Endometrial laminin subunit beta-3 expression associates with reproductive outcome in patients with repeated implantation failure

Analysis of gene and protein expression in the endometrium for validation of an ex vivo model of the equine uterus using PCR, digital and visual histopathology

In the past, most research in equine reproduction has been performed in vivo but the use of in vitro and ex vivo models has recently increased. This study aimed to evaluate the functional stability of an ex vivo hemoperfused model for equine uteri with molecular characterization of marker genes and their proteins. In addition, the study validated the respective protein expression and the aptness of the software QuPath for identifying and scoring immunohistochemically stained equine endometrium. After collection, uteri (n = 12) were flushed with preservation solution, transported to the laboratory on ice, and perfused with autologous blood for 6 h. Cycle stage was determined by examination of the ovaries for presence of Graafian follicles or corpora lutea and analysis of plasma progesterone concentration (estrus: n = 4; diestrus: n = 4; anestrus: n = 4). Samples were obtained directly after slaughter, after transportation, and during perfusion (240, 300, 360 min). mRNA expression levels of progesterone (PGR), estrogen (ESR1) and oxytocin (OXTR) receptor as well as of MKI67 (marker of cell growth) and CASP3 (marker of apoptosis) were analyzed by RT-qPCR, and correlation to protein abundance was validated by immunohistochemical staining. Endometrial samples were analyzed by visual and computer-assisted evaluation of stained antigens via QuPath. For PGR, effects of the perfusion and cycle stage on expression were found (P < 0.05), while ESR1 was affected only by cycle stage (P < 0.05) and OXTR was unaffected by perfusion and cycle stage. MKI67 was lower after 360 min of perfusion as compared to samples collected before perfusion (P < 0.05). For CASP3, differences in gene expression were found after transport and samples taken after 240 min (P < 0.05). Immunohistochemical staining revealed effects of perfusion on stromal and glandular cells for steroid hormone receptors, but not for Ki-67 and active Caspase 3. OXTR was visualized in all layers of the endometrium and was unaffected by perfusion. Comparison of QuPath and visual analysis resulted in similar results. For most cell types and stained antigens, the correlation coefficient was r > 0.5. In conclusion, the isolated hemoperfused model of the equine uterus was successfully validated at the molecular level, demonstrating stability of key marker gene expression. The utility of computer-assisted immunohistochemical analysis of equine endometrial samples was also confirmed.

Rhythm of the First Language: Dynamics of Extracellular Vesicle-Based Embryo-Maternal Communication in the Pre-Implantation Microenvironment

One of the most critical steps in mammalian reproduction is implantation. Embryos with an impaired capacity for embryo-maternal crosstalk are thought to have a reduced potential for implantation. One agent of embryo-maternal communication is extracellular vesicles (EV). EVs are lipid bilayer-bound biological nanoparticles implicated in intercellular communication between many of the known cell types. In the current study, we isolated EVs from trophoblast analogue JAr spheroids and supplemented the EVs with receptive endometrium analogue RL95-2 cells to simulate pre-implantation embryo-maternal dialogue. The transcriptome of the endometrial cells was examined at 30 min, 4 h and 48 h intervals using Oxford Nanopore^® technology. At the time points, 30 min, 4 h and 48 h, the endometrial cells showed a significantly altered transcriptome. It seems trophoblast EVs induce a swift and drastic effect on the endometrial transcriptome. The effect peaks at around 4 h of EV supplementation, indicating a generalized effect on cell physiology. Alterations are especially apparent in biological pathways critical to embryonic implantation, such as extracellular matrix-receptor interactions and cytokine-receptor interactions. These observations can be helpful in elucidating the dynamics of embryo-maternal communication in the pre-implantation period.

Proteomic analysis of extracellular vesicles secreted by primary human epithelial endometrial cells reveals key proteins related to embryo implantation

BACKGROUND

Successful implantation is dependent on coordination between maternal endometrium and embryo, and the role of EVs in the required cross-talk cell-to-cell has been recently established. In this regard, it has been reported that EVs secreted by the maternal endometrium can be internalized by human trophoblastic cells transferring their contents and enhancing their adhesive and invasive capacity. This is the first study to comprehensively evaluate three EV isolation methods on human endometrial epithelial cells in culture and to describe the proteomic content of EVs secreted by pHEECs from fertile women.

METHODS

Ishikawa cells and pHEECs were in vitro cultured and hormonally treated; subsequently, conditioned medium was collected and EVs isolated. Ishikawa cells were used for the comparison of EVs isolation methods ultracentrifugation, ExoQuick-TC and Norgen Cell Culture Media Exosome Purification Kit (n = 3 replicates/isolation method). pHEECs were isolated from endometrial biopsies (n = 8/replicate; 3 replicates) collected from healthy oocyte donors with confirmed fertility, and protein content of EVs isolated by the most efficient methodology was analysed using liquid chromatography-tandem mass spectrometry. EV concentration and size were analyzed by nanoparticle tracking analysis, EV morphology visualized by transmission electron microscopy and protein marker expression was determined by Western blotting.

RESULTS

Ultracentrifugation was the most efficient methodology for EV isolation from medium of endometrial epithelial cells. EVs secreted by pHEECs and isolated by ultracentrifugation were heterogeneous in size and expressed EV protein markers HSP70, TSG101, CD9, and CD81. Proteomic analysis identified 218 proteins contained in these EVs enriched in biological processes involved in embryo implantation, including cell adhesion, differentiation, communication, migration, extracellular matrix organization, vasculature development, and reproductive processes. From these proteins, 82 were selected based on their functional relevance in implantation success as possible implantation biomarkers.

CONCLUSIONS

EV protein cargos are implicated in biological processes related to endometrial receptivity, embryo implantation, and early embryo development, supporting the concept of a communication system between the embryo and the maternal endometrium via EVs. Identified proteins may define new biomarkers of endometrial receptivity and implantation success.