Effect of human granulosa cell co-culture using standard culture media on the maturation and fertilization potential of immature human oocytes

Human-induced pluripotent stem cell-derived ovarian support cell co-culture improves oocyte maturation in vitro after abbreviated gonadotropin stimulation

STUDY QUESTION

Can in vitro maturation (IVM) and developmental competence of human oocytes be improved by co-culture with ovarian support cells (OSCs) derived from human-induced pluripotent stem cells (hiPSCs)?

SUMMARY ANSWER

OSC-IVM significantly improves the rates of metaphase II (MII) formation and euploid Day 5 or 6 blastocyst formation, when compared to a commercially available IVM system.

WHAT IS KNOWN ALREADY

IVM has historically shown highly variable performance in maturing oocytes and generating oocytes with strong developmental capacity, while limited studies have shown a positive benefit of primary granulosa cell co-culture for IVM. We recently reported the development of OSCs generated from hiPSCs that recapitulate dynamic ovarian function in vitro.

STUDY DESIGN, SIZE, DURATION

The study was designed as a basic science study, using randomized sibling oocyte specimen allocation. Using pilot study data, a prospective sample size of 20 donors or at least 65 oocytes per condition were used for subsequent experiments. A total of 67 oocyte donors were recruited to undergo abbreviated gonadotropin stimulation with or without hCG triggers and retrieved cumulus-oocyte complexes (COCs) were allocated between the OSC-IVM or control conditions (fetal-like OSC (FOSC)-IVM or media-only IVM) in three independent experimental design formats. The total study duration was 1 April 2022 to 1 July 2023.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Oocyte donors between the ages of 19 and 37 years were recruited for retrieval after informed consent, with assessment of anti-Mullerian hormone, antral follicle count, age, BMI and ovarian pathology used for inclusion and exclusion criteria. In experiment 1, 27 oocyte donors were recruited, in experiment 2, 23 oocyte donors were recruited, and in experiment 3, 17 oocyte donors and 3 sperm donors were recruited. The OSC-IVM culture condition was composed of 100 000 OSCs in suspension culture with hCG, recombinant FSH, androstenedione, and doxycycline supplementation. IVM controls lacked OSCs and contained either the same supplementation, FSH and hCG only (a commercial IVM control), or FOSCs with the same supplementation (Media control). Experiment 1 compared OSC-IVM, FOSC-IVM, and a Media control, while experiments 2 and 3 compared OSC-IVM and a commercial IVM control. Primary endpoints in the first two experiments were the MII formation (i.e. maturation) rate and morphological quality assessment. In the third experiment, the fertilization and embryo formation rates were assessed with genetic testing for aneuploidy and epigenetic quality in blastocysts.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed a statistically significant improvement (∼1.5×) in maturation outcomes for oocytes that underwent IVM with OSCs compared to control Media-IVM and FOSC-IVM in experiment 1. More specifically, the OSC-IVM group yielded a MII formation rate of 68% ± 6.83% SEM versus 46% ± 8.51% SEM in the Media control (P = 0.02592, unpaired t-test). FOSC-IVM yielded a 51% ± 9.23% SEM MII formation rate which did not significantly differ from the media control (P = 0.77 unpaired t-test). Additionally, OSC-IVM yielded a statistically significant ∼1.6× higher average MII formation rate at 68% ± 6.74% when compared to 43% ± 7.90% in the commercially available IVM control condition (P = 0.0349, paired t-test) in experiment 2. Oocyte morphological quality between OSC-IVM and the controls did not significantly differ. In experiment 3, OSC-IVM oocytes demonstrated a statistically significant improvement in Day 5 or 6 euploid blastocyst formation per COC compared to the commercial IVM control (25% ± 7.47% vs 11% ± 3.82%, P = 0.0349 logistic regression). Also in experiment 3, the OSC-treated oocytes generated blastocysts with similar global and germline differentially methylated region epigenetic profiles compared commercial IVM controls or blastocysts after either conventional ovarian stimulation.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

While the findings of this study are compelling, the cohort size remains limited and was powered on preliminary pilot studies, and the basic research nature of the study limits generalizability compared to randomized control trials. Additionally, use of hCG-triggered cycles results in a heterogenous oocyte cohort, and potential differences in the underlying maturation state of oocytes pre-IVM may limit or bias findings. Further research is needed to clarify and characterize the precise mechanism of action of the OSC-IVM system. Further research is also needed to establish whether these embryos are capable of implantation and further development, a key indication of their clinical utility.

WIDER IMPLICATIONS OF THE FINDINGS

Together, these findings demonstrate a novel approach to IVM with broad applicability to modern ART practice. The controls used in this study are in line with and have produced similar to findings to those in the literature, and the outcome of this study supports findings from previous co-culture studies that found benefits of primary granulosa cells on IVM outcomes. The OSC-IVM system shows promise as a highly flexible IVM approach that can complement a broad range of stimulation styles and patient populations. Particularly for patients who cannot or prefer not to undergo conventional gonadotropin stimulation, OSC-IVM may present a viable path for obtaining developmentally competent, mature oocytes.

STUDY FUNDING/COMPETING INTEREST(S)

A.D.N., A.B.F., A.G., B.P., C.A., C.C.K., F.B., G.R., K.S.P., K.W., M.M., P.C., S.P., and M.-J.F.-G. are shareholders in the for-profit biotechnology company Gameto Inc. P.R.J.F. declares paid consultancy for Gameto Inc. P.C. also declares paid consultancy for the Scientific Advisory Board for Gameto Inc. D.H.M. has received consulting services from Granata Bio, Sanford Fertility and Reproductive Medicine, Gameto, and Buffalo IVF, and travel support from the Upper Egypt Assisted Reproduction Society. C.C.K., S.P., M.M., A.G., B.P., K.S.P., G.R., and A.D.N. are listed on a patent covering the use of OSCs for IVM: U.S. Provisional Patent Application No. 63/492,210. Additionally, C.C.K. and K.W. are listed on three patents covering the use of OSCs for IVM: U.S. Patent Application No. 17/846,725, U.S Patent Application No. 17/846,845, and International Patent Application No.: PCT/US2023/026012. C.C.K., M.P.S., and P.C. additionally are listed on three patents for the transcription factor-directed production of granulosa-like cells from stem cells: International Patent Application No.: PCT/US2023/065140, U.S. Provisional Application No. 63/326,640, and U.S. Provisional Application No. 63/444,108. The remaining authors have no conflicts of interest to declare.

Telomere Length and Telomerase Activity of Granulosa Cells and Follicular Fluid in Women Undergoing In Vitro Fertilization

This study aimed to evaluate the interrelationship between telomere length, telomerase activity and oxidative DNA damage in patients undergoing in vitro fertilization (IVF). This single-center, observational clinical study comprised 102 unselected, consecutive patients with various infertility diagnoses. Granulosa cells (GCs) and follicular fluid (FF) were analyzed simultaneously for telomere functions and for the marker of oxidative DNA damage, 8-hydroxy-2-deoxyguanosine (8-OHdG). An Absolute Human Telomere Lengths Quantification qPCR Assay kit and Telomerase Activity Quantification qPCR Assay kit (Nucleotestbio, Budapest, Hungary), as well as an 8-OHdG ELISA kit (Abbexa Ltd., Cambridge, United Kingdom) were used for analyses. Similar telomere lengths were found in GCs and FF, however telomerase activity was markedly depressed, while 8-OHdG levels were markedly elevated in FF compared with those in GCs (p < 0.01). Telomere lengths were independent of telomerase activity both in GCs and FF. However, GC 8-OHdG was inversely related to telomerase activity in GCs and FF (p < 0.05). Importantly, 8-OHdG levels both in GCs and FF had significant negative impact on the number of the retrieved and MII oocytes (p < 0.01), whereas FF 8-OHdG was negatively related further to the number of fertilized oocytes and blastocysts (p < 0.01). In conclusion, we could not confirm the direct association of telomere function and reproductive potential. However, oxidative DNA damage, as mainly reflected by 8-OHdG, adversely affected early markers of IVF outcome and clinical pregnancies.

Analysis of maturation dynamics and developmental competence of in vitro matured oocytes under time-lapse monitoring

BACKGROUND

To improve the developmental competence of in vitro cultured oocytes, extensive literature focused on maturation rate improvement with different additives in culture medium, while studies investigating the maturation dynamics of oocytes during in vitro maturation (IVM) and the influencing factors on oocyte viability are scarce.

METHODS

The study involved a retrospective observation by time-lapse monitoring of the IVM process of 157 donated GV oocytes from 59 infertile couples receiving ICSI in 2019, in Tongji Hospital, Wuhan, China. The GV oocytes derived from controlled ovarian hyperstimulation (COH) cycles underwent rescue IVM (R-IVM), and the maturation dynamics, including GVBD time (GV-MI), time from GVBD to maturation (MI-MII), maturation time (GV-MII), and MII arrest duration (MII-ICSI), were recorded by time-lapse monitoring. The matured oocytes were inseminated at different MII arrest points and subsequent embryo developments were assessed. The effects of baseline clinical characteristics, oocyte diameters, and maturation dynamics on the developmental competence of the oocytes were also analyzed.

RESULTS

Totally, 157 GV oocytes were collected. GVBD happened in 111 oocytes, with a median GV-MI duration of 3.7 h. The median MI-MII duration was 15.6 h and the median GV-MII duration was 19.5 h. The maturation rate reached 56.7% at 24 h and 66.9% at 48 h, and the clinical factors, including patient age, FSH level, AMH level, ovarian stimulation protocol, and serum estradiol and progesterone levels on hCG trigger day, showed no effects on the 24-h maturation rate. The normal fertilization rate of oocytes resuming meiosis within 8 h and matured within 24 h was significantly higher than that of oocytes resuming meiosis after 8 h and matured after 24 h. Furthermore, among those oocytes matured within 24 h, the high-quality embryo formation rate of oocytes resuming meiosis within 4.5 h and matured within 19 h was significantly higher. All stated time was measured from the start point of IVM. Additionally, for oocytes from patients with serum progesterone levels less than 1 ng/ml on hCG trigger day, the high-quality embryo formation rate was significantly increased.

CONCLUSION

R-IVM technology could increase the available embryos for patients in routine COH cycles, but excessive culture beyond 24 h is not recommended. GV-MI duration of the oocyte, recorded by time-lapse system, and serum progesterone levels of patients on hCG trigger day can significantly affect the developmental potential of the IVM oocytes.

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

Objective

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

Materials and Methods

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

Results

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

Conclusion

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

Ovulatory signals alter granulosa cell behavior through YAP1 signaling

BACKGROUND

The Hippo pathway plays critical roles in regulating cell proliferation, differentiation and survival among species. Hippo pathway proteins are expressed in the ovary and are involved in ovarian function. Deletion of Lats1 causes germ cell loss, ovarian stromal tumors and reduced fertility. Ovarian fragmentation induces nuclear YAP1 accumulation and increased follicular development. At ovulation, follicular cells stop proliferating and terminally differentiate, but the mechanisms controlling this transition are not completely known. Here we explore the role of Hippo signaling in mouse granulosa cells before and during ovulation.

METHODS

To assess the effect of oocytes on Hippo transcripts in cumulus cells, cumulus granulosa cells were cultured with oocytes and cumulus oocyte complexes (COCs) were cultured with a pSMAD2/3 inhibitor. Secondly, to evaluate the criticality of YAP1 on granulosa cell proliferation, mural granulosa cells were cultured with oocytes, YAP1-TEAD inhibitor verteporfin or both, followed by cell viability assay. Next, COCs were cultured with verteporfin to reveal its role during cumulus expansion. Media progesterone levels were measured using ELISA assay and Hippo transcripts and expansion signatures from COCs were assessed. Lastly, the effects of ovulatory signals (EGF in vitro and hCG in vivo) on Hippo protein levels and phosphorylation were examined. Throughout, transcripts were quantified by qRT-PCR and proteins were quantified by immunoblotting. Data were analyzed by student's t-test or one-way ANOVA followed by Tukey's post-hoc test or Dunnett's post-hoc test.

RESULTS

Our data show that before ovulation oocytes inhibit expression of Hippo transcripts and promote granulosa cell survival likely through YAP1. Moreover, the YAP1 inhibitor verteporfin, triggers premature differentiation as indicated by upregulation of expansion transcripts and increased progesterone production from COCs in vitro. In vivo, ovulatory signals cause an increase in abundance of Hippo transcripts and stimulate Hippo pathway activity as indicated by increased phosphorylation of the Hippo targets YAP1 and WWTR1 in the ovary. In vitro, EGF causes a transient increase in YAP1 phosphorylation followed by decreased YAP1 protein with only modest effects on WWTR1 in COCs.

CONCLUSIONS

Our results support a YAP1-mediated mechanism that controls cell survival and differentiation of granulosa cells during ovulation.

Could fertility clinics offer a sizable improvement of live birth rates by maturing post-GVBD oocytes in vitro?

PURPOSE

The objective of this study is to analyze the potential of immature, denuded, post-GVBD (germinal vesicle breakdown) oocytes (including prometaphase I, metaphase I, and prometaphase II stages) to result live birth after in vitro maturation. Furthermore, we compared two culture media to identify which of them provides better reproductive outcomes when used for in vitro maturation.

METHODS

We performed a retrospective cohort study including 4022 IVF-ICSI (in vitro fertilization-intracytoplasmic sperm injection) cycles between 2011 and 2015. A total of 4450 immature post-GVBD oocytes from 1442 cycles were cultured in vitro; of these, 2364 oocytes reached MII (metaphase II) stage (IVMC oocytes, in vitro meiotic completion) and were fertilized. Overall, 3933 embryo transfers were performed: 3579 were embryos derived from MII oocytes (ET-MII); 264 were embryos derived from MII + IVMC oocytes (ET-MIX), and 90 embryos from IVMC oocytes (ET-IVMC). In total, 399 IVMC embryos were transferred.

RESULTS

Maturation rate for immature post-GVBD oocytes was 54.1%. G-2™PLUS (Vitrolife) medium provided significantly higher maturation rate (p < 0.001) than G-IVF™PLUS (Vitrolife) (65.7% vs. 42.5%, p < 0.001). Embryos in ET-IVMC in cleavage stage had an average morphological score of 6.8/10 (7.7 in ET-MII; p < 0.001). Regarding reproductive outcomes, ET-IVMC gave 11.1% biochemical pregnancy rate, 10.0% clinical pregnancy rate, 7.8% ongoing pregnancy rate, and 5.6% live birth rate.

CONCLUSIONS

Embryos arising from IVMC oocytes resulted in a live birth rate of 5.6%. We suggest that in vitro maturation of denuded immature post-GVBD oocytes should be performed at the very least when few MII are collected, and likely in all patients, as they provide acceptable maturation and fertilization rates, and a sizeable increase in live birth.

Human oocyte maturation in vitro is improved by co-culture with cumulus cells from mature oocytes

The conventional method of human oocyte maturation in vitro in the presence of gonadotrophins continues to be a relatively low-success procedure in the assisted conception programme owing to suboptimal maturation conditions in the absence of an ovarian 'niche' and poor understanding of this procedure at the molecular level in oocytes. In this study, the gene expression profiles of human oocytes were analysed according to their manner of maturation: in vivo (in the ovaries) or in vitro (matured either by the conventional method or by a new approach - co-cultured with cumulus cells of mature oocytes from the same patient). Our results show that the in-vitro maturation procedure strongly affects the gene expression profile of human oocytes, including several genes involved in transcriptional regulation, embryogenesis, epigenetics, development, and the cell cycle. The in-vitro maturation of oocytes co-cultured with cumulus cells from mature oocytes provides an ovarian 'niche' to some degree, which improves oocyte maturation rates and their gene expression profile to the extent that they are more comparable to oocytes that naturally mature in the ovarian follicle.

Delayed intracytoplasmic sperm injection (ICSI) with trophectoderm biopsy and preimplantation genetic screening (PGS) show increased aneuploidy rates but can lead to live births with single thawed euploid embryo transfer (STEET)

PURPOSE

The aim of this study was to report the results of IVF with trophectoderm biopsy and preimplantation genetic screening (PGS) following delayed intracytoplasmic sperm injection (ICSI).

METHODS

Patients undergoing IVF with PGS and delayed ICSI were included in the study. Indications for delayed ICSI included absent or poor fertilization via standard insemination or more than 50 % immature oocytes, noted post-cumulus stripping for standard ICSI procedure. Delayed ICSI was performed the day after retrieval due to absent or poor fertilization. The immature oocytes were kept in extended culture, and if demonstrated maturity, ICSI was performed. Primary outcome included fertilization rate and blastocyst stage formation, defined by the number of blastocysts for biopsy. Secondary outcome included aneuploidy rate and pregnancy outcomes following single thawed euploid embryo transfers (STEET).

RESULTS

Sixteen patients with delayed ICSI were included in the study. Twelve were due to poor fertilization and four secondary to immature oocytes. A total of 219 oocytes were retrieved; ten were frozen upon patient request, 168 had standard insemination, and 13 had routine ICSI on the day of retrieval. A total of 129 oocytes underwent delayed ICSI. Sixty-three (49 %) fertilized, 19 (14.7 %) reached blastocysts for biopsy; fivw of which were chromosomally normal (26.3 %). Three patients underwent STEET of a delayed ICSI embryo; all three resulted in live births, including one embryo biopsied on day 8 of development.

CONCLUSION

Fertilization failure or an excessive proportion of immature oocytes in an IVF cycle, necessitating delayed ICSI, showed equivalent fertilization and blast formation rates. With the implementation of trophectoderm biopsy and PGS, these embryos can lead to healthy live born babies.

Telomerase activity in pregnancy complications (Review)

Telomeres are specific DNA regions positioned at the ends of chromosomes and composed of functional non-coding repeats. Upon cell division, the telomeres decrease in length by a preordained amount. When the telomeres become critically short, cells lose the ability to divide and enter a specific functioning mode designated as 'cellular senescence'. However, human tissues express an enzyme that deters the shrinking of the telomeres, the telomerase. Due to its ability to maintain telomere length, the telomerase slows down and possibly suspends the aging of the cells. In regard to this, solid evidence demonstrates that female human fertility decreases with increased maternal age and that various adverse factors, including alterations in telomerase activity, can contribute to age-associated infertility in women. The fact that telomerase activity is regulated in a time- and location-dependent manner in both embryo and placental tissues, highlights it potential importance to the successful completion of pregnancy. Since maternal age is a crucial determining factor for the success of in vitro and in vivo fertilization, numerous studies have focused on telomerase activity and its correlation with mammalian fertilization, as well as the following cleavage and pre-implantation developmental processes. Associations between telomerase activity and pregnancy complications have been previously observed. Our aim in this review was to summarize and critically discuss evidence correlating telomerase activity with pregnancy complications.

The potential role of granulosa cells in the maturation rate of immature human oocytes and embryo development: A co-culture study

Objective

In order to increase the number of mature oocytes usable for intracytoplasmic sperm injection (ICSI), we aimed to investigate the effect of co-culturing granulosa cells (GCs) on human oocyte maturation in vitro, the fertilization rate, and embryo development.

Methods

A total of 133 immature oocytes were retrieved and were randomly divided into two groups; oocytes that were cultured with GCs (group A) and oocytes that were cultured without GCs (group B). After in vitro maturation, only oocytes that displayed metaphase II (MII) underwent the ICSI procedure. The maturation and fertilization rates were analyzed, as well as the frequency of embryo development.

Results

The mean age of the patients, their basal levels of follicle-stimulating hormone, and the number of oocytes recovered from the patients were all comparable between the two study groups. The number of oocytes that reached MII (mature oocytes) was 59 out of 70 (84.28%) in group A, compared to 41 out of 63 (65.07%) in group B (p=0.011). No significant difference between fertilization rates was found between the two study groups (p=0.702). The embryo development rate was higher in group A (33/59, 75%) than in group B (12/41, 42.85%; p=0.006). The proportion of highest-quality embryos and the blastocyst formation rate were significantly lower in group B than in group A (p=0.003 and p<0.001, respectively).

Conclusion

The findings of the current study demonstrate that culturing immature human oocytes with GCs prior to ICSI improves the maturation rate and the likelihood of embryo development.

High fat diet induced obesity alters ovarian phosphatidylinositol-3 kinase signaling gene expression

Insulin regulates ovarian phosphatidylinositol-3-kinase (PI3 K) signaling, important for primordial follicle viability and growth activation. This study investigated diet-induced obesity impacts on: (1) insulin receptor (Insr) and insulin receptor substrate 1 (Irs1); (2) PI3K components (Kit ligand (Kitlg), kit (c-Kit), protein kinase B alpha (Akt1) and forkhead transcription factor subfamily 3 (Foxo3a)); (3) xenobiotic biotransformation (microsomal epoxide hydrolase (Ephx1), Cytochrome P450 isoform 2E1 (Cyp2e1), Glutathione S-transferase (Gst) isoforms mu (Gstm) and pi (Gstp)) and (4) microRNA's 184, 205, 103 and 21 gene expression. INSR, GSTM and GSTP protein levels were also measured. Obese mouse ovaries had decreased Irs1, Foxo3a, Cyp2e1, MiR-103, and MiR-21 but increased Kitlg, Akt1, and miR-184 levels relative to lean littermates. These results support that diet-induced obesity potentially impairs ovarian function through aberrant gene expression.

The effect of human cumulus cells on the maturation and developmental potential of immature oocytes in ICSI cycles

PURPOSE

To investigate the effect of human cumulus cells on the maturation and developmental potential of immature oocytes in ICSI cycles.

METHODS

Immature oocytes were randomly divided into two groups: the cumulus-denuded oocyte group (group A) and the cumulus-intact oocyte group (group B). Only oocytes that reached metaphase II (MII) stage after in vitro maturation were used in the ICSI procedure. In vivo mature sibling MII oocytes served as the control group. Maturation rate, fertilization rate, embryo quality and developmental potential were examined.

RESULTS

There was no significant difference in maturation rate between group A (68.16%) and group B (70.49%; P > 0.05). The total fertilization rate among the three groups was comparable (P > 0.05), while the zygotes with two pronuclei in group A (74.59%) or group B (75.97%) were significantly lower than those in control group (84.29%; P < 0.05). The available embryo rate in group A (11.49%) was markedly lower than that in group B (27.66%; P < 0.05), and both of them were significantly lower than that in control group (62.38%; P < 0.05). The proportion of ≥6-cell embryos in group B (45.74%) was notably higher than in group A (26.44%; P < 0.05), and both were markedly lower than in control group (65.92%; P < 0.05). The proportion of embryos with <10% fragmentation in group A (13.79%) was significantly lower than in group B (29.79%; P < 0.05), and both were notably lower than in control group (42.98%; P < 0.05).

CONCLUSIONS

The presence of cumulus cells surrounding the immature oocytes during IVM before ICSI had no influence on nuclear maturation and fertilization, but leads to better subsequent embryonic development. This is perhaps mediated by an improvement in cytoplasmic maturation.

Effects of cumulus cells on in vitro maturation of oocytes and development of cloned embryos in the pig

The purpose of this study was to investigate the role of porcine cumulus cells (CC) in oocyte maturation and somatic cell nuclear transfer (SCNT) embryo development in vitro. Denuded pig oocytes were co-cultured with CC or routinely cultured in maturation medium without a feeder layer. Porcine CC inactivated with mitomycin C or non-inactivated were used for the feeder layer in co-culture with porcine SCNT embryos to investigate comparatively the developmental competence of cloned embryos. The DNA damage aspects of apoptosis and expression pattern of genes implicated in apoptosis (Fas/FasL) as well as the mRNA expression of DNA methyltransferase (Dnmt1, Dnmt3a) of porcine SCNT embryos were also evaluated by comet assay or real-time RT-PCR, respectively. The results showed that co-culture with CC improved the extrusion rate of pbI (49.3% vs 31.5%, p<0.05) and survival rate (75.7% vs 53.3%, p<0.05) of denuded oocytes, but had no effects on blastocyst developmental rate or 2-cell-stage survival rate of in vitro fertilization embryos. Co-culture with CC inactivated by mitomycin C improved the blastocyst developmental rate (26.6% vs 13.0%, p<0.05) and decreased the apoptotic incidence (27.6% vs 46.2%, p<0.05) of porcine cloned embryos. Co-culture with inactivated CC reduced Fas and FasL mRNA expression of cloned embryos at the blastocyst stage compared with NT controls (p<0.05), but there were no differences in Dnmt1 and Dnmt3a mRNA expression among groups. Co-culture with inactivated cumulus cell monolayer significantly increased blastocyst formation and decreased the apoptotic incidence in porcine cloned embryos during in vitro development.

Women with high telomerase activity in luteinised granulosa cells have a higher pregnancy rate during in vitro fertilisation treatment

OBJECTIVE

To study the effect of telomerase activity (TA) in human luteinised granulosa cells (GCs) on the outcome of in vitro fertilisation treatment.

METHODS

Fifty-six women, aged 23 to 39 years, were enrolled and divided into four groups according to their levels of TA.

RESULTS

Seventeen cases in group A exhibited nondetectable TA, 16 cases in group B expressed low levels of TA (between 0.1 and 0.65 OD × mm), 14 cases in group C expressed moderate TA levels (between 0.66 and 1.00 OD × mm) and 9 cases in group D expressed high levels of TA (more than 1.00 OD × mm). The level of total serum testosterone (T) was significantly higher in groups C and D than in group A (1.43±0.10 vs. 1.08±0.11 nmol/L, P<0.030 and 1.56±0.08 vs. 1.08±0.11 nmol/L, P<0.005, respectively). The TA level was positively correlated with T (r=0.291, P<0.011). No obvious differences were observed in rates of fertilisation, cleavage, mature oocyte formation or good-quality embryos among the groups. The patients in group D exhibited the highest rates of embryo implantation and clinical pregnancy (with rates of 52.63% and 77.78%, respectively, compared with 18.92% and 29.41% in group A, 25.71% and 37.50% in group B and 48% and 50% in group C, with P<0.018 and P=0.112, respectively). The patients in group D also had a greater likelihood of becoming pregnant than those in group A (OR: 9.703, P < 0.023), group B (OR: 14.765, P<0.009) or group C (OR: 5.560, P=0.103).

CONCLUSIONS

Luteinised GCs have a certain potential for proliferation and TA of luteinised GCs may predict the clinical outcomes of IVF treatment. Some unknown regulatory mechanisms between TA and T should be studied in further trials.

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.

Evaluation of the developmental potential of metaphase I oocytes from stimulated intracytoplasmic sperm injection cycles

The objective of the present study was to evaluate the developmental potential and clinical application value of metaphase I (MI) oocytes obtained from stimulated intracytoplasmic sperm injection (ICSI) cycles. ICSI was performed on MI oocytes immediately after denudation (Group A), or on in vitro-matured (IVM) oocytes following culture; oocytes in culture were further divided into two groups, being cultured for either 3–5 h (Group B) or 24–28 h (Group C). Metaphase II oocytes from the same cycle(s) isolated for ICSI served as the control group (Group D). The rates of normal fertilisation, cleavage and high-quality embryos were compared among the four groups. High-quality embryos were transferred whenever possible, and pregnancy rates were evaluated. Results showed that normal fertilisation rates for Groups B, C and D were significantly higher than that of Group A (68.6%, 57.8%, 74.5% and 30.1%, respectively; P < 0.01). The rate of high-quality embryos in Group B was comparable with Group D; the rate for Group C was significantly lower than that of the other groups (P < 0.05). Two clinical pregnancies were achieved after transfer of embryos from IVM oocytes. In vitro maturation of MI oocytes for a short period of time may increase the number of available embryos; however, overnight in vitro culture of MI oocytes did not improve results.

The role of co-culture systems on developmental competence of preimplantation mouse embryos against pH fluctuations

PURPOSE

To determine the effect of pH fluctuations of culture media, and the role of co-culture systems on embryo development.

METHODS

Mouse embryos were incubated in phosphate buffered solutions (PBSs) with different pH for various lengths of time. After 3 h incubation of embryos at various pH, the embryos were transferred into four media with human (HEF) and mouse (MEF) embryonic fibroblast cells, and without feeder cells; HTF and MEM-alpha. Developmental rate at day three (morula), four (expanded blastocyst) and five (hatching or hatched blastocyst) was evaluated.

RESULTS

Developmental rate at day three, four and five decreased when the incubation time at pH 6.2 and 8 increased to 3 h and more. In addition, significantly less embryos incubated at pH 6.2 and 8 developed to hatching and hatched blastocysts compared with pH 7.35. Embryos incubated at pH 6.2, co-cultured with MEF or HEF showed a significant improvement (P < 0.05) at day three in HEF compared to HTF, and at day five in MEF compared to HTF. At pH 8, a significant improvement (P < 0.05) was observed at day five in HEF and MEF compared to MEM-alpha.

CONCLUSIONS

Mouse 2-cell embryos could tolerate minor pH fluctuations, but that major pH changes affect subsequent development. Besides, feeder cells could improve embryo development, especially when embryos are prone to rise or fall in pH.

Live offspring from vitrified blastocysts derived from fresh and cryopreserved ovarian tissue grafts of adult mice

Ovarian tissue cryopreservation and transplantation can be used to preserve fertility for cancer patients. In this study, we assessed the viability and function of ovarian tissue from adult mice that was cryopreserved by solid surface vitrification or traditional slow-cooling using variousin vitroandin vivotechniques, including allotransplantation,in vitrooocyte maturation, embryo culturein vitro, blastocyst cryopreservation, embryo transfer, and development. The importance of cumulus cells for oocyte maturation, fertilization, and embryo development was investigated. Graft recovery, follicle survival, and oocyte retrieval was similar in control, vitrified, and slow-cooled groups. High rates of oocyte maturation, cleavage, and blastocyst formation were achieved, with no significant differences between the control, vitrified or slow-cooled ovarian tissue grafts. The presence of cumulus cells was important for oocyte maturation, fertilization, and subsequent development. Cumulus–oocyte complexes with no surrounding cumulus cells (N-COCs) or with an incomplete layer (P-COCs) had significantly lower rates of oocyte maturation and blastocyst formation than cumulus–oocyte complexes with at least one complete layer of cumulus cells (F-COCs; maturation rate: 63, 78 vs 94%; blastocyst rate: 29, 49 vs 80%). Live births were achieved using vitrified blastocysts derived from oocytes taken from vitrified and slow-cooled ovarian tissue heterotypic allografts. Successful production of healthy offspring from these vitrified blastocysts suggests that this technique should be considered as a useful stage to pause in the assisted reproduction pathway. This provides an alternative protocol for restoring fertility and offering cancer patients a better indication of their chances of pregnancy and live birth.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.

Effect of embryonic fibroblast cell co-culture on development of mouse embryos following exposure to visible light

PURPOSE

To determine the effects of visible light on development of mouse embryos and the potential of fibroblast cells to overcome deleterious effects of visible light on mouse preimplantation stage embryos.

METHODS

Two-cell mouse embryos were randomly allocated to un-exposed group (control) and exposed group receiving 1600 lx visible light for various time lengths. Both exposed and un-exposed embryos were co-cultured with either Mouse Embryonic Fibroblast (MEF) or Human Embryonic Fibroblast (HEF). Developmental rate of embryos at day 3 (morula), 4 (expanded blastocyst) and 5 (hatching or hatched blastocyst) was evaluated.

RESULTS

Exposure of embryos to visible light for 30 min decreased developmental rate significantly (P<0.01). Developmental rate of exposed embryos co-cultured with MEF (58%; p<0.05 both at day 4 and 5) and HEF (67%; P<0.01 both at day 4 and 5) was higher than control.

CONCLUSIONS

Visible light adversely affects embryo development in a time-dependent manner. Feeder cells may enhance embryo development particularly when suboptimal conditions are involved.

Effects of in vitro maturation on gene expression in rhesus monkey oocytes

In vitro oocyte maturation (IVM) holds great promise as a tool for enhancing clinical treatment of infertility, enhancing availability of nonhuman primates for development of disease models, and facilitating endangered species preservation. However, IVM outcomes have remained significantly below the success rates obtained with in vivo matured (VVM) oocytes from humans and nonhuman primates. A cDNA array-based analysis is presented, comparing the transcriptomes of VVM oocytes with IVM oocytes. We observe a small set of just 59 mRNAs that are differentially expressed between the two cell types. These mRNAs are related to cellular homeostasis, cell-cell interactions including growth factor and hormone stimulation and cell adhesion, and other functions such as mRNA stability and translation. Additionally, we observe in IVM oocytes overexpression of PLAGL1 and MEST, two maternally imprinted genes, indicating a possible interruption or loss of correct epigenetic programming. These results indicate that, under certain IVM conditions, oocytes that are molecularly highly similar to VVM oocytes can be obtained; however, the interruption of normal oocyte-somatic cell interactions during the final hours of oocyte maturation may preclude the establishment of full developmental competence.