Human embryo implantation modelled in microfluidic channels

Microfluidic Platforms for Real-Time In Situ Monitoring of Biomarkers for Cellular Processes

Cellular processes are mechanisms carried out at the cellular level that are aimed at guaranteeing the stability of the organism they comprise. The investigation of cellular processes is key to understanding cell fate, understanding pathogenic mechanisms, and developing new therapeutic technologies. Microfluidic platforms are thought to be the most powerful tools among all methodologies for investigating cellular processes because they can integrate almost all types of the existing intracellular and extracellular biomarker-sensing methods and observation approaches for cell behavior, combined with precisely controlled cell culture, manipulation, stimulation, and analysis. Most importantly, microfluidic platforms can realize real-time in situ detection of secreted proteins, exosomes, and other biomarkers produced during cell physiological processes, thereby providing the possibility to draw the whole picture for a cellular process. Owing to their advantages of high throughput, low sample consumption, and precise cell control, microfluidic platforms with real-time in situ monitoring characteristics are widely being used in cell analysis, disease diagnosis, pharmaceutical research, and biological production. This review focuses on the basic concepts, recent progress, and application prospects of microfluidic platforms for real-time in situ monitoring of biomarkers in cellular processes.

Butyrate Improves Porcine Endometrial Epithelial Cell Receptivity via Enhancing Acetylation of Histone H3K9

SCOPE

Uterine receptivity is a major restriction of embryo implantation and survival, and the endometrial luminal epithelium serves as the transient gateway for uterine receptivity and embryo implantation. Butyrate is reported to promote the success of embryo implantation, but the effects and mechanism of butyrate on uterine receptivity are still unknown.

METHODS AND RESULTS

Porcine endometrial epithelial cells (PEECs) are used as a model, and the cellular receptivity changes, metabolism, and gene expression profiles influenced by butyrate are analyzed. The study finds that butyrate improves receptive changes in PEECs, including inhibiting proliferation, exhibiting more pinocytosis on the cell surface, and increasing adhesiveness to porcine trophoblast cells. In addition, butyrate increases prostaglandin synthesis and markedly impacts purine metabolism, pyrimidine metabolism, and the FoxO signaling pathway. siRNA to inhibit the expression of FoxO1 and chromatin immunoprecipitation-sequencing (ChIP-seq) of H3K9ac are used to demonstrate that the H3K9ac/FoxO1/PCNA pathway can contribute to the effects of cell proliferation inhibition and uterine receptivity improvement induced by butyrate.

CONCLUSION

The findings reveal that butyrate improves endometrial epithelial cell receptivity by enhancing the acetylation of histone H3K9, which shows nutritional regulation and therapeutic potential for poor uterine receptivity and difficulty in embryo implantation.

In Vitro Gametogenesis in Oncofertility: A Review of Its Potential Use and Present-Day Challenges in Moving toward Fertility Preservation and Restoration

Current fertility preservation options are limited for cancer survivor patients who wish to have their own biological children. Human in vitro gametogenesis (IVG) has the hypothetical ability to offer a unique solution to individuals receiving treatment for cancer which subsequently shortens their reproductive lifespan. Through a simple skin punch biopsy, a patient's fertility could be restored via reprogramming of dermal fibroblast cells to induced pluripotent stem cells, then from primordial germ cell-like cells into viable oocytes and spermatocytes which could be used for embryogenesis. Induced pluripotent stem cells could also be used to form in vitro environments, similar to the ovary or testes, necessary for the maturation of oogonia. This would allow for the entire creation of embryos outside the body, ex vivo. While this area in stem cell biology research offers the potential to revolutionize reproduction as we know it, there are many critical barriers, both scientific and ethical, that need to be overcome to one day see this technology utilized clinically.

Deconstructing human peri-implantation embryogenesis based on embryos and embryoids

The peri-implantation period from blastula to gastrula is one of the crucial stages of human embryo and stem cell development. During development, human embryos undergo many crucial events, such as embryonic lineage differentiation and development, structural self-assembly, pluripotency state transition, cell communication between lineages, and crosstalk between the embryo and uterus. Abnormalities in these developmental events will result in implantation failure or pregnancy loss. However, because of ethical and technical limits, the developmental dynamics of human peri-implantation embryos and the underlying mechanisms of abnormal development remain in a "black box". In this review, we summarize recent progress made towards our understanding of human peri-implantation embryogenesis based on extended in vitro cultured embryos and stem cell-based embryoids. These findings lay an important foundation for understanding early life, promoting research into human stem cells and their application, and preventing and treating infertility. We also propose key scientific issues regarding peri-implantation embryogenesis and provide an outlook on future study directions. Finally, we sum up China's contribution to the field and future opportunities.

Modelling human embryogenesis: embryo-like structures spark ethical and policy debate

BACKGROUND

Studying the human peri-implantation period remains hindered by the limited accessibility of the in vivo environment and scarcity of research material. As such, continuing efforts have been directed towards developing embryo-like structures (ELS) from pluripotent stem cells (PSCs) that recapitulate aspects of embryogenesis in vitro. While the creation of such models offers immense potential for studying fundamental processes in both pre- and early post-implantation development, it also proves ethically contentious due to wide-ranging views on the moral and legal reverence due to human embryos. Lack of clarity on how to qualify and regulate research with ELS thus presents a challenge in that it may either limit this new field of research without valid grounds or allow it to develop without policies that reflect justified ethical concerns.

OBJECTIVE AND RATIONALE

The aim of this article is to provide a comprehensive overview of the existing scientific approaches to generate ELS from mouse and human PSCs, as well as discuss future strategies towards innovation in the context of human development. Concurrently, we aim to set the agenda for the ethical and policy issues surrounding research on human ELS.

SEARCH METHODS

The PubMed database was used to search peer-reviewed articles and reviews using the following terms: 'stem cells', 'pluripotency', 'implantation', 'preimplantation', 'post-implantation', 'blastocyst', 'embryoid bodies', 'synthetic embryos', 'embryo models', 'self-assembly', 'human embryo-like structures', 'artificial embryos' in combination with other keywords related to the subject area. The PubMed and Web of Science databases were also used to systematically search publications on the ethics of ELS and human embryo research by using the aforementioned keywords in combination with 'ethics', 'law', 'regulation' and equivalent terms. All relevant publications until December 2019 were critically evaluated and discussed.

OUTCOMES

In vitro systems provide a promising way forward for uncovering early human development. Current platforms utilize PSCs in both two- and three-dimensional settings to mimic various early developmental stages, including epiblast, trophoblast and amniotic cavity formation, in addition to axis development and gastrulation. Nevertheless, much hinges on the term 'embryo-like'. Extension of traditional embryo frameworks to research with ELS reveals that (i) current embryo definitions require reconsideration, (ii) cellular convertibility challenges the attribution of moral standing on the basis of 'active potentiality' and (iii) meaningful application of embryo protective directives will require rethinking of the 14-day culture limit and moral weight attributed to (non-)viability. Many conceptual and normative (dis)similarities between ELS and embryos thus remain to be thoroughly elucidated.

WIDER IMPLICATIONS

Modelling embryogenesis holds vast potential for both human developmental biology and understanding various etiologies associated with infertility. To date, ELS have been shown to recapitulate several aspects of peri-implantation development, but critically, cannot develop into a fetus. Yet, concurrent to scientific innovation, considering the extent to which the use of ELS may raise moral concerns typical of human embryo research remains paramount. This will be crucial for harnessing the potential of ELS as a valuable research tool, whilst remaining within a robust moral and legal framework of professionally acceptable practices.

Endometrial cell-derived small extracellular vesicle miR-100-5p promotes functions of trophoblast during embryo implantation

Communication between maternal uterus and blastocyst occurs in the early stages of pregnancy, and the interaction influences the success of embryo implantation. Whereas small extracellular vesicles (sEVs) play an essential role in mediating intercellular communication in numerous biological processes, their role in embryo implantation during the window of implantation (WOI) remains poorly defined. Here, we report that endometrial epithelial cells (EECs) secrete sEVs during early pregnancy, which affects the trophoblast behaviors (migration, invasion, and proliferation), thus influencing embryo implantation. We show that microRNA (miR)-100-5p, sEVs containing microRNA (miRNA), activates both focal adhesion kinase (FAK) and c-Jun N-terminal kinase (JNK), as well as contributes to trophoblast migration and invasion. Furthermore, our findings indicate that the sEV miR-100-5p promotes angiogenesis during the implantation process. In conclusion, this study reveals a novel mechanism by which EEC-derived sEV miR-100-5p crosstalks with trophoblasts, leading to an enhanced ability for implantation.