Improved methods for blastocyst formation and culture

Emerging role of extracellular vesicles in communication of preimplantation embryos in vitro

In vitro, efficient communication between mammalian embryos in groups or between embryos and cocultured somatic cells implies that there is a sender, a message and a receiver that is able to decode the message. Embryos secrete a variety of autocrine and paracrine factors and, of these, extracellular vesicles have recently been implicated as putative messengers in embryo-embryo communication, as well as in communication of the embryo with the maternal tract. Extracellular vesicles (EVs) are membrane-bound vesicles that are found in biofluids and in culture media conditioned by the presence of embryos or cells. EVs carry and transfer regulatory molecules, such as microRNAs, mRNAs, lipids and proteins. We conducted a systematic search of the literature to review and present the currently available evidence regarding the possible roles of EVs in in vitro embryo communication and embryo development. It is important to note that there is limited information available on the molecular mechanisms and many of the biologically plausible functions of EVs in embryo communication have not yet been substantiated by conclusive experimental evidence. However, indirect evidence, such as the use of media conditioned by embryos or by somatic cells with improved embryo development as a result, may indicate that EVs can be an important asset for the development of tailor-made media, allowing better embryo development in vitro, even for single embryo culture.

Stem Cells in Cardiovascular Medicine: the Road to Regenerative Therapies

PURPOSE OF REVIEW

The purpose of this review is to provide a broad overview of current trends in stem cell research and its applications in cardiovascular medicine. Researches on different stem cell sources, their inherent characteristics, and the limitations they have in medical applications are discussed. Additionally, uses of stem cells for both modeling and treating cardiovascular disease are discussed, taking note of the obstacles these engineered interventions must overcome to be clinically viable.

RECENT FINDINGS

Tissue engineering aims to replace dysfunctional tissues with engineered constructs. Stem cell technologies have been a great enabling factor in working toward this goal. Many tissue-engineered products are in development that utilize stem cell technology. Although promising, some refinement must be made to these constructs with respect to safety and functionality. A deeper understanding of basic differentiation and tissue developmental mechanisms is required to allow these engineered tissues to be translated into the clinic.

Autologous embryo–cumulus cells co-culture and blastocyst transfer in repeated implantation failures: a collaborative prospective randomized study

In repeated implantation failure, the co-culture of human embryos with somatic cells has been reported to promote the improvement of embryos quality, implantation and pregnancy rate. It was reported that feeder cells can be more beneficial to the oocyte and embryo by detoxifying the culture medium and supporting embryo development via different pathways. In this study, 432 patients, each with a minimum of three repeated implantation failures, were accepted for a prospective randomized study with or without autologous cumulus cell embryo co-culture and transfer at day 3 or day 5–6. We also investigated the expression of leukaemia inhibitor factor (LIF) and platelet activating factor receptor (PAF-R) on day 3 confluent cumulus cells. The statistic analysis of the data showed significant difference of implantation and clinical pregnancy rates between classical culture and day 3 compared with co-culture and day 5–6 transfer. The molecular analysis showed that cumulus cells express the LIF and the PAF-R genes and confirmed the possible positive role of growth factors and cytokines in early embryo development. Embryo co-culture systems with autologous cells can be beneficial in routine in vitro fertilization for embryo selection and implantation improvement. More molecular investigations need to be done to improve elucidation of the complex dialogue between the embryo and feeder cells prior to implantation and to understand the involved biological function and molecular process during embryo development.

Desenvolvimento de embriões de camundongas após manutenção em diferentes soluções de manipulação

Avaliou-se a eficácia de duas soluções de manipulação (SM) de embriões de camundongas nos estádios de blastocisto inicial (Bin), mórula compacta grau I (McI) e II (McII), distribuídos aleatoriamente em três tratamentos (T), de acordo com a solução de manutenção. No T1 usou-se PBS modificado (controle); no T2, SME e no T3, SME enriquecida. Os embriões foram mantidos durante quatro horas na solução de manutenção e posteriormente classificados quanto ao estádio de desenvolvimento e à qualidade embrionária. Logo após, foram cultivados em meio TCM 199 e classificados novamente quanto ao estádio de desenvolvimento e à qualidade embrionária. A taxa de desenvolvimento dos embriões após manutenção por quatro horas em solução de manipulação foi menor (P<0,05) nos embriões do controle, comparada à de embriões do SME e SME enriquecida, diferença esta não observada (P>0,05) após o cultivo in vitro. Os embriões McII do T3 tiveram maior desenvolvimento (P<0,05) em relação aos embriões do T1 e T2, indicando o efeito benéfico do enriquecimento da solução SME. Conclui-se que as soluções de manipulação SME e SME enriquecida influenciaram beneficamente o desenvolvimento de embriões

Uterine dynamics: impact on the human reproduction process

This review assesses data on the possible relationship between the contractility of the non-pregnant uterus and the human reproduction process. The possibility of assessing non-invasively uterine contractility using ultrasound scans has improved understanding of hormone regulation and the influence of uterine contractility on the human embryo implantation process in both natural and ovarian stimulation cycles. Contractions of the non-pregnant uterus are influenced by ovarian hormones and, presumably, partake in the in-vivo fertilization and embryo implantation processes in humans. Approaches aimed at either stimulating or inhibiting uterine contractions could be instrumental in improving pregnancy rates after the use of assisted reproductive technologies.

Release of DEFB126 from macaque sperm and completion of capacitation are triggered by conditions that simulate periovulatory oviductal fluid

Capacitation of macaque sperm in vitro has been achieved efficiently only with the addition of both cyclic nucleotides and methylxanthines. The use of these exogenous sperm activators clouds an understanding of the normal mechanisms underlying capacitation and may slow early embryo development following in vitro fertilization (IVF). We demonstrate that culture medium which simulates periovulatory oviductal fluid with respect to bicarbonate (HCO(3)(-)) and glucose concentration induces capacitation in a high percentage of macaque sperm as determined by the ability of sperm to undergo both the release of coating protein DEFB126 and the zona pellucida-induced acrosome reaction (AR). Few sperm were able to undergo the AR following 6 hr incubation in medium containing either 35 mM HCO(3)(-) (approximately 7.2 pH) or 90 mM HCO(3)(-) (approximately pH 7.8) with 5 mM glucose. When glucose concentration was lowered to 0.5 mM to match levels reported for women at midcycle, the AR rate increased significantly in sperm incubated in both levels of HCO(3)(-), indicating that glucose interferes with sperm responsiveness to increasing HCO(3)(-) concentration observed in the primate oviduct during ovulation. Even greater synchronization of capacitation could be achieved with nonphysiologic extremes of alkalinity or energy substrate deprivation. In the latter case, sperm achieved high rates of IVF. A shift in pH from 7.2 to 7.8 in a HEPES-buffered medium was sufficient to remove DEFB126 from the surface of most sperm after only 3 hr. The loss of DEFB126 from sperm under periovulaory fluid conditions has implications for the timing of release of sperm from the oviductal reservoir.

[Blastocyst quality criteria]

Embryo culture to the blastocyst stage has progressed enormously with the new generation of acellular culture media, or sequential media. The main advantages of embryo transfer at the blastocyst stage are that it provides a natural embryo selection during culture, or a selection using preimplantation diagnosis, it provides better conditions for SET, avoiding multiple pregnancies and overcoming repeated IVF failures by improving embryo selection. The risks are failing to select a single blastocyst or obtaining a limited number of frozen blastocysts, with reduced survival after thawing. However, prolonged embryo culture seems to be good practice for day 3 embryos with delayed development, and blastocyst transfer. More effective at day 5 than at day 6.

Vascular endothelial growth factor level changes during human embryo development in culture medium

OBJECTIVE

Implantation is a complex phenomenon consisting of the first strong contact between embryo and endometrium. Recent studies have demonstrated that this process is dependent not only on the 'readiness' of the endometrium, but also on complex interactions between endometrial and embryonic tissues that cross-talk by means of different molecules (growth factors, cytokines, vasoactive factors). Investigations performed on human blastocysts indicate a role for vascular endothelial growth factor (VEGF) in these processes. The aim of the present study was to investigate VEGF levels at different stages in human embryo culture medium.

STUDY DESIGN

We selected 20 women among patients undergoing assisted reproduction with the in vitro fertilization-blastocyst transfer protocol. The oocytes were inseminated by intracytoplasmic sperm injection. For each patient, approximately two cultures of four microinjected oocytes (and then of four embryos) were performed. Each culture of four oocytes/embryos was placed in one dish to increase the probability to detect small VEGF concentrations.

RESULTS

Results showed significantly higher VEGF levels in the medium at blastocyst stage (12.16 +/- 2.80 pg/ml) compared with embryos at pronuclear stage (13.58 +/- 2.32 pg/ml) and microinjected oocytes (12.80 +/- 3.45 pg/ml).

CONCLUSIONS

An important VEGF synthesis by blastocysts occurs during human embryo development.

Mammalian embryo co-culture: Trials and tribulations of a misunderstood method

Embryo-somatic cell co-culture was devised over 40 years ago in an attempt to improve the development and viability of mammalian preimplantation embryos generated and cultured in vitro. While initial endeavours were successful in this respect, other studies soon highlighted a number of significant long-term detrimental impacts of this approach. Surprisingly little is known about the mechanisms underlying the beneficial effects of co-culture, although the production of embryotrophic compounds, modulation of nutrient profile, protection against culture-induced stress and/or toxin clearance are all contenders. The extent to which the inadvertent exposure of embryos to serum accounts for many of these effects remains open to question. Although the popularity of somatic cell co-culture has recently declined in favour of the use of sequential media due to concerns associated with its risk of disease transmission and long-term sequelae, we argue that complete dismissal of this technique is ill advised, given that our limited understanding of basic somatic cell interactions has prevented us from fully exploiting its potential. In this respect, there is some merit in focussing future research strategies based on reconstructed maternal tract tissue. Although the use of co-culture in clinical practice is unacceptable and its implementation in domestic species for commercial purposes should be viewed with diffidence, this technique can still provide a wealth of information on the development of novel, more physiological embryo in vitro culture systems. The proviso for acquiring such information is to gain a fuller understanding of the culture requirements/biochemistry of somatic cells and their interaction with the early conceptus.

Development, chromosomal composition, and cell allocation of bovine cloned blastocyst derived from chemically assisted enucleation and cultured in conditioned media

Treatment of in vitro matured bovine oocytes with colcemid results in a membrane protrusion that contains maternal chromosomes, which can be easily removed by aspiration. Four experiments were designed to evaluate the overall and temporal effects of conditioned medium (CM) by bovine cumulus cells on development of nuclear transfer (NT) bovine embryos and to examine the chromosomal composition and allocation of inner cell mass (ICM) and trophectoderm (TE) of the subsequent blastocysts. The nuclear transfer embryos were cultured in various CR1aa media conditioned by preculture with bovine cumulus cells. Development to the blastocyst stage in BSA-containing CM (BCM) and serum-containing CM (SCM) were similar to co-culture group (24-30%). The 24 hr-conditioned BCM yielded higher blastocyst development than 48 and 72 hr-conditioned BCM. Temporary exposure of embryos to BCM and SCM followed by CR1aa was also studied. Morula and blastocyst development were not different among the groups cultured in BCM for 72, 96, and 168 hr, but were significantly higher (P < 0.01) than groups exposed to BCM for 24 and 48 hr, respectively. Blastocyst development in SCM for 24 hr (29%), 96 hr (25%), and 168 hr (27%) were much higher (P < 0.05) than those in SCM for 48 hr (12%) and 72 hr (10%). The analyses of chromosomal composition of the resulting blastocysts indicate approximately 80% of the blastocysts cultured in CR1aa with co-culture or groups initially exposed to BCM for 24 hr followed by culture in CR1aa were diploid. However, the incidence of diploidy were only 36-60% in SCM-cultured groups and groups cultured in BCM beyond 48 hr. Conditioned media did not affect the allocation of ICM and TE in the blastocyst. No difference was found in the ratio of inner cell mass to total cells in co-culture, BCM or SCM groups (0.424, 0.441, and 0.473, respectively). In conclusion, bovine cumulus cell-CM and CR1aa with co-culture supported comparable development and blastocyst ICM:total cell ratio of bovine NT embryos. However, CM affected the blastocyst chromosomal composition and induced higher mixploidy.

Is there still a place for co-cultures in the era of sequential media?

Co-cultures have been advocated in assisted reproduction owing to the inadequacy of simple media to support embryo development beyond the cleavage stage. Different human and non-human cells and cell lines have been used for co-cultures. High rates of blastocyst formation have been reported with the use of co-cultures, and they have been proposed as a salvage treatment option in couples with repeated implantation failures. Since the advent of complex sequential media, which yield very high blastocyst formation and blastocyst implantation rates, the need for co-cultures has been questioned. Upon review of the literature, it is evident that well-designed randomized studies that compare co-cultures with simple or sequential media do not exist. Progression to the blastocyst stage for cleavage stage embryos appears to be similar, if not better, for embryos that are cultured in modern sequential media, rendering the use of co-cultures obsolete. Furthermore, there is no consensus regarding the necessity of sequential media, as similar results have been obtained with a single medium formulation that supports all stages of the preimplantation period. Whether co-cultures are beneficial in patients with repeated implantation failures, however, should be investigated in randomized trials. Co-cultures still serve as powerful tools for understanding embryo metabolism. Furthermore, co-cultures may be instrumental in studying expression of implantation-related genes and embryo-endometrium interaction.

Hormonal regulation of implantation

Implantation is a complex process that requires synchronization between the embryo and a receptive endometrium. Hormones, such as the female sex steroids, prostaglandins, and peptide hormones, regulate the cellular and molecular mediators of endometrial receptivity, which include pinopodes, cell adhesion molecules, cytokines, homeobox genes, and growth factors. These mediators can be altered, despite the presence of normal hormone levels and endometrial histology; this limits the usefulness of the luteal phase endometrial biopsy. Therefore, analysis of markers of endometrial receptivity may predict successful implantation better. Elevated androgen and estrogen levels, as seen with polycystic ovary syndrome and controlled ovarian hyperstimulation, respectively, also can have detrimental effects on the endometrium, and therefore, implantation.

Cryopreservation of IVF embryos: which stage?

Embryo freezing is a mandatory tool in IVF technology as controlled ovarian hyperstimulation usually leads to extra embryos which are not transferred. One dilemma is the embryonic stage at which the embryos are to be frozen. Early stage freezing (PNs or cleavage stage) leads to a two step selection: at the time of thawing and a few hours or a day after. Then the recovering embryos are submitted to the classical in vitro developmental arrests in relation with maternal, paternal and cytogenetic factors. The "take home baby rate" per frozen embryo is low, rarely over 5%. Blastocyst have overcome the blocks in vitro: a first selection has already been made. The quality of freezing at this stage depends greatly on the culture conditions. It allows freezing of fewer embryos, but with higher yields: a >10% take home baby rate can be expected. It is clear to us that vitrification, beside the technical problems, has to be handled with care, especially if ethylene glycol (EG) is used. Metabolic products of EG might have negative effects on organogenesis.

Relationship between peak serum estradiol levels and treatment outcome in in vitro fertilization cycles after embryo transfer on day 3 or day 5

OBJECTIVE

To examine the relationships between peak serum estradiol (E(2)) levels and treatment outcome in in vitro fertilization (IVF) cycles after embryo transfer (ET) on day 3 or day 5.

DESIGN

Retrospective analysis of 697 IVF-ET cycles between January 1999 and December 2001.

SETTING

A university-affiliated assisted reproduction program.

PATIENT(S)

Infertile patients undergoing IVF-ET cycles.

INTERVENTION(S)

Peak E(2) concentration in serum was determined on the day of human chorionic gonadotropin (hCG) administration. The IVF-generated embryos were cultured for 2 days until transfer on day 3. If more than four 8-cell embryos were present on day 3, embryo culture was continued until day 5 for blastocyst transfer.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy rates.

RESULT(S)

High peak E(2) levels did not adversely affect treatment outcome. After the cycles were divided according to the day of ET, high peak E(2) levels were associated with improved pregnancy rates after ET on day 5 but not on day 3.

CONCLUSION(S)

Increasing peak E(2) levels in IVF cycles are associated with improved pregnancy rates after ET on day 5.

Fundamentals of human embryonic growth in vitro and the selection of high-quality embryos for transfer

Knowledge of the nature of embryo growth, and the handling and scoring of quality in human embryos are significant aspects for embryologists in IVF clinics. This review describes the formation, growth and maturation of human oocytes, many aspects of fertilization in vitro, embryonic transcription during preimplantation stages, and the formation of polarities, timing controls, role of mitochondria and functions of endocrine and paracrine systems. Modern concepts are fully discussed, together with their significance in the practice of IVF. This knowledge is essential for the correct clinical care of human embryos growing in vitro, especially in view of their uncharacteristic tendency to vary widely in implantation potential. Underlying causes of such variation have not been identified. Stringent tests must be enforced to ensure human embryos develop under optimal conditions, and are scored for quality using the most advanced techniques. Optimal methods of culture are described, including methods such as co-culture introduced to improve embryo quality but less important today. Detailed attention is given to quality as assessed from embryonic characteristics determined by timers, polarities, disturbed embryo growth and anomalous cell cycles. Methods for classification are described. Approaches to single embryo transfers are described, including the use of sequential media to produce high-quality blastocysts. These approaches, and others involved in surgical methods to remove fragments, transfer ooplasm or utilize newer approaches such as preimplantation diagnosis of chromosomal complements in embryos are covered. New outlooks in this field are summarized.

Apoptosis in mammalian preimplantation embryos: regulation by survival factors

The formation of a developmentally competent mammalian blastocyst requires the transition from a unicellular state, the fertilized zygote, to a differentiated multicellular structure. In common with other developing organisms, generation of the required cell population involves the processes of cell division, differentiation and cell death, all of which can be regulated by peptide growth factors. Cell death in the preimplantation embryo occurs by apoptosis and, by analogy with other systems, may serve to eliminate unwanted cells during the critical developmental transitions that take place during this period. Cells may be eliminated because they are abnormal or possess defects, including damaged DNA or chromosomal abnormalities. At the early cleavage stages, apoptosis may be associated with activation of the embryonic genome and may contribute to the blastomere fragmentation commonly observed in human IVF embryos. The major wave of apoptosis occurs in a number of species in the inner cell mass of the blastocyst, as identified using nuclear labelling including terminal transferase-mediated dUTP nick end labelling (TUNEL) and fluorescence and confocal microscopy. Apoptosis may protect the integrity and cellular composition of the inner cell mass, by eliminating damaged cells or possibly those with an inappropriate phenotype. Preimplantation embryos express genes involved in the regulation and execution of apoptosis and their cells can undergo this default pathway in the absence of exogenous survival signals. Evidence is now accumulating from several species that apoptosis in the embryo is regulated by soluble peptide growth factors acting as survival factors in an autocrine or paracrine manner. To date, these include transforming growth factor alpha and members of the insulin-like growth factor family. Apoptosis may also be affected by environmental factors, including culture conditions and the composition of media. The regulation of apoptosis in the preimplantation embryo is likely to be of critical importance for both embryo viability and for later development, since the cells of the inner cell mass give rise to the fetus and carry the germ line.

Comparison of G1.2/G2.2 and Sydney IVF cleavage/blastocyst sequential media for the culture of human embryos: a prospective, randomized, comparative study

OBJECTIVE

To compare two commercially available sequential media, G1.2/G2.2 and Sydney IVF cleavage/blastocyst media, as supports for human embryo culture.

DESIGN

Prospective randomized study.

SETTING

University-based IVF clinic.

PATIENT(S)

Two hundred forty-nine patients undergoing IVF treatment for the first or second time, randomly allocated at the time of oocyte retrieval, to either culture in G1.2/G2.2 or Sydney IVF media.

INTERVENTION(S)

Oocyte recovery, IVF or intracytoplasmic sperm injection, embryo culture, transfer on day 3 or day 5/6.

MAIN OUTCOME MEASURE(S)

Developmental stage on day 3, blastocyst rate, pregnancy outcome as assessed by beta hCG positive test, implantation rates, and ongoing pregnancies.

RESULT(S)

Embryos cultured in G1.2/G2.2 media displayed a faster kinetics of cleavage, compaction, blastulation, and hatching, but a lower day 3 embryo quality than those grown in Sydney IVF media. For patients with at least five embryos, G1.2/G2.2 media yielded higher implantation rates (26.2%) in our day 3 embryo transfer program when compared to Sydney IVF medium (15.5%), whereas similar implantation rates were obtained for day 5/6 embryo transfer for both media (43.1% and 36.1%, respectively).

CONCLUSION(S)

In our day 3 embryo transfer program, G1.2/G2.2 media were superior to Sydney IVF media, whereas both media yielded similar outcomes in our blastocyst transfer program.

Establishment of a ciliated epithelial cell line from human Fallopian tube

Human tubal epithelial cells in primary culture were transfected with simian virus 40 (SV40) large T antigen plasmid, and an immortalized ciliated cell line, named as NT/T-S, was established without crisis. Transmission electron microscopy proved that NT/T-S cells had cilia, microvilli, junctional complexes, rough endoplasmic reticula, free ribosomes and microtubules. NT/T-S cells were evaluated preliminarily on the basis of co-culture study using surplus embryos at the 4- to 8-cell stage in our IVF and embryo transfer programme. All of the 133 embryos had >/=10% fragments (based on the surface area) and were unworthy of cryopreservation. Up to 57% (16/28) of the embryos with 10-30% fragments reached the blastocyst stage by co-culture. In contrast, blastocyst formation was observed in <10% of the control embryos, some of which were co-cultured with NFL/T cells (the immortalized human fetal liver epithelial cells) (1/16), and the others were incubated with the co-culture medium alone (1/18). Various cytokines/growth factors such as leukaemia inhibitory factor (LIF), interleukin (IL)-6, IL-8 and basic fibroblast growth factor were secreted by NT/T-S cells as well as by the tubal epithelial cells in primary culture. The establishment of a ciliated cell line will provide a valuable resource for the further studies of the Fallopian tube in the early events of pregnancy.

Assisted reproductive technology (ART) in humans: facts and uncertainties

Since the first in vitro fertilization (IVF) in human, the number of patients using Assisted Reproductive Technologies (ART) has increased tremendously. ART technologies have increased in number and their spectrum has also widened. The first IVF babies are now more than 20 years old. All the retrospective analyses have demonstrated that the obstetrical and pediatrical impact has not really affected single births. The main problems observed occur with multiple pregnancies, including high costs for the couples and for society. The decrease in the number of embryos transferred has improved the situation and moreover does not impair the final results. IntraCytoplasmic Sperm Injection (ICSI) is a more debatable and questionable technique with a real negative genetic impact. The main problem is chromosome abnormalities more specifically related to the sex chromosomes. The question of a systematic genetic work-up on the patients entering ICSI programs is discussed. No negative impact of cryopreservation has been demonstrated even though some controversy arises from time to time. Pre-implantation Genetic Diagnosis (PGD) is now a interesting tool for patients carrying genetic defects. Blastocyst biopsy now has a future role in reproductive medicine. Gender selection through sperm sorting is also now a reality. As with the other developing bio-technologies related to reproduction, there are ethical questions. The decisions concerning these technologies do not belong solely to scientists but are rather a matter for society to decide.