Morphological and ultrastructural analysis of sheep primordial follicles preserved in 0.9% saline solution and TCM 199

Efficiency of mannitol-supplemented medium during adding/removing ovarian tissue with penetrating cryoprotective agents

Most protocols to cryopreserve ovarian tissue utilize the permeable cryoprotective agents (CPAs) in 1.5 M concentration. However the issues related to the ability to use higher concentrations of CPAs have remained open. The research aim was to assess the efficiency of media containing osmotically active sugars (sucrose, mannitol) at stepwise adding/removing of 3 M dimethylsulphoxide (DMSO) and propanediol (PROH) on ovarian tissue integrity. After the CPAs adding/removing the ovarian tissue injury was histologically examined, as well as the oocyte volume in tissue structure was assessed. It has been found, that after adding/removing of PROH and DMSO solutions the maximum amount of normal follicles made 67-93% when using Dulbecco's Modified Eagle Medium (DMEM) with 200 mM sucrose. Assessment of tissue damage after adding/removing of CPAs has demonstrated that the percentage of normal follicles was 83-87% using DMSO in presence of both sucrose and mannitol as the dilution media components. While removing PROH the level of follicles preservation was 2.5× higher when using mannitol compared with sucrose. Our results indicate that the ovarian tissue injury was minimal during adding 3 M CPAs using DMEM, containing sucrose and following application of mannitol at removing both DMSO and PROH.

Ovarian fragment sizes affect viability and morphology of preantral follicles during storage at 4°C

The method of transportation and the conditions imposed on the ovarian tissue are pivotal aspects for the success of ovarian tissue cryopreservation (OTC). The aim of this study was to evaluate the effect of the size of the ovarian tissue (e.g. whole ovary, biopsy size and transplant size) during different times of storage (0, 6, 12 and 24 h) on the structural integrity of equine ovarian tissue transported at 4°C. Eighteen pairs of ovaries from young mares (<10 years old) were harvested in a slaughterhouse and processed to simulate the fragment sizes (biopsy and transplant size groups) or kept intact (whole ovary group) and stored at 4°C for up to 24 h in α-MEM-enriched solution. The effect of the size of the ovarian tissue was observed on the morphology of preantral follicles, stromal cell density, DNA fragmentation and mitochondrial membrane potential. The results showed that (i) biopsy size fragments had more morphologically normal preantral follicles after 24 h of storage at 4°C; (ii) mitochondrial membrane potential was the lowest during each storage time when the whole ovary was used; (iii) DNA fragmentation rate in the ovarian cells of all sizes of fragments increased as storage was prolonged and (iv) transplant size fragments had increased stromal cell density during storage at cool temperature. In conclusion, the biopsy size fragment was the best to preserve follicle morphology for long storage (24 h); however, transportation/storage should be prior determined according to the distance (time of transportation) between patient and reproduction centers/clinics.

Morphometric and Ultrastructure studies of Primordial Follicles and Expression of Estrogen-dependent Genes in the Ovaries of Domestic Cats

The aim of this study was to compare and estimate the population of the primordial follicle morphometrically and ultrastructurally in the left and right side ovaries of 10 ovariohysterectomied healthy domestic shorthair cats. The ovaries were processed for light microscopy, electron microscopy, and estrogen-dependent gene expression for assessments. A total of 15,092 primordial follicles with and without a nucleus were examined and counted. A total of 6842 primordial follicles with a nucleus were examined and counted. The light-microscopy numerical data were collected from two histological sections per ovary for a total of 20 sections from the left ovary and 20 sections from the right ovary. The average surface area of the histological sections was 645.99 mm². The number of tertiary follicles was found to be higher in the left ovaries than in the right ovaries. The primordial follicles are under the tunica albuginea at various levels. Some are crowded or scattered in one or two rows, although at times, there were areas without any primordial follicles. The primordial follicles varied in size, and were surrounded by 4–10 squamous granulosa cells. Some primordial follicles shared their ooplasm with one or two neighboring primordial follicles, forming a giant primordial follicle with two or three nuclei. The ultrastructure of the primordial follicles showed rounded nuclei with distinct nucleoli, rounded and elongated mitochondria, and a considerably thick basement membrane under the granulosa cells. The squamous granulosa cells showed well-developed microvilli intermingled with the microvilli of the oocyte oolemma. Elongated mitochondria, coated pits, multicytoplasmic vesicles, ribosomes, and Golgi apparatuses were obvious in the oocyte ooplasm. Large vesicles contain small multivesicles and some scattered lipid globules in the ooplasm. There were estrogen-dependent gene-expression differences between the right and left ovaries. Further gene research is in the plan, using a larger pool of cats, with a focus on age differences.

Lower apoptosis rate in ovine preantral follicles from ovaries stored in supplemented preservation media

The aim of this study was to investigate the effect of ovarian tissue transportation conditions (medium and period of time) on the morphology, apoptosis and development of ovine preantral follicles cultured in vitro. Each ovarian pair was cut into nine slices, with one fragment being fixed immediately (fresh control). The remaining fragments were placed individually in cryotubes containing conservation medium (minimal essential medium (MEM) without supplementation or MEM+ - with supplementation) and stored at 35ºC for 6 or 12 h without (non-cultured) or with subsequent culture for 5 days. Then, the fragments were processed for histological and terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick-end labelling (TUNEL) examination. Preservation of ovarian slices in MEM or MEM+ (non-cultured) resulted in similar percentages of normal follicles when compared with the fresh control. Nevertheless, compared with the fresh control, a decrease in the percentage of normal follicles was observed in tissues cultured for 5 days. Only for tissues preserved in supplemented medium (MEM+) for 6 h, the percentage of TUNEL positive cells was similar between non-cultured tissues and tissues cultured for 5 days. Follicular activation and growth (follicular and oocyte diameter) were higher in cultured tissues than in fresh control or non-cultured tissues, except those from fragments preserved for 6 h in MEM and then cultured for 5 days in which no growth was observed. In conclusion, ovine ovarian tissue was successfully preserved in supplemented medium (MEM+) at a temperature close to physiological values (35°C) for up to 6 h without affecting apoptosis in the ovarian follicles and their ability to develop in vitro.

Immunohistochemical localization of fibroblast growth factor-2 in the sheep ovary and its effects on pre-antral follicle apoptosis and development in vitro

Studies with sheep are important to improve our knowledge about the factors that control folliculogenesis in mammals and to explore possible physiological differences among species. The aims of this study were to characterize FGF-2 protein expression in ovine ovaries and to verify the effect of FGF-2 on the morphology, apoptosis and growth of ovine pre-antral follicles cultured in vitro. After collection, one fragment of ovarian tissue was fixed for histological analysis and TUNEL analysis (fresh control). The remaining fragments were cultured for 7 days in control medium (α-MEM(+) ) alone or supplemented with FGF-2 at different concentrations (1, 10, 50, 100 or 200 ng/ml). After culturing, ovarian tissue was destined to histology and TUNEL analysis, and oocyte and follicle diameters were measured. The immunostaining for FGF-2 was observed in oocytes from primordial, primary and secondary follicles, as well as in granulosa cells of secondary and antral follicles. The percentage of normal follicles was similar among control medium, 1 and 10 ng/ml FGF-2, and significantly higher than those observed in 50, 100 or 200 ng/ml FGF-2. A significant increase in follicle diameter was observed when tissues were cultured in 10, 50, 100 or 200 ng/ml FGF-2 compared with the fresh control and the other treatments. Similar results were observed for oocyte diameter in tissues cultured with 50, 100 or 200 ng/ml FGF-2 (p < 0.05). However, the percentage of apoptotic cells only decreased (p < 0.05) in ovarian tissues cultured in 1 or 10 ng/ml FGF-2 compared with the control medium and other FGF-2 treatments. In conclusion, this study demonstrated the presence of FGF-2 in ovine ovaries. Furthermore, 10 ng/ml FGF-2 inhibits apoptosis and promotes ovine follicle growth. As the sheep ovary is more similar to that of humans, the culture system demonstrated in this work seems to be an appropriate tool for studies towards human folliculogenesis.

Vitreous cryopreservation of human preantral follicles encapsulated in alginate beads with mini mesh cups

To completely avoid ice crystal formation and thus get a higher survival rate, vitrification methods have been commonly used for cryopreservation of oocytes and embryos. However, currently used vitrification methods for oocytes and embryos are not suitable for the cryopreservation of preantral follicles (PFs). In the present study, stainless steel mesh was fabricated into mini mesh cups to vitrify isolated PFs. Moreover, isolated follicles were encapsulated and then subjected to vitreous cryopreservation to facilitate in vitro culture/maturation of follicles after warming. The results showed that the percentages of viable follicles did not differ significantly between the vitrification group and fresh group soon after warming (81.25% vs. 85.29%, P>0.05) and after a 7-day culture period (77.78% vs. 83.33%, P>0.05). No difference in mean follicular diameter was observed between cryopreserved and fresh follicles when cultured in vitro. Transmission electron microscopic analysis revealed that vitreous cryopreservation could maintain the ultrastructure of follicles in alginate beads. In conclusion, the present vitrification method could efficiently cryopreserve isolated human ovarian follicles encapsulated by calcium alginate, which could be put into immediate use (in vitro culture/ maturation) after warming. However, more follicles and some detailed biochemical analyses are required to further investigate the effects of vitrification on the long-term growth of human encapsulated PFs.

Ultrastructure of Sheep Primordial Follicles Cultured in the Presence of Indol Acetic Acid, EGF, and FSH

The aim of this study was to investigate the ultrastructural characteristics of primordial follicles after culturing of sheep ovarian cortical slices in the presence of indol acetic acid (IAA), Epidermal Growth Factor (EGF), and FSH. To evaluate ultrastructure of primordial follicles cultured in MEM (control) or in MEM containing IAA, EGF, and FSH, fragments of cultured tissue were processes for transmission electron microscopy. Except in the control, primordial follicles cultured in supplemented media for 6 d were ultrastructurally normal. They had oocyte with intact nucleus and the cytoplasm contained heterogeneous-sized lipid droplets and numerous round or elongated mitochondria with intact parallel cristae were observed. Rough endoplasmic reticulum (RER) was rarely found. The granulosa cells cytoplasm contained a great number of mitochondria and abundant RER. In conclusion, the presence of IAA, EGF, and FSH helped to maintain ultrastructural integrity of sheep primordial follicles cultured in vitro.

Short-term preservation of canine preantral follicles: Effects of temperature, medium and time

The use of the large pool of preantral follicles is a promising alternative to provide high numbers of fertilizable oocytes to reproductive biotechnology. This issue is particularly important to canids, since current rates of success of in vitro techniques using oocytes are very limited, and many species within this family are threatened by extinction. The aim of this study was to evaluate effects of temperature, medium and time on morphology and viability of canine preantral follicles during short-term preservation. Canine ovaries were cut into fragments which were incubated in 0.9% NaCl solution or in minimum essential medium (MEM) at 4, 20 or 38 degrees C for 2, 6, 12 or 24 h. Afterwards, preantral follicles were analyzed by histology, transmission electron microscopy and viability testing using trypan blue, calcein-AM and ethidium homodimer-1. Percentages of morphological normal and viable follicles were maintained similar to control (time 0 h) after incubation in 0.9% NaCl at 4 or 20 degrees C for up to 6h and at 38 degrees C for 2 h. Using MEM, such preservation was possible for 12h at 4 or 20 degrees C, and for 6h at 38 degrees C. These results indicate that preservation of canine preantral follicles might be better accomplished through hypothermic (4 or 20 degrees C) storage in MEM, which ensures maintenance of morphology and viability for up to 12h.

Chilling ovarian fragments during transportation improves viability and growth of goat preantral follicles cultured in vitro

The aim of the present study was to evaluate the effects of storage of goat ovarian fragments at different temperatures and for different incubation times on the viability and growth of cultured preantral follicles in vitro. Caprine ovaries were collected and divided into 19 fragments, with one fragment being fixed immediately (fresh control). The remaining fragments were placed in minimal essential medium (MEM) and maintained at 4, 20 or 35°C for 2 or 4 h. After each incubation period, some of the fragments were fixed (non-cultured), whereas others were cultured in vitro for 1 or 7 days. Fragments were processed to enable routine histological and transmission electron microscopic examination. After 7 days of culture, only ovarian fragments stored at 4°C for 4 h maintained a percentage of morphologically normal follicles similar to that in the fresh control. For all other treatments groups, there was a significant increase in follicular activation observed. In addition, there was an increase in oocyte and follicular diameter after culture of ovarian cortex that had been chilled previously at 4°C for 2 or 4 h. In conclusion, the present study demonstrated that chilling ovarian fragments at 4°C during transportation is best for maintaining follicle viability and to increase follicular growth during in vitro culture.

Conservação de folículos pré-antrais bovinos em solução salina 0,9% ou TCM 199

Investigou-se a eficiência da solução salina 0,9% (SS) e TCM 199 na conservação de folículos pré-antrais (FOPA) bovinos in situ em diferentes temperaturas e tempos de incubação. Cada par ovariano foi dividido em 25 fragmentos. Um fragmento foi escolhido aleatoriamente e fixado imediatamente após a coleta (controle). Os demais foram distribuídos em tubos contendo SS ou TCM 199 a 4, 20 ou 39ºC por 2, 4, 12 ou 24h. A análise histológica mostrou que a conservação a 4ºC em ambas as soluções manteve a porcentagem de FOPA normais similar ao controle. A conservação em SS a 20ºC por 12 ou 24h, TCM 199 a 20ºC por 24h e em ambas as soluções a 39ºC a partir de 2h aumentou (P<0,05) a porcentagem de FOPA degenerados comparada à porcentagem de folículos-controle. Em ambas as soluções, independente do tempo de incubação, a porcentagem de folículos normais, após conservação a 39ºC, foi (P<0,05) menor que a obtida com 4 e 20ºC. FOPA bovinos podem ser conservados eficientemente a 4ºC por até 24h em ambas as soluções, e a 20ºC por 4 e 12h em SS e TCM 199, respectivamente.

Histological and ultrastructural analysis of cryopreserved sheep preantral follicles

The aim of this study was to verify the histological and ultrastructural characteristics of sheep preantral follicles after exposure of ovarian tissue to cryopreservation in glycerol (GLY), ethylene glycol (EG), propanediol (PROH) or dimethyl sulfoxide (DMSO) in order to determine the optimum method to store sheep ovarian tissue for later experimental or clinical use. Each ovarian pair from five mixed-breed ewes was divided into 17 fragments. One (control) fragment was immediately fixed for routine histological and ultrastructural studies and the remaining (test) fragments were randomly distributed in cryotubes, equilibrated at 20 degrees C/20 min in 1.8 mL of minimal essential medium (MEM) containing 1.5 or 3 M GLY, EG, PROH or DMSO and then either fixed for morphological studies to determine their possible toxic effect or frozen/thawed and then fixed to test the effect of cryopreservation on preantral follicles. Histological analysis showed that, compared to control fragments, all cryoprotectants at both concentrations significantly reduced the percentage of normal preantral follicles in ovarian fragments prior to or after cryopreservation. PROH 3.0 M appeared to exert a more toxic effect (P<0.05) than the other cryoprotectants in noncryopreserved tissues. After freezing/thawing, the highest (P<0.05) percentages of lightmicroscopical normal preantral follicles were observed in ovarian fragments cryopreserved in EG (1.5 and 3 M) or DMSO (1.5 M). However, transmission electronic microscopical (TEM) examination showed that only the DMSO-cryopreserved preantral follicles had normal ultrastructure. The data suggest that sheep preantral follicles should be cryopreserved with 1.5 M DMSO for later clinical or experimental application.