Ineffective endometrial matrix remodeling, a key factor in infertility, impedes embryo implantation in the uterine wall. Our study reveals the cellular and molecular impact of human collagenase-1 administration in mouse uteri, demonstrating enhanced embryo implantation rates. Collagenase-1 promotes remodeling of the endometrial ECM, degrading collagen fibers and proteoglycans. This process releases matrix-bound bioactive factors (e.g., VEGF, decorin), facilitating vascular permeability and angiogenesis. Collagenase-1 elevates embryo implantation regulators, including NK cell infiltration and the key cytokine LIF. Remarkably, uterine tissue maintains structural integrity despite reduced endometrial collagen fiber tension. In-utero collagenase-1 application rescues implantation in heat stress and embryo transfer models, known for low implantation rates. Importantly, ex vivo exposure of human uterine tissue to collagenase-1 induces collagen de-tensioning and VEGF release, mirroring remodeling observed in mice. Our research highlights the potential of collagenases to induce and orchestrate cellular and molecular processes enhancing uterine receptivity for effective embryo implantation. This innovative approach underscores ECM remodeling mechanisms critical for embryo implantation.

Objective: To construct a repetitive implantation failure (RIF)-related competitive endogenous RNA (ceRNA) regulatory network and validate with clinical samples. Methods: RIF-related long non-coding RNA (lncRNA), microRNA (miRNA) and messenger RNA (mRNA) from the high-throughput gene expression omnibus (GEO) database Expression profile data set were obtained to construct a ceRNA regulatory network of lncRNA-miRNA-mRNA. At the same time, weighted gene co-expression network analysis (WGCNA) was used to explore hub genes in the network. This retrospective study collected RIF patients and controls (at least one pregnancy history after assisted conception) who underwent in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) for assisted pregnancy from 2020 to 2021 at the Reproductive Medicine Center of the First Affiliated Hospital of Zhengzhou University. In the endometrial tissue of patients with 1 pregnancy history, real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) was used to verify the mRNA expression levels of RIF-related hub genes, and Western blotting and immunohistochemistry were used to verify protein expression levels of vascular cell adhesion molecule-1 (VCAM1). Results: A RIF-related ceRNA regulatory network consisting of 32 lncRNAs, 31 miRNAs and 88 mRNAs was constructed, and 7 RIF-related hub genes were identified using WGCNA. By intersecting 88 mRNAs and hub genes in the ceRNA network, two RIF-related key genes were obtained, i.e., VCAM1 and interleukin-2 receptor α (interleukin-2 receptor α, IL-2RA). In clinical verification, the ages of the control group and RIF group [M (Q1, Q3)] were 26.50 (25.00, 34.00) and 30.50 (25.75, 35.25) years old, respectively (P>0.05). Compared with the control group, the mRNA [0.30 (0.15, 0.42) vs 0.99 (0.69, 1.34), P=0.001] and protein expression [0.44 (0.16, 1.27) vs 2.39 (1.58, 2.58), P<0.001] of VCAM1 in the endometrium of the RIF group were both reduced. Conclusions: This study uses bioinformatics analysis methods to construct a RIF-related ceRNA regulatory network, and it is confirmed through clinical samples that the expression level of VCAM1 in the endometrial tissue of RIF patients is significantly reduced.
目的： 构建反复种植失败（RIF）相关竞争性内源RNA（ceRNA）调控网络并进行临床样本验证。 方法： 从高通量基因表达数据库（GEO）得到RIF相关的长链非编码RNA（lncRNA）、微小RNA（miRNA）和信使RNA（mRNA）表达谱数据集，构建lncRNA-miRNA-mRNA的ceRNA调控网络。同时利用加权基因共表达网络分析（WGCNA）探索网络中的枢纽基因。回顾性收集2020—2021年于郑州大学第一附属医院生殖医学中心行体外受精（IVF）/卵胞浆内单精子显微注射（ICSI）助孕的RIF患者和对照组（助孕后至少有1次妊娠史）患者的子宫内膜组织，应用实时荧光定量聚合酶链反应（qRT-PCR）验证RIF相关枢纽基因的mRNA表达水平，并应用Western印迹和免疫组化技术验证血管细胞黏附分子-1（VCAM1）的蛋白表达水平。 结果： 构建了由32个lncRNA、31个miRNA和88个mRNA组成的RIF相关ceRNA调控网络，并利用WGCNA鉴定出7个RIF相关枢纽基因。将ceRNA网络中的88个mRNA与枢纽基因取交集得到2个RIF相关关键基因：VCAM1和白细胞介素2受体α（IL-2RA）。临床验证中，对照组和RIF组的年龄［M（Q1，Q3）］分别为26.50（25.00，34.00）和30.50（25.75，35.25）岁（P>0.05）。与对照组相比，RIF组子宫内膜中VCAM1的mRNA［M（Q1，Q3）］［0.30（0.15，0.42）比0.99（0.69，1.34），P=0.001］和蛋白表达水平［M（Q1，Q3）］［0.44（0.16，1.27）比2.39（1.58，2.58），P<0.001］均降低。 结论： 本研究成功构建了RIF相关ceRNA调控网络，并通过临床样本证实RIF患者子宫内膜组织中VCAM1的表达水平降低。.

BACKGROUND: Monoamine oxidases (MAOs) is an enzyme that catalyzes the deamination of monoamines. The current research on this enzyme is focused on its role in neuropsychiatric, neurodevelopmental, and neurodegenerative diseases. Indeed, MAOs with two isoforms, namely, A and B, are located on the outer mitochondrial membrane and are widely distributed in the central nervous system and peripheral tissues. Several reports have described periodic changes in the levels of this enzyme in the human endometrial tissue.
RESULTS: The novel role of MAOs in endometrial receptivity establishment and embryonic development by maintaining monoamine homeostasis was investigated in this study. MAOs activity was observed to be enhanced during the first trimester in both humans and mice under normal conditions. However, under pathological conditions, MAOs activity was reduced and was linked to early pregnancy failure. During the secretory phase, the endometrial stromal cells differentiated into decidual cells with a stronger metabolism of monoamines by MAOs. Excessive monoamine levels cause monoamine imbalance in decidual cells, which results in the activation of the AKT signal, decreased FOXO1 expression, and decidual dysfunction.
CONCLUSIONS: The findings suggest that endometrial receptivity depends on the maintenance of monoamine homeostasis via MAOs activity and that this enzyme participates in embryo implantation and development.

UNASSIGNED: Fibroblast growth factors (FGFs) play a key role in embryo implantation and support endometrial trophoblastic interaction.
UNASSIGNED: The aim of the study was to evaluate the association between FGF-1 (rs34011) gene variety and its serum concentration with repeated implantation failure (RIF).
UNASSIGNED: The design of the study was a cross-sectional study.
UNASSIGNED: Four hundred infertile women with a history of RIF and 400 healthy women undergoing the first in vitro fertilisation-embryo transfer attempt with successful delivery (controls) were enrolled in the study. Genomic DNA was extracted from peripheral blood leucocytes and genotyped by Tetra-Primer Amplification Refractory Mutation System-Polymerase Chain Reaction. Serum FGF-1 concentration was evaluated with enzyme-linked immunosorbent assay.
UNASSIGNED: The ANOVA test was used to analyse the difference between the means of the groups.
UNASSIGNED: In RIF group, the genotype frequencies of the GG, GA and AA were 59%, 33.5% and 7.5%, respectively, whereas in controls were 72.5%, 24% and 3.5%, respectively. The G and A allele frequencies in the RIF group were 75.75% and 24.25%, while in controls were 84.5% and 15.5%, respectively (P < 0.0001). We have also shown that serum FGF-1 concentration in RIF and control groups was 17 ± 3.55 and 23.62 ± 4.91 pg/mL, respectively (P = 0.008). We have also shown that AA genotype is significantly associated with decreased serum FGF-1 concentration in RIF (AA, GA and GG serum levels were 9.55 ± 2.65, 14 ± 3.35 and 22.55 ± 7.26 pg/mL, and in controls were 12.22 ± 2.27, 18.44 ± 5.98 and 26.66 ± 8.29 pg/mL, respectively).
UNASSIGNED: The current study suggests that a significant association between FGF-1 (rs34011) promoter polymorphism and its serum concentration with RIF. The study also suggests that AA genotype is linked to lower FGF-1 serum levels and may play a risk factor for RIF.

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.
CONCLUSIONS: 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.
BACKGROUND: Not applicable.

Extracellular vesicles (EVs) serve as messengers for intercellular communication, yet the precise mechanisms by which recipient cells interpret EV messages remain incompletely understood. In this study, we explored how the origin of EVs, their protein cargo, and the recipient cell type influence the cellular response to EVs within an embryo implantation model. We treated two types of EVs to 6 different recipient cell types and expression of zinc finger protein 81 (ZNF81) gene expression in the recipient cells were quantified using quantitative polymerase chain reaction (qPCR). The proteomic contents of the EV cargos were also analyzed. The results showed that downregulation of the ZNF81 gene was a specific cellular response of receptive endometrial epithelial cells to trophoblast derived EVs. Protein cargo analysis revealed that the proteomic profile of EVs depends on their cell of origin and therefore may affect the recipient cell response to EVs. Furthermore, trophoblastic EVs were found to be specifically enriched with transcription factors such as CTNNB1 (catenin beta-1), HDAC2 (histone deacetylase 2), and NOTCH1 (neurogenic locus notch homolog protein 1), which are known regulators of ZNF81 gene expression. The current study provided compelling evidence supporting the existence of EV specificity, where the characteristics of both the EVs and the recipient cell type collectively contribute to regulating EV target specificity. Additionally, EV protein cargo analysis suggested a potential association between transcription factors and the specific functionality of trophoblastic EVs. This in vitro embryo implantation model and ZNF81 read-out provides a unique platform to study EV specific functionality in natural cell-cell communication.

Objective: This study aimed to assess the relationship between implantation and soluble HLA-G (sHLA-G) expression in cleavage embryo culture medium (ECM) in conjunction with early developmental kinetics determined by time-lapse imaging (TLI). Methods: A retrospective, single-center study was conducted involving 238 embryos from 165 patients who underwent Frozen-thawed embryo transfer (FET) using autologous oocytes, with either single or double embryo transfer. TLI morphokinetic parameters (t2, t3, t4, t5, t6, t7, t8, cc2, s2, cc3, s3) of embryos were analyzed, and sHLA-G levels in D3 ECM were measured using an enzyme-linked immunosorbent assay (ELISA). A hierarchical classification model was developed to categorize embryos into five groups (A, B, C, D, E). The correlation between sHLA-G levels, TLI classification of embryos, and embryo implantation was investigated to establish a non-invasive method for evaluating implantation potential. Multivariate logistic regression analysis was performed to identify potential influencing factors, and receiver operating characteristic (ROC) curves were used to evaluate the predictive value for implantation. Results: Multivariate unconditional logistic regression analysis indicated that TLI parameters t5 and s3 and sHLA-G level in ECM were independent risk factors affecting embryo implantation. The implantation rate decreased from TLI classification A to E. The proposed classification model effectively assessed the implantation potential of embryos. The implantation rate was higher in the sHLA-G positive group compared to the sHLA-G negative group (p < 0.001). The expression of sHLA-G in D3 ECM, combined with the TLI classification model, accurately evaluated the implantation potential of embryos with an AUC of 0.876. Conclusion: The integration of cleavage kinetics and embryonic sHLA-G expression could reliably identify embryos with a high likelihood of successful implantation.

BACKGROUND: Abnormal endometrial blood flow causes a decrease in endometrial receptivity and is considered a relatively independent risk factor for recurrent implantation failure (RIF). This study aimed to explore the potentially functional circRNA-miRNA-mRNA network in RIF, and further explore its mechanism.
METHODS: Datasets were downloaded from the GEO database to identify differentially expressed circRNAs, miRNAs and mRNAs. The circRNA-miRNA-mRNA and PPI networks were constructed using Cytoscape 3.6.0 and the STRING database, the hub genes were identified with the cytoHubba plug-in, and a circRNA-miRNA-hub mRNA regulatory sub-network was constructed. Then, GO and KEGG pathway enrichment analyses of the hub genes were performed to comprehensively analyze the mechanism of hub mRNAs in RIF. Due to the results of circRNAs-miRNAs-hub mRNAs regulatory network, we verified the expression of circRNA_0001721, circRNA_0000714, miR-17-5p, miR-29b-3p, HIF1A and VEGFA in the RIF mouse model by qRT‒PCR and western blotting.
RESULTS: We initially identified 175 DEmRNAs, 48 DEmiRNAs and 56 DEcircRNAs in RIF associated with angiogenesis and constructed a circRNA-miRNA‒mRNA network and PPI network. We further identified six hub genes in the acquired network. Based on these genes, functional enrichment analysis revealed that the HIF-1 signaling pathway plays a vital role in endometrial angiogenesis in RIF. In addition, the interaction networks of circRNA_0001721/miR-17-5p/HIF1A and the circRNA_0000714/miR-29b-3p/VEGFA axis were predicted. In the RIF mouse model, circRNA_0001721, circRNA_0000714, HIF1A and VEGFA were down-regulated, whereas miR-17-5p and miR-29b-3p were up-regulated according to qRT‒PCR and western blotting.
CONCLUSIONS: This study revealed that the HIF-1 signaling pathway plays a vital role in endometrial angiogenesis in RIF. The circRNA_0001721/miR-17-5p/HIF1A and circRNA_0000714/miR-29b-3p/VEGFA axes might play a role in the pathogenesis of endometrial angiogenesis in RIF.

UNASSIGNED: This study investigated whether RNA-Seq-based endometrial receptivity test (rsERT)-which provides precision for the optimal hour of the window of implantation (WOI)-can improve clinical outcomes of frozen embryo transfer (FET) cycles in patients with a history of repeated implantation failure (RIF).
UNASSIGNED: Patients with a history of RIF who received at least one autologous high-quality blastocyst during the subsequent FET cycle were retrospectively enrolled and divided into two groups: rsERT and FET, comprising patients who underwent rsERT-guided pET (n=115) and standard FET without rsERT (n=272), respectively.
UNASSIGNED: In the rsERT group, 39.1% (45/115) of patients were receptive. rsERT patients showed a higher probability of achieving both positive human chorionic gonadotropin (63.5% vs. 51.5%, P=0.03) and clinical pregnancy (54.8% vs. 38.6%, P=0.003) rates. In subgroup analysis, rsERT patients with non-receptive results had higher clinical pregnancy rates than patients undergoing FET (58.6% vs. 38.6%, P=0.003). rsERT patients with receptive results guided by rsERT with a precise WOI time had higher, although non-significant, clinical pregnancy rates (48.9% vs. 38.6%, P=0.192) than patients who underwent standard-time FET.
UNASSIGNED: Hourly precise rsERT can significantly improve the probability of achieving clinical pregnancy in patients with RIF, especially in those with non-receptive rsERT results.

The reproductive efficiency of dromedary camels is hindered by challenges such as early embryonic mortality, which may be attributed to a lack of synchronization between conceptus signalling and uterine receptivity. Understanding the intricate biological processes involved in feto-maternal interactions during implantation is crucial to address these limitations. Osteopontin (OPN) is a protein involved in cell signalling and adhesion, playing a crucial role in embryonic implantation. Previous studies have shown the presence of OPN in the uterine endometrium of various mammalian species including dromedary camels. However, the expression pattern of OPN in dromedary conceptuses remains unexplored. Thus, the current study aimed, for the first time, to investigate the temporospatial expression of OPN in dromedary conceptuses during the peri-implantation period at Days 8, 10, and 12 of pregnancy. Twelve conceptuses were recovered non-surgically from pregnant females on Days 8, 10, 12 of pregnancy. Quantitative real-time PCR (qrt-PCR), immunohistochemistry (IHC), and immunofluorescence (IF) were employed for analysis of the expression of OPN mRNA and protein. The results revealed significant increases in both OPN mRNA and protein expression started on Day 10 and peaked at Day 12 of pregnancy. Immuno-localization confirmed the presence of OPN protein in the trophectoderm and endoderm of dromedary conceptuses. In conclusion, the expression and localization of OPN during the peri-implantation period in dromedary conceptuses imply its involvement as a crucial reproductive factor and its upregulation during this period, with a pronounced increase close to attachment time (Day 12 of pregnancy) further supports its role in embryo adhesion, implantation, and placentation.