Reproduction Abstracts

Introduction: Decidualisation occurs in the secretory phase of the menstrual cycle, transforming endometrial stromal cells to secretory decidual stromal cells (DSC). Extensive cross-talk occurs between DSC and immune cells. In the first trimester of pregnancy the decidua is rich with maternal leukocytes, made up of ~70% NK cells and ~20% macrophages. The number of NK and macrophage cells increases during decidualisation and into the first trimester of pregnancy. Decidual NK (dNK) cells have a distinctly different phenotype to peripheral blood NK with a unique repertoire of activatory and inhibitory receptors. dNK and macrophages have roles in spiral artery remodelling before and during trophoblast invasion.

Materials and methods: DSC, dNK and macrophages were isolated from tissue obtained from first trimester terminations of pregnancy. DSC were re-decidualised in vitro using cAMP and medroxyprogesterone 17-acetate (MPA) conditioned media (CM) was collected after 72 hours. Decidualisation was measured by secretion of IGFBP1, PRL and expression of FOXO1. dNK and macrophages were incubated with DSC CM for 6 hour, media was changed to 10% (v/v) FBS RPMI and cells incubated for a further 12 hours. CM was collected IL-6 and IL-8 secretion via ELISA and cell receptor expression via flow cytometer was analysed.

Results and discussion: Decidualisation of DSC increased secretion of IGFBP1, PRL and FOXO1 (P<0.05). DSC CM did not alter dNK receptor expression. DSC CM significantly stimulated dNK secretion of IL-8 and IL-6 (P<0.05). DSC CM did not significantly alter macrophage receptor expression or secretion of IL-8 or IL-6. These results indicate that decidualised DSC secreted factors do not affect the receptor expression of decidual NK or macrophage cells. However, DSC activated dNK stimulating them to secrete the chemokines IL-8 and IL-6. These results provide support for the hypothesis that DSC interact and stimulate NK cells in the first trimester of pregnancy.