Interleukin 11 and Activin A Synergise to Enhance Medroxyprogesterone But Not cAMP-Induced Decidualization of Human Endometrial Stromal Cells.

Abstract

Decidualization of endometrial stromal cells is a critical requirement for embryo implantation and the establishment of pregnancy. The mechanisms of human endometrial stromal cell (HESC) decidualization are poorly understood although locally produced factors including interleukin 11 (IL-11) and Activin A enhance decidualization. We hypothesised that IL-11 and Activin A interact to progress decidualization. The aim of this study was to examine IL-11 and activin A interactions during HESC decidualization. Decidualization of HESC was assessed using an ex vivo model in which estrogen (E)+medroxyprogesterone (MPA) or cAMP was administered to HESC cells for up to 14 days (d). Medium was collected and replenished from d 114 for prolactin (PRL, a decidual marker), IL-11 and Activin A assay. HESC were treated with IL-11(100ng/ml) or Activin A (50ng/ml) for 24 hours and cellular RNA was isolated for real-time RT-PCR analysis and culture medium was collected for ELISA assays. HESC treated with cAMP or E+MPA secreted PRL from d 1 and 4 respectively. At d 1, HESC treated with cAMP secreted more IL-11 and Activin A compared to controls (IL-11 vs control, 100±20% vs 1000±85%, p<0.05; Activin A vs control, 100±10% vs 180±20%, p<0.05). At d 1 of cAMP treatment, there was a greater % increase in IL-11 compared to Activin A secretion compared to controls and suggested IL-11 may be produced earlier than Activin A during the decidualization process. By contrast, there was no increase in IL-11 or Activin A secretion during E+MPA-induced decidualization. Co-treatment of HESC with E+MPA ± IL-11 or Activin A increased PRL secretion compared to E+MPA alone (410±40% vs 100±5%, p<0.05; 170±10% vs 100±5%; respectively) at d 7-8 of culture. This was further enhanced when HESC were cultured with E+MPA+IL-11+Activin A compared to either cytokine alone and E+MPA. This suggested IL-11 and Activin synergised to further progress decidualization compared to each cytokine and E+MPA. By contrast, coculture of HESC with cAMP and either IL-11 or Activin A or IL-11+Activin A, did not significantly increase PRL secretion from HESC compared to controls at any time point. HESC treated with Activin A for 24 hours did not affect IL-11 mRNA expression but significantly stimulated IL-11 secretion compared to controls (100±25% vs 345±136%, p<0.05). HESC treated with IL-11 did not change Activin A mRNA expression or secretion compared to controls. These data suggest Activin A regulated IL-11 secretion from HESC post-transcriptionally. This study demonstrated that IL-11 and Activin A synergised to enhance MPA induced decidualization and that Activin A regulated IL-11 secretion but not mRNA expression by HESC. Interestingly, while cAMP was a potent inducer of IL-11 and Activin A secretion coinciding with decidualization, both cytokines did not synergise with cAMP to regulate decidualization. This knowledge is important in understanding the mechanisms by which two key locally produced cytokines, IL-11 and Activin A, promote decidualization of HESC and thus the formation of decidua, an essential component of a functional placenta.