MiR-143 and rat embryo implantation

Uterine fluid microRNAs in repeated implantation failure

Recurrent implantation failure (RIF) is a significant obstacle in assisted reproductive procedures, primarily because of compromised receptivity. As such, there is a need for a dependable and accurate clinical test to evaluate endometrial receptiveness, particularly during embryo transfer. MicroRNAs (miRNAs) have diverse functions in the processes of implantation and pregnancy. Dysregulation of miRNAs results in reproductive diseases such as recurrent implantation failure (RIF). The endometrium secretes several microRNAs (miRNAs) during the implantation period, which could potentially indicate whether the endometrium is suitable for in vitro fertilization (IVF). The goal of this review is to examine endometrial miRNAs as noninvasive biomarkers that successfully predict endometrium receptivity in RIF.

Effect of miR-143-3p from Extracellular Vesicles of Porcine Uterine Luminal Fluid on Porcine Trophoblast Cells

Extracellular vesicles (EVs) in uterine luminal fluid (ULF) can reportedly affect the proliferation and migration function of porcine trophoblast cells (PTr2 cells) by mediating the maternal-fetal exchange of information. miR-143-3p is considered a crucial miRNA in early pregnancy in mammals; however, little is currently known about how it regulates the function of PTr2 cells. This study aimed to investigate the effects of ssc-miR-143-3p in ULF-EVs on the function of PTr2 cells during porcine embryo implantation. The uptake of ULF-EVs by PTr2 cells was confirmed, which significantly increased the expression of ssc-miR-143-3p. Ssc-miR-143-3p was found to facilitate the proliferation and migration of PTr2 cells in the CCK-8, EdU and wound-closure assays, while the opposite findings were observed after the knockdown of ssc-miR-143-3p. Bioinformatics analysis and the luciferase reporter assay showed that glycerol-3 phosphate dehydrogenase 2 (GDP2) was directly targeted by miR-143-3p. Inhibition of miR-143-3p was validated in mice to inhibit embryo implantation. In summary, ssc-miR-143-3p in ULF-EVs affects the proliferation and migration of PTr2 cells by mediating GPD2, thereby affecting embryo implantation.

Role of endometrial microRNAs in repeated implantation failure (mini-review)

MicroRNAs (miRNAs) play various roles in the implantation and pregnancy process. Abnormal regulation of miRNAs leads to reproductive disorders such as repeated implantation failure (RIF). During the window of implantation, different miRNAs are released from the endometrium, which can potentially reflect the status of the endometrium for in vitro fertilization (IVF). The focus of this review is to determine whether endometrial miRNAs may be utilized as noninvasive biomarkers to predict the ability of endometrium to implant and provide live birth during IVF cycles. The levels of certain miRNAs in the endometrium have been linked to implantation potential and pregnancy outcomes in previous studies. Endometrial miRNAs could be employed as non-invasive biomarkers in the assisted reproductive technology (ART) cycle to determine the optimal time for implantation. Few human studies have evaluated the association between ART outcomes and endometrial miRNAs in RIF patients. This review may pave the way for more miRNA transcriptomic studies on human endometrium and introduce a specific miRNA profile as a multivariable prediction model for choosing the optimal time in the IVF cycle.

Differential Expression Pattern of Goat Uterine Fluids Extracellular Vesicles miRNAs during Peri-Implantation

Early pregnancy failure occurs when a mature embryo attaches to an unreceptive endometrium. During the formation of a receptive endometrium, extracellular vesicles (EVs) of the uterine fluids (UFs) deliver regulatory molecules such as small RNAs to mediate intrauterine communication between the embryo and the endometrium. However, profiling of small RNAs in goat UFs’ EVs during pregnancy recognition (day 16) has not been carried out. In this study, EVs were isolated from UFs on day 16 of the estrous cycle or gestation. They were isolated by Optiprep™ Density G radient (ODG) and verified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting. Immunostaining demonstrated that CD63 was present both in the endometrial epithelium and glandular epithelium, and stain intensity was greater in the pregnant endometrium compared to the non-pregnant endometrium. Small RNA sequencing revealed that UFs’ EVs contained numerous sRNA families and a total of 106 differentially expressed miRNAs (DEMs). Additionally, 1867 target genes of the DEMs were obtained, and miRNA–mRNA interaction networks were constructed. GO and KEGG analysis showed that miRNAs were significantly associated with the formation of a receptive endometrium and embryo implantation. In addition, the fluorescence in situ hybridization assay (FISH) showed that chi-miR-451-5p was mainly expressed in stromal cells of the endometrium and a higher level was detected in the endometrial luminal epithelium in pregnant states. Moreover, the dual-luciferase reporter assay showed that chi-miR-451-5p directly binds to PSMB8 and may play an important role in the formation of a receptive endometrium and embryo implantation. In conclusion, these results reveal that UFs’ EVs contain various small RNAs that may be vital in the formation of a receptive endometrium and embryo implantation.

Murine Blastocysts Release Mature MicroRNAs Into Culture Media That Reflect Developmental Status

Extracellular microRNA (miRNA) sequences derived from the pre-implantation embryo have attracted interest for their possible contributions to the ongoing embryonic-uterine milieu, as well as their potential for use as accessible biomarkers indicative of embryonic health. Spent culture media microdroplets used to culture late-stage E4.0 murine blastocysts were screened for 641 mature miRNA sequences using a reverse transcription-quantitative polymerase chain reaction-based array. We report here 39 miRNAs exclusively detected in the conditioned media, including the implantation-relevant miR-126a-3p, miR-101a, miR-143, and miR-320, in addition to members of the highly expressed embryonic miR-125 and miR-290 families. Based on these results, an miRNA panel was assembled comprising five members of the miR-290 family (miR-291-295) and five conserved sequences with significance to the embryonic secretome (miR-20a, miR-30c, miR-142-3p, miR-191, and miR-320). Panel profiling of developing embryo cohort lysates and accompanying conditioned media microdroplets revealed extensive similarities in relative quantities of miRNAs and, as a biomarker proof of concept, enabled distinction between media conditioned with differently staged embryos (zygote, 4-cell, and blastocyst). When used to assess media conditioned with embryos of varying degrees of degeneration, the panel revealed increases in all extracellular panel sequences, suggesting cell death is an influential and identifiable factor detectable by this assessment. In situ hybridization of three panel sequences (miR-30c, miR-294, and miR-295) in late-stage blastocysts revealed primarily inner cell mass expression with a significant presence of miR-294 throughout the blastocyst cavity. Furthermore, extracellular miR-290 sequences responded significantly to high centrifugal force, suggesting a substantial fraction of these sequences may exist within a vesicle such as an exosome, microvesicle, or apoptotic bleb. Together, these results support the use of extracellular miRNA to assess embryonic health and enable development of a non-invasive viability diagnostic tool for clinical use.

Essential Role of CRIM1 on Endometrial Receptivity in Goat

In domestic ruminants, endometrial receptivity is related to successful pregnancy and economic efficiency. Despite several molecules having been reported in the past regarding endometrial receptivity regulation, much regarding the mechanism of endometrial receptivity regulation remains unknown due to the complex nature of the trait. In this work, we demonstrated that the cysteine-rich transmembrane bone morphogenetic protein (BMP) regulator 1 (CRIM1) served as a novel regulator in the regulation of goat endometrial receptivity in vitro. Our results showed that hormones and IFN-τ increased the expression of CRIM1 in goat endometrial epithelial cells (EECs). Knockdown of CRIM1 via specific shRNA hindered cell proliferation, cell adhesion and prostaglandins (PGs) secretion and thus derailed normal endometrial receptivity. We further confirmed that receptivity defect phenotypes due to CRIM1 interference were restored by ATG7 overexpression in EECs while a loss of ATG7 further impaired receptivity phenotypes. Moreover, our results showed that changing the expression of ATG7 affected the reactive oxygen species (ROS) production. Moreover, mR-143-5p was shown to be a potential upstream factor of CRIM1-regulated endometrial receptivity in EECs. Overall, these results suggest that CRIM1, as the downstream target of miR-143-5p, has effects on ATG7-dependent autophagy, regulating cell proliferation, cell adhesion and PG secretion, and provides a new target for the diagnosis and treatment of early pregnancy failure and for improving the success rates of artificial reproduction.

The Role of MicroRNAs in Mammalian Fertility: From Gametogenesis to Embryo Implantation

The genetic codes inscribed during two key developmental processes, namely gametogenesis and embryogenesis, are believed to determine subsequent development and survival of adult life. Once the embryo is formed, its further development mainly depends on its intrinsic characteristics, maternal environment (the endometrial receptivity), and the embryo–maternal interactions established during each phase of development. These developmental processes are under strict genetic regulation that could be manifested temporally and spatially depending on the physiological and developmental status of the cell. MicroRNAs (miRNAs), one of the small non-coding classes of RNAs, approximately 19–22 nucleotides in length, are one of the candidates for post-transcriptional developmental regulators. These tiny non-coding RNAs are expressed in ovarian tissue, granulosa cells, testis, oocytes, follicular fluid, and embryos and are implicated in diverse biological processes such as cell-to-cell communication. Moreover, accumulated evidences have also highlighted that miRNAs can be released into the extracellular environment through different mechanisms facilitating intercellular communication. Therefore, understanding miRNAs mediated regulatory mechanisms during gametogenesis and embryogenesis provides further insights about the molecular mechanisms underlying oocyte/sperm formation, early embryo development, and implantation. Thus, this review highlights the role of miRNAs in mammalian gametogenesis and embryogenesis and summarizes recent findings about miRNA-mediated post-transcriptional regulatory mechanisms occurring during early mammalian development.

Selective estrogen receptor modulator ormeloxifene suppresses embryo implantation via inducing miR-140 and targeting insulin-like growth factor 1 receptor in rat uterus

Ormeloxifene, the non-steroidal SERM contraceptive, inhibits endometrial receptivity and embryo implantation via countering nidatory estrogen. However, the molecular mechanism of ormeloxifene action responsible for its contraceptive efficacy still remains unclear. Herein, we aimed to identify the miRNAs modulated under the influence of ormeloxifene and to explore their role in endometrial receptivity and embryo implantation. By doing microRNA sequencing analysis, a total of 168 miRNAs were found to be differentially expressed in uterine tissue of ormeloxifene-treated rats, on day 5 (10:00 h) of pregnancy i.e. peri-implantation period. Out of differentially expressed miRNAs, miR-140 expression was found to be elevated in ormeloxifene administered groups and was selected for detailed investigation. In-vivo gain-of-function of miR-140 resulted in a significant reduction of implantation sites indicating its role in embryo implantation. The experiment on delayed implantation showed that estradiol caused down-regulation of miR-140. It also suppressed the attachment and outgrowth of BeWo spheroids to RL95-2 endometrial cells. In transwell migration assay, miR-140 was found to be involved in suppression of migration and invasion of endometrial epithelial cells. The ormeloxifene treatment caused up-regulation of miR-140 along with down-regulated expression of its target IGF1R in endometrial epithelial and stromal cells which also led to the suppression of downstream effectors integrin β3 and FAK. In mimic miR-140 receiving horn, the reduced expression of IGF1R was observed along with suppressed downstream integrin β3 and FAK similar to that observed in uteri of ormeloxifene- treated rats. Taken together, these findings suggest that ormeloxifene-induced inhibition of embryo implantation occurs via inducing miR-140 and altering its target IGF1R in rat uterus.

MiR-125b regulates endometrial receptivity by targeting MMP26 in women undergoing IVF-ET with elevated progesterone on HCG priming day

On the women undergoing IVF-ET with elevated progesterone on human chorionic gonadotrophin priming, the assisted reproductive technology outcome is poor. But, due to the unknown mechanism of this process, no effective method has been found to overcome this difficulty. Here, we investigated the roles of miR-125b and its target gene, MMP26, in endometrial receptivity (ER) in these women. The expression of miR-125b was significantly up-regulated in EECs in women with elevated progesterone during the window of implantation, and it showed a progesterone-dependent effect in vitro. Similarly, the expression of miR-125b was significantly up-regulated in the preimplantation period, and was down-regulated in the implantation period and the post-implantation period in mouse EECs. In addition, miR-125b showed a greater decrease at implantation sites than it did at interimplantation sites. The luciferase report assay demonstrated that MMP26 is a target gene of miR-125b. And the expression profile of MMP26 showed an inverse relationship with miR-125b in vivo and in vitro. Overexpression of miR-125b in human EECs inhibited cell migration and invasion. Gain-of-function of miR-125b induced a significant decrease in the number of implantation sites. In conclusion, these data shed new light on how miR-125b triggers ER decline through the regulation of MMP26 function.

MicroRNA and Embryo Implantation

PROBLEM

In mammals, implantation involves interactions between an activated blastocyst and a receptive endometrium. There are controversies on the role of microRNAs in preimplantation embryo development. The actions of endometrial microRNAs on implantation are beginning to be understood.

METHOD OF STUDY

Review of literature on microRNAs in preimplantation embryos and endometrium.

RESULTS

Emerging evidence suggests a role of microRNAs in blastocyst activation and implantation. Differential expression of microRNAs is found between receptive and non-receptive endometria. Members of the let-7, miR-200, miR-30 families, and the miR-17-92 clusters are more commonly found to be associated with endometrial receptivity. Experimental studies show that the targets of the differentially expressed microRNAs affect endometrial receptivity, decidualization, and embryo implantation. Free and exosome/microvesicle containing microRNAs have been detected in human and ovine uterine luminal fluid (ULF). They may serve as mediators of embryo-endometrium dialog. Some observations suggest that the microRNAs in ULF may be used as biomarkers in infertility treatment.

CONCLUSION

MicroRNAs in endometrium and blastocysts are involved in the implantation process.

Preimplantation embryo-secreted factors modulate maternal gene expression in rat uterus

In mammalian reproduction, embryo implantation into the uterus is spatiotemporally regulated by a complex process triggered by a number of factors. Although previous studies have suggested that uterine receptivity is mediated by blastocyst-derived factors, specific functions of embryos remain to be defined during preimplantation. Therefore, the present study was conducted to identify the maternal genes regulated by embryo-secreted factors in the rat uterus. RNA-sequencing (RNA-seq) data revealed that 10 genes are up-regulated in the delayed implantation uterus compared with the pseudopregnancy uterus. The RNA-seq results were further verified by real-time quantitative polymerase chain reaction. Sulf1 expression is significantly (P < 0.05) induced in the delayed implantation uterus, although Areg, Calca, Fxyd4 and Lamc3 show a definite but non-statistically significant increase in their expression levels. During early pregnancy, the levels of Areg, Calca, Fxyd4, Lamc3 and Sulf1 expression at 3.5 days post coitus (dpc) are significantly (P < 0.05) higher than those at 1.5 dpc. Treatment with embryo-conditioned media revealed that Lamc3 and Sulf1 are up-regulated compared with the other genes studied. Thus, embryo-derived factors regulate maternal gene expression, with Lamc3 and Sulf1 possibly being suitable markers for a response study of embryo-secreted factors to improve our understanding of embryo-maternal communication.

MicroRNA-181a is involved in the regulation of human endometrial stromal cell decidualization by inhibiting Krüppel-like factor 12

BACKGROUND

The transformation of endometrium into decidua is essential for normal implantation of the blastocyst. However, the post-transcriptional regulation and the miRNAs involved in decidualization remain poorly understood. Here, we examined microRNA-181a (miR-181a) expression in decidualized human endometrial stromal cell (hESC). In addition, we investigated the functional effect of miR-181a on hESC decidualization in vitro.

METHODS

Quantitative real-time PCR (qRT-PCR) was used to detect the profile of miR-181a in decidualized hESC. qRT-PCR, enzyme-linked fluorescent assay, and immunofluorescence assay were performed to investigate decidualization marker genes' expression after enhancing or inhibition of miR-181a expression in hESC. Luciferase reporter assay, western blotting, qRT-PCR, and immunofluorescence assay were carried out to identify the relationship between miR-181a and Krüppel-like factor 12 (KLF12).

RESULTS

miR-181a expression levels increased dramatically in hESC treated with 8-Br-cAMP and MPA. Increased miR-181a expression promoted hESC decidualization-related gene expression and morphological transformation; conversely, inhibition of miR-181a expression compromised hESC decidualization in vitro. Further analysis confirmed that miR-181a interacted with the 3' untranslated region of the transcription factor KLF12 and down-regulated KLF12 at the transcriptional and translational levels. KLF12 overexpression abolished miR-181a-induced decidualization.

CONCLUSIONS

Our findings suggest that miR-181a plays a functionally important role in human endometrial stromal cell decidualization in vitro by inhibiting KLF12.