The search for improved in-vitro systems should not be ignored: embryo co-culture may be one of them

Systematic Development, Validation and Optimization of a Human Embryo Culture System

Objective: To develop and validate a reliable in vitro culture system for human embryos. Design: Retrospective analyses of a series of four studies were conducted between 2006 and 2010 to assess the effect of incubator type (CO2 box versus Tri-gas minibox), media type, oil type, and hyaluronate supplementation. Optimization of in vitro blastocyst development was verified by assessing our National CDC/ART Surveillance reports between 2010 and 2016. Material and Methods: All patients experienced controlled ovarian hyperstimulation, followed by egg retrieval 35 h post-hCG. Cumulus-oocyte complexes were temporarily cultured in P1 or LG Fert medium plus HSA. Eggs were moved to a more complex media (G-medium or Global®-LG medium) containing a synthetic protein and embryo adhesion supplement (SPS and EAS, respectively; mLG) post-ICSI insemination. Zygotes were assigned to group culture in 25 µl droplets under oil (light mineral oil or paraffin oil; 37 °C) and embryo development was evaluated on Days 3, 5, and 6 and transferred on Day 3 to 5 depending on the number/quality of embryos available and the IVF history of the patient. Transfers were performed under ultrasound guidance, primarily using a Sureview-Wallace catheter, and enriched ET medium containing 500 µg/mL EAS. Results: Pilot study results (Expt. 1) showed that a mLG single-step medium could be effectively used in combination with Sanyo MCO-5 tri-gas (TG) incubators. Once adapted to SCIRS Lab in 2007 (Expt. 2), the latter culture system yielded improved blastocyst production and pregnancy outcomes compared to CO2 in air sequential incubation in P1/Multi-blast medium. In Expt. 3, the mLG/TG system yielded high levels of ≥2BB quality blastocysts (51 to 66%) across all age groups, and greater (p < 0.05) pregnancy success/live birth rates using fewer embryos transferred on Day 5 versus Day 3. After validating its clinical effectiveness, mLG was then prospectively compared to a new generation G-media (1.5 & 2.5; Expt. 4) and determined that the crossover treatment using paraffin oil (Ovoil™) allowed the mLG system to be optimized. Subsequently, a compilation of our Annual CDC/ART reported data over six years verified the overall viability of in vitro cultured and vitrified blastocysts produced in the mLG/TG system. Conclusion: By systematically evaluating and implementing various components of an embryo culture system we were able to optimize blastocyst development over the last decade. Our mLG/TG culture system modified an exceptionally well designed KSOMAA LG medium using endotoxin-free EAS and SPS additives to support cellular membrane wellness under stressful in vitro conditions (e.g., culture, cell biopsy, vitrification). Our use of the mLG/TG culture system has proven to be effective, creating reliably high blastocyst production, implantation, and healthy live births.

Interaction of the EGFR signaling pathway with porcine cumulus oocyte complexes and oviduct cells in a coculture system

It has become increasingly recognized that coculture has a beneficial effect on the in vitro maturation (IVM) of oocytes and embryo development in many species. However, these effects of coculture on IVM have been documented only for their positive conditioning roles without any evidence on the precise mechanisms underlying the action of coculture systems on the development of cumulus oocyte complexes (COCs). It has been suggested that the epidermal growth factor receptor (EGFR) signaling pathway is important for development of COCs, mediated by several epidermal growth factor (EGF)-like proteins with downstream mitogen-activated protein kinase 1/3 signaling. Therefore, we hypothesized that canine oviduct cells (OCs) in a coculture system, which shows improvement of oocyte quality in several species, are associated with EGFR signaling by exposure to progesterone (P4; imitating its production before ovulation and its continuous increase while oocytes reside in the oviduct to complete maturation in dogs). We designed three experimental groups: control, OCs coculture exposed to P4, and OCs coculture without exposure to P4. The result showed that the OCs coculture exposed to P4 strongly expressed EGF-like proteins and significantly improved COCs and subsequent embryo development. Furthermore, the expression of EGFR-related genes in cumulus cells and GDF9 and BMP15 in oocytes was upregulated in the P4-treated group. This study provides the first evidence that OCs exposed to P4 can induce strong expression of EGF-like proteins, and OCs effectively mediate improved porcine COCs development and subsequent embryo development by altering EGFR signaling related mRNA expression.

Embryo Culture Media, Culture Techniques and Embryo Selection: A Tribute to Wesley Kingston Whitten

This review article gives a brief history of the classical experiments that led to the development of the embryo culture medium and in vitro embryo culture. It proposes that, in view of the outstanding and significant pioneering contributions of Wesley Kingston Whitten to the development of embryo culture medium, he be considered the “Father of Embryo Culture Medium”. Furthermore, it describes the nutritional requirements of early embryos and how these requirements with specific references to carbohydrates, amino acids, phosphates, growth factors, etc, have been utilized to formulate increasingly more complex embryo culture media. This has led to the development of progressively more efficacious embryo culture media including the formulation of completely defined and synthetic protein-free embryo culture medium. The review also describes physical factors, growth factors, insemination methods for the fertilization of oocytes and culture methods affecting embryo growth, development, metabolism, oxygen embryotoxicity and survival. In procedural terms, the review also summarizes the evolution of embryo culture techniques from tube culture to, microdrop culture under oil to co-culture to ultra microdrop culture techniques. It includes techniques of in vitro maturation and for the selection of potentially viable embryos of various developmental stages.

On-chip single embryo coculture with microporous-membrane-supported endometrial cells

In vitro culture (IVC) of the mammalian embryo is an essential technique in reproductive technology and other related life science disciplines. Although embryos are usually cultured in groups, a single embryo culture has been highly desired for IVC to investigate developmental processes. In this study, we proposed and developed the first single embryo coculture device, which allows making an array of a single embryo coculture with endometrial cells by controlling the culture environment in a microfluidic device. To realize this concept, we investigated three key issues: selection of a culture medium for the embryo coculture with endometrial cells using a mouse embryo and endometrial cells, evaluation of an on-microporous-membrane coculture of endometrial cells and an embryo to control the polarization of endometrial cells on the membrane, and evaluation of the coculture of endometrial cells and the embryo in the microfluidic device. We successfully obtained an array of a single coculture of embryo with endometrial cells in a microfluidic device. This concept will open and enhance the management of an individual embryo for assisted reproductive technology, livestock breeding, and fundamental stage research by further development.

Effects of co-culture and embryo number on the in vitro development of bovine embryos

It is generally accepted that culturing embryos in groups or with somatic cells improves both the yield and quality of the blastocysts obtained. The aims of this study were 1) to compare the yield and quality of the embryos obtained after culture in several number conditions and in several culture systems and 2) to assess the effect of co-culture started at various stages of embryo development. Under cell-free culture conditions (modified synthetic oviduct fluid [mSOF] supplemented with 10% fetal calf serum [FCS] 48 h post insemination, the rate of Day 10 blastocysts was lower when embryos were cultured in small groups (1 to 6 per drop) than in large groups (4 versus 23% ; P < 0.01). There was no group effect when embryos were co-cultured either with Buffalo rat liver (BRL) cells in TCM 199, or in a culture system allowing the progressive development of cumulus cells in mSOF, even if co-culture started at 66 or 114 h post insemination. However, embryos cultured singly had lower cell numbers than embryos cultured in large groups when co-culture started at 114 h post insemination. This suggests that 1) somatic cells improve the development of singly cultured bovine embryos up to the blastocyst stage after the 9-16 cell stage; 2) co-culture affects blastocyst cell number of singly cultured embryos by acting roughly between the 5-8 and the 9-16 cell stage; and 3) cooperation between embryos could replace the effect of co-culture either on the yield of blastocysts or on blastocyst cell number. Blastocysts appeared significantly earlier in co-culture with cumulus cells in mSOF than in co-culture with BRL cells in TCM 199 (detection of the blastocysts: 7.3 +/- 0.1 d post insemination with cumulus cells versus 8.1 +/- 0.1 d with BRL cells; P < 0.001) and had a significant higher number of cells (143 +/- 9 versus 85 +/- 11; P < 0.001). This system thus seems suitable for the culture of small numbers of embryos resulting from in vitro maturation and fertilization of oocytes from individual donor cows.

Development of mouse embryos co-cultured with polarized or non-polarized uterine epithelial cells using sequential culture media

This study investigated the effects of the in vitro co-culture of mouse embryos with non-polarized or polarized uterine epithelial cells, using sequential culture media, on their development to blastocysts, blastocyst quality (blastocyst diameter and cell number), apoptosis, Bcl-2 and Bax gene expression. There were three treatments, all of which used sequential culture media. The treatments were no co-culture (control), non-polarized or polarized epithelial cell monolayer co-culture in 24-well tissue culture plates. Mouse uterine epithelial cells were isolated enzymatically and were seeded either on the surface of the culture plate (non-polarized monolayer) or on a Millipore filter insert coated with extra-cellular matrix extract (polarized monolayer) that was then placed in the culture plate. Two-cell mouse embryos were cultured in G-1 ver3 medium to the eight-cell stage when they were randomly assigned to the treatments. The culture medium was G-2 ver3 during the treatment phase of the study. Significances of differences were evaluated by the one-way analysis of variance for continuous data. The epithelial cells cultured on Millipore filters became polarized and their morphology compared favorably with those cultured on the surface of the culture plate and in vivo uterine epithelial cells. After 96 h on the treatments, the polarized monolayer had supported the development of significantly more hatched blastocysts (80.0%; P<0.05) than the non-polarized monolayer (63.4%) or the control (61.4%) culture treatments. Co-culture resulted in the production of blastocysts with significantly more cells (non-polarized monolayer 56.7+/-2.1, polarized monolayer 61.9+/-2.1) than the control culture (42.8+/-2.6; P<0.05) but the diameter and shape of the blastocysts were not significantly different. The proportion of blastocysts with apoptotic blastomere was higher for the control culture (94.4%) than for the non-polarized (68.2%) or polarized (66.7%) co-culture systems (P<0.05). Moreover, the apoptotic index was significantly higher in control blastocysts (5.6+/-0.9; P<0.05) than in non-polarized (1.7+/-0.3) or polarized (1.5+/-0.3) co-culture. In the control, Bax mRNA was strongly expressed when compared to co-culture treatments (P<0.05), whereas, the relative abundance of Bcl-2 mRNA to the beta-tubulin was lower than co-culture treatments (P<0.05). It is concluded that a co-culture system involving polarized uterine epithelial cells and sequential culture media is a promising method of producing mouse embryos.

The effect of Vero cell coculture on the development of mouse embryos exposed to monoclonal antibodies specific for mammalian heat shock protein 60

Heat shock proteins (HSP) have been identified as an important factor of a very complex and highly conserved cellular defense mechanism to preserve cell survival under adverse environmental conditions. HSP 60 are immunodominant antigens of microbe such as Chlamydia trachomatis and have a potentiality to become a target antigen due to antigenic similarity between chlamydial and human HSP. This study was conducted to investigate the effects of Vero cell coculture to anti-HSP 60 on the early mouse embryo development in vitro. The 2-cell mouse embryos (ICR) were cultured and mouse embryo development was observed every 24 hr for 3 days. 45% and 22.1% of the embryos cultured in Ham's F-10 plus anti HSP 60 with Vero cells developed to the 4- to 8- cell stage (day 1) and morular stage (day 2) as compared with 29.2% and 2.7% of those cultured without Vero cells respectively. But at day 3, the beneficial effect of Vero cells was not noted. These findings suggest that Vero cells have some roles to overcome the detrimental effect of anti-HSP 60 to some degree. These results suggest that Vero cells coculture will promote reproductive outcome in patient previously sensitized to microbial (e.g. Chlamydia trachomatis) HSP 60.

Successful freezing and thawing of blastocysts cultured in sequential media using a modified method

OBJECTIVE

To evaluate the clinical role of blastocyst freezing and thawing after prolonged culturing in sequential media.

DESIGN

Retrospective analysis of 293 blastocyst freeze-thawing cycles.

SETTING

University hospital infertility unit.

PATIENT(S)

Nonselected couples undergoing IVF.

INTERVENTION(S)

Blastocysts were frozen and thawed by a modified method.

MAIN OUTCOME MEASURES

Blastocyst recovery after freeze-thawing and pregnancy rates after the transfer. Evaluation of the effect of the number of transferred blastocysts, the method of IVF, and of the woman's age on the results achieved by frozen-thawed blastocysts.

RESULT(S)

Frozen-thawed blastocysts provided a 29.5% clinical pregnancy rate per transfer. After the transfer of three blastocysts the pregnancy rate was 42.0%, and after the transfer of one or two blastocysts it was approximately the same (25.0% and 28.0%, respectively). The method of IVF did not affect pregnancy rates, but the increasing age of the woman did. Pregnancies were characterized by a low abortion rate (8.0%) regardless of the age of the woman.

CONCLUSION(S)

A modified method for blastocyst freeze-thawing provides good clinical results. It offers the possibility for a single-thawed blastocyst transfer and represents a good alternative for older women because of its lower risk of spontaneous abortion.

The mechanism of action of coculture on embryo development in the mouse model: direct embryo-to-cell contact and the removal of deleterious components

OBJECTIVE

To elucidate the mechanism for the mode of action of coculture by the use of a coculture system for mouse one-cell embryos with human oviductal epithelial cells.

DESIGN

Prospective, controlled in vitro experimental study.

SETTING

Academic research laboratory.

ANIMAL(S)

Female ICR strain mice aged between 6 and 8 weeks.

INTERVENTION(S)

Flushed one-cell embryos were cultured in human tubal fluid medium alone (control), in coculture system with human oviductal cells, in five kinds of conditioned media, and in a contactless coculture system using a cell-culture insert.

MAIN OUTCOME MEASURE(S)

The percentage of the embryos developed to hatching blastocyst stage and the level of superoxide anion in the supernatant from each culture condition.

RESULT(S)

The rates of embryo development to the hatching blastocyst stage were significantly higher in the coculture group (43%) than in the control group (none) (P <.05). The embryo development rate in the control group was similar to that of the embryos in the five kinds of conditioned media. The effects of coculture on embryo development disappeared in the contactless coculture group. The level of superoxide anion was significantly reduced in the coculture group compared to the control group.

CONCLUSION(S)

The present coculture system overcomes the two-cell block in vitro and improves the embryo development. The beneficial effect may be a result of direct cell-to-cell contact between the embryo and helper cells and the removal of deleterious components from medium, rather than a result of embryotrophic factors.

Human embryo development and pregnancies in an homologous granulosa cell coculture system

PURPOSE

Our purpose was to determine the effects of the coculture of embryos on human granulosa cells (GCs) in patients in the first cycle of IVF-ET treatment and in patients with repeated implantation failures and to investigate the presence of specific proteins in a 48-hr GC conditioned medium and the GC ultrastructural characteristics.

METHODS

Eighteen patients with tubal or idiopathic infertility were enrolled in this study: 7 patients (Trial 1) were in the first cycle of IVF-ET treatment and 11 patients (Trial 2) had repeated implantation failures (one to five). Embryos from each patient were cocultured randomly either on homologous granulosa cells or on a conventional culture medium.

RESULTS

At the end of the coculture period (day 5 or 6), 50% of the embryos (Trial 1) reached the blastocyst stage, with respect to 35% in Trial 2. The pregnancy rate per retrieval was 14.2 and 9%, respectively, in Trial 1 and in Trial 2. Many conditioned media showed proteins of 24-29 kDa. and some of them showed additional proteins of 90 kDa. The ultrastructural analysis of GCs showed healthy, metabolically active, protein-synthesizing, and mostly steroidogenic cells.

CONCLUSIONS

GC cultures improve embryo development but not pregnancy rates both in Trial 1 and in Trial 2.

Comparison of sex ratio and cell number of IVM-IVF bovine blastocysts co-cultured with bovine oviduct epithelial cells or with Vero cells

The influence of 2 co-culture systems (BOEC and Vero cells) on the development rates, quality grades and sex ratios of IVM-IVF bovine embryos were studied. Zygotes obtained after IVF were co-cultured in each co-culture system for 7 and 8 d (Day 0 = day of insemination) in B2 medium. No effect of the co-culture system was observed on development rates measured on Days 7 and 8. However, Vero cell co-culture had a positive influence on embryo quality. Irrespective of their sex, embryos produced on Vero cells showed higher cells number than those co-cultured on BOEC (103.4 +/- 3.8 and 97 +/- 8.12 for BOEC vs 113.7 +/- 3.5 and 114 +/- 5.9 for Vero cells at Days 7 and 8, respectively; P < 0.05). The percentage of male embryos was increased in the two co-culture systems (60.7% males for BOEC; P < 0.05 vs 63% males for Vero cells; P < 0.01) on Day 7. In both co-culture systems the increase in the percentage of males was more obvious for embryos reaching the most advanced stage (expanded blastocysts). The results show that Vero cells improved the quality grade of bovine embryos produced in vitro, and thus are recommended for use as a safe co-culture system that does not contain pathogens.

Coculture of human embryos with buffalo rat liver cells for women with decreased prognosis in in vitro fertilization

OBJECTIVE

The coculture of human embryos with epithelial cells may improve both embryo quality and pregnancy rates. In this current study we tested the efficacy of coculture with the buffalo rat liver cell line on pregnancy rates in women with a potentially poor prognosis for success with in vitro fertilization (previous in vitro fertilization failure, advanced maternal age, increased early follicular follicle-stimulating hormone levels, and anovulation).

STUDY DESIGN

This prospective controlled study evaluated a total of 203 women (135 coculture, 68 controls) undergoing in vitro fertilization. Implantation rates per embryo, clinical pregnancy rates, and continuing/delivered pregnancy rates were analyzed.

RESULTS

Buffalo rat liver cells, which are commercially available, are stable in coculture. Implantation rates (number of sacs with fetal heart motion per embryos transferred) were similar for coculture (19%) and control (18%) embryos. No difference in the rate of continuing/delivered pregnancies per retrieval was noted (17% coculture vs 14% control) in the group with advanced maternal age, but coculture caused a trend toward improved pregnancy rates in the group with ovulatory dysfunction (43% coculture vs 14% control) and the group with previous in vitro fertilization failure (34% coculture vs 28% control).

CONCLUSION

This is the first published controlled study to our knowledge that reports the use of the buffalo rat liver cell coculture for human in vitro fertilization in a large number of patients. Our data support consideration of buffalo rat liver coculture for in vitro fertilization for women with previous in vitro fertilization failure and possibly for patients with oocyte or ovulatory dysfunction.

Effect of high molecular weight factors present in bovine oviductconditioned medium on in vitro bovine embryo development

To investigate the presence of embryotrophic factors in bovine oviduct-conditioned medium (BOCM), the high molecular weight fraction (> 10 KDa) from BOCM was added to 3 chemically defined embryo culture media (TCM199, DMEM/F12 and modified synthetic oviduct fluid [mSOF]). Zygotes were obtained by in vitro maturation and fertilization of oocytes. Conditioning of TCM199 with oviduct cells increased both cleavage to the 5- to 8-cell stage (59 vs 37%) and further development to the blastocyst stage (19 vs 4%). The low molecular weight fraction (< 10 KDa) of BOCM maintained development to the 5- to 8-cell stage but did not allow development to the blastocyst stage. Adding the high molecular weight fraction to the inactive low molecular weight fraction restored bovine embryo development up to the blastocyst stage. This embryotrophic effect of the high molecular weight fraction was not observed when this fraction was added to TCM199 or DMEM/F12 medium. Whereas adding this fraction to mSOF medium significantly (P<0.05) increased embryo development up to the blastocyst stage (36%) in comparison with that of mSOF (15%) or BOCM (14%). These results show that BOCM contains high molecular weight factors promoting embryo development up to the blastocyst stage. Some chemically defined media mask the effect of these embryotrophic factors.

Differential preimplantation development of rhesus monkey embryos in serum-supplemented media

Several media, some augmented with amino acids, have been formulated recently, based on simplex optimization, to support the preimplantation development of mouse embryos. For the highly limited studies on preimplantation development of nonhuman primate embryos, a complex medium (CMRL-1066) has been employed. Our objective was to compare the developmental ability of rhesus monkey embryos in a simple medium containing amino acids, KSOM/AA, with the complex media used previously. Zygotes (99) were recovered following in vitro fertilization (IVF) from six monkeys, allocated to either CMRL or KSOM/AA both containing 10% fetal calf serum (FCS), and monitored daily until reaching the expanded or hatched blastocyst stage. The distribution of cells between the inner cell mass (ICM) and trophectoderm was determined at the end of culture by differential nuclear staining. Although a greater number of embryos cultured in KSOM/AA vs. CMRL developed to the morula stage (80%) and beyond (66% to expanded blastocyst), the differences were not significant. Such embryos in KSOM/AA did, however, develop at a significantly faster rate, on average, reaching the expanded blastocyst stage 26 hr earlier than did embryos cultured in CMRL. KSOM/AA embryos hatched in less time and had a higher percentage (43 vs. 34) of cells allocated to the ICM. These results indicate that a simple medium, KSOM/AA, in the presence of serum, supports the development of rhesus monkey embryos at high efficiency and at a faster rate than that observed for embryos cultured in the complex medium, CMRL-1066.

The effects of coculture with autologous cryopreserved endometrial cells on human in vitro fertilization and early embryo morphology: a randomized study

PURPOSE

The aim of this study was to examine the influence of endometrial cells on the fertilization rate and early embryonic morphology following routine in vitro fertilization (IVF). Cryopreservation with subsequent thawing allowed the use of autologous somatic cells, thus minimizing the risk of transmission of infective agents. Interpatient variability was eliminated by randomizing oocytes from each cycle into the control or coculture group.

RESULTS

Two hundred ninety-four oocytes from 24 IVF cycles (21 patients) were included in the study (145 coculture and 149 control). The normal fertilization rate of control oocytes (56.4%) was not significantly different from that of oocytes cocultured with endometrial cells (61.4%). The mean number of blastomeres in cocultured embryos (3.65) was not significantly different from the number in control embryos (3.46) 2 days after insemination, but the proportion of embryos with minimal or no fragmentation was significantly higher in the coculture group [34/84 (40.5%) vs. 17/80 (21.3%); P < 0.01].

CONCLUSIONS

The inclusion of cryopreserved autologous endometrial cells in routine clinical IVF procedures does not influence fertilization or the early cleavage rate but may reduce the extent of embryo fragmentation during the early cleavage divisions.

Effect of coculture on subsequent survival and implantation of cryopreserved human embryos

PURPOSE

This retrospective analysis was designed to assess the performance of human embryos following cryopreservation based on whether they were originally developed in standard culture medium (65 cycles, 223 embryos) or cocultured on partial monolayers of bovine oviductal epithelial cells (63 cycles, 198 embryos). Embryo cryosurvival and implantation were compared between the study group and the contemporaneously match controls.

RESULTS

During a 2-year period when no factors of the cryopreservation program were altered, 63 transfers of 159 surviving thawed control cleavage-stage embryos (71.3% survival) that were 54% intact gave rise to 11 viable pregnancies (17.5%/ET), to yield an implantation rate of 6.9% per embryo. Sixty-three transfers of 147 thawed cocultured embryos (74.2% survival) that were 61% intact gave an implantation rate of 13.6% per embryo that was significantly higher than the control group (P < 0.05).

CONCLUSION

Coculture of embryos prior to cryopreservation does not appear to improve cryosurvival; however, it does improve implantation postthaw compared with embryos following standard culture prior to cryopreservation.

Co-culture of the early human embryo: factors affecting human blastocyst formation in vitro

Co-culture systems have been designed to overcome the embryonic developmental arrest observed in vitro in conventional culture media. Oviduct and uterine epithelial cells can sustain embryonic development, as can trophoblastic tissue and transport epithelia of non-genital origin. Its benefits involve neither hormone dependency nor histo-specificity. Fibroblasts do not overcome the developmental arrest in most mammalian species, but whether they do in humans is still unsure. In all systems, the quality of the feeder cells and the co-culture medium are very important. Using the Vero cell line, 60% of human IVF embryos reach the blastocyst stage. The quality of the sperm seems to affect results. We have observed: For 10% of the patients with unexplained fertility, blastocyst stage is not attained; this probably involves a maternal (ovarian) problem. When at least one blastocyst is transferred, the pregnancy rate per transfer is 31%. The implantation rate in pregnant women is higher than after transfer at day 2. After repeated failures of transfer at early stages (2-6 cells), transfer at the blastocyst stage gives high pregnancy rates (40%). This indicates an in vitro selection. There is a strong paternal effect on blastocyst formation: poor quality sperm give lower rates of blastocyst. Co-culture helps to understand treatment failures related to male factors. Around 60% of the patients having spare embryos have had blastocysts frozen. Transfers of frozen-thawed blastocysts give a 20% pregnancy rate and an implantation rate per embryo of 11%. Co-culture is a new tool which has to be carefully evaluated in human IVF programs. It does not impair "a minima" embryo viability and it allows in vitro selection.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth factors in reproduction

The changes that occur in the female reproductive tract during the menstrual cycle and in early pregnancy, in preparation for embryo implantation and subsequent placental and fetal development, have long attracted the interest of reproductive biologists. The early embryo expresses growth factors and growth factor receptors that are, in general, temporally expressed. In addition, the oviduct and uterine endometrium also synthesize growth factors and cytokines, and the developing embryo finds itself in a growth-factor-rich milieu during early development. The autocrine, juxtracrine, and paracrine actions of these factors in the development of the early embryo and of the maternal reproductive tract are just beginning to be appreciated, as are their potential roles in cellular proliferation and cell-cell communication within the developing embryo, in the reproductive tract, and at the maternal-trophoblast interface. When detailed mechanisms underlying these interactions are fully understood, it is anticipated that therapies will be rationally designed to treat reproductive disorders associated with abnormal embryonic development and poor placentation.

In vitro development of bovine embryos in Buffalo rat liver- or bovine oviduct-conditioned medium

A culture system for bovine embryos was developed using Buffalo rat liver cell (BRL) line-conditioned medium without serum. Zygotes, obtained by in vitro maturation and fertilization of oocytes, were cultured either in unconditioned medium (TCM 199 or DMEM/F12) or in the same medium conditioned by bovine oviduct or BRL cells. No serum was added during conditioning or during embryo culture. The DMEM/F12 medium was superior to TCM 199 for development of bovine embryos to the 5 to 8-cell stage: on average between 50 and 57% of the embryos reached this stage after 2 d of culture in DMEM/F12 or in conditioned medium, while 36% reached this stage in TCM 199. Further development to the blastocyst stage was enhanced by conditioning. The highest percentage of blastocysts was achieved in DMEM/F12 medium conditioned with BRL cells (30%). The yield of blastocysts was similar in TCM 199 and in DMEM/F12 media conditioned with bovine oviduct cells (22 versus 20%), but after conditioning with BRL cells, DMEM/F12 medium yielded a higher percentage of blastocysts than TCM 199 (30 versus 18%). This might be explained by the fact that viability of BRL cells was better in DMEM/F12 medium than in TCM 199 when serum was omitted. Blastocysts produced in BRL-conditioned medium had a higher number of cells than blastocysts obtained in bovine oviduct-conditioned medium, and their transfer to recipients led to pregnancies and birth of calves. In conclusion, culture of bovine embryos in DMEM/F12 medium conditioned with BRL cells without serum led to the development of good-quality blastocysts and is thus a promising method for producing embryos for the study of potential embryotrophic factors. The use of rat liver cell lines guarantees against bovine viruses and allows for better production of embryos.

Use of coculture with cumulus cells in insemination medium in human in vitro fertilization (IVF)

PURPOSE

In an initial trial, 16 of 33 (48%) bipronuclear human zygotes left in culture in the insemination drop from which they had originated developed to fully expanded blastocysts.

RESULTS

This method was subsequently used for all supernumerary embryos judged unsuitable for replacement or cryopreservation on Day 1, 2, or 3 of development. Over a 4-year period, embryos reaching the fully expanded blastocyst stage were cryopreserved. Of 113 such blastocysts thawed, 81 survived (72%), and upon transfer to 52 patients, 8 clinical pregnancies were established (15%), of which 6 were live births. Subsequently, following modification of some culture parameters, 60 patients had 296 supernumerary embryos cultured for 6 days; 43 of these patients (72%) had 148 embryos (50%) that cavitated and 134 (45%) of these cavitating embryos were judged to be fully expanded blastocycts; 125 (42%) of these embryos were cryopreserved.

CONCLUSION

The blastocyst formation rate is similar to that reported by others using conventional culture procedures or coculture on Vero or other cell types. I conclude that cumulus cells are a ready source of feeder cells for the coculture of human embryos.