Evaluation of the effect of human testicular cell conditioned media on the in vitro development of follicles from cryopreserved human ovarian cortical pieces. A potential approach for fertility preservation for cancer patients

If in vitro culture conditions could be improved, in vitro growth of cryopreserved ovarian tissue and isolated follicles could become an alternative to ovarian tissue transplantation. This study evaluated two cryopreservation methods, slow cooling and vitrification, and two in vitro culture methods, to determine their effect on the in vitro growth of human ovarian follicles. After warming, the OT pieces (1 × 10 × 3 mm) were cultured in either routine culture medium (DMEM), or DMEM supplemented 50:50 with media previously used for human testicular cell culture (hTCCM) to serve as a source of growth factors. Several parameters were evaluated during culture including follicle recruitment, growth, morphology, diameter, hormone production, and gene expressions (PTEN, BMP-15, PDGF, GDF-9, and GAPDH). The follicular morphology and hormonal secretion were comparable for both cryopreservation methods and both culture methods (P > 0.05). Follicle recruitment was accelerated in the vitrified group, in the presence of hTCCM (P > 0.05). After 7 days of culture, the follicle diameter was greater in the slow/hTCCM compared to the vitrification DMEM group. Similarly only one gene expression profile, BMP-15, in the slow/hTCCM differed significantly from another treatment group (Vit DMEM). At the end of culture (over 21 days), three immature, low-quality oocytes were the achievement. In conclusion, a very quick and easy vitrification protocol gave comparable results to the slow cooling method. We also established that the laboriously prepared hTCCM supplement did not benefit the outcomes. Further work is needed before in vitro maturation of cryopreserved ovarian cortical pieces can be used clinically.

Orthotopic Transplantation of Native and Cryopreserved Ovarian Tissue in Day-Old Geese

As an alternative method for preserving female genetic material, the cryopreservation and orthotopic transplantation of day-old gonadal tissue have become well-developed techniques in a few poultry species. The aim of the present study was to apply these methods for the first time to domestic geese. Cryopreservation was accomplished using the previously developed vitrification technique. Native and frozen/thawed White Hungarian geese ovarian tissue was transplanted onto Grey Landes geese recipients. Both donors and recipients were less than 24 h old. The surgical protocol previously used in chickens needed to be modified regarding anaesthesia; ketamine, xylazine, and midazolam were administered partly intramuscularly and partly intravenously. After sexual maturation, the Grey Landes recipients were paired with White Hungarian ganders, and eggs were collected and hatched individually. The origin of the offspring was determined by phenotype- and microsatellite markers. Donor-derived offspring were obtained from native and frozen/thawed ovarian tissue transplantation, which had not been published earlier. The ratio of donor-derived progeny producing layers was 40% and 58% in native and frozen/thawed gonadal tissue transplantation, respectively. The highest rate of donor-originated progeny was 78.9%. Consequently, gonadal tissue transplantation appears to be a suitable method for preserving female genetic material in domestic geese; the technique is already implemented in Hungarian gene bank practice.

Evaluation of Cryopreservation of Bovine Ovarian Tissue by Analysis of Reactive Species of Oxygen, Toxicity, Morphometry, and Morphology

Ovarian tissue cryopreservation has been widely investigated for preserving female fertility. In the present study, we aimed to compare the effects of three concentrations (1, 1.5, and 3 M) of dimethylsulfoxide (DMSO) on the vitrification of ovarian tissue. The ovarian cortex was divided into control and vitrified groups: (i) 1 M-DMSO, (ii) 1.5 M-DMSO, and (iii) 3 M-DMSO. Follicles from all fragments were analyzed for DMSO-induced deleterious effects, morphological and morphometric aspects, and concentration of reactive oxygen species. Additionally, the fragments were cultured to assess the integrity and return of follicular development post-vitrification. All DMSO concentrations resulted in a higher percentage of degenerated preantral follicles than before the cryopreservation process. After vitrification, the cryopreserved ovarian fragments showed similar percentages of intact follicles; however, the 3 M DMSO concentration differed from the control. Analyzing free radical production, we found that the 3 M DMSO concentration had higher levels of oxidative stress than the lower DMSO. After in vitro cultivation of the vitrified/warmed fragments, the 1 M DMSO concentration exhibited higher percentages of morphologically intact follicles than the other concentrations. Therefore, we suggest that bovine preantral follicles can be cryopreserved in situ with greater efficiency in 1 M DMSO.

Human ovarian cryopreservation: vitrification versus slow freezing from histology to gene expression

Cryopreservation of ovarian tissue is one of the strategies offered to girls and women needing gonadotoxic treatment to preserve their fertility. The reference method to cryopreserve is slow freezing; vitrification is an alternative method. The aim was to evaluate which of the two is the best method for human ovarian tissue cryopreservation. Each ovary was divided into three groups: (i) fresh; (ii) slow freezing; and (iii) vitrification. An evaluation of the follicular density, quality and the expression six genes (CYP11A, STAR, GDF9, ZP3, CDK2, CDKN1A) were performed. We observed no significant difference in follicular density within these three groups. Slow freezing altered the primordial follicles compared to the fresh tissue (31.8% vs 55.9%, p = 0.046). The expression of genes involved in steroidogenesis varied after cryopreservation compared to the fresh group; CYP11A was under-expressed in slow freezing group (p = 0.01), STAR was under-expressed in the vitrification group (p = 0.01). Regarding the expression of genes involved in cell cycle regulation, CDKN1A was significantly under-expressed in both freezing groups (slow freezing: p = 0.0008; vitrification: p = 0.03). Vitrification had no effect on the histological quality of the follicles at any stage of development compared to fresh tissue. There was no significant difference in gene expression between the two techniques.

Influence of Intracellular Cryoprotectants on the Conservation of Dermal Somatic Tissues Derived from Antillean Manatees (Trichechus manatus manatus Linnaeus, 1758)

Cryopreservation of somatic tissue has been studied as a tool for the knowledge and conservation of endangered species, such as Antillean manatees. The use of vitrification protocols is an important step in the establishment of biological banks. To decrease the damage caused by this technique, a reduction in the concentration of cryoprotectants has been proposed. Therefore, we aimed to evaluate combinations and concentrations of intracellular cryoprotectants for the conservation of somatic tissues derived from Antillean manatees. Dulbecco's modified Eagle's medium, F-12 composed of 10% fetal bovine serum and 0.25 M sucrose, was supplemented with 3.0 M ethylene glycol (EG) plus 3.0 M dimethyl sulfoxide (DMSO), or 1.5 M EG plus 1.5 M DMSO or 3.0 M EG or 3.0 M DMSO, to produce four solutions for solid-surface vitrification. Noncryopreserved tissues were used as the controls. After warming, tissues derived from four Antillean manatees were evaluated for ultrastructure, histology, and in vitro culture. No differences were observed among the cryopreserved and noncryopreserved tissues in terms of ultrastructure. The dermis thickness of the cryopreserved fragments in solutions containing 3.0 M EG plus 3.0 M DMSO, 3.0 M EG, and 3.0 DMSO was similar to that of the control. Moreover, cryopreservation with 3.0 M EG plus 3.0 M DMSO maintained tissue proliferative capacity potential evaluated by quantification of nucleolar organizing regions. Nevertheless, none of the cryopreserved fragments were able to maintain the number of fibroblasts and the collagen percentage as compared with that of the noncryopreserved fragments. Also, none of the cryopreserved fragments in the different solutions were able to produce cells in vitro. In summary, even reducing the concentration of intracellular cryoprotectants as well as their association did not guarantee the maintenance of cells after in vitro culture. Further studies are needed to optimize the cryopreservation protocols in Antillean manatee somatic tissues.

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.

Cryopreservation of African painted dog (Lycaon pictus) ovarian tissue

Development of techniques for the preservation and use of gonadal tissues are increasingly needed for the genetic management of the endangered African painted dog (Lycaon pictus). Here we evaluated two cryopreservation techniques for ovarian tissue (2 × 2 × 1 mm3 fragments, n = 11 individuals): needle immersed vitrification (NIV), with equilibration in a 7.5% dimethyl sulfoxide (DMSO) and 7.5% ethylene glycol (EG) solution, and vitrification in a 15% DMSO, 15% EG, and 0.5 M sucrose solution, and slow freezing in cryovials with either the equilibration (SF-E) or vitrification (SF-V) solutions. Following warming, tissues were either fixed and embedded for evaluation of density of morphologically normal follicles, semi-quantitative scoring of stromal cell preservation, and apoptotic index (TUNEL stain), and/or flash-frozen for expression of proliferation (PCNA), apoptosis (CASP3, BCL2), or oxidative stress (GPX3, SOD1, SOD2) pathway genes (n = 4). Needle immersed vitrification maintained higher density of morphologically normal follicles compared to the slow freezing protocols applied (p < 0.05), with no significant changes in expression of select genes among treatment groups. A slight increase in apoptotic index was observed in all cryopreservation groups, but only reached significance in SF-E compared with fresh tissue controls (p < 0.05). Future research should be dedicated to developing improved methods for ovarian tissue culture in the species, both as a means to evaluate the efficacy of tissue cryopreservation techniques and for the production of viable oocytes from banked ovarian tissue in the endangered African painted dog.

Vitrification versus slow freezing of human ovarian tissue: a systematic review and meta-analysis of histological outcomes

A systematic review and meta-analysis of pertinent literature published from 2006 to January 2022 were conducted to study and compare vitrification and slow freezing, the two prominent methods of ovarian tissue cryopreservation. The primary outcome measures for this study were (1) proportion of intact primordial follicles, (2) proportion of intact stromal cells, (3) proportion of DNA fragmentation in primordial follicles, and (4) mean primordial follicle density. This meta-analysis of 19 studies revealed a significantly greater proportion of intact stromal cells in vitrified tissue versus slow-frozen tissue. No significant differences upon pooled analyses were observed between the two cryopreservation methods with respect to the proportion of intact primordial follicles, proportion of DNA fragmentation, or mean primordial follicle density. Due to differences seen in stromal cell viability, vitrification may be a preferred option to preserve histology of tissue. However, more work should be done to compare the two freezing techniques with less heterogeneity caused by patients, samples, and protocols.

The effect of high-throughput vitrification of human ovarian cortex tissue on follicular viability: a promising alternative to conventional slow freezing?

BACKGROUND

The standard procedure most frequently used for ovarian tissue cryopreservation (OTC) is slow freezing, while vitrification has been proposed as promising alternative and has built an impressive catalog of success in fertility laboratories regarding cryopreservation of oocytes and embryos.

METHODS

We developed and evaluated a high-throughput protocol for vitrification of human ovarian tissue suitable for clinical processing. Follicular viability was assessed via calcein staining prior and after cryopreservation analyzing ovarian tissue of a cohort of 30 patients.

RESULTS

We found no significant differences regarding follicular viability between slow frozen and vitrified cortex tissue samples 24 h after thawing and rapid warming. Follicular viability of thawed and rapid warmed samples was not significantly different in comparison to fresh samples, indicating high proportions of follicular survival rates with both methods.

CONCLUSIONS

High-throughput vitrification is a promising option in a clinical setting. More research is required to determine the status of other tissue-specific quality indicators potentially influencing on autotransplantation.

Vitrification of the ovarian tissue in sturgeons

The aim of this study was to test whether vitrification of sterlet Acipenser ruthenus and Russian sturgeon Acipenser gueldenstaedtii ovarian tissue through needle-immersed vitrification (NIV) is an efficient strategy for the preservation of oogonia (OOG) in order to supplement the current conservation efforts for these endangered fish species. Histological analyses of the gonads displayed that the ovaries of both species were immature and contained predominantly OOG and primary oocytes. The germline origin of these cells was verified by localization of the vasa protein through immunocytochemistry. NIV protocol was optimized by testing different equilibration (ES) and vitrification solutions (VS) containing various concentrations of dimethyl sulfoxide (Me₂SO), propylene glycol (PG) or methanol (MeOH). In sterlet, the highest average viability (55.7 ± 11.5%) was obtained by using a combination of 1.5 M PG and 1.5 M Me₂SO in the ES, and 1.5 M MeOH and 5.5 M Me₂SO in the VS. In Russian sturgeon, the highest average viability (49.4 ± 17.1%) was obtained by using a combination of 1.5 M MeOH and 1.5 M Me₂SO in the ES, and 3 M PG and 3 M Me₂SO in the VS. To test whether vitrified/warmed OOG are functional, we have conducted an intra-specific transplantation assay to verify whether transplanted sterlet OOG will colonize the gonads of recipient fish. Fluorescently labelled cells were detected within recipient gonads at 2 and 3 months post-fertilization (mpf). Colonization rates of vitrified/warmed OOG (70% at 2 mpf and 61% at 3 mpf) were similar to those of fresh OOG (80% at 2 mpf and 70% at 3 mpf). This study has demonstrated that vitrification of ovarian tissue is an effective method for the preservation of OOG, and that the vitrified/warmed cells are functional and are able to colonize recipient gonads after transplantation similarly to the fresh cells. Since the vitrification procedure displayed in this study is simple and does not require complex and expensive laboratory equipment, it can be readily applied in field conditions, and therefore it can be invaluable for the conservation efforts of the critically endangered sturgeon species. However, care needs to be taken that despite the research conducted so far, donor-derived progeny was not yet obtained in sturgeons.

Influence of Vitrification Device, Warming Protocol, and Subsequent In Vitro Culture on Structural Integrity of Testicular Fragments from Adult Domestic Cats

The objective of the study was to evaluate the integrity of cat testicular tissues after vitrification with different devices followed by different warming conditions. The influence of vitro culture for 24 hours after warming also was examined. Testicular tissues from adult domestic cats were dissected in small fragments that were vitrified using Cryotop^® or threaded on fine needles, warmed (directly at 37°C or with a preliminary 10 seconds exposure to 50°C), and/or cultured in vitro for an additional 24 hours. For each treatment group, tissues were assessed based on histology, apoptosis, and sperm DNA integrity. Results showed that fragments of testicular tissues were efficiently cryopreserved (maintaining the quality of all cell types) with vitrification with Cryotop followed by direct warming at 37°C, and additional culture of 24 hours at 38.5°C. These encouraging results are paving the road to optimize preservation protocols and use them for systematic banking of tissues from genetically valuable felids.

Influence of different warming temperatures on the vitrified testicular fragments from pre-pubertal cat

Testicular vitrification is an alternative to preserve the genetic material of pre-pubertal animals. However, there are few studies on post-vitrification warming. Hence, the aim was to compare the influence of different warming temperatures on vitrified testicular fragments from pre-pubertal cats. The testicles were fragmented and divided into a control group (non-vitrified) and vitrified, using an association between dimethylsulphoxide and glycerol. The vitrified fragments were warmed at 50, 55 and 60°C/5 s. Morphological and morphometric evaluations were carried out using classical histology. Afterwards, the mitochondrial activity was evaluated using Rhodamine 123. The data were expressed in mean and standard error. The differences were considered significant when p < .05. In the histomorphological analysis, the testicular fragment presented seminiferous tubules with poorly developed germinal epithelium, compatible with pre-pubertal animals. The group warmed at 50°C presented similar to the control regarding the maintenance of the integrity of the tubules and cells, without stromal rupture and lamina propria alteration, as well as regarding the maintenance of the junctions between the cells. The group warmed at 55°C showed reduction of the cell junctions, and the one warmed at 60°C had increased detachment of the basement membrane (p < .05). The warming caused a reduction in the tubular diameter inversely proportional and progressive to the increase in temperature, with the highest diameter in the control group and the lowest in the 60°C group. The control group showed a lower incidence of Rhodamine 123, followed in ascending order of the warmings at 55 and 60°C. The higher mitochondrial activity was obtained with 50°C, showing an increase of the metabolic cell function at this temperature. It was concluded that the testicular fragment of pre-pubertal cats presents a better preserved morphology, morphometry and viability when warmed at 50°C.

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.

Cellular and Molecular Impact of Vitrification Versus Slow Freezing on Ovarian Tissue

Objective: To evaluate a vitrification protocol from histology to gene expression to slow freezing. Methods: Ovaries from 12 prepubertal ewes. The same ovary was cut into fragments, studied fresh, frozen, and vitrified. Follicle morphology by hematoxylin-eosin-safran staining, vitality by Trypan Blue, and apoptosis by marking cleaved caspase-3 were studied. The expression of gene: anti-Müllerian hormone (AMH), cytochrome p450 family 11 subfamily A member 1 (CYP11A), and steroidogenic acute regulatory protein (STAR; granulosa cells); growth differentiation factor 9 (GDF9) and zona pellucida glycoprotein 3 (ZP3; oocytes); and cyclin D2 (CCND2) and cyclin-dependent kinase inhibitor 1A (CDKN1A; cell cycle regulation), was evaluated by reverse transcription quantitative polymerase chain reaction. Results: The slow freezing protocol had a significant negative impact on intact primordial follicles compared with fresh tissue (37.6% vs. 62.5%, p = 0.003). More intact follicles after vitrification were observed compared with slow freezing (p = 0.037). The apoptotic primordial follicles were similar after slow freezing and vitrification (12.6% vs. 13.9%). Concerning granulosa cell genes, slow freezing led to a trend toward overexpression of AMH messenger RNA (mRNA; p = 0.07); while vitrification led to a significant overexpression of CYP11A mRNA (p = 0.003), and a trend toward an overexpression of STAR mRNA (p = 0.06). Concerning oocyte genes, both techniques did not lead to a difference of GDF9 and ZP3 mRNA. Concerning cell cycle genes, slow freezing led to a significant underexpression of CCND2 (p = 0.04); while vitrification did not lead to a difference for CCND2 and CDKN1A mRNA. Conclusion: Vitrification preserved follicular morphology better than slow freezing and led to gene overexpressed, while slow freezing led to gene underexpressed. Impact statement The preservation of female fertility and in particular the cryopreservation of ovarian tissue (OT) is a major public health issue aimed at improving the quality of life of patients after gonadotoxic treatments. The use of slow freezing of this OT, which is the reference technique, is not optimal due to tissue alteration. The alternative would be vitrification. This study compares these two techniques. We have highlighted that vitrification preserved follicular morphology better than slow freezing and led to gene overexpressed, while slow freezing led to gene underexpressed.

Cryopreservation of grey wolf (Canis lupus) testicular tissue

Development of genomic preservation technologies for canids, especially for seasonally breeding species like the grey wolf (Canis lupus), is needed in advance of growing species conservation concerns. Here, we evaluated the efficacy of two cryopreservation protocols - needle immersion vitrification (NIV) and slow freezing (SF) on grey wolf (n = 7) testicular tissue morphology. NIV samples were equilibrated in a 7.5% v/v dimethyl sulfoxide (DMSO or Me2SO) + 7.5% ethylene glycol (EG) solution in minimum essential medium with 20% FBS for 10 min at 4 °C, then exposed to 15% DMSO + 15% EG + 0.5 M sucrose for 10 min at 4 °C before plunging into liquid nitrogen. For slow freezing, we assessed two cryoprotectant (CPA) strategies, DMSO, 15% v/v alone (SF-D) or 7.5% EG + 7.5% DMSO (SF-ED). Following thawing, there were no significant differences in seminiferous tubule area among treatment groups, although all cryopreserved tissues displayed reduced tubule size compared with fresh controls and increased apoptosis, the latter reaching significance for SF-D treated tissues. Slow freezing improved maintenance of testis architecture, with minimal detachment of seminiferous tubule basement membranes post-thaw. Spermatogonia densities were reduced in NIV tissues compared with fresh, with no differences in spermatocyte, spermatid, or Sertoli cell counts, or germ cell marker DDX4⁺ cell densities among groups. In sum, we conclude that slow freezing better maintained morphology of cryopreserved testicular tissues compared with needle vitrification with 15% each DMSO and EG and 0.5 M sucrose, and that DMSO + EG combination SF supports cell viability. This represents a first step in the development of male gonadal tissue preservation strategies for the grey wolf.

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.

Improvement of the application of gonadal tissue allotransplantation in the in vitro conservation of chicken genetic lines

In avian species, the surgical technique for ovarian allotransplantation has been developed for domestic chickens; however, not all genotypes can be effectively used as recipients. The aims of the present study were to ascertain donor/recipient combinations for production of offspring from frozen/thawed ovarian tissues. The development of the technique is important because domestic chicken offspring have only been produced from fresh (never frozen) ovarian and from frozen-thawed testicular tissues. Information obtained from evaluating genetic differences of intensively selected lines in which there was successful pairing was compared in the indigenous breeds. Results indicate donor/recipient combinations were created which could be effectively used for gonadal tissue allotransplantations. Gonadal tissues of Yellow, Speckled and Partridge-color Hungarian, Black and Speckled Transylvanian Naked Neck chicken breeds were allotransplanted into White Leghorn or Novogen White breeds for offspring production. The gonadal tissues of these indigenous breeds were cryopreserved using vitrification procedures. There was successful allografting of frozen/thawed gonadal tissues at a rate between 20 % and 100 % depending on the genotype and sex, and histological examination and microsatellite marker analysis provided evidence that the donor ovarian and testicular tissues had the capacity for producing gametes. The hens of Speckled Transylvanian Naked Neck/White Leghorn combination using frozen/thawed ovarian tissues were produced for progeny tests. Of these, 58 % produced eggs and 9.1 % produced donor-derived offspring, based on data for both feather color markers and genetic analysis.

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.

Morphological, biochemical and functional studies to evaluate bovine oocyte vitrification

The aim of the present study was to evaluate the effect of vitrification on morphological, biochemical and functional parameters of matured bovine oocytes at different recovery times. To this end, matured bovine oocytes were vitrified using the Cryotech® kit (a minimum-volume system) and then incubated in maturation medium for different post-warming durations (0 h, 3 h or 21 h). Morphology, viability and biochemical parameters were assessed at each time point mentioned above and the recovery of the metaphase plate was analyzed at 2 h, 3 h and 4 h post-warming. The vitrification-warming process did not affect the viability or morphology of oocytes at any time point. However, the recovery of the metaphase plate occurred mostly between 3 and 4 h rather than at 2 h after warming (P < 0.05). Both control and vitrified-warmed oocytes showed changes in cytosolic oxidative activity, quantification of active mitochondria, reactive oxygen species (ROS) levels and redox status at the different time points studied (P < 0.05). However, differences between control and vitrified-warmed oocytes were found only in the quantification of active mitochondria and ROS production (P < 0.05). Finally, in vitro fertilization and embryo culture were carried out as functional studies to establish whether vitrification-warming affected oocyte competence, and a significant decrease was found both in the cleavage rate and embryo development (P < 0.05). We concluded that major improvements in oocyte vitrification, at list with Cryotech® kit, are still needed to avoid variations in oocyte metabolism which could contribute to the reduction in the developmental competence of bovine oocytes.

Preservation of zebrafish genetic resources through testis cryopreservation and spermatogonia transplantation

Zebrafish is one of the most commonly used model organisms in biomedical, developmental and genetic research. The production of several thousands of transgenic lines is leading to difficulties in maintaining valuable genetic resources as cryopreservation protocols for eggs and embryos are not yet developed. In this study, we utilized testis cryopreservation (through both slow-rate freezing and vitrification) and spermatogonia transplantation as effective methods for long-term storage and line reconstitution in zebrafish. During freezing, utilization of 1.3 M of dimethyl sulfoxide (Me2SO) displayed the highest spermatogonia viability (~60%), while sugar and protein supplementation had no effects. Needle-immersed vitrification also yielded high spermatogonia viability rates (~50%). Both optimal slow-rate freezing and vitrification protocols proved to be reproducible in six tested zebrafish lines after displaying viability rates of >50% in all lines. Both fresh and cryopreserved spermatogonia retained their ability to colonize the recipient gonads after intraperitoneal transplantation of vasa::egfp and actb:yfp spermatogonia into wild-type AB recipient larvae. Colonization rate was significantly higher in dnd-morpholino sterilized recipients than in non-sterilized recipients. Lastly, wild-type recipients produced donor-derived sperm and donor-derived offspring through natural spawning. The method demonstrated in this study can be used for long-term storage of valuable zebrafish genetic resources and for reconstitution of whole zebrafish lines which will greatly improve the current preservation practices.

Cryopreservation of Human Ovarian Tissue: A Review

BACKGROUND

Cryopreservation of human ovarian tissue has been increasingly applied worldwide to safeguard fertility in cancer patients, notably in young girls and women who cannot delay the onset of their treatment. Moreover, it has been proposed to patients with benign pathologies with a risk of premature ovarian insufficiency. So far, more than 130 live births have been reported after transplantation of cryopreserved ovarian tissue, and almost all patients recovered their ovarian function after tissue reimplantation.

SUMMARY

This review aims to summarize the recent results described in the literature regarding human ovarian tissue cryopreservation in terms of methods and main results obtained so far. To cryopreserve human ovarian tissue, most studies describe a slow freezing/rapid thawing protocol, which is usually an adaptation of a protocol developed for sheep ovarian tissue. Since freezing has been shown to have a deleterious effect on ovarian stroma and granulosa cells, various research groups have been vitrifying ovarian tissue. Despite promising results, only 2 babies have been born after transplantation of vitrified/warmed ovarian tissue. Optimization of both cryopreservation strategies as well as thawing/warming protocols is therefore necessary to improve the survival of follicles in cryopreserved ovarian tissue.

KEY MESSAGES

Human ovarian tissue cryopreservation has been successfully applied worldwide to preserve fertility in patients with malignant or nonmalignant pathologies that have a detrimental effect on fertility. Human ovarian tissue cryopreservation could also be applied as an alternative to postpone pregnancy or menopause in healthy women. Slow freezing and vitrification procedures have been applied to cryopreserve human ovarian tissue, but both alternatives require optimization.

Cryopreservation and transplantation of common carp spermatogonia

Common carp (Cyprinus carpio) is one of the most cultured fish species over the world with many different breeds and plenty of published protocols for sperm cryopreservation. However, data regarding preservation of gonadal tissue and surrogate production is still missing. A protocol for freezing common carp spermatogonia was developed through varying different factors along a set of serial subsequent experiments. Among the six cryoprotectants tested, the best survival was achieved with dimethyl sulfoxide (Me₂SO). In the next experiment, a wide range of cooling rates (0.5–10°C/min) and different concentrations of Me₂SO were tested resulting in the highest survival achieved using 2 M Me₂SO and cooling rate of -1°C/min. When testing different tissue sizes and incubation times in the cryomedia, the highest viability was observed when incubating 100 mg tissue fragments for 30 min. Finally, sugar supplementation did not yield significant differences. When testing different equilibration (ES) and vitrification solutions (VS) used for needle-immersed vitrification, no significant differences were observed between the tested groups. Additionally, varied exposure time to VS did not improve the vitrification outcome where the viability was 4-fold lower than that of freezing. The functionality of cryopreserved cells was tested by interspecific transplantation into sterilized goldfish recipients. The exogenous origin of the germ cells in gonads of goldfish recipient was confirmed by molecular markers and incorporation rate was over 40% at 3 months post-transplantation. Results of this study can serve for long-term preservation of germplasm in carp which can be recovered in a surrogate recipient.

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.

Vitrification of canine ovarian tissues with polyvinylpyrrolidone preserves the survival and developmental capacity of primordial follicles

Ovarian tissue cryopreservation combined with immature follicle development can preserve female fertility in wildlife, regardless of age or reproductive timing. To investigate the effects of different cryopreservation methods and cryoprotectants on follicular survival and developmental capacity, ovarian cortical pieces from 15 dogs were cryopreserved by slow freezing or vitrification with different additional cryoprotectants as follows: dimethyl sulfoxide (DMSO), polyvinylpyrrolidone (PVP), combined DMSO and PVP (each at half the concentration of when used independently), or none (control). Cryopreserved ovarian tissues were evaluated by neutral red staining, histology, and xenotransplantation assays. Among cryopreservation conditions tested, vitrification with combined DMSO and PVP significantly improved the maintenance of follicular morphology compared to that in control. Furthermore, ovarian tissues vitrified using this condition maintained follicle morphology and developmental capacity 9 weeks after grafting, as shown by an increased percentage of primary and secondary follicles and a significant decrease in the transition stage from primordial to primary stage follicles 5 and 9 weeks after grafting. In contrast, slow freezing and control groups lost intact follicles by 5 weeks after grafting. The described cryopreservation techniques, which preserve canine follicle development, will build the foundation of ovarian tissue cryopreservation to preserve female fertility in wild canids.

The Role of Reproductive Sciences in the Preservation and Breeding of Commercial and Threatened Teleost Fishes

The teleost fishes are the largest and most diverse vertebrate group, accounting for nearly half of all known vertebrate species. Teleost fish exhibit greater species diversity than any other group of vertebrates and this is reflected in the unique variety of different reproductive strategies displayed by fish. Fish have always been an important resource for humans worldwide, especially as food. While wild capture fisheries have historically been the main source of fish, the farming of fish (aquaculture) is increasingly becoming the more dominant source of food fish, and is predicted to account for 60% of total global fish production by 2030.Fishes are increasingly threatened by a wide range of anthropogenic impacts, including loss of habitat, pollution, invasive species and over-exploitation. In addition, climate change, especially the consequences of global warming, can impact fish at all levels of biological organization from the individual to the population level, influencing both physiological and ecological processes in a variety of direct and indirect ways. As such, there is an urgent need to protect and conserve the huge genetic diversity offered by this diverse vertebrate group, not just as a source of genes for contemporary breeding and for protection against the consequences of climate change and disease, but also as part of our national heritage. While the cryopreservation of reproductive cells is a means of achieving these objectives, currently only fish sperm can be successfully frozen. Due to their large size, large yolk compartment, low membrane permeability and high chilling sensitivity, successful and reproducible protocols for the cryopreservation of fish oocytes and embryos still remains elusive. However, significant advances have been made in the cryopreservation of primordial germ cells as an alternative means of conserving both paternal and maternal genomes. Although more research needs to be carried out on how these cells can be optimally applied to emerging reproductive technologies, including transplantation techniques and surrogate broodstock technologies, the successful cryopreservation of fish germ cells, and the establishment of genetic resource banks, offers the possibility of both conserving and restoring threatened species. Further, current and future conservation efforts need to consider the impact of climate change in both in situ conservation and reintroduction efforts.In conclusion, it is anticipated that the successful cryopreservation of fish germplasm will result in a range of economic, ecological and societal benefits. In partnership with emerging assisted reproductive technologies, the successful cryopreservation of fish germplasm will lead to more efficient reproduction in aquaculture, assist selective breeding programmes, and be of crucial importance to future species conservation actions.

Influence of warming and reanimation conditions on seminiferous tubule morphology, mitochondrial activity, and cell composition of vitrified testicular tissues in the domestic cat model

Understanding critical roles of warming and reanimation is critical to improve the survival of vitrified testicular tissue in domestic cats. The objective was to study structural and functional properties of testicular tissues from prepubertal domestic cats after standard vitrification followed by two warming protocols (directly at 37°C or with a 5-second pre-exposure to 50°C) and three reanimation time points (immediately, 24 h and 5 days post-warming). In Experiment 1, tissues were evaluated for histo-morphology and mitochondrial activity immediately or 24 h after warming protocols. In Experiment 2, cell viability, DNA fragmentation, and germ cell composition were assessed immediately, 24 h, or 5 days after optimal warming. Preservation of seminiferous tubule structure was better using warming at 50°C for five seconds, and survival of somatic as well as germinal cells was higher compared to direct warming at 37°C for one minute. Short term in vitro culture (for reanimation) also proved that cellular composition and functionality were better preserved when warmed for a short time at 50°C. Collective data showed that short warming at 50°C led to better quality of seminiferous tubule structure and cell composition after vitrification and short-term culture. In addition, data suggest clear directions to further understand and optimize testicular tissue survival after fertility preservation procedures.

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.

Stroma cell-derived factor 1 and connexins (37 and 43) are preserved after vitrification and in vitro culture of goat ovarian cortex

This study aimed to evaluate the follicular morphology and development (follicular activation, cell proliferation, and hormone production), as well as the distribution pattern of Connexins 37 and 43 and SDF-1α after vitrification and in vitro culture of goat ovarian tissue. The study involved four experimental groups: fresh control, vitrified control, fresh culture and vitrified culture. The ovarian fragments were vitrified by a solid surface technique using the Ovarian Tissue Cryosystem and subsequently in vitro cultured for 7 days. The percentage of normal preantral follicles was similar between vitrified control and vitrified culture. However, both vitrified control and vitrified culture treatments showed a significant reduction of morphologically normal follicles in comparison to fresh control. A higher percentage of developing follicles (transition, primary and secondary) was observed in both fresh culture and vitrified culture treatments. Progesterone and estradiol production decreased (P < 0.05) during in vitro culture. SDF-1α and Cx37 proteins were detected in oocytes and granulosa cells from all the treatments. However, in vitrified cultured tissue, only granulosa cells were labeled with Cx37. Connexin 43 was detected in the granulosa, theca cells and zona pellucida in all the treatments. In conclusion, in vitro culture of vitrified goat ovarian cortex was able to promote follicle survival and did not alter the expression of SDF-1α and 43. However, the expression of Cx 37 was modified after in vitro culture of vitrified tissue.

GDF9-β promotes folliculogenesis in sheep ovarian transplantation onto the chick embryo chorioallantoic membrane (CAM) in cryopreservation programs

PURPOSE

Ovarian tissue (OT) cryopreservation is a treatment option for fertility preservation among young cancer patients. However, the procedure may involve a reduction in the GDF9-β expression and a delay in follicular growth after thawing and transplantation. The aim of this study was to evaluate whether supplementation of GDF9-β can compensate the reduction of this factor during the cryopresevation process and promote folliculogenesis after transplantation of thawed sheep ovarian tissue.

METHODS

Sheep OT was cryopreserved using two methods of vitrification and slow freezing. Fresh and thawed OTs were then transplanted onto chick embryo chorioallantoic membrane (CAM) and then divided into two groups based on the addition of GDF9-β to the grafted tissue. After 5 days of culture, both histological and immunohistological (Ki-67) assessments were performed to evaluate follicular structure, development, and proliferation. The fibrotic and necrotic areas were measured using MICROVISIBLE software.

RESULTS

Folliculogenesis took place in all culture groups, but was significantly improved only in the +GDF9-β cultured group. Also, better follicular structure was preserved in the aforementioned group (p < 0.05). When GDF9-β was supplemented to the culture medium, more neovascularization (p < 0.05) and better transplantation (p > 0.05) was observed. Furthermore, the areas of fibrosis and necrosis were lower in this group rather than the controls. Follicular proliferative activity was significantly higher only in the slow freezing +GDF9-β cultured group.

CONCLUSIONS

GDF9-β, as a stimulatory factor, not only promoted the folliculogenesis in the fresh ovarian transplant, but also compensated for its reduction during the cryopreservation process.

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.

Cryopreservation of Zebrafish Spermatogonia by Whole Testes Needle Immersed Ultra-Rapid Cooling

Current trends in science and biotechnology lead to creation of thousands of new lines in model organisms thereby leading to the necessity for new methods for safe storage of genetic resources beyond the common practices of keeping breeding colonies. The main purpose of this study was to adapt the needle immersed vitrification (NIV) procedure to cryopreserve whole zebrafish testes. Cryopreservation of early-stage germ cells by whole testes NIV offers possibilities for the storage of zebrafish genetic resources, especially since after transplantation they can mature into both male and female gametes. Testes were excised, pinned on an acupuncture needle, equilibrated in two cryoprotective media (equilibration solution containing 1.5 M methanol and 1.5 M propylene glycol; and vitrification solution containing 3 M dimethyl sulfoxide and 3 M propylene glycol) and plunged into liquid nitrogen. Samples were warmed in a series of three consequent warming solutions. The main advantages of this technique are (1) the lack of spermatozoa after digestion of warmed testes thus facilitating downstream manipulations; (2) ultra-rapid cooling enabling the optimal exposure of tissues to liquid nitrogen therefore maximizing the cooling and reducing the required concentration of cryoprotectants, thereby reducing their toxicity; (3) synchronous exposure of several testes to cryoprotectants and liquid nitrogen; and (4) repeatability demonstrated by obtaining viability of above 50% in five different zebrafish strains.

Vitrification and in vitro culture had no adverse effect on the follicular development and gene expression of stimulated human ovarian tissue

AIM

The study assesses the effect of the vitrification procedure on the integrity, morphology, follicular development and gene expression of stimulated human ovarian tissue after warming and two weeks of in vitro culture.

METHODS

Ovarian specimens were divided into non-vitrified and vitrified groups and were cultured for two weeks. Morphological analysis and immunohistochemistry were performed. The 17-β estradiol and anti-Müllerian hormone levels in collected media were assessed. Gene expression was analyzed using real-time reverse transcription polymerase chain reaction.

RESULTS

The morphology and immunohistochemistry of bcl-2-like protein 4 and B-cell lymphoma 2 of human stimulated ovarian tissue were similar in both groups. There was no significant difference in the percentage of normal follicles between the groups before and after in vitro culture. In spite of an increase in the percentage of growing follicles in cultured tissues compared to the non-cultured groups, the rate of normal follicles was significantly decreased in both cultured groups (P < 0.05). Gene expression was no different in vitrified tissues compared to the control; however, the expression of growth differentiation factor 9 and follicle stimulating hormone receptor genes were increased and factor in germ line alpha and kit ligand genes were decreased during in vitro culture (P < 0.05). In the two cultured groups, the level of 17-β estradiol was increased (P < 0.05), but the anti-Müllerian hormone concentration was not statistically altered.

CONCLUSIONS

These results showed that the integrity of stimulated human ovarian tissue after vitrification/warming was well preserved; however, the in vitro culture condition needs improvement.

Cryopreservation of human ovarian tissue using the silver closed vitrification system

PURPOSE

The aim of this study is to evaluate the feasibility of using a hand-made silver container for the cryopreservation of human ovarian cortex.

METHODS

Human ovarian cortex tissues were vitrified using an open vitrification system (OVS) of needle immersed vitrification (NIV) and two closed vitrification systems (CVS) of a plastic vial (plastic CVS) and a silver container (silver CVS). Outcomes of vitrification were evaluated morphologically and histologically by in vitro culture and xenotransplantation. The apoptosis of primordial follicles was assessed by TUNEL staining. The production of E2 and P4 was examined by a chemiluminescent immunoassay. Blood vessels were visualized with CD31 staining.

RESULTS

Compared with the fresh ovarian cortex tissue, ovarian cortex tissues that were vitrified using the three different carriers and then warmed showed significantly reduced percentages of normal primordial follicles, viability of primordial follicles, E2 and P4 levels during in vitro culture and decreased amounts of blood vessels. However, much better outcomes were obtained with NIV and silver CVS than with plastic CVS, based on the better morphology and viability of primordial follicles, higher E2 and P4 production during an in vitro culture, and greater numbers of blood vessels after xenografting. Importantly, the outcomes of ovarian cortex cryopreservation with silver CVS were similar and comparable to those with NIV.

CONCLUSIONS

The hand-made silver container as a CVS is a promising carrier for the cryopreservation of the human ovarian cortex.

Determination of Follicular Localization in Human Ovarian Cortex for Vitrification

PURPOSE

To determine the optimal follicle localization for ovarian vitrification in adolescent and young adult (AYA)-aged (between 15 and 39 years of age) patients with cancer or primary ovarian insufficiency (POI).

METHODS

In total, ovaries from 24 women were included in our study. These include women who received ovariectomy for fertility preservation before gonadotoxic treatments for cancer (n = 4), or for the treatment of POI by the in vitro activation method (n = 8), and other women and infants (0-3 years of age) whose ovaries were autopsied (n = 12). Before cryopreservation, a portion of the ovary sampled from cancer and POI patients was used for histological analysis. Depths of follicles from the surface of ovarian cortices were then measured by using digital imaging software. The locations of the follicles at different developmental stages in the ovarian cortex were noted.

RESULTS

The mean depth at which the primordial and primary follicles were located was 271 μm in infants. This was deeper in women in their twenties, thirties, and forties (501, 462, and 493 μm, respectively). The majority of secondary follicles were located <1000 μm from the ovarian surface (mean depth, 639 μm). In regard to patients with POI, the mean depth of primordial and primary follicles was 566 μm, whereas 70% of secondary follicles were located >1000 μm deep.

CONCLUSION(S)

These findings suggest that <1 mm is a potential optimum thickness of normal ovarian tissue for vitrification and a requirement that thicker ovarian cortices include secondary follicles in POI patients.

Vitrification versus slow freezing for human ovarian tissue cryopreservation: a systematic review and meta-anlaysis

Vitrification is a well-accepted procedure for cryopreservation of gametes and embryos. Less is known, however, about its performance in preserving ovarian tissue, for which slow freezing is the current convention. Increasing interest is being focused on vitrification, but there are as yet no standard protocols for its use with ovarian tissue. In part, this is because of the variety of cell types and complex nature of ovarian tissue. We performed a meta-analysis of 14 studies that compared vitrification with slow freezing for cryopreservation of ovarian tissue. In the pooled analysis, there was no significant difference between the two methods in terms of the proportion of intact primordial follicles, but vitrification was associated with significantly less DNA damage. Secondary endpoints included the number of stromal cells, significantly higher with vitrification, and primordial follicle density, which did not differ between the two methods. The present meta-analysis suggests that vitrification may be more effective than slow freezing, with less primordial follicular DNA strand breaks and better preservation of stromal cells. These advantages should lead to improved ovarian function after transplantation.

Fertility Preservation in Cancer Patients: In Vivo and In Vitro Options

Oocyte, embryo and ovarian tissue cryopreservation are being increasingly proposed for fertility preservation among cancer patients undergoing therapy to enable them to have babies after the cancer is cured. Embryo cryopreservation is not appropriate for single girls without any sperm partner and also because oocyte retrieval is an extended procedure, it is impossible in cases requiring immediate cancer cure. Thus ovarian tissue cryopreservation has been suggested for fertility preservation especial in cancer patients. The main goal of ovarian cryopreservation is re-implanting the tissue into the body to restore fertility and the hormonal cycle. Different cryopreservation protocols have been examined and established for vitrification of biological samples. We have used Cryopin to plunge ovarian tissue into the liquid nitrogen and promising results have been observed. Ovarian tissue re-implantation after cancer cure has one problem- the possibility of recurrence of malignancy in the reimplanted tissue is high. Xenografting-implantation of the preserved tissue in another species- also has its drawbacks such as molecular signaling from the recipient. In vitro follicle culturing is a safer method to obtain mature oocytes for fertilization and the various studies that have been carried out in this area are reviewed in this paper.

Human umbilical cord stem cell conditioned medium versus serum-free culture medium in the treatment of cryopreserved human ovarian tissues in in-vitro culture: a randomized controlled trial

BACKGROUND

To reduce young female fertility loss, the in-vitro culture of cryopreserved ovarian cortical tissues (OCTs) is considered an effective approach without delaying treatment and undergoing stimulation medicine. However, ischemic damage and follicular loss during the in-vitro culture of OCTs are major technical challenges. Human umbilical cord stem cells (HUMSCs) and their conditioned medium (HUMSC-CM) have been considered to be potential resources for regeneration medicine because they secrete cytokines and enhance cell survival and function. The aim of this study was to determine whether HUMSC-CM improves the development of frozen-thawed in-vitro cultured ovarian tissues compared with a serum-free culture medium (SF-CM).

METHODS

The thawed OCTs (n = 68) were cultivated in HUMSC-CM and SF-CM in vitro for 8 days, and the ovarian tissues were processed and analyzed by a classical histological evaluation. The microvessel density (MVD) and apotosis detection during in-vitro culture of OCTs were also performed.

RESULTS

A significant difference in the rate of morphologically normal primordial follicles in the HUMSC-CM group was observed compared to that in the SF-CM group (group C) from days 2 to 4 (day 2: group B 58.0 ± 2.45% vs group C 32.0 ± 5.83%, p = 0.002; day 3: group B 55.5 ± 4.20% vs group C 21.0 ± 9.80%, p = 0.048; day 4: group B 52.0 ± 4.08% vs group C 21.5 ± 8.19%, p = 0.019). The microvessel density (MVD) detection showed a time-dependent increase and peaked on day 4. There was a significant difference between groups B (49.33 ± 0.58) and C (24.33 ± 3.79) (p = 0.036). The percentage of apoptotic follicles in group B was lower than that in group C on day 1 (13.75 ± 2.50% vs 27.0 ± 10.10%, p = 0.003), day 5 (11.75 ± 1.50% vs 51.0 ± 10.5%, p = 0.019) and day 7 (15.0 ± 5.10% vs 46.5 ± 21.75%, p = 0.018).

CONCLUSIONS

These data have provided the first experimental evidence of the effect of HUMSC-CM on frozen-thawed OCTs in vitro. The results showed that the HUMSC-CM group provided a better protecting effect on the in-vitro culture of the cryopreserved OCTs compared to the SF-CM group.

Attempts to improve human ovarian transplantation outcomes of needle-immersed vitrification and slow-freezing by host and graft treatments

PURPOSE

To investigate if needle-immersed vitrification or slow-freezing yields better implantation results for human ovarian tissue and which method benefits more when combined with the "improvement protocol" of host melatonin treatment and graft incubation with biological glue + vitamin E + vascular endothelial growth factor-A.

METHODS

Human ovarian tissue was preserved by needle-immersed vitrification or slow-freezing and transplanted into immunodeficient mice, either untreated (groups A and C, respectively) or treated with the improvement protocol (groups B and D, respectively). Grafted and ungrafted slices were evaluated by follicle counts, apoptosis assay and immunohistochemistry for Ki67 and platelet endothelial cell adhesion molecule (PECAM).

RESULTS

Follicle number in the recovered grafts was limited. The number of atretic follicles was significantly higher after vitrification with/without the improvement protocol and slow-freezing than that after slow-freezing + the improvement protocol. Stroma cell apoptosis was the lowest in the group D. PECAM staining showed a peripheral and diffuse pattern in the group D (mostly normal follicular morphology) and a diffuse pattern in all other groups (few follicles, mostly atretic), with significantly higher diffuse levels in the vitrification groups. Ki67 staining was identified in all normal follicles. Follicles did not survive transplantation in the vitrification groups.

CONCLUSIONS

Ovarian sample preparation with slow-freezing + the improvement protocol appears to yield better implantation outcomes than needle-immersed vitrification with/without the improvement protocol. The real quality of frozen tissue can be assessed only after grafting and not after thawing/warming.

Expression of Folliculogenesis-Related Genes in Vitrified Human Ovarian Tissue after Two Weeks In Vitro Culture

OBJECTIVE

This study was designed to evaluate the effects of vitrification and in vitro culture of human ovarian tissue on the expression of oocytic and follicular cell-related genes.

MATERIALS AND METHODS

In this experimental study, ovarian tissue samples were obtained from eight transsexual women. Samples were cut into small fragments and were then assigned to vitrified and non-vitrified groups. In each group, some tissue fragments were divided into un-cultured and cultured (in α-MEM medium for 2 weeks) subgroups. The normality of follicles was assessed by morphological observation under a light microscope using hematoxylin and eosin (H&E) staining. Expression levels of factor in the germ line alpha (FIGLA), KIT ligand (KL), growth differentiation factor 9 (GDF-9) and follicle stimulating hormone receptor (FSHR) genes were quantified in both groups by real-time reverse transcriptase polymerase chain reaction (RT-PCR) at the beginning and the end of culture.

RESULTS

The percentage of normal follicles was similar between non-cultured vitrified and non-vitrified groups (P>0.05), however, cultured tissues had significantly fewer normal follicles than non-cultured tissues in both vitrified and non-vitrified groups (P<0.05). In both cultured groups the rate of primary and secondary follicles was significantly higher than non-cultured tissues (P<0.05). The expression of all examined genes was not significantly altered in both non-cultured groups. Whiles, in comparison with cultured tissues non-cultured tissues, the expression of FIGLA gene was significantly decreased, KL gene was not changed, GDF-9 and FSHR genes was significantly increased (P<0.05).

CONCLUSION

Human ovarian vitrification following in vitro culture has no impairing effects on follicle normality and development and expression of related-genes. However, in vitro culture condition has deleterious effects on normality of follicles.

Fertility preservation through gonadal cryopreservation

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