Heme oxygenase 1 (HO-1, encoded by the HMOX1 gene) is the rate-limiting enzyme that catalyzes heme degradation, and it has been reported to exert antioxidative effects. Recently, decidualization has been reported to confer resistance to environmental stress signals, protecting against oxidative stress. However, the effects and regulatory mechanism of HO-1 in decidual stromal cells (DSCs) during early pregnancy remain unknown. Here, we verified that the levels of HO-1 and heme in DSCs are increased compared with those in endometrial stromal cells. Additionally, the upregulation of HIF1A expression led to increased HMOX1 expression in DSCs possibly via nuclear factor erythroid 2-related factor (encoded by the NFE2L2 gene). However, addition of the competitive HO-1 inhibitor zinc protoporphyrin IX resulted in an increase in HIF1A expression. Hydrogen peroxide (H₂O₂) induced the production of reactive oxygen species (ROS), decreased the cell viability of DSCs in vitro, and upregulated the level of heme. As an HO-1 inducer, cobalt protoporphyrin IX decreased ROS production and significantly reversed the inhibitory effect of H₂O₂ on cell viability. More importantly, patients with unexplained spontaneous abortion had low levels of HO-1 that were insufficient to protect against oxidative stress. This study suggests that the upregulation of HO-1 expression via HIF1A protects DSCs against excessive heme-mediated oxidative stress. Furthermore, the excessive oxidative stress injury and impaired viability of DSCs associated with decreased HO-1 expression should be associated with the occurrence and/or development of spontaneous abortion.

Decidualization of uterine stromal cells plays an important role in the establishment of normal pregnancy. Previous studies have demonstrated that Acyl-CoA binding protein (Acbp) is critical to cellular proliferation, differentiation, mitochondrial functions, and autophagy. The characterization and physiological function of Acbp during decidualization remain largely unknown. In the present study, we conducted the expression profile of Acbp in the endometrium of early pregnant mice. With the occurrence of decidualization, the expression of Acbp gradually increased. Similarly, Acbp expression was also strongly expressed in decidualized cells following artificial decidualization, both in vivo and in vitro. We applied the mice pseudopregnancy model to reveal that the expression of Acbp in the endometrium of early pregnant mice was not induced by embryonic signaling. Moreover, P4 significantly upregulated the expression of Acbp, whereas E2 appeared to have no regulating effect on Acbp expression in uterine stromal cells. Concurrently, we found that interfering with Acbp attenuated decidualization, and that might due to mitochondrial dysfunctions and the inhibition of fatty acid oxidation. The level of autophagy was increased after knocking down Acbp. During induced decidualization, the expression of ACBP was decreased with the treatment of rapamycin (an autophagy inducer), while increased with the addition of Chloroquine (an autophagy inhibitor). Our work suggests that Acbp plays an essential role in the proliferation and differentiation of stromal cells during decidualization through regulating mitochondrial functions, fatty acid oxidation, and autophagy.

A successful pregnancy requires sufficient decidualization of endometrial stromal cells (ESCs). CD82, a metastasis suppressor, is a critical regulator for trophoblast invasion but the effect in decidualization was largely unknown. Here we reported that there was a high level of CD82 in DSC by the immunohistochemistry staining and flow cytometer analysis. Stimulation with prostaglandin E2 (PGE2) elevated the expression of CD82 in ESCs. In contrast, celecoxib, a selective COX-2 inhibitor, significantly downregulated the expression of CD82 in decidual stromal cells (DSCs). Bioinformatics analysis and further research showed that recombinant human interleukin (IL)-1β protein (rhIL-1β) upregulated CD82 in ESCs. Of note, blocking IL-1β signaling with anti-human IL-1β neutralizing antibody could reverse the stimulatory effect of PGE2 on CD82 in ESCs. Silencing CD82 resulted in the decease of the decidualization markers PRL and IGFBP1 mRNA levels in DSCs. More importantly, we observed rhIL-1β also upregulated the expression of COX-2, and the upregulation of PRL and IGFBP1 induced by rhIL-1β could be abolished by celecoxib in ESCs or CD82 deficiency in DSCs. This study suggests that CD82 should be a novel promotor for decidualization under a positive regulation of the COX-2/PGE2/IL-1β positive feedback loop.

Immune cells and cytokines have important roles in the pathogenesis of endometriosis. However, the production and role of cytokines of T helper type 1 (Th1) and Th2 cells in the progress of endometriosis have remained to be fully elucidated. The present study reported that the interferon (IFN)-γ levels and the percentage of IFN-γ⁺CD4⁺ cells were significantly increased in the peritoneal fluid (PF) at the early stage and maintained at a higher level at the advanced stage of endometriosis; furthermore, interleukin (IL)-10 and IL-10⁺CD4⁺ cells were elevated in the advanced stage of endometriosis. In addition, IL-2 levels in the PF at the advanced stage of endometriosis were elevated and negatively associated with IFN-γ expression. In a co-culture system of ectopic endometrial stromal cells (ESCs) and macrophages, elevated IL-2 was observed, and treatment with cytokines IL-2 and transforming growth factor-β led to upregulation of the ratio of IL-2⁺ macrophages. IL-27-overexpressing ESCs and macrophages were able to induce a higher ratio of IL-10⁺CD4⁺ T cells. Blocking of IL-2 with anti-IL-2 neutralizing antibody led to upregulation of the ratio of IFN-γ⁺CD4⁺ T cells in the co-culture system in vitro. Recombinant human IL-10 and IFN-γ promoted the viability, invasiveness and transcription levels of matrix metalloproteinase (MMP)2, MMP9, and prostaglandin-endoperoxide synthase 2 of ESCs, particularly combined treatment with IL-10 and IFN-γ. These results suggest that IL-2 and IL-27 synergistically promote the growth and invasion of ESCs by modulating the balance of IFN-γ and IL-10 and contribute to the progress of endometriosis.