Follicle culture after ovarian cryostorage

Incorporation of phosphatase inhibitor in culture prompts growth initiation of isolated non-growing oocytes

In vitro folliculogenesis of primordial and early preantral follicles is necessary for increment of reproductive efficiency in domestic animals, humans and endangered species. Recent study in phosphatase and tensin homolog (Pten) -knockout mice has revealed that this phosphatase acts as an inhibitory factor in follicle activation of primordial pool with the resultant inhibition of oocyte growth. To test in vitro effect of a phosphatase inhibitor on growth initiation of isolated non-growing oocytes in neonatal ovaries, we applied a specific inhibitor (bpV (HOpic)) for PTEN in culturing system. Non-growing oocytes isolated from the ovaries of newborn BDF1 (C57BL/6 × DBA/2) pups were divided to four culture groups. Five days after culture, the oocytes in 14 μmol/l bpV only, 14 μmol/l bpV plus 100 ng/ml Kit Ligand (KL), and 100 ng/ml KL groups showed significantly (P<0.05) growth (19.3±0.55, 25.8±0.53 and 21.6±0.29 μm, respectively) compared with that of the control (no additive) (16.9±0.53 μm). In addition, western blotting in those groups showed enhanced expression of phosphorylated Akt. In conclusion, we clearly demonstrate that isolated non-growing oocytes develop in phosphatase inhibitor, especially to PTEN, incorporated culturing system, and show first as we know that oocytes with zona Pellucidae can be obtained in vitro from isolated non-growing oocytes.

In vitro development of secondary follicles from cryopreserved rhesus macaque ovarian tissue after slow-rate freeze or vitrification

BACKGROUND

Ovarian tissue cryopreservation is the only option for preserving fertility in prepubertal girls and cancer patients requiring immediate treatment. Following ovarian tissue cryopreservation, fertility can be restored after tissue transplant or in vitro follicle maturation.

METHODS

Macaque (n= 4) ovarian cortex was cryopreserved using slow-rate freezing (slow freezing) or vitrification. Tissues were fixed for histology or phosphohistone H3 (PPH3) analysis, cultured with bromodeoxyuridine (BrdU) or used for three-dimensional secondary follicle culture. Follicular diameter and steroid hormones were measured weekly.

RESULTS

Slow freezing induced frequent cryo-injuries while vitrification consistently maintained morphology of the stroma and secondary follicles. PPH3 was similar in fresh and vitrified, but sparse in slow-frozen tissues. BrdU uptake appeared diminished following both methods compared with that in fresh follicles. In vitro follicle survival and growth were greater in fresh than in cryopreserved follicles. Antrum formation appeared similar after vitrification compared with the fresh, but was reduced following slow freezing. Steroid production was delayed or diminished following both methods compared with fresh samples.

CONCLUSIONS

Secondary follicle morphology was improved after vitrification relative to slow freezing. Following vitrification, stroma was consistently more compact with intact cells typical to that of fresh tissue. BrdU uptake demonstrated follicle viability post-thaw/warming. For the first time, although not to the extent of fresh follicles, macaque follicles from cryopreserved tissue can survive, grow, form an antrum and produce steroid hormones, indicating some functional preservation. The combination of successful ovarian tissue cryopreservation with in vitro maturation of follicles will offer a major advancement to the field of fertility preservation.

Meiosis in a bottle: new approaches to overcome Mammalian meiocyte study limitations

The study of meiosis is limited because of the intrinsic nature of gametogenesis in mammals. One way to overcome these limitations would be the use of culture systems that would allow meiotic progression in vitro. There have been some attempts to culture mammalian meiocytes in recent years. In this review we will summarize all the efforts to-date in order to culture mammalian sperm and oocyte precursor cells.

Evaluation of the developmental competence and chromosomal compliment of mouse oocytes derived from in-vitro growth and maturation of preantral follicles

PURPOSE

To evaluate the developmental potential and aneuploidy rates of in-vitro versus in-vivo grown and matured mouse oocytes.

METHODS

Mice were superovulated to obtain in-vivo matured oocytes. Mouse preantral follicles were also mechanically isolated and cultured in-vitro. In-vitro fertilization (IVF) was performed and fertilization, cleavage, and morula/blastocyst formation rates were compared between groups. Cytogenetic analysis was used to compare oocyte aneuploidy rates and aneuploidy characteristics in the developing embryos.

RESULTS

In-vivo oocyte maturation resulted in higher IVF fertilization, cleavage, and morula/blastocyst formation rates versus in-vitro follicle culture (96.4% versus 78.5%, p<0.001; 95.3% versus 77.4%, p<0.001; 94.1% versus 76.9%, p<0.001). Total aneuploidy rates were higher in embryos derived from in-vitro matured oocytes versus those grown in-vivo (4.0% versus 1.3%, p<0.05).

CONCLUSIONS

Results indicate a reduced developmental competency of in-vitro matured oocytes. The data also highlight an increased susceptibility to meiotic errors in early stage follicles undergoing in vitro culture.

[State of the art on in vitro folliculogenesis in mouse]

Follicle culture systems have been developed so as to achieve in vitro fertilization of oocytes coming from immature follicles. The in vitro folliculogenesis methods would be especially useful in reproductive medicine to restore fertility in women having undergone ovarian cryopreservation. Several culture systems allowing in vitro growth of small follicles have been developed in mouse. These have proven to be successful by the birth of healthy offsprings. Some elements determine the outcome of culture: follicle isolations at a defined stage of development, follicular morphology preservation, and supplementation of growth factors or hormones. Development of follicle culture in the mouse model led to a better understanding of ovarian physiology, in particular the relation between endocrine and paracrine factors on follicle development. The in vitro techniques in mouse became a valuable tool for improving reproductive technics improvement, and for toxicology studies.

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.

Developmental competence of transported in-vitro matured macaque oocytes

This study examines in-vitro maturation (IVM) in a non-human primate model, Macaca fascicularis. The animals had hormonal injections and laparoscopic oocyte retrieval (OR)) at 12- and 24- h after human chorionic gonadotrophin (HCG). The immature oocytes were placed in tightly capped tubes containing pre-equilibrated IVM medium and transported for 5 h in a dry portable 37 degrees C incubator without CO2 supplement. Meiotic spindle was observed at 36-38- h post-HCG by polarized microscopy in 72 and 84.5% of mature oocytes collected at 12- and 24- h post-HCG oocyte retrieval intervals respectively. However, abnormal spindle formations were detected in some IVM oocytes by confocal microscopy. The IVM oocytes were also randomly selected for (i) intracytoplasmic injection with frozen-thawed epididymal M. fascicularis spermatozoa and (ii) nuclear transfer (NT) with fresh M. fascicularis cumulus cells. Embryonic development of sperm-injected embryos was not affected by the 12- and 24- h post-HCG oocyte retrieval intervals (22.5 versus 27.9% respectively). However, embryonic development of NT embryos was significantly affected by the 12- h post-HCG oocyte retrieval interval (4.5 versus 31.7% respectively; P < 0.01). In conclusion, IVM of monkey oocytes in a dry portable incubator for 5 h did not affect the maturation rate. However, the ability of primate oocytes to develop after somatic cell nuclear transfer was affected by oocyte retrieval time post-HCG.

The cryopreservation of ovarian tissue: uses and indications in veterinary medicine

Animal experiments have shown that cryopreservation of the ovarian cortex, containing primordial follicles, could be used to preserve gametes thereby restoring fertility in humans and animals. During the last 100 years, many hundreds of species have been lost, and a third of the breeding animals are threatened with extinction. To preserve genetic diversity, notably for the conservation of endangered species, it is essential to conserve female and male gametes. Today, biotechnologies such as artificial insemination and embryo transfer are used in breeding programs and are well developed. However, even using these advanced techniques, there are problems due to the limited number of individuals used as the source of gametes, so that the risk of inbreeding is high, even in large populations. To preserve genetic diversity, it is necessary to create gene banks of male and female gametes and embryos, using a very large number of individual donors. Cryopreservation of ovarian tissue could present a means for enlarging the gene pool. Cryopreserved ovarian tissue could be used in auto- or xenografts, or for in vitro maturation (IVM) of primordial follicles. In this review, we describe the processes for cryopreservation of ovarian tissue and the various possibilities for using it.

Follicle development in grafted mouse ovaries after cryopreservation and subcutaneous transplantation

OBJECTIVE

Our aim was to determine the impact of freezing, thawing, and subcutaneous transplantation on follicular development in grafted mouse ovaries.

STUDY DESIGN

The mice were divided into 3 groups: control (group 1), frozen-thawed grafting (group 2), and frozen-thawed grafting with human menopausal gonadotropin injection (group 3). After freezing and thawing, the ovaries were transplanted into the subcutaneous tissue. Two weeks after transplantation, grafted ovaries and blood samples were collected.

RESULTS

Ovaries from group 3 contained significantly more follicles (246 +/- 43 follicles) than group 2(P <.05). The pattern and intensity of Cx37 immunohistochemical staining was similar in all groups. Follicle-stimulating hormone concentrations were significantly decreased in group 2 after ovarian grafting.

CONCLUSION

In mice, gonadotropin treatment before subcutaneous grafting improved the survival of growing follicles. Subcutaneous ovarian transplantation may restore ovarian function and could obviate many of the problems that are related to ovarian banking for humans.

Effects of low O2 and ageing on spindles and chromosomes in mouse oocytes from pre-antral follicle culture

To assess their quality, spindles were analysed in mouse oocytes from pre-antral follicle culture. High or low oxygen tension was present during the last 16 or 20 h post human chorionic gonadotrophin (HCG)/epidermal growth factor (EGF) addition. Most oocytes from pre-antral follicle culture possessed typical anastral spindles with flat poles resembling those of ovulated, in-vivo-matured oocytes of sexually mature mice, while denuded oocytes in-vitro matured to metaphase II (MII) formed significantly longer, slender spindles with pointed, narrow poles. Spindles in oocytes from follicle culture were only slightly shorter and less compact at the equator as compared with those of oocytes matured in vivo. Chromosomes were well aligned at the equator in MII oocytes obtained from follicle culture with high oxygen. Maturation rate was significantly reduced by lowering oxygen tension to 5% O2. Prolonged culture and the presence of only 5% O2 dramatically increased the percentage of MII oocytes with unaligned chromosomes. These observations indicate that sufficient oxygen supply and time of retrieval after initiation of resumption of maturation by HCG as well as the microenvironment and cell-cell interactions between oocytes and their somatic compartment are critical in affecting the oocyte's capacity to mature to MII, to form a functional spindle, and to align chromosomes correctly.

Live offspring by in vitro fertilization of oocytes from cryopreserved primordial mouse follicles after sequential in vivo transplantation and in vitro maturation

The objectives of the present study were to achieve 1) oocyte maturation, 2) oocyte competence of fertilization, and 3) oocyte competence of embryogenesis with oocytes from primordial follicles obtained from cryopreserved newborn mouse ovaries by using a two-step method. In the first step, frozen-thawed newborn mouse ovaries were transplanted under the kidney capsule of recipients for the initiation of growth from the primordial follicle stage on. In the second step, growing preantral follicles in the ovarian grafts were recovered and cultured. The results demonstrated that primordial follicles were able to be recruited to preantral follicles during the period of transplantation, and preantral follicles could be mechanically isolated from ovarian grafts. Under the present in vitro culture conditions, 85.8% of the isolated follicles (n = 332) from ovarian grafts survived the 12-day in vitro culture process, 84.9% of the recovered oocytes (n = 285) were germinal vesicle breakdown (GVBD)-competent, and 76% of the oocytes that underwent GVBD (n = 242) developed to the metaphase II (MII) stage. In the in vitro fertilization experiments, 75.4% of 142 inseminated MII oocytes underwent fertilization and cleavage to the 2-cell stage. Subsequently, 79.7% of the 2-cell-stage embryos (n = 69) progressed to the late morula-early blastocyst stage. Transfer of late morula-early blastocyst embryos resulted in the production of live offspring. From our experiments, it may be concluded that in vivo maturation by grafting followed by in vitro maturation of frozen-thawed primordial follicles can restore fertility in mice. This model could be useful for a similar application in the human.