Deficiency in decidualization has been widely regarded as an important cause of spontaneous abortion. Generalized decidualization also includes massive infiltration and enrichment of NK cells. However, the underlying mechanism of decidual NK (dNK) cell residence remains largely unknown. Here, we observe that the increased macroautophagy/autophagy of decidual stromal cells (DSCs) during decidualization, facilitates the adhesion and retention of dNK cells during normal pregnancy. Mechanistically, this process is mediated through activation of the MITF-TNFRSF14/HVEM signaling, and further upregulation of multiple adhesion adhesions (e.g. Selectins and ICAMs) in a MMP9-dependent manner. Patients with unexplained spontaneous abortion display insufficient DSC autophagy and dNK cell residence. In addition, poor vascular remodeling of placenta, low implantation number and high ratio of embryo loss are observed in NK cell depletion mice. In therapeutic studies, low doses of rapamycin, a known autophagy inducer that significantly promotes endometrium autophagy and NK cell residence, and improves embryo absorption in spontaneous abortion mice models, which should be dependent on the activation of MITF-TNFRSF14/HVEM-MMP9-adhension molecules axis. This observation reveals novel molecular mechanisms underlying DSCs autophagy-driven dNK cell residence, and provides a potential therapeutic strategy to prevent spontaneous abortion. Abbreviations: ACTA2/αSMA: actin alpha 2, smooth muscle; ATG: autophagy-related; ATG5^over ESC: ATG5-overexpressed ESCs; BTLA: B and T lymphocyte associated; CDH1: cadherin 1; CDH5: cadherin 5; CXCL12: C-X-C motif chemokine ligand 12; dNK: decidual NK; DIC: decidual immune cell; DSC: decidual stromal cell; EOMES: eomesodermin; ESC: endometrial stromal cell; FCGR3A/CD16: Fc fragment of IgG receptor IIIa; HUVEC: human umbilical vein endothelial cell; ICAM: intercellular cell adhesion molecule; ILC: innate lymphoid cell; ITGB1: integrin subunit beta 1; ITGA2: integrin subunit alpha 2; IPA: Ingenuity Pathway Analysis; KIR2DL1: killer cell immunoglobulin like receptor, two Ig domains and long cytoplasmic tail 1; KLRD1/CD94: killer cell lectin like receptor D1; KLRK1/NKG2D: killer cell lectin like receptor K1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; 3-MA: 3-methyladenine; MITF: melanocyte inducing transcription factor; MiT-TFE: microphthalmia family of bHLH-LZ transcription factors; MMP9: matrix metalloproteinase 9; MTOR: mechanistic target of rapamycin kinase; NCAM1/CD56: neural cell adhesion molecule 1; NCR2/NKp44: natural cytotoxicity triggering receptor 2; NK: natural killer; KLRB1/NK1.1: killer cell lectin like receptor B1; NP: normal pregnancy; PBMC: peripheral blood mononuclear cell; PECAM1/CD31: platelet and endothelial cell adhesion molecule 1; pNK: peripheral blood NK; PRF1/Perforin: Perforin 1; PTPRC/CD45: protein tyrosine phosphatase receptor type C; Rapa: rapamycin; rh-TNFSF14/LIGHT: recombinant human TNFSF14/LIGHT; SA: spontaneous abortion; SELE: selectin E; SELP: selectin P; SELL: selectin L; siATG5 DSCs: ATG5-silenced DSCs; siTNFRSF14/HVEM DSCs: TNFRSF14/HVEM-silenced DSCs; TBX21/T-bet: T-box transcription factor 21; SQSTM1/p62: sequestosome 1; TNFRSF14/HVEM: TNF receptor superfamily member 14; TNFSF14/LIGHT: TNF superfamily member 14; uNK: uterine NK; UIC: uterine immune cell; USC: uterine stromal cell; VCAM1: vascular cell adhesion molecule 1; VIM: vimentin.

Endometriosis is an estrogen-dependent inflammatory disease. The anti-inflammatory cytokine IL-10 is also increased in endometriosis. IL-10 production by Th17 cells is critical for limiting autoimmunity and inflammatory responses. However, the mechanism of inducing IL-10-producing Th17 cells is still largely unknown. The present study investigated the differentiation mechanism and role of IL-10-producing Th17 cells in endometriosis. Here, we report that IL-10⁺Th17 cells are significantly increased in the peritoneal fluid of women with endometriosis, along with an elevation of IL-27, IL-6 and TGF-β. Compared with peripheral CD4⁺ T cells, endometrial CD4⁺ T cells highly expressed IL-27 receptors, especially the ectopic endometrium. Under external (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) and local (estrogen, IL-6 and TGF-β) environmental regulation, IL-27 from macrophages and endometrial stromal cells (ESCs) induces IL-10 production in Th17 cells in vitro and in vivo. This process may be mediated through the interaction between c-musculoaponeurotic fibrosarconna (c-Maf) and retinoic acid-related orphan receptor gamma t (RORγt), and associated with the upregulation of downstream B lymphocyte-induced maturation protein-1 (Blimp-1). IL-10⁺Th17 cells, in turn, stimulate the proliferation and implantation of ectopic lesions and accelerate the progression of endometriosis. These results suggest that IL-27 is a pivotal regulator in endometriotic immune tolerance by triggering Th17 cells to produce IL-10 and promoting the rapid growth and implantation of ectopic lesions. This finding provides a scientific basis for potential therapeutic strategies aimed at preventing the development of endometriosis, especially for patients with high levels of IL-10⁺Th17 cells.

Physiological pregnancy requires the maternal immune system to recognize and tolerate embryonic Ags. Although multiple mechanisms have been proposed, it is not yet clear how the fetus evades the maternal immune system. In this article, we demonstrate that trophoblast-derived thymic stromal lymphopoietin (TSLP) instructs decidual CD11c+ dendritic cells (dDCs)with increased costimulatory molecules; MHC class II; and Th2/3-type, but not Th1-type, cytokines. TSLP-activated dDCs induce proliferation and differentiation of decidual CD4+CD25− T cells into CD4+CD25+FOXP3+ regulatory T cells (Tregs) through TGF-β1. TSLP-activated dDC–induced Tregs display immunosuppressive features and express Th2-type cytokines. In addition, decidual CD4+CD25+FOXP3+ Tregs promote invasiveness and HLA-G expression of trophoblasts, resulting in preferential production of Th2 cytokines and reduced cytotoxicity in decidual CD56brightCD16− NK cells. Of interest, decreased TSLP expression and reduced numbers of Tregs were observed at the maternal–fetal interface during miscarriage. Our study identifies a novel feedback loop between embryo-derived trophoblasts and maternal decidual leukocytes, which induces a tolerogenic immune response to ensure a successful pregnancy.

What mechanism is involved in regulating the autophagy of endometrial stromal cells (ESCs), and does it participate in the pathogenesis of endometriosis? CXCL12 down-regulates secretory phase ESC autophagy. mTOR (mammalian target of rapamycin), the major negative regulator of autophagy, is abnormally increased in endometriotic lesions and is involved in the direct regulation of endometrial stromal cell (ESC) apoptosis. Autophagy was measured by transmission electron microscopy and immunofluorescence, and in vitro analysis was used to measure estrogen/CXCL12/CXCR4 signaling-mediated ESC autophagy. A total of 31 controls and 31 women with histologically confirmed endometriosis were included. We measured the autophagy level of normal and endometriosis-derived endometrium, and its relationship to the stage of endometriosis, as well as the potential molecular and signaling pathways that mediate the aberrant autophagy in endometriosis. Compared with control secretory phase ESCs, a significant reduction of the autophagy grade (as observed in TEM), punctuate LC3B staining (as observed in immunofluorescence assays), and autophagy-associated protein levels were exhibited in secretory phase eutopic ESCs (P < 0.05) and ectopic ESCs (P < 0.05) from women with endometriosis. In addition, the autophagy level was strongly negatively correlated with the CXCL12 concentration in ESCs (R² = −0.9694). However, there was no significant difference in autophagy grade or CXCL12 concentration between stage I–II and stage III–IV endometriosis-derived ectopic ESCs (P > 0.05). Based on a human autophagy PCR array, CXCL12 and CXCR4, which is the CXCL12 receptor, in ESCs were predicted to be molecules that mediate the abnormally lower autophagy in endometriosis. Accordingly, after estradiol (E2) treatment a marked increase in CXCL12 secretion (1.71-fold, P < 0.01) and CXCR4 expression (5.07-fold, P < 0.01) in secretory phase ESCs was observed together with decreases in autophagy grade (TEM), punctuate LC3B immunofluorescent staining and autophagy-associated protein levels (P < 0.05). These changes could be reversed by progesterone (P4) (P < 0.05). The suppression of autophagy induced by E2 and recombinant human CXCL12 protein could be abrogated by an anti-CXCR4 neutralizing antibody and by a NF-κB inhibitor (P < 0.05), respectively. In addition, estrogen-stimulated CXCL12 secretion led to a low population of S phase cells (P < 0.05), as well as a low level of apoptosis (P < 0.05) in secretory phase ESCs. Further studies are needed to examine the mechanism of autophagy on ESC apoptosis. Measures to increase in endometrial autophagy might be a valid, novel approach to reduce local E2-dependent growth of endometriotic tissue. This study was supported by the National Natural Science Foundation of China (NSFC) (81471513, 81471548 and 81270677), the Training Program for Young Talents of Shanghai Health System XYQ2013104, the Program for Zhuoxue of Fudan University, and the Program for Creative Talents Education of Key Disciplines of Fudan University. None of the authors has any conflict of interest to declare.

The aim of the current study was to determine the pattern of immune cells and related functional molecules in peripheral blood and at the maternal-fetal interface in women with unexplained recurrent spontaneous abortion (URSA). In part I, 155 women were included and divided into four groups: non-pregnant controls with no history of URSA (NPCs), pregnant controls with no history of URSA (PCs), non-pregnant women with a history of URSA (NPUs), and pregnant women with a history of URSA (PUs). Venous blood samples were collected and analyzed. In part II, 35 subjects with URSA and 40 subjects in the early stage of normal pregnancy who chose to undergo an abortion were recruited. Samples of the decidua were collected, and the proportion of immune cells and the expression of related molecules were evaluated. Peripheral regulatory T cells (Treg cells) increased in PCs compared to NPCs, but in women with URSA the flux of Treg cells disappeared when pregnancy occurred. Levels of interleukin-10 (IL-10), cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), and IL-17 and the ratio of Th17/Treg cells in peripheral blood remained stable among the four groups. At the maternal-fetal interface, the percentage of Treg cells, the level of CTLA-4 of CD4+CD25+CD127lo cells and CD4+Foxp3+ cells were significantly lower in women with URSA compared to controls, respectively. Levels of transforming growth factor-β1 (TGF-β1) mRNA and protein in the decidua significantly decreased in URSA while levels of IL-6 and tumor necrosis factor-ɑ (TNF-ɑ) and the Th17/Treg ratio significantly increased. In conclusion, peripheral Treg cells did not increase in pregnant women with URSA. The decrease in Treg cells and levels of CTLA-4 and TGF-β1 and as well as the increase in levels of IL-6 and TNF-ɑ, and the Th17/Treg ratio at the maternal-fetal interface might contribute to inappropriate maternal-fetal immune tolerance in URSA.