Novel direct cover vitrification for cryopreservation of ovarian tissues increases follicle viability and pregnancy capability in mice

Preserving Porcine Genetics: A Simple and Effective Method for On-Site Cryopreservation of Ear Tissue Using Direct Cover Vitrification

Cell cryopreservation is widely used for porcine genetic conservation; however, isolating and freezing primary cells in farms without adequate experimental equipment and environment poses a significant challenge. Therefore, it is necessary to establish a quick and simple method to freeze tissues on-site, which can be used for deriving primary fibroblasts when needed to achieve porcine genetic conservation. In this study, we explored a suitable approach for porcine ear tissue cryopreservation. The porcine ear tissues were cut into strips and frozen by direct cover vitrification (DCV) in the cryoprotectant solution with 15% EG, 15% DMSO and 0.1 M trehalose. Histological analysis and ultrastructural evaluation revealed that thawed tissues had normal tissue structure. More importantly, viable fibroblasts could be derived from these tissues frozen in liquid nitrogen for up to 6 months. Cells derived from thawed tissues did not show any cell apoptosis, had normal karyotypes and could be used for nuclear transfer. These results suggest that this quick and simple ear tissue cryopreservation method can be applied for porcine genetic conservation, especially in the face of a deadly emerging disease in pigs.

Review of ovarian tissue cryopreservation techniques for fertility preservation

Ovarian failure and ovarian malfunction are among major fertility problems in women of reproductive age (18-35 years). It is known that various diseases, such as ovarian cancer and premature ovarian failure, besides certain treatments, such as radiotherapy and chemotherapy of other organs, can affect the normal process of folliculogenesis and cause infertility. In recent years, various procedures have been proposed for the treatment of infertility. One of the newest methods is the use of cryopreservation ovarian fragments after cancer treatment. According to some studies, this method yields very satisfactory results. Although ovarian tissue cryopreservation (OTC) is an accepted technique of fertility preservation, the relative efficacy of cryopreservation protocols remains controversial. Considering the controversies about these methods and their results, in this study, we aimed to compare different techniques of ovarian cryopreservation and investigate their advantages and disadvantages. Reviewing the published articles may be possible to identify appropriate strategies and improve infertility treatment in these patients.

Effect of retinol as antioxidant on the post-thaw viability and the expression of apoptosis and developmental competence-related genes of vitrified preantral follicles in buffalo (Bubalus bubalis)

The present study evaluated the effect of supplementation of retinol in the vitrification solution on the viability, apoptosis and development-related gene expression in vitrified buffalo preantral follicles. Preantral follicles isolated from cortical slices of ovaries were randomly assigned into three groups: Group1-Control fresh preantral follicles; Group 2-Vitrification treatment (Vitrification solution 1 (VS1) -TCM-199 + 25 mM HEPES + Foetal bovine serum (FBS) 10%, Ethylene glycol (EG): 10%, Dimethyl sulphoxide (DMSO): 10%, Sucrose-0.3 M for 4 min; VS2- TCM-199 + 25 mM HEPES + FBS10%, EG:25%, DMSO: 25%, Sucrose:0.3 M for 45 s); Group3-vitrification treatment +5 μM of Retinol. Preantral follicles were placed in corresponding vitrification medium and plunged into liquid nitrogen (-196°C). After a week, the follicles were thawed and analysed for follicular viability and gene expression. There was no significant difference in the viability rates among the Group 1(Fresh preantral follicles) (91.46 ± 2.39%), Group 2 (89.59 ± 2.46%) and Group 3 (87.19 ± 4.05%). There was a significantly (p < .05) higher mRNA expression of BCL2L1, GDF-9 and BMP-15 in the vitrification + retinol group compared with the control group. There was a significantly (p < .05) higher expression of Caspase-3 and Annexin-5 in the vitrification group and Vitrification + retinol group compared with control group of follicles. It is concluded that the supplementation of 5 μM of Retinol in Vitrification solution was an efficient vitrification procedure for the vitrification of buffalo preantral follicles.

Vitrification of Dog Skin Tissue as a Source of Mesenchymal Stem Cells

The purpose of this study was to develop an efficient vitrification system for cryopreservation of dog skin tissues as a source of stable autologous stem cells. In this study, we performed vitrification using four different cryoprotectants, namely, ethylene glycol (EG), dimethyl-sulfoxide (Me2SO), EG plus Me2SO, and EG plus Me2SO plus sucrose, and analyzed the behaviors of cells established from warmed tissues. Tissues vitrified with 15% EG, 15% Me2SO, and 0.5 M sucrose had a normal histological appearance and the highest cell viability after cell isolation, and thus, this cocktail of cryoprotectants was used in subsequent experiments. We evaluated proliferation and apoptosis of cells derived from fresh and vitrified tissues. These cells had a normal spindle-like morphology after homogenization through subculture. Dog dermal skin stem cells (dDSSCs) derived from fresh and vitrified tissues had similar proliferation capacities, and similar percentages of these cells were positive for mesenchymal stem cell markers at passage 3. The percentage of apoptotic cell did not differ between dDSSCs derived from fresh and vitrified tissues. Real-time PCR analysis revealed that dDSSCs at passage 3 derived from fresh and vitrified tissues had similar expression levels of pluripotency (OCT4, SOX2, and NANOG), proapoptotic (BAX), and antiapoptotic (BCL2 and BIRC5) genes. Both types of dDSSCs successfully differentiated into the mesenchymal lineage (adipocytes and osteocytes) under specific conditions, and their differentiation potentials did not significantly differ. Furthermore, the mitochondrial membrane potential of dDSSCs derived from vitrified tissues was comparable with that of dDSSCs derived from fresh tissues. We conclude that vitrification of dog skin tissues using cocktail solution in combination of 15% EG, 15% Me2SO, and 0.5 M sucrose allows efficient banking of these tissues for regenerative stem cell therapy and conservation of genetic resources.

Comparison between two cryopreservation techniques of human ovarian cortex: morphological aspects and the heat shock response (HSR)

This study was tailored to compare the cryopreservation of the human ovarian cortex using closed metal container vitrification or the slow-freezing technique. Superficial ovarian cortical tissue biopsies were collected from 12 participants who underwent gynaecological videolaparoscopy. The fragmented samples were allocated to three experimental conditions: (a) fresh ovarian tissue, (b) slow-freezing, and (c) vitrification with a metal closed container. After thawing or rewarming, cellular morphological analyses were performed to determine tissue viability. The cellular response to thermal stress was measured by a putative increase in the immune quantification of the heat shock protein 70 kDa (heat shock protein 70 kDa response - HSR) after a heat challenge (2 h exposure at 42 °C). Both the total number of intact follicles and the frequency of primordial follicles were higher in fresh ovarian tissue than in the preserved samples, regardless of the technique employed. There was a trend towards an increase in the absolute number of intact follicles in the tissue preserved by vitrification. After cryopreservation, a higher HSR was obtained after slow-freezing. These results indicate that both cryopreservation techniques present advantages and may be used as alternatives to ovarian tissue cryopreservation.

Optimizing ovarian tissue quality before cryopreservation: comparing outcomes of three decortication methods on stromal and follicular viability

OBJECTIVE

To evaluate whether specific ovarian decortication techniques vary in promoting ovarian cortex cryopreservation and transplant outcomes.

DESIGN

Experimental design.

SETTING

University hospital.

ANIMAL(S)

Nonobese diabetic (NOD)/severe combined immunodeficiency (SCID) female mice.

INTERVENTION(S)

Human ovarian biopsy samples allocated to one of the following decortication procedures: scratching with scalpel blade (B), cutting with microsurgical scissors (M), separation with slicer (S), or no-separation (control, C). Parallel, in vivo experiment: decortication techniques combined with slow freezing (SF) and vitrification (VT) before xenograft into immunodeficient mice.

MAIN OUTCOME MEASURE(S)

Follicular counts, apoptosis, shear stress, Hippo pathway and inflammation. In vivo: recovered grafts analyzed for follicular counts, angiogenesis, proliferation, and fibrosis.

RESULT(S)

There were no differences in follicular density or number of damaged follicles between the decortication techniques in the in vitro study. Nevertheless, the M samples showed statistically significantly increased stromal damage compared with the controls and S samples, and up-regulation of Hsp60 shear stress gene expression. Decortication by both M and S inhibited the Hippo pathway, promoting gene expression changes. In the 21-day xenograft, total follicular density statistically significantly decreased compared with the nongrafted controls in all groups. Nevertheless, no differences were observed between the decortication techniques. Ovarian stroma vascularization was increased in the vitrified samples, but among the slow-freezing samples, the B samples had the lowest microvessel density. The M decorticated xenografts had increased fibrosis.

CONCLUSION(S)

Decortication with a slicer causes less damage to ovarian tissue than other commonly used methods although microsurgical scissors seem to preserve slightly increased follicular numbers. Nevertheless, blade decortication seems to be a reliable technique for maintaining acceptable follicular conditions without inducing serious stromal impairment.

Effects of Different Vitrification Solutions and Protocol on Follicular Ultrastructure and Revascularization of Autografted Mouse Ovarian Tissue

Objective

Many attempts have been made to preserve fertility by improving the cryopreservation of the ovarian tissue. This current studyaimed to improve of direct cover vitrification (DCV) protocol on follicular preservation and angiogenesis in autografted ovarian tissue.

Materials and Methods

In this experimental study, sixty five female Balb/c mice (5-6 week-old) were anesthetized and their ovaries were dissected. The left ovaries were vitrified by DCV solution, thawed by descending concentrations of sucrose, and then autografted subcutaneously. The right ovaries were autografted with no vitrification procedure prior to transplantation. The animals were sacrificed under anesthesia on the 7thday after transplantation to obtain ovarian tissue. Follicular quality was assessed by histological and ultrastructure observations, and angiogenesis was examined by immunohistochemical staining and real-time polymerase chain reaction (PCR) analysis.

Results

The histological and ultrastructure features of the follicles preserved well after vitrification of the ovarian tissue by 10% ethylene glycol (EG) and 10% dimethyl sulfoxide (DMSO). Revascularizationwas manifested prominently in the DCV1-vitrified/grafted ovaries by von Willebrand factor (vWF) and alpha smooth muscle actin (α-SMA) immunostaining. The ovarian tissue vitrified in DCV1 protocol had higher expression levels of angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF) 7 days after autotransplantation (P<0.01).

Conclusion

These findings suggest that DCV with 10% of both EG and DMSO, is an effective cryopreservation solution for preservation of good quality follicles as well an upregulation of angiogenic factors after ovarian tissue transplantation.

The growth and development conditions in mouse offspring derived from ovarian tissue cryopreservation and orthotopic transplantation

PURPOSE

To investigate the potential development or metabolic risk in offspring derived from mice with transplanted frozen-thawed ovarian tissue.

METHODS

Mice ovaries were intervened by vitrification (group V) and slow-freezing (group S) cryopreservation and orthotopic transplantation. Orthotopic transplantation of fresh ovarian (group F) and natural mating (group C) served as control groups. The fertility restoration and health conditions of generations were assessed by offspring counts, anti-fatigue and motor ability, and organ morphology. The methylation rate and expression level of imprinted genes (IGF2R, H19, SNRPN, and PLAGL1) were used to predict the potential risk of development in transplanted generations.

RESULTS

Both the percentage of normal morphological follicles in different developmental periods and the litter size of receipt mice were comparable in all three transplanted groups. There was no significant difference in offspring mice's birth defects, body weight gain, anti-fatigue ability, or exercise capacity among the four groups. The methylation rate of IGF2R, H19, and PLAGL1 showed a significant variation in cryopreservation groups as compared with control groups, as well as a difference in gene expression. The SNRPN appeared to be stable in methylation status. There were no differences in mRNA expression in all groups.

CONCLUSIONS

The different ovarian tissue cryopreservation methods did not influence either maternal fertility function or offspring growth. However, these technologies could affect the methylation rate and expression level of some development-related imprinting genes in the offspring, which may lead to some indeterminacy risk.

Slow Freezing Versus Vitrification of Mouse Ovaries: from Ex Vivo Analyses to Successful Pregnancies after Auto-Transplantation

Slow freezing (SF) is the reference method for ovarian tissue cryopreservation. Vitrification (VT) constitutes an alternative but controversial method. This study compares SF and VT (open [VTo] and closed [VTc] systems) in terms of freezing damage and fertility restoration ability. In vitro analyses of C57Bl/6 SF or VTo-ovaries, immediately after thawing/warming or after culture (cult), revealed that event though follicular density was similar between all groups, nuclear density was decreased in VTo-ovaries compared to CT-ovaries (CT = 0.50 ± 0.012, SF = 0.41 ± 0.03 and VTo = 0.29 ± 0.044, p < 0.01). Apoptosis was higher in VTo-cult ovaries compared to SF-cult ovaries (p < 0.001) whereas follicular Bmp15 and Amh gene expression levels were decreased in the ovaries after culture, mostly after VTo (p < 0.001). Natural mating after auto-transplantation of SF, VTo and VTc-ovaries revealed that most mice recovered their oestrous cycle. Fertility was only restored with SF and VTo ovaries (SF: 68%; VTo: 63%; VTc: 0%; p < 0.001). Mice auto-transplanted with SF and VTo-ovaries achieved the highest number of pregnancies. In conclusion, in vitro, no differences between SF and VTo were evident immediately after thawing/warming but VTo ovaries displayed alterations in apoptosis and follicular specific proteins after culture. In vivo, SF and VTo ovary auto-transplantation fully restored fertility whereas with VTc-ovary auto-transplantation no pregnancies were achieved.

In vitro growth and development of isolated secondary follicles from vitrified caprine ovarian cortex

The aim of this study was to evaluate the viability, antrum formation and in vitro development of isolated secondary follicles from vitrified caprine ovarian cortex in a medium previously established for fresh isolated secondary follicles, in the absence (α-minimum essential medium (α-MEM+) alone) or presence of FSH and vascular endothelial growth factor (VEGF; α-MEM++FSH+VEGF). Ovarian fragments were distributed among five treatments (T1 to T5): fresh follicles were fixed immediately (T1), follicles from fresh tissue were cultured in vitro in α-MEM+ (T2) or α-MEM++FSH+VEGF (T3) and follicles from vitrified tissue were cultured in vitro in α-MEM+ (T4) or α-MEM++FSH+VEGF (T5). After 6 days of culture, treated follicles (T2, T3, T4 and T5) were evaluated for morphology, viability and follicular development (growth, antrum formation and proliferation of granulosa cells by Ki67 and argyrophilic nucleolar organiser region (AgNOR) staining). The levels of reactive oxygen species (ROS) in the culture media were also assessed. Overall, morphology of vitrified follicles was altered (P<0.05) compared with the fresh follicles. Follicular viability, antrum formation and ROS were similar between treatments (P>0.05). The average overall and daily follicular growth was highest (P<0.05) in T3. Granulosa cells in all treatments (T1, T2, T3, T4 and T5) stained positive for Ki67. However, fresh follicles from T3 had significantly higher AgNOR staining (P<0.05) compared with follicles of T1, T2, T4 and T5. In conclusion, secondary follicles can be isolated from vitrified and warmed ovarian cortex and survive and form an antrum when growing in an in vitro culture for 6 days.

Oocyte retrieval after heterotopic transplantation of ovarian tissue cryopreserved by closed vitrification protocol

PURPOSE

A device for closed vitrification was designed to reduce the risk of contamination and investigated on its efficacy for ovarian function recovery after cryopreservation and heterotopic transplantation.

METHODS

Ovarian tissues from green fluorescence protein transgenic mice (10 GFP mice) were vitrified using the device, and warmed ovarian tissues were transplanted into the ovarian bursa region in wild-type female mice (6 mice). Fresh ovarian tissues were similarly transplanted as a control. After recovery of the estrous cycle, mice were mated with male mice. Ovarian tissues from six cynomolgus monkeys were vitrified and warmed with the device for autologous, heterotopic transplantation. Fresh tissue transplantation was not performed for the control. Ovarian function was examined by recovery of the hormonal cycle. Histological examination was conducted.

RESULTS

The number of live pups per recipient mouse was not significantly different after transplantation of fresh or vitrified-warmed ovarian tissue, although the pregnancy rate was reduced with vitrified tissues. The hormonal cycle was restored in 5/6 monkeys after heterotopic transplantation of vitrified-warmed ovarian tissue. Follicles were harvested at eight sites in the omentum and 13 sites in the mesosalpinx. In vitro maturation (IVM)/IVF produced embryo but did not develop.

CONCLUSIONS

Resumption of the hormonal cycles, follicle development, and oocyte retrieval from vitrified-warmed ovarian tissue transplants may indicate that the use of vitrification for ovarian tissue in a closed system has a potential of clinical application without the risk of contaminations. More detailed analyses of the effects of vitrification on ovarian tissue, such as gene expression patterns in oocytes and granulosa cells, may be needed for establishing a standard procedure for cryopreservation of ovarian tissues in human.

Antioxidant defense capacity of ovarian tissue after vitrification in a metal closed system

OBJECTIVE

The present study analyzed the quality of bovine ovarian tissue after vitrification in a metal closed chamber, in terms of putative changes in tissue viability (lactate dehydrogenase -LDH- release), anti-oxidant defenses, and redox parameters caused by cryopreservation.

METHODS

Small and large fragmented bovine ovarian tissue specimens were vitrified in a metal chamber. After rewarming, tissue samples were fixed or cultured for 48 hours. Glutathione (GSH), protein sulfhydryl content, Total Radical Trapping Antioxidant Potential (TRAP), and lactate dehydrogenase were analyzed immediately after rewarming and after tissue culture.

RESULTS

No changes in antioxidant parameters or viability of rewarmed tissue samples were found immediately or 48h after vitrification. The method of vitrification in a metal closed chamber used in this study preserved the quality of bovine ovarian tissue. Furthermore, our data showed that the size of the tissue specimens did not affect post-vitrification biochemical viability parameters.

CONCLUSIONS

We believe that the vitrification methodology employed in the present study is safe and effective, and should be evaluated for use in humans.

The mitochondrial DNA copy number, cytochrome c oxidase activity and reactive oxygen species level in metaphase II oocytes obtained from in vitro culture of cryopreserved ovarian tissue in comparison with in vivo-obtained oocyte

AIM

To evaluate the mitochondrial DNA (mtDNA) copy number, reactive oxygen species (ROS) level and intensity of mitochondrial enzyme activity in metaphase II oocytes derived from vitrified cultured immature mouse ovarian tissue in comparison with nonvitrified group and in vivo-obtained oocytes.

METHODS

Vitrified and nonvitrified ovaries from neonate female mice were cultured for 7 days. Then, preantral follicles were isolated and cultured in a three-dimensional culture system. Follicular development and oocyte maturation were evaluated and compared in both groups. Some of the collected metaphase II oocytes derived from in vitro and in vivo conditions were inseminated with capacitated spermatozoa, and then, the fertilization and embryo developmental rates were assessed. In the other series of oocytes, mtDNA copy number, distribution and enzyme activity and ROS level were analyzed.

RESULTS

The embryo development, mtDNA copy number and mitochondrial enzyme activity in collected metaphase II oocytes from two in vitro-cultured groups were significantly lower, and the ROS level was higher than those of the in vivo group (P < 0.05), but there was no significant difference between vitrified and nonvitrified groups.

CONCLUSION

This study showed that a two-step in vitro culture of mouse ovarian tissue decreased the mtDNA copy number and cytochrome c oxidase activity of metaphase II oocytes through an increase in their ROS level in comparison with in vivo-obtained oocytes. Thus, the in vitro culture methods should be improved.

Ovarian tissue vitrification and heterotopic autologous transplantation in prepubertal Wistar rats

OBJECTIVE

To evaluate the efficiency of ovarian tissue heterotopic autografting after vitrification in prepubertal rats.

METHODS

Fragments of excised ovaries from prepubertal rats were used after assessing post-warming cellular viability, to determine the best vitrification protocol prior to retroauricular autografting. Pre-pubertal females (N=24) were castrated and divided into three group: Group 1 - fresh ovarian tissue transplantation; Group 2 - vitrified/warmed tissue transplantation; Group 3 - bilateral oophorectomy without transplantation. The ovarian fragments were exposed to solutions from the Ingamed® commercial kit, allocated in bacteriological loops and immersed in liquid nitrogen. Sixty days after transplantation, a vaginal mucus sample was collected for cytology tests, followed by sacrificing the animal, performing a cardiac puncture for collecting a blood sample to determine luteinizing hormone and estradiol levels, and excision of the transplanted fragment for histology tests.

RESULTS

Vaginal cytology revealed that 87.5% of females from groups 1 and 2 had estrus while all females in Group 3 remained in diestrus. The mean LH value in groups 1 (0.08 mIU/mL) and 2 (0.34 mIU/mL) were statistically different from that of Group 3 (2.27 mIU/mL). E2 values did not differ between the groups. The histological analysis of Group 1 excised grafts versus those from Group 2 showed a higher percentage of primary follicles (62.5% vs. 12.5%), developing follicles (75% vs. 25%), corpus luteum (37.5% vs. 12.5%) and stromal region (100% vs. 87.5%).

CONCLUSION

This study indicated that pre-pubertal ovarian tissue vitrification can be used to preserve fertility and to restore endocrine function in castrated rats.

Assessment of DNA damage in goat preantral follicles after vitrification of the ovarian cortex

Effective methods for gamete preservation should have low impact on DNA integrity. The present study investigated the effects of vitrification of goat ovarian tissues on the occurrence of DNA fragmentation and DNA double-stand breaks using the terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) assay and detection of phosphorylated histone H2AX (γH2AX), respectively. Goat ovaries were collected at a local abattoir and 12 tissue fragments were prepared from each ovarian pair. Tissue fragments were used as fresh control samples or were cultured in vitro, vitrified or vitrified and cultured. Vitrification was performed using the Ovarian Tissue Cryosystem. Fragments from all groups (control and treatments) were processed for histology, transmission electron microscopy, TUNEL assay and immunofluorescence. Compared with fresh control samples, a lower percentage of morphologically normal follicles was detected in the vitrification followed by culture treatment group (P<0.05). Normal follicular ultrastructure was observed in all groups. Immunofluorescence revealed the presence of γH2AX foci in few oocytes and ovarian stromal cells. TUNEL-positive follicles were found in samples without significant differences among groups (P>0.05). In conclusion, the vitrification protocol used in the present study did not increase DNA damage in preantral follicles enclosed in goat ovarian tissues.

Impact of GnRHa pretreatment on the autotransplatation efficacy of cytopreserved rat ovarian tissue

Pre-therapeutic cryopreservation of ovarian tissue and subsequent transplantation after disease remission has recently emerged as an option to restore endocrinal function and preserve fertility for patients subjected to gonadotoxic treatments such as chemotherapy. However, the relatively low survival rate of follicles after grafting the frozen-thawed ovarian tissue largely limited the application of this technique. Gonadotropin-releasing hormone analogues (GnRHa), owing to their endocrinal regulatory effect, have been successfully used for fertility preservation against gonadotoxic conditions such as cytotoxic agents based anti-cancer therapy. In this study, we evaluated the potential protective effect of precedent GnRHa treatment before cryopreservation on freezing-thawing related follicular damages using a rat autoxenograft model. We have observed that GnRHa significantly increases the fraction of follicles with normal morphology, while presenting negnigible effect on the physiological recovery of the grafted follicular tissue, as demonstrated by the estrous cycle, folliculogenesis and post-autograft vascularization. Our data implicates that GnRHa pretreatment may effectively increase the efficacy of cryopreservation and the subsequent successful rate of transplantation.

Antioxidant properties of coenzyme Q10-pretreated mouse pre-antral follicles derived from vitrified ovaries

AIM

This study evaluated the antioxidant status of pre-antral follicles derived from vitrified ovaries pretreated with coenzyme Q10 (CoQ10).

METHODS

Mouse pre-antral follicles derived from fresh and vitrified warmed ovarian tissue were cultured with or without CoQ10 (50 μmol/L). Follicular growth, total antioxidant capacity (TAC), malondialdehyde (MDA) level, and superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) activity during cultivation were assessed.

RESULTS

The growth rate of the fresh pre-antral follicles was higher compared with the vitrified groups, especially in the CoQ10-treated than non-treated groups. MDA increased while TAC decreased at 96 h of the cultivation period. TAC was higher while MDA was lower in the fresh pre-antral follicles than in the vitrified groups. These rates were higher in the CoQ10-treated than non-treated groups. The vitrified and fresh CoQ10-pretreated groups had significantly higher SOD, GPX, and CAT activity compared with the CoQ10 non-treated groups.

CONCLUSION

CoQ10-supplemented maturation medium can increase antioxidant enzyme activity and decrease lipid peroxidation in cultured pre-antral follicles derived from fresh and vitrified mouse ovaries.

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.

VEGF and FGF2 Improve Revascularization, Survival, and Oocyte Quality of Cryopreserved, Subcutaneously-Transplanted Mouse Ovarian Tissues

This study was conducted to investigate the effect of the vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) on revascularization, survival, and oocyte quality of cryopreserved, subcutaneously-transplanted mouse ovarian tissue. Autologous subcutaneous transplantation of vitrified-thawed mouse ovarian tissues treated with (experimental group) or without (control group) VEGF and FGF2 was performed. After transplantation to the inguinal region for two or three weeks, graft survival, angiogenesis, follicle development, and oocyte quality were examined after gonadotropin administration. VEGF coupled with FGF2 (VEGF/FGF2) promoted revascularization and significantly increased the survival rate of subcutaneously-transplanted cryopreserved ovarian tissues compared with untreated controls. The two growth factors did not show long-term effects on the ovarian grafts. In contrast to the untreated ovarian grafts, active folliculogenesis was revealed as the number of follicles at various stages and of mature oocytes in antral follicles after gonadotropin administration were remarkably higher in the VEGF/FGF2-treated groups. Although the fertilization rate was similar between the VEGF/FGF2 and control groups, the oocyte quality was much better in the VEGF/FGF2-treated grafts as demonstrated by the higher ratio of blastocyst development. Introducing angiogenic factors, such as VEGF and FGF2, may be a promising strategy to improve revascularization, survival, and oocyte quality of cryopreserved, subcutaneously-transplanted mouse ovarian tissue.

Connexin 37 and 43 gene and protein expression and developmental competence of isolated ovine secondary follicles cultured in vitro after vitrification of ovarian tissue

Cryoinjuries caused by vitrification of tissues and organs lead to the loss of membrane proteins that mediate intercellular communications, such as connexins 37 (Cx37) and 43 (Cx43). Thus, the present study aimed to evaluate ovine Cx37 and Cx43 gene and protein expressions and developmental competence by in vitro-cultured secondary follicles retrieved from vitrified ovarian tissue. Ovarian fragments for the same ovary pair were distributed into six treatments: (1) fresh ovarian tissue (FOT); (2) vitrified ovarian tissue (VOT); (3) isolated follicles from fresh ovarian tissue (FIF); (4) isolated follicles from vitrified ovarian tissue; (5) isolated follicles from fresh ovarian tissue followed by in vitro culture (CFIF); (6) isolated follicles from vitrified ovarian tissue followed by in vitro culture (CVIF). In all treatments, Cx37 and Cx43 gene and protein expression patterns were evaluated by reverse transcription polymerase chain reaction and immunocytochemistry. In addition, secondary follicles were analyzed according to follicular integrity and growth, apoptosis, and cell proliferation. In vitro-cultured secondary follicles (CFIF and CVIF) were evaluated based on morphology (extruded follicles), antrum formation, and viability. The percentage of intact follicles was higher, whereas antrum formation, oocyte extrusion rate, and follicle viability were lower in CVIF than in CFIF treatment (P < 0.05). Terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphates nick end-labeling assay demonstrated that apoptosis was absent in FIF, whereas follicles from all other treatments showed positive labeling. Cell proliferation index was higher in isolated follicles from vitrified ovarian tissue and CVIF treatments than in follicles from FIF. Expression of Cx43 messenger RNA was lower in CVIF treatment when compared with follicles from all other treatments (P < 0.05). Follicle Cx37 messenger RNA levels did not show alterations in any treatment (P > 0.05). Cx37 and Cx43 immunolabeling was localized mainly on granulosa cells and oocytes, respectively. In conclusion, isolation of ovine secondary follicles could be done successfully after vitrification of ovarian tissue, and the basement membrane integrity remained intact after in vitro culture. Although the gene and protein expression of Cx37 did not change after vitrification of ovarian tissue, Cx43 turned out to be altered in secondary follicles after vitrification and in vitro culture.

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.

bFGF and VEGF improve the quality of vitrified-thawed human ovarian tissues after xenotransplantation to SCID mice

PURPOSE

The aim of this research is to study whether basic fibroblast growth factor (bFGF) alone or in combination with vascular endothelial growth factor (VEGF) could improve the quality of vitrified-thawed human ovarian tissue xenotransplanted to severe combined immune deficiency (SCID) mice.

METHODS

After collection and cryopreservation, thawed human ovarian tissue were cultured in vitro for 2 days and then xenografted to severe combined immune deficiency (SCID) mice for 7 days. The in vitro culture medium was separated into six groups, including (A) the blank control group, (B) the human recombinant bFGF (150 ng/ml) group, (C) the bFGF (150 ng/ml)+human recombinant VEGF (25 ng/ml) group, (D) bFGF (150 ng/ml)+VEGF (50 ng/ml) group, (E) bFGF (150 ng/ml)+ VEGF (75 ng/ml) group and (F) bFGF (150 ng/ml) + VEGF (100 ng/ml) group. In addition, eight pieces of thawed ovarian tissue were transplanted without in vitro culture, which serve as the fresh control group. The effect of transplantation was assessed by histological analysis, immunohistochemical staining for CD34, Ki-67, and AC-3 expression, and microvessel density (MVD).

RESULTS

There was no significant difference between the fresh and blank control group. Compared to the blank control group, the number of follicles, MVD, and rate of Ki-67-positive cells increased significantly in groups B, C, D, E, and F, while apoptosis decreased significantly. Compared to the bFGF treatment group, no significant difference appeared in group C, D, E, and F.

CONCLUSIONS

The administration of bFGF alone or in combination with VEGF improved the quality of postgraft human ovarian tissue, though VEGF, regardless of different concentrations, did not influence effect of bFGF.

Three dimensional in vitro culture of preantral follicles following slow-freezing and vitrification of mouse ovarian tissue

To evaluate the effects slow-freezing and vitrification on three dimensional in vitro culture of preantral follicles, ovaries of 12-14 days old female NMRI mice were isolated and randomly assigned to fresh control, slow-freezing and vitrification groups. Slow-freezing was performed using programmable freezer. Vitrification was carried out in a medium consisting of ethylene glycol (EG) and dimethyl sulphoxide (Me2SO) by needle immersion method. middle sized preantral follicles were mechanically isolated and cultured for 12 days in 0.7% sodium alginate gel. The follicles development and quantitative expression of oocyte specific genes (Bmp15, Gdf9, Fgf8) and the growth related genes (Igf1, Kit, Kit-l) were assessed after 1, 8 and 12 days of culture. Both cryopreserved groups showed reduction of follicular survival rates compared to the control group on days 8 and 12 of culture (P < 0.05). Antrum formation rates reduced in slow-freezing after 12 days of culture (P < 0.05). Evaluation of gene expression showed reduction of Bmp15, Gdf9, Fgf8, Kit and Kit-l during 12 days of culture (P < 0.05). Kit and Kit-l expression in slow-freezing group significantly reduced on day 8 of culture (p < 0.05). Igf1 expression was lower in slow-freezing group on 1st day of culture than vitrification and control groups (P < 0.05). Finally, intergroup comparison showed same expression pattern of genes after 12 days of culture. Thus, cryopreservation of mouse ovaries by both methods can preserve most developmental parameters and expression of maturation genes. However, vitrification is a better method for cryopreservation of mouse ovaries due to greater antrum formation and expression of growth related markers.

Comparison of oxidative status of mouse pre-antral follicles derived from vitrified whole ovarian tissue and vitrified pre-antral follicles in the presence of alpha lipoic acid

AIM

The main goal of this study was to compare developmental competence and oxidative status of vitrified-warmed pre-antral follicles (VPF) with pre-antral follicles derived from vitrified-warmed ovarian tissue (VOF) in the presence of alpha lipoic acid (ALA).

MATERIALS AND METHODS

Ovarian tissue and isolated pre-antral follicles were exposed to equilibration solution and then vitrification solution. After thawing of LN2 snap-frozen samples, pre-antral follicles were cultured with or without ALA for 12 days that followed by hCG-induced ovulation. MII oocytes were in vitro fertilized and embryo cleavage assessed. Reactive oxygen species (ROS) and total antioxidant capacity (TAC) levels of cultured pre-antral follicles were measured.

RESULTS

The rates of survival, antral-like cavity formation, MII oocytes, fertilization, 2-cell embryo and blastocyst development were higher in VPF compared to VOF. These rates were higher in ALA-supplemented groups in comparison to their respective groups. An increase and a decrease in ROS production and TAC levels were observed up to the 96 h during cultivation period, respectively. ROS level was lower in cultured VPF compared to VOF. In ALA-treated groups, ROS level decreased to reach comparable values of starting point and TAC levels increased after 24 h of culture and then remained constant.

CONCLUSION

Developmental outcomes showed vitrification of pre-antral follicles is more appropriate method than that of whole ovarian tissue. Moreover, it seems that inclusion of ALA improved in vitro development of pre-antral follicles in both vitrified and non-vitrified samples.

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.

Cryopreservation of oocytes and embryos

Two hundred years have passed since the first description of supercooled water by Gey-Lussac to the recently high survival rates of embryo and oocytes after vitrification. This review discusses important milestones that have made vitrification the method of choice for oocytes and embryos cryopreservation. We will go through the first cells ever to survive low temperature exposure in the beginning of the last century, the finding of glycerol in the late 1940s and the first mouse and bovine embryos freezing in the 1970s. During the 1980s, embryo vitrification began and the time since is a tribute to the development of oocytes vitrification. Standardization and an automatic vitrification procedure are currently under development. The next evolutionary step in oocyte and embryo cryopreservation will be preserving them in the dry state at room temperature, allowing home storage for future use a reality.

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.

Antiapoptotic agent sphingosine-1-phosphate protects vitrified murine ovarian grafts

Significant follicle loss from frozen ovarian grafts is unavoidable. The authors evaluated the protective effects of the antiapoptotic agent sphingosine-1-phosphate (S1P) on vitrified ovarian grafts. Three-week-old sexually immature female FVB mice were divided into 4 groups, fresh, control without S1P, 0.5 mmol/L S1P, and 2 mmol/L S1P. The ovaries were pretreated with S1P for 1 hour and then cryopreserved by modified vitrification. The frozen-thawed ovaries were autotransplanted under the back muscles of mice for 10 days. Expression of apoptosis-related genes encoding caspase 3 and c-Myc was analyzed in the vitrified ovaries and 10 days after transplantation using real-time quantitative polymerase chain reaction. To quantify the ovarian reserve, anti-Müllerian hormone (AMH) levels and follicles were measured in the 10-day vitrified ovarian grafts. Caspase 3 and c-Myc messenger RNA did not differ significantly in the 4 groups after vitrification but was significantly upregulated in the control group after transplantation. The AMH levels and primordial follicle pool were significantly higher in the S1P-treated groups than in the control group but lower than that in the fresh group. The S1P protects vitrified ovarian grafts from ischemic reperfusion injury rather than from vitrification-associated process.

Good thermally conducting material supports follicle morphologies of porcine ovaries cryopreserved with ultrarapid vitrification

Effects of supporting materials during vitrification procedure on the morphologies of preantral follicles of pig ovaries were assessed. Ovarian cortical sections of prepubertal pigs were randomly allocated to 5 groups. The sections were vitrified ultrarapidly with 5 different vitrification devices. The sections were put on 4 fine needles (Cryosupport), on a thin copper plate, or on a carbon graphite sheet or were sandwiched between copper plates or between carbon graphite sheets before cooling. The cooling and warming rates with the graphite sheets were significantly higher than those with the copper plates (P<0.05). A total of 3,064 follicles were analyzed following HE staining after vitrification with 5 different devices. The morphologies follicles vitrified on the Cryosupport or on the graphite sheet were well preserved compared with those vitrified on the copper plate or between copper plates (P<0.01). The morphologies of follicles vitrified between copper plates were mostly damaged (P<0.05). Taken together, good thermally conducting material supports follicle morphologies of ovaries cryopreserved with ultrarapid vitrification.

Production of live offspring from testicular tissue cryopreserved by vitrification procedures in Japanese quail (Coturnix japonica)

Cryopreservation of testicular tissue can be used for ex situ conservation of male germplasm of avian species. The possibility of using vitrification and transplantation of testicular tissue for fertility preservation and recovery was tested in Japanese quail. Testes were removed from 1-wk-old Japanese quail; transfixed on acupuncture needles; equilibrated with dimethyl sulphoxide, ethylene glycol, and sucrose; plunged into liquid nitrogen; and stored in 2-ml straws. Cryopreserved tissue was warmed in sucrose solution at room temperature or at 40°C. Fresh and cryopreserved tissue were transplanted subcutaneously into castrated, 1-wk-old recipients. Twenty of 21 recipients survived the surgery, and 18 had viable transplants at maturity, with no difference in transplantation success between fresh and cryopreserved tissue. Fluid extrusion from 11 of the transplants was collected and inseminated surgically into the magnum of 22 quail hens, and 10 inseminations included foam from the proctodeal gland of the same recipients. Egg production in the 2 wk after insemination was reduced, and none of the hens inseminated with foam produced fertile eggs. Five hens inseminated without foam produced a total of eight live offspring; four of these hens had been inseminated with fluid extrusion from cryopreserved tissue. Histological examination showed spermatogenesis in the transplants, and the tubules, lumens, and epithelium of the seminiferous tubules were of comparable size to those of testicular tissue from intact males. These results demonstrate that testicular tissue of Japanese quail can be preserved using vitrification procedures and recovered through transplantation.

Restoring fertility after ovarian tissue cryopreservation: a half century of research

Tissue transplantation and in vitro ovarian follicle culture have been investigated as alternative techniques to restore fertility in young women who are facing fertility-threatening diseases or treatments following ovarian tissue cryopreservation. Although transplants of fresh or frozen ovarian tissue have successfully yielded healthy live births in different species including humans, the risks of reintroducing cancer cells back into the patient, post treatment, have limited its clinical purpose. The in vitro ovarian follicle culture minimizes these risks and provides a way to harvest more mature oocytes, however its clinical translation has yet to be determined. Not only is it possible for tissue cryopreservation to safeguard fertility in cancer patients, this technique also allows the maintenance of germplasm banks for animals of high commercial value or for those animals that are at risk of extinction. Given the importance of managing female genetic material, this paper reviews the progress of the methods used to preserve and restore female fertility in different species to demonstrate the results obtained in the past 50 years of research, the current achievements and the future directions on this field.

The use of a metal container for vitrification of mouse ovaries, as a clinical grade model for human ovarian tissue cryopreservation, after different times and temperatures of transport

PURPOSE

Cryopreservation of ovarian tissue is paramount for fertility preservation, with important clinical applications, especially for women suffering from an oncological condition. Several cryopreservation methodologies have been tried in search of better outcomes, especially in terms of primor-dial and primary follicles integrity post-cryopreservation. Vitrification has successfully been applied to ovarian tissue using different carriers for tissue exposure to the liquid nitrogen (LN2).

METHODS

We developed an enclosed metal vessel, which has the advantage of a faster heat transfer, when in contact with LN2 avoiding at the same time, the direct contact with tissue. Additionally, we assessed the effect of different times and temperatures of transport between the collection of mouse ovaries and the beginning of cryopreservation, on follicular morphology after vitrification.

RESULTS

Our results suggest that 37 °C and R.T. help to maintain normal primordial and primary follicle morphology for up to 4 hrs after collection and beginning of vitrification in a metal container.

CONCLUSION

These data show that the metal container is an appropriate carrier for mouse ovary vitrification. The rate of morphologically normal primordial follicles up to 4 hrs.