Evidence of metabolic activity during low-temperature ovarian tissue preservation in different media

Prolonged cold-preservation of domestic cat ovarian tissue is improved by extracellular solution but impaired by the fragmentation of ovary

For domestic cats ovaries, recommended cold-storage limit is 24 h in Phosphate Buffered Saline (PBS) or Dulbecco`s PBS (DPBS). Here, we attempted to verify wheatear cat ovaries may benefit from more complex solutions during prolonged cold-storage (>24 h). First, the preservation capabilities of extracellular (SP+), intracellular (UW) solutions and DPBS supplemented with glutathione (DPBS+GSH) were compared using ovary fragments from the same ovary (n=10). Intact ovary stored in DPBS served as a control. Ovaries were kept at 4 °C for 48 h, and 72 h. In the second experiment, first ovary was stored in DPBS, second in SP+ or UW solution for 48 h (n = 12). Ovaries pairs stored in DPBS for 24 h served as a control (n=8). Tissue samples were evaluated directly after cold-storage and after following 24 h in vitro culture. Ovarian follicle morphology, apoptosis rates (cleaved caspase-3, TUNEL), and follicular growth activation (Ki-67) were assessed. Ovary fragmentation impaired follicular morphology preservation upon cold-storage comparing to intact ovary. However, ovarian fragments stored in UW for 48 h and in SP+ for 72 h presented better morphology than DPBS+GSH group. Comparison of intact ovaries cold-storage for 48 h showed that SP+ provided superior follicular morphology over DPBS, and it was comparable to the outcome of 24-hour storage. No follicular activation after in vitro culture was observed. Nevertheless, tissue culture increased considerably caspase-3 cleavage and TUNEL detection. The ovary fragmentation prior to cold-storage is not recommended in domestic cats. Replacement of DPBS with SP+ solution for whole ovary and UW solution for ovarian tissue fragments improves follicular structure preservation during 48-hour cold-storage.

Comparison of liquid nitrogen-free slow freezing protocols toward enabling a practical option for centralized cryobanking of ovarian tissue

Geographically distributed ovarian tissue cryobanks remain limited due to the high facility and staff costs, and cold transportation to centers is associated with ischemia-induced tissue damage that increases with transport distance. It is ideal to perform the cryopreservation procedure at a tissue removal site or local hospital before shipment to cost-effective centralized cryobanks. However, conventional liquid nitrogen-based freezers are not portable and require expensive infrastructure. To study the possibility of an ovarian tissue cryopreservation network not dependent on liquid nitrogen, we cryopreserved bovine ovarian tissue using three cooling techniques: a controlled rate freezer using liquid nitrogen, a liquid nitrogen-free controlled rate freezer, and liquid nitrogen-free passive cooling. Upon thawing, we evaluated a panel of viability metrics in frozen and fresh groups to examine the potency of the portable liquid nitrogen-free controlled and uncontrolled rate freezers in preserving the ovarian tissue compared to the non-portable conventional controlled rate freezer. We found similar outcomes for reactive oxygen species (ROS), total antioxidant capacity (TAC), follicular morphology, tissue viability, and fibrosis in the controlled rate freezer groups. However, passive slow cooling was associated with the lowest tissue viability, follicle morphology, and TAC, and the highest tissue fibrosis and ROS levels compared to all other groups. A stronger correlation was found between follicle morphology, ovarian tissue viability, and fibrosis with the TAC/ROS ratio compared to ROS and TAC alone. The current study undergirds the possibility of centralized cryobanks using a controlled rate liquid nitrogen-free freezer to prevent ischemia-induced damage during ovarian tissue shipment.

Kisspeptin decreases the adverse effects of human ovarian vitrification by regulating ROS-related apoptotic occurrences

Kisspeptin is characterized as a neuropeptide with a pivotal function in female and male infertility, and its antioxidant properties have been demonstrated. In this study, the effects of kisspeptin on the improvement of the vitrification and thawing results of human ovarian tissues were investigated. In this work, 12 ovaries from patients who underwent hysterectomy were collected laparoscopically, and then 32 samples from each of their tissues were taken. Haematoxylin and eosin (H&E) staining was performed to check the normality of the ovarian tissue and, subsequently, the samples were allocated randomly into four groups, including: (1) fresh (control), (2) vitrification, (3) vitrified + 1 μM kisspeptin, and (4) vitrified + 10 μM kisspeptin groups. After vitrification, thawing, and tissue culture processes, H&E staining for tissue quality assessment, terminal deoxynucleotidyl transferase dUTP nick end labelling assay for apoptosis evaluation, and malondialdehyde (MDA), superoxide dismutase (SOD), and ferric reducing ability of plasma tests for oxidative stress appraisal were carried out. Our histological results showed incoherency of ovarian tissue morphology in the vitrification group compared with other groups. Other findings implicated increased apoptosis rate and MDA concentration and reduced SOD activity and total antioxidant capacity (TAC) in the vitrification group compared with the control group (P < 0.05). Moreover, decreased apoptosis rate and MDA concentration, and increased TAC and SOD function were observed in the vitrification with kisspeptin groups (1 μM and 10 μM) compared with the vitrified group (P < 0.05). Our reports express that kisspeptin is an effective agent to overcome the negative effects of vitrification by regulating reactive oxygen species-related apoptotic processes.

Impact of prepubertal bovine ovarian tissue pre-freeze holding duration on follicle quality

Ovarian tissue cryopreservation prior to gonadotoxic treatment is the only recommended option for fertility preservation in prepubertal girls. Due to the technical complexity of this technique, limited number of centres across the world are equipped to offer the facility. Hence, the retrieved ovarian tissue needs to be maintained at hypothermic temperature (4 °C) for long time during shipment. The time taken between tissue retrieval and cryopreservation could influence the functionality of cells during fertility restoration. This study explored the tissue integrity and follicle quality of ovarian cortical slices subjected to pre-freeze holding for various time durations in vitro. Prepubertal bovine ovarian tissue from < 12 months old animals were handled at hypothermic holding (4 °C) for 0, 24, 48 and 72 h. The tissues were assessed for follicle viability through confocal analysis of live-dead labelled samples, and follicle quality and tissue integrity through histology. Results have shown that follicle viability, and overall follicle quality were not significantly affected at the end of 72 h hypothermic holding. Though, the observation reassures extended hypothermic holding prior to freezing, findings need to be validated in human tissue prior to use in clinical fertility preservation programs.

Investigation of the optimal culture time for warmed bovine ovarian tissues before transplantation

Ovarian tissue cryopreservation by vitrification is an effective technique, but there are still many unresolved issues related to the procedure. The aim of this study was to investigate the optimal culture time of post-warmed ovarian tissues and their viability before ovarian tissue transplantation. The bovine ovarian tissues were used to evaluate the effect of post-warming culture periods (0, 0.25, 0.5, 1, 2, 5 and 24 hours) in the levels of residual cryoprotectant, LDH release, ROS generation, gene and protein abundance, and follicle viability and its mitochondrial membrane potential. Residual cryoprotectant (CPA) concentration decreased significantly after 1 hour of culture. The warmed ovarian tissues that underwent between 0 to 2 hours of culture time showed similar LDH and ROS levels compared to fresh non-frozen tissues. The AMH transcript abundance did not differ in any of the groups. No increase in the relative transcript abundance and protein level of Caspase 3 and Cleaved-Caspase 3, respectively, in the first 2 hours of culture after warming. On the other hand, an increased protein level of double stranded DNA breaks (gamma-H2AX) was observed in post-warmed tissues disregarding the length of culture time, and a temporary reduction in pan-AKT was detected in post-warming tissues between 0 to 0.25 hours of culture time. Prolonged culture time lowered the percentage of viable follicles in warmed tissues, but it did not seem to affect the follicular mitochondrial membrane potential. In conclusion, 1 to 2 hours of culture time would be optimal for vitrified-warmed tissues before transplantation.

Analysis of Fertility Preservation by Ovarian Tissue Cryopreservation in Pediatric Children in China

BACKGROUND

Ovarian tissue cryopreservation (OTC) is the only method of fertility preservation (FP) in prepubertal girls, but the experience remains limited. This study investigates the effectiveness and feasibility of FP of OTC in children facing gonadotoxicity treatment in Chinese first ovarian tissue cryobank.

PROCEDURE

OTC and evaluation of 49 children ≤14 years old in the cryobank of Beijing Obstetrics and Gynecology Hospital, Capital Medical University, from July 2017 to May 19, 2022, were analyzed retrospectively. We compared children's general characteristics, follicle numbers, and hormone levels with and without chemotherapy before OTC.

RESULTS

The age of 49 children at the time of OTC was 7.55 (1-14) years old. There were 23 cases of hematological non-malignant diseases, eight cases of hematological malignant diseases, four cases of gynecological malignant tumors, one case of neurological malignant tumors, one case of bladder cancer, five cases of sarcoma, three cases of mucopolysaccharidosis, one case of metachromatic leukodystrophy, two cases of dermatomyositis, one case of Turner's syndrome. The median follicular count per 2-mm biopsy was 705. Age and AMH were not correlated (r = 0.084, P = 0.585). Age and follicle count per 2-mm biopsy was not correlated (r = -0.128, P = 0.403). Log10 (follicle count per 2-mm biopsy) and Log10 (AMH) were not correlated (r = -0.118, P = 0.456). Chemotherapy before OTC decreased AMH levels but had no significant effect on the number of follicles per 2-mm biopsy.

CONCLUSIONS

OTC is the only method to preserve the fertility of prepubertal girls, and it is safe and effective. Chemotherapy before OTC is not a contraindication to OTC.

Histidine buffered media maintains pH stabile during cooled transportation of human ovarian tissue

The aim of this study was to investigate whether pH is stable when transporting ovarian tissue in media buffered with either HEPES or histidine. Furthermore, if the choice of transport media impacts the in vitro maturation rate of oocytes collected in connection with ovarian tissue cryopreservation. Human ovaries (n = 34) collected for ovarian tissue cryopreservation were transported immersed in either 30 ml of HEPES buffered (follicle flushing media (Origio; Denmark)) or histidine buffered media (Custodiol®-HTK, Koehler-Chemie, Germany). Tissue was transported on ice for 4–5 h. At arrival, the ovary was weighed, and the pH of the media was measured at 0 °C. From 15 patients, immature oocytes were collected for in vitro maturation, oocytes that matured to metaphase II were evaluated. The pH measured in the HEPES buffered media (pH = 7.5 ± 0.13, n = 18) was significantly higher (p < 0.001) than the pH measured in the histidine buffered media (pH = 7.2 ± 0.05, n = 16). The standard deviation of pH measurements for the histidine buffered media was significantly lower than for the HEPES buffered media measurements (p < 0.0001). A total of 170 and 247 immature oocytes were collected and in vitro matured from ovaries transported in HEPES and histidine buffered media, respectively. The maturation rate of immature oocytes after IVM was similar in the two groups. The results show that pH in the histidine buffered media is closer to the physiological level and more stable than in HEPES buffered medium and support the use of histidine buffered media for cooled transportation of human ovaries.

Long-time low-temperature transportation of human ovarian tissue before cryopreservation

RESEARCH QUESTION

Can the low-temperature transport time of removed human ovarian tissue be prolonged until cryopreservation?

DESIGN

Fresh ovarian cortex from nine premenopausal patients was either slow-frozen immediately or stored at 4°C for 24 or 48 h before slow-freezing. The fresh and frozen-thawed biopsies were evaluated by follicle counting via calcein staining, histologic analyses via haematoxylin and eosin staining, and apoptosis via terminal deoxynucleotidyl transferase-mediated dUDP nick-end labelling (TUNEL). The fresh cortex was assessed by reactive oxygen species (ROS) and total antioxidant capacity (TAC) assay to detect oxidative stress. The frozen-thawed cortex biopsies were also evaluated by quantitative PCR for messenger RNA (mRNA) expression of BCL-2, BAX, TNFa, HIF-1a, BMP15 and GDF9, and Western blot for detection of BCL-2, BMP15, GDF9 and CASPASE-3. The frozen-thawed cortex was cultured in vitro for 4 days, anti-Müllerian hormone and glucose were assessed in the supernatant, and ROS and TAC assay detected any oxidative stress in the cortex.

RESULTS

In the fresh cortex, there were no significant differences between the three groups. In the frozen-thawed cortex, there were no significant differences between the three groups regarding follicle viability, TUNEL, mRNA expression of TNFa, HIF-1a or BMP15. GDF9 mRNA and BAX/BCL-2 were lower and higher at 48 h than at 0 h, respectively. However, the protein expression of BCL-2, CASPASE-3, GDF9 and BMP15 were no different. In the cultured cortex, ROS, TAC and glucose uptake were no different across the three groups.

CONCLUSION

Ovarian tissue transportation was validated for 24 h in the procedure used in clinical practice. This study showed that 4-8°C transportation for 24 or 48 h does not seem to damage the ovarian tissue. However, ovarian tissue transportation beyond 48 h needs to be further studied for conclusions to be made.

Ovarian tissue transportation: a systematic review

In recent years, some countries and fertility preservation networks have started adopting 24 h transportation for ovarian tissue, a practice that has the potential to spread very quickly due to the high costs and bureaucracy involved in the establishment of ovarian tissue cryobanks. While pregnancies and live births have been reported after such long periods of transportation, this, however, remains an empirical procedure. This review aims to prompt reflection on ovarian tissue transport, highlighting the lack of knowledge in humans by providing a counterpoint looking into more than 40 studies published in different animal models. By discussing these studies in animals, the findings of various models can be deciphered, and light shed on the patterns identified. Like the development of different assisted reproductive technology procedures, this is an important step in creating guidelines for future studies on human ovarian tissue transportation.