Effects of vitrification procedures on subsequent development and ultrastructure of in vitro-matured swamp buffalo (Bubalus bubalis) oocytes

Effect of ovarian growth factors on ultra-structural maturation in frozen human immature oocytes after in vitro maturation: a comparative study

BACKGROUND

In artificial reproductive technique (ART), nearly 20% of human oocytes are immature in the germinal vesicle (GV) phase. Consequently, the best method for reserving them is cryopreserving GV oocytes, and in vitro maturation (IVM) is recommended. The aim of this study was to determine the ultrastructure characteristics of fresh and vitrified immature human oocytes after in vitro maturation in conditioned mediums.

METHODS

This study was a comparative laboratory study carried out in 2018 at Afzalipur Infertility Center in Kerman. 170 fresh and 198 vitrified GV oocytes were cultured within three IVM mediums; α-mem as control medium, α-mem supplemented with human bone marrow mesenchymal stem cells (BM-MSCs) and α-mem supplemented with ovarian growth factors (O.F). After 48 h, the maturation rate and morphological feature of IVM oocytes [132 fresh IVM (fIVM) and 134 vitrified IVM (vIVM)] were evaluated. For the ultrastructure study, 10 IVM oocytes from each medium were compared with 10 fresh in vivo oocytes cancelled from ART.

RESULTS

The survival rate of vitrified GV oocyte after thawing was 88.88%. The oocyte maturation rate was reduced in vIVM compared to the fIVM group (76.33% vs. 77.95%); the highest oocyte maturation rate in the O.F fIVM and lowest in α-mem vIVM (82.35% vs. 71.42%). The lowest number of cortical granules was observed in α-mem vIVM, but the greatest presence of M-SER aggregates was in O.F fIVM. In vIVM oocytes, the oolemma contained irregular little microvillus organization.

CONCLUSIONS

The O.F mediums have shown the highest maturation which defends the oocyte ultra-structural conservation.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

Cryopreservation of cynomolgus macaque (Macaca fascicularis) sperm with glycerol and ethylene glycol, and its effect on sperm-specific ion channels - CatSper and Hv1

The cryoprotective agent (CPA) is one of the most important factors that affects the cryosurvival of sperm. The aim of the present study was to compare two different CPAs, glycerol (Gly) and ethylene glycol (EG), on the cryopreservation of cynomolgus macaques sperm and evaluate the effects of cryopreservation on sperm motility, acrosomal integrity, DNA integrity, mitochondrial function and the sperm membrane ion channels CatSper and Hv1. Compared to fresh sperm, cryopreservation with either 0.7 M Gly or EG decreased the sperm motility (79.8 ± 1.5% Vs. 47.3 ± 1.8% and 47.6 ± 1.4%), acrosomal integrity (89.6 ± 1.2% Vs. 80.1 ± 1.8% and 79.6 ± 1.7%), DNA integrity (91.9 ± 0.7% Vs. 82.9 ± 1.0% and 82.3 ± 1.0%) and mitochondrial membrane potential (87.9 ± 1.8% Vs. 70.6 ± 2.7% and 67.9 ± 2.5%) and the quantity of the CatSper and Hv1 channels determined by Western Blot (p < 0.05), and EG showed equal cryoprotection to cynomolgus sperm in all of the sperm parameters. Our results indicated, for the first time, that cryopreservation decreases the quantity of sperm membrane ion channels (CatSper and Hv1), which might be one of the reasons that frozen sperm have a low fertilizing ability. The study will be beneficial to understand the biological process involved in sperm cryopreservation of nonhuman primates and contribute to improving cryopreservation protocols than can maintain sperm function and fertilizing ability.

Supplementation of culture media with vitamin E improves mouse antral follicle maturation and embryo development from vitrified ovarian tissue

AIM

The aim of this study was to evaluate the effects of preventive vitamin E (α-tocopherol) on antral follicle development and embryogenesis of oocytes obtained after vitrification of mouse ovarian tissue.

METHODS

Female Balb/c mice were killed by cervical dislocation after the injection of pregnant mare's serum gonadotrophin (10 IU) and their ovaries were randomly divided into three groups: control or non-vitrified (n = 10), vitrification 1 (5, 10% ethylene glycol + 5, 10% dimethylsulfoxide) (n = 15), and vitrification 2 (10, 15% ethylene glycol + 10, 15% dimethylsulfoxide) (n = 15) with ascending concentration of cryoprotectants. After toxicity tests and vitrification-warming, mechanically isolated antral follicles were cultured in α-minimum essential medium, which was supplemented with or without α-tocopherol (100 μM). The follicular maturation rates and embryo development were collected and assessed. Also, the viability, morphology and ultrastructure of derived antral follicles from vitrified ovaries were analyzed.

RESULTS

The morphology and ultrastructure of follicles were well preserved in the vitrified groups and α-tocopherol supplementation of culture media significantly increased the proportion of oocytes that reached metaphase II blastocyst rates compared to non-α-tocopherol supplemented media (P < 0.01).

CONCLUSION

Vitamin E improves in vitro maturation rates and blastocyst rates of oocytes that are isolated from vitrified ovarian tissue.

Preservation of mouse ovarian tissue follicle morphology and ultra-structure after vitrifying in biotechnological protocols

Background

The aim of the present study was to characterize the morphological and ultrastractural of mouse ovarian tissue with different cryoprotectant solution.

Objective

Aim of this study, is to demonstrae an improved convetional vitrification method on mouse ovarian tissue using different concentrations of ethylene glycol (EG) and/or dimetyl sulfoxide (DMSO) and EG.

Materials and methods

Mouse ovarian tissue dissected and were randomly assigned to three groups: control, conventional vitrification (CV) and toxicity test. Then ovaries were vitrified by 5%, 10% EG or DMSO CV1-CV4, 5%, 10% EG plus DMSO CV5-CV6 and EG plus DMSO in climbing concentrations CV7. The effect of cryoprotectant solutions on ovarian tissue were evaluated by histological examination hematotoxillin & eosin stain, H&E, viability assessment trypan blue stain and ultrastructural analyses transmission electron microscopy, TEM.

Results

Ovarian tissue frozen in CV7 solution showed a higher percentage of morphologically normal follicles or viable follicles than other cryoprotectant solutions P < 0.05. Ultrastructural analysis of ovarian tissue showed that less damage was observed in CV7 and it was very similar to the control group.

Conclusion

Vitrification of ovarian tissue with optimal cryoprotectant solutions such as EG plus DMSO is the most effective for preserving the structural efficiency of ovarian follicles.

Ultrastructure of immature and mature human oocytes after cryotop vitrification

In vitro maturation of vitrified immature germinal vesicle (GV) oocytes is a promising fertility preservation option. We analyzed the ultrastructure of human GV oocytes after Cryotop vitrification (GVv) and compared it with fresh GV (GVc), fresh mature metaphase II (MIIc) and Cryotop-vitrified mature (MIIv) oocytes. By phase contrast microscopy and light microscopy, the oolemmal and cytoplasmic organization of fresh and vitrified oocytes did not show significant changes. GVv oocytes showed significant ultrastructural alterations of the microvilli in 40% of the samples; small vacuoles and occasional large/isolated vacuoles were abnormally present in the ooplasm periphery of 50% of samples. The ultrastructure of nuclei and mitochondria-vesicle (MV) complexes, as well as the distribution and characteristics of cortical granules (CGs), were comparable with those of GVc oocytes. MIIv oocytes showed an abnormal ultrastructure of microvilli in 30% of the samples and isolated large vacuoles in 70% of the samples. MV complexes were normal, but mitochondria-smooth endoplasmic reticulum aggregates appeared to be of reduced size. CGs were normally located under the oolemma but presented abnormalities in distribution and matrix electron density. In conclusion, Cryotop vitrification preserved main oocyte characteristics in the GV and MII stages, even if peculiar ultrastructural alterations appeared in both stages. This study also showed that the GV stage appears more suitable for vitrification than the MII stage, as indicated by the good ultrastructural preservation of important structures that are present only in immature oocytes, like the nucleus and migrating CGs.

Ultrastructure of vitrified rabbit transgenic embryos

The aim of the study was to determine the viability of rabbit transgenic (enhanced green fluorescent protein (EGFP)-positive) embryos cultured in vitro and compare with gene-microinjected (Mi) non-transgenic (EGFP-negative) embryos following vitrification. Non-microinjected and non-vitrified embryos were used as the control. Morphological signs of injury to embryo organelles were determined at the ultrastructural level using transmission electron microscopy (TEM). Morphometric evaluation was performed on cellular organelles using microphotographs obtained by TEM. Intact and Mi embryos recovered from in vivo fertilized eggs at 19-20 hours post coitum (hpc) were cultured for up to 72 hpc (morula stage), evaluated for the EGFP gene integration and then vitrified in 0.25 ml insemination straws in modified EFS (40% ethylene glycol + 18% Ficoll 70 + 0.3 M sucrose) vitrification solution. After 1-3 days the embryos were devitrified, a representative selection of embryos was analyzed by TEM and the remaining embryos were subjected to additional in vitro culture. Observations by TEM showed that the vitrified/warmed EGFP-positive and EGFP-negative embryos had a slight accumulation of cellular debris and lipid droplets compared with the control intact embryos. More severe changes were detected in the membrane structures of the treated embryos, mostly in the cytoplasmic envelope, trophoblastic microvilli, junctional contacts and mitochondria. We suggest that the higher proportion of deteriorated cell structures and organelles in the treated embryos may be due to the vitrification process rather than to mechanical violation (the gene-microinjection procedure), as a detailed inspection of ultrastructure revealed that most damage occurred in the cell membrane structures.

Does cryopreservation of ovarian tissue affect the distribution and function of germinal vesicle oocytes mitochondria?

The aim of this study was to evaluate mitochondrial alteration and ATP content of germinal vesicle (GV) oocytes isolated from fresh and vitrified ovaries. After superovulation, the ovaries from adult mice were collected and divided into control and vitrified groups. GV oocytes were isolated mechanically from each group. Half were cultured for 24 hours and their maturation was assessed. Metaphase II oocytes were collected and submitted to in vitro fertilization and their fertilization rates and development to the blastocyst stage were evaluated. In the remaining GV oocytes, ATP levels were quantified, and mitochondrial distribution, mitochondrial membrane potential, and intracellular free calcium were detected with rhodamine 123, JC-1 and Flou-4 AM staining, using laser-scanning confocal microscopy. Maturation and fertilization rates of GV oocytes and the developmental rates of subsequent embryos were significantly lower in vitrified samples (P < 0.05). The ATP content and Ca(2+) levels differed significantly in fresh and vitrified GV oocytes (P < 0.05). Most mitochondria were seen as large and homogenous aggregates (66.6%) in fresh GV oocytes compared to vitrified oocytes (50%). No significant differences in mitochondrial membrane potential were found between the groups. The lower maturation and fertilization rates of GV oocytes from vitrified ovaries may be due to changes in their mitochondrial function and distribution.

Effect of bovine ovarian tissue vitrification on the structural preservation of antral follicles

This study was performed to evaluate the structural preservation of antral follicles after bovine ovarian tissue vitrification using histological analysis. Ovaries (n = 30) of slaughtered cows were cut into small fragments using a scalpel blade, and the ovarian tissues were randomly assigned to vitrification using 15% dimethyl sulphoxide (DMSO) and 15% ethylene glycol (EG) and fresh tissues (control) groups. For histological evaluations, fresh and post-thawing ovarian tissues were immediately fixed, serially sectioned into 5-μm sections and stained with haematoxylin and eosin (H&E). Nine serial sections per fragment were subjected for morphological assessment. The diameter of the antral follicles was determined and classified into four groups: 1 (≤1 mm), 2 (>1-2 mm), 3 (>2-3 mm) and 4 (>3-4 mm). Then, follicular morphology was evaluated in relation to atresia and categorized into seven grades: Grade A (healthy follicle); Grades B, C and D (early atresia); Grades E and F (moderate atresia); and Grade G (advanced atresia). The results revealed that small diameters of antral follicles (1 and 2 mm) were more susceptible for cryoinjury. The normal follicular morphology (Grade A) was not affected by vitrification throughout follicle diameters. Nevertheless, some damage features were monitored after vitrification. In conclusion, the morphological structure of bovine antral follicles could be successfully preserved by ovarian tissue vitrification.

Cryopreservation of immature buffalo oocytes: effects of cytochalasin B pretreatment on the efficiency of cryotop and solid surface vitrification methods

The aim of the present study was to compare the efficiency of the solid surface (SSV), cryotop (CT) vitrification methods and cytochalasin B (CB) pretreatment for cryopreservation of immature buffalo oocytes. Cumulus-oocyte complexes (COCs) were placed for 1 min in TCM199 containing 10% dimethylsulfoxide (DMSO), 10% ethylene glycol (EG), and 20% fetal bovine serum, and then transferred for 30 s to base medium containing 20% DMSO, 20% EG and 0.5 mol/L sucrose. CB pretreated ((+)CB) or non-pretreated ((-)CB) COCs were vitrified either by SSV or CT. Surviving vitrified COCs were selected for in vitro maturation (IVM) and in vitro fertilization (IVF). The rate of viable oocytes after vitrification in CT groups (82%) was significantly lower (P < 0.05) than that in a fresh control group (100%), but significantly higher (P < 0.05) than those in SSV groups (71-72%). Among vitrified groups, the highest maturation rate was obtained in the CT (-)CB group (32%). After IVF, the cleavage and blastocyst formation rates were similar among vitrified groups but significantly lower than those of the control group. In conclusion, a higher survival rate of oocytes after vitrification and IVM was obtained in the CT group compared with that in the SSV group, indicating the superiority of the CT method. Pretreatment with CB did not increase the viability, maturation or embryo development of vitrified oocytes.

Cryo-survival, fertilization and early embryonic development of vitrified oocytes derived from mice of different reproductive age

PURPOSE

to evaluate the effect of female reproductive age on oocyte cryo-survival, fertilization and the subsequent embryonic development following vitrification using the mouse model in order to address the question of how maternal reproductive age is related to fertility preservation.

METHODS

oocytes were collected from mice of different reproductive age: (1) 8-10 weeks, (2) 16-20 weeks, (3) 32-36 weeks, and (4) 44-48 weeks. Following vitrification and warming, the oocytes in each group were assessed for cryo-survival, fertilization and embryonic development as well as for the quality of blastocysts. Fresh oocytes without undergoing vitrification were used in each age group as controls.

RESULTS

the mean number of oocytes retrieved following superovulation was found to reduce significantly (P < 0.05) in mice from 32-36 weeks of age (18.1 ± 8.5) compared with 8-10 weeks of age (26.8 ± 9.8) and 16-20 weeks of age (23.9 ± 4.2) respectively. The cryo-survival rate of oocytes was reduced significantly (P < 0.05) in mice of 44-48 weeks of age (90.4% ± 7.9) compared with the other 3 groups (98.8% ± 2.1, 98.0% ± 3.3 and 98.5% ± 2.2, respectively). The cleavage rate of vitrified oocytes declined significantly following the increase in maternal age in mice of 32-36 weeks of age (69.7% ± 20.8) forward (63.6% ± 9.2). However, no significant difference in the cleavage rate was found among the control groups of different maternal ages. The rate of embryo development to the blastocyst stage in the vitrified oocytes also significantly declined following the increase in maternal age (71.8% ± 8.8, 66.4% ± 10.7, 64.2% ± 17.4 and 4.1% ± 8.3 respectively). There were no such differences in the rates of embryo development to the blastocyst stage among the control groups following the increase in maternal age (75.9% ± 12.2, 79.5% ± 28.9, 70.2% ± 17.4 and 69.3% ± 19.0 respectively). However, the quality of blastocysts produced from 32-36 weeks and 44-48 weeks of ages was significantly poor in term of total cell numbers and the ratio of inner cell mass(ICM) / trophectoderm (TE) compared to younger age in both vitrified and control groups

CONCLUSIONS

cryo-survival of oocytes following vitrification and warming procedures is associated with female reproductive age. There is a more negative impact on the oocytes following vitrification and warming with the increase of maternal age.

Solid-surface vitrification is an appropriate and convenient method for cryopreservation of isolated rat follicles

BACKGROUND

Cryopreservation of isolated follicles may be a potential option to restore fertility in young women with cancer, because it can prevent the risks of cancer transmission. Several freezing protocols are available, including slow-rate freezing, open-pulled straws vitrification (OPS) and solid-surface vitrification (SSV, a new freezing technique). The purpose of our study was to investigate the effects of these freezing procedures on viability, ultrastructure and developmental capacity of isolated rat follicles.

METHODS

Isolated follicles from female Sprague-Dawley rats were randomly assigned to SSV, OPS and slow-rate freezing groups for cryopreservation. Follicle viability assessment and ultrastructural examination were performed after thawing. In order to study the developmental capacity of thawed follicles, we performed in vitro culture with a three-dimensional (3D) system by alginate hydrogels.

RESULTS

Our results showed that the totally viable rate of follicles vitrified by SSV (64.76%) was slightly higher than that of the OPS group (62.38%) and significantly higher than that of the slow-rate freezing group (52.65%; P < 0.05). The ultrastructural examination revealed that morphological alterations were relatively low in the SSV group compared to the OPS and slow-rate freezing groups. After in vitro culture within a 3D system using alginate hydrogels, we found the highest increase (28.90 +/- 2.21 microm) in follicle diameter in follicles from the SSV group. The estradiol level in the SSV group was significantly higher than those in the OPS and slow-rate freezing groups at the end of a 72-hr culture period (P < 0.05).

CONCLUSIONS

Our results suggest that the SSV method is an appropriate and convenient method for cryopreservation of isolated rat follicles compared with the conventional slow-rate freezing method and the OPS method.

Reproduction in domestic buffalo

The domestic buffalo is an indispensable livestock resource to millions of smallholder farmers in developing countries, particularly in Asia. Although its reproductive biology is basically similar to that of cattle, there are important differences and unique characteristics that need to be considered in order to apply modern reproductive technologies to improve its productivity. Under most smallholder production systems, the reproductive efficiency of buffalo is compromised by factors related to climate, management, nutrition and diseases. However, when managed and fed properly, buffalo can have good fertility and provide milk, calves and draught power over a long productive life. The basic technical problems associated with artificial insemination in buffalo were largely overcome two decades ago, but the technology has not had the expected impact in some developing countries, because largely of infrastructural and logistic problems. Approaches involving the use of hormones for treating anoestrus and for synchronizing oestrus have had varying rates of success, depending on the protocols used and the incidence of underlying problems that cause infertility. Embryo technologies such as multiple ovulation embryo transfer, in vitro embryo production, cryopreservation and cloning are being intensively studied but have had far lower success rates than in cattle. Improving the productivity of buffalo requires an understanding of their potential and limitations under each farming system, development of simple intervention strategies to ameliorate deficiencies in management, nutrition and healthcare, followed by judicious application of reproductive technologies that are sustainable with the resources available to buffalo farmers.