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

Comparison of angiogenic potential in vitrified vs. slow frozen human ovarian tissue

Vitrification of ovarian tissue is a promising alternative approach to the traditional slow freezing method. Few empirical investigations have been conducted to determine the angiogenic profiles of these two freezing methods. In this study we aimed to answer the question whether one of the cryopreservation methods should be preferred based on the secretion of angiogenic factors. Tissue culture with reduced oxygen (5%) was conducted for 48 h with samples of fresh, slow frozen/thawed and vitrified/rapid warmed ovarian cortex tissue from 20 patients. From each patient, tissue was used in all three treatment groups. Tissue culture supernatants were determined regarding cytokine expression profiles of angiogenin, angiopoietin-2, epidermal growth factor, basic fibroblast growth factor, heparin binding epidermal growth factor, hepatocyte growth factor, Leptin, Platelet-derived growth factor B, placental growth factor and vascular endothelial growth factor A via fluoroimmunoassay. Apoptotic changes were assessed by TUNEL staining of cryosections and supplemented by hematoxylin and eosin and proliferating cell nuclear antigen staining. Comparing the angiogenic expression profiles of vitrified/rapid warmed tissue with slow frozen/thawed tissue samples, no significant differences were observed. Detection of apoptotic DNA fragmentation via TUNEL indicated minor apoptotic profiles that were not significantly different comparing both cryopreservation methods. Vitrification of ovarian cortical tissue does not appear to impact negatively on the expression profile of angiogenic factors and may be regarded as an effective alternative approach to the traditional slow freezing method.

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.

Fibrin Scaffold Incorporating Platelet Lysate Enhance Follicle Survival and Angiogenesis in Cryopreserved Preantral Follicle Transplantation

Background:

Transplantation of cryopreserved follicles can be regarded as a promising strategy for preserving fertility in cancer patients under chemotherapy and radiotherapy by reducing the risk of cancer recurrence. The present study aimed to evaluate whether fibrin hydrogel supplemented with platelet lysate (PL) could be applied to enhance follicular survival, growth, and angiogenesis in cryopreserved preantral follicle grafts.

Materials and Methods:

Preantral follicles were extracted from 15 four-week-old NMRI mice, cryopreserved by cryotop method, and encapsulated in fibrin-platelet lysate for subsequent heterotopic (subcutaneous) auto-transplantation into the neck. Transplants were assessed in three groups including fresh follicles in fibrin-15%PL, cryopreserved follicles in fibrin-15%PL, and cryopreserved follicles in fibrin-0% PL. Two weeks after transplantation, histological, and immunohistochemistry (CD31) analysis were applied to evaluate follicle morphology, survival rate, and vascular formation, respectively.

Results:

Based on the results, fibrin-15% PL significantly increased neovascularization and survival rate (SR) both in cryopreserved (SR=66.96%) and fresh follicle (SR=90.8%) grafts, compared to PL-less fibrin cryopreserved transplants (SR=28.46%). The grafts supplemented with PL included a significantly higher percentage of preantral and antral follicles. Also, no significant difference was observed in the percentage of preantral follicles between cryopreserved and fresh grafts of fibrin-15% PL. However, a significantly lower (P=0.03) percentage of follicles (23.37%) increased to the antral stage in cryopreserved grafts of fibrin-15%PL, compared to fresh grafts (35.01%).

Conclusion:

The findings demonstrated that fibrin-PL matrix could be a promising strategy to improve cryopreserved follicle transplantation and preserve fertility in cancer patients at the risk of ovarian failure.

Ultrastructural Characterization of Porcine Growing and In Vitro Matured Oocytes

Simple Summary

During oocyte growth and maturation, the organelle’s morphology of porcine oocytes changed and populated different compartments depending on the differentiation status. Changes in ultrastructural or subcellular level of porcine oocytes during oogenesis/folliculogenesis were observed, potentially leading to future mitochondrion replacement therapies of oocytes.

Abstract

This study aimed to investigate ultrastructural changes of growing porcine oocytes and in vitro maturated oocytes. Light microscopy was used to characterize and localize the primordial, primary, secondary, and tertiary follicles. During oocyte growth and maturation, the morphology of mitochondria was roundish or ovoid in shape depending on the differentiation state, whereas their mean diameters oscillated between 0.5 and 0.7 µm, respectively, from primary and secondary follicles. Hooded mitochondria were found in the growing oocytes of the tertiary follicles. In addition to the pleomorphism of mitochondria, changes in the appearance of lipid droplets were also observed, along with the alignment of a single layer of cortical granules beneath the oolemma. In conclusion, our study is apparently the first report to portray morphological alterations of mitochondria that possess the hooded structure during the growth phase of porcine oocytes. The spatiotemporal and intrinsic changes during oogenesis/folliculogenesis are phenomena at the ultrastructural or subcellular level of porcine oocytes, highlighting an in-depth understanding of oocyte biology and impetus for future studies on practical mitochondrion replacement therapies for oocytes.

A closed vitrification system enables a murine ovarian follicle bank for high-throughput ovotoxicity screening, which identifies endocrine disrupting activity of microcystins

Increasing evidence reveals that a broad spectrum of environmental chemicals and pharmaceutical compounds cause female ovarian toxicity (ovotoxicity). The current gold standard of ovotoxicity testing largely relies on whole laboratory animals, but in vivo models are time consuming, costly, and present animal welfare concerns. We previously demonstrated that the 3D encapsulated in vitro follicle growth (eIVFG) is a robust in vitro model for ovotoxicity testing. However, the follicle preparation process is complex and highly dependent on technical skills. Here, we aimed to use vitrification method to cryopreserve murine immature follicles for a high-content eIVFG, chemical exposure, and ovotoxicity screening. Results indicated that a closed vitrification system combined with optimized vitrification protocols preserved mouse follicle viability and functionality and vitrified follicles exhibited comparable follicle and oocyte reproductive outcomes to freshly harvested follicles during eIVFG, including follicle survival and development, ovarian steroidogenesis, and oocyte maturation and ovulation. Moreover, vitrified follicles consistently responded to ovotoxic chemical, doxorubicin (DOX). We further used vitrified follicles to test the response of microcystins (MCs), an emerging category of environmental contaminants produced by cyanobacteria associated with harmful algal blooms (HABs), and found that different congeners of MCs exhibited differential ovotoxicities. In summary, our study demonstrates that vitrification enables a long-term-storage and ready-to-use ovarian follicle bank for high-throughput ovotoxicity screening, which identifies endocrine disrupting effects of MCs.

The harmful effect of removing the extracellular vitrification medium during embryo cryopreservation using a nylon mesh device in rabbit

During the last decades, many techniques have been developed to reduce sample volume and improve cooling and warming rates during embryo vitrification. The vast majority are based on the "minimum drop size" concept, in which the vitrification solution around embryos is reduced by aspiration, leaving a tiny part of volume surrounding embryos. However, novel cryodevices were aimed to remove the entire vitrification solution. This study was designed to compare the "minimum drop size" technique using Cryotop® with the nylon mesh as cryodevice on rabbit morula embryos. The outcomes assessed were the in vitro development rates (experiment 1) and the offspring rates at birth (experiment 2). Embryos were vitrified in a two-step procedure; equilibrium (10% EG + 10% Me2SO) for 2 min and vitrification (20% EG + 20% Me2SO) for 1 min. In experiment 1, embryos (n = 323) were warmed and subsequently in vitro cultured for 48 h to assess the embryo developmental capability to reach the hatching-hatched blastocyst stage. In experiment 2, embryos were transferred using the laparoscopic technique (n = 369) to assess the offspring rate at birth. In this context, rates of in vitro embryo development were similar between vitrified groups (0.73 ± 0.042% and 0.66 ± 0.047% for Cryotop® and nylon mesh device, respectively), but lower than in the fresh group (0.97 ± 0.016%, p < 0.05). In experiment 2, there were no significant differences in survival rates (offspring born/total embryos transferred) among the Cryotop® device group and fresh group (0.41 ± 0.049% and 0.49 ± 0.050%, respectively). But significantly lower value was obtained in the nylon mesh device group (0.18 ± 0.030%). These results indicate that nylon mesh is not suitable as cryodevice for rabbit morula vitrification, remaining those using the "minimum drop size" methodology as the best option.

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.

Establishment of an improved vitrification protocol by combinations of vitrification medium for isolated mouse ovarian follicles

In vitro follicle growth (IVFG) is an emerging alternative option for fertility preservation in women instead of ovarian tissue cryopreservation and transplantation. To widen the application of this technique, follicle cryopreservation should be established prior to clinical use. In the present study, we tried to determine the optimal vitrification protocol of mouse ovarian follicle for in vitro culture and oocyte maturation by comparing four different compositions of cryoprotective agents (CPA). Secondary follicles were mechanically isolated from 2-week-old BDF-1 mice and randomly assigned to fresh control and four different groups by the composition of CPAs (ES, EDS, EFS and EPS groups; E: ethylene glycol, D: dimethyl sulfoxide, S: sucrose, F: ficoll, P: 1,2-propanediol (PROH)). After vitrification and warming procedures, the follicles were cultured in vitro for 10 days and then treated with human chorionic gonadotropin and epidermal growth factor to induce oocyte maturation. Fourteen to 16 h later, oocyte maturation and quality were assessed. Follicle viability was evaluated by Calcein-AM/ethidium homodimer-1 staining immediately after warming, and their survival and diameters were measured during follicle culture periods. Antral cavity formation was observed at the end of the culture period (on the 10th day of culture). Following oocyte maturation, its maturational ability and meiotic spindle formation were assessed to evaluate their competence. There was no significant difference in viability after warming among the vitrification groups. From the 8th day of culture, the survival rate of ES and EDS were significantly higher than those of other vitrification groups (EPS and EFS). The follicle diameter was largest in the fresh-control group from the 6th day, while smallest in the EFS with statistical significance. On the 10th day of culture, the antral-cavity formation rate of EDS was comparable to that of the fresh control group. However, the oocyte maturation was significantly decreased in all four vitrification groups when compared with control group; especially, the EFS showed a more marked reduction in the oocyte maturation. There were no significant differences in meiotic spindle formation among all of those groups. Our results suggest that EDS combination for mouse follicle vitrification are the most effective vitrification protocols for mouse follicle and evaluated by an in vitro culture and oocyte maturation after warming.

Comparison of the Oocyte Quality Derived from Two-Dimensional Follicle Culture Methods and Developmental Competence of In Vitro Grown and Matured Oocytes

In vitro follicle growth (IVFG) is an emerging fertility preservation technique, which can obtain fertilizable oocytes from an in vitro culture system in female. This study aimed to compare efficiency of the most widely used two-dimensional follicle culture methods [with or without oil layer (O+ or O- group)]. Preantral follicles were isolated from mice and randomly assigned. Follicles were cultured for 10 days and cumulus-oocyte complexes harvested 16-18 hours after hCG treatment. Follicle and oocyte growth, hormones in spent medium, meiotic spindle localization, expression of reactive oxygen species (ROS), mitochondrial activity, and gene expression were evaluated. In follicle growth, survival, pseudoantral cavity formation, ovulation, and oocyte maturation were also significantly higher in O+ group than O- group. Hormone production was significantly higher in follicles cultured in O+ than O-. There were no significant differences in mRNA expression related to development. On the other hand, the level of ROS was increased while the mitochondrial activity of in vitro grown matured oocyte was less than in vivo matured oocytes. In conclusion, follicle culture with O+ group appears to be superior to the culture in O- group in terms of follicle growth, development, oocyte growth, maturation, and microorganelles in oocyte.

Effects of Supplementation of Human Endometriotic Fluids on In Vitro Mouse Preantral Follicle Culture

This study aimed to investigate the potential detrimental effect of human endometriotic fluids (EFs) on in vitro growth of mouse preantral follicles. Preantral follicles (isolated from ovaries of 7- to 8-week-old mice) were cultured in growth medium for 10 days and then in maturation medium for 2 days. During in vitro culture, EF supernatants (0%, 2.5%, 5%, and 10%) were supplemented. Meiotic spindle integrity of metaphase II (MII) oocytes was analyzed. Hormone (17β-estradiol and anti-Müllerian hormone [AMH]) levels in the final spent media were measured by enzyme-linked immunosorbent assay. The survival rates of follicles at day 10 were significantly lower in 3 EF-supplemented groups (56.1%, 30.6%, and 6.2%; 83.6% in the nonsupplemented group). The production of total oocytes per initiated follicle was also significantly lower in the 3 EF-supplemented groups (34.7%, 18.4%, and 4.1%; 68.1% in the nonsupplemented group). Proportions of the oocyte with normal spindles were significantly lower in the 3 EF-supplemented groups (10%, 0% and 0%; 52% in the nonsupplemented group). In the final spent media, the level of 17β-estradiol was significantly lower only in the 10% EF-supplemented group, and the level of AMH was significantly lower in all 3 EF-supplemented groups, when compared with the nonsupplemented group. During in vitro culture of mouse preantral follicles, the survival rate, oocyte acquisition, spindle integrity of MII oocytes, and AMH production were greatly affected by EF supplementation. These findings suggest a possibility of detrimental effects of endometriotic cysts on folliculogenesis in adjacent ovarian tissues.

Fertility preservation through gonadal cryopreservation

Fertility preservation is an area of immense interest in today's society. The most effective and established means of fertility preservation is cryopreservation of gametes (sperm and oocytes) and embryos. Gonadal cryopreservation is yet another means for fertility preservation, especially if the gonadal function is threatened by premature menopause, gonadotoxic cancer treatment, surgical castration, or diseases. It can also aid in the preservation of germplasm of animals that die before attaining sexual maturity. This is especially of significance for valuable, rare, and endangered animals whose population is affected by high neonatal/juvenile mortality because of diseases, poor management practices, or inbreeding depression. Establishing genome resource banks to conserve the genetic status of wild animals will provide a critical interface between ex-situ and in-situ conservation strategies. Cryopreservation of gonads effectively lengthens the genetic lifespan of individuals in a breeding program even after their death and contributes towards germplasm conservation of prized animals. Although the studies on domestic animals are quite promising, there are limitations for developing cryopreservation strategies in wild animals. In this review, we discuss different options for gonadal tissue cryopreservation with respect to humans and to laboratory, domestic, and wild animals. This review also covers recent developments in gonadal tissue cryopreservation and transplantation, providing a systematic view and the advances in the field with the possibility for its application in fertility preservation and for the conservation of germplasm in domestic and wild species.

Use of nonhuman primates for the development of bioengineered female reproductive organs

Nonhuman primates (NHPs) have been widely used in reproductive biology, neuroscience, and drug development since a number of primate species are phylogenetically close to humans. In this review, we summarize the use of NHPs for nonclinical application in the reproductive system disorders including the loss or failure of an organ or tissue. Causes of infertility include congenital aplasia and acquired disorders of the reproductive organs. In addition, anti-cancer treatments can deplete ovarian follicles, leading to premature ovarian failure, infertility and long-term health risks. Along with a limited supply of human reproductive organs, anatomic/physiologic similarities to humans support the need for NHP models (New-World monkeys such as the common marmoset and Old-World monkeys such as cynomolgus and rhesus monkeys) to promote the advances in female infertility studies. For maintaining and executing animal studies using NHP, special protocols including animal care, anesthetic protocol, surgical technique, and immunosuppressive protocol are necessary. With a growing interest in the potential therapies such as endometrial tissue engineering, and ovary/follicle cryopreservation and grafting in Korea, this review can be useful in selecting appropriate animal models and can bridge between nonclinical studies and clinical applications by providing detailed information on the use of NHPs in the field of reproductive organ disorders.

Development of sheep primordial follicles encapsulated in alginate or in ovarian tissue in fresh and vitrified samples

In vitro follicle growth is a promising strategy for female fertility preservation. This study was conducted to compare the development of ovine follicles either isolated or in the context of ovarian cortical pieces after short term (8 days) three-dimensional culture in fresh and vitrified samples. Four different experiments were conducted; I) culture of ovarian cortical pieces encapsulated in 0.5% and 1% alginate and without alginate encapsulation (CP-0.5%, CP-1% and CP, respectively), II) culture of isolated primordial and primary follicles encapsulated in 1% and 2% alginate (IF-1% and IF-2%, respectively), III) culture of fresh and vitrified-warmed cortical pieces (F-CP and Vit-CP, respectively), and IV) culture of fresh and vitrified-warmed encapsulated isolated follicles (F-IF and Vit-IF, respectively). The number of secondary follicles after culture was negatively influenced by encapsulation of ovarian cortical pieces (6.3 ± 3.3 and 10.6 ± 0.9 vs 21.5 ± 2.3 in CP-0.5% and CP-1% vs CP, respectively). The diameter of follicles in IF-2% was higher than IF-1% (54.06 ± 2 vs 41.9 ± 1.5) and no significant difference in follicular viability was observed between the two groups. The proportions of different follicular types and their viability after culture in vitrified-warmed cortical pieces were comparable with fresh ones. The viability of vitrified-warmed isolated follicles was lower than fresh counterparts. The growth rate of fresh follicles was higher than vitrified-warmed follicles after culture (47.9 ± 1 vs 44.6 ± 1). In conclusion, while encapsulation of ovarian cortical pieces decreased the follicles' development, it could better support the growth of isolated follicles. Moreover, the viability and growth rate of isolated-encapsulated follicles was decreased by vitrification.

Supplementation of culture media with vitamin E improves mouse antral follicle maturation and embryo development from vitrified ovarian tissue

AIM

The aim of this study was to evaluate the effects of preventive vitamin E (α-tocopherol) on antral follicle development and embryogenesis of oocytes obtained after vitrification of mouse ovarian tissue.

METHODS

Female Balb/c mice were killed by cervical dislocation after the injection of pregnant mare's serum gonadotrophin (10 IU) and their ovaries were randomly divided into three groups: control or non-vitrified (n = 10), vitrification 1 (5, 10% ethylene glycol + 5, 10% dimethylsulfoxide) (n = 15), and vitrification 2 (10, 15% ethylene glycol + 10, 15% dimethylsulfoxide) (n = 15) with ascending concentration of cryoprotectants. After toxicity tests and vitrification-warming, mechanically isolated antral follicles were cultured in α-minimum essential medium, which was supplemented with or without α-tocopherol (100 μM). The follicular maturation rates and embryo development were collected and assessed. Also, the viability, morphology and ultrastructure of derived antral follicles from vitrified ovaries were analyzed.

RESULTS

The morphology and ultrastructure of follicles were well preserved in the vitrified groups and α-tocopherol supplementation of culture media significantly increased the proportion of oocytes that reached metaphase II blastocyst rates compared to non-α-tocopherol supplemented media (P < 0.01).

CONCLUSION

Vitamin E improves in vitro maturation rates and blastocyst rates of oocytes that are isolated from vitrified ovarian tissue.

Total oxidative status of mouse vitrified pre-antral follicles with pre-treatment of alpha lipoic acid

Background: Cryopreservation of pre-antral follicles is a hopeful technique to preserve female fertility. The aim of the present study was to evaluate reactive oxygen species (ROS) and total antioxidant capacity (TAC) levels of mouse vitrified pre-antral follicles in the presence of alpha lipoic acid (ALA). Methods: Isolated pre-antral follicles (140–150 µm in diameter) were divided into vitrified–warmed and fresh groups. Each group was subjected to in vitro maturation with or without ALA for 12 days, followed by adding human chronic gonadotropin to induce ovulation. In vitro fertilization was performed to evaluate their developmental competence. In parallel, the amount of ROS and TAC were assessed after 0, 24, 48, 72, and 96 h of culture by 2',7'-dichlorofluorescin assay and ferric reducing/antioxidant power assay, respectively. Results: The respective rates of survival, antrum formation, and metaphase II oocytes were significantly higher in ALA-supplemented groups compared to the groups not treated with ALA. TAC and ROS levels were significantly decreased and increased, respectively during the culture period up to 96 h in the absence of ALA in both vitrified and non-vitrified samples. However, with pretreatment of ALA, TAC levels were increased significantly and remained constant up to 96 h in vitrified-warmed pre-antral follicles, while ROS levels completely returned to the level of starting point after 96 h of culture in the presence of ALA. Conclusion: Pretreatment of ALA positively influences development of pre-antral follicles in vitrified and non-vitrified samples through increasing follicular TAC level and decreasing ROS levels.

Vitrification of mouse preantral follicles versus slow freezing: Morphological and apoptosis evaluation

The aim of this study was evaluation of survivability, maturation rate and apoptotic gene expression of preantral follicles after vitrification and slow freezing technique. Normal mouse preantral follicles were randomly divided into three experimental groups. In the control group, follicles were cultured immediately; in the vitrification and slow freezing groups, follicles were cultured after vitrification-warming and slow freezing-thawing procedures. Follicular viability was assessed by using 0.4% trypan blue, and molecular evaluation of messenger RNA levels of apoptosis-related genes was performed by the semi-quantitative RT-PCR method after 3 h of culture. Oocyte maturation rates were also evaluated on day 14 of culture. Survival and maturation rate in the slow freezing group were significantly lower than those in control and vitrification groups (P ≤ 0.05). Although there was no difference in Survivin expression among the three experimental groups, Bcl-2 expression was significantly lower in the slow freezing group compared to the other groups (P ≤ 0.05). The expression of Bax, P53, Fas and Bax/Bcl-2 ratio in the slow freezing group was significantly higher than control and vitrification groups (P ≤ 0.05). Preantral follicle vitrification seems to be better than slow freezing as seen in the survival, maturation and expression rates of apoptotic gene variants.

Ovarian tissue vitrification is more efficient than slow freezing in protecting oocyte and granulosa cell DNA integrity

Ovarian tissue cryopreservation is the primary treatment modality currently available to women at risk of losing their ovarian function due to cytotoxic therapy. However, the impact of these techniques on the oocyte DNA integrity is not elucidated. Here we have investigated the effect of vitrification and conventional slow freezing of eight week old Swiss albino mouse ovarian tissues on the oocyte and granulosa cell DNA integrity using the comet assay. The intracellular levels of reactive oxygen species in oocytes was measured by 2',7'-dichlorodihydrofluorescein diacetate fluorescence. The cryopreservation of ovarian tissue by the slow freezing technique resulted in a significantly higher level of DNA fragmentation in oocytes in comparison to vitrification (p < 0.05) whereas DNA fragmentation in granulosa cells was significantly higher than the control (p < 0.01). Further, reactive oxygen species were significantly elevated in oocytes derived from slow freezing when compared to vitrification (p < 0.05). Therefore, we conclude that the ovarian tissue slow freeze-thawing makes the oocyte and granulosa cells more vulnerable to DNA damage whereas vitrification appears to be a safer method than slow freezing for ovarian tissue cryopreservation.

Does cryopreservation of ovarian tissue affect the distribution and function of germinal vesicle oocytes mitochondria?

The aim of this study was to evaluate mitochondrial alteration and ATP content of germinal vesicle (GV) oocytes isolated from fresh and vitrified ovaries. After superovulation, the ovaries from adult mice were collected and divided into control and vitrified groups. GV oocytes were isolated mechanically from each group. Half were cultured for 24 hours and their maturation was assessed. Metaphase II oocytes were collected and submitted to in vitro fertilization and their fertilization rates and development to the blastocyst stage were evaluated. In the remaining GV oocytes, ATP levels were quantified, and mitochondrial distribution, mitochondrial membrane potential, and intracellular free calcium were detected with rhodamine 123, JC-1 and Flou-4 AM staining, using laser-scanning confocal microscopy. Maturation and fertilization rates of GV oocytes and the developmental rates of subsequent embryos were significantly lower in vitrified samples (P < 0.05). The ATP content and Ca(2+) levels differed significantly in fresh and vitrified GV oocytes (P < 0.05). Most mitochondria were seen as large and homogenous aggregates (66.6%) in fresh GV oocytes compared to vitrified oocytes (50%). No significant differences in mitochondrial membrane potential were found between the groups. The lower maturation and fertilization rates of GV oocytes from vitrified ovaries may be due to changes in their mitochondrial function and distribution.

Three dimensional culture of fresh and vitrified mouse pre-antral follicles in a hyaluronan-based hydrogel: a preliminary investigation of a novel biomaterial for in vitro follicle maturation

BACKGROUND

Folliculogenesis within the ovary requires interaction between somatic cell components and the oocyte. Maintenance of 3-dimensional (3-D) architecture and granulosa-oocyte interaction may be critical for successful in vitro maturation of follicles. Testing of novel biomaterials for the 3-D culture of follicles may ultimately lead to a culture model that can support the longer in vitro culture intervals needed for in vitro maturation of human oocytes from ovarian tissue biopsies.

METHODS

A novel tyramine-based hyaluronan (HA) hydrogel was tested for its biocompatibility with ovarian follicles. The HA was prepared at concentrations from 2 to 5 mg/ml. HA hydrogel was also formulated and tested with matrix proteins (ECM). Enzymatically isolated pre-antral follicles from the ovaries of 10-12 day SJL pups were divided amongst control (CT) and HA treatments. The growth of both fresh and vitrified follicles was assessed after encapsulation in the hydrogel. The basal culture medium was MEM alpha supplemented with FSH, LH, ITS and 5% FBS. Maturation was triggered by addition of hCG and EGF after in vitro culture (IVC). Outcome parameters monitored were follicle morphology, survival after IVC, antrum formation, GVBD and MII formation. Differences between treatments were analyzed.

RESULTS

HA and ECM-HA encapsulated follicles looked healthy and maintained their 3-D architecture during IVC. In control cultures, the follicles flattened and granulosa:oocyte connections appeared fragile. Estradiol secretion per follicle was significantly higher by Day 12 in ECM-HA compared to HA or CT (4119, 703 and 1080 pg/ml, respectively). HA and ECM-HA cultured follicles had similar survival rates (62% and 54%, respectively), percent GV breakdown (96-97%), MII formation (47-48%) and oocyte diameters at the end of IVC. Control cultures differed significantly in percent GVBD (85%) and MII formation (67%) . Vitrified-warmed follicles encapsulated in HA had an oocyte maturation rate to MII of 54% as compared to 57% in non-embedded follicles.

CONCLUSIONS

Initial testing of this new and unique HA-based hydrogel was quite promising. The ease of follicle encapsulation in HA, its optical transparency and ability to be molded combined with its support of follicle growth, estradiol secretion and resumption of meiosis make this HA-hydrogel particularly attractive as model for 3-D ovarian follicle culture.

An unusual presentation of tumor lysis syndrome in a patient with advanced gastric adenocarcinoma: case report and literature review

Tumor lysis syndrome (TLS) is characterized by hyperuricemia, hyperkalemia, hyperphosphatemia, and secondary hypocalcemia in patients with a malignancy. When these laboratory abnormalities develop rapidly, clinical complications such as cardiac arrhythmias, acute renal failure, seizures, or death may occur. TLS is caused by rapid release of intracellular contents by dying tumor cells, a condition that is expected to be common in hematologic malignancies. However, TLS rarely occurs with solid tumors, and here we present the second chemotherapy-induced TLS in a patient with advanced gastric adenocarcinoma to be reported in the literature. We also provide information regarding the total cases of TLS in solid tumors reported from 1977 to present day. Our methodology involved identifying key articles from existing reviews of the literature and then using search terms from these citations in MEDLINE to find additional publications. We relied on a literature review published in 2003 by Baeksgaard et al., where they gathered all total 45 cases reported from 1977 to 2003. Then, we looked for new reported cases from 2004 to present day. All reports (case reports, brief reports, letters to editor, correspondence, reviews, journals, and short communications) identified through these searches were reviewed and included.

Nanoliter droplet vitrification for oocyte cryopreservation

AIM

Oocyte cryopreservation remains largely experimental, with live birth rates of only 2-4% per thawed oocyte. In this study, we present a nanoliter droplet technology for oocyte vitrification.

MATERIALS & METHODS

An ejector-based droplet vitrification system was designed to continuously cryopreserve oocytes in nanoliter droplets. Oocyte survival rates, morphologies and parthenogenetic development after each vitrification step were assessed in comparison with fresh oocytes.

RESULTS

Oocytes were retrieved after cryoprotectant agent loading/unloading, and nanoliter droplet encapsulation showed comparable survival rates to fresh oocytes after 24 h in culture. Also, oocytes recovered after vitrification/thawing showed similar morphologies to those of fresh oocytes. Additionally, the rate of oocyte parthenogenetic activation after nanoliter droplet encapsulation was comparable with that observed for fresh oocytes. This nanoliter droplet technology enables the vitrification of oocytes at higher cooling and warming rates using lower cryoprotectant agent levels (i.e., 1.4 M ethylene glycol, 1.1 M dimethyl sulfoxide and 1 M sucrose), thus making it a potential technology to improve oocyte cryopreservation outcomes.

A simple and efficient method for preparation of isolated ovarian follicles for transmission electron microscopy

OBJECTIVE

A simple method for preparation of isolated ovarian follicles for transmission electron microscopy (TEM) using transwell inserts is described.

MATERIALS AND METHODS

Pre-antral follicles were enzymatically isolated from mouse ovaries and cultured overnight on transwell insert polyester membranes. The following day, isolated ovarian follicles were processed for TEM by moving the transwell insert through successive wells containing the fixation and embedding reagents. After polymerization of the resin, the polyester membrane with the follicles embedded in the resin was disengaged from the transwell unit. The resin was sectioned. Semi-thin sections were stained with toluidine blue while ultra-thin sections were stained by uranyl acetate and examined by light microscopy and TEM, respectively.

RESULTS

Isolated ovarian follicles were easily processed in groups for TEM. Follicles were well embedded and there appeared to be no loss of tissue during processing. The ultra-structure of processed isolated ovarian follicles was well preserved with little evidence of processing artifacts.

CONCLUSIONS

In situ processing and preparation of isolated ovarian follicles by first allowing attachment on transwell insert membranes was shown to be a simple, rapid and effective method for TEM.