Gene expression and protein secretion patterns in decidual macrophages and different M1 and M2 macrophage populations with focus on M-CSF and IL-10 as polarising factors in JOURNAL OF REPRODUCTIVE IMMUNOLOGY, vol 90, issue 2, pp 151-151

• Introduction: We have recently observed (Svensson et al., data to be published) that M-CSF and IL-10, among several factors tested, are able to induce macrophages (MΦ) with phenotypic characteristics of decidual MΦ with expression of typical M2, or immune regulatory, cell surface markers (scavenger receptor, mannose receptor, DC-SIGN). The aim of this study was to investigate in a comprehensive manner whether this finding could be shown by an extended mapping of secreted molecules and also at the gene expression level.Materials and methods: CD14+ blood monocytes and decidual MΦ from healthy first trimester pregnant women (n = 11) were isolated by immunomagnetic cell sorting (MACS). MΦ were also generated in vitro from MACS-sorted CD14+ blood monocytes from non-pregnant women. RNA was isolated from blood monocytes and MΦ and the expression of 100 decidual MΦ-associated genes (Gustafsson et al., PlosOne 2008) was analysed with a custom microarray. RT-PCR was used to analyse the gene expression of IRF5, which was recently associated with classically activated (M1) MΦ. A multiplex bead assay was used to quantify the levels of cytokines and chemokines in conditioned media.Results: To estimate the similarity of the in vitro differentiated MΦ with decidual MΦ, we performed hierarchical clustering of differentially regulated genes. M1 MΦ and MΦ treated with GM-CSF and IL-4/13 formed their own branches, indicating transcriptional profiles clearly differing from all other MΦ types analysed. MΦ differentiated with M-CSF alone or with IL-10, regardless of the growth factor used, clustered together with decidual MΦ, supporting their close relationship. Genes similarly regulated in these macrophages were not restricted to immune modulating genes. This group included the M2-associated chemokines CCL2 and CCL18, the immune modulating B7 family-related VSIG4, the angiogenic insulin-like growth factor-1 and the M2-associated folate receptor β-encoding FOLR2 and selenoprotein-encoding SEPP1. The M2 polarisation status of decidual MΦ was confirmed by low expression of the M1-associated transcription factor IRF5, and comparable levels were detected in M-CSF- and IL-10-stimulated MΦ. IRF5 expression was higher in M1 MΦ and, surprisingly, also in IL-4/13-stimulated MΦ. As to protein secretion, decidual and M-CSF/IL-10-stimulated MΦ were found to produce comparable levels of IL-10 and the pro-inflammatory cytokines IL-6 and TNF, while M1 MΦ produced significantly higher levels of TNF and did not produce IL-10. Decidual and M-CSF/IL-10-stimulated MΦ also produced high levels of the monocyte- and granulocyte-recruiting chemokines CCL2, CCL4 and CXCL1, while the Th1 cell-recruiting CXCL10 and the Th2 cell-recruiting CCL22 were only produced at low levels. CXCL10 was highest in M1 MΦ, while CCL22 levels were highest in GM-CSF and/or IL-4/13-stimulated MΦ.Conclusions: Our data consistently shows a central role for M-CSF and IL-10 as polarising agents for decidual MΦ, while Th2 and pro-inflammatory agents induce MΦ with clearly differing characteristics. We hypothesise that decidual MΦ have a predominant homeostatic function. This is supported by their low production of both Th1 and Th2 cell-recruiting chemokines. It is thus likely that M-CSF and IL-10 shape the polarisation of decidual MΦ contributing to the homeostatic and tolerant immune environment required for successful fetal development.

Nyckelord

Decidual macrophages

M-CSF

IL-10

Tolerance

Pregnancy

MEDICINE

MEDICIN

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