Assessment of vitrification outcome by xenotransplantation of ovarian cortex pieces in γ-irradiated mice: morphological and molecular analyses of apoptosis

Systematic review and meta-analysis on patented and non-patented vitrification processes to ovarian tissue reported between 2000 and 2021

Due to the great interest in ovarian cryopreservation and, consequently conservation and restoration of female fertility in the last decades, different vitrification procedures (vitrification devices or solutions) have been developed, patented, and used both for academic research purposes and for clinical use. Therefore, the present study aimed to provide a systematic review and meta-analysis of data obtained from the application of different patented and non-patented vitrification devices and solutions in different countries. For this purpose, relevant observational studies published between the years 2000 to 2021 were selected to verify the efficiency of ovarian vitrification processes on parameters such as morphology, viability, and apoptosis in preantral ovarian follicles after transplantation or in vitro culture. Our research revealed that, although several countries were considered in the study, the United States and Japan were the countries that registered the most processes, and 22 and 16 vitrification devices and solutions out of a total of 51, respectively were patented. Sixty-two non-patented processes were also considered in the study in all countries. We also observed that transplantation and in vitro ovarian culture were the techniques predominantly used to evaluate the efficiency of the devices and vitrification solutions, respectively. In conclusion, this review showed that patented or non-patented protocols available in the literature are able to successfully preserve preantral follicles present in ovarian tissue. Despite the satisfactory results reported so far, adjustments in ovarian vitrification protocols in order to minimize cryoinjuries to the follicles remain one of the goals of cryopreservation and preservation of the female reproductive function. We found that vitrification alters the morphology and viability, and offers risks leading in some cases to follicular apoptosis. However, adjustments to current protocols to develop an optimal procedure can minimize damage by not compromising follicular development after vitrification/warming.

Preserving Oocytes in Oncofertility†

The prodigious rise of cancer survival rates enables many cancer survivors to live long lives. Therefore, the side effects of cancer treatments as well as the long-term quality of life after cancer have become more relevant. Ovarian toxicity is a major off-target effect of anticancer agents for childhood and young adult female cancer patients. Both chemotherapy and irradiation have been demonstrated to damage the ovary and increase the risks of premature ovarian failure (POF), early menopause, ovarian endocrine disorders, and sub- or infertility. Oncofertility is an emerging and multidisciplinary research and medical field that focuses on providing cancer patients with fertility preservation options. Oocyte quality and quantity are one of the most important factors to determine women's fertility success; therefore, preserving oocytes is paramount for maintaining the ability of young female cancer patients' reproduction after their recovery. This review summarizes peer-reviewed literature on current oocyte preservation options in oncofertility. We describe in-depth oocyte and embryo cryopreservation, ovarian suppression, ovarian tissue cryopreservation, in vitro maturation, ovarian transposition, and adjuvant therapy. Further, we discuss current guidelines and practices of female fertility preservation that cover preserving oocytes.

Molecular Mechanism and Prevention Strategy of Chemotherapy- and Radiotherapy-Induced Ovarian Damage

Fertility preservation is an emerging discipline, which is of substantial clinical value in the care of young patients with cancer. Chemotherapy and radiation may induce ovarian damage in prepubertal girls and young women. Although many studies have explored the mechanisms implicated in ovarian toxicity during cancer treatment, its molecular pathophysiology is not fully understood. Chemotherapy may accelerate follicular apoptosis and follicle reservoir utilization and damage the ovarian stroma via multiple molecular reactions. Oxidative stress and the radiosensitivity of oocytes are the main causes of gonadal damage after radiation treatment. Fertility preservation options can be differentiated by patient age, desire for conception, treatment regimen, socioeconomic status, and treatment duration. This review will help highlight the importance of multidisciplinary oncofertility strategies for providing high-quality care to young female cancer patients.

Follicular development and the expression of BAX and vascular endothelial growth factor in transplanted ovaries in uni- and bilateral ovariectomized mice: An experimental study

Background

Several conflicting results have been reported on the survival and function of transplanted ovaries.

Objective

Evaluation of the follicular development and the expression of vascular endothelial growth factor (VEGF) and Bcl-2-associated X protein (BAX) in ovaries transplanted into uni- and bilaterally ovariectomized mice.

Materials and Methods

In this experimental study, 40 female NMRI mice (21-days-old, 12-15 gr) were ovariectomized uni- and bilaterally (n = 20/ group), while the 8-wk-old mice were considered as intact control group (n = 6). 5 weeks after transplantation at the proestrus stage, the morphology of recovered transplanted ovaries and the proportion of follicles were studied at different developmental stages. The apoptosis cell death by pro-apoptotic protein BAX and the expression of VEGF were evaluated using immunohistochemistry.

Results

In the bilaterally ovariectomized mice, among the 455 counted normal follicles, a lower rate of primordial and primary follicles and a higher rate of preantral and antral follicles were observed (p = 0.002). However, the percentages of preantral and antral follicles, and the corpus luteum were significantly lower in the intact control group (among the 508 counted normal follicles in this group) compared to other transplanted groups (p = 0.002). The number of BAX-positive cells in all groups was not significantly different. The VEGF expression was prominent in vessels of the corpus luteum, and also in the theca layer of large follicles of studied groups.

Conclusion

Early discharge of ovarian reserve was prominent in the bilaterally ovariectomized group but the incidence of apoptotic cells and VEGF expression as angiogenic factor did not differ in both ovariectomized mice. Thus, unilaterally ovariectomy has less side effects on the ovarian reserve compared to bilateral ovariectomy.

The protective effects of rapamycin pretreatment on ovarian damage during ovarian tissue cryopreservation and transplantation

Ovarian tissue cryopreservation and transplantation (OCT) has been sufficiently proven effective and feasible to preserve fertility for women especially for prepubertal girls suffering from cancer with radiotherapy and chemotherapy. However, grafts' survival, significant follicle loss and a delay of revascularization during OCT still need to be resolved no matter what kind of cryopreserved method being used. Different from previous reports about additives treatment on recipient after ovarian transplantation, we here report a new vitrification protocol with pretreatment of rapamycin, an inhibitor of the mTOR signaling pathway. The rapamycin treatment has been shown to inhibit the activation of mTOR signaling pathway in fresh thawed ovaries or in ovaries shortly grafted in the recipient mice. Further study revealed increased percentage of primordial follicles and reduced apoptosis after 5 days of transplantation. Long-term follow up of ovarian development demonstrated the increase of ovarian survival rates in rapamycin treated ovaries after 2 weeks of transplantation. Although follicular development showed a slight delay with more secondary and early antral follicles found in rapamycin treated ovaries, follicular development was not blocked as manifested by the ovarian morphology after 5 weeks of transplantation. Taken together, the pretreatment of rapamycin before vitrification is a good method for clinical application with its effectiveness on preserving follicle reserve and promoting ovarian survival during the process of OCT.

Review of non-permeating cryoprotectants as supplements for vitrification of mammalian tissues

Vitrification of mammalian tissues is important in the areas of human assisted reproduction, animal reproduction, and regenerative medicine. Non-permeating cryoprotectants (CPAs), particularly sucrose, are increasingly used in conjunction with permeating CPAs for vitrification of mammalian tissues. Combining non-permeating and permeating CPAs was found to further improve post-thaw viability and functionalities of vitrified mammalian tissues, showing the potential applications of such tissues in various clinical and veterinary settings. With the rising demand for the use of non-permeating CPAs in vitrification of mammalian tissues, there is a strong need for a timely and comprehensive review on the supplemental effects of non-permeating CPAs toward vitrification outcomes of mammalian tissues. In this review, we first discuss the roles of non-permeating CPAs including sugars and high molecular weight polymers in vitrification. We then summarize the supplemental effects of non-permeating CPAs on viability and functionalities of mammalian embryos, and ovarian, testicular, articular cartilage, tracheal, and kidney tissues following vitrification. Lastly, challenges associated with the use of non-permeating CPAs in vitrification of mammalian tissues are briefly discussed.

Assessment of DNA Repair Gene Expressions in Vitrified Mouse Preantral Follicles

Objective

Vitrification of the ovarian tissue is one of the techniques recommended for preserving the fertility of women who are dealing with infertility. Despite its benefits, our information about the molecular aspects of ovarian follicles vitrification is somehow ambiguous. Therefore, the aim of this study was to evaluate the expression pattern of DNA repair genes in vitrified preantral follicles.

Materials and Methods

In this experimental study, the isolated preantral follicles (n=906) from 14-16 days old mice (n=12) were divided into three groups: fresh, toxic and vitrified which were cultured in vitro for 12 days. Preantral follicles were vitrified using cryotop followed by exposure to equilibration solution for five minutes and vitrification solution (VS) for 30 seconds. In the toxic group, preantral follicles were only placed in equilibration and vitrification media and they were then placed in the warming solutions without exposure to liquid nitrogen. On the second and sixth days of the culture period, real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was carried out to evaluate expression of the selected genes involved in DNA repair, including Msh6 (MutS homolog 6), Mre11 (Meiotic recombination 11), Brca1 (Breast cancer type 1), Rad51 (RAD51 recombinase), Pcna (Proliferating cell nuclear antigen) and Atm (ATM serine/threonine kinase). In addition, developmental parameters including growth, survival rate, antrum cavity formation and ovulation were analyzed.

Results

The relative mRNA expression of Msh6, Mre11, Brca1, Rad51, Pcna and Atm on the second and sixth days of the culture period in vitrified group was significantly higher than those of the control and toxic groups, but there was no significant difference between the toxic and control groups. In addition, developmental parameters of follicles were similar in both toxic and control groups, while both were significantly higher than that of vitrified group.

Conclusion

Vitrification changes the expression pattern of DNA repair genes of the mouse preantral follicles.

Folliculogenesis-Associated Genes Expression in Human Vitrified Ovarian Tissue after Xenotransplantation in γ-Irradiated Mice

Objective

Autograft transplantation of vitrified cortical ovarian tissue is an acceptable clinical technique for fertility preservation in women. Xenograft transplantation into animal models could be useful for evaluating the safety of human vitrified ovarian tissue. This study targeted to evaluate impact of vitrification on expression of the genes associated with folliculogenesis after xenograft transplantation of human vitrified ovarian tissue to γ-irradiated mice.

Materials and Methods

In this experimental study, ovarian biopsies were gathered from six transsexual persons. The cortical section of ovarian biopsies was separated and chopped into small pieces. These pieces were randomly divided into vitrified and non-vitrified groups. In each group some pieces were considered as non-transplanted tissues and the others were transplanted to γ-irradiated female National Medical Research Institute (NMRI) mice. Before and after two weeks of xenograft transplantation, histological assessment and evaluation of the expression of folliculogenesis- associated genes (FIGLA, GDF-9, KL and FSHR) were performed in both vitrified and non-vitrified groups.

Results

Percentage of the normal follicles and expression of the all examined genes from transplanted and non- transplanted tissue were similar in both vitrified and non-vitrified groups (P>0.05). After transplantation, the normal follicle rate was significantly decreased and among the folliculogenesis-associated genes, expression of GDF-9 gene was significantly increased, rather than before transplantation in vitrified and non-vitrified tissues (P<0.05).

Conclusion

The vitrification method using dimethyl solphoxide and ethylene glycol (EG) had no remarkable effect on the normal follicular rate and expression of folliculogenesis-associated genes after two weeks human ovarian tissue xenografting. In addition, transplantation process can cause a significant decrease in normal follicular rate and expression of GDF-9 gene.

Supplementation of Culture Media with Lysophosphatidic Acid Improves The Follicular Development of Human Ovarian Tissue after Xenotransplantaion into The Back Muscle of γ-Irradiated Mice

Objective

The aim of the present study was to evaluate the effects of lysophosphatidic acid (LPA) supplementation of human ovarian tissue culture media on tissue survival, follicular development and expression of apoptotic genes following xenotransplantation.

Materials and Methods

In this experimental study, human ovarian tissue was collected from eight normal female to male transsexual individuals and cut into small fragments. These fragments were vitrified-warmed and cultured for 24 hours in the presence or absence of LPA, then xenografted into back muscles of γ-irradiated mice. Two weeks post-transplantation the morphology of the recovered tissues were evaluated by hematoxylin and eosin staining. The expression of genes related to apoptosis (BAX and BCL2) were analyzed by real time revers transcription polymerase chain reaction (RT-PCR) and detection of BAX protein was done by immunohistochemical staining.

Results

The percent of normal and growing follicles were significantly increased in both grafted groups in comparison to the non-grafted groups, however, these rates were higher in the LPA-treated group than the non-treated group (P<0.05). There was a higher expression of the anti-apoptotic gene, BCL2, but a lower expression of the pro-apoptotic gene, BAX, and a significant lower BAX/ BCL2 ratio in the LPA-treated group in comparison with non-treated control group (P<0.05). No immunostaining positive cells for BAX were observed in the follicles and oocytes in both transplanted ovarian groups.

Conclusion

Supplementation of human ovarian tissue culture medium with LPA improves follicular survival and development by promoting an anti-apoptotic balance in transcription of BCL2 and BAX genes.

Vitrification of collared peccary ovarian tissue using open or closed systems and different intracellular cryoprotectants

This study aimed to evaluate different vitrification methods using distinct cryoprotectants (CPAs) for the preservation of collared peccary ovarian preantral follicles (PFs). Ovarian pairs from six females were fragmented and three fragments (fresh control group) were immediately evaluated for morphology, viability, cell proliferation capacity (assessed by quantifying the number of argyrophilic nucleolus organizer regions - NORs), and apoptosis (by the identification of activated caspase-3 expression). The remaining 18 fragments were vitrified using the solid surface vitrification (SSV) method or the ovarian tissue cryosystem (OTC) with 3 M ethylene glycol (EG), 3 M dimethylsulfoxide (DMSO), or a combination of the two (1.5 M EG/1.5 M DMSO). After two weeks, samples were rewarmed and evaluated as described previously. The OTC with any of the CPAs provided a similar conservation of morphologically normal PFs as the fresh control group (75.6 ± 8.6%); however, the SSV was only efficient with DMSO alone (63.9 ± 7.6%). Regarding the viability or cell proliferation, all tested groups provided post rewarming values similar to those observed for the fresh control group, 84.0 ± 2.9% viable cells with 2.0 ± 0.2 NORs. Related to apoptosis analysis, only the OTC with EG (46.7%) and the SSV method with EG (43.4%) or the combination of EG and DMSO (33.4%) provided similar values to those found for the fresh control group (36.7%). Our findings indicate the utilization of a closed system, the OTC, with 3 M EG as the CPA for the vitrification of collared peccary ovarian tissue.

Negative air pressure treatment accelerates the penetration of permeable cryoprotectants into bovine ovarian tissue in vitrification protocol and improves cell density after vitrification

Effects of additional physical treatments during vitrification of the bovine ovarian tissue were examined for increasing of permeability of ethylene glycol (EG) and dimethyl sulfoxide (Me2SO). The concentrations of EG and Me2SO and histological changes in the ovarian tissue were evaluated. In the first equilibration step (7.5% EG and 7.5% Me2SO), all the 10-min physical treatments, i.e., negative (679 hPa) or positive (1347 hPa) air pressure applied with a disposable syringe, and shaking (60 rpm) applied with a laboratory shaker, were comparable to 25-min non-physical treatment (plain) vitrification. When effects of the negative air pressure were examined in the second equilibration step (20% EG and 20% Me2SO), its 10-min treatment was equivalent to 15-min plain vitrification (140-170 mg/g tissue). It was thus indicated that the negative air pressure treatment accelerates the penetration of permeable cryoprotectants into the ovarian tissue slices. Histological examination showed that the cell density and the amount of pan-cadherin in the tunica albuginea of the ovary was reduced by the vitrification, but was improved by the negative air pressure treatment. The amount of pan-cadherin in the tunica albuginea was recommended as a biomarker for evaluation of effectiveness of protocol for cryopreservation of bovine ovarian tissue and considered to be a candidate biomarker for human ovarian tissue cryopreservation.

Selection of stable expressed reference genes in native and vitrified/thawed human ovarian tissue for analysis by qRT-PCR and Western blot

PURPOSE

To select reference genes with stable messenger RNA (mRNA) expression for quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) analysis of vitrified/thawed human ovarian tissue and to evaluate in human ovarian tissue the levels of key proteins which are commonly used as reference proteins.

METHODS

Pieces of ovarian tissue were obtained during laparoscopy from patients (n = 10, 24-36 years old) who suffered from types of cancer that does not affect reproductive system. Tissue strips from the intact group were immediately placed into liquid nitrogen. Tissue strips from the second group were successively placed into solutions with cryoprotective agents. Then, these strips were rapidly placed into liquid nitrogen. After thawing, ovarian tissue strips were cultured during 2 h in complete growth medium. Gene expression levels were measured using quantitative RT-PCR. Also, protein levels of three key reference genes were measured using Western blot. Statistical analysis of obtained data was performed by BestKeeper, NormFinder, and geNorm software utilities; correlation coefficients were also calculated.

RESULTS

The most suitable reference genes for qRT-PCR analysis of human cortical ovarian tissue after cryopreservation by vitrification are genes of ribosomal proteins RPL4, RPLP0, RPS18, and heat shock protein HSP90AB1. The protein levels of three commonly used reference genes (ACTB, GAPDH, and HSP90) were measured in two groups of samples of human ovarian tissue: intact and vitrified/thawed. The levels of ACTB, GAPDH, and HSP90 proteins were similar in native and vitrified/thawed samples.

CONCLUSION

Selection of suitable reference genes is the first aim of any research dedicated to the investigation of gene expression, because the interpretation of obtained results largely depends on selection of appropriate reference genes. Nowadays, there are many mathematical approaches allowing to select not only single reference gene but also a group of the most stably expressed reference genes. The use of mathematical models which take into account multiple reference genes will allow to obtain more accurate data on the expression of target genes.

Total saponins of Albiziae Cortex show anti-hepatoma carcinoma effects by inducing S phase arrest and mitochondrial apoptosis pathway activation

ETHNOPHARMACOLOGICAL RELEVANCE

Albiziae Cortex (AC) is a widely used traditional medicine in China. It is possess various properties to treat insomnia, traumatic injuries, diuresis, sthenia, and confusion. Total saponins of Albiziae Cortex (TSAC) are the most abundant bioactive components of AC, which were reported to show significant anti-tumor effects in vivo and in vitro. But the underlying mechanism of TSAC remained to be revealed.

AIM OF STUDY

In this study, we investigated the anti-hepatoma carcinoma effects and the potential mechanism of TSAC in vivo and in vitro.

MATERIALS AND METHODS

We first purified TSAC from crude extracts and characterized the major bioactive compounds by high performance liquid chromatography (HPLC). Effects of TSAC on viability of various hepatoma carcinoma cell lines were measured by MTT. Inhibition on cell proliferation was analysed using colony formation assay. Cell cycle distribution was revealed by flow cytometry. The apoptotic cells were observed by Hoechst 33258 staining and acridine orange (AO)/ethidium bromide (EB) double staining. Microstructures of apoptotic cells were examined by Transmission electron microscopy (TEM). The mitochondrial membrane potential were determined by JC-1 staining. Western blot was used to investigate the effects of TSAC on apoptosis-related proteins, B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax), and S-phase related protein cyclin A, cyclin E and cyclin-dependent kinases 2 (CDK2). Effects on tumor growth was assessed by H22-bearing ICR mice.

RESULTS

TSAC significantly decreased the hepatoma carcinoma cell viability and inhibited HepG2 cell colony formation in a concentration-dependent manner. We also found that TSAC inhibited HepG2 cell growth via induction of S phase arrest. Further study showed that TSAC significantly down-regulated the expressions of cyclin A, cyclin E and CDK2 in HepG2 cells. Meanwhile, TSAC could effectively induce mitochondria-dependent caspase apoptosis pathway activation. Furthermore, TSAC increased the expression of pro-apoptotic protein Bax and decreased the expression of anti-apoptotic protein Bcl-2. In vivo assay showed that the anti-tumor effects of TSAC were significantly augmented without increasing toxicity in H22-bearing ICR mice.

CONCLUSION

TSAC could inhibit cell proliferation through inducing S phase arrest and activate cell apoptosis via mitochondria-dependent apoptosis pathway. Therefore, TSAC could be a promising agent in clinical trials for anti-hepatoma carcinoma treatment.

Morphological and Molecular Aspects of In Vitro Culture of Preantral Follicles Derived from Vitrified Ovarian

Objective

This study aimed to evaluate the expression of the genes related to folliculo-genesis after vitrification of mouse ovarian tissues using a two-step in vitro culture.

Materials and Methods

In this experimental study, vitrified and non-vitrified ovaries from 7- day old (neonate) female mice were cultured using alpha-Minimum Essential Medium (α-MEM) supplemented with 5% fetal bovine serum (FBS) for 7 days. Morphology, surface area of ovaries and percentage of normal follicles were evaluated and compared in both groups. After one-week culture, in non-vitrified group, preantral follicles of cultured ovaries were isolated and cultured in a three-dimensional alginate culture system for 12 days. Then, the collected metaphase (M) II oocytes were inseminated with capacitated spermatozoa derived from 7-8-week old (adult) male NMRI mice. Follicular diameter, oocyte maturation, fertilization, embryo development and the expression of genes related to follicular development (Pcna, Fshr and Cyp17a1,) using real time reverse transcription-polymerase chain reaction (RT-PCR) were assessed at the end of last culture period in both groups.

Results

The ovarian area in vitrified group (162468.20 703.78) was less than non-vitrified group (297211.40 6671.71), while the percentage of preantral follicles in vitrified group (18.40%) was significantly lower than those of non-vitrified group (24.50%) on day 7 of culture (P<0.05). There were no significant differences between the two groups in terms of follicular diameter, expression of genes related to development of follicles, oocyte maturation, fertilization, as well as embryo development (P>0.05).

Conclusion

The results of this study showed that vitrification of ovarian tissue following in vitro culture had negative impact on the survival and development of follicles within the tissue. However, no significant alterations were observed in development, gene expression and hormonal production of in vitro culture of isolated follicles derived from vitrified ovarian tissues as compared to the non-vitrified samples.

Expectations and limitations of ovarian tissue transplantation

Constant progress in the diagnosis and treatment of cancer disease has increased the number and prognosis of cancer survivors. However, the toxic effects of chemotherapy and radiotherapy on ovarian function have resulted in premature ovarian failure. Patients are, therefore, still expecting methods to be developed to preserve their fertility successfully. Several potential options are available to preserve fertility in patients who face premature ovarian failure, including immature or mature oocyte and embryo cryopreservation. However, for children or prepubertal women needing immediate chemotherapy, cryopreservation of ovarian tissue is the only alternative. The ultimate aim of this strategy is to implant ovarian tissue into the pelvic cavity (orthotopic site) or in a heterotopic site once oncological treatment is completed and the patient is disease free. Transplantation of ovarian tissue with sufficiently large numbers of follicles could potentially restore endocrine function and allow multiple cycles for conception. However, the success of ovarian tissue transplantation still has multiple challenges, such as the low number of follicles in the graft that may affect their longevity as well as the survival of the tissue during ex vivo processing and subsequent transplantation. Therefore, this review aims to summarize the achievements of ovary grafting and the potential techniques that have been developed to improve ovarian graft survival.

Sheep Isolated Secondary Follicles Are Able to Produce Metaphase II Oocytes After Vitrification and Long-Term In Vitro Growth

The vitrification of preantral follicles followed by in vitro growth (IVG) could be valuable to produce fertilizable oocytes. However, the meiotic resumption rates of oocytes cultured from vitrified secondary follicles (SF) have been reported as suboptimal. This study aimed to verify two base media (alpha modification of minimum essential medium, α-MEM, and tissue culture medium 199, TCM199) on vitrified SF regarding different requirements during IVG. Sheep ovarian fragments were divided in six groups: (1) Fresh groups (Control α-MEM and TCM199): SF without vitrification; (2) Follicle-Vitrified (Follicle-Vit α-MEM and TCM199): SF vitrified after isolation; and (3) Tissue-Vitrified (Tissue-Vit α-MEM and TCM199): SF vitrified enclosed in ovarian fragments and, subsequently, isolated. The isolated SF were submitted to IVG for 18 days. Thereafter, the recovered cumulus-oocyte complexes (COCs) underwent in vitro maturation (IVM) and evaluation of chromatin configuration. Follicular granulosa cells were analyzed for their gene expression of Bax, Bcl2, and Connexins (CX) 37 and 43. COCs from in vivo antral follicles were used as in vivo control. Data were analyzed by analysis of variance, Tukey, and chi-square tests. Differences were considered significant if p-value is <0.05. Follicle-Vit groups had higher (p < 0.05) percentage of antrum formation compared with Tissue-Vit groups. Vitrification did not affect (p > 0.05) oocyte diameter postmaturation. Oocytes from Follicle-Vit in α-MEM reached metaphase II stage after IVM. Gene expression for CX37, CX43, and Bax was lower in Tissue-Vit groups. For Bcl2, the gene expression was the opposite. In conclusion, during IVG for 18 days, maximal oocyte meiotic resumption was not negatively impacted by vitrification and was greatest for isolated SF using α-MEM as a medium.

Effects of Angiopoietin-2 on Transplanted Mouse Ovarian Tissue

Transplantation of ovarian tissue (OT) is currently the only clinical option to restore fertility with cryopreserved OT. However, follicle loss caused by ischemia and slow revascularization occurs in transplanted OT. To shorten the ischemic period and promote angiogenesis, some angiogenic factors have been used. Angiopoietin-2 (Ang2) is one of the major angiogenic factors and has been reported to promote blood vessels and increase vascular permeability in ischemic and/or hypoxic environment. This study was performed to investigate the effects of Ang2 on follicle integrity and revascularization of transplanted mouse OT. Five-week-old B6D2F1 female mice were divided into a control group and two Ang2 groups, followed by ovary collection and vitrification. After warming, the ovaries were autotransplanted into kidney capsules with/without Ang2 injection (50 or 500 ng/kg), and then the mice were sacrificed at days 2, 7, 21, and 42 after transplantation. A total 2,437 follicles in OT grafts were assessed for follicular density, integrity, and classification by using hematoxylin and eosin staining. Apoptosis and revascularization were evaluated by using TUNEL assay and CD31 immunohistochemistry, respectively. Serum follicle-stimulating hormone (FSH) levels were measured by using enzyme-linked immunosorbent assay. Both Ang2 groups showed remarkable increase in morphologically intact follicle ratio across all grafting durations except D21. The numbers of CD31(+) vessels were significantly increased in both Ang2 groups compared with the control group at all durations, except in the 50 ng Ang2 group at D42. However, the mean numbers of follicles of the grafts, apoptosis ratios, and serum FSH levels showed no significant differences among the groups. Our results show that Ang2 treatment significantly increased the intact follicle ratios and the number of blood vessels of the mouse OT grafts. However, further studies performed with large animal or human OT are necessary before clinical application for fertility preservation in cancer patients, and the reliability of the systemic effects of Ang2 should be verified.

The preservation of vital functions in cat ovarian tissues during vitrification depends more on the temperature of the cryoprotectant exposure than on the sucrose supplementation

The objective of this study was to better characterize the impact of cryoprotectant exposure (temperature and sucrose supplementation) on the health and function of preantral follicles in ovarian tissues during vitrification using the domestic cat model. Ovarian cortical pieces from peri-pubertal individuals were exposed to cryoprotectants at 4 °C or room temperature and supplemented with 0 or 0.5 M of sucrose, followed by vitrification. After rapid warming, cortical pieces were cultured in vitro and assessed for normal follicular morphology, viability and resumption of transcriptional activities for up to 7 days. Throughout the culture period, follicular morphology (up to 67.5% normal follicles) and global RNA transcription (up to 50.9% follicles with transcriptional activity) in warmed tissues were improved by cryoprotectant exposure at 4 °C compared to room temperature, but viability (up to 84.6% viable follicles) did not seem to be affected by exposure temperature. Sucrose supplementation did not have a consistent effect as it increased RNA transcription but decreased normal follicular morphology. For the first time, the study demonstrated that the preservation of critical tissue functions, such as the transcriptional activities, highly depends on the temperature of the cryoprotectant exposure and not necessarily on the presence of sucrose.

Ovarian injury during cryopreservation and transplantation in mice: a comparative study between cryoinjury and ischemic injury

STUDY QUESTION

What is the main cause of ovarian injury during cryopreservation and transplantation in mice: cryoinjury or ischemic injury?

SUMMARY ANSWER

Post-transplantation ischemia is the main cause of ovarian injury during cryopreservation and transplantation for restoring ovarian function.

WHAT IS KNOWN ALREADY

During cryopreservation and the transplantation of ovaries, cryoinjury and ischemic injury inevitably occur, which has a detrimental effect on ovarian quality and reserve.

STUDY DESIGN, SIZE, DURATION

A total of 80 B6D2F1 female mice were randomly allocated to 2 control and 6 experimental groups according to the presence or the absence of transplantation (n = 10/group). The control groups consisted of fresh or vitrified-warmed controls that had the whole ovary fixed without transplantation (fresh and vitri-con, respectively). The experimental groups were further divided according to the presence of vitrification (fresh or vitrified-warmed) and the transplantation period (2 [D2], 7 [D7] or 21 [D21] days).

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the control groups, fresh and vitrified-warmed ovaries were immediately fixed after the collection (fresh) and the vitrification-warming process (vitrification control, vitri-con), respectively. Of those experimental groups, three were auto-transplanted with fresh whole ovary (FrOT; FrOT-D2, FrOT-D7 and FrOT-D21). For the other three groups, the ovaries were harvested and stored in liquid nitrogen for 1 week after vitrification and then warmed to auto-transplant the vitrified whole ovaries (vitrified ovary [VtOT]; VtOT-D2, VtOT-D7 and VtOT-D21). After 2, 7 or 21 days of grafting, the grafts and blood sera were collected for analysis by hematoxylin-eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, CD31 immunohistochemistry and follicle-stimulating hormone enzyme-linked immunosorbent assay.

MAIN RESULTS AND THE ROLE OF CHANCE

The vitrification-warming procedure decreased the proportion of intact follicles (Grade 1, G1) (vitri-con 50.3% versus fresh 64.2%) but there was a larger decrease due to ischemic injury after transplantation (FrOT-D2: 42.5%). The percentage of apoptotic follicles was significantly increased in the vitrified-warmed ovary group compared with the fresh control, but it increased more after transplantation without vitrification (fresh: 0.9%, vitri-con: 6.0% and FrOT-D2: 26.8%). The mean number of follicles per section and percentage of CD31-positive area significantly decreased after vitrification but decreased to a larger extent after transplantation (number of follicles, fresh: 30.3 ± 3.6, vitri-con: 20.6 ± 2.9, FrOT-D2: 17.9 ± 2.1; CD31-positive area, fresh: 10.6 ± 1.3%, vitri-con: 5.7 ± 0.9% and FrOT-D2: 4.2 ± 0.4%). Regarding the G1 follicle ratio and CD31-positive area per graft, only the FrOT groups significantly recovered with time after transplantation (G1 follicle ratio, FrOT-D2: 42.5%, FrOT-D7: 56.1% and FrOT-D21: 70.7%; CD31-positive area, FrOT-D2: 4.2 ± 0.4%, FrOT-D7: 5.4 ± 0.6% and FrOT-D21: 7.5 ± 0.8%). Although there was no significant difference between the two transplantation groups at each evaluation, the serum follicle-stimulating hormone level of both groups significantly decreased over time.

LIMITATIONS AND REASONS FOR CAUTION

It is unclear how far these results can be extrapolated from mice to the human ovary.

WIDER IMPLICATIONS OF THE FINDINGS

Minimizing ischemic injury should be the first priority rather than preventing cryoinjury alone, and decreasing the combination of cryoinjury and ischemic injury is necessary to improve ovarian quality after cryopreservation and transplantation.

STUDY FUNDING/COMPETING INTEREST

This study was supported by a grant of the Korea Healthcare Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI12C0055). The authors have no conflict of interest to declare.