Jin-Tae Chung

A 38 h interval between hCG priming and oocyte retrieval increases in vivo and in vitro oocyte maturation rate in programmed IVM cycles.

BACKGROUND Our aim was to evaluate whether extending the interval between human chorionic gonadotrophin (hCG) priming and immature oocyte retrieval increases the oocyte maturation rate following in vitro maturation (IVM). METHODS This study was performed retrospectively. IVM was performed on 113 polycystic ovary syndrome patients (n = 120 cycles). Oocyte collection was performed either 35 h (Group 1; n = 76) or 38 h (Group 2; n = 44) after 10 000 IU of hCG priming. Following oocyte retrieval, oocyte maturity was assessed and the remaining immature oocytes were cultured in IVM medium up to Day 2. RESULTS The number of in vivo matured oocytes collected was significantly higher in Group 2 (13.6%, 114/840 versus 7.3%, 96/1312 in Group 1) (P < 0.01); the oocyte maturation rate after Day 1 was significantly higher (P < 0.01) in Group 2 (46.3 versus 36.0% in Group 1); and clinical pregnancy (40.9 versus 25%) and implantation rates (15.6 versus 9.6%) were better in Group 2 than those in Group 1. CONCLUSIONS The results suggest that extending the period of hCG priming time from 35 to 38 h for immature oocyte retrieval promotes oocyte maturation in vivo and increases the IVM rate of immature oocytes. Therefore, oocyte retrieval after 38 h of hCG priming may improve subsequent pregnancy outcome in cycles programmed for IVM treatment.

Maturational and developmental competence of immature oocytes retrieved from bovine ovaries at different phases of folliculogenesis

Immature oocytes recovered from bovine ovaries were studied to determine if their maturational and developmental competence is affected by phase of folliculogenesis. Ovaries (a total of 39 pairs) were collected from a local abattoir. Following examination, each pair of ovaries was assigned to one of three groups, according to follicle size and with or without a corpus luteum: (i) early phase (n = 13 pairs): all follicles were <or=8 mm in diameter; (ii) late phase (n = 13 pairs): the largest follicle was >or=15 mm in diameter; (iii) luteal phase (n = 13 pairs): all follicles were <or=8 mm in diameter and there was a corpus luteum on one of the ovaries. All follicles were aspirated and cumulus-oocytes complexes (COC) were cultured in 1.0 ml maturation medium, TC-199 medium supplemented with 10% fetal bovine serum (FBS), 0.2 mmol pyruvate, and 75 mIU/ml FSH and LH (Humegon) at 38.5 degrees C in a humidified atmosphere of 5% CO(2) and 95% air for 24 h. Following maturation in vitro, the oocytes were inseminated with frozen-thawed semen and cultured for further development in vitro. The mean number of oocytes retrieved from early phase ovaries was 32 +/- 8.1 which was significantly higher (P < 0.05) than other phases (n = 20.1 +/- 5.4 and 22.7 +/- 6.9). The numbers of degenerated oocytes from early, late and luteal phase ovaries were not different (n = 1.6 +/- 0.7, 1.8 +/- 0.5 and 1.5 +/- 0.5, respectively). The rates of oocyte maturation (84.4%, 89.2% and 83.6%) and fertilization (53.5%, 53.3% and 51.3%) were not significantly different across the three groups. In addition, there were no significant differences in the rates of cleavage (77.9%, 79.9% and 73.9%) and blastocyst formation (27.4%, 33.0% and 30.4%) in the three groups. These results indicate that the maturational and developmental competence of immature oocytes is not affected by the phase of folliculogenesis.

Comparison of in-vitro maturation cycles with and without in-vivo matured oocytes retrieved

This study compared the embryological characteristics and clinical outcome of in-vitro maturation (IVM) treatment cycles with and without in-vivo matured oocytes collected following human chorionic gonadotrophin (HCG) priming. The patients were administered 10,000 IU of HCG subcutaneously when endometrial thickness reached > or =6 mm and oocyte collection was performed 35-36 h after HCG administration. The clinical outcome and embryological aspects were analysed between IVM cycles with (group 1) and without (group 2) in-vivo matured oocytes. In group 1, three (range 1-12) in-vivo matured oocytes per patient were retrieved on average. The number of good quality embryos derived from in-vivo matured oocytes in group 1 was significantly higher than those derived from in-vitro matured oocytes in group 1 and group 2 (P < 0.05). However, there was no difference between the number of good quality embryos produced from in-vitro matured oocytes in the two groups. There were 12 clinical pregnancies (40.0%) in group 1, and seven pregnancies (23.3%) in group 2. These results suggest that IVM cycles with in-vivo matured oocytes resulted in a good clinical pregnancy rate, which could be explained by the superior quality of embryos derived from the in-vivo matured oocytes.

Selection of the optimal day for oocyte retrieval based on the diameter of the dominant follicle in hCG-primed in vitro maturation cycles

BACKGROUND The efficiency of in vitro maturation (IVM) techniques is suboptimal compared with controlled ovarian stimulation combined with IVF cycles, and studies are needed to identify factors that predispose IVM cycles to success or failure. We compared the outcome of IVM cycles with different dominant follicle (DF) size at oocyte retrieval following hCG priming. METHODS IVM was performed in 160 patients with polycystic ovaries (171 cycles). We administered 10,000 IU hCG s.c. 35-38 h before oocyte collection when endometrial thickness reached at least 6 mm. IVM cycles were retrospectively analyzed according to DF diameter as follows; Group 1: DF diameter <or=10 mm, Group 2: between 10 and 14 mm, Group 3: >14 mm. RESULTS A positive correlation was observed between DF size and number of in vivo matured oocytes collected (Group 1, 2 and 3 = 6.9, 10.6 and 15.1%, respectively). The rates of IVM, fertilization and embryo development were similar among the sibling immature oocytes collected from the three groups. However, clinical pregnancy rate in Group 2 (40.3%) was higher than Group 3 (17.1%) (P < 0.05). Moreover, implantation rates in Groups 1 (13.6%) and 2 (14.3%) were higher than Group 3 (4.9%) (P < 0.01). CONCLUSIONS Our results suggest that oocyte collection in IVM cycles should be performed when the DF is 14 mm diameter or less. Sibling immature oocytes may be affected detrimentally if a DF >14 mm is present at oocyte collection.

Clinical definition paper on in vitro maturation of human oocytes

In vitro maturation (IVM) of human oocytes is a reproductive technique which has been practiced for 25 years and is gaining popularity. However, the techniques used for IVM differ substantially across clinics and they result in extremely variable pregnancy rates, partially due to some of these differences in protocols. Such differences include the use in some cycles of hCG triggering prior to oocyte retrieval and the use of a few days of gonadotrophin treatment to support moderate follicle growth. Other important factors are patient selection (including those with polycystic ovaries or decreased ovarian reserve), the number of embryos transferred and cleavage-stage embryo or blastocyst transfer. There are also substantial differences of opinion among clinicians regarding IVM and what it implies. Due to the large variation in protocols, a decision was made to write this paper in an attempt to introduce uniformity when comparing treatments and outcomes of IVM. A clinical definition of IVM was developed: The retrieval of oocytes from small and intermediate sized follicles in an ovary before the largest follicle has surpassed 13 mm in mean diameter. The use of short gonadotrophin stimulation should be acknowledged. However, it should be stated that metaphase II oocytes also have the potential to be collected at that time in the cycles associated with either hCG or GnRH agonist priming. Many feel this is not IVM because some mature oocytes are retrieved, therefore, we recommend renaming this procedure either natural cycle IVF or modified natural cycle IVF (if gonadotrophin stimulation is given) with early triggering, combined with IVM The percentage as well as the absolute number of mature oocytes at retrieval should be indicated. The use of these titles will allow transparency when comparing results of IVM cycles.

Comparison of survival rate of cleavage stage embryos produced from in vitro maturation cycles after slow freezing and after vitrification

Significantly more embryos survived the vitrification procedure compared to slow freezing (85.5% vs. 61.8%) in cleavage-stage human embryos produced from in vitro maturation cycles, suggesting that vitrification is more efficient than slow freezing for cryopreservation.

Effect of polyvinylpyrrolidone on bovine oocyte maturation in vitro and subsequent fertilization and embryonic development

The exact role of polyvinylpyrrolidone (PVP) in culture medium for oocyte maturation is still largely unknown. Bovine cumulus-oocyte complexes (COC) were cultured in in-vitro maturation (IVM) medium supplemented with 10% fetal bovine serum (FBS), 0.3% PVP (K-90) or 10% serum substitute supplement (SSS) respectively. The rates of oocyte maturation, fertilization and early embryonic development were evaluated. In addition, the status of DNA fragmentation in the oocytes was determined by comet assay, and the ratio of trophectoderm (TE) cells and inner cell mass (ICM) in blastocysts was determined by differential staining. Furthermore, the percentage of apoptotic cells in the blastocysts was examined by TUNEL assay. The results indicated that the effect of PVP in IVM medium was similar to FBS in terms of oocyte maturation and subsequent embryonic development. However, the addition of SSS in IVM medium retarded further embryonic development and resulted in more oocyte DNA fragmentation and a higher ratio of TE cells and ICM in the blastocysts. However, the number of apoptotic cells in blastocysts was similar among the three groups. These results suggest for the first time that the addition of PVP in oocyte maturation medium is not only a suitable substitute for serum but is also beneficial to in-vitro oocyte maturation.

High survival and hatching rates following vitrification of embryos at blastocyst stage: a bovine model study

Cryopreservation of embryos at the blastocyst stage may provide an effective method to increase the cumulative pregnancy rate for each treatment cycle of ovarian-stimulated IVF. The objective of this study was to evaluate the survival rate and hatching rate of bovine blastocysts following vitrification using a method designed for oocytes, with a view to introducing this methodology into human assisted reproduction technology and reproductive medicine. Bovine blastocysts were produced from abattoir materials subjected to in-vitro maturation and in-vitro fertilization. Survival rate of the bovine blastocysts was 100% (94/94) following vitrification using a method designed for oocyte cryopreservation. There was no difference in the hatching rate of the bovine blastocysts between control (62.5%: 60/96) and vitrified (61.7%: 58/94) groups. The number of dead cells in the blastocysts was not significantly different between control (5.0 +/- 2.9) and vitrified (9.5 +/- 4.0) groups. In conclusion, the results of this study indicate that bovine blastocysts can be vitrified successfully using a procedure designed for oocyte cryopreservation. It is possible that this method may also be successful for the cryopreservation of human embryos. A further study into this is currently being organized.

Effect of centrifugation on early embryonic development and parthenogenetic activation of bovine oocytes matured in vitro

This study examined the fertilization, early developmental competence and capacity for parthenogenetic activation of bovine oocytes matured in vitro after centrifugation. Immature oocytes were cultured in tissue culture medium 199 supplemented with 10% fetal bovine serum and 75 mIU mL(-1) FSH + LH at 5% CO2 to facilitate maturation. After culture for 24 or 30 h, the metaphase-II stage oocytes were centrifuged at 3000, 5000, 7000 or 10000g for 5 min before in vitro fertilization or parthenogenetic activation. Frozen-thawed bull semen was used for in vitro fertilization. For parthenogenetic activation, the oocytes were exposed to 20 microM calcium ionophore A23187 for 5 min at room temperature. Fertilization rates were not different between control and treatment groups (87.7% v. 74.6%, 73.4%, 75.9% and 76.4% respectively). Also, there were no differences in early embryonic development between control and treatment groups (rates of blastocyst formation were 21.1% v 20.2%, 28.8%, 31.2% and 24.1% respectively). When the oocytes were centrifuged at various speeds alone, the activation rate of oocytes was significantly higher (P < 0.05) in the 10000g treatment group compared with control (10.8% v 0.0%). There were no differences in the activation rates of oocytes between control and treatment groups at speeds up to 7000g (70.9% v. 71.9%, 78.3% and 77.2% respectively) after centrifugation and stimulation with Ca(2+)-ionophore. However, the activation rate of oocytes was significantly higher (P < 0.05) in the 10000g treatment group compared with control (70.9% v. 83.1%). In addition, the percentage of activated oocytes with diploid formation was significantly higher in the oocytes after centrifugation at 10000g and stimulation with calcium ionophore A23187 than in the control (18.4% v 7.1%). These results indicate that centrifugation of oocytes matured in vitro has no detrimental effect on fertilization and subsequent early embryonic development. They also indicate that the oocytes might be parthenogenetically activated after centrifugation and that high-speed centrifugation may induce activation of some oocytes. The results suggest that the optimal speed for centrifugation of bovine oocytes might be < or = 7000g to enhance the visibility of nuclear elements for further micromanipulation.

Fertilization and embryo development with spermatozoa obtained from testicular sperm extraction into oocytes generated from human chorionic gonadotropin-primed in vitro maturation cycles

OBJECTIVE To evaluate the fertilization rate and embryo development resulting from intracytoplasmic sperm injection (ICSI) of spermatozoa retrieved by testicular sperm extraction (TESE) in hCG-primed in vitro maturation (IVM) cycles. DESIGN Case-control study. SETTING University teaching hospital. PATIENT(S) Twenty-four IVM cycles were performed in 21 patients (mean age, 32.3 ± 2.4 years) with polycystic ovaries (PCO) whose partners were nonobstructive azoospermic. Twelve cycles where IVM oocytes were also retrieved were compared with a control group consisting of age-matched IVM cycles with ICSI using ejaculated spermatozoa (n = 12). INTERVENTION(S) In vitro maturation treatment with TESE sperm. MAIN OUTCOME MEASURE(S) Fertilization and embryo development between sibling oocytes matured in vivo and in vitro. RESULT(S) Eight singleton pregnancies and one twin pregnancy were obtained after ET (9/24, 37.5%). In the 12 IVM cycles where in vivo-matured oocytes were also obtained, the fertilization rate after TESE-ICSI was significantly higher in in vivo-matured oocytes than in sibling in vitro-matured oocytes (84.2% vs. 53.2%). The proportion of good quality embryos was also higher (63.5% vs. 40.2%). In the control group of cycles with ejaculated spermatozoa, there was no difference in fertilization rates between sibling oocytes matured in vivo and in vitro (84.6% vs. 79.6%). CONCLUSION(S) Our results suggest that IVM of immature oocytes combined with TESE-ICSI is an option for couples with PCO and azoospermia. However, there are lower fertilization and good quality embryo rates achieved when TESE-ICSI was done with in vitro-matured oocytes. Additional studies are necessary to determine the role of this treatment combination.