Morphometrical analysis of preantral follicular survival of VEGF-treated bovine ovarian cortex tissue following xenotransplantation in an immune deficient mouse model

Production of marmoset eggs and embryos from xenotransplanted ovary tissues

The common marmoset (Callithrix jacchus) has attracted attention as a valuable primate model for the analysis of human diseases. Despite the potential for primate genetic modification, however, its widespread lab usage has been limited due to the requirement for a large number of eggs. To make up for traditional oocyte retrieval methods such as hormone administration and surgical techniques, we carried out an alternative approach by utilizing ovarian tissue from deceased marmosets that had been disposed of. This ovarian tissue contains oocytes and can be used as a valuable source of follicles and oocytes. In this approach, the ovarian tissue sections were transplanted under the renal capsules of immunodeficient mice first. Subsequent steps consist of development of follicles by hormone administrations, induction of oocyte maturation and fertilization, and culture of the embryo. This method was first established with rat ovaries, then applied to marmoset ovaries, ultimately resulting in the successful acquisition of the late-stage marmoset embryos. This approach has the potential to contribute to advancements in genetic modification research and disease modeling through the use of primate models, promoting biotechnology with non-human primates and the 3Rs principle in animal experimentation.

Metabolic and secretory recovery of slow frozen-thawed human ovarian tissue in vitro

Within the options available for fertility preservation, cryopreservation of ovarian cortical tissue has become an important technique. Freezing and thawing procedures have been optimized to preserve tissue integrity and viability. However, the improvement of the tissue retransplantation is currently of great interest. Rapid angiogenesis is needed at the retransplantation site to accomplish sufficient blood supply to provide oxygen and nutrients. Many studies address this issue. However, we need to understand the physiology of the thawed tissue to gain further understanding of the complexities of the procedure. As freezing and thawing generally impairs cellular metabolism, we aimed to characterize the changes in metabolic activity and secretion of the angiogenic factor vascular endothelial growth factor-A (VEGF-A) of frozen-thawed ovarian cortical tissue over time. Biopsy punches of ovarian cortical tissue from patients undergoing fertility preservation were maintained in culture without freezing or after a slow-freezing and thawing procedure. VEGF-A secretion was measured after 48 h by ELISA. To examine temporary changes, metabolic activity was assessed for both fresh and frozen-thawed tissue of the same patient. Metabolic activity and VEGF-A secretion were measured at 0, 24 and 48 h in culture. Thawed ovarian cortical tissue secreted significantly less VEGF-A compared to fresh ovarian cortical tissue within 48 h of culture. After thawing, metabolic activity was significantly reduced compared to fresh ovarian cortex but over the course of 48 h, the metabolic activity recovered. Similarly, VEGF-A secretion of thawed tissue increased significantly over 48 h. Here, we have shown that it takes 48 h for ovarian cortical tissue to recover metabolically after thawing, including VEGF-A secretion.

Ovarian tissue damage after grafting: systematic review of strategies to improve follicle outcomes

Frozen-thawed human ovarian tissue endures large-scale follicle loss in the early post-grafting period, characterized by hypoxia lasting around 7 days. Tissue revascularization occurs progressively through new vessel invasion from the host and neoangiogenesis from the graft. Such reoxygenation kinetics lead to further potential damage caused by oxidative stress. The aim of the present manuscript is to provide a systematic review of proangiogenic growth factors, hormones and various antioxidants administered in the event of ovarian tissue transplantation to protect the follicle pool from depletion by boosting revascularization or decreasing oxidative stress. Although almost all investigated studies revealed an advantage in terms of revascularization and reduction in oxidative stress, far fewer demonstrated a positive impact on follicle survival. As the cascade of events driven by ischaemia after transplantation is a complex process involving numerous players, it appears that acting on specific molecular mechanisms, such as concentrations of proangiogenic growth factors, is not enough to significantly mitigate tissue damage. Strategies exploiting the activated tissue response to ischaemia for tissue healing and remodelling purposes, such as the use of antiapoptotic drugs and adult stem cells, are also discussed in the present review, since they yielded promising results in terms of follicle pool protection.

Leptin decreases apoptosis and promotes the activation of primordial follicles through the phosphatidylinositol-3-kinase/protein kinase B pathway in cultured ovine ovarian tissue

This study evaluated the effects of leptin on primordial follicle survival and activation after in vitro culture of ovine ovarian tissue and if leptin acts through the phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) pathway. Ovarian fragments were fixed for histology (fresh control) or cultured for 7 days in control medium (α-MEM+) alone or supplemented with leptin (1, 5, 10, 25 or 50 ng/ml). Follicle morphology, activation and apoptosis were analyzed. Next, the fragments were cultured in the medium that showed the best results in the absence or the presence of the PI3K inhibitor (LY294002), and immunohistostaining of p-Akt protein was assessed. After culture, the percentage of normal follicles decreased (P < 0.05) in all treatments compared with the fresh control. Moreover, control medium and 1 ng/ml leptin had similar (P > 0.05) percentages of normal follicles, which were significantly higher than those in other treatments. However, culture with 1 ng/ml leptin maintained apoptosis similarly (P > 0.05) to that of the fresh control and lower (P < 0.05) than that in α-MEM+. Leptin did not influence follicle activation (P > 0.05) compared with the control medium (α-MEM+). Culture in 1 ng/ml leptin with LY294002 decreased the normal follicles and increased apoptosis, inhibited follicle activation (P < 0.05), and reduced p-Akt immunostaining, compared with the medium containing 1 ng/ml leptin without PI3K inhibitor. In conclusion, leptin at 1 ng/ml reduces apoptosis and promotes the activation of primordial follicles compared with the fresh control after in vitro culture of ovine ovarian tissue possibly through the PI3K/Akt pathway.

Passive slow freezing is an efficacious and cost-effective alternative to controlled slow freezing for ovarian tissue cryopreservation

We aimed to assess the feasibility of passive slow freezing (PSF using Mr. Frosty container, Nalgene) as an alternative to controlled slow rate freezing (CSF using (Freezal™, Air liquide)) for human ovarian tissue (OT) cryopreservation. Validation studies needed were determined after assessing the risk associated (EuroGTP-II ART tool) and were conducted in 66 OT samples from 10 transgender men aged 23.4 ± 5.1 y. Folliculogenesis was assessed in vitro (after 2 h and 2 days of culture) and in vivo (2, 4 and 6 weeks xenotransplantation in Balbc/nude mice) by haematoxilin-eosin staining. Fibrosis was assessed by Masson's trichrome staining. Immunohistochemistry was used to study cell proliferation (PCNA and Ki-67) and apoptosis (caspase-3 and TUNEL). Differences in percentages were estimated using a generalized estimated equations method. After 2 days of in vitro culture, higher odds of primordial follicles (PF) (OR 1.626; 95%CI (1.162-2.266); P = 0.004) and lower odds of growing follicles (GF) (OR 0.616; 95%CI (0.441-0.861); P = 0.004) were associated with the established CSF technique. No statistical differences were found in the mean estimated proportion of proliferating (Ki-67+ or PCNA+) or apoptotic (caspase-3+ or Tunel+) follicles. Two and 6 weeks after xenotransplantation, respectively lower odds of GF (OR 0.419; 95%CI (0.217-0.809); P = 0.010) and secondary follicles (OR 0.135; 95%CI (0.071-0.255); P < 0.001) were associated with CSF. Proportion of fibrosis was similar. This validation study shows a higher follicle activation after 2 days in vitro and after 2 weeks following xenotransplantation in mice using PSF. PSF may be an easy, cost-effective low-risk alternative to CSF for cryopreservation of human OT.

Hormonal Stimulation of Human Ovarian Xenografts in Mice: Studying Folliculogenesis, Activation, and Oocyte Maturation

Ovarian tissue cryopreservation and banking provides a fertility preservation option for patients who cannot undergo oocyte retrieval; it is quickly becoming a critical component of assisted reproductive technology programs across the world. While the transplantation of cryopreserved ovarian tissue has resulted in over 130 live births, the field has ample room for technological improvements. Specifically, the functional timeline of grafted tissue and each patient's probability of achieving pregnancy is largely unpredictable due to patient-to-patient variability in ovarian reserve, lack of a reliable method for quantifying follicle numbers within tissue fragments, potential risk of reintroduction of cancer cells harbored in ovarian tissues, and an inability to control follicle activation rates. This review focuses on one of the most common physiological techniques used to study human ovarian tissue transplantation, xenotransplantation of human ovarian tissue to mice and endeavors to inform future studies by discussing the elements of the xenotransplantation model, challenges unique to the use of human ovarian tissue, and novel tissue engineering techniques currently under investigation.

Involvement of PTEN and FOXO3a Proteins in the Protective Activity of Protocatechuic Acid Against Cisplatin-Induced Ovarian Toxicity in Mice

The present study evaluated the effects of protocatechuic acid (PCA) after cisplatin-induced ovarian toxicity in mice and if PTEN and FOXO3a proteins are involved in PCA action. The mice were divided into five experimental groups (five animals per group) and treated once a day for 3 days as follows: (1) the control group was pretreated with oral administration (o.p.) of saline solution, followed by an intraperitoneal (i.p.) injection of saline solution. The other groups were pretreated (o.p.) with (2) saline solution (cisplatin group), (3) N-acetylcysteine (150 mg/kg of body weight), or with (4) 20 or (5) 50 mg/kg body weight of PCA, followed by 5 mg/kg body weight (i.p.) of cisplatin. Next, the ovaries were destined to histological (morphology and activation), immunohistochemical (PCNA and cleaved caspase-3 expression), and fluorescence (reactive oxygen species [ROS], glutathione [GSH], and active mitochondria levels) analyses. Moreover, the immunoreactivity for p-PTEN and p-FOXO3a was evaluated to investigate a potential mechanism by which PCA could prevent the cisplatin-induced ovarian damage. Pretreatment with N-acetylcysteine or 20 mg/kg PCA before cisplatin preserved the percentage of normal follicles and cell proliferation as observed in the control, reduced apoptosis and ROS levels, and showed higher active mitochondria and GSH levels than the cisplatin treatment (P < 0.05). Moreover, pretreatment with 20 mg/kg PCA decreased cisplatin-induced p-PTEN and increased (P < 0.05) nuclear export of p-FOXO3a. In conclusion, PCA at 20 mg/kg reduced apoptosis, maintained cell proliferation and mitochondrial function, reduced ROS production, and increased GSH expression likely through the involvement of PTEN and FOXO3a proteins.

Heterotopic autotransplantation of ovarian tissue in a large animal model: Effects of cooling and VEGF

Heterotopic and orthotopic ovarian tissue autotransplantation techniques, currently used in humans, will become promising alternative methods for fertility preservation in domestic and wild animals. Thus, this study describes for the first time the efficiency of a heterotopic ovarian tissue autotransplantation technique in a large livestock species (i.e., horses) after ovarian fragments were exposed or not to a cooling process (4°C/24 h) and/or VEGF before grafting. Ovarian fragments were collected in vivo via an ultrasound-guided biopsy pick-up method and surgically autografted in a subcutaneous site in both sides of the neck in each mare. The blood flow perfusion at the transplantation site was monitored at days 2, 4, 6, and 7 post-grafting using color-Doppler ultrasonography. Ovarian grafts were recovered 7 days post-transplantation and subjected to histological analyses. The exposure of the ovarian fragments to VEGF before grafting was not beneficial to the quality of the tissue; however, the cooling process of the fragments reduced the acute hyperemia post-grafting. Cooled grafts compared with non-cooled grafts contained similar values for normal and developing preantral follicles, vessel density, and stromal cell apoptosis; lower collagen type III fibers and follicular density; and higher stromal cell density, AgNOR, and collagen type I fibers. In conclusion, VEGF exposure before autotransplantation did not improve the quality of grafted tissues. However, cooling ovarian tissue for at least 24 h before grafting can be beneficial because satisfactory rates of follicle survival and development, stromal cell survival and proliferation, as well as vessel density, were obtained.

Epigallocatechin-3-gallate (EGCG) reduces apoptosis of preantral follicles through the phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) signaling pathway after in vitro culture of sheep ovarian tissue

The aims of this study were to analyze the effects of different concentrations of epigallocatechin-3-gallate (EGCG) on the primordial follicle survival and development after in vitro culture of ovarian tissue, and to verify the possible involvement of the phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathway in the EGCG actions in the sheep ovary. Ovarian fragments were fixed for histological analysis (fresh control) or cultured in α-minimum essential medium alone (α-MEM⁺: control medium) or with different concentrations of EGCG (0.01; 0.1; 1; 10 or 100 μg/mL) for 7 days. Inhibition of PI3K activity was performed in fragments cultured with 1 μg/mL EGCG plus LY294002. Thereafter, immunohistochemistry was performed to evaluate the expression of cleaved caspase-3 and AKT phosphorylation (p-AKT). The results showed that 1 μg/mL EGCG maintained the follicular survival similar (P > 0.05) to that of the fresh control and higher (P < 0.05) than that of the α-MEM⁺ and other EGCG treatments. No difference (P > 0.05) in the follicular activation was observed. However, both follicle and oocyte diameters increased after in vitro culture with 1 μg/mL EGCG compared to other treatments (P < 0.05), except for 10 μg/mL EGCG (P > 0.05). After PI3K inhibition, there was an increase (P < 0.05) of the follicular apoptosis and a reduction of p-AKT immunolocalization. In conclusion, EGCG at 1 μg/mL reduces apoptosis of preantral follicles through the PI3K/AKT pathway after in vitro culture of sheep ovarian tissue.

Advances in in vitro folliculogenesis in domestic ruminants

The in vitro follicle culture (IVFC) represents an outstanding tool to enhance our understanding of the control of folliculogenesis and to allow the future use of a large number of immature oocytes enclosed in preantral follicles (PFs) in assisted reproductive techniques in humans as well as in others mammalian species including the ruminants. So far, the best results of IVFC were reported from mice with the production of live offspring from primordial follicles cultured in vitro. Live birth has been obtained after the in vitro culture of bovine early antral follicles. However, in other ruminant species, these results have been limited to the production of a variable number of mature oocytes and low percentages of embryos after in vitro culture of goat, buffalo and sheep isolated secondary preantral follicles. The present review presents and discusses the main findings, limitations, and prospects of in vitro folliculogenesis in ruminants focusing on bovine, caprine, and ovine species.

Heterotopic ovarian allotransplantation in goats: Preantral follicle viability and tissue remodeling

An appropriate implantation site favors angiogenesis and avoids ovarian tissue damage after tissue grafting. The objective of this study was to evaluate the effects of intramuscular (IM) and subcutaneous (SC) sites for ovarian grafts in goats by evaluating follicular morphology and activation, preantral follicle and stromal cell densities, tissue DNA fragmentation, collagen types I and III depositions, and graft revascularizations. Ovarian cortical tissue was transplanted in IM or SC sites and recovered 7 or 15 days post-transplantation. There was a greater percentage of developing follicles and lesser follicular and stromal cell densities in all grafted tissues as compared to ovarian tissues of the control group. The stromal cell density and percentage of normal follicles were positively associated. At 15 days post-transplantation, tissues at the SC and IM sites had similar amounts of DNA fragmentation and type III collagen content. In contrast, tissues at the SC, as compared with IM site, had greater abundances of collagen type I. Furthermore, there was a positive association between collagen type I and percentage of morphologically normal follicles post-transplantation. In addition to a marked decrease in follicular density 15 days post-transplantation in ovarian grafts at the SC and IM sites, low percentages of normal follicles and follicular activation were observed similarly in both transplantation sites. There were also positive associations of stromal cell density and abundance of type I collagen fibers with the percentage of intact follicles in grafted ovarian tissues.

Is the pre-antral ovarian follicle the 'holy grail'for female fertility preservation?

Fertility preservation is not only a concern for humans with compromised fertility after cancer treatment. The preservation of genetic material from endangered animal species or animals with important genetic traits will also greatly benefit from the development of alternative fertility preservation strategies. In humans, embryo cryopreservation and mature-oocyte cryopreservation are currently the only approved methods for fertility preservation. Ovarian tissue cryopreservation is specifically indicated for prepubertal girls and women whose cancer treatment cannot be postponed. The cryopreservation of pre-antral follicles (PAFs) is a safer alternative for cancer patients who are at risk of the reintroduction of malignant cells. As PAFs account for the vast majority of follicles in the ovarian cortex, they represent an untapped potential, which could be cultivated for reproduction, preservation, or research purposes. Vitrification is being used more and more as it seems to yield better results compared to slow freezing, although protocols still need to be optimized for each specific cell type and species. Several methods can be used to assess follicle quality, ranging from simple viability stains to more complex xenografting procedures. In vitro development of PAFs to the pre-ovulatory stage has not yet been achieved in humans and larger animals. However, in vitro culture systems for PAFs are under development and are expected to become available in the near future. This review will focus on recent developments in (human) fertility preservation strategies, which are often accomplished by the use of in vitro animal models due to ethical considerations and the scarcity of human research material.

Evaluation of Z-VAD-FMK as an anti-apoptotic drug to prevent granulosa cell apoptosis and follicular death after human ovarian tissue transplantation

PURPOSE

To evaluate the efficiency of ovarian tissue treatment with Z-VAD-FMK, a broad-spectrum caspase inhibitor, to prevent follicle loss induced by ischemia/reperfusion injury after transplantation.

METHODS

In vitro, granulosa cells were exposed to hypoxic conditions, reproducing early ischemia after ovarian tissue transplantation, and treated with Z-VAD-FMK (50 μM). In vivo, cryopreserved human ovarian fragments (n = 39) were embedded in a collagen matrix containing or not Z-VAD-FMK (50 μM) and xenotransplanted on SCID mice ovaries for 3 days or 3 weeks.

RESULTS

In vitro, Z-VAD-FMK maintained the metabolic activity of granulosa cells, reduced HGL5 cell death, and decreased PARP cleavage. In vivo, no improvement of follicular pool and global tissue preservation was observed with Z-VAD-FMK in ovarian tissue recovered 3-days post-grafting. Conversely, after 3 weeks of transplantation, the primary follicular density was higher in fragments treated with Z-VAD-FMK. This improvement was associated with a decreased percentage of apoptosis in the tissue.

CONCLUSIONS

In situ administration of Z-VAD-FMK slightly improves primary follicular preservation and reduces global apoptosis after 3 weeks of transplantation. Data presented herein will help to guide further researches towards a combined approach targeting multiple cell death pathways, angiogenesis stimulation, and follicular recruitment inhibition.

Hematological and biochemical profile of BALB/c nude and C57BL/6 SCID female mice after ovarian xenograft

Hematological and biochemical profile studies help to evaluate functional changes of animals used in experiments. The aim of this study was to determine the hematological and biochemical profile of immunosuppressed BALB/c nude and C57BL/6 SCID mice after bovine ovarian xenotransplantation. Therefore, a total of 74 female mice were divided into four groups: non-xenotransplanted animals, xenotransplanted animals, xenotransplanted animals treated with eCG and xenotransplanted animals treated with FSH + LH. After anesthesia, blood samples were collected and hematologic and biochemical values were evaluated. The results showed no significant differences (p ≤ 0.05) for hematological parameters between the control group and the treatment groups of both strains. However, considering the biochemical profile, it was observed an increase of AST concentrations (p ≤ 0.05) in both strains and a decrease of ALT concentrations (p ≤ 0.05) only in C57BL/6 SCID strain of the groups subjected to hormonal treatment compared with those non subjected. Additionally, the values of the renal enzymes, urea and creatinine, did not differ (p ≤ 0.05) between the groups. Our findings suggest that the xenotransplantation procedure as well as the hormonal dosages had no significant effect on the well-being of the animals considering the evaluated hematological and biochemical profile.

Effect of treatment with angiopoietin-2 and vascular endothelial growth factor on the quality of xenografted bovine ovarian tissue in mice

Cryopreservation and transplantation of ovarian tissue (OT) represents a method for fertility preservation. However, as the transplantation is performed without vessel anastomosis, unavoidable ischemic damage occurs. To reduce this ischemic damage and improve outcomes after transplantation, we used two kind of angiogenic factors, angiopoietin-2 (ang-2) and vascular endothelial growth factor (VEGF). Fresh or vitrified-warmed bovine OTs were prepared for xenotransplantation (XT). Fresh OTs were immediately xenografted into nude mice (XT-Fresh). Vitrified-warmed OTs were xenografted into four subgroups of mice, which were injected intraperitoneally before XT with saline (XT-Vitri), Ang-2 (XT-Ang-2), VEGF (XT-VEGF), and a combination of Ang-2 and VEGF (XT-Combined). Seven or 28 days post-grafting, grafted OTs and blood samples were collected for evaluation. Follicle normality was higher in the angiogenic factor-treated groups than in the XT-Vitri group. The XT-VEGF and the XT-Combined showed higher (P<0.05) follicular density than the XT-Vitri group. The highest apoptotic follicle ratio was observed in the XT-Vitri group on day 7; this was decreased (P<0.05) in the XT-Combined group. Microvessel densities were higher in the angiogenic factor-treated groups than in the XT-Vitri group. The largest fibrotic area was showed in the XT-Vitri group on day 28, and it was decreased (P<0.05) in the XT-combined group. Based on these results, administration of Ang-2 and VEGF to recipients prior to XT appeared to alleviate ischemic damage by enhancing angiogenesis, which resulted in the maintenance of follicle integrity and density, and reduced follicle apoptosis and OT fibrosis.