Varied cellular abnormalities in thin vs. normal endometrium in recurrent implantation failure by single-cell transcriptomics.

BACKGROUND: Reduced endometrium thickness and receptivity are two important reasons for recurrent implantation failure (RIF). In order to elucidate differences between these two types of endometrial defects in terms of molecular signatures, cellular interactions, and structural changes, we systematically investigated the single-cell transcriptomic atlas across three distinct groups: RIF patients with thin endometrium (≤ 6 mm, TE-RIF), RIF patients with normal endometrium thickness (≥ 8 mm, NE-RIF), and fertile individuals (Control). METHODS: The late proliferative and mid-secretory phases of the endometrium were collected from three individuals in the TE-RIF group, two in the NE-RIF group, and three in the control group. The study employed a combination of advanced techniques. Single-cell RNA sequencing (scRNA-seq) was utilized to capture comprehensive transcriptomic profiles at the single-cell level, providing insights into gene expression patterns within specific cell types. Scanning and transmission electron microscopy were employed to visualize ultrastructural details of the endometrial tissue, while hematoxylin and eosin staining facilitated the examination of tissue morphology and cellular composition. Immunohistochemistry techniques were also applied to detect and localize specific protein markers relevant to endometrial receptivity and function. RESULTS: Through comparative analysis of differentially expressed genes among these groups and KEGG pathway analysis, the TE-RIF group exhibited notable dysregulations in the TNF and MAPK signaling pathways, which are pivotal in stromal cell growth and endometrial receptivity. Conversely, in the NE-RIF group, disturbances in energy metabolism emerged as a primary contributor to reduced endometrial receptivity. Additionally, using CellPhoneDB for intercellular communication analysis revealed aberrant interactions between epithelial and stromal cells, impacting endometrial receptivity specifically in the TE-RIF group. CONCLUSION: Overall, our findings provide valuable insights into the heterogeneous molecular pathways and cellular interactions associated with RIF in different endometrial conditions. These insights may pave the way for targeted therapeutic interventions aimed at improving endometrial receptivity and enhancing reproductive outcomes in patients undergoing ART. Further research is warranted to validate these findings and translate them into clinical applications for personalized fertility treatments. TRIAL REGISTRATION: Not applicable.

Single-cell transcriptome analysis uncovers the molecular and cellular characteristics of thin endometrium.

Infertility is a social and medical problem around the world and the incidence continues to rise. Thin endometrium (TE) is a great challenge of infertility treatment, even by in vitro fertilization and embryo transfer. It is widely believed that TE impairs endometrium receptivity. However, only a few studies have explained the molecular mechanism. Herein, in order to reveal the possible mechanism, we sampled endometrium from a TE patient and a control volunteer and got a transcriptomic atlas of 18 775 individual cells which was constructed using single-cell RNA sequencing, and seven cell types have been identified. The cells were acquired during proliferative and secretory phases, respectively. The proportion of epithelial cells and stromal cells showed a significant difference between the TE group and the control group. In addition, differential expressed genes (DEGs) in diverse cell types were revealed, the enriched pathways of DEGs were found closely related to the protein synthesis in TE of both proliferative and secretory phases. Some DEGs can influence cell-type ratio and impaired endometrial receptivity in TE. Furthermore, divergent expression of estrogen receptors 1 and progesterone receptors in stromal and epithelial cells were compared in the TE sample from the control. The cellular and molecular heterogeneity found in this study provided valuable information for disclosing the mechanisms of impaired receptivity in TE.

Methyl 3,4-dihydroxybenzoate alleviates oxidative damage in granulosa cells by activating Nrf2 antioxidant pathway.

Oxidative damage induced granulosa cells (GCs) apoptosis was considered as a significant cause of compromised follicle quality, antioxidants therapy has emerged as a potential method for improving endometriosis pregnancy outcomes. Here, we found that GCs from endometriosis patients show increased oxidative stress level. Methyl 3,4-dihydroxybenzoate (MDHB), a small molecule compound that is extracted from natural plants, reversed tert-butyl hydroperoxide (TBHP) induced GCs oxidative damage. Therefore, the aim of this study was to assess the protective effect of MDHB for GCs and its potential mechanisms. TUNEL staining and immunoblotting of cleaved caspase-3/7/9 showed MDHB attenuated TBHP induced GCs apoptosis. Mechanistically, MDHB treatment decreased cellular and mitochondria ROS production, improved the mitochondrial function by rescuing the mitochondrial membrane potential (MMP) and ATP production. Meanwhile, MDHB protein upregulated the expression of vital antioxidant transcriptional factor Nrf2 and antioxidant enzymes SOD1, NQO1 and GCLC to inhibited oxidative stress state, further beneficial to oocytes and embryos quality. Therefore, MDHB may represent a potential drug candidate in protecting granulosa cells in endometriosis, which can improve pregnancy outcomes for endometriosis-associated infertility.

Three-dimensional architecture of granulosa cell derived from oocyte cumulus complex, revealed by FIB-SEM.

The oocyte cumulus complex is mainly composed of an oocyte, the perivitelline space, zona pellucida and numerous granulosa cells. The cumulus granulosa cells (cGCs) provide a particularly important microenvironment for oocyte development, regulating its growth, maturation and meiosis. In this study, we studied the internal structures and cell-to-cell connections of mouse cGCs using focused ion beam scanning electron microscopy (FIB-SEM). We reconstructed three-dimensional models to display characteristic connections between the oocyte and cGCs, and to illustrate various main organelles in cGCs together with their interaction relationship. A special form of cilium identified in granulosa cell was never reported in previous literature.

Truncating PICK1 Variant Identified in Azoospermia Affected Mitochondrial Dysfunction in Knockout Mice.

OBJECTIVE: The protein interacting with C kinase 1 (PICK1) plays a critical role in vesicle trafficking, and its deficiency in sperm cells results in abnormal vesicle trafficking from Golgi to acrosome, which eventually disrupts acrosome formation and leads to male infertility. METHODS: An azoospermia sample was filtered, and the laboratory detection and clinical phenotype indicated typical azoospermia in the patient. We sequenced all of the exons in the PICK1 gene and found that there was a novel homozygous variant in the PICK1 gene, c.364delA (p.Lys122SerfsX8), and this protein structure truncating variant seriously affected the biological function. Then we constructed a PICK1 knockout mouse model using clustered regularly interspaced short palindromic repeat cutting technology (CRISPRc). RESULTS: The sperm from PICK1 knockout mice showed acrosome and nucleus abnormalities, as well as dysfunctional mitochondrial sheath formation. Both the total sperm and motility sperm counts were decreased in the PICK1 knockout mice compared to wild-type mice. Moreover, the mitochondrial dysfunction was verified in the mice. These defects in the male PICK1 knockout mice may have eventually led to complete infertility. CONCLUSION: The c.364delA novel variant in the PICK1 gene associated with clinical infertility, and pathogenic variants in the PICK1 may cause azoospermia or asthenospermia by impairing mitochondrial function in both mice and humans.

Identification and characterization of novel compound heterozygous variants in FSHR causing primary ovarian insufficiency with resistant ovary syndrome.

Primary ovarian insufficiency (POI) is among the foremost causes of women infertility due to premature partial or total loss of ovarian function. Resistant ovary syndrome (ROS) is a subtype of POI manifested as normal ovarian reserve but insensitive to gonadotropin stimulation. Inactivating variants of follicle-stimulating hormone receptor (FSHR), a class A G-protein coupled receptor, have been associated with POI and are inherited via an autosomal recessive pattern. In this study, we investigated the genetic causes of a primary infertility patient manifested as POI with ROS, and elucidated the structural and functional impact of variants of uncertain significance. Next-generation sequencing (NGS) combined with Sanger sequencing revealed novel compound heterozygous FSHR variants: c.1384G>C/p.Ala462Pro and c.1862C>T/p.Ala621Val, inherited from her father and mother, respectively. The two altered amino acid sequences, localized in the third and seventh transmembrane helix of FSHR, were predicted as deleterious by in silico prediction. In vitro experiments revealed that the p.Ala462Pro variant resulted in barely detectable levels of intracellular signaling both in cAMP-dependent CRE-reporter activity and ERK activation and displayed a severely reduced plasma membrane receptor expression. In contrast, the p.Ala621Val variant resulted in partial loss of receptor activation without disruption of cell surface expression. In conclusion, two unreported inactivating FSHR variants potentially responsible for POI with ROS were first identified. This study expands the current phenotypic and genotypic spectrum of POI.

Thinning or Opening: A Randomized Sibling-Embryo Pilot Trial on the Efficacy of Two Laser-Assisted Hatching Modes During the Extended Culture of Highly Fragmented Cleavage Embryos.

A randomized sibling-embryo pilot trial investigated whether two ways of laser-assisted hatching result in different blastulation and clinical outcomes after extended in vitro culture process of highly fragmented day-3 cleavage embryos. From 92 couples, a total of 315 highly fragmented day-3 embryos (the fragmentation >25%) were recruited and randomized into laser-assisted zona thinning (LAT, n=157) and opening (LAO, n=158) groups, and then underwent a blastocyst culture in vitro. The main endpoint measurements including blastocyst formation and grading as well as the clinical pregnancy after blastocyst transfer were obtained during the treatment procedure of in vitro fertilization and embryo transfer, and then analyzed with generalized estimating equation (GEE) and/or time-to blastocyst analysis models. A total of 166 day-3 embryos developed into blastocyst stage (52.70%), of which 97 were viable blastocysts (30.79%), and 42 top-quality ones (13.33%). LAT did not have any inferior or superior to LAO in the endpoints of either total, viable, top-quality or hatched blastocyst formation, with the ORs (95%CI) from GEE model as 0.89 (0.55-1.45), 0.71 (0.42-1.21), 1.12 (0.56-2.25) and 0.68 (0.42-1.12) respectively for LAT treatment. And the time-to-blastocyst analysis showed a similar result. Additionally, no difference in clinical outcomes after blastocyst transfer was found between the two groups. The author concluded that when applying the LAHs during the extended culture of highly fragmented embryos, both LAT and LAO can generate a promising clinical outcome, and the LAT operation be equivalent to the LAO. Future well-designed, multiple-center, larger-sample investigations are required to ascertain above conclusion.

Iron overload compromises preimplantation mouse embryo development.

We and others have previously shown that abnormal pelvic environment plays an important role in the unexplained infertility of endometriosis. However, whether iron overload caused by ectopic periodic bleeding found in patients with endometriosis participates in endometriosis-associated reproductive failure is unknown. This study aimed to investigate effects of iron at level relevant to pelvic iron overload on the development of preimplantation mouse embryo. Two-cell embryos were collected, and cultured to blastocysts in G1/G2 medium supplemented with iron alone or in combination with iron chelator. The development rates, ATP level, mitochondrial membrane potential (MMP), reactive oxygen species level (ROS), and apoptotic and ferroptotic indices were compared between control and iron treatments across each specific developmental stage. Prolonged exposure to iron remarkably impaired early embryo development in vitro by hampering blastocyst formation (P < 0.001), which could be partly restored by iron chelator (P < 0.001). The arrest of embryo development was linked with iron-initiated mitochondrial dysfunction with reduction of ATP generation and MMP (P < 0.05 and P < 0.001, respectively). Impaired mitochondria altered ROS accumulation post-iron exposure at morula stage and blastocyst stage (P < 0.05). Moreover, Iron-exposed blastocyst stage embryos showed higher apoptotic and ferroptotic rates (P < 0.001 and P < 0.05, respectively). Our results highlight that pathologically relevant level of iron compromises preimplantation mouse embryo development by disrupting mitochondrial function and triggering both apoptosis and ferroptosis, which implicates that excess iron found in peritoneal fluid of women with endometriosis likely participates in endometriosis-associated reproductive failure.

Iron overload in endometriosis peritoneal fluid induces early embryo ferroptosis mediated by HMOX1.

Endometriosis is one of the most common disorders that causes infertility in women. Iron is overloaded in endometriosis peritoneal fluid (PF), with harmful effects on early embryo development. However, the mechanism by which endometriosis peritoneal fluid affects embryonic development remains unclear. Hence, this study investigated the effect of iron overload on mouse embryos and elucidated the molecular mechanism. Iron overload in endometriosis PF disrupted blastocyst formation, decreased GPX4 expression and induced lipid peroxidation, suggesting that iron overload causes embryotoxicity and induces ferroptosis. Moreover, mitochondrial damage occurs in iron overload-treated embryos, presenting as decreased ATP levels, increased ROS levels and MMP hyperpolarization. The cytotoxicity of iron overload is attenuated by the ferroptosis inhibitor Fer-1. Furthermore, Smart-seq analysis revealed that HMOX1 is upregulated in embryo ferroptosis and that HMOX1 suppresses ferroptosis by maintaining mitochondrial function. This study provides new insight into the mechanism of endometriosis infertility and a potential target for future endometriosis infertility treatment efforts.

Islet-cell autoantigen 69 accelerates liver regeneration by downregulating Tgfbr1 and attenuating Tgfß signaling in mice.

Regeneration is a unique defense mechanism of liver tissue in response to functional cell loss induced by toxic chemicals or surgical resection. In this study, we found that Islet-cell autoantigen 69 (Ica69) accelerates liver regeneration in mice. Following 70% partial hepatectomy, both Ica69 mRNA and protein are significantly upregulated in mouse hepatocytes at the early stage of liver regeneration. Compared with the wild-type mice, Ica69-deficient mice have more severe liver injury, delayed liver regeneration, and high surgical accidental mortality following hepatectomy. Mechanistically, Ica69 interacts with Pick1 protein to regulate Tgfbr1 protein expression and Tgfß-induced Smad2 phosphorylation. Our findings suggest that Ica69 in liver tissue is a new potential target for promoting liver regeneration.