes of intracellular protein transport, protein targeting to the lysosome and protein transport, and mainly located in the cytoplasm, neuronal cell body and membrane. Moreover, they were mainly involved in the molecular functions of protein binding, metal ion binding and SH3 domain binding. Further, the differentially expressed miRNAs were mainly enriched in the endocytosis, Wnt and axon guidance pathways, as well as the MAPK, focal adhesion, PI3K-Akt, cAMP, mTOR and TGF-β signalling pathways, which are linked to immunoregulation and angiogenesis based on the results of bioinformatics analysis with DIANA-miRPath 3.0. In addition, the expression of eight miRNAs was randomly verified by quantitative PCR independently in three mice infected with E. granulosus and three normal mice.

Conclusion: M-MDSCs have a potential angiogenic role during E. granulosus infection, and miRNAs may play a role in the immune response and angiogenesis functions of M-MDSCs through regulation of the identified signalling pathways.

Keywords: Angiogenesis; Echinococcus granulosus; MicroRNA; Monocytic-type myeloid-derived suppressor cells.