Cat and dog primordial follicles enclosed in ovarian cortex sustain viability after in vitro culture on agarose gel in a protein-free medium

In Vitro Growth of Human Follicles: Current and Future Perspectives

Ovarian tissue cryopreservation is gaining importance as a successful method to restore fertility to girls and young women at high risk of sterility. However, there are concerns regarding the safety of transplantation after ovarian tissue cryopreservation due to the high risk of reintroducing cancer cells and causing disease recurrence. In these cases, the development of culture systems that support oocyte development from the primordial follicle stage is required. Notable achievements have been reached in human follicle in vitro growth in the past decade. Currently, systems for the in vitro culture of ovarian tissue are based on two-dimensional substrates that do not support the survival of follicles or recapitulate the mechanical heterogenicity in the mammalian ovary. Recognition of the importance of special arrangements between cells has spurred research in three-dimensional culture systems, and the provision of a precise culture system that maximizes the diffusion of nutrients and gases through the follicles has raised interest in advanced biomimetic models. The current review critically examines various culture systems employed for the in vitro development of follicles, with a particular focus on solutions utilizing Organ-on-a-Chip (OOC) technology. The emphasis on OOC technology underscores its role as a promising avenue in ensuring the successful cultivation and maintenance of follicular structures during the culture period.

Comparative Tensile Properties and Collagen Patterns in Domestic Cat (Felis catus) and Dog (Canis lupus familiaris) Ovarian Cortical Tissues

The importance of the ovarian extracellular environment and tissue rigidity on follicle survival and development has gained attention in recent years. Our laboratory has anecdotally observed differences in the rigidity of domestic cat and dog ovarian cortical tissues, which have been postulated to underlie the differences in in vitro culture responses between the species, wherein cat ovarian tissues display higher survival in extended incubation. Here, the tensile strengths of cat and dog ovarian cortical tissues were compared via micropipette aspiration. The underlying collagen patterns, including fiber length, thickness, alignment, curvature, branch points and end points, and overall tissue lacunary and high-density matrix (HDM) were quantified via picrosirius red staining and TWOMBLI analysis. Finally, we explored the potential of MMP (-1 and -9) and TIMP1 supplementation in modulating tissue rigidity, collagen structure, and follicle activation in vitro. No differences in stiffness were observed between cat or dog cortical tissues, or pre- versus post-pubertal status. Cat ovarian collagen was characterized by an increased number of branch points, thinner fibers, and lower HDM compared with dog ovarian collagen, and cat tissues exposed to MMP9 in vitro displayed a reduced Young's modulus. Yet, MMP exposure had a minor impact on follicle development in vitro in either species. This study contributes to our growing understanding of the interactions among the physical properties of the ovarian microenvironment, collagen patterns, and follicle development in vitro.

Cryopreservation Competence of Chicken Oocytes as a Model of Endangered Wild Birds: Effects of Storage Time and Temperature on the Ovarian Follicle Survival

For the conservation of endangered avian species, developing gamete preservation technologies is essential. However, studies in oocytes have not been widely conducted. In this study, assuming that the ovaries are transported to a research facility after death, we investigated the effect of ovary storage on oocytes for the purpose of cryopreserving avian female gametes by using a chicken as a model of endangered avian species. After excision, the ovaries were stored at either a low temperature (4 °C) or room temperature for 1–3 days. Ovarian follicles stored under different conditions for each period were examined by neutral red staining, histology, and gene and protein expression analysis. In addition, the pH of the storage medium after preserving the ovaries was measured. Then, ovarian tissues were vitrified to determine the cryopreservation competence. Storing the ovarian tissues at 4 °C kept the follicles viable and morphologically normal for 3 days with slow decline. In contrast, although different storage temperature did not influence follicle viability and morphology after only 1 day of storage, ovarian tissues stored at room temperature rapidly declined in structurally normal follicles, and viable follicles were rarely seen after 3 days of storage. Gene and protein expression analysis showed that apoptosis had already started on the first day, as shown by the higher expression of CASP9 under room temperature conditions. Furthermore, high expression of SOD1 and a rapid decline of pH in the storage medium under room temperature storage suggested the influence of oxidative stress associated with low pH in this condition on the follicle survivability in hen ovarian tissues. Our cryopreservation study also showed that ovarian tissues stored at 4 °C could recover after cryopreservation even after 3 days of storage. The described storage conditions and cryopreservation methods, which preserve chicken follicle survival, will lay the foundation of ovarian tissue preservation to preserve the fertility of wild female birds.

Fibroblast growth factor-2 promotes in vitro activation of cat primordial follicles

This study evaluated the effect of fibroblast growth factor-2 (FGF-2) on the morphology, primordial follicle activation and growth after in vitro culture of domestic cat ovarian tissue. Ovaries (n = 12) from prepubertal domestic cats were collected and fragmented. One fragment was fixed for histological analysis (fresh control). The remaining fragments were incubated in control medium alone or with 10, 50 or 100 ng/ml FGF-2 for 7 days. After in vitro culture, the following endpoints were analyzed: morphology, activation by counting primordial and developing follicles, and growth (follicle and oocyte diameters). Treatment with 100 ng/ml FGF-2 maintained (P > 0.05) the percentage of normal follicles similar to fresh control. Follicle survival was greater (P < 0.05) after culture in 100 ng/ml FGF-2 than in 50 ng/ml FGF-2. The percentage of primordial follicles decreased (P < 0.05) and the percentage of developing follicles increased (P < 0.05) in all treatments compared with fresh tissue. The proportion of developing follicles increased (P < 0.05) in tissues incubated with 100 ng/ml FGF-2 compared with control medium and other FGF-2 concentrations. Furthermore, culture in 10 or 100 ng/ml FGF-2 resulted in increased (P < 0.05) follicle and oocyte diameters compared with fresh tissues and MEM+. In conclusion, FGF-2 at 100 ng/ml maintains follicle survival and promotes the in vitro activation and growth of cat primordial follicles.

Early preantral follicles of the domestic cat express gonadotropin and sex steroid signalling potential

Key biomolecular processes which regulate primordial ovarian follicle dormancy and early folliculogenesis in mammalian ovaries are not fully understood. The domestic cat is a useful model to study ovarian folliculogenesis and is the most relevant for developing in vitro growth methods to be implemented in wild felid conservation breeding programs. Previously, RNA-sequencing of primordial, primary, and secondary follicle samples from domestic cat implicated ovarian steroidogenesis and steroid reception during follicle development. Here we aimed to identify which sex steroid biosynthesis and metabolism enzymes, gonadotropin receptors, and sex steroid receptors are present and may be potential regulators. Differential gene expression, functional annotation, and enrichment analyses were employed and protein localisation was studied too. Gene transcripts for PGR, PGRMC1, AR (steroid receptors), CYP11A1, CYP17A1, HSD17B1 and HSD17B17 (steroidogenic enzymes), and STS (steroid metabolising enzyme) were significantly differentially expressed (Q values of ≤0.05). Differential gene expression increased in all transcripts during follicle transitions apart from AR which decreased by the secondary stage. Immunohistochemistry localised FSHR and LHCGR to oocytes at each stage. PGRMC1 immunostaining was strongest in granulosa cells whereas AR was strongest in oocytes throughout each stage. Protein signals for steroidogenic enzymes were only detectable in secondary follicles. Products of these significantly differentially expressed genes may regulate domestic cat preantral folliculogenesis. In vitro growth could be optimised as all early follicles express gonadotropin and steroid receptors meaning hormone interaction and response may be possible. Protein expression analyses of early secondary follicles supported its potential for producing sex steroids.

Influence of hydrogel encapsulation during cryopreservation of ovarian tissues and impact of post-thawing in vitro culture systems in a research animal model

Objective

Using domestic cats as a biomedical research model for fertility preservation, the present study aimed to characterize the influences of ovarian tissue encapsulation in biodegradable hydrogel matrix (fibrinogen/thrombin) on resilience to cryopreservation, and static versus non-static culture systems following ovarian tissue encapsulation and cryopreservation on follicle quality.

Methods

In experiment I, ovarian tissues (n=21 animals; 567 ovarian fragments) were assigned to controls or hydrogel encapsulation with 5 or 10 mg/mL fibrinogen (5 or 10 FG). Following cryopreservation (slow freezing or vitrification), follicle viability, morphology, density, and key protein phosphorylation were assessed. In experiment II (based on the findings from experiment I), ovarian tissues (n=10 animals; 270 ovarian fragments) were encapsulated with 10 FG, cryopreserved, and in vitro cultured under static or non-static systems for 7 days followed by similar follicle quality assessments.

Results

In experiment I, the combination of 10 FG encapsulation/slow freezing led to greater post-thawed follicle quality than in the control group, as shown by follicle viability (66.9%±2.2% vs. 61.5%±3.1%), normal follicle morphology (62.2%±2.1% vs. 55.2%±3.5%), and the relative band intensity of vascular endothelial growth factor protein phosphorylation (0.58±0.06 vs. 0.42±0.09). Experiment II demonstrated that hydrogel encapsulation promoted follicle survival and maintenance of follicle development regardless of the culture system when compared to fresh controls.

Conclusion

These results provide a better understanding of the role of hydrogel encapsulation and culture systems in ovarian tissue cryopreservation and follicle quality outcomes using an animal model, paving the way for optimized approaches to human fertility preservation.

Canid Reproductive Biology: Norm and Unique Aspects in Strategies and Mechanisms

The reproductive physiology of canids is unique compared to other mammalian species. Specifically, the reproductive cycle of female canids is characterized by extended periods of proestrus and estrus followed by obligatory diestrus and protracted ovarian inactivity (anestrus). Although canid reproduction follows this general pattern, studies have shown variations in reproductive biology among species and geographic regions. Understanding of these differences is critical to the development of assisted reproductive technologies including estrus induction, gamete rescue, and embryo production techniques for canid conservation efforts. This review summarizes current knowledge of canid reproduction, including estrus cyclicity, seasonality, and seminal traits, with the emphasis on species diversity. The application of reproductive technologies in wild canid conservation will also be discussed.

Review of non-permeating cryoprotectants as supplements for vitrification of mammalian tissues

Vitrification of mammalian tissues is important in the areas of human assisted reproduction, animal reproduction, and regenerative medicine. Non-permeating cryoprotectants (CPAs), particularly sucrose, are increasingly used in conjunction with permeating CPAs for vitrification of mammalian tissues. Combining non-permeating and permeating CPAs was found to further improve post-thaw viability and functionalities of vitrified mammalian tissues, showing the potential applications of such tissues in various clinical and veterinary settings. With the rising demand for the use of non-permeating CPAs in vitrification of mammalian tissues, there is a strong need for a timely and comprehensive review on the supplemental effects of non-permeating CPAs toward vitrification outcomes of mammalian tissues. In this review, we first discuss the roles of non-permeating CPAs including sugars and high molecular weight polymers in vitrification. We then summarize the supplemental effects of non-permeating CPAs on viability and functionalities of mammalian embryos, and ovarian, testicular, articular cartilage, tracheal, and kidney tissues following vitrification. Lastly, challenges associated with the use of non-permeating CPAs in vitrification of mammalian tissues are briefly discussed.

Reproductive biology and biotechnologies in wild felids

Conservation strategies in natural habitats as well as in breeding centers are necessary for maintaining and reinforcing viable populations of wild felids. Among the fundamental knowledge that is required for conservation breeding, a solid understanding of reproductive biology is critical for improving natural breeding and enhance genetic diversity. Additionally, it offers the opportunity to develop assisted reproductive technologies (ARTs) in threatened and endangered species. Conservation breeding and reproductive biotechnologies of wild felids have advanced in the past decade. It has been clearly shown that female felids have species and individual patterns of reproductive cycles and respond differently to exogenous hormones. In males, several species still have poor semen quality often due to the loss of genetic diversity in small populations. To overcome the challenges of natural breeding (incompatibility between individuals or suboptimal environment) and mitigate inbreeding, artificial insemination, embryo production and embryo transfer have been further developed in 24 wild cat species. Major factors limiting ART success are inconsistent responses to ovarian stimulation, variable quality of gametes and embryos, and preparation of recipient females. Additional approaches including stem cell technologies have been explored for future medical applications. However, there still is a critical need for better knowledge of feline reproductive biology and improvement of ARTs efficiency to increase the genetic diversity and create sustainable populations of wild felids.

3D printed mold leachates in PDMS microfluidic devices

The introduction of poly(dimethylsiloxane) (PDMS) and soft lithography in the 90’s has revolutionized the field of microfluidics by almost eliminating the need for a clean-room environment for device fabrication. More recently, 3D printing has been introduced to fabricate molds for soft lithography, the only step for which a clean-room environment is still often necessary, to further support the rapid prototyping of PDMS microfluidic devices. However, toxicity of most of the commercial 3D printing resins has been established, and little is known regarding the potential for 3D printed molds to leak components into the PDMS that would, in turn, hamper cells and/or tissues cultured in the devices. In the present study, we investigated if 3D printed molds produced by stereolithography can leach components into PDMS, and compared 3D printed molds to their more conventional SU-8 counterparts. Different leachates were detected in aqueous solutions incubated in the resulting PDMS devices prepared from widely used PDMS pre-polymer:curing agent ratios (10:1, 15:1 and 20:1), and these leachates were identified as originating from resins and catalyst substances. Next, we explored the possibility to culture cells and tissues in these PDMS devices produced from 3D printed molds and after proper device washing and conditioning. Importantly, we demonstrated that the resulting PDMS devices supported physiological cultures of HeLa cells and ovarian tissues in vitro, with superior outcomes than static conventional cultures.

Influence of microwave-assisted dehydration on morphological integrity and viability of cat ovarian tissues: First steps toward long-term preservation of complex biomaterials at supra-zero temperatures

Ovarian tissue contains large pools of immature oocytes enclosed in primordial follicles, making it an attractive target for fertility preservation in female cancer patients, livestock and wild species. Compared to cryopreservation, desiccation and long-term storage of samples at supra-zero temperatures (using strategies inspired from small organisms to resist extreme environments) would be more cost-effective and convenient. The objective of the study was to characterize the influence of microwave-assisted dehydration on structural and functional properties of living ovarian tissues. While this method allows preservation of single cells (cat oocytes and sperm cells so far) using trehalose as the xeroprotectant, it has not been developed for multicellular tissues yet. Ovarian cortex biopsies were reversibly permeabilized, exposed to various concentrations of trehalose, and dried for different times using a commercial microwave under thermal control. Effective dehydration of samples along with proper trehalose retention were reached within 30 min of microwave drying. Importantly, the process did not affect morphology and DNA integrity of follicles or stromal cells. Moreover, transcriptional activity and survival of follicles were partially maintained following 10 min of drying, which already was compatible with storage at non-cryogenic temperatures. Present data provide critical foundation to develop dry-preservation techniques for long-term storage of living multicellular tissues.

Supplementation of culture medium with knockout serum replacement improves the survival of bovine secondary follicles when compared with other protein sources during in vitro culture

The present study evaluated the effect of knockout serum replacement (KSR), fetal bovine serum (FBS) and bovine serum albumin (BSA) on the viability and growth of bovine secondary follicles cultured in vitro for 12 days. To this end, secondary follicles were isolated (185-202 μm) and cultured in vitro in TCM-199+ medium supplemented with KSR (5% and 10%), FBS (5% and 10%) or BSA (3 mg/ml) at 38.5°C with 5% CO2 in air. Follicular diameters were evaluated on days 0, 4, 8 and 12. After 12 days of culture, follicular survival analysis was performing by using calcein-AM and ethidium homodimer. Before and after culture, follicles were fixed in paraformaldehyde for histological evaluation. Follicular diameter at different days of culture were compared using the Kruskal-Wallis test, while the percentages of viable follicles were analyzed by chi-squared test (P < 0.05). Results showed that follicles cultured in the presence of KSR at both concentrations presented higher follicular survival rates than those cultured in control medium alone or supplemented with FBS or BSA. Conversely, the presence of KSR, BSA or FBS did not increase follicular diameter after 12 days of culture. Histology analysis showed that, among the tested treatments, follicles cultured in the presence of KSR had preserved rounded oocytes, juxtaposed granulosa cells and intact basal membrane. In conclusion, supplementation of culture medium with KSR increases the follicular survival of bovine secondary follicles cultured in vitro.

Cilostamide and forskolin maintain gap junction function of incubated dog follicles

Disruption of the communication between the oocyte and granulosa cells is one of the major causes of poor development of in vitro grown ovarian follicles and oocytes. The present study investigated the effect of two cAMP modulators, cilostamide and forskolin, on in vitro growth of isolated dog secondary follicles and enclosed oocytes, communication between the gamete and surrounding granulosa cells, expression of GJA1 and GDF9, as well as cAMP level. Secondary follicles were incubated with cilostamide or forskolin alone or a combination of 20 μM cilostamide +1 μM forskolin, and the diameter of the incubated follicles and enclosed oocytes assessed every 72 h. Gap junction activity, GJA1 and GDF9 expression and cAMP level were assessed on Days 6 and 12 and transzonal projection (TZP) density was evaluated on Day 12. Neither cilostamide nor forskolin alone enhanced in vitro growth of dog follicles and the enclosed oocytes (P > 0.05). However, these two cAMP modulators dose dependently sustained gap junction activity and stimulated cAMP production compared with the non-supplemented control. Cilostamide at the high dosage (20 μM) also upregulated GJA1 expression. The combination of cilostamide and forskolin supported oocyte growth during the first 9 days and upregulated GJA1 and GDF9 expression at Day 12 of in vitro culture. This combination treatment also sustained gap junction activity, cAMP production, and increased TZP function (calcein intensity: TZP density ratio). The findings indicated that a combination of cilostamide and forskolin supported growth and survival of oocytes enclosed within cultured follicles by sustaining cAMP production and gap junction activity.

Insulin promotes preantral follicle growth and antrum formation through temporal expression of genes regulating steroidogenesis and water transport in the cat

The aims of the present study were to determine the effects of insulin, invitro, on: (1) the viability and growth of domestic cat ovarian follicles; (2) mRNA expression of genes regulating steroidogenesis (cytochrome P450 family 17 subfamily, A polypeptide 1 (Cyp17a1), cytochrome P450 family 19 subfamily, A polypeptide 1 (Cyp19a1) and steroidogenic acute regulatory protein (Star)) and water transport (aquaporins (AQPs) Aqp1, Aqp3, Aqp7, Aqp9); and (3) steroid production (17β-oestradiol (E2), progesterone (P4), androstenedione (A4)). Cat secondary follicles were isolated from ovarian cortices and cultured in 0 (Control), 1 or 10µgmL-1 insulin for 14 days (Day 0=culture onset). Follicle and oocyte viability (based on neutral red staining), diameter and antrum formation were assessed every 72h and at the end of incubation (Day 14). Expression of steroidogenic and water transport genes was evaluated on Days 0, 6 and 12, and E2, P4 and A4 concentrations in the culture medium were determined on Day 12. By Day 14, 1 and 10µgmL-1 insulin had significantly promoted (P<0.05) both antrum formation in a mean (±s.e.m.) 26.9±9.0% and 78.0±10.0% of follicles respectively, and follicle growth (diameter 151.4±4.5 and 169.9±10.5µm respectively) compared with Control (antrum formation in 3.3±3.3% of follicles and follicle diameter 129.1±6.6µm). High insulin (10µgmL-1) treatment increased follicle viability compared with Control (86.0±9.8% vs 38.1±10.9% respectively; P<0.05). However, insulin had no beneficial effect (P>0.05) on oocyte diameter. Cyp17a1 expression on Days 6 and 12 was higher (P<0.05) in follicles cultured in the low (1µgmL-1) compared with high (10µgmL-1) insulin treatment, with no significant difference between low or high insulin vs Control groups. Star expression was higher (P<0.01) in the low insulin compared with Control group on Day 6, but Star was undetectable in the high insulin group by Day 12. Compared with high insulin, low insulin increased (P<0.05) Aqp1 expression on Day 6, but there were no significant differences between these two groups on Day 12. In contrast, high insulin decreased (P<0.05) Aqp9 transcript levels compared with Control. Only P4 production was affected by insulin, with P4 concentrations in the medium being higher (P<0.05) in the low compared with high insulin and Control groups. In summary, the findings indicate that insulin promotes cat ovarian follicle growth and survival invitro, including enhanced antrum formation, with the likely mechanism involving temporal expression of Cyp17a1, Star and Aqp9 genes.

Effect of oxygen tension on in vitro viability and development of dog follicles enclosed within the ovarian cortex

Oxygen concentration has been shown to influence in vitro viability and growth of ovarian follicles. The present study examined the effect of oxygen tension on in vitro development of dog follicles enclosed within the ovarian cortex. Ovaries were obtained from domestic dogs (age, 8 months to 2 years), and cortical fragments were recovered. The cortices were then incubated on 1.5% (w/v) agarose gel blocks within a 4-well culture plate containing Eagle Minimum Essential Medium (MEM). Ovarian follicles within the tissues were processed for histology and assessed for follicle density, viability and diameter immediately after collection (Control) or after 2 or 5 days of in vitro incubation. Apoptotic cells were assessed using TUNEL assay. Comparisons of follicular viability and diameter were performed using analysis of variance followed by Tukey's test (p < 0.05). Comparisons of follicle density and apoptosis among treatments were conducted using Non-parametric Kruskal-Wallis test followed by Friedman's test (p < 0.05). No difference (p > 0.05) in follicle density was observed among groups at Day 2 of in vitro culture. However, the density of follicles within cortices cultured in 20% oxygen for 5 days significantly reduced compared to the Control and those incubated in 5% concentration. The viability of cultured follicles in all treatments decreased (p < 0.05) compared to the Control after 2 days incubation, and this value further reduced (p < 0.05) in 20% oxygen group at Day 5. There were no differences in the percentages of apoptotic follicles between the two treatment groups (p > 0.05). Nevertheless, after 5 days of culture, the percentage of TUNEL-positive follicles increased significantly (p < 0.05) in cortices incubated in 20% oxygen environment. In conclusion, our findings demonstrated that 5% oxygen level was superior to 20% concentration in sustaining in vitro viability of dog follicles enclosed within the ovarian cortex.

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.

INFLUÊNCIA DO HEPES NA MATURAÇÃO IN VITRO DE OÓCITOS CANINOS OBTIDOS DE CADELAS EM DIESTRO E ANESTRO

Resumo Diferentemente de outras espécies domésticas, a maturação in vitro (MIV) de oócitos caninos apresenta sucesso limitado. O objetivo deste estudo foi avaliar o efeito do HEPES na maturação in vitro de oócitos caninos obtidos de cadelas em diestro e anestro. Os ovários foram coletados, isolados assepticamente e transportados refrigerados a uma temperatura de 4 ºC. Os complexos cumulus-oócito (CCOs), provenientes das duas fases do ciclo estral, foram submetidos a dois tratamentos: meio TCM-199 com adição de 25 mM de HEPES (GT) e meio sem suplementação (GC). Depois de 72 horas de maturação, os CCOs foram desnudados, fixados e corados com HOESCHT 33342 para avaliação da maturação nuclear. Os oócitos obtidos da fase de anestro e diestro do GT demonstraram, em relação ao grupo GC, maior frequência de oócitos nos estágios de M-II (p<0,01). Comparando-se os diferentes status reprodutivos, observou-se que os oócitos obtidos da fase de diestro apresentaram índices maiores de QVG e M-II. Nossos resultados demonstraram que o HEPES preserva a viabilidade e morfologia oocitária, indispensáveis para a aquisição da competência meiótica, potencializando as taxas de M-II, e que os oócitos obtidos da fase de diestro estão mais aptos a completarem a maturação oocitária.

Effect of EGF on expression and localization of maturation-promoting factor, mitogen-activated protein kinase, p34cdc2 and cyclin B during different culture periods on in vitro maturation of canine oocytes

This study aimed to investigate the localization of MPF, MAPK, p34^cdc2 and cyclin B1 proteins, before and after treatment with EGF during different moments of oocyte maturation. The ovaries obtained from 350 domestic dogs were aseptically isolated, immersed in physiological solution and transported at 4°C. In the laboratory, the ovaries were sectioned for the release of cumulus-oocyte complexes. Cumulus-oocyte complexes were selected and divided into treatment groups with and without EGF and cultured for 24, 48 and 72 hr. Immunofluorescence was used for the detection and the localization of MAPK, MPF, p34^cdc2 and cyclin B1 proteins. We observed that the expression and localization of MPF, MAPK, p34^cdc2 and cyclin B1 proteins are associated with meiosis resumption and cell cycle progression, and that EGF influences cell signalling pathways by promoting alterations in the localization of these proteins, improving the acquisition of oocyte competence. This is the first report of the localization of crucial proteins for meiosis progression in domestic dogs and identification of the expression and localization of proteins for cell cycle progression performed in this study represented a step of great importance to elucidate the mechanisms involved in the meiosis block in domestic dogs, allowing the advance in this research area.

Effect of anti-apoptotic drug Z-VAD-FMK on in vitro viability of dog follicles

It is recognized that ovarian follicular atresia is associated with apoptosis, and the most important effector of cell death is caspase-3. The aim of this study was to investigate the influence of anti-apoptotic drug Z-VAD-FMK on in vitro follicle growth in the domestic dog. Ovaries were obtained from peri-pubertal and adult domestic dogs, and cortical fragments recovered and incubated on 1.5% (w/v) agarose gel blocks within a 24-well culture plate containing Minimum Essential Medium Eagle-Alpha Modification (αMEM) supplemented with 4.2 μg/mL insulin, 3.8 μg/mL transferrin, 5 ng/mL selenium, 2 mM L-glutamine, 100 μg/mL of penicillin G sodium, 100 μg/mL of streptomycin sulfate, 0.05 mM ascorbic acid, 10 ng/mL of FSH and 0.1% (w/v) polyvinyl alcohol in humidified atmosphere of 5% CO₂ and 5% O₂. The cortices were randomly allocated in six treatments: 1) 10 ng/mL EGF (EGF V0); 2) 10 ng/mL of EGF plus 1 mM Z-VAD-FMK (EGF V1); 3) 10 ng/mL of EGF and 10 mM Z-VAD-FMK (EGF V10); 4) 1 mM Z-VAD-FMK; 5) 10 mM Z-VAD-FMK and (6) no EGF and Z-VAD-FMK supplementation (Control). The cortices were processed for histology and assessed for viability (based on morphology), density of structurally normal follicles, and diameter immediately after collection (non-culture Control) or after 3 or 7 days of in vitro incubation. Evaluation of mRNA expression of Cas3 in fresh cortices and those incubated for 3 days was performed using real-time PCR. Histological analysis revealed that in vitro incubation decreased (P < 0.05) follicle viability and density compared to the fresh, non-culture control. Addition of 10 μM of Z-VAD-FMK alone to the culture medium sustained follicle viability at Day 3, but did not impact follicle diameter when compared to the other treatment groups (p < 0.001); however, the beneficial benefit of this anti-apoptotic drug diminished after 7 days of incubation. Furthermore, Z-VAD-FMK supplementation did not impact Cas3 expression. The findings demonstrated that dog ovarian tissues are highly susceptible to in vitro incubation and Z-VAD-FMK supported short-term survival of dog follicles enclosed within the ovarian cortex.

Retinoic acid promotes in vitro follicle activation in the cat ovary by regulating expression of matrix metalloproteinase 9

Retinoic acid (RA) facilitates tissue morphogenesis by regulating matrix matalloproteinase (MMPs) expression. Our objective was to examine the influence of RA on in vitro development of follicles enclosed within domestic cat ovarian tissues. Ovarian cortices from 9 prepubertal and 13 adult cats were incubated for 7 d in medium containing 0 (control), 1 or 5 μM RA and then analyzed for viability. Cortices from additional three animals of each age group were cultured in the same condition and follicle morphology, stage and size were histologically evaluated. In a separate study, cortices from 14 donors (7 prepubertal; 7 adult cats) were incubated in 0 or 5 μM RA for 7 d and assessed for (1) MMP1, 2, 3, 7, 9 and TIMP1 expression by qPCR and (2) protein expression of MMP9 by immunohistochemistry. Donor age did not influence follicle response to RA. Collective data from both age groups revealed that percentages of primordial follicles in 5 μM RA treatment were lower (P < 0.05; 40.5 ± 4.5%) than in fresh cortices (66.7 ± 5.3%) or controls (60.1 ± 4.0%) with 1 μM-RA treatment producing intermediate (56.3 ± 4.0%) results. Proportion of primary follicles in 5 μM RA (21.7 ± 3.3%) was higher than in fresh cortices (4.9 ± 2.9%) and controls (9.0 ± 2.8%) with 1 μM-RA treatment producing an intermediate value (13.8 ± 2.0%). Furthermore, proportion of secondary follicles increased after 7 d in the presence of 5 μM RA (9.5 ± 2.7%) compared to other groups (fresh, 1.9 ± 0.8%; control, 2.6 ± 1.1%; 1 μM RA, 2.5 ± 0.2%). MMP9 transcript and protein were upregulated, whereas MMP7 mRNA was suppressed by 5 μM-RA treatment compared to fresh counterparts. RA did not impact MMP1, 2, 3, 13 or TIMP1 expression. In summary, RA activated cat primordial follicle growth likely via a mechanism related to upregulation of MMP9 and down-regulation of MMP7 transcripts.

Evaluation of an ovary-on-a-chip in large mammalian models: Species specificity and influence of follicle isolation status

The ability to grow oocytes from immature ovarian follicles in vitro has significant potential for fertility preservation; yet, it has proved challenging in large mammalian species due to the complex metabolic needs and long-term culture requirements. Currently, follicular incubations are based on a "static" system with manual exchange of medium. Despite the numerous advantages of conventional culturing approaches, recapitulating the native microenvironment and supporting the survival of ovarian follicles from large mammalian species still represent challenges. In this study, we utilized an innovative, dynamic microfluidic system to support the in vitro survival of domestic cat and dog follicles enclosed within the ovarian cortex or isolated from ovarian cortex. Results indicate both species-specific and tissue type-specific differences in response to microfluidic culture. Domestic cat but not dog ovarian cortical tissues maintained viability under flow similar to conventional agarose gel controls. Preantral stage isolated follicles from both species that grew most favourably in conventional alginate bead culture, but overall, there was no influence of culture system on expression of follicle development or oocyte health markers. This system represents an important exploration toward the development of an improved ovarian in vitro culture system of large mammalian species (e.g., cats and dogs), which has potential applications for fertility preservation, reproductive toxicology, and endangered mammal conservation efforts.

In vitro production of Sudanese camel (Camelus dromedarius) embryos from epididymal spermatozoa and follicular oocytes of slaughtered animals

Application of assisted reproductive technology in camelidea, such as artificial insemination (AI) and embryo transfer, has been slow in comparison to that for other livestock species. In Egypt, there are few attempts to establish in vitro maturation (IVM) and fertilization (IVF) techniques in dromedary camel. The present study was carried out to produce Sudanese camel embryos using in vitro matured oocytes and epididymal spermatozoa. Dromedary camel ovaries were collected from abattoirs and then, the oocytes were aspirated from all the visible follicles on the ovarian surface (~2-8 mm in a diameter). Meanwhile, Fetal Dromedary Camel Serum (FDCS) was obtained from camel fetuses after slaughtering. Thereafter, only Cumulus Oocyte Complexes (COCs) were matured in vitro in the Tissue Culture Medium (TCM-199) complemented with 10% FDCS. Spermatozoa required for in vitro fertilization were collected from testes (epididymal cauda) of the slaughtered camel bulls. The results clearly showed that the maturation rate of oocytes at metaphase II was about 59.5% while the fertilization rate was around 70.4%. Intriguingly, the embryo rates determined were 13.1%, in 2-cell; 0.0%, in 4-cell; 34.7%, in 8-16% cell; 39.1%, in morula and 13.1% in a blastocyst stage. This study represented a successful in vitro production of Sudanese dromedary camel embryos from epididymal sperm cells and in vitro matured oocytes recovered from slaughtered camels.

Stem cell factor promotes in vitro ovarian follicle development in the domestic cat by upregulating c-kit mRNA expression and stimulating the phosphatidylinositol 3-kinase/AKT pathway

In the present study we examined the effects of stem cell factor (SCF; 50 vs 100 ng mL–1) alone or in combination with epidermal growth factor (EGF; 100 ng mL–1) on: (1) the in vitro viability and growth of cat follicles within ovarian cortices; (2) phosphatidylinositol 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK) phosphorylation; and (3) c-kit and FSH receptor (FSHr) mRNA expression. At 100 ng mL–1, SCF increased (P ≤ 0.05) the percentage and size of secondary follicles after 14 days of in vitro culture and sustained AKT phosphorylation after 3 days incubation. EGF suppressed this beneficial effect and reduced (P ≤ 0.05) the percentage of structurally normal follicles and FSHr expression when combined with 100 ng mL–1 SCF. Expression of c-kit mRNA was higher (P ≤ 0.05) in the presence of 100 ng mL–1 SCF compared with fresh follicles and cohorts cultured under other conditions. A c-kit inhibitor suppressed follicle growth and reduced AKT phosphorylation. Collectively, the results demonstrate that SCF promotes cat follicle development by upregulating c-kit mRNA expression and AKT phosphorylation. EGF suppresses the stimulating effect of SCF, leading to downregulation of FSHr expression.

A three-dimensional alginate system for in vitro culture of cumulus-denuded feline oocytes

In the case of high valuable individuals with very precious genetic material, widening the genetic pool including gametes with poor morphological characteristics, as cumulus-denuded oocytes (CDOs), could be an option. To improve the in vitro culture of low-competence feline CDOs, an enriched three-dimensional (3D) system in association with competent cumulus-oocyte complexes (COCs) was developed. For this purpose, domestic cat CDOs were cultured with or without companion COCs in the 3D barium alginate microcapsules. The overall viability and the meiotic progression of feline CDOs cocultured with COCs or cultured separately in 3D or in 2D (traditional microdrops) system were compared. The 3D system was able to support viability and meiotic resumption of the feline oocytes, as well as the 2D microdrops. In 3D microcapsules, the presence of COCs resulted in a higher viability of CDOs (91.1%, p < .05), than that obtained without COCs or in 2D microdrops (71.2% and 67.3%, respectively), but the percentages of meiotic resumption were similar of those of CDOs cultured separately (55.4% vs. 40.4%, p > .05). It is notable that the presence of CDOs seemed to enhance the meiotic progression of the associated COCs. In conclusion, the 3D barium alginate microcapsules are a suitable system for feline oocytes in vitro culture, but more specific enriched conditions should be developed to improve the CDOs full competence in vitro.

Carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) pre-exposure ensures follicle integrity during in vitro culture of ovarian tissue but not during cryopreservation in the domestic cat model

PURPOSE

Temporary and reversible downregulation of metabolism may improve the survival of tissues exposed to non-physiological conditions during transport, in vitro culture, and cryopreservation. The objectives of the study were to (1) optimize the concentration and duration of carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP-a mitochondrial uncoupling agent) exposures for biopsies of domestic cat ovarian tissue and (2) examine the effects of FCCP pre-exposures on follicle integrity after tissue culture and/or cryopreservation.

METHODS

Biopsies of cat ovarian tissue were first treated with various concentrations of FCCP (0, 10, 40, or 200 nM) for 10 or 120 min to determine the most suitable pre-exposure conditions. Based on these results, tissues were pre-exposed to 200 nM FCCP for 120 min for the subsequent studies on culture and cryopreservation. In all experiments and for each treatment group, tissue activity and integrity were measured by mitochondrial membrane potential (relative optical density of rhodamine 123 fluorescence), follicular viability (calcein assay), follicular morphology (histology), granulosa cell proliferation (Ki-67 immunostaining), and follicular density.

RESULTS

Ovarian tissues incubated with 200 nM FCCP for 120 min led to the lowest mitochondrial activity (1.17 ± 0.09; P < 0.05) compared to control group (0 nM; 1.30 ± 0.12) while maintaining a constant percentage of viable follicles (75.3 ± 7.8 %) similar to the control group (71.8 ± 11.7 %; P > 0.05). After 2 days of in vitro culture, percentage of viable follicles (78.8 ± 8.9 %) in similar pre-exposure conditions was higher (P < 0.05) than in the absence of FCCP (61.2 ± 12.0 %) with percentages of morphologically normal follicles (57.6 ± 17.3 %) not different from the fresh tissue (70.2 ± 7.1 %; P > 0.05). Interestingly, percentages of cellular proliferation and follicular density were unaltered by the FCCP exposures. Based on the indicators mentioned above, the FCCP-treated tissue fragments did not have a better follicle integrity after freezing and thawing.

CONCLUSIONS

Pre-exposure to 200 nM FCCP during 120 min protects and enhances the follicle integrity in cat ovarian tissue during short-term in vitro culture. However, FCCP does not appear to exert a beneficial or detrimental effect during ovarian tissue cryopreservation.

The preservation of vital functions in cat ovarian tissues during vitrification depends more on the temperature of the cryoprotectant exposure than on the sucrose supplementation

The objective of this study was to better characterize the impact of cryoprotectant exposure (temperature and sucrose supplementation) on the health and function of preantral follicles in ovarian tissues during vitrification using the domestic cat model. Ovarian cortical pieces from peri-pubertal individuals were exposed to cryoprotectants at 4 °C or room temperature and supplemented with 0 or 0.5 M of sucrose, followed by vitrification. After rapid warming, cortical pieces were cultured in vitro and assessed for normal follicular morphology, viability and resumption of transcriptional activities for up to 7 days. Throughout the culture period, follicular morphology (up to 67.5% normal follicles) and global RNA transcription (up to 50.9% follicles with transcriptional activity) in warmed tissues were improved by cryoprotectant exposure at 4 °C compared to room temperature, but viability (up to 84.6% viable follicles) did not seem to be affected by exposure temperature. Sucrose supplementation did not have a consistent effect as it increased RNA transcription but decreased normal follicular morphology. For the first time, the study demonstrated that the preservation of critical tissue functions, such as the transcriptional activities, highly depends on the temperature of the cryoprotectant exposure and not necessarily on the presence of sucrose.

Female fertility preservation strategies: cryopreservation and ovarian tissue in vitro culture, current state of the art and future perspectives

In the present review, the main strategies of female fertility preservation are covered. Procedures of fertility preservation are necessary for women who suffer from diseases whose treatment requires the use of aggressive therapies, such as chemotherapy and radiotherapy. These kinds of therapy negatively influence the health of gametes and their progenitors. The most commonly used method of female fertility preservation is ovarian tissue cryopreservation, followed by the retransplantation of thawed tissue. Another approach to female fertility preservation that has been actively developed lately is the ovarian tissue in vitro culture. The principal methods, advantages and drawbacks of these two strategies are discussed in this article.

Felis catus ovary as a model to study follicle biology in vitro

PURPOSE

The current study was designed to evaluate the response of individual intact antral follicles from adult female domestic cats to a luteinizing hormone (LH) stimulus in vitro by assessing cumulus-oocyte expansion (C-OE) and steroid production.

METHODS

C-OE and steroid levels (estradiol [E2] and progesterone [P4]) obtained from individual antral feline follicles (n = 366 follicles; n = 56 cats) were analyzed after 12 or 24 h of culture in the presence or absence of LH (low [3.4 ng/ml] or high [100 ng/ml]).

RESULTS

At the end of the culture, the highest percentage of expanded cumulus-oocyte complexes (COCs) was observed in the LH groups at 12 or 24 h in comparison to their controls (p < 0.001). There was a significant increase in expanded COCs when comparing LH concentrations (high vs. low) at 12 or 24 h. Higher levels of both E2 and P4 were observed in the media from antral follicles after 12 and 24 h of culture in the presence of LH (both concentration, p < 0.05). There was no association between hormone levels and follicle diameter; high variability was observed in the steroid levels produced by antral follicles within all treatment groups.

CONCLUSIONS

These data indicate, for the first time, that feline antral follicles (0.5-2 mm) from different stages of the natural estrous cycle can be cultured and will respond to an LH stimulus, based on an increase in steroid levels as well as C-OE after 12 or 24 h in culture.

The domestic dog and cat as models for understanding the regulation of ovarian follicle development in vitro

The culture of ovarian follicles is an important tool for understanding the mechanisms controlling follicle development and differentiation of the oocyte. The benefit of recovering meiotically and developmentally competent oocytes from early stage follicles (primordial, primary, pre-antral and early antral) also would be significant, ranging from rescue of genomes from endangered species to preserving fertility in women facing cancer treatments. This research field is at an early stage of scientific discovery. To-date, live offspring from cultured primordial follicles that produced fertilizable oocytes has occurred only in the mouse. Progress in other more complex species has been limited because larger animals have longer durations of natural folliculogenesis, thereby requiring more culture time to generate fully grown follicles and oocytes. We believe the dog and cat are excellent models for understanding more about folliculogenesis in vitro. This review highlights what is known about this topic for these two species as well as future priorities. We have discovered that it is more challenging to maintain viability of primordial follicles within ovarian tissues in vitro in the dog than the cat. Nonetheless, it is possible to grow both isolated cat and dog pre-antral follicles in culture. Although the follicles of both species have the capacity to increase in size and produce steroids, only cat oocytes appear morphologically normal. The reason for this striking difference between these two species is an area of high research priority. While much more fundamental data are required, we envision advanced technology that will allow harvesting oocytes from the vast, unused follicle stores sequestered within carnivore ovaries. These gametes have utility for reproducing genetically valuable dogs and cats that are 'companions' or biomedical models for investigating human disorders as well as for salvaging the genomes of rare canid and felid species that die before contributing to genetic management programs.