Effect of Catalase or Alpha Lipoic Acid Supplementation in the Vitrification Solution of Ovine Ovarian Tissue

Current Fertility Preservation Steps in Young Women Suffering from Cancer and Future Perspectives

Childhood cancer incidence, especially in high-income countries, has led to a focus on preserving fertility in this vulnerable population. The common treatments, such as radiation and certain chemotherapeutic agents, though effective, pose a risk to fertility. For adult women, established techniques like embryo and egg freezing are standard, requiring ovarian stimulation. However, for prepubescent girls, ovarian tissue freezing has become the primary option, eliminating the need for hormonal preparation. This review describes the beginning, evolution, and current situation of the fertility preservation options for this young population. A total of 75 studies were included, covering the steps in the current fertility preservation protocols: (i) ovarian tissue extraction, (ii) the freezing method, and (iii) thawing and transplantation. Cryopreservation and the subsequent transplantation of ovarian tissue have resulted in successful fertility restoration, with over 200 recorded live births, including cases involving ovarian tissue cryopreserved from prepubescent girls. Despite promising results, challenges persist, such as follicular loss during transplantation, which is attributed to ischemic and oxidative damage. Optimizing ovarian tissue-freezing processes and exploring alternatives to transplantation, like in vitro systems for follicles to establish maturation, are essential to mitigating associated risks. Further research is required in fertility preservation techniques to enhance clinical outcomes in the future. Ovarian tissue cryopreservation appears to be a method with specific benefits, indications, and risks, which can be an important tool in terms of preserving fertility in younger women.

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.

Ovarian tissue cryopreservation and transplantation: a review on reactive oxygen species generation and antioxidant therapy

Cancer is the leading cause of death worldwide. Fortunately, the survival rate of cancer continues to rise, owing to advances in cancer treatments. However, these treatments are gonadotoxic and cause infertility. Ovarian tissue cryopreservation and transplantation (OTCT) is the most flexible option to preserve fertility in women and children with cancer. However, OTCT is associated with significant follicle loss and an accompanying short lifespan of the grafts. There has been a decade of research in cryopreservation-induced oxidative stress in single cells with significant successes in mitigating this major source of loss of viability. However, despite its success elsewhere and beyond a few promising experiments, little attention has been paid to this key aspect of OTCT-induced damage. As more and more clinical practices adopt OTCT for fertility preservation, it is a critical time to review oxidative stress as a cause of damage and to outline potential ameliorative interventions. Here we give an overview of the application of OTCT for female fertility preservation and existing challenges; clarify the potential contribution of oxidative stress in ovarian follicle loss; and highlight potential ability of antioxidant treatments to mitigate the OTCT-induced injuries that might be of interest to cryobiologists and reproductive clinicians.

The protective effects of astaxanthin on pre-antral follicle degeneration in ovine vitrified/warmed ovarian tissue

This study assesses the protective effects of astaxanthin (AST) against vitrification/warming-induced cryoinjuries of ovarian tissue slices in sheep. Cortical slices of slaughterhouse acquired-ovine ovaries were randomly distributed in different groups: fresh, toxicity, and five vitrification groups including vitrification in presence of 0 (control group), 1, 10 and 100 μM astaxanthin or 100 μM vitamin E. After vitrification/warming and 24 h culturing, the samples were subjected to histological studies, antioxidant evaluation by TAC and TBAR assays, and assessment of relative expression of BMP4, BMP15, GDF9 and KITLG genes related to folliculogenesis and follicular growth regulation. According to the results, vitrification reduced the percentage of morphologically intact follicles compared to the fresh and toxicity groups (p < 0.05). In vitrification groups, vitamin E and all three concentrations of AST increased the percentage of intact pre-antral follicles and antioxidant activity relative to the vitrified control (p < 0.05). This enhancement significantly occurred in 10 μM AST group more than vitamin E (p < 0.05). Also, 10 μM concentration of AST enhanced the expression of all the examined genes compared to the control (p < 0.05), while the expression of BMP4, BMP15 and KITLG was higher in the AST than vitamin E (p < 0.05). The latter could increase only the expression of GDF9 compared to the control group (p = 0.011). In conclusion, AST is a highly effective antioxidant for maintaining the survival of pre-antral follicles, retaining cell density, increasing total antioxidant capacity, and increasing the expression of some genes related to follicular development after short-term culture of vitrified/warmed ovarian tissue slices.

Quantification of residual cryoprotectants and cytotoxicity in thawed bovine ovarian tissues after slow freezing or vitrification

STUDY QUESTION

How much residual cryoprotectant remains in thawed/warmed ovarian tissues after slow freezing or vitrification?

SUMMARY ANSWER

After thawing/warming, at least 60 min of diffusion washing in media was necessary to significantly reduce the residual cryoprotectants in ovarian tissues frozen by slow freezing or vitrification.

WHAT IS KNOWN ALREADY

Ovarian tissue cryopreservation (OTC) by slow freezing has been the conventional method; while the vitrification method has gained popularity for its practicality. The main concern about vitrification is how much potentially toxic residual cryoprotectant remains in the warmed tissues at the time of transplantation.

STUDY DESIGN, SIZE, DURATION

This was an animal study using the ovarian tissues from 20 bovine ovaries. The duration of this study was from 2018 to 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ovarian cortex tissues were prepared from 20 bovine ovaries and assigned randomly to groups of fresh (non-frozen) control, slow freezing with 1.5 M dimethyl sulfoxide (DMSO), 1.5 M 1,2-propanediol (PROH) and vitrification with 35% ethylene glycol (EG). The residual cryoprotectant concentrations in thawed/warmed tissues were measured by gas chromatography at the following time points: frozen (before thawing/warming), 0 min (immediately after thawing/warming), 30, 60 and 120 min after diffusion washing in media. Next, the ultrastructural changes of primordial follicles, granulosa cells, organelles and stromal cells in the ovarian tissues (1 mm × 1 mm × 1 mm) were examined in fresh (non-frozen) control, slow freezing with DMSO or PROH and vitrification with EG groups. Real-time quantitative PCR was carried out to examine the expressions of poly (ADP-ribose) polymerase-1 (PARP1), a DNA damage sensor and caspase-3 (CASP3), an apoptosis precursor, in thawed/warmed ovarian tissues that were washed for either 0 or 120 min and subsequently in tissues that were ex vivo cultured for 24 or 48 h. The same set of tissues were also used to analyze the protein expressions of gamma H2A histone family member X (γH2AX) for DNA double-strand breaks and activated caspase-3 (AC3) for apoptosis by immunohistochemistry.

MAIN RESULTS AND THE ROLE OF CHANCE

The residual cryoprotectant concentrations decreased with the extension of diffusion washing time. After 60 min washing, the differences of residual cryoprotectant between DMSO, PROH and EG were negligible (P > 0.05). This washing did not affect the tissue integrity or significantly elevate the percentage of AC3 and γH2AX positive cells, indicating that tissues are safe and of good quality for transplantation.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Since the study was performed with ovarian tissues from bovines, generalizability to humans may be limited. Potential changes in ovarian tissue beyond 120 min were not investigated.

WIDER IMPLICATIONS OF THE FINDINGS

This study addresses concerns about the cytotoxicity of EG in warmed ovarian tissues and could provide insights when devising a standard vitrification protocol for OTC.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by a Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science to N.S.

Ovarian tissue features assessed in bovine fetuses after vitrification and xenotransplantation procedures

Cryopreservation and transplantation of ovarian tissue are proposed methods for the restoration of endocrine function and reproductive potential. Therefore, this study aimed to evaluate the effects of vitrification and xenotransplantation on follicle viability, activation, stromal cell integrity, vascularization, and micronuclei formation. Bovine fetal ovaries were fragmented and assigned to the following groups: Fresh control (FC), ovarian fragments immediately fixed; Vitrified control (VC), ovarian fragments vitrified; Vitrified xenotransplanted (VX), ovarian fragments vitrified and xenotransplanted; and Fresh xenotransplanted (FX), ovarian fragments xenotransplanted. Ovarian fragments were grafted in female BALB/c mice and recovered after 14 days. Follicular viability was preserved (P >  0.05) in VC group. The rate of developing follicles was greater (P <  0.05) in the FX group compared to other groups. Follicular density was higher (P <  0.05) in the VC group than the FC, VX, and FX groups. A decrease (P <  0.05) of stromal cell density was recorded after vitrification (VC vs. FX). Blood vessel density decreased in VC, VX, and FX groups compared with the FC group, and blood vessel density was correlated with follicular viability (positively; P =  0.07) and developing follicles (negatively; P <  0.001). Both vitrification and xenotransplantation groups (VC, VX, and FX) had a greater (P <  0.05) number of cells with one MN compared to the FC group. In summary, our findings showed that both vitrification and xenotransplantation modified blood vessel, follicular and stromal cell densities, follicular viability and activation, and micronuclei formation in ovarian tissue.

Vitrification of canine ovarian tissue using the Ovarian Tissue Cryosystem (OTC) device

The present study evaluated the effect of Ovarian Tissue Cryosystem (OTC) on follicular morphology and density, as well as on stromal cell density of vitrified canine ovarian tissue. Canine ovarian fragments collected from adult female dogs in stages of the random oestrous cycle were fixed (FC, fresh control) or vitrified (VIT) with an OTC device. After vitrification and warming, the fragments were fixed for histological analysis. Overall, the mean percentage of normal pre-antral follicles decreased after vitrification procedure (FC: 74.5% ± 1.6% vs. VIT: 52.05% ± 1.5%). Although the rates of normal primordial (71.1% ± 1.8%) and secondary (0.7% ± 0.4%) follicles vitrified showed a reduction (p < .05), vitrification using OTC showed considerable preservation of follicles, when compared to the fresh control (81.1% ± 1.5% and 2.3% ± 0.6%, respectively). The mean follicular density was maintained after vitrification (FC: 199.65 ± 12.8 vs. VIT: 199.68 ± 10.8), whereas the stromal cell density decreased in the VIT group. Based on the results, we recommend the use of OTC for vitrification of canine ovarian tissue.

N-acetyl-cysteine and the control of oxidative stress during in vitro ovarian follicle growth, oocyte maturation, embryo development and cryopreservation

Oxidative stress is generated by an imbalance between reactive oxygen species (ROS) formation and cellular defense mechanisms. To reduce cellular damage caused by ROS in vivo or in vitro, N-acetyl-cysteine (NAC) is converted into metabolites that have the capacity of stimulating synthesis of glutathione (GSH) which functions directly as free radical scavengers. The NAC antioxidant potential evaluated to the greatest extent is the indirect action of NAC, as a precursor of GSH, with glutathione being the primary antioxidant in cells. During long-term preantral follicle culture, NAC has a synergic action with FSH and an important function in sustaining preantral follicle growth and follicle-cell viability in vitro. The NAC inclusion in in vitro maturation medium for cumulus-oocyte complexes (COC) leads to protection of oocytes from damage induced by heat stress, reductions in ROS, and increases in cumulus cell expansion. Developing embryos are susceptable to oxidative stress because of susceptability to cellular structure damage and not having well-developed defense mechanisms. Results from various indicate there are beneficial effects of NAC on embryonic development by increasing GSH biosynthesis and regulating cell proliferation. In addition, NAC is also an effective antioxidant during cryopreservation of ovarian follicles, oocytes and embryos, because inclusion of NAC in preservation medium leads to improvements in mitochondrial function and cell viability, and reductions in ROS and cellular apoptosis. In this review, there is evaluation of mechanisms of action of NAC and beneficial effects during in vitro culture of preantral follicles, as well as oocyte maturation, embryonic development and cryopreservation.

Alpha Lipoic Acid Supplementation Improves Ovarian Tissue Vitrification Outcome: An Alternative to Preserve the Ovarian Function of Morada Nova Ewe

This study evaluated the effect of adding alpha lipoic acid (ALA) to the vitrification solution of sheep ovarian tissue on 7 days of in vitro culture or 15 days of xenotransplantion. ALA was used at two different concentrations (100 μM: ALA100 and 150 μM: ALA150). Ovarian tissue was evaluated by classical histology (follicular morphology, development, and stromal cell density); immunohistochemistry for forkhead box O3a (FOXO3a); Ki67 (cell proliferation); cluster of differentiation 31 (CD31); and alpha smooth muscle actin (α-SMA). Reactive oxygen species (ROS) levels in ovarian tissue, as well as malondialdehyde (MDA) and nitrite levels in the culture medium, were assessed. Similar percentage of morphologically normal follicles was found in the vitrified ovarian tissue in the presence of ALA100 or ALA150 after in vitro culture or xenotransplantation. Follicular development from all treatments was higher (P < 0.05) than the control group. Moreover, an activation of primordial follicles was observed by FOXO3a. Stromal cell density and immunostaining for Ki67 and CD31 were significantly higher (P < 0.05) in ALA150 vitrified tissue. No difference (P > 0.05) was found in α-SMA between ALA concentrations after in vitro culture or xenograft. ROS levels in the ovarian tissue were similar (P > 0.05) in all treatments, as well as MDA and nitrite levels after 7 days of culture. We concluded that the addition of ALA 150 is able to better preserve the stromal cell density favoring granulosa cell proliferation and neovascularization.

Initial response of ovarian tissue transcriptome to vitrification or microwave-assisted dehydration in the domestic cat model

Background

Long term preservation of living ovarian tissues is a critical approach in human reproductive medicine as well as in the conservation of rare animal genotypes. Compared to single cell preservation, optimization of protocols for tissues is highly complex because of the diversity of cells responding differently to non-physiological conditions. Using the prepubertal domestic cat as a model, the objective was to study immediate effects of vitrification or microwave-assisted dehydration on the global transcriptome dynamics in the ovarian cortex. RNA sequencing was performed on ovarian tissues (n = 6 individuals) from different conditions: fresh tissue after dissection (F), vitrified/warmed tissue (V), tissue dehydrated for 5 min (D5) or 10 min (D10) followed by rehydration. Differential gene expression analysis was performed for comparison pairs V vs. F, D10 vs. F, D5 vs. F and D10 vs. D5, and networks were built based on results of functional enrichment and in silico protein-protein interactions.

Results

The impact of the vitrification protocol was already measurable within 20 min after warming and involved upregulation of the expression of seven mitochondrial DNA genes related to mitochondrial respiration. The analysis of D10 vs. F revealed, 30 min after rehydration, major downregulation of gene expression with enrichment of in silico interacting genes in Ras, Rap1, PI3K-Akt and MAPK signaling pathways. However, comparison of D5 vs. F showed negligible effects of the shorter dehydration protocol with two genes enriched in Ras signaling. Comparison of D10 vs. D5 showed downregulation of only seven genes. Vitrification and dehydration protocols mainly changed the expression of different genes and functional terms, but some of the differentially expressed genes formed a major in silico protein-protein interaction cluster enriched for mitochondrial respiration and Ras/MAPK signaling pathways.

Conclusions

Our results showed, for the first time, different effects of vitrification and microwave-assisted dehydration protocols on the global transcriptome of the ovarian cortex (using the domestic cat as a biomedical model). Acquired data and networks built on the basis of differentially expressed genes (1) can help to better understand stress responses to non-physiological stresses and (2) can be used as directions for future preservation protocol optimizations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07236-z.

Natural antioxidants in the vitrification solution improve the ovine ovarian tissue preservation

The present study evaluated the effect of the addition of antioxidants anethole (AN) and robinin (RO) in the vitrification solution, and the in vitro incubation (IVI) medium of ovine ovarian tissue. Ovarian fragments were vitrified without antioxidant (VWA) or with different concentrations of AN (30, 300 and 2000 μg/mL) or RO (0.125, 0.25 and 0.50 mg/mL), followed by IVI (24 h). Histological analyses showed that the percentage of morphologically normal preantral follicles (MNPF) in AN 2000 did not differ from RO 0.125 or fresh ovarian tissue (CTR). Subsequently, ovarian fragments were vitrified in the presence of AN 2000 and RO 0.125 followed by IVI without or with (AN 2000+ and RO 0.125+) the same antioxidants. The follicular activation in all treatments was significantly increased as compared to the CTR. The stroma cell density (SCD) in all the vitrified fragments was significantly lower than the CTR. However, in the AN 2000 and RO 0.125 this parameter was significantly higher when compared to the VWA. The reactive oxygen species (ROS) in the ovarian cortex of the AN 2000 or AN 2000+ were significantly reduced in comparison with the CTR while the intracellular ROS levels of AN 2000 and CTR were similar. The total antioxidant capacity (TAC) in RO 0.125 was significantly higher than that of VWA, AN 2000 and AN 2000+. According to the results, the use of antioxidants (AN or RO) only in the vitrification solution of ovine ovarian tissue is recommended, due to their better preservation of the SCD. Moreover, AN 2000 best maintains the follicular morphology, while RO 0.125 has a high TAC.