Trehalose sustains a higher post-thaw sperm motility than sucrose in vitrified human sperm

One of the cryopreservation methods that best preserves sperm function is vitrification. However, comparative studies have not been performed to evaluate the effect of nonpermeable cryoprotectors on sperm function for prolonged periods of time post-devitrification. These times are necessary, especially in in vitro fertilisation and intrauterine insemination, for gamete interaction and then fertilisation to occur, while maintaining motility to arrive at the fertilisation site. In this study, sucrose (.25 m) and trehalose (.1 and .05 m) were compared in essential parameters like motility and plasma membrane integrity for 12 hr. Post-devitrification sperm motility using .1 m trehalose was 68.9%, higher than that obtained with .05 m trehalose (59.9%, p < .0081) and .25 m sucrose (57.9%, p < .0002). Similar results were obtained at 6 and 12 hr with .1 m trehalose (58.0% and 42.3% respectively) compared to .05 m trehalose (p < .0184 and p < .033) and .25 m sucrose (p < .0001 and p < .0012).There was no difference between .25 m sucrose and .05 m trehalose. Membrane integrity was best preserved at time 0 by .1 m trehalose (p < .05), but there was no significance at 6 and 12 hr compared to sucrose. Our results suggest that for assisted reproduction techniques that require motile spermatozoa for a longer period of time, use of .1 m trehalose is recommended in the sperm vitrification technique.

Use of the fluorescent dye tetramethylrhodamine methyl ester perchlorate for mitochondrial membrane potential assessment in human spermatozoa

Mitochondrial membrane potential (ΔΨm) is an indicator of sperm quality and its evaluation complements the standard semen analysis. The fluorescent dye JC-1 has been widely used to assess sperm ΔΨm; however, some problems have been detected under certain experimental conditions. Another fluorescent compound, tetramethylrhodamine methyl ester perchlorate (TMRM), has been used in somatic cells and bovine spermatozoa but not in human spermatozoa. TMRM accumulates in hyperpolarised mitochondria and the fluorescence intensity of this compound correlates with ΔΨm. Thus, the aim of this study was to evaluate and validate the usefulness of the fluorescent dye TMRM for measuring sperm ΔΨm. The results showed that TMRM accurately detects sperm populations displaying either high or low ΔΨm. Moreover, TMRM was able to measure sperm ΔΨm under the experimental conditions in which JC-1 had previously presented difficulties. Differences in ΔΨm according to sperm and semen quality were properly detected and a positive correlation between ΔΨm and conventional semen parameters was observed. Finally, a positive correlation was found between the ΔΨm measurement by TMRM and by the widely used JC-1. In conclusion, TMRM is a simple, time-effective method, easy to set in laboratories equipped with flow cytometry technology, and can accurately detect changes in ΔΨm with efficiency comparable to JC-1 without its limitations.

Effect of seminal plasma on Atlantic salmon (Salmo salar) sperm vitrification

This study was designed to test a vitrification method in Atlantic salmon spermatozoa and determine the capacity of seminal plasma (SP) to protect these cells from cryoinjuries. The vitrification medium consisted of a standard buffer for fish spermatozoa (Cortland medium) + 10% DMSO + 2% BSA + 0.13-M sucrose + SP at concentrations of 30% (G30), 40% (G40), or 50% (G50). Fresh sperm was used as a control. To freeze the samples, 30-μL suspensions of spermatozoa from each group were dropped directly into liquid nitrogen. The resulting spheres were placed in cryotubes for storage in liquid nitrogen. The cryotubes with the vitrified spermatozoa were thawed by placing them in a water bath at 37 °C for 45 seconds. After thawing, the following sperm quality parameters were determined by flow cytometry: DNA fragmentation (terminal deoxynucleotidyl transferase dUTP nick end labeling), plasma membrane integrity (SYBR-14/PI, staining technique), and mitochondrial membrane potential (JC-1 staining). An optical microscope was used to assess subjectively sperm motility, whereas fertility was determined by the presence of neurulation using five replicates per treatment in a sample of 30 eggs. Spermatozoa quality variables were preserved best when the highest concentration of SP (50%) was used (DNA fragmentation, 9.2%; plasma membrane integrity, 98.6%; mitochondrial membrane integrity, 47.2%; motility, 44.1%; and fertility, 46.2%).

In vitro perfusion of whole bovine ovaries by freezing medium: effect of perfusion rate and elapsed time after extraction

BACKGROUND

Cryopreservation and transplantation of the whole ovary with vascular pedicle would be helpful to prevent posttransplantation ischemia. In fact, perfusion of the intact mammalian ovary through arteries and veins is the most technically difficult part of the whole cryopreservation process because of its complexity. It is important to develop the technology of long-time perfusion of intact ovaries by cryoprotectants at low temperatures because it was established earlier that 24-hour cooling to 5 degrees C before cryopreservation is beneficial for the freezing of human ovarian tissue. The aim of this research was to study the effectiveness of perfusion of intact bovine ovaries with different rates of perfusion and elapsed time between extraction of these ovaries and beginning of perfusion.

METHODS

Arteria ovarica was cannulated and ovaries were perfused with Leibovitz L-15 medium + 100 IU/mL heparin + 5% bovine calf serum + 6% dimethyl sulfoxide + 6% ethylene glycol + 0.15 M sucrose + Indian ink at room temperature (22 degrees C). In the first cycle of experiments, ovaries (n = 145) were perfused for 60 minutes during 1 to 1.5 hours after extraction of ovaries in the slaughter house at perfusion rates of 150 mL/hour (2.5 mL/minute), 100 mL/hour (1.67 mL/minute), 75 mL/hour (1.25 mL/minute), 50 mL/hour (0.83 mL/minute), 25 mL/hour (0.42 mL/minute), and 12.5 mL/hour (0.21 mL/minute) for groups 1, 2, 3, 4, 5, and 6, respectively. In the second cycle of experiments, ovaries (n = 29) were perfused with a rate of 25 mL/hour (0.42 mL/minute) for 60 minutes during the following time-periods elapsed after extraction of ovaries in the slaughter house: 3 hours (n = 18), 4 hours (n = 5), 5 hours (n = 3), and 6 hours (n = 3) for groups 1, 2, 3, and 4, respectively. Ovaries in luteal and follicular phase of development were distributed randomly into groups. Successful perfusion of blood vessels was detected visibly by a blue coloration of the vascular pedicle and ovarian tissues. The percentage of Indian ink-perfused tissues was detected. The intensity of the vascular leakage and tissue damage was scored microscopically and noted as follows: lack of disruption (-), weak disruption (+), moderate disruption (++), and strong disruption

RESULTS

The first cycle of experiments shows that an optimal perfusion rate was established for groups 4 and 5 (50 and 25 mL/hour, respectively). In the second cycle of experiments, good perfusion of ovaries with the perfusion rate of 25 mL/hour was established only for ovaries of group 1 (3 hours after extraction). The effectiveness of perfusion in group 2 (4 hours after extraction) was sharply decreased.

CONCLUSIONS

Effective perfusion of bovine intact ovaries with vascular pedicle with freezing medium (6% ethylene glycol + 6% dimethyl sulfoxide + 0.15 M sucrose) at room temperature includes a rate of perfusion 25 or 50 mL/ hour. Ovaries must be perfused no later than 3 hours after the death of animals.

Quality of human spermatozoa: relationship between high-magnification sperm morphology and DNA integrity

The aim of this work is to establish the relationship between the morphology of Intracytoplasmic Morphologically Selected Sperm Injection (IMSI)-selected spermatozoa and their DNA integrity. The 45 ejaculates were randomly distributed into three treatment groups: normozoospermic, oligoasthenozoospermic and oligoasthenotheratozoospermic samples. The evaluation of DNA integrity was performed using the sperm chromatin dispersion test. It was established that DNA integrity of spermatozoa is strongly dependent on ejaculate quality (P < 0.05). The count of spermatozoa with nonfragmented DNA in normozoospermic samples was high and independent from IMSI-morphological classes (Class 1 versus Class 3, respectively) (P > 0.1). With decreased ejaculate quality, the percentage of spermatozoa with nonfragmented DNA decreased significantly (P < 0.05) independent from morphological class. Nevertheless, the rate of IMSI-selected spermatozoa with fragmented DNA within of Class 1 in normozoospermic (Group 1), in oligoasthenozoospermic (Group 2) and in oligoasthenotheratozoospermic (Group 3) samples was 21.1%, 31.8% and 54.1%, respectively. In conclusion, there is a direct relationship between morphological parameters of spermatozoa and their DNA integrity. However, the IMSI technique alone is not enough for the selection of spermatozoa with intact nuclei.

Cryopreservation of Ovarian Tissue: Detailed Description of Methods for Transport, Freezing and Thawing

Purpose: In many cases cancer therapy leads to an irreversible reduction or even loss of ovarian reserve. Cryopreservation of ovarian tissue with subsequent thawing and re-transplantation of tissue after the cancer is in remission constitutes a promising method to preserve fertility in women. To date, more than 25 cases of live births after re-transplantation of cryopreserved ovarian tissue have been published worldwide. In Germany the first live birth after re-transplantation of cryopreserved tissue was in 2011. Material and Methods: After surgical removal of ovarian tissue in the Gynaecological Clinic of Dresden University, the tissue was sent to the Gynaecological Clinic of Bonn University in a special transport container at 5 °C and was frozen the next day using 1.5 M dimethyl sulfoxide cryosolution. In 2010 this ovarian tissue was thawed using a sucrose solution in the Gynaecological Clinic of Erlangen University Clinical Centre and was laparoscopically re-transplanted into the patient. Results: The patient became pregnant, the pregnancy was uneventful, and she gave birth to a healthy boy. Conclusion: Freezing of ovarian tissue with subsequent re-transplantation as described here is a viable method to preserve fertility in cancer patients.

Vitrified sperm banks: the new aseptic technique for human spermatozoa allows cryopreservation at -86 °C

The vitrification technique is simple, quick, cost-effective and has showed a significantly stronger cryoprotective effect in contrast to conventional freezing. The method is based on the rapid cooling of the cell by direct immersion in liquid nitrogen (LN (2) ), thereby avoiding the formation of ice crystals, due to the lower risk of water thawing, which impairs cell function. The aim of this study was to evaluate the effect of storage at -86 °C compared to the conventional -196 °C (under LN (2) ) on essential parameters of the functioning of aseptically vitrified human sperm. Sperm motility, integrity of mitochondrial membrane potential and the rate of DNA fragmentation were determined. The comparison of -86 °C and -196 °C demonstrated no statistical difference in sperm progressive motility (73% vs. 77%), integrity of mitochondrial membrane potential (71% vs. 74%) or DNA fragmentation (3.1% vs. 2.9%). In conclusion, aseptically vitrified sperm can be preserved at -86 °C; eliminating the use of LN (2) simplifies and significantly reduces the costs associated with storage in sperm banks by decreasing the time and space needed for storage, the effort in finding stored samples, and by improving safety for the operator. However, for prolonged storage further studies are needed.

Long-time cooling of human ovarian tissue before cryopreservation as obvious procedure: stimulation of follicular development and neo-vascularisation

BACKGROUND

The positive effect of cooling on tissue cells is known. The aim of this research was to study the intensiveness of neo-vascularisation and follicular development in ovarian tissue after 24 hours cooling to 5 degrees C before cryopreservation.

METHODS

Fifty six pieces from 7 patients were divided into the following four groups: Group 1: pieces cultured just after operation, Group 2: pieces cooled after operation to 5 degrees C for 24 hours and then cultured, Group 3: pieces frozen-thawed just after operation and then cultured, Group 4: pieces cooled after operation to 5 degrees C for 24 hours, frozen, thawed, and then cultured. Culture of ovarian pieces was performed in a chorioallantoic membrane (CAM)-system for 5 days. The efficacy of the tissue cooling was evaluated by the development of follicles and intensiveness of neo-vascularisation (by Desmin).

RESULTS

For Group 1, 2, 3, and 4, mean density of follicles per 1 mm3 was 10.1, 11.1, 9.8, and 12.0, respectively (P1-2, 3-4 < 0.05). For these groups 91%, 92%, 90%, and 90% preantral follicles were morphologically normal (P1-2, 3-4 > 0.1). The immunohistochemical analysis showed that the intensiveness of neo-vascularisation observed in ovarian tissue of Group 2 (pre-cooled before culture) and Group 4 (pre-cooled before cryopreservation) was drastically increased.

CONCLUSIONS

The 24 hour cooling to 5 degrees C before cryopreservation is beneficial for cryopreservation of human ovarian tissue.

Cryoprotectant-free vitrification of fish (Oncorhynchus mykiss) spermatozoa: first report

The aims of this investigation were to test a novel technology comprising cryoprotectant-free vitrification of the spermatozoa of rainbow trout and to study the ability of sucrose and components of seminal plasma to protect these cells from cryo-injuries. Spermatozoa were isolated and vitrified using three different media: Group 1: standard buffer for fish spermatozoa, Cortland(®) medium (CM, control); Group 2: CM + 1% BSA + 40% seminal plasma; and Group 3: CM + 1% BSA + 40% seminal plasma + 0.125 m sucrose. For cooling, 20-μl suspensions of cells from each group were dropped directly into liquid nitrogen. For warming, the spheres containing the cells were quickly submerged in CM + 1% BSA at 37 °C with gentle agitation. The quality of spermatozoa before and after vitrification was analysed by the evaluation of motility and cytoplasmic membrane integrity with SYBR-14/propidium iodide staining technique. Motility (86%, 81% and 82% for groups 1, 2 and 3, respectively) (P > 0.1) was not decreased significantly. At the same time, cytoplasmic membrane integrity of spermatozoa of Groups 1, 2 and 3 was changed significantly (30%, 87% and 76% respectively) (P < 0.05). All tested solutions can be used for vitrification of fish spermatozoa with good post-warming motility. However, cytoplasmic membrane integrity was maximal in Group 2 (CM + 1% BSA + 40% seminal plasma). In conclusion, this is the first report about successful cryoprotectant-free cryopreservation of fish spermatozoa by direct plunging into liquid nitrogen (vitrification). Vitrification of fish spermatozoa without permeable cryoprotectants is a prospective direction for investigations: these cells can be successfully vitrified with 1% BSA + 40% seminal plasma.

Vitrification of human ICSI/IVF spermatozoa without cryoprotectants: new capillary technology

The aim of this study was to develop and to test the standardized aseptic technology of permeable cryoprotectant-free vitrification of human spermatozoa in capillaries (for intracytoplasmic sperm injection [ICSI] or in vitro fertilization [IVF]). To test the effect of vitrification on basic sperm parameters, each of 68 swim-up-prepared ejaculates from oligo-astheno-terato-zoospermic patients were aliquoted and distributed into 3 groups: 1) nontreated control, 2) 10 μL of spermatozoa cryopreserved by slow conventional freezing with glycerol-contented medium, and 3) 10 μL of spermatozoa vitrified in 50-μL plastic capillaries in culture medium with 0.25 M sucrose. Spermatozoa motility (1, 24, and 48 hours after warming), plasma membrane integrity, acrosomal integrity, and spontaneous capacitation-like changes were determined after warming. Aseptic cryoprotectant-free vitrification showed a significantly stronger cryoprotective effect compared with conventional freezing. One hour after warming, motility, plasma membrane integrity, and acrosomal integrity were significantly higher than is observed for conventionally frozen spermatozoa (28% vs 18%, 56% vs 22%, and 55% vs 21%, respectively; P < .05), although lower than in fresh spermatozoa (35%, 96%, and 84%, respectively; P < .05). Capacitation-like changes did not differ significantly between vitrified and conventionally frozen samples (8% vs 9%, respectively; P > .1) (2% in fresh spermatozoa). The newly developed technology of aseptic vitrification of human spermatozoa in capillaries can effectively preserve these cells from cryo-injures. Spermatozoa, vitrified by this technology, are free from seminal plasma owing to swim-up preceding vitrification and are free from permeable cryoprotectants. They are ready for further use immediately after warming without any additional treatment. Therefore, the reported technology has a great potential for use in ICSI/IVF.

Fish (Oncorhynchus mykiss) spermatozoa cryoprotectant-free vitrification: stability of mitochondrion as criterion of effectiveness

The aim of the present investigations was to test a novel technology comprising cryoprotectant-free vitrification of the spermatozoa of rainbow trout and to study the ability of sucrose and components of seminal plasma to protect these cells from cryoinjuries. Spermatozoa were isolated and vitrified using five different mediums: Group 1: standard buffer for fish spermatozoa, Cortland(®)-medium (CM, control); Group 2: CM+1% bovine serum albumin (BSA); Group 3: CM+1% BSA+0.125 M sucrose; Group 4: CM+1% BSA+40% seminal plasma; and Group 5: CM+1% BSA+40% seminal plasma+0.125 M sucrose. For cooling, 20 μL suspensions of cells from each group were dropped directly into liquid nitrogen. For warming, the spheres containing the cells were quickly submerged in CM+1% BSA at 37 °C with gentle agitation. The quality of spermatozoa before and after vitrification was analysed by the evaluation of motility, cytoplasmic membrane integrity (SYBR-14/propidium iodide staining technique), and mitochondrial membrane integrity (JC-1 staining). Motility (86%, 71%, 80%, 81%, and 82%, for Groups 1, 2, 3, 4, and 5, respectively) and cytoplasmic membrane integrity (90%, 82%, 83%, 84%, and 87%, respectively) of spermatozoa in all the 5 groups were not decreased significantly. All tested solutions can be used for vitrification of fish spermatozoa with good post-warming motility and cytoplasmic membrane integrity. However, mitochondrial membrane potentials of the spermatozoa in Groups 1, 2, 3, 4, and 5 were changed significantly (6%, 50%, 37%, 55%, and 34%, respectively) (P(1,2,3,4,5)<0.001; P(2,3,4,5) <0.01)(P(3-5)>0.1). This rate was maximal in Group 4 (CM+1% BSA+40% seminal plasma). In conclusion, this is the first report about successful cryoprotectant-free cryopreservation of fish spermatozoa by direct plunging into liquid nitrogen (vitrification). Vitrification of fish spermatozoa without permeable cryoprotectants is a prospective direction for investigations: these cells can be successfully vitrified with 1% BSA+40% seminal plasma without significant loss of important physiological parameters.

Cryoprotectant-free vitrification of human spermatozoa in large (up to 0.5 mL) volume: a novel technology

BACKGROUND

The aim of this study was to develop and to test the aseptic technology of cryoprotectant-free vitrification of human spermatozoa in large volume (for intrauterine insemination). Spermatozoa, vitrified by this technology, are free of permeant cryoprotectants and are ready for further use immediately after warming without any additional treatment (centrifugation or separation in the gradient for removal of cryoprotectant).

METHODS

Each of 52 swim up-prepared ejaculates were divided into three aliquots and distributed into three treatment groups: Group 1: non-treated control; Group 2: spermatozoa cryopreserved by slow conventional freezing with glycerol-containing medium, and Group 3: spermatozoa vitrified in 0.5 mL insemination "French" straws in culture medium with 0.25 M sucrose. Sperm motility 1, 24 and 48 hours after warming, plasma membrane integrity and capacitation-like changes (spontaneous "cryo-capacitation" and acrosome reaction) were assessed after freezing-thawing.

RESULTS

In contrast to conventional freezing, spermatozoa vitrified with aseptic cryoprotectant-free technology displayed superior functional characteristics. The motility rate, integrity rates of cytoplasmic, and acrosomal membranes were significantly higher after vitrification than after conventional freezing (76% vs 52%, 54% vs 28% and 44% vs 30%, respectively) (p < 0.05). However, there were no differences between vitrification and conventional freezing in the presence of glycerol in terms of percentage of spermatozoa expressing CTC-capacitation pattern (11% vs 10%, respectively) (p > 0.1).

CONCLUSIONS

A basic protection from cryo-injury can be achieved for human spermatozoa using the novel technology of aseptic cryoprotectant-free vitrification in large volumes.

Human ovarian tissue vitrification versus conventional freezing: morphological, endocrinological, and molecular biological evaluation

Cryopreservation as a process can be divided into two methods: conventional freezing and vitrification. The high effectiveness of vitrification in comparison with conventional freezing for human oocytes and embryos is shown, whereas data on human ovarian tissue are limited. The aim of this study was to compare the safety and effectiveness of conventional freezing and vitrification of human ovarian tissue. Ovarian tissue fragments from 15 patients were transported to the laboratory within 22–25 h in a special, isolated transport box that can maintain a stable temperature of between 5 and 8 °C for 36 h. Small pieces of ovarian tissue (0.3–1×1–1.5×0.7–1 mm) were randomly distributed into three groups: group 1, fresh pieces immediately after receiving transport box (control); group 2, pieces after vitrification; and group 3, pieces after conventional freezing. After thawing, all the pieces were culturedin vitro. The viability and proliferative capacity of the tissue byin vitroproduction of hormones, development of follicles, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene expression after culture were evaluated. A difference between freezing and vitrification was not found in respect to hormonal activity and follicle quality. The supernatants showed 17-β estradiol concentrations of 365, 285, and 300 pg/ml respectively, and progesterone concentrations of 3.82, 1.99, and 1.95 ng/ml respectively. It was detected that 95, 80, and 83% follicles respectively were morphologically normal. The molecular biological analysis, however, demonstrated that theGAPDHgene expression in ovarian tissue after vitrification was dramatically decreased in contrast to conventional freezing. For cryopreservation of human ovarian tissue, conventional freezing is more promising than vitrification, because of higher developmental potential.

Apoptosis in human ovarian tissue after conventional freezing or vitrification and xenotransplantation

One of the new emerging techniques to preserve reproductive potential of cancer patients is cryopreservation of ovarian fragments prior to medical treatment and their retransplantation after healing. In order to investigate and compare apoptosis in human ovarian tissue after conventional ("slow") freezing and vitrification, we used a xenograft model in which conventionally frozen, vitrified and fresh non treated human ovarian tissue pieces were subcutaneously transplanted in SCID mice. The tissue samples were weekly, during four weeks, recovered from scarified SCID mice. The apoptosis was examined by immunohistochemical staining with the anti-caspase-3 antibody. There was a significant difference between the amount of apoptotic cells in cryopreserved ovarian tissue independent from mode of cooling compare to the control. The ovarian tissue after vitrification showed a significantly higher amount of apoptotic cells, than in slow frozen. The results obtained after comparative study of two different cryopreservation methods show that vitrification of human ovarian tissue could become a practice-relevant alternative to slow cryopreservation only after further improvement.

Acrosomal status and mitochondrial activity of human spermatozoa vitrified with sucrose

This study investigates the ability of sucrose to protect spermatozoa against mitochondrial damage, artificial cryoinduction of capacitation, and acrosome reaction. Spermatozoa were isolated using the swim-up procedure performed using three different media: (a) human tubal fluid (HTF, control) medium; (b) HTF with 1% human serum albumin (HSA); and (c) HTF with 1% HSA and 0.25 M sucrose. From each group, 30 mul suspensions of cells were dropped directly into liquid nitrogen and stored for at least 24 h. Cells were thawed by quickly submerging the spheres in HTF with 1% HSA at 37 degrees C with gentle agitation. Sperm motility, viability, mitochondrial membrane potential integrity, spontaneous capacitation, and acrosome reaction were investigated. Sperm viability, acrosome reaction, and capacitation were detected using the double fluorescence chlortetracycline-Hoechst 33258 staining technique. Mitochondrial function was evaluated using a unique fluorescent cationic dye, 5,5',6,6'-tetrachloro-1-1',3,3'-tetraethyl-benzamidazolocarbocyanin iodide, commonly known as JC-1. The number of progressively motile spermatozoa was significantly higher in the sucrose-supplemented medium group (57.1+/-3.2%, P<0.05) when compared with controls (19.4+/-1.9%). The combination of HSA and sucrose (65.2+/-2.6%) has a stronger cryoprotective effect on the integrity of mitochondrial membrane potential (P<0.05) compared with HSA alone (32.6+/-4.7%). In conclusion, vitrification of human spermatozoa with non-permeable cryoprotectants such as HSA and sucrose can effectively cryopreserve the cells without significant loss of important physiological parameters.

Simplified technique of human ovarian tissue freezing: quick cooling from -36 degree C

Standard protocol of freezing of human ovarian tissue presupposes the very slow cooling (-0.3 C/min) from auto-seeding to -40 C, then slow cooling (-10 C/min) to -140 C and then direct plunging into liquid nitrogen. The aim of this investigation was to compare the -10 C/min cooling rate of human ovarian tissue from -40 C to -140 C with the -220 C/min cooling rate (direct plunging into liquid nitrogen) from -36 degree C. After post-thawing in vitro culture of tissue, hormonal activity as well as follicle viability was evaluated. After culture of fresh tissue pieces (Group 1), pieces after freezing and thawing with slow cooling (-10 C/min) from -40 C (Group 2) and pieces after freezing and thawing with direct plunging into liquid nitrogen (-220 C/min) from -36 C (Group 3), the supernatants showed estradiol 17-ss concentrations of 481, 441 and 459 pg per ml, respectively, and progesterone concentrations of 9.05, 5.06, 4.87 ng per ml, respectively. It is concluded that 94, 96, and 98 percent follicles for Groups 1, 2 and 3, respectively, were normal. Technique of human ovarian tissue cryopreservation with very slow cooling to -36 C and then direct plunging into liquid nitrogen with -220 C/min cooling rate is tolerated without apparent detriment.

Meiotic abnormalities in in vitro-matured marmoset monkey (Callithrix jacchus) oocytes: development of a non-human primate model to investigate causal factors

BACKGROUND

Meiotic abnormalities are thought to be a major causal factor of low embryo development rates, for embryos developed from in vitro-matured oocytes. A new non-human primate model, in the common marmoset, is being developed to facilitate investigation of the mechanisms involved.

METHODS

Oocytes were dissected from antral follicles from three size classes. They were allowed to mature in vitro for only 24 h, in order to focus the investigation on the rapidly maturing oocytes. Chromosome spreads were visualized with Giemsa staining, and spindles /chromosomes with fluorescently labelled anti-alpha-tubulin antibody combined with a DNA fluorochrome.

RESULTS

40% of the oocytes had reached metaphase II (MII) after 24 h. Of the MII oocytes selected for karyotyping, readable chromosomal spreads were obtained from 64%. Overall, 63% of these presented a normal haploid chromosome number of 23,X, with all abnormal karyotypes occurring in the oocytes from small follicles. For another group of MII oocytes, where meiotic spindles were visualized, only half of the MII oocytes displayed well-formed spindles and apparently correct chromosomal alignment.

CONCLUSIONS

This work provides the first information on the normal and aneuploid MII meiotic chromosome sets for the marmoset oocyte, and demonstrates a high rate of chromosomal and spindle abnormality among rapidly maturing oocytes from small antral follicles.

Aseptic technology of vitrification of human pronuclear oocytes using open-pulled straws

BACKGROUND

The aim of this study was to compare the viability of human pronuclear oocytes subjected to vitrification using cooling by direct submerging of open-pulled straws in liquid nitrogen versus vitrification by cooling of open-pulled straws located inside a closed 0.5 ml straw (aseptic system).

METHODS

Two- and three-pronuclei stage oocytes (n=114) were cryopreserved in super-open-pulled straws by vitrification in 20% ethylene glycol +20% dimethylsulphoxide (DMSO) + osmotic active and neutral non-permeable cryoprotectants with a four-step exposure in 20, 33, 50 and 100% vitrification solution for 2, 1 and 1 min, and 30-50 s, respectively at room temperature, and plunging into liquid nitrogen. Oocytes of group 1 (n=42) were rapidly cooled at a speed of 20,000 degrees C/min by direct plunging of open-pulled straws into liquid nitrogen. Oocytes of group 2 (n=44) were first located in 0.5 ml straws, which were closed at both sides by metal balls, and then plunged into liquid nitrogen. This method resulted in a cooling speed of 200 degrees C/min. For both groups, oocytes were thawed rapidly at a speed of 20 000 degrees C/min using an identical protocol. Oocytes subsequently were expelled into a graded series of sucrose solutions (1.0, 0.75, 0.5, 0.25 and 0.12 mol/l) at 2.5 min intervals.

RESULTS

Oocyte development up to expanded blastocyst stage after in vitro culture was 15% in group 1, 14% in group 2 and 29% in an untreated control group.

CONCLUSION

The deposition of human pronuclear oocytes in open-pulled straws which are placed inside a hermetically closed container guarantees a complete isolation of oocytes from liquid nitrogen and avoids potential contamination by pathogenic microorganisms. The combination of direct plunging of this container into liquid nitrogen and rapid warming makes this process as efficient as conventional vitrification.

DNA integrity and motility of human spermatozoa after standard slow freezing versus cryoprotectant-free vitrification

BACKGROUND

In contrast to the technique of conventional freezing, the vitrification of spermatozoa requires high cooling rates (720 000 degrees K/min), which could be damaging for spermatozoa. The aim of our study was to compare slowly frozen and vitrified spermatozoa in terms of their post-thaw DNA integrity and motility.

METHODS

Semen samples were prepared according to the routine swim-up technique and divided into aliquots for comparison of fresh, conventionally frozen and vitrified spermatozoa from the same ejaculate in the presence or absence of cryoprotectants. Spermatozoa motility and DNA integrity were determined.

RESULTS

The motility of spermatozoa conventionally (slowly) frozen with a cryoprotectant was similar to that recorded for spermatozoa vitrified in the absence of cryoprotectant (47 versus 52%). The DNA integrity was unaffected by the cryopreservation method or presence of cryoprotectants.

CONCLUSION

The vitrification of human spermatozoa in the absence of conventional cryoprotectants is indeed feasible. The DNA integrity of vitrified sperm is comparable with that shown by standard slow-frozen/thawed spermatozoa, yet the method is quick and simple and does not require special cryobiological equipment.