Non-invasive Embryo Assessment: Altered Individual Protein Profile in Spent Culture Media from Embryos Transferred at Day 5

Quantitative Proteomics and Metabolomics of Culture Medium from Single Human Embryo Reveal Embryo Quality-Related Multiomics Biomarkers

An effective tool to assess embryo quality in the assisted reproduction clinical practice will enhance successful implantation rates and mitigate high risks of multiple pregnancies. Potential biomarkers secreted into culture medium (CM) during embryo development enable rapid and noninvasive methods of assessing embryo quality. However, small volumes, low biomolecule concentrations, and impurity interference collectively preclude the identification of quality-related biomarkers in single blastocyst CM. Here, we developed a noninvasive trace multiomics approach to screen for potential markers in individual human blastocyst CM. We collected 84 CM samples and divided them into high-quality (HQ) and low-quality (LQ) groups. We evaluated the differentially expressed proteins (DEPs) and metabolites (DEMs) in HQ and LQ CM. A total of 504 proteins and 189 metabolites were detected in individual blastocyst CM. Moreover, 9 DEPs and 32 DEMs were identified in different quality embryo CM. We also categorized HQ embryos into positive implantation (PI) and negative implantation (NI) groups based on ultrasound findings on day 28. We identified 41 DEPs and 4 DEMs associated with clinical implantation outcomes in morphologically HQ embryos using a multiomics analysis approach. This study provides a noninvasive multiomics analysis technique and identifies potential biomarkers for clinical embryo developmental quality assessment.

How should the best human embryo in vitro be? Current and future challenges for embryo selection

In-vitro fertilization (IVF) aims at overcoming the causes of infertility and lead to a healthy live birth. To maximize IVF efficiency, it is critical to identify and transfer the most competent embryo within a cohort produced by a couple during a cycle. Conventional static embryo morphological assessment involves sequential observations under a light microscope at specific timepoints. The introduction of time-lapse technology enhanced morphological evaluation via the continuous monitoring of embryo preimplantation in vitro development, thereby unveiling features otherwise undetectable via multiple static assessments. Although an association exists, blastocyst morphology poorly predicts chromosomal competence. In fact, the only reliable approach currently available to diagnose the embryonic karyotype is trophectoderm biopsy and comprehensive chromosome testing to assess non-mosaic aneuploidies, namely preimplantation genetic testing for aneuploidies (PGT-A). Lately, the focus is shifting towards the fine-tuning of non-invasive technologies, such as "omic" analyses of waste products of IVF (e.g., spent culture media) and/or artificial intelligence-powered morphologic/morphodynamic evaluations. This review summarizes the main tools currently available to assess (or predict) embryo developmental, chromosomal, and reproductive competence, their strengths, the limitations, and the most probable future challenges.

Maternal and embryonic signals cause functional differentiation of luminal epithelial cells and receptivity establishment

Embryo implantation requires temporospatial maternal-embryonic dialog. Using single-cell RNA sequencing for the uterus from 2.5 to 4.5 days post-coitum (DPC) and bulk sequencing for the corresponding embryos of 3.5 and 4.0 DPC pregnant mice, we found that estrogen-responsive luminal epithelial cells (EECs) functionally differentiated into adhesive epithelial cells (AECs) and supporting epithelial cells (SECs), promoted by progesterone. Along with maternal signals, embryonic Pdgfa and Efna3/4 signaling activated AECs and SECs, respectively, enhancing the attachment of embryos to the endometrium and furthering embryo development. This differentiation process was largely conserved between humans and mice. Notably, the developmental defects of SOX9-positive human endometrial epithelial cells (similar to mouse EEC) were related to thin endometrium, whereas functional defects of SEC-similar unciliated epithelial cells were related to recurrent implantation failure (RIF). Our findings provide insights into endometrial luminal epithelial cell development directed by maternal and embryonic signaling, which is crucial for endometrial receptivity.

Neutrophil depletion in the pre-implantation phase impairs pregnancy index, placenta and fetus development

Maternal neutrophils cells are players in gestational tolerance and fetus delivery. Nonetheless, their actions in each phase of the pregnancy are unknown. We here investigated the role of maternal neutrophil depletion before the blastocyst implantation phase and outcomes in the pregnancy index, placenta, and fetus development. Neutrophils were pharmacologically depleted by i.p. injection of anti-Gr1 (anti-neutrophils; 200 µg) 24 hours after plug visualization in allogeneic-mated C57BL/6/BALB/c mice. Depletion of peripheral neutrophils lasted until 48 hours after anti-Gr1 injection (gestational day 1.5-3.5). On gestational day 5.5, neutrophil depletion impaired the blastocyst implantation, as 50% of pregnant mice presented reduced implantation sites. On gestational day 18.5, neutrophil depletion reduced the pregnancy rate and index, altered the placenta disposition in the uterine horns, and modified the structure of the placenta, detected by reduced junctional zone, associated with decreased numbers of giant trophoblast cells, spongiotrophoblast. Reduced number of placenta cells labeled for vascular endothelial growth factor (VEGF), platelet-endothelial cell adhesion molecule (PECAM-1), and intercellular cell adhesion molecule (ICAM-1), important markers of angiogenesis and adhesiveness, were detected in neutrophil depleted mice. Furthermore, neutrophil depletion promoted a higher frequency of monocytes, natural killers, and T regulatory cells, and lower frequency of cytotoxic T cells in the blood, and abnormal development of offspring. Associated data obtained herein highlight the pivotal role of neutrophils actions in the early stages of pregnancy, and address further investigations on the imbricating signaling evoked by neutrophils in the trophoblastic interaction with uterine epithelium.

TMT-based quantitative N-glycoproteomic analysis reveals glycoprotein protection can improve the quality of frozen bovine sperm

Cryopreservation of bovine semen plays a vital role in accelerating genetic improvement and elite breeding, but it has a detrimental effect on sperm quality, resulting in the decline of the reproductive efficiency. The glycosylation modification of protein has irreplaceable roles in spermatozoa. Herein, the effect of cryopreservation on glycoproteins of bovine spermatozoa has been studied for the first time using a tandem mass tag (TMT)-labeled quantitative glycoproteome. A total of 2598 proteins and 492 glycoproteins were identified, including 83 different expression proteins (DEPs) and 44 different expression glycosylated proteins (DEGPs) between fresh and frozen spermatozoa. Thirty-three DEPs are glycoproteins, which demonstrates that glycoproteins of bovine sperm were seriously affected by cryopreservation. Moreover, the effects include glycoprotein expression, glycosylation modification, and substructure localization for proteins such as glycoproteins TEX101, ACRBP, and IZOMU4. The biologic functions of the 115 changed proteins are mainly involved in sperm capacitation, migration in female genitalia, and sperm-egg interaction. Mostly key regulators were identified to be glycoproteins, which confirms that glycosylated proteins played important roles in bovine sperm. This comprehensive study of sperm glycoproteins helps to unravel the cryoinjury mechanisms, thus implying that glycoprotein protection should be an effective way to improve the quality of frozen sperm.

Evidence of Paraoxonases 1, 2, and 3 Expression in Human Ovarian Granulosa Cells

Increasing evidence suggests that the antioxidant paraoxonase proteins, PON1, PON2, and PON3, have a role in reproduction and may be synthesized by ovarian cells. The aim of this work was to investigate whether human ovarian granulosa cells (GC) express paraoxonases 1, 2, and 3 (PON1, PON2, and PON3) at both the transcriptional and protein levels. Cells were purified from follicle samples of women undergoing ovarian stimulation at oocyte retrieval. We analyzed mRNA by polymerase chain reaction using specific primers for the different variants and quantified the proteins by Western blot using commercially available human recombinant PON proteins as standards. The protein subcellular distribution was determined by immunofluorescence and confocal microscopy and the cell cycles by flow cytometry. Thymidine was used for cellular synchronization at G1/S. Human hepatoma HepG2 and immortalized granulosa COV434 cell lines were used to optimize methodologies. mRNAs from PON1, the two variants of PON2, and PON3 were detected in GC. The cells actively secreted PON1 and PON3, as evidenced by the protein detection in the incubation medium. PON1 and PON3 were mainly distributed in the cytoplasm and notably in the nucleus, while PON2 colocalized with mitochondria. Subcellular nucleo-cytoplasmic distribution of PON1 was associated with the cell cycle. This is the first evidence describing the presence of mRNAs and proteins of the three members of the PON family in human ovarian GC. This study provides the basis of further research to understand the role of these proteins in GC, which will contribute to a better understanding of the reproduction process.

Current Advancements in Noninvasive Profiling of the Embryo Culture Media Secretome

There have been over 8 million babies born through in vitro fertilization (IVF) and this number continues to grow. There is a global trend to perform elective single embryo transfers, avoiding risks associated with multiple pregnancies. It is therefore important to understand where current research of noninvasive testing for embryos stands, and what are the most promising techniques currently used. Furthermore, it is important to identify the potential to translate research and development into clinically applicable methods that ultimately improve live birth and reduce time to pregnancy. The current focus in the field of human reproductive medicine is to develop a more rapid, quantitative, and noninvasive test. Some of the most promising fields of research for noninvasive assays comprise cell-free DNA analysis, microscopy techniques coupled with artificial intelligence (AI) and omics analysis of the spent blastocyst media. High-throughput proteomics and metabolomics technologies are valuable tools for noninvasive embryo analysis. The biggest advantages of such technology are that it can differentiate between the embryos that appear morphologically identical and has the potential to identify the ploidy status noninvasively prior to transfer in a fresh cycle or before vitrification for a later frozen embryo transfer.