Dynamic microfunnel culture enhances mouse embryo development and pregnancy rates

Micro-vibration results in vitro-derived bovine blastocysts with greater cryotolerance, epigenetic abnormalities, and a massive transcriptional change

Much effort has been employed to improve the quality of embryos obtained by in vitro production (IVP) given the relevance of this technology to current livestock systems. In this context, dynamic IVP systems have proved beneficial to the embryo once they mimic fluid flows and mechanical forces resulting from the movement of ciliated cells and muscle contraction in the reproductive tract. In the present study, we sought to confirm these initial findings as well as assess potential molecular consequences to the embryo by applying micro-vibration (45 Hz for 5 s once per 60 min) during both oocyte maturation and embryo culture in cattle. As a result, micro-vibration led to lower incidence of apoptosis in blastocysts following vitrification-thawing. Further analyses revealed epigenetic and transcriptional changes in blastocysts derived from the micro-vibration treatment, with a total of 502 differentially expressed genes. Enrichment analyses linked differentially expressed genes to 'Oxidative phosphorylation', 'Cytokine-cytokine receptor interaction', and 'Signaling pathways regulating pluripotency of stem cells'. Yet, a meta-analysis indicated that the transcriptional changes induced by micro-vibration were not toward that of in vivo-derived embryos. In conclusion, micro-vibration increases the cryoresistance of bovine embryos, but caution should be taken given the unclear consequences of epigenetic and transcriptional abnormalities induced by the treatment.

Non-invasive evaluation of embryo quality for the selection of transferable embryos in human in vitro fertilization-embryo transfer

The ultimate goal of human assisted reproductive technology is to achieve a healthy pregnancy and birth, ideally from the selection and transfer of a single competent embryo. Recently, techniques for efficiently evaluating the state and quality of preimplantation embryos using time-lapse imaging systems have been applied. Artificial intelligence programs based on deep learning technology and big data analysis of time-lapse monitoring system during in vitro culture of preimplantation embryos have also been rapidly developed. In addition, several molecular markers of the secretome have been successfully analyzed in spent embryo culture media, which could easily be obtained during in vitro embryo culture. It is also possible to analyze small amounts of cell-free nucleic acids, mitochondrial nucleic acids, miRNA, and long non-coding RNA derived from embryos using real-time polymerase chain reaction (PCR) or digital PCR, as well as next-generation sequencing. Various efforts are being made to use non-invasive evaluation of embryo quality (NiEEQ) to select the embryo with the best developmental competence. However, each NiEEQ method has some limitations that should be evaluated case by case. Therefore, an integrated analysis strategy fusing several NiEEQ methods should be urgently developed and confirmed by proper clinical trials.

Oviduct-mimicking microfluidic chips decreased the ROS concentration in the in vitro fertilized embryos of CD-1 mice

BACKGROUND

The process of the assisted reproductive technology (ART) cycle is extremely complicated, and various factors in each step may influence the final clinical outcomes; thus, optimizing culture conditions for embryos is crucial in the ART cycle, particularly when the traditional petri-dish method remains unchanged for decades. In the current study, we intend to culture embryos in a dynamic environment on chips to optimize the embryo culture conditions.

METHODS

Multilayer soft lithography technology was utilized to establish a microfluidics-based oviduct. Mouse primary oviduct epithelial cells were identified by immunofluorescence staining and then loaded into the chip to coculture with the embryos. The development potential parameters of embryos on chips with cells, on chips without cells, and in drops were compared, as well as reactive oxygen species (ROS) in embryos.

RESULTS

There were no obvious differences regarding the fertilization rate, 4-Cell embryo rate, cleavage rate, high-quality embryo rate, or blastocyst formation rate. However, the intracellular ROS levels in 4-Cell stage embryos on chips with cells were statistically significantly lower than those in drops (P < 0.001). This organ-on-chip device allowed the probability of mammalian embryo culture in a microfluidic-based manner.

CONCLUSIONS

Our findings demonstrated that this novel oviduct-on-chip model may optimize embryo culture conditions by reducing intracellular ROS levels, which may be a competent alternative to the existing stable embryo culture system.

Surface functionalization of poly(dimethylsiloxane) substrates facilitates culture of pre-implantation mouse embryos by blocking non-selective adsorption

Poly(dimethylsiloxane) (PDMS) is widely used in biomedical settings such as microfluidics for its optical transparency, castability, gas permeability and relative biocompatibility. While PDMS devices with certain modifications or treatments have been used for mammalian pre-implantation embryo culture, it is unclear why native PDMS leads to significant embryo death. In this study, we employ Nile Red as a model hydrophobic small molecule to demonstrate that significant hydrophobic sequestration occurs on native PDMS substrates even with a bovine serum albumin-containing KSOM pre-equilibration. Our results suggest that this small molecule sequestration has detrimental effects on mouse embryo development in PDMS static culture wells, with 0% blastocyst development rates from embryos cultured on native PDMS. We found that prior saturation of the PDMS culture well with water vapour only rescues about 10% of blastocyst development rates, indicating osmolality alone is not responsible for the high rates of embryo arrest. We also present a safe and simple Pluronic F127 pretreatment for PDMS substrates that successfully circumvented the harmful effects of native PDMS, achieving a blastocyst and implantation rate akin to that of our polystyrene controls. Our results call into question how researchers and clinicians can account for the alterations in medium composition and embryo secretions when using hydrophobic substrates, especially in the mammalian embryo culture setting where minimum effective concentrations of peptides and amino acids are commonplace.

The Future of IVF: The New Normal in Human Reproduction

Increased demand for in vitro fertilization (IVF) due to socio-demographic trends, and supply facilitated by new technologies, converged to transform the way a substantial proportion of humans reproduce. The purpose of this article is to describe the societal and demographic trends driving increased worldwide demand for IVF, as well as to provide an overview of emerging technologies that promise to greatly expand IVF utilization and lower its cost.

Dynamic shapes of the zygote and two-cell mouse and human

Mouse zygote morphokinetics were measured during interphase, the mitotic period, cytokinesis, and two-cell stage. Sequences of rounder-distorted-rounder shapes were revealed, as were changing patterns of cross section area. A calcium chelator and an actin-disrupting agent inhibited the area changes that occurred between pronuclear envelope breakdown and cytokinesis. During cell division, two vortices developed in each nascent cell and they rotated in opposite directions at each end of the cell, a pattern that sometimes persisted for up to 10 h. Exchange with the environment may have been promoted by these shape and area cycles and persisting circulation in the cytoplasm may have a similar function between a cell's interior and periphery. Some of these movements were sporadically also seen in human zygotes with abnormal numbers of pronuclei and the two-cell stages that developed from these compromised human zygotes.

Mechanobiology of the female reproductive system

BACKGROUND

Mechanobiology in the field of human female reproduction has been extremely challenging technically and ethically.

METHODS

The present review provides the current knowledge on mechanobiology of the female reproductive system. This review focuses on the early phases of reproduction from oocyte development to early embryonic development, with an emphasis on current progress.

MAIN FINDINGS RESULTS

Optimal, well-controlled mechanical cues are required for female reproductive system physiology. Many important questions remain unanswered; whether and how mechanical imbalances among the embryo, decidua, and uterine muscle contractions affect early human embryonic development, whether the biomechanical properties of oocytes/embryos are potential biomarkers for selecting high-quality oocytes/embryos, whether mechanical properties differ between the two major compartments of the ovary (cortex and medulla) in normally ovulating human ovaries, whether durotaxis is involved in several processes in addition to embryonic development. Progress in mechanobiology is dependent on development of technologies that enable precise physical measurements.

CONCLUSION

More studies are needed to understand the roles of forces and changes in the mechanical properties of female reproductive system physiology. Recent and future technological advancements in mechanobiology research will help us understand the role of mechanical forces in female reproductive system disorders/diseases.

In vitro fertilization and andrology laboratory in 2030: expert visions

The aim of this article is to gather 9 thought leaders and their team members to present their ideas about the future of in vitro fertilization and the andrology laboratory. Although we have seen much progress and innovation in the laboratory over the years, there is still much to come, and this article looks at what these leaders think will be important in the future development of technology and processes in the laboratory.

A Review on Microfluidics: An Aid to Assisted Reproductive Technology

Infertility is a state of the male or female reproductive system that is defined as the failure to achieve pregnancy even after 12 or more months of regular unprotected sexual intercourse. Assisted reproductive technology (ART) plays a crucial role in addressing infertility. Various ART are now available for infertile couples. Fertilization in vitro (IVF), intracytoplasmic sperm injection (ICSI) and intrauterine insemination (IUI) are the most common techniques in this regard. Various microfluidic technologies can incorporate various ART procedures such as embryo and gamete (sperm and oocyte) analysis, sorting, manipulation, culture and monitoring. Hence, this review intends to summarize the current knowledge about the application of this approach towards cell biology to enhance ART.

Organ-on-a-chip technology for the study of the female reproductive system

Over the past decade, organs-on-a-chip and microphysiological systems have emerged as a disruptive in vitro technology for biopharmaceutical applications. By enabling new capabilities to engineer physiological living tissues and organ units in the precisely controlled environment of microfabricated devices, these systems offer great promise to advance the frontiers of basic and translational research in biomedical sciences. Here, we review an emerging body of interdisciplinary work directed towards harnessing the power of organ-on-a-chip technology for reproductive biology and medicine. The focus of this topical review is to provide an overview of recent progress in the development of microengineered female reproductive organ models with relevance to drug delivery and discovery. We introduce the engineering design of these advanced in vitro systems and examine their applications in the study of pregnancy, infertility, and reproductive diseases. We also present two case studies that use organ-on-a-chip design principles to model placental drug transport and hormonally regulated crosstalk between multiple female reproductive organs. Finally, we discuss challenges and opportunities for the advancement of reproductive organ-on-a-chip technology.

Recent advances in critical nodes of embryo engineering technology

The normal development and maturation of oocytes and sperm, the formation of fertilized ova, the implantation of early embryos, and the growth and development of foetuses are the biological basis of mammalian reproduction. Therefore, research on oocytes has always occupied a very important position in the life sciences and reproductive medicine fields. Various embryo engineering technologies for oocytes, early embryo formation and subsequent developmental stages and different target sites, such as gene editing, intracytoplasmic sperm injection (ICSI), preimplantation genetic diagnosis (PGD), and somatic cell nuclear transfer (SCNT) technologies, have all been established and widely used in industrialization. However, as research continues to deepen and target species become more advanced, embryo engineering technology has also been developing in a more complex and sophisticated direction. At the same time, the success rate also shows a declining trend, resulting in an extension of the research and development cycle and rising costs. By studying the existing embryo engineering technology process, we discovered three critical nodes that have the greatest impact on the development of oocytes and early embryos, namely, oocyte micromanipulation, oocyte electrical activation/reconstructed embryo electrofusion, and the in vitro culture of early embryos. This article mainly demonstrates the efforts made by researchers in the relevant technologies of these three critical nodes from an engineering perspective, analyses the shortcomings of the current technology, and proposes a plan and prospects for the development of embryo engineering technology in the future.

Metabolomic Analysis Evidences That Uterine Epithelial Cells Enhance Blastocyst Development in a Microfluidic Device

Here we report the use of a microfluidic system to assess the differential metabolomics of murine embryos cultured with endometrial cells-conditioned media (CM). Groups of 10, 1-cell murine B6C3F1 × B6D2F1 embryos were cultured in the microfluidic device. To produce CM, mouse uterine epithelial cells were cultured in potassium simplex optimized medium (KSOM) for 24 h. Media samples were collected from devices after 5 days of culture with KSOM (control) and CM, analyzed by reverse phase liquid chromatography and untargeted positive ion mode mass spectrometry analysis. Blastocyst rates were significantly higher (p < 0.05) in CM (71.8%) compared to control media (54.6%). We observed significant upregulation of 341 compounds and downregulation of 214 compounds in spent media from CM devices when compared to control. Out of these, 353 compounds were identified showing a significant increased abundance of metabolites involved in key metabolic pathways (e.g., arginine, proline and pyrimidine metabolism) in the CM group, suggesting a beneficial effect of CM on embryo development. The metabolomic study carried out in a microfluidic environment confirms our hypothesis on the potential of uterine epithelial cells to enhance blastocyst development. Further investigations are required to highlight specific pathways involved in embryo development and implantation.

Design and Microfabrication of An On-Chip Oocyte Maturation System for Reduction of Apoptosis

Objective

In customary assisted reproductive technology (ART), oocyte culture occurs in static micro drops of Petri dishes with vast media volume; while, the in vivo condition is dynamic. In this study, we aimed to improve the maturation efficiency of mammalian oocytes by designing an optimal microchamber array to obtain the integration of oocyte trapping and maturation within a microfluidic device and evaluate the role of microfluidic culture condition in lipid peroxidation level of the culture medium, in vitro matured oocytes apoptosis, and its comparison with the conventional static system.

Materials and Methods

In this experimental research, immature oocytes were collected from ovaries of the Naval Medical Research Institute (NMRI) mice. Oocytes were randomly laid in static and dynamic (passive and active) in vitro maturation culture medium for 24 hours. The lipid peroxidation level in oocyte culture media was assessed by measuring the concentration of malondialdehyde (MDA), and the rate of apoptosis in in vitro matured oocytes was assessed by the TUNEL assay after a-24 hour maturation period.

Results

The MDA concentration in both dynamic oocyte maturation media were significantly lower than the static medium (0.003 and 0.002 vs. 0.13 μmol/L, P<0.01). Moreover, the rate of apoptosis in matured oocytes after a-24 hour maturation period was significantly lower in passive dynamic and active dynamic groups compared with the static group (16%, 15% vs. 35%, P<0.01).

Conclusion

The dynamic culture for in vitro oocyte maturation (IVM) improves the viability of IVM oocytes in comparison with the static culture condition.

Microfluidics in male reproduction: is ex vivo culture of primate testis tissue a future strategy for ART or toxicology research?

The significant rise in male infertility disorders over the years has led to extensive research efforts to recapitulate the process of male gametogenesis in vitro and to identify essential mechanisms involved in spermatogenesis, notably for clinical applications. A promising technology to bridge this research gap is organ-on-chip (OoC) technology, which has gradually transformed the research landscape in ART and offers new opportunities to develop advanced in vitro culture systems. With exquisite control on a cell or tissue microenvironment, customized organ-specific structures can be fabricated in in vitro OoC platforms, which can also simulate the effect of in vivo vascularization. Dynamic cultures using microfluidic devices enable us to create stimulatory effect and non-stimulatory culture conditions. Noteworthy is that recent studies demonstrated the potential of continuous perfusion in OoC systems using ex vivo mouse testis tissues. Here we review the existing literature and potential applications of such OoC systems for male reproduction in combination with novel bio-engineering and analytical tools. We first introduce OoC technology and highlight the opportunities offered in reproductive biology in general. In the subsequent section, we discuss the complex structural and functional organization of the testis and the role of the vasculature-associated testicular niche and fluid dynamics in modulating testis function. Next, we review significant technological breakthroughs in achieving in vitro spermatogenesis in various species and discuss the evidence from microfluidics-based testes culture studies in mouse. Lastly, we discuss a roadmap for the potential applications of the proposed testis-on-chip culture system in the field of primate male infertility, ART and reproductive toxicology.

Biophysical optimization of preimplantation embryo culture: what mechanics can offer ART

Owing to the rise of ART and mounting reports of epigenetic modification associated with them, an understanding of optimal embryo culture conditions and reliable indicators of embryo quality are highly sought after. There is a growing body of evidence that mechanical biomarkers can rival embryo morphology as an early indicator of developmental potential and that biomimetic mechanical cues can promote healthy development in preimplantation embryos. This review will summarize studies that investigate the role of mechanics as both indicators and promoters of mammalian preimplantation embryo development and evaluate their potential for improving future embryo culture systems.

Microfluidic Systems for Assisted Reproductive Technologies: Advantages and Potential Applications

Microfluidic technologies have emerged as a powerful tool that can closely replicate the in-vivo physiological conditions of organ systems. Assisted reproductive technology (ART), while being able to achieve successful outcomes, still faces challenges related to technical error, efficiency, cost, and monitoring/assessment. In this review, we provide a brief overview of the uses of microfluidic devices in the culture, maintenance and study of ovarian follicle development for experimental and therapeutic applications. We discuss existing microfluidic platforms for oocyte and sperm selection and maintenance, facilitation of fertilization by in-vitro fertilization/intracytoplastimc sperm injection, and monitoring, selection and maintenance of resulting embryos. Furthermore, we discuss the possibility of future integration of these technologies onto a single platform and the limitations facing the development of these systems. In spite of these challenges, we envision that microfluidic systems will likely evolve and inevitably revolutionize both fundamental, reproductive physiology/toxicology research as well as clinically applicable ART.

Understanding and Assisting Reproduction in Wildlife Species Using Microfluidics

Conservation breeding and assisted reproductive technologies (ARTs) are invaluable tools to save wild animal species that are on the brink of extinction. Microfluidic devices recently developed for human or domestic animal reproductive medicine could significantly help to increase knowledge about fertility and contribute to the success of ART in wildlife. Some of these microfluidic tools could be applied to wild species, but dedicated efforts will be necessary to meet specific needs in animal conservation; for example, they need to be cost-effective, applicable to multiple species, and field-friendly. Microfluidics represents only one powerful technology in a complex toolbox and must be integrated with other approaches to be impactful in managing wildlife reproduction.

Using a Dielectrophoretic Microfluidic Biochip Enhanced Fertilization of Mouse Embryo in Vitro

Droplet microfluidics has appealed to many interests for its capability to epitomize cells in a microscale environment and it is also a forceful technique for high-throughput single-cell epitomization. A dielectrophoretic microfluidic system imitates the oviduct of mammals with a microchannel to achieve fertilization in vitro (IVF) of an imprinting control-region (ICR) mouse. We applied a microfluidic chip and a positive dielectrophoretic (p-DEP) force to capture and to screen the sperm for the purpose of manipulating the oocyte. The p-DEP responses of the oocyte and sperm were exhibited under applied bias conditions (waveform AC 10 V_pp, 1 MHz) for trapping 1 min. The insemination concentration of sperm nearby the oocyte was increased to enhance the probability of natural fertilization through the p-DEP force trapping. A simulation tool (CFDRC-ACE+) was used to simulate and to analyze the distribution of the electric field. The DEP microfluidic devices were fabricated using poly (dimethylsiloxane) (PDMS) and ITO (indium tin oxide)-glass with electrodes. We discuss the requirement of sperm in a DEP microfluidic chip at varied concentrations to enhance the future rate of fertilization in vitro for an oligozoospermia patient. The result indicates that the rate of fertility in our device is 17.2 ± 7.5% (n = 30) at about 3000 sperms, compatible with traditional droplet-based IVF, which is 14.2 ± 7.5% (n = 28).

Implications of Assisted Reproductive Technologies for Pregnancy Outcomes in Mammals

Development of assisted reproductive technologies has been driven by the goals of reducing the incidence of infertility, increasing the number of offspring from genetically elite animals, facilitating genetic manipulation, aiding preservation and long-distance movement of germplasm, and generating research material. Superovulation is associated with reduced fertilization rate and alterations in endometrial function. In vitro production of embryos can have a variety of consequences. Most embryos produced in vitro are capable of establishing pregnancy and developing into healthy neonatal animals. However, in vitro production is associated with reduced ability to develop to the blastocyst stage, increased incidence of failure to establish pregnancy, placental dysfunction, and altered fetal development. Changes in the developmental program mean that some consequences of being produced in vitro can extend into adult life. Reduced competence of the embryo produced in vitro to develop to the blastocyst stage is caused largely by disruption of events during oocyte maturation and fertilization. Conditions during embryo culture can affect embryo freezability and competence to establish pregnancy after transfer. Culture conditions, including actions of embryokines, can also affect the postnatal phenotype of the resultant progeny.

Suppression of TGF-β and ERK Signaling Pathways as a New Strategy to Provide Rodent and Non-Rodent Pluripotent Stem Cells

Stem cells are unspecialized cells and excellent model in developmental biology and a promising approach to the treatment of disease and injury. In the last 30 years, pluripotent embryonic stem (ES) cells were established from murine and primate sources, and display indefinite replicative potential and the ability to differentiate to all three embryonic germ layers. Despite large efforts in many aspects of rodent and non-rodent pluripotent stem cell culture, a number of diverse challenges remain. Natural and synthetic small molecules (SMs) strategy has the potential to overcome these hurdles. Small molecules are typically fast and reversible that target specific signaling pathways, epigenetic processes and other cellular processes. Inhibition of the transforming growth factor-β (TGF-β/Smad) and fibroblast growth factor 4 (FGF4)/ERK signaling pathways by SB431542 and PD0325901 small molecules, respectively, known as R2i, enhances the efficiency of mouse, rat, and chicken pluripotent stem cells passaging from different genetic backgrounds. Therefore, the application of SM inhibitors of TGF-β and ERK1/2 with leukemia inhibitory factor (LIF) allows the cultivation of pluripotent stem cells in a chemically defined condition. In this review, we discuss recently emerging evidence that dual inhibition of TGF-β and FGF signaling pathways plays an important role in regulating pluripotency in both rodent and non-rodent pluripotent stem cells.

Organs-On-Chip Models of the Female Reproductive System

Microfluidic-based technology attracts great interest in cell biology and medicine, in virtue of the ability to better mimic the in vivo cell microenvironment compared to conventional macroscale cell culture platforms. Recent Organs-on-chip (OoC) models allow to reproduce in vitro tissue and organ-level functions of living organs and systems. These models have been applied for the study of specific functions of the female reproductive tract, which is composed of several organs interconnected through intricate endocrine pathways and communication mechanisms. To date, a disease and toxicology study of this system has been difficult to perform. Thus, there is a compelling need to develop innovative platforms for the generation of disease model and for performing drug toxicity/screening in vitro studies. This review is focused on the analysis of recently published OoC models that recreate pathological and physiological characteristics of the female reproductive organs and tissues. These models aim to be used to assess changes in metabolic activity of the specific cell types and the effect of exposure to hormonal treatment or chemical substances on some aspects of reproduction and fertility. We examined these models in terms of device specifications, operating procedures, accuracy for studying the biochemical and functional activity of living tissues and the paracrine signalling that occurs within the different tissues. These models represent a powerful tool for understanding important diseases and syndromes affecting women all around the world. Immediate adoption of these models will allow to clarify diseases, causes and adverse events occurring during pregnancy such as pre-eclampsia, infertility or preterm birth, endometriosis and infertility.

Mouse embryo assay to evaluate polydimethylsiloxane (PDMS) embryo-toxicity

In vitro embryo culture to support In Vitro Fertilization (IVF) procedures is a well-established but still critical technique. In the last decade first attempts to use microfluidic devices in IVF have shown positive results, enabling to control the culture conditions and to preserve the quality of the embryos during their development. In this study we completed an industry standard mouse embryo assay (MEA) to exclude potential toxic effects of PDMS.

Embryo culture at a reduced oxygen concentration of 5%: a mini review

The optimum oxygen tension for culturing mammalian embryos has been widely debated by the scientific community. While several laboratories have moved to using 5% as the value for oxygen tension, the majority of modern in vitro fertilization (IVF) laboratory programmes still use 20%. Several in vivo studies have shown the oxygen tension measured in the oviduct of mammals fluctuates between 2% and 8% and in cows and primates this values drops to <2% in the uterine milieu. In human IVF, a non-physiological level of 20% oxygen has been used in the past. However, several studies have shown that atmospheric oxygen introduces adverse effects to embryo development, not limited to numerous molecular and cellular physiology events. In addition, low oxygen tension plays a critical role in reducing the high level of detrimental reactive oxygen species within cells, influences embryonic gene expression, helps with embryo metabolism of glucose, and enhances embryo development to the blastocyst stage. Collectively, this improves embryo implantation potential. However, clinical studies have yielded contradictory results. In almost all reports, some level of improvement has been identified in embryo development or implantation, without any observed drawbacks. This review article will examine the recent literature and discusses ongoing efforts to understand the benefits that low oxygen tension can bring to mammal embryo development in vitro.

Improvement of embryonic development and clinical outcomes of germinal vesicle stage oocytes using a microvibration culture system

In vitro maturation (IVM) has evolved as a clinical treatment option in assisted reproductive technology. However, the poor developmental potential of germinal vesicle (GV)-stage oocytes is still suboptimal. This study's objective was to evaluate the effect of a microvibration culture system (MVC) during IVM and/or in vitro culture (IVC) on the clinical outcomes and the embryonic development potential of human GV-stage oocytes collected from human chorionic gonadotropin (HCG)-primed IVM and fertilization-embryo transfer (IVM/F-ET) cycles of patients with polycystic ovaries (PCO). A total of 206 HCG-primed IVM/F-ET cycles were divided into four groups according to the microvibration and static culture system applied during IVM and/or IVC: Group SS (static system during both IVM and IVC); Group SV (static system during IVM alternated with microvibration system during IVC); Group VS (microvibration system during IVM alternated with static system during IVC), and Group VV (microvibration system during both IVM and IVC). The results indicate that the rates of in vitro MII oocytes per cycle, fertilization, and cleavage were not significantly different between the groups. The rate of good-quality embryos in Group SV tended to be higher than the rate in Groups SS and VS, but there was no significant difference between Group SS and Group SV. Clinical pregnancy, implantation, and live birth rates of Groups SV and VS were slightly higher than those of Group SS. However, the rate of good-quality embryos with at least six cells on day 4, the clinical pregnancy, implantation, and live births in Group VV were significantly higher than those in Group SS. These results indicate that, compared with the static culture system, the MVC system applied for both IVM and IVC seems to improve the clinical outcomes and the quality of embryos of GV oocytes derived from HCG-primed IVM/F-ET cycles in PCO patients. Abbreviations: PCO: polycystic ovaries; HCG: human chorionic gonadotropin; GV: germinal vesicle; MII: metaphase II; IVM: in vitro maturation; IVF: in vitro fertilization; IVC: in vitro culture: MVC: microvibration culture; SC: static culture; ICSI: intracytoplasmic sperm injection; IVM/F-ET: IVM and fertilization-embryo transfer; AMH: anti-Mullerian hormone; OHSS: ovarian hyperstimulation syndrome.

Enhancing developmental rate and quality of mouse single blastomeres into blastocysts using a microplatform

The present work reports the beneficial effects of using a microplatform on the development of mouse single blastomeres (SBs) to the blastocyst stage. Development of blastocysts from SBs separated from two- and four-cell stage embryos (two- and four-cell SBs) can provide a valuable supply both for couples who use fertility-assisted techniques and farm animals. As a step forward, we introduce three chips that provide the possibility of culturing SBs separately, in groups, and in the vicinity of the intact embryo (co-culture), while each well of the chips is assigned to an isolated SB. Two- and four-cell SBs co-cultured with intact embryos showed 97.1% and 76.6% developmental rates and up to 34.1% and 49.1% growth relative to the microdroplet method (control). We examined the quality of developed blastocysts by assessing the total cell number, the number of inner cell mass (ICM) according to the octamer-binding transcription factor 4 marker (OCT4), and trophectoderm (TE). Co-culture of SBs with an intact embryo in a chip with nanoscale culture medium volume also increased the cell population of the developed embryo. The ICM:TE ratio, which is the most important blastocyst quality parameter, also indicated that developed two-cell SBs have a higher degree of similarity to intact embryos despite fewer numbers of total cells.

Application of microfluidic technologies to human assisted reproduction

Microfluidics can be considered both a science and a technology. It is defined as the study of fluid behavior at a sub-microliter level and the investigation into its application to cell biology, chemistry, genetics, molecular biology and medicine. There are at least two characteristics of microfluidics, mechanical and biochemical, which can be influential in the field of mammalian gamete and preimplantation embryo biology. These microfluidic characteristics can assist in basic biological studies on sperm, oocyte and preimplantation embryo structure, function and environment. The mechanical and biochemical characteristics of microfluidics may also have practical and/or technical application(s) to assisted reproductive technologies (ART) in rodents, domestic species, endangered species and humans. This review will consider data in mammals, and when available humans, addressing the potential application(s) of microfluidics to assisted reproduction. There are numerous sequential steps in the clinical assisted reproductive laboratory process that work, yet could be improved. Cause and effect relations of procedural inefficiencies can be difficult to identify and/or remedy. Data will be presented that consider microfluidic applications to sperm isolation, oocyte cumulus complex isolation, oocyte denuding, oocyte mechanical manipulation, conventional insemination, intracytoplasmic sperm injection, embryo culture, embryo analysis and oocyte and embryo cryopreservation. While these studies have progressed in animal models, data with human gametes and embryos are significantly lacking. These data from clinical trials are requisite for making future evidence-based decisions regarding the application of microfluidics in human ART.

Microphysiologic systems in female reproductive biology

Microphysiologic systems (MPS), including new organ-on-a-chip technologies, recapitulate tissue microenvironments by employing specially designed tissue or cell culturing techniques and microfluidic flow. Such systems are designed to incorporate physiologic factors that conventional 2D or even 3D systems cannot, such as the multicellular dynamics of a tissue-tissue interface or physical forces like fluid sheer stress. The female reproductive system is a series of interconnected organs that are necessary to produce eggs, support embryo development and female health, and impact the functioning of non-reproductive tissues throughout the body. Despite its importance, the human reproductive tract has received less attention than other organ systems, such as the liver and kidney, in terms of modeling with MPS. In this review, we discuss current gaps in the field and areas for technological advancement through the application of MPS. We explore current MPS research in female reproductive biology, including fertilization, pregnancy, and female reproductive tract diseases, with a focus on their clinical applications. Impact statement This review discusses existing microphysiologic systems technology that may be applied to study of the female reproductive tract, and those currently in development to specifically investigate gametes, fertilization, embryo development, pregnancy, and diseases of the female reproductive tract. We focus on the clinical applicability of these new technologies in fields such as assisted reproductive technologies, drug testing, disease diagnostics, and personalized medicine.

A novel method to understand tumor cell invasion: integrating extracellular matrix mimicking layers in microfluidic chips by "selective curing"

A major challenge in studying tumor cell invasion into its surrounding tissue is to identify the contribution of individual factors in the tumor microenvironment (TME) to the process. One of the important elements of the TME is the fibrous extracellular matrix (ECM) which is known to influence cancer cell invasion, but exactly how remains unclear. Therefore, there is a need for new models to unravel mechanisms behind the tumor-ECM interaction. In this article, we present a new microfabrication method, called selective curing, to integrate ECM-mimicking layers between two microfluidic channels. This method enables us to study the effect of 3D matrices with controlled architecture, beyond the conventionally used hydrogels, on cancer invasion in a controlled environment. As a proof of principle, we have integrated two electrospun Polycaprolactone (PCL) matrices with different fiber diameters in one chip. We then studied the 3D migration of MDA-MB-231 breast cancer cells into the matrices under the influence of a chemotactic gradient. The results show that neither the invasion distance nor the general cell morphology is affected significantly by the difference in fiber size of these matrices. The cells however do produce longer and more protrusions in the matrix with smaller fiber size. This microfluidic system enables us to study the influence of other factors in the TME on cancer development as well as other biological applications as it provides a controlled compartmentalized environment compatible with cell culturing.

Using stem cell oxygen physiology to optimize blastocyst culture while minimizing hypoxic stress

This review is a response to the Fellows Forum on testing 2% oxygen for best culture of human blastocysts (J Ass Reprod Gen 34:303-8, 1; J Ass Reprod Gen 34:309-14, 2) prior to embryo transfer. It is a general analysis in support of the position that an understanding of stem cell physiology and responses to oxygen are necessary for optimization of blastocyst culture in IVF and to enhance reproductive success in fertile women.

Near-infrared laser irradiation improves the development of mouse pre-implantation embryos

The aim of the present study was to assess the effects of near-infrared laser irradiation on the in vitro development of mouse embryos. Female ICR mice were superovulated with pregnant mare serum gonadotropin and human chorionic gonadotropin (hCG), and mated with male mice. Two-cell stage embryos were collected 40 h after administering hCG and cultured in M16 medium. Two-cell embryos (0 h after culture), 8-cell embryos (approx. 30 h after culture), morula (approx. 48 h after culture), and blastocysts (approx. 73 h after culture) were irradiated at 904 nm for 60 s. These embryos were cultured in a time-lapse monitoring system and the timing of blastocyst hatching was evaluated. Some of the irradiated blastocysts were transferred to the uterine horns of pseudopregnant recipients immediately after irradiation. Pregnancy rates, and offspring growth and fertility, were evaluated. Near-infrared laser irradiation increased the speed of in vitro mouse embryo development. In irradiated blastocysts, hatching was faster than in control (non-irradiated) blastocysts (18.4 vs. 28.2 h, P < 0.05). When 195 irradiated blastocysts were transferred to 18 pseudopregnant mice, all became pregnant and 92 (47.2%) normal-looking pups were born alive. When 182 control blastocysts were transferred to 17 pseudopregnant mice, 14 (82.4%) became pregnant and 54 (29.7%) normal-looking pups were born alive. The growth trajectories (up to 5 weeks) of offspring from irradiated blastocysts were similar to those from control blastocysts. Second generation offspring from transplanted animals were all fertile. These results indicate that near-infrared laser irradiation improves the quality of mouse embryo development in vitro, and increases the live birth rate without affecting the normality of the offspring. Thus, the near-infrared laser method may enhance the quality of embryos and contribute to improvements in reproductive technologies in mammals.

Microfluidic analysis of oocyte and embryo biomechanical properties to improve outcomes in assisted reproductive technologies

Measurement of oocyte and embryo biomechanical properties has recently emerged as an exciting new approach to obtain a quantitative, objective estimate of developmental potential. However, many traditional methods for probing cell mechanical properties are time consuming, labor intensive and require expensive equipment. Microfluidic technology is currently making its way into many aspects of assisted reproductive technologies (ART), and is particularly well suited to measure embryo biomechanics due to the potential for robust, automated single-cell analysis at a low cost. This review will highlight microfluidic approaches to measure oocyte and embryo mechanics along with their ability to predict developmental potential and find practical application in the clinic. Although these new devices must be extensively validated before they can be integrated into the existing clinical workflow, they could eventually be used to constantly monitor oocyte and embryo developmental progress and enable more optimal decision making in ART.

Comparison of static culture, micro-vibration culture, and micro-vibration culture with co-culture in poor ovarian responders

Objective

This study was conducted to compare the effects of static culture, dynamic culture, and the combination of dynamic culture with specialized surfaces involving co-culture on human embryonic development. Embryos cultured using conventional static culture (SC) techniques served as a control group. We compared dynamic culture using micro-vibration culture (MVC) and micro-vibration with co-culture (MCoC), in which autologous cumulus cells were used as a specialized surface.

Methods

We conducted a chart review of patients who were treated between January 2011 and November 2014 in order to compare embryonic development rates and pregnancy rates among the groups. Zygotes were cultured in micro-droplets, and embryos were subsequently selected for transfer. Some surplus embryos were cryopreserved, and the others were cultured for blastocyst development. A micro-vibrator was set at the frequency of 42 Hz for duration of 5 seconds per 60 minutes to facilitate embryo development.

Results

No significant differences among the groups were present in patient's characteristics. However, the clinical pregnancy rates were significantly higher in the MVC group and the MCoC group than in the SC group. No significant differences were found in the blastocyst development rate between the SC group and the MVC group, but the blastocyst development rate in the MCoC group was significantly higher than in the SC and MVC groups.

Conclusion

The clinical pregnancy rate was significantly increased by the application of micro-vibration to the embryonic cultures of poor responders. The blastocyst development rate was significantly increased by the application of MCoC to surplus embryos.

Evaluation of Mouse Oocyte In Vitro Maturation Developmental Competency in Dynamic Culture Systems by Design and Construction of A Lab on A Chip Device and Its Comparison with Conventional Culture System

Objective

In conventional assisted reproductive technology (ART), oocytes are cultured in static microdrops within Petri dishes that contain vast amounts of media. However, the in vivo environment is dynamic. This study assesses in vitro oocyte maturation through the use of a new microfluidic device. We evaluate oocyte fertilization to the blastocyct stage and their glutathione (GSH) contents in each experimental group.

Materials and Methods

In this experimental study, we established a dynamic culture condition. Immature oocytes were harvested from ovaries of Naval Medical Research Institute (NMRI) mice. Oocytes were randomly placed in static (passive) and dynamic (active) in vitro maturation (IVM) culture medium for 24 hours. In vitro matured oocytes underwent fertilization, after which we placed the pronucleus (PN) stage embryos in microdrops and followed their developmental stages to blastocyst formation after 3 days. GSH content of the in vitro matured oocytes was assessed by monochlorobimane (MCB) staining.

Results

We observed significantly higher percentages of mature metaphase II oocytes (MII) in the passive and active dynamic culture systems (DCS) compared to the static group (P<0.01). There were significantly less mean numbers of germinal vesicle (GV) and degenerated oocytes in the passive and active dynamic groups compared to the static group (P<0.01). Fertilization and blastocyst formation rate in the dynamic systems were statistically significant compared to the static cultures (P<0.01). There was significantly higher GSH content in dynamically matured oocytes compared to statically matured oocytes (P<0.01).

Conclusion

Dynamic culture for in vitro oocyte maturation improves their developmental competency in comparison with static culture conditions.

Comparison of 2, 5, and 20 % O2 on the development of post-thaw human embryos

PURPOSE

The objective of this study is to investigate the effect of 2, 5, and 20 % O2 on post-thaw day 3 human embryo culture until blastocyst stage.

METHODS

One hundred fifty-five day 3 human embryos were used. One hundred twenty out of 155 embryos were recovered after thawing. Surviving embryos were distributed into 2, 5, or 20 % O2 groups and cultured for 2.5 days. At the end of culture, blastocyst formation was assessed, and then, embryos were collected for RT-qPCR or immunofluorescence analysis.

RESULTS

Using visible blastocoel to define blastocyst formation, 58.7 % (27/46) of surviving day 3 embryos formed blastocyst at 2 % O2, 63.6 % (28/44) at 5 % O2, and 66.7 % (20/30) at 20 % O2. The difference in blastocyst formation rates was not significant. Average blastocyst cell number was 119.44 ± 11.64 at 2 % O2, 142.55 ± 22.47 at 5 % O2, and 97.29 ± 14.87 at 20 % O2. Average apoptotic rate was 4.7 % ± 0.4 % for blastocyst formed at 2 % O2, 3.5 % ± 0.7 % at 5 % O2, and 5.8 % ± 1.1 % at 20 % O2. Apoptosis rate was significantly lower for blastocysts formed at 5 % O2 (p < 0.05). Compared with gene expression levels at 5 % O2, which were arbitrarily set as "1," 20 % O2 is associated with significantly higher expression of BAX (2.14 ± 0.47), G6PD (2.92 ± 1.06), MnSOD (2.87 ± 0.88), and HSP70.1 (8.68 ± 4.19). For all genes tested, no significant differences were found between 2 and 5 % O2.

CONCLUSION

The result suggests that development of cryopreserved human embryos from day 3 to blastocyst stage benefits from culture at 5 % O2.

Microfluidics for High-Throughput Quantitative Studies of Early Development

Developmental biology has traditionally relied on qualitative analyses; recently, however, as in other fields of biology, researchers have become increasingly interested in acquiring quantitative knowledge about embryogenesis. Advances in fluorescence microscopy are enabling high-content imaging in live specimens. At the same time, microfluidics and automation technologies are increasing experimental throughput for studies of multicellular models of development. Furthermore, computer vision methods for processing and analyzing bioimage data are now leading the way toward quantitative biology. Here, we review advances in the areas of fluorescence microscopy, microfluidics, and data analysis that are instrumental to performing high-content, high-throughput studies in biology and specifically in development. We discuss a case study of how these techniques have allowed quantitative analysis and modeling of pattern formation in the Drosophila embryo.

Optimizing the culture environment and embryo manipulation to help maintain embryo developmental potential

With increased use of comprehensive chromosome screening (CCS), the question remains as to why some practices do not experience the same high levels of clinical success after implementation of the approach. Indeed, the debate surrounding the efficacy and usefulness of blastocyst biopsy and CCS continues. Importantly, several variables impact the success of an assisted reproductive technology cycle. Transfer of a euploid embryo is but one factor in an intricate system that requires numerous steps to occur successfully. Certainly, the culture environment and the manipulations of the embryo during its time in the laboratory can impact its reproductive potential. Environmental stressors ranging from culture media to culture conditions and even culture platform can impact biochemical, metabolic, and epigenetic patterns that can affect the developing cell independent of chromosome number. Furthermore, accompanying procedures, such as biopsy and vitrification, are complex and, when performed improperly, can negatively impact embryo quality. These are areas that likely still carry room for improvement within the IVF laboratory.

Microwells support high-resolution time-lapse imaging and development of preimplanted mouse embryos

A vital aspect affecting the success rate of in vitro fertilization is the culture environment of the embryo. However, what is not yet comprehensively understood is the affect the biochemical, physical, and genetic requirements have over the dynamic development of human or mouse preimplantation embryos. The conventional microdrop technique often cultures embryos in groups, which limits the investigation of the microenvironment of embryos. We report an open microwell platform, which enables micropipette manipulation and culture of embryos in defined sub-microliter volumes without valves. The fluidic environment of each microwell is secluded from others by layering oil on top, allowing for non-invasive, high-resolution time-lapse microscopy, and data collection from each individual embryo without confounding factors. We have successfully cultured mouse embryos from the two-cell stage to completely hatched blastocysts inside microwells with an 89% success rate (n = 64), which is comparable to the success rate of the contemporary practice. Development timings of mouse embryos that developed into blastocysts are statistically different to those of embryos that failed to form blastocysts (p-value < 10(-10), two-tailed Student's t-test) and are robust indicators of the competence of the embryo to form a blastocyst in vitro with 94% sensitivity and 100% specificity. Embryos at the cleavage- or blastocyst-stage following the normal development timings were selected and transferred to the uteri of surrogate female mice. Fifteen of twenty-two (68%) blastocysts and four of ten (40%) embryos successfully developed into normal baby mice following embryo transfer. This microwell platform, which supports the development of preimplanted embryos and is low-cost, easy to fabricate and operate, we believe, opens opportunities for a wide range of applications in reproductive medicine and cell biology.

Tauroursodeoxycholic acid improves the implantation and live-birth rates of mouse embryos

We previously demonstrated that tauroursodeoxycholic acid (TUDCA) improved the developmental competence of mouse embryos by attenuating endoplasmic reticulum (ER) stress-induced apoptosis during preimplantation development. Here, we present a follow-up study examining whether TUDCA enhances the implantation and live-birth rate of mouse embryos. Mouse 2-cell embryos were collected by oviduct flushing and cultured in the presence or absence of 50 μM TUDCA. After culture (52 h), blastocysts were transferred to 2.5-day pseudopregnant foster mothers. It was found that the rates of pregnancy and implantation as well as the number of live pups per surrogate mouse were significantly higher in the TUDCA-treated group compared to the control group, but there was no significant difference in the mean weights of the pups or placentae. Thus, we report for the first time that TUDCA supplementation of the embryo culture medium increased the implantation and livebirth rates of transferred mouse embryos.

Use of a novel polydimethylsiloxane well insert to successfully mature, culture and identify single porcine oocytes and embryos

The objective of this study was to evaluate the efficacy of a novel polydimethylsiloxane (PDMS) well-insert system for oocyte in vitro maturation (IVM) and in vitro embryo culture (IVC) in pigs. The PDMS well inserts, consisting of multiple microwells with connecting microchannels, resulted in equivalent blastocyst development compared with standard microdrop culture for IVC. These PDMS well inserts were then evaluated for IVM or IVC in a rocking versus static environment. The rocking environment during both oocyte IVM and embryo culture had detrimental effects on oocyte and embryo development compared with a static environment. Importantly, blastocyst development of oocytes and embryos cultured in the PDMS well inserts in the static environment was equivalent to that of standard microdrops. Further analysis of transcript abundance in blastocysts produced from these different environments revealed that the PDMS well-insert system may produce more viable embryos. In conclusion, this PDMS well-insert system can successfully mature oocytes and culture embryos in an individually-identifiable manner without compromising, and perhaps enhancing, developmental potential.