BMP/SMAD1/5 Signaling in the Endometrial Epithelium Is Essential for Receptivity and Early Pregnancy

Affinity-tagged SMAD1 and SMAD5 mouse lines reveal transcriptional reprogramming mechanisms during early pregnancy

Endometrial decidualization, a prerequisite for successful pregnancies, relies on transcriptional reprogramming driven by progesterone receptor (PR) and bone morphogenetic protein (BMP)-SMAD1/SMAD5 signaling pathways. Despite their critical roles in early pregnancy, how these pathways intersect in reprogramming the endometrium into a receptive state remains unclear. To define how SMAD1 and/or SMAD5 integrate BMP signaling in the uterus during early pregnancy, we generated two novel transgenic mouse lines with affinity tags inserted into the endogenous SMAD1 and SMAD5 loci (Smad1HA/HA and Smad5PA/PA). By profiling the genome-wide distribution of SMAD1, SMAD5, and PR in the mouse uterus, we demonstrated the unique and shared roles of SMAD1 and SMAD5 during the window of implantation. We also showed the presence of a conserved SMAD1, SMAD5, and PR genomic binding signature in the uterus during early pregnancy. To functionally characterize the translational aspects of our findings, we demonstrated that SMAD1/5 knockdown in human endometrial stromal cells suppressed expressions of canonical decidual markers (IGFBP1, PRL, FOXO1) and PR-responsive genes (RORB, KLF15). Here, our studies provide novel tools to study BMP signaling pathways and highlight the fundamental roles of SMAD1/5 in mediating both BMP signaling pathways and the transcriptional response to progesterone (P4) during early pregnancy.

Impaired bone morphogenetic protein (BMP) signaling pathways disrupt decidualization in endometriosis

Endometriosis is linked to increased infertility and pregnancy complications due to defective endometrial decidualization. We hypothesized that identification of altered signaling pathways during decidualization could identify the underlying cause of infertility and pregnancy complications. Our study reveals that transforming growth factor β (TGFβ) pathways are impaired in the endometrium of individuals with endometriosis, leading to defective decidualization. Through detailed transcriptomic analyses, we discovered abnormalities in TGFβ signaling pathways and key regulators, such as SMAD4, in the endometrium of affected individuals. We also observed compromised activity of bone morphogenetic proteins (BMP), a subset of the TGFβ family, that control endometrial receptivity. Using 3-dimensional models of endometrial stromal and epithelial assembloids, we showed that exogenous BMP2 improved decidual marker expression in individuals with endometriosis. Our findings reveal dysfunction of BMP/SMAD signaling in the endometrium of individuals with endometriosis, explaining decidualization defects and subsequent pregnancy complications in these individuals.

Affinity-tagged SMAD1 and SMAD5 mouse lines reveal transcriptional reprogramming mechanisms during early pregnancy

Endometrial decidualization, a prerequisite for successful pregnancies, relies on transcriptional reprogramming driven by progesterone receptor (PR) and bone morphogenetic protein (BMP)-SMAD1/SMAD5 signaling pathways. Despite their critical roles in early pregnancy, how these pathways intersect in reprogramming the endometrium into a receptive state remains unclear. To define how SMAD1 and/or SMAD5 integrate BMP signaling in the uterus during early pregnancy, we generated two novel transgenic mouse lines with affinity tags inserted into the endogenous SMAD1 and SMAD5 loci (Smad1HA/HA and Smad5PA/PA). By profiling the genome-wide distribution of SMAD1, SMAD5, and PR in the mouse uterus, we demonstrated the unique and shared roles of SMAD1 and SMAD5 during the window of implantation. We also showed the presence of a conserved SMAD1, SMAD5, and PR genomic binding signature in the uterus during early pregnancy. To functionally characterize the translational aspects of our findings, we demonstrated that SMAD1/5 knockdown in human endometrial stromal cells suppressed expressions of canonical decidual markers (IGFBP1, PRL, FOXO1) and PR-responsive genes (RORB, KLF15). Here, our studies provide novel tools to study BMP signaling pathways and highlight the fundamental roles of SMAD1/5 in mediating both BMP signaling pathways and the transcriptional response to progesterone (P4) during early pregnancy.

Endometrial TGFβ signaling fosters early pregnancy development by remodeling the fetomaternal interface

The endometrium is a unique and highly regenerative tissue with crucial roles during the reproductive lifespan of a woman. As the first site of contact between mother and embryo, the endometrium, and its critical processes of decidualization and immune cell recruitment, play a leading role in the establishment of pregnancy, embryonic development, and reproductive capacity. These integral processes are achieved by the concerted actions of steroid hormones and a myriad of growth factor signaling pathways. This review focuses on the roles of the transforming growth factor β (TGFβ) pathway in the endometrium during the earliest stages of pregnancy through the lens of immune cell regulation and function. We discuss how key ligands in the TGFβ family signal through downstream SMAD transcription factors and ultimately remodel the endometrium into a state suitable for embryo implantation and development. We also focus on the key roles of the TGFβ signaling pathway in recruiting uterine natural killer cells and their collective remodeling of the decidua and spiral arteries. By providing key details about immune cell populations and TGFβ signaling within the endometrium, it is our goal to shed light on the intricate remodeling that is required to achieve a successful pregnancy.

Impaired bone morphogenetic protein (BMP) signaling pathways disrupt decidualization in endometriosis

Endometriosis is linked to increased infertility and pregnancy complications due to defective endometrial decidualization. We hypothesized that identification of altered signaling pathways during decidualization could identify the underlying cause of infertility and pregnancy complications. Our study reveals that transforming growth factor β (TGFβ) pathways are impaired in the endometrium of individuals with endometriosis, leading to defective decidualization. Through detailed transcriptomic analyses, we discovered abnormalities in TGFβ signaling pathways and key regulators, such as SMAD4, in the endometrium of affected individuals. We also observed compromised activity of bone morphogenetic proteins (BMP), a subset of the TGFβ family, that control endometrial receptivity. Using 3-dimensional models of endometrial stromal and epithelial assembloids, we showed that exogenous BMP2 improved decidual marker expression in individuals with endometriosis. Our findings unveil a previously unidentified dysfunction in BMP/SMAD signaling in the endometrium of individuals with endometriosis, explaining decidualization defects and subsequent pregnancy complications in these individuals.

CREB1 Is Involved in miR-134-5p-Mediated Endometrial Stromal Cell Proliferation, Apoptosis, and Autophagy

The successful establishment of endometrial receptivity is a key factor in ensuring the fertility of ewes and their economic benefits. Hu sheep have attracted attention due to their high fecundity and year-round estrus. In this study, we found that in the luteal phase, the uterine gland density, uterine coefficient, and number of uterine caruncles of high-fertility Hu sheep were higher than those of low-fertility Hu sheep. Thousands of differentially expressed genes were identified in the endometrium of Hu sheep with different fertility potential using RNA sequencing (RNA-Seq). Several genes involved in endometrial receptivity were screened using bioinformatics analysis. The qRT-PCR analysis further revealed the differential expression of cAMP reactive element binding protein-1 (CREB1) in the Hu sheep endometrium during the estrous cycle. Functionally, our results suggested that CREB1 significantly affected the expression level of endometrial receptivity marker genes, promoted cell proliferation by facilitating the transition from the G1 phase to the S phase, and inhibited cell apoptosis and autophagy. Moreover, we observed a negative linear correlation between miR-134-5p and CREB1 in the endometrium. In addition, CREB1 overexpression prevented the negative effect of miR-134-5p on endometrial stromal cell (ESC) growth. Taken together, these data indicated that CREB1 was regulated by miR-134-5p and may promote the establishment of uterine receptivity by regulating the function of ESCs. Moreover, this study provides new theoretical references for identifying candidate genes associated with fertility.

Impaired bone morphogenetic protein signaling pathways disrupt decidualization in endometriosis

It is hypothesized that impaired endometrial decidualization contributes to decreased fertility in individuals with endometriosis. To identify the molecular defects that underpin defective decidualization in endometriosis, we subjected endometrial stromal cells from individuals with or without endometriosis to time course in vitro decidualization with estradiol, progesterone, and 8-bromo-cyclic-AMP (EPC) for 2, 4, 6, or 8 days. Transcriptomic profiling identified differences in key pathways between the two groups, including defective bone morphogenetic protein (BMP)/SMAD4 signaling (ID2, ID3, FST), oxidate stress response (NFE2L2, ALOX15, SLC40A1), and retinoic acid signaling pathways (RARRES, RARB, ALDH1B1). Genome-wide binding analyses identified an altered genomic distribution of SMAD4 and H3K27Ac in the decidualized stromal cells from individuals without endometriosis relative to those with endometriosis, with target genes enriched in pathways related to signaling by transforming growth factor β (TGFβ), neurotrophic tyrosine kinase receptors (NTRK), and nerve growth factor (NGF)-stimulated transcription. We found that direct SMAD1/5/4 target genes control FOXO, PI3K/AKT, and progesterone-mediated signaling in decidualizing cells and that BMP2 supplementation in endometriosis patient-derived assembloids elevated the expression of decidualization markers. In summary, transcriptomic and genome-wide binding analyses of patient-derived endometrial cells and assembloids identified that a functional BMP/SMAD1/5/4 signaling program is crucial for engaging decidualization.

Shoutai Wan regulates glycolysis imbalance at the maternal-fetal interface in threatened abortion mice

ETHNOPHARMACOLOGICAL RELEVANCE

Threatened abortion is a common disease among women of childbearing age. Its high incidence rate and unclear etiology, seriously threaten women's physical and mental health. Shoutai Wan (STW) is a traditional Chinese medicine decoction for treating abortion. It has a long history of treating threatened abortion by tonifying the kidney and calming the fetus. However, the mechanism of STW remains unclear.

AIM OF STUDY

To study the mechanism and potential benefit of STW in pregnant mice with hydrocortisone and mifepristone-induced threatened abortion.

MATERIALS AND METHODS

The STW compounds were identified using gas chromatography-mass spectrometry analysis. STW-H, STW-M, or STW-L was separately given 3 mg/ml, 1.5 mg/ml and 0.75 mg/ml STW in the morning, and 2 mg/ml hydrocortisone in the afternoon from gestation day (D) 1-9 and once with 0.4 mg/kg mifepristone on D10. Didroxyprogesterone (0.1 mg/ml) and equal dose pure water were used to replace STW in didroxyprogesterone (DYD) group and model group respectively. The control group used pure water to replace STW, hydrocortisone, and mifepristone. We performed morphological and histological analyses of the maternal-fetal interface on day 10.

RESULTS

The embryo loss rate in the STW-H and DYD groups was lower than that in the model group. Hematoxylin and eosin (HE) staining suggested that the morphology of maternal-fetal interface was improved in the STW-H and DYD groups. Immunohistochemical (IHC), Quantitative Reverse Transcription Polymerase Chain Reactionstaining (qRT-PCR), and Western blot (WB) results indicated that HIF-1α expression in the maternal-fetal interface of the STW-H and DYD groups was higher than that in model group. The activities of HK, PKM, LDH and the concentration of lactic acid in the STW-H and DYD groups were higher than those in model group. Furthermore, the protein and mRNA levels of HK2, PKM2, LDHA, MCT4, and GPR81 were higher in the STW-H and DYD groups than those in the model group.

CONCLUSIONS

STW can reduce the pregnancy loss rate by regulating the glycolysis balance at the maternal-fetal interface of kidney deficiency threatened abortion model mice.

Assessment of BMP7, SMAD4, and CDH1 Expression Profile and Regulatory miRNA-542-3p in Eutopic and Ectopic Endometrium of Women with Endometriosis

Alterations in the expression of numerous genes and the miRNAs that are recognized as their regulators in the endometrial cells of women with endometriosis may disrupt the intracellular signaling pathways associated with epithelial–mesenchymal transition (EMT). So far, the functional role of BMP7 in endometrial physiology has been confirmed, especially in the context of fertility, but the role of the activation of a specific mechanism operating through the BMP–SMAD–CDH1 axis in the formation of endometrial lesions remains unexplored. The aim of this study was to evaluate the expression profile of miR-542-3p and the EMT markers (BMP7, SMAD4, CDH1) in matched eutopic endometrium (EUE) and ectopic endometrium (ECE) samples from women with endometriosis in relation to healthy women. The levels of expression of the studied genes and miRNA in peripheral blood mononuclear cells (PBMCs) obtained from women diagnosed with endometriosis and those without the disease were also evaluated. Fifty-four patients (n = 54: with endometriosis—n = 29 and without endometriosis—n = 25) were included in the study. A comparative analysis of the relative mean expression values (RQ) of the studied mRNA and miRNA assessed by RT-qPCR demonstrated downregulation of BMP7, SMAD4, and CDH1 expression in ectopic lesions and upregulation in the eutopic endometrium compared with the control group. In the eutopic tissue of women with endometriosis, miR-542-3p expression was similar to that of the control but significantly lower than in endometrial lesions. We also confirmed a trend towards a negative correlation between miR-542-3p and BMP7 in ectopic tissue, and in PBMC, a significant negative correlation of miR-542-3p with further BMP signaling genes, i.e., SMAD4 and CDH1, was observed. These results indicate that the miRNA selected by us may be a potential negative regulator of BMP7-SMAD4-CDH1 signaling associated with EMT. The different patterns of BMP7, SMAD4, and CDH1 gene expression in ECE, EUE, and the control endometrium observed by us suggests the loss of the endometrial epithelium phenotype in women with endometriosis and demonstrates their involvement in the pathogenesis and pathomechanism of this disease.

Progress on the Role of Estrogen and Progesterone Signaling in Mouse Embryo Implantation and Decidualization

Embryo implantation and decidualization are key steps in establishing a successful pregnancy. Defects in embryo implantation and decidualization can cause a series of adverse chain reactions which can contribute to harmful pregnancy outcomes, such as embryo growth retardation, preeclampsia, miscarriage, premature birth, and so on. Approximately 75% of failed pregnancies are considered to be due to embryo implantation failure or defects. Decidualization, characterized by proliferation and differentiation of uterine stromal cells, is one of the essential conditions for blastocyst implantation, placental formation, and maintenance of pregnancy and is indispensable for the establishment of pregnancy in many species. Embryo implantation and decidualization are closely regulated by estrogen and progesterone secreted by the ovaries. Many cellular events and molecular signaling network pathways are involved in this process. This article reviews the recent advances in the molecular mechanisms of estrogen- and progesterone-regulating uterine receptivity establishment, blastocyst implantation, and decidualization, in order to better understand the underlying molecular mechanisms of hormonal regulation of embryo implantation and to develop new strategies for preventing or treating embryo implantation defects and improving the pregnancy rate of women.