Glycodelin-A and IL-10 regulate human decidual macrophage differentiation from monocyte

Abstract

INTRODUCTION: To facilitate a successful pregnancy, it is important to confer immune tolerance to the semi-allogenic fetus. Macrophages are the second most abundant leukocytes (20~30%) in the decidua. Based on stimuli and function, macrophages are broadly classified as M1/inflammatory, M2/wound healing, and M3/regulatory macrophages. Gene expression profiling using microarray suggests that the decidual macrophages possess the phenotype of M2/M3 macrophages which secretes anti-inflammatory cytokines (e.g. IL-10) and immunomodulatory factors such as indoleamine 2,3-dioxygenase 1 (IDO-1) that contributes to immune tolerance. Aberrant levels of decidual macrophages are associated with fetal loss and pregnancy complications including intrauterine growth restriction and preeclampsia. Glyodelin-A (GdA) is an immunomodulatory glycoprotein abundantly found in the decidua during early pregnancy. The most well studied role of GdA is on feto-maternal defense. It promotes Th2 cytokine shift and regulates the differentiation/functions of immune cells, trophoblasts and endometrial cells. Hypothesis: We hypothesize that GdA is involved in the differentiation and biological functions of decidual macrophages. METHOD: Macrophage colony stimulating factors (MCSF) with/without IL-10 or GdA were used to differentiate human peripheral blood derived monocytes into macrophages. The phenotype of the macrophages was analyzed by qPCR and flow cytometry. The conditioned medium of the differentiated macrophages was also collected for cytokine/immunomodulatory factor determination using membranebased cytokine array, Western blotting and kynurenine assay. Flow cytometry-based latex beads assay was used to study the phagocytoic activity of differentiated macrophage. RESULT: The results showed that GdA induced the expression of decidual macrophage markers indoleamine-2,3 dioxygenase (IDO-1) and CD209 during MCSF-induced monocyte differentiation. IL-10, another molecule known to induce the differentiation of monocytes into decidual macrophages, induced the expression of CD209 and another decidual macrophage marker, neuropilin-1 (NRP-1). Interestingly, co-treatment of GdA and IL-10 significantly increased the expression of all three decidual macrophage markers in the MCSFdifferentiated macrophages. In addition, the conditioned medium of GdA-polarized macrophage exhibited a cytokine profile similar to that of decidual macrophages as demonstrated by cytokine array. GdA-polarized macrophages have a lower phagocytoic activity when compared to the control. CONCLUSION: To conclude, decidual GdA polarizes the differentiation of human monocyte towards decidual macrophage. Our data also indicates that GdA and IL-10 had additive effect on decidual macrophage differentiation. In addition, GdA regulates the biological functions of macrophages, including IDO-1 activity/production, phagocytosis and cytokine expression. Acknowledgements: This work was supported in part by grants from the Committee on Research and Conference Grant, Hong Kong Research Grant Council (HKU 774212M).