Human embryonic behavior in a sequential human oviduct-endometrial coculture system

The expression of activins, their type II receptors and follistatin in human Fallopian tube during the menstrual cycle and in pseudo-pregnancy

BACKGROUND

The Fallopian tube (FT) is the site of fertilization and early embryonic development. We have previously reported the expression of activins, their receptors and follistatin by the FT. Here, our aim was to study the expression of tubal activins, their type II receptors and follistatin during the menstrual cycle and following exposure to hCG in vivo.

METHOD

A set of 30 FTs were collected from cycling women (n = 12) at different stages of the cycle (n = 4 in each stage) and pseudo-pregnant women (n = 3) at the time of hysterectomy for benign disease. The pseudo-pregnant women were injected with hCG in the days leading up to hysterectomy, and pseudo-pregnancy was confirmed by the persistence of amenorrhea, the presence of corpus luteum and decidualization of the endometrium. FT specimens were examined using immunohistochemistry and quantitative RT-PCR.

RESULTS

The expression of activin βA- and βB-subunits, activin type IIA and IIB receptors, and follistatin varied throughout the menstrual cycle, being lowest in the follicular phase and highest in the luteal phase. These results were demonstrated at the mRNA and protein level by quantitative RT-PCR and immunohistochemistry (P< 0.05). HCG injection rescued the expression of the candidate molecules from falling to the follicular stage levels but the expression remained lower than in the luteal phase.

CONCLUSIONS

We suggest that activins play a role in tubal physiology and early embryonic development. Additionally, exposure of the tubal epithelium to hCG modulates the expression of tubal activins.

Influence of cumulus cell coculture and cumulusaided embryo transfer on embryonic development and pregnancy rates

OBJECTIVE

In this study, we aimed to evaluate the influence of autologous cumulus oocyte complex (COC) coculture on embryonic development and quality, and investigate the implantation and pregnancy rates after cumulus-aided embryo transfer in the ICSI-ET cycles.

MATERIAL AND METHODS

Ninety five consecutive infertile women undergoing their first cycle of IVF teratment were included in the study. The cases were divided into two groups. Group 1 consisted of 48 women undergoing ICSI, along with autologous cumulus embryo coculture and cumulus-aided emryo transfer. Group 2 comprised 47 consecutive patients who consented to undergo ICSI and in whom autologous cumulus embryo coculture and cumulus-aided embryo transfer were not performed. Implantation and pregnancy rates were compared between the two groups.

RESULTS

The demographic data and controlled ovarian hyperstimulation parameters were similar in the two groups. The fertilization and cleavage rates were found to be higher in group 1 when compared with group 2 (p=0.03 and 0.001, respectively). There were no statistical significant differences for the implantation and clinical pregnancy rates between the two groups.

CONCLUSION

Usage of autologous COCs as coculture may improve fertilization and cleavage rates. However, cumulus-aided embryo transfer does not produce an increase in implantation and pregnancy rates.

Identification of a novel role for endothelins within the oviduct

Endothelins were first identified as potent vasoactive peptides; however, diversity in the biological function of these hormones is now evident. We have identified a novel role for endothelins: a requirement for these peptides within the oviduct during fertilization and/or early embryo development. In vivo, treatment after ovulation with a dual endothelin receptor antagonist (tezosentan) decreased the number of two-cell embryos that could be collected from within the oviducts. In vitro fertilization experiments showed that gamete viability and their ability to fertilize were not affected by treatment with this antagonist, suggesting that the effect observed in vivo was mediated by the oviduct itself. Expression of mRNA for all three isoforms of the endothelins and both receptor subtypes was detectable within the oviduct. Expression of mRNA for endothelin-3 was regulated by gonadotropins in epithelial cells of the oviduct and increased specifically within the isthmus of this structure. Immunostaining revealed localization of both endothelin receptors A and B to the columnar epithelial cells within the oviduct, suggestive of a local role for endothelins in the regulation of epithelial function and ultimately oviductal secretions. A microarray analysis revealed three likely endothelin-regulated protein networks for future analysis: the TGFbeta, IL-10, and CCAAT/enhancer-binding protein superfamilies. Overall, these results suggest a novel and requisite role for endothelins within the oviduct during fertilization and/or early embryo development.

Oviductal cells and early conception

The ability to bypass the oviduct by fertilizing human oocytes in vitro and then transferring the ensuing embryos into the uterine environment to produce pregnancies that can be carried to term (assisted reproductive technology, ART) has made the real functional significance of the fallopian tube come under debate. The question has been raised as to whether the oviduct is a simple conduit, providing for the transport of gametes and embryos, or whether it has any functional relevance to early conception. In the field of ART, some reports claim that transfer of embryos either to the uterus or to the oviduct yield similar results, while a greater amount of evidence confirms that tubal transfers are associated with higher pregnancy and take home baby rates, suggesting that unknown factors in the oviduct favour fertilization and embryo viability. This review attempts to provide some answers to questions about the role of oviductal cells in vivo during early conception and in vitro in the field of ART.

Teratoma formation by human embryonic stem cells: evaluation of essential parameters for future safety studies

Transplantation of human embryonic stem cells (hESC) into immune-deficient mice leads to the formation of differentiated tumors comprising all three germ layers, resembling spontaneous human teratomas. Teratoma assays are considered the gold standard for demonstrating differentiation potential of pluripotent hESC and hold promise as a standard for assessing safety among hESC-derived cell populations intended for therapeutic applications. We tested the potency of teratoma formation in seven anatomical transplantation locations (kidney capsule, muscle, subcutaneous space, peritoneal cavity, testis, liver, epididymal fat pad) in SCID mice with and without addition of Matrigel, and found that intramuscular teratoma formation was the most experimentally convenient, reproducible, and quantifiable. In the same experimental setting, we compared undifferentiated hESC and differentiated populations enriched for either beating cardiomyocytes or definitive endoderm derivatives (insulin-secreting beta cells), and showed that all cell preparations rapidly formed teratomas with varying percentages of mesoderm, ectoderm, and endoderm. In limiting dilution experiments, we found that as little as two hESC colonies spiked into feeder fibroblasts produced a teratoma, while a more rigorous single-cell titration achieved a detection limit of 1/4000. In summary, we established core parameters essential for facilitating safety profiling of hESC-derived products for future therapeutic applications.

Live births in poor prognosis IVF patients using a novel non-contact human endometrial co-culture system

Patients with repeated implantation failures or poor embryo quality may benefit from embryo culture using the co-culture technique; growth factors secreted by co-culture cells may act as survival factors. Autologous endometrial co-culture has been suggested as a safe alternative to animal cells for co-culture of human embryos. However, the technique is fairly labour intensive and its effectiveness can vary from patient-to-patient. This study presents clinical outcome data on a novel noncontact co-culture system using a human endometrial cell line rather than autologous tissue. Embryos from 316 poor prognosis patients with repeated IVF failures, previous cycles with poor embryo quality or advanced maternal age were cultured in Transwell chambers with a monolayer of endometrial cells. The clinical pregnancy rate in patients less than 39 years of age was 53% and for patients aged between 39 and 42 years it was 33%. To date, 76 patients have delivered 111 healthy infants with no congenital anomalies and 18 pregnancies are ongoing. This is the first report on the potential benefits of a non-contact co-culture system in the IVF laboratory. This study shows that an established human endometrial cell line can be used to obtain the benefits of co-culture without the potential disadvantages associated with using autologous endometrial tissue.

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.

Human blastocyst culture and derivation of embryonic stem cell lines

Human embryonic stem cell (hESC) biology is expected to revolutionize the future of medicine by the provision of cell-based therapies for the treatment of a variety of deliberatig diseases. The tremendous versatility of hESCs has reinforced this hope. To understand the biology of these mysterious cells and attempt to differentiate them into desirable tissues, bona fide hESCs that maintain their stability with time are required for research and clinical application. This review discusses the various protocols to derive and propagate hESCs from high quality embryos. The nature and properties of hESCs are also described together with unanswered questions that need to be addressed if this science is to be taken to the bedside.

Cell therapy and the safety of embryonic stem cell-derived grafts

Recent developments in the identification, in vitro culture and differentiation of stem cells point to the unprecedented potential of these cells, or their derivatives, to cure degenerative disorders. Human embryonic stem cells (hESC) offer the particular advantage of prolonged proliferative capacity and great versatility in the lineages that can be formed in culture. Translating these advantages into clinical benefits faces many challenges, including efficient differentiation into the desired cell type(s), maintaining genetic stability during long-term culture and, finally, ensuring the absence of potentially tumorigenic hESC from the final product. It is this final safety issue that will form the focus of this review.

Human Embryo Culture

Human embryonic stem cells (hESCs) are derived from preimplantation embryos. Approximately 60% of human embryos are blocked during in vitro development. Although statistics are inconclusive, experience demonstrates that hESCs are more effectively derived from high-quality embryos. In this way, optimal human embryo culture conditions are a crucial aspect in any derivation laboratory. Embryos can be cultured solely with sequential media or cocultured on a monolayer of a given cell type. This chapter explores general aspects of human embryonic development, the concept of sequential culture and coculture, and specific protocols and procedures in which the authors are experienced, including the results obtained.

Interleukin-1 system messenger ribonucleic acid and protein expression in human fallopian tube may be associated with ectopic pregnancy

OBJECTIVE

To investigate the interleukin-1 (IL-1) system mRNA and protein expression in human fallopian tubes with ectopic pregnancies.

DESIGN

A controlled study.

SETTING

Clinical and academic research setting in a university medical center.

PATIENT(S)

Women undergoing salpingectomy for fallopian tube with ectopic pregnancy and women undergoing tubal ligation.

INTERVENTION(S)

Paired segments of human fallopian tubes containing an ectopic pregnancy and parafallopian tube segments adjacent to the ectopic pregnancy were collected from five women undergoing laparoscopic salpingectomy. Segments of fallopian tubes from four women undergoing tubal ligation were used as control tissues. Quantitative competitive polymerase chain reaction (QC-PCR) and immunohistochemistry were performed.

MAIN OUTCOME MEASURE(S)

The differences of IL-1 system mRNA and the ratio of IL-1beta to IL-1 receptor antagonist (IL-1ra) in both fallopian tubes with ectopic pregnancies and normal controls were analyzed.

RESULT(S)

A complete IL-1 system mRNA and protein expression was identified in both fallopian tubes with ectopic pregnancies and normal controls. As QC-PCR demonstrated, IL-1beta mRNA expression was decreased, and IL-1ra and IL-1 receptor type 1 were increased in fallopian tubes with ectopic pregnancies in comparison with normal control tubes. In para-ectopic tubes, IL-1 receptor type 1 mRNA was statistically significantly increased in comparison with normal controls. There was a lower ratio of IL-1beta to IL-1ra at mRNA in fallopian tubes with ectopic pregnancies.

CONCLUSION(S)

These results suggest that an inappropriate ratio of IL-1beta to IL-1ra and a higher expression of its receptor in fallopian tubes may possibly be implicated to the implantation of an ectopic pregnancy in the oviduct.

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.

Embryotrophic factor-3 from human oviductal cells affects the messenger RNA expression of mouse blastocyst

Our previous results showed that embryotrophic factor-3 (ETF-3) from human oviductal cells increased the size and hatching rate of mouse blastocysts in vitro. The present study investigated the production of ETF-3 by an immortalized human oviductal cell line (OE-E6/E7) and the effects of ETF-3 on the mRNA expression of mouse embryos. The ETF-3 was purified from primary oviductal cell conditioned media using sequential liquid chromatographic systems, and antiserum against ETF-3 was raised. The ETF-3-supplemented Chatot-Ziomek-Bavister medium was used to culture Day 1 MF1 x BALB/c mouse embryos for 4 days. The ETF-3 treatment significantly enhanced the mouse embryo blastulation and hatching rate. The antiserum, at concentrations of 0.03-3%, abolished the embryotrophic effect of ETF-3. Positive ETF-3 immunoreactivity was detected in the primary oviductal cells, OE-E6/E7, and blastocysts derived from ETF-3 treatment. Vero cells (African Green Monkey kidney cell line), fibroblasts, and embryos cultured in control medium did not possess ETF-3 immunoreactivity. The mRNA expression patterns of the treated embryos were studied at the blastocyst stage by mRNA differential display reverse transcription-polymerase chain reaction (DDRT-PCR). The DDRT-PCR showed that some of the mRNAs were differentially expressed after ETF-3 treatment. Twelve of the differentially expressed mRNAs that had high homology with cDNA sequences in the GenBank were selected for further characterization. The differential expression of seven of these mRNAs (ezrin, heat shock 70-kDa protein, cytochrome c oxidase subunit VIIa-L precursor, proteinase-activated receptor 2, eukaryotic translation initiation factor 2beta, cullin 1, and proliferating cell nuclear antigen) was confirmed by semiquantitative RT-PCR. In conclusion, immortalized oviductal cells produce ETF-3, which influences mRNA expression of mouse blastocyst.

Improved development of very-poor-quality human preembryos by coculture with human fallopian ampullary cells

PURPOSE

To determine whether a confluent culture of fallopian ampullary epithelial cells, taken from women at the end of their reproductive life, is capable of rescuing very-poor-quality preembryos from cleavage arrest and/or degeneration.

METHODS

Human preembryos. rejected for transfer or freezing because of very poor quality, and arrested within 24 h of cleavage, were cultured for 5 days in medium alone or over a confluent culture of fallopian ampullary epithelia] cells. Morphological criteria were utilized to assess preembryo degeneration and stage of development.

RESULTS

The described coculture rescued preembryos from degeneration, enhancing development to the blastocyst stage 2.2-fold, compared with cultures in medium alone. Furthermore, fully expanded and hatching blastocysts were observed only under coculture conditions.

CONCLUSIONS

Very-poor-quality human preembryos may be rescued from degeneration, and their growth and development dramatically improved, when cocultured with a confluent culture of fallopian ampullary epithelial cells.

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.

A historical perspective of the clinical evolution of the assisted reproductive technologies

The practice of assisted reproduction technology today is the result of the dedicated patient care, observation, research, and experimentation undertaken by previous generations of physicians. The building blocks of progress have been assembled over past decades, by scientists whose primary objective has been to push forward the frontiers of knowledge, in order to offer more effective methods of infertility treatment. And fortunately that process continues today. Amongst the many scientific developments that have led to the modern practice in assisted reproductive technology, a small number stand out as having had a unique importance. This historical review redraws the path through which in vitro fertilization went from an experimental to an accepted infertility treatment.

Coculture of human embryos with autologous human endometrial epithelial cells in patients with implantation failure

We have developed a coculture system with autologous human endometrial epithelial cells (AEEC) that retained many features of human endometrial epithelium. Implantation failure (IF; >3 previous cycles failed with 3-4 good quality embryos transferred) is a distressing condition in which 2-day embryo transfer repetition is the routine option. The objective of this study was to investigate the basics and to evaluate prospectively the clinical value of embryo coculture on AEEC and blastocyst transfer with their own oocytes [in vitro fertilization (IVF) patients] or with donated oocytes (oocyte donation patients) compared to a routine day 2 embryo transfer for patients with IF. Scanning electron microscopy and mouse embryo assays demonstrate that EEC from fertile and IF patients were morphologically and functionally similar; similar findings were observed in EEC obtained from fresh or frozen endometria. Clinically, 168 IVF cycles were performed in 127 patients with 3.8+/-0.2 previously failed cycles, and 80 cycles were performed in 57 patients undergoing oocyte donation with 3.0+/-0.2 previously failed cycles. Twenty IVF patients and 15 ovum donation patients with 3 previously failed cycles in whom a 2-day embryo transfer was performed were used as controls. In 88% of ovum donation cycles, at least 2 blastocysts were available for transfer, with 60.1% blastocyst formation; 2.2+/-0.1 blastocysts were transferred/cycle, and 36 pregnancies (determined by fetal cardiac activity) were obtained (32.7% implantation and 54.5% pregnancy rates). In 168 IVF cycles, 8.1+/-0.2 embryos/cycle started coculture, resulting in 49.2% blastocyst formation; 2.3+/-0.2 blastocysts were transferred/cycle, and 29 clinical pregnancies were obtained (11.8% implantation and 20.2% pregnancy rates). Fifteen cycles were canceled (9%). In oocyte donation patients with IF undergoing 2-day embryo transfer, implantation and pregnancy rates were significantly lower (4.5% and 13.3%; P < 0.01) than with coculture; however, in IVF patients with IF, results with day 2 transfer (10.7% and 35%) were similar to those with coculture. The present study demonstrates that coculture of human embryos with AEEC and blastocyst transfer is safe, ethical, and effective and constitutes a new approach to improve implantation in patients with IF undergoing ovum donation, but not in IVF patients.

Coculture with homologous oviductal cells improved the implantation of human embryos--a prospective randomized control trial

PURPOSE

The efficacy of homologous oviductal cell coculture on the success of a human in vitro fertilization program was investigated in a prospective randomized control clinical trial.

METHODS AND RESULTS

One hundred eighty-one couples were randomized into the control and the coculture groups. Pronuclear-stage zygotes were either cultured in Earles' balanced salt solution supplemented with 15% preovulatory serum (control) or cultured with human oviductal cells (coculture) for 24 hr before embryo transfer. There was no difference in the age of the patients, indication for treatment, number of oocyte retrieved or fertilized, or number of embryo replaced between the two groups. The pregnancy rates per transfer for the control and the coculture group were 12.8 and 19.3%, respectively. The number of viable fetus was significantly higher (P < 0.01, chi-square test) in the coculture group (25/264) than in the control group (8/262). The coculture group also showed a higher multiple pregnancy rate, lower abortion rate, and more spare embryos suitable for cryopreservation.

Coculture of human spermatozoa with reproductive tract cell monolayers can enhance sperm functions better than coculture with Vero cell monolayers

PURPOSE

In order to develop a better system for support of human sperm function in vitro, we conducted studies to evaluate whether reproductive tract cells are better than non-reproductive tract cells as an adjunt in that regard.

METHODS

Human spermatozoa were cocultured with Vero cells, with human oviduct cells and endometrial cells, and without cells (control) for either 1, 4, or 24 hr. Sperm motility was then analyzed with a computer-aided sperm analyzer (CASA-Hamiliton Thron, HTM IVOS Motility Analyzer). Aliquots of spermatozoa incubated for 24 hr were also stained with Hoechst 33258 and FITC-PNA to evaluate the status of acrosome in live cells.

RESULTS

Significant differences (P < 0.05) between the oviduct cell and the control groups after 24 hr were evident in the curvilinear velocity (VCL) (81.4 +/- 13.4 vs 60.0 +/- 14.1 microns/sec) and amplitude of lateral head displacement (ALH) (5.2 +/- 0.6 vs 4.1 +/- 0.5 microns). The incidence of acrosome reaction of live sperm was significantly higher in the endometrial cell group than in the controls (25.4 +/- 9.9 vs 6.6 +/- 2.4%; P < 0.001).

CONCLUSIONS

Coculture with human reproductive tract cells seems to improve some functional parameters of human spermatozoa. Coincubation with such cell lines, especially oviduct cells, might be a feasible approach to optimization of human spermatozoa for assisted fertilization using subfertile or frozen-thawed samples. We think coincubating human spermatozoa with a human reproductive tract cell line, especially oviduct cells, might be a feasible approach in preparing human spermatozoa for assisted fertilizatioin in subfertile and frozen-thawed semen samples.

Optimizing tubal epithelial cell growth promotes mouse embryo hatching in coculture

PURPOSE

This study investigates the relationship between human tubal epithelial cell growth characteristics and mouse embryonic development to determine which cellular requirements should be preferentially provided in a coculture system.

METHODS

Cell growth and viability were assessed for 5 days in alpha-minimal essential medium or human tubal fluid supplemented with 10% human serum or 10% synthetic serum. Two-cell mouse embryo development to blastocyst and hatching blastocyst stages was also assessed with or without coculture.

RESULTS

Both epithelial cell growth and embryo development were dependent on serum supplementation with better cell viability and growth rates in human serum and better blastocyst development in synthetic serum. The highest proportion of hatching blastocysts was found in alpha-minimal essential medium and human serum with coculture.

CONCLUSIONS

Culture conditions which improve tubal epithelial cell growth also improve the hatching rate of mouse embryos in coculture. This indicates that by meeting the metabolic and nutritional demands for epithelial cell growth, the beneficial effects of coculture on embryo development may be optimized.

Beneficial effects of coculture with cumulus cells on blastocyst formation in a prospective trial with supernumerary human embryos

PURPOSE

We reported previously on the use of coculture with cumulus cells in insemination medium for the development of human embryos in vitro. Here we describe a prospective trial to determine if this procedure has a significant beneficial effect.

METHODS

On the day after insemination, zygotes were randomized for culture in either a fresh drop of medium without (- cum) or were left in their insemination drop with (+ cum) cumulus cells. Embryos with the best morphological quality were replaced on the third day of development at the eight-cell stage. The remaining embryos were cultured for a further 3 days and cryopreserved if they reached the fully expanded blastocyst (FEB) stage. Three different culture media were used over the period of this study.

RESULTS

In 11 patients, supernumerary embryos were available only for continued culture in +cum and three patients had embryos cultured in only -cum. Thirty-nine other patients had embryos assigned to both +cum and -cum treatments. In the +cum group, 98 blastocysts developed from 216 embryos cultured for 6 days (45%), and this was significantly greater (P < 0.01) than the 48 blastocysts from 156 embryos (31%) developing in the absence of cumulus cells. In basal HTF medium (HTF medium with EDTA and glutamine) and basal XI HTF medium (similar to basal HTF but devoid of glucose and phosphate), culture of embryos with cumulus cells produced significantly more FEBs than in the absence of cumulus cells. There was no significant difference between the two culture treatments when regular HTF medium was used. Preliminary results indicate that pronectin-coated dishes provide a good substratum for cumulus cell attachment and embryo development.

CONCLUSIONS

The culture of human embryos with their cumulus cells in insemination drops of medium produces a significantly greater proportion of FEBs than when the zygotes are transferred to fresh culture drops devoid of cumulus cells. This is the first report of a significantly higher blastocyst rate with coculture in which a real comparison has been made between two culture treatments which differ only in the presence or absence of homologous cumulus cells in insemination drops.