In vitro growth and maturation as well as fertilization of mouse preantral oocytes from vitrified ovaries

Sorbitol accumulation decreases oocyte quality in aged mice by altering the intracellular redox balance

Sorbitol is a product of glucose metabolism through the polyol pathway. Many studies have demonstrated that excessive sorbitol can disrupt the intracellular redox balance. However, we still know very little about the impact of excessive intracellular sorbitol on oocyte quality, oocyte maturation, and embryo developmental potential. This study explored whether intracellular sorbitol accumulates in the oocytes of aged mice during in vitro maturation (IVM) and what roles sorbitol plays in oocyte development and maturation. Our results showed that sorbitol levels were significantly higher in in vitro-matured oocytes from aged mice than in oocytes from young mice (14.08 ± 3.78 vs. 0.23 ± 0.04 ng/oocyte). The expression of aldose reductase (AR) mRNA was significantly higher in the in vitro-cultured oocytes from 9-month-old mice than prior to culture. To decrease the excessive intracellular sorbitol in oocytes from aged mice, sorbinil, a specific inhibitor of aldose reductase, was supplemented in IVM medium, and the sorbitol level was significantly decreased (14.08 ± 3.78 vs. 0.48 ± 0.19 ng/oocyte). Our results indicated that the percentage of oocytes with first polar body extrusion (PBE) was significantly higher in the sorbinil group than in the aged group (82.4% ± 7.2% vs. 66.1% ± 6.9%), and the content of sorbitol was drastically increased in the aged group. The ROS fluorescence intensity in the sorbinil group was drastically lower than that in the aged group, while the GSH fluorescence intensity was significantly higher. Interestingly, SOD1 was upregulated in the sorbinil group. The present study suggests that excessive sorbitol accumulation is induced during IVM in aged mouse oocytes, which negatively influences oocyte quality by altering the intracellular redox balance. Inhibition of sorbitol accumulation may be a potential method to improve the nuclear maturation of aged oocytes.

Primordial follicle survival of goat ovarian tissue after vitrification and transplantation on chorioallanthoic membrane

Background

Ovarian tissue vitrification is an alternative fertility preservation procedure for young female patients prior to gonadotoxic treatment. Primordial follicle loss might be a potential issue for vitrification and transplantation procedures. This study aimed to evaluate primordial follicle density and deoxyribonucleic acid (DNA) fragmentation in each stage of the preservation procedure of goat ovarian tissue. Follicle density and DNA fragmentation were examined microscopically after staining with hematoxylin eosin and TUNEL assay, respectively. Both parameters were compared between fresh, fresh-transplanted, vitrification, and vitrification-transplanted groups.

Results

A significant decrease was observed in the primordial follicle proportion after vitrification and transplantation compared to the primordial follicle proportion in the fresh group (88.09% vs 52.42%, p < 0.05, 95% CI 11.54, 66.94). There was no significant difference in DNA fragmentations of primordial follicles between each group (p > 0.05).

Conclusions

The vitrification and transplantation process of goat ovarian strips could cause the primordial follicles loss and DNA damage of the follicles. However, primordial follicles loss and DNA damage were not significantly different in each procedure.

Ovarian tissue vitrification is more efficient than slow freezing to preserve ovarian stem cells in CF-1 mice

OBJECTIVE

The aim of this study was to investigate the efficacy of protocols for mice ovary cryopreservation to compare the differences in Mouse Vasa Homologue expression (a germline cell marker) and ovarian viability after vitrification or slow freezing.

METHODS

Female CF1 mice aged 40-45 days were randomly divided into three groups: Control, vitrification or slow freezing. Their ovaries were surgically removed, rinsed in saline solution and cryopreserved. For vitrification, we used a commercial protocol and for slow freeze, we used 1.5 M ethylene glycol (EG) as cryoprotectant. After that, the ovaries were processed for histological an immunohistochemical analysis, and counting of primordial, primary, pre-antral and antral follicles.

RESULTS

No significant difference was found in the proportion of high-quality primordial, primary and pre-antral follicles after thawing/warming in the slow freezing and vitrification groups. The immunohistochemistry for MVH antibody demonstrated that the slow freeze group had a higher number of unmarked cells (p=0.012), indicating a harmful effect on the MVH expression in the ovarian tissue, where the cell structure is complex.

CONCLUSION

Although both protocols indicated similar results in the histological analysis of follicular counts, the vitrification protocol was significantly better to preserve ovarian stem cells, an immature germ cell population. These cells are able to self-renew having regeneration potential, and may be effective for the treatment of ovarian failure and consequently infertility.

Stepped vitrification technique for human ovarian tissue cryopreservation

The advantage of stepped vitrification (SV) is avoiding ice crystal nucleation, while decreasing the toxic effects of high cryoprotectant concentrations. We aimed to test this method for human ovarian tissue cryopreservation. Ovarian cortex was taken from 7 fertile adult women. Samples were subjected to an SV protocol performed in an automatic freezer, which allowed sample transfer to ever higher concentrations of dimethyl sulfoxide (DMSO) as the temperature was reduced. Histological evaluation of the vitrified-warmed tissue showed large numbers of degenerated follicles after 24 hours of in vitro culture. We therefore evaluated DMSO perfusion rates by X-ray computed tomography, ice crystal formation by freeze-substitution, and cell toxicity by transmission electron microscopy, seeking possible reasons why follicles degenerated. Although cryoprotectant perfusion was considered normal and no ice crystals were formed in the tissue, ultrastructural analysis detected typical signs of DMSO toxicity, such as mitochondria degeneration, alterations in chromatin condensation, cell vacuolization and extracellular matrix swelling in both stromal and follicular cells. The findings indicated that the method failed to preserve follicles due to the high concentrations of DMSO used. However, adaptations can be made to avoid toxicity to follicles caused by elevated levels of cryoprotectants.

Slow-freezing versus vitrification for human ovarian tissue cryopreservation

PURPOSE

Ovarian tissue can be cryopreserved prior to chemotherapy using either the slow-freezing or the vitrification method; however, the data on the equality of the procedures are still conflicting. In this study, a comparison of the cryo-damage of human ovarian tissue induced by either vitrification or slow-freezing was performed.

METHODS

Ovarian tissue from 23 pre-menopausal patients was cryopreserved with either slow-freezing or vitrification. After thawing/warming, the tissue was histologically and immunohistochemically analyzed and cultured in vitro. During tissue culture the estradiol release was assessed.

RESULTS

No significant difference was found in the proportion of high-quality follicles after thawing/warming in the slow-freezing and vitrification group, respectively (72.7 versus 66.7 %, p = 0.733). Estradiol secretion by the ovarian tissue was similar between groups during 18 days in vitro culture (area-under-the-curve 5,411 versus 13,102, p = 0.11). Addition of Sphingosine-1-Phosphate or Activin A to the culture medium did not alter estradiol release in both groups. The proportion of Activated Caspase-3 or 'Proliferating-Cell-Nuclear-Antigen' positive follicles at the end of the culture period was similar between slow-freezing and vitrification.

CONCLUSION(S)

Slow-freezing and vitrification result in similar morphological integrity after cryopreservation, a similar estradiol release in culture, and similar rates of follicular proliferation and apoptosis after culture.

Optimal vitrification protocol for mouse ovarian tissue cryopreservation: effect of cryoprotective agents and in vitro culture on vitrified-warmed ovarian tissue survival

STUDY QUESTION

What is the optimal vitrification protocol according to the cryoprotective agent (CPA) for ovarian tissue (OT) cryopreservation?

SUMMARY ANSWER

The two-step protocol with 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) for 10 min then 20% EG, 20% DMSO and 0.5 M sucrose for 5 min showed the best results in mouse OT vitrification.

WHAT IS KNOWN ALREADY

Establishing the optimal cryopreservation protocol is one of the most important steps to improve OT survival. However, only a few studies have compared vitrification protocols with different CPAs and investigated the effect of in vitro culture (IVC) on vitrified-warmed OT survival. Some recent papers proposed that a combination of CPAs has less toxicity than one type of CPA. However, the efficacy of different types and concentrations of CPA are not yet well documented.

STUDY DESIGN, SIZE, DURATION

A total of 644 ovaries were collected from 4-week-old BDF1 mice, of which 571 ovaries were randomly assigned to 8 groups and vitrified using different protocols according to CPA composition and the remaining 73 ovaries were used as controls. After warming, each of the eight groups of ovaries was further randomly divided into four subgroups and in vitro cultured for 0, 0.5, 2 and 4 h, respectively. Ovaries of the best two groups among the eight groups were autotransplanted after IVC.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The CPA solutions for the eight groups were composed of EDS, ES, ED, EPS, EF, EFS, E and EP, respectively (E, EG; D, DMSO; P, propanediol; S, sucrose; F, Ficoll). The IVC medium was composed of α-minimal essential medium, 10% fetal bovine serum and 10 mIU/ml follicle-stimulating hormone (FSH). Autotransplantation of vitrified-warmed OTs after IVC (0 to 4 h) using the EDS or ES protocol was performed, and the grafts were recovered after 3 weeks. Ovarian follicles were assessed for morphology, apoptosis, proliferation and FSH level.

MAIN RESULTS AND THE ROLE OF CHANCE

The percentages of the morphologically intact (G1) and apoptotic follicles in each group at 0, 0.5, 2 and 4 h of IVC were compared. For G1 follicles at 0 and 4 h of IVC, the EDS group showed the best results at 63.8 and 46.6%, respectively, whereas the EP group showed the worst results at 42.2 and 12.8%, respectively. The apoptotic follicle ratio was lowest in the EDS group at 0 h (8.1%) and 0.5 h (12.7%) of IVC. All of the eight groups showed significant decreases in G1 follicles and increases in apoptotic follicles as IVC duration progressed. After autotransplantation, the EDS 0 h group showed a significantly higher G1 percentage (84.9%) than did the other groups (42.4-58.8%), while only the ES 4 h group showed a significant decrease in the number of proliferative cells (80.6%, 87.6-92.9%). However, no significant differences in apoptotic rates and FSH levels were observed between the groups after autotransplantation.

LIMITATIONS, REASONS FOR CAUTION

The limitation of this study was the absence of in vitro fertilization using oocytes obtained from OT grafts, which should be performed to confirm the outcomes of ovarian cryopreservation and transplantation.

WIDER IMPLICATIONS OF THE FINDINGS

We compared eight vitrification protocols according to CPA composition and found the EDS protocol to be the optimal method among them. The data presented herein will help improve OT cryopreservation protocols for humans or other animals.

In vitro development of human primordial follicles to preantral stage after vitrification

PURPOSE

The aim was to culture primordial follicles in vitro to reach preantral stage in vitrified human ovarian tissue.

METHODS

Ovarian tissue samples were obtained from six women. Tissue strips were vitrified by infiltration with a cryoprotectant followed by mounting on a stainless steel carrier. After culturing for 7 days the morphology and developmental stages of follicles enclosed in fresh and vitrified groups were analyzed.

RESULTS

High proportion of viable follicles in vitrified ovarian strips was obtained. After culturing for 7 days the percentage of secondary and preantral follicles increased significantly (P < 0.05) whereas primordial and transitory follicles showed a significant decrease (P < 0.05) compared to their respective counterparts at day 0 of culture.

CONCLUSIONS

Vitrification of ovarian strips with an improved carrier device and culturing of follicles in ovarian strips after warming yielded developed follicles with high viability and morphological integrity that may be suitable for use in fertility preservation among cancer patients.

In vitro growth of mouse preantral follicles: effect of animal age and stem cell factor/insulin-like growth factor supplementation

OBJECTIVE

To determine whether animal age impacts in vitro preantral follicle growth. Effects of hCG, stem cell factor (SCF), and/or insulin-like growth factor (IGF) supplementation in growth medium were also investigated.

METHODS

Intact preantral follicles were mechanically isolated from fresh ovaries of BDF1 mice and cultured in growth medium for 9 to 11 days. Surviving follicles with antrum formation were transferred to maturation medium for 14 to 18 hours. Follicle survival, antrum formation, and retrieval of metaphase II (MII) oocytes were compared among three age categories (4-5, 7-8, and 10-11 week-old). By using 7- to 8-week-old mice, preantral follicles were cultured in growth medium supplemented with hCG (0, 5, or 10 mIU/mL), SCF (50 ng/mL), IGF-1 (50 ng/mL), and SCF+IGF-1.

RESULTS

Seven- to eight-week-old mice showed a higher follicle survival and antrum formation and produced more MII oocytes compared to other groups. In the 7- to 8-week-old mice, supplementation of 5 mIU/mL hCG significantly enhanced the antrum formation but the percentage of MII oocytes was similar to that of the control. Supplementation of SCF+IGF-1 did not enhance follicle survival or antrum formation but the percentage of MII oocytes increased modestly (39.1%) than in the control (28.6%, statistically not significant).

CONCLUSION

Seven- to eight-week-old mice showed better outcomes in growth of preantral follicles in vitro than 4- to 5- or 10- to 11-week-old mice. Supplementation of hCG enhanced antrum formation and supplementation of SCF+IGF-1 yielded more mature oocytes; hence, these should be considered in the growth of preantral follicles in vitro.

Allotransplantation of cryopreserved prepubertal mouse ovaries restored puberty and fertility without affecting methylation profile of Snrpn-DMR

OBJECTIVE

To evaluate the genetic safety of vitrification on the methylation imprints and the development and fertility potential of prepubertal mouse ovaries.

DESIGN

Experimental animal study.

SETTING

University-based fertility center.

ANIMAL(S)

Institute of Cancer Research (ICR) 10-day-old female mice, 10-week-old adult female mice, and 12-week-old adult male mice.

INTERVENTION(S)

Vitrification of juvenile mouse ovaries was performed using ED20 and EG5.5/30 solutions followed by retrieval of fresh and vitrified-warmed germinal vesicle (GV) oocytes for Snrpn differentially methylated regions (DMR) methylation analyses, collection of mature oocytes from superovulated ovarian grafts, in vitro fertility(IVF), and early embryonic development after heterotopic allotransplantation.

MAIN OUTCOME MEASURE(S)

Analysis of methylation status of Snrpn-DMR, percentage of fertilization, and blastocysts formation.

RESULT(S)

Methylation status of Snrpn-DMR from vitrified-warmed GV oocytes did not show significant alteration compared with that of controls, although a significant reduction of viable oocytes was observed. Puberty as well as endocrine function was restored, and no significant difference was shown in number of follicles, percentage of mice retaining fertility, and blastocyst formation among three groups.

CONCLUSION(S)

Our study proved that vitrification of prepubertal mouse ovaries did not alter the methylation profile of Snrpn-DMR and subsequent allotransplantation; IVF could restore the development and fertility potential.

Mouse ovarian follicle cryopreservation using vitrification or slow programmed cooling: assessment of in vitro development, maturation, ultra-structure and meiotic spindle organization

AIM

To compare different outcomes of vitrification and slow freezing of isolated pre-antral follicles and to evaluate different cryo-devices for vitrification of isolated follicles.

METHODS

Pre-antral follicles were isolated from mouse ovaries and cryopreserved using vitrification and slow freezing. A preliminary experiment was carried out to select the optimal cryo-device for vitrification of isolated follicles. A total of 414 follicles were randomly distributed among four groups: control (CT) fresh (n=100), nylon mesh (n=96), electron microscopy grid (n=102), and micro-capillary tips (n=116). Subsequently, a total of 979 follicles were randomly assigned to three different groups: CT fresh (n=256), vitrification (n=399) and slow freezing (n=324). CT and cryopreserved/thawed follicles were cultured in vitro and examined daily for development. Final maturation was triggered with human chorionic gonadotrophin and rates of oocyte maturation were calculated. The ultra-structure of cryopreserved/thawed follicles was studied using electron microscopy. Meiotic spindle presence and organization in mature oocytes were examined using the Oosight imaging system.

RESULTS

  Micro-capillary tips resulted in poor immediate post-warming survival but no differences were observed in the subsequent in vitro development characteristics between different cryo-devices. Nylon mesh proved to be the easiest carrier, particularly when large numbers of follicles were to be vitrified. Compared to vitrification, slow freezing resulted in a significantly lower number of intact follicles at the end of the culture period (P<0.0001). However all other outcome measures were comparable between both techniques.

CONCLUSIONS

Isolated follicles were more vulnerable to cryodamage after slow freezing as compared to vitrification.

Effects of vitrification solutions and equilibration times on the morphology of cynomolgus ovarian tissues

This study assessed the effects of vitrification solutions and equilibration times on morphology of cynomolgus ovarian tissues. Ovarian cortical sections (0.1-0.2 cm thickness) of seven cynomolgus monkeys were randomly allocated to either a control group or one of six vitrification groups. Ovarian tissue sections were vitrified ultra-rapidly by placing them directly into liquid nitrogen using two different vitrification solutions (VSEGP: 5.64 mol/l ethylene glycol+5% (w/v) polyvinylpyrrolidone+0.5 mol/l sucrose; and VSED: 3.22 mol/l ethylene glycol+2.56 mol/l dimethylsulphoxide+0.5 mol/l sucrose) after three different exposure times (5-20 min). After warming, follicle morphology was analysed using light and transmission electron microscopy. The proportion of morphologically normal follicles vitrified using VSED after a 5-min exposure was lower (P<0.05) than those vitrified by other conditions. The proportion of normally structured mitochondria in oocytes of preantral follicles vitrified after a 5-min exposure to VSED (56%) was lower (P<0.01) than those vitrified by other conditions (78-88%). Following tissue vitrification with VSED, the surface ratio of lysosome was increased compared with non-vitrified oocytes (1.64% versus 1.11%; P<0.05). These results indicate that VSEGP can support the morphology of vitrified preantral follicles and oocytes.

Successful in vitro culture of pre-antral follicles derived from vitrified murine ovarian tissue: oocyte maturation, fertilization, and live births

Cryopreservation of ovarian tissue is an important option for preserving the fertility of cancer patients undergoing chemotherapy and radiotherapy. In this study, we examined the viability and function of oocytes derived in vitro from pre-antral follicles as an alternative method for restoring fertility. Pre-antral follicles (specified as secondary follicle with a diameter around 100-130 μm) were mechanically isolated from vitrified-warmed and fresh adult mouse ovarian tissues and cultured for 12 days followed by an ovulation induction protocol at the end of this period to initiate oocyte maturation. Oocytes were then released from these follicles, fertilized in vitro, and cultured to the blastocyst stage and vitrified. After storage in liquid nitrogen for 2 weeks, groups of vitrified blastocysts were warmed and transferred into pseudo-pregnant recipient females. Although most of the isolated mouse pre-antral follicles from fresh (79.4%) and vitrified (75.0%) ovarian tissues survived the 12-day in vitro culture period, significantly fewer mature oocytes developed from vitrified-warmed pre-antral follicles than from the fresh controls (62.2 vs 86.4%, P<0.05). No difference was observed in embryo cleavage rates between these two groups, but the proportion of embryos that developed into blastocysts in the vitrification group was only half that of the controls (24.2 vs 47.2%, P<0.05). Nevertheless, live births of healthy normal pups were achieved after transfer of vitrified blastocysts derived from both experimental groups. This study shows that successful production of healthy offspring using an in vitro follicle culture system is feasible, and suggests that this procedure could be used in cancer patients who wish to preserve their fertility using ovarian tissue cryopreservation.

Comparisons of different protocols for vitrifying mouse ovarian tissue

The aim of this study was to detect the effects of different combinations of cryoprotectants with different equilibrium time on the mouse ovarian tissue during vitrification. Ovarian tissue of mice was vitrified-thawed. Mice (n = 80) were randomly assigned to treatment groups according to different vitrification solutions [I: 20% (v/v) ethylene glycol (EG) + 20% (v/v) Dimethylsulfoxde (DMSO), II: 20% (v/v) EG + 20% (v/v) PROH, III: 20% (v/v) PROH + 20% (v/v) DMSO] and different lengths of equilibrium time (a: 15 min, b: 30 min, c: 45 min). The serum levels of estradiol, the follicular density and the percentage of cells expressing Proliferating-cell nuclear antigen (PCNA) of grafts in Group IIb were the highest in all these treatment groups. In addition, the serum levels of estradiol, the follicular density and the percentage of cells expressing PCNA of grafts in Group Ib were significantly higher than those in Group Ia and Group Ic, while the serum levels of estradiol, the follicular density and the percentage of cells expressing PCNA of grafts in Group IIIb were significantly higher than those in Group IIIa and Group IIIc. In conclusion, vitrification solution [20% (v/v) EG + 20% (v/v) PROH] with equilibrium time of 30 min is optimal selection for vitrifying mouse ovarian tissue.

Sucrose affecting successful transplantation of vitrified-thawed mouse ovarian tissues

PURPOSE

The aim of this experiment is to detect effects of varying levels of sucrose on vitrified ovarian tissues.

METHODS

Ovarian tissues of mice were vitrified-thawed. Mice were randomly assigned to the fresh control group and experimental groups. According to different concentration of sucrose in vitrification solution, the experimental groups were randomly divided into Group I (0.2 M sucrose), Group II (0.4 M sucrose), Group III (0.8 M sucrose) and Group IV (1.6 M sucrose). Cytology was followed throughout the oophorectomy and transplantation period. Hormone levels and density of follicle were measured 1 month after transplantation.

RESULTS

The number of days before the resumption of estrous cycles in control group was significantly smaller than those in all of experimental groups. The serum estradiol levels of mice and the follicular density of ovarian grafts in control group were significantly higher than those in all of experimental groups. In addition, the number of days before the resumption of estrous cycles in Group II and Group III were smaller than those in Group I and Group IV. The serum estradiol levels of mice and the follicular density of ovarian grafts in Group II and Group III were significantly higher than those in Group I and Group IV. However, no difference was observed in the number of days before the resumption of estrous cycles and the serum estradiol levels between Group II and Group III. A similar follicular density was also observed in Group II and Group III.

CONCLUSION

Sucrose concentration of 0.4 M or 0.8 M in cryoprotective media is suitable for vitrifying mouse ovarian tissues.

Comparison of urinary and recombinant follicle-stimulating hormone in in vitro growth, maturation, and fertilization of mouse preantral follicles

OBJECTIVE

To compare the effects of urinary and recombinant follicle-stimulating hormone (FSH) on follicular development, oocyte maturation, and fertilization.

DESIGN

Prospective randomized animal study.

SETTING

University-based research laboratory.

ANIMAL(S)

Normal (C57BL/6xDBA2) F1 mice.

INTERVENTION(S)

Collection of preantral follicles by mechanical dissection, in vitro growth (IVG) with urinary or recombinant FSH (100 mIU/mL), in vitro maturation (IVM), and fertilization.

MAIN OUTCOME MEASURE(S)

During IVG, follicle diameter and antral formation were evaluated. The number of cells per follicle was evaluated at the end of IVG. The 17beta-estradiol measurements were performed from conditioned media. After IVM, mucification and oocyte maturation rates were estimated and mature oocytes were fertilized.

RESULT(S)

No differences were observed in the antral formation rate of either group. Antral follicles in the urinary FSH group, however, showed a higher diameter but a lower number of cells per follicle than those in the recombinant FSH group. The level of 17beta-estradiol was also higher in the recombinant FSH group. The rate of mature oocytes developing into metaphase I or II was statistically significantly higher in the recombinant FSH group than in the urinary FSH group.

CONCLUSION(S)

Recombinant FSH provided better conditions than urinary FSH for the growth and development of mouse preantral follicles that could produce mature oocytes with fertilization capacity.

In vitro growth and maturation of mouse oocyte-granulosa cell complex from cryopreserved ovaries and achievement of pup birth

Ovarian tissue banking is a feasible strategy for fertility preservation for young women after cancer treatments. Ovarian tissue, after thawing, is used for several options; orthotopic grafting (normal site), autologous heterotopic grafting and collection of ovarian follicles for culture. Recent reports of live birth encouraged clinicians and researchers to apply this technology to premature ovarian failure (POF) resulting from strong cancer therapy. Grafting, however, carries a risk of malignant cell recurrence. For safety, development of a culture method is necessary but optimum culturing conditions for less-developed follicles abundant in the ovary are not well known. In the present article, the current status of ovarian tissue cryopreservation, and in vitro oocyte growth and maturation from the preserved ovaries are reviewed.

Effect of vitrification method on survivability, follicular growth and ovulation of preantral follicles in mice

AIM

This study was designed to compare the survival rates, follicular growth rates, and ovulation rates of vitrified preantral follicles (PF) from ovaries with those isolated from a vitrified ovarian cortical strip.

METHODS

Mouse ovaries were divided into three groups: those not treated by vitrification of the PF (control), those treated by vitrification of the PF isolated from the ovaries (group I), and those treated by vitrification of ovarian tissue followed by PF isolation (group II). The group I samples were exposed to equilibration solution (EG-20) for 5.0 min plus vitrification solution (EFS-40) for 0.5 min, while the group II samples were exposed to EG-20 for 10.0 min plus EFS-40 for 2.0 min, before vitrification. They were subsequently placed on an electron microscope grid, and submerged immediately in liquid nitrogen. After thawing, the survival rate and the growth rate of the follicles were evaluated every 2 days.

RESULTS

In the in vitro condition, the follicles grew and developed into antral follicles in groups I and II. The survival rate of the group I samples was higher than that of the group II samples during the in vitro culture (P<0.05). The growth rates of the follicles in group I were higher than those in group II after day 6 (P<0.05). The ovulation rate of the samples in group I was higher than that of group II (P<0.05).

CONCLUSION

These results demonstrated that direct PF vitrification appeared to be better than vitrification of the PF isolated from ovarian tissue.

Cryopreservation of the mouse ovary inhibits the onset of primordial follicle development

The cryopreservation of ovarian tissue has been reported to affect the development of preantral follicles. However, the effect of cryopreservation of ovarian tissue on the development of primordial follicles remains to be elucidated. This study was conducted to evaluate the effect of cryopreservation on the development of frozen-thawed mouse primordial follicles. One-day-old mouse ovaries were cryopreserved by either slow-freezing or a vitrification method. The development of primordial follicles was evaluated histologically and also with markers for follicle development such as: GDF-9, inhibin-alpha subunit and ZP3 in fresh and frozen-thawed ovaries cultured for five days. The proportion of apoptotic and necrotic areas was analyzed in fresh and frozen-thawed ovaries at one and five days after culture, in order to examine the viability of ovarian cells that influence primordial follicle development. The development rate of primordial follicles was significantly lower in slow-frozen and vitrified ovaries than the fresh controls after five days of in vitro culture (P<0.05). The mRNA expression for all developmental markers was slightly decreased in the frozen-thawed ovaries; this difference was not significant. The proportion of apoptosis was significantly increased in the slow-frozen and vitrified ovaries compared to the fresh ovaries at one day (P<0.05); however, there was no difference at five days after culture. The proportion of the area of necrosis was significantly higher in slow-frozen and vitrified ovaries compared to the fresh ovaries at one and five days after culture (P<0.05). Our preliminary data suggest that ovarian tissue cryopreservation using slow-freezing and vitrification methods inhibits development of primordial follicles. This may be caused by the death of ovarian cells through apoptosis and necrosis after cryopreservation.

Pup birth from mouse oocytes in preantral follicles derived from vitrified and warmed ovaries followed by in vitro growth, in vitro maturation, and in vitro fertilization

OBJECTIVE

To determine an optimum condition for vitrification of various animal species and to examine the developing capacity into pups of mouse oocytes in preantral follicles originating from cryopreserved ovaries.

DESIGN

Experimental animal study.

SETTING

Laboratory environment.

ANIMAL(S)

Normal (C57BL/6 x DBA2) F1 mice.

INTERVENTION(S)

Vitrification of animal ovaries using polyester sheets as a storage device; collection of oocyte-granulosa cell complexes by enzymatic treatment; and in vitro growth (IVG), in vitro maturation (IVM), and IVF, with embryo transplantation to pseudopregnant mice.

MAIN OUTCOME MEASURE(S)

Histological analysis of vitrified and warmed ovaries from several animal species; measurement of successful rates in IVG, IVM, and IVF of mouse oocytes in oocyte-granulosa cell complexes collected from the vitrified and warmed ovaries; and achievement of pup birth.

RESULT(S)

The vitrification method used was effective for storage of various animal ovaries. The oocytes enclosed in preantral follicles that were yielded from the vitrified-warmed ovaries preserved the capacity for developing into pups after IVG, IVM, and IVF.

CONCLUSION(S)

The findings indicated that ovarian cryopreservation by vitrification and subsequent IVG, IVM, and IVF are promising methods for restoring young cancer patients' fertility. The practical information presented here is applicable to human ovarian tissues.

Correlation of somatic cell steroid secretion and quality of generated oocytes after in-vitro stimulation of mouse follicles

PURPOSE

To test the possibility of follicular somatic cell steroidogenesis as a marker for quality of their embraced oocytes.

METHODS

Mechanically isolated mouse preantral follicles were cultured and matured in-vitro (IVC/IVM) for study.

RESULTS

During IVC/IVM, oogenesis occurred concomitantly with folliculogenesis in a coordinated manner and simultaneously with progressive increments of somatic cell steroidogenesis. Follicular E(2) production of matured oocytes were significantly higher than that of immature ones. The majority of MII oocytes (32/36) and all developed blastocysts(12/12) were associated with active E(2) production prior to ovulation. In this study, 18 MII oocytes met both requirements for active and optimal E(2) production. 13 of them were fertilized and 10 developed into blastocysts.

CONCLUSION

Active somatic cell steroidogenesis prior to ovulation and an optimal steroid milieu at ovulation are prerequisites for generation of competent oocytes after follicular maturation in-vitro.