Vitrification of mouse pronuclear embryos after polar body biopsy without direct contact with liquid nitrogen

Cryopreservation in ART and concerns with contamination during cryobanking

The cryopreservation of gametes and embryos is vital to numerous fields of reproductive biology, including assisted human reproduction. With improved culture conditions, there are an increasing number of embryos to cryopreserve for potential use in subsequent cycles. Many of the gametes and embryos in human IVF are cryopreserved in open systems. Because liquid nitrogen is not sterile, concerns have been raised with regard to contamination from the liquid nitrogen and also cross-contamination between patients' germplasm. Human gamete and embryo cryopreservation are discussed, with recommendations on how to minimize and eliminate contamination, emphasizing the benefits of closed vitrification devices.

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.

Cryotop and development of vitrified immature bovine oocytes

The effectiveness of different cryodevices (open-pulled straw (OPS), electron microscopy grid (EMG), and Cryotop was evaluated for vitrification of immature bovine oocytes. Polar body, metaphase II stage (MII), survivability, and subsequent developmental rates were determined. Only oocytes with four or five layers of cumulus cells were used. Oocytes were equilibrated in two vitrification solutions - 1: 10% DMSO + 10% ethylene glycol (EG) for 30-45sec and 2: 20% DMSO + 20% EG +0.5M sucrose for 25sec -, mounted on one of the cryodevices and directly plunged into liquid nitrogen for 10 days. Immature vitrified oocytes using Cryotop showed the highest rates of polar body extrusion (PB) and nuclear maturity (MII); 41 and 58% respectively. Vitrified oocytes using OPS and EMG showed 26 and 32%; and 35 and 46% of PB and MII rates, respectively. The highest survivability resulted from Cryotop and EMG groups and no significant difference was found between them. Vitrified oocytes using Cryotop had the highest cleavage and blastocyst rates. All of the mean rates for vitrified immature oocytes were significantly lower than that of control group (P<0.05). The results of this study showed the superiority of Cryotop device for vitrification of immature bovine oocytes

Human oocyte cryopreservation: comparison between slow and ultrarapid methods

The success of reproductive technologies is facilitated by the cryopreservation of embryos and gametes. In Italy, where legislation prohibits zygote and embryo cryopreservation, clinics have extensively introduced oocyte cryopreservation. Two different strategies of oocyte cryopreservation are available: slow freezing or ultrarapid cooling (vitrification). Although the results are very encouraging with both methods, there is still controversy regarding both the procedure itself and the most suitable method to use. This study reports the routine application of the two different oocyte cryopreservation methods in programmes running in two consecutive periods. The study centre carried out 286 thawing cycles for a total of 1348 thawed oocytes cryopreserved by the slow-freezing method and 59 warming cycles for a total of 285 warmed oocytes cryopreserved by vitrification. Comparison of the outcomes obtained with the slow-freezing method versus vitrification in women who underwent IVF for infertility showed survival, fertilization, pregnancy and implantation rates of 57.9% versus 78.9% (P < 0.0001), 64.6% versus 72.8% (P = 0.027), 7.6% versus 18.2% (P = 0.021) and 4.3% versus 9.3% (P = 0.043) respectively. These results suggest that oocyte vitrification is associated with a better outcome than the slow-freezing method.

Risk of contamination of germplasm during cryopreservation and cryobanking in IVF units

Cryopreservation of sperm, embryos and, more recently, oocytes plays an important and increasing role in assisted reproduction, due to improvements of old, and introduction of new technologies. In parallel, concerns are increasing about the technical and biological safety of these procedures. However, published data regarding the confirmed or theoretical hazards of these procedures are sparse and sometimes contradictory. The purpose of this review will summarize data and opinions about one of the most disputed risks, the potential hazard of contamination and disease transmission through cryopreservation. Special attention is concentrated on the weak points of the technology including open vitrification systems, sterilization of liquid nitrogen and safety of commonly used storage tanks including straws and cryovials. Suggestions are also made for practical measures to avoid these dangers while preserving the benefits and perspectives of new cryopreservation technologies.

Vitrification of isolated mice blastomeres using a closed loading device

Isolated blastomeres obtained by embryo biopsy serve mainly for preimplantation genetic screening. Blastomeres are undifferentiated embryonic cells that include all the embryo genetic information. A lot of developing technologies may benefit by the efficient cryopreservation of blastomeres for future potential use, especially for stem cell culture and differentiation control. We are hereby reporting for the first time the feasibility of preserving individual isolated blastomeres in microvolumes in a closed vitrification system. Using a cryotip and propagation in microvolumes, isolated mice blastomeres were vitrified and warmed with 100% post-warming survival.

Successful vitrification of human amnion-derived mesenchymal stem cells

BACKGROUND

A cryopreservation protocol for human amnion-derived mesenchymal stem cells (HAMs) is required because these cells cannot survive for long periods in culture. The aim of this study was to determine whether vitrification is a useful freezing method for storage of HAMs.

METHODS

HAMs were cryopreserved using vitrification method. The morphology and viability of thawed HAMs was evaluated by Trypan Blue staining. The expression of several embryonic stem cell (ESC) markers was evaluated using flow cytometry, RT-PCR and immunocytochemistry. Von Kossa, Oil Red O and Alcian Blue staining were used to asses the differentiation potential of thawed HAMs.

RESULTS

The post-thawing viability of HAMs was 84.3 +/- 3.2% (Mean +/- SD, n = 10). The thawed HAMs showed morphological characteristics indistinguishable from the non-vitrified fresh HAMs. The expression of surface antigens (strong positive for CD44, CD49d, CD59, CD90, CD105 and HLA-ABC; weak positive for HLA-G; negative for CD31, CD34, CD45, CD106, CD117 and HLA-DR) and the expression of ESC markers [CK18, fibroblast growth factor-5, GATA-4, neural cell adhesion molecule, Nestin, Oct-4, stem cell factor, HLA-ABC, Vimentin, bone morphogenetic protein (BMP) 4, hepatocyte nuclear factor 4 alpha (HNF-4 alpha), Pax-6, alpha-fetoprotein, Brachyury, BMP-2, TRA-1-60, stage-specific embryonic antigen (SSEA-3, SSEA-4)] were maintained in the vitrified-thawed HAMs. The thawed HAMs retained ability to differentiate into osteoblasts, adipocytes and chondrocytes under appropriate culture conditions.

CONCLUSIONS

Our results suggest that vitrification is a reliable and effective method for cryopreservation of HAMs.

A live birth after transfer of a day 2 embryo derived from frozen-thawed zygotes that had undergone polar body biopsy: a case report

OBJECTIVE

To present a live birth after freezing and thawing of biopsied oocytes.

DESIGN

Case report.

SETTING

Artificial reproduction unit of a university hospital.

PATIENT(S)

A primary infertile couple with asthenoteratozoospermia and repeated failures of intracytoplasmic sperm injection (ICSI).

INTERVENTION(S)

Screening of aneuploidy during the fourth ICSI cycle with polar body biopsy (PB) for repeated failures of artificial reproductive techniques and a transfer of a cryopreserved day 2 embryo derived from cryopreserved zygotes with slow-rate freezing after PB.

MAIN OUTCOMES MEASURE(S)

Live birth, viability, and survival.

RESULT(S)

A successful pregnancy and a live birth were presented after a transfer of day 2 embryos derived from oocytes that underwent PB and subsequent cryopreservation.

CONCLUSION(S)

Pregnancy can be obtained subsequent to cryopreservation and thawing after PB.

Cryotop vitrification of human oocytes results in high survival rate and healthy deliveries

Vitrification, an ultra-rapid cooling technique, offers a new perspective in attempts to develop an optimal cryopreservation procedure for human oocytes and embryos. To further evaluate this method for human oocytes, 796 mature oocytes (metaphase II) were collected from 120 volunteers. Since Italian legislation allows the fertilization of a maximum of only three oocytes per woman, there were 463 supernumerary oocytes; instead of being discarded, they were vitrified. When, in subsequent cycles, these oocytes were utilized, 328 out of 330 (99.4%) oocytes survived the warming procedure. The fertilization rate, pregnancy rate and implantation rate per embryo were 92.9, 32.5 and 13.2% respectively. Thus, as already reported in the literature, the vitrification procedure seems to be highly effective, safe (since healthy babies have been born) and easy to apply. In situations where embryo cryopreservation is not permitted (as in Italy), there is now good indication for routine application of the method, once further standardization is achieved.

Aseptic vitrification of human germinal vesicle oocytes using dimethyl sulfoxide as a cryoprotectant

OBJECTIVE

To evaluate the viability of vitrified human germinal vesicle (GV)-oocytes to mature to metaphase II (MII) stage after "rapid" cooling directly in liquid nitrogen in comparison with "slow" cooling in a closed 0.5-mL straw (aseptic system), with or without dimethyl sulfoxide (DMSO) in vitrification solution. The possibility of avoiding parthenogenesis of the oocytes after vitrification using DMSO was investigated.

DESIGN

In vitro maturation after vitrification.

SETTING

Assisted reproduction centers.

PATIENT(S)

Patients undergoing standard superovulation treatment and having GV-oocytes after follicular puncture.

INTERVENTION(S)

The GV-oocytes were vitrified with long/short exposure to DMSO using slow or rapid cooling, then warmed and matured in vitro.

MAIN OUTCOME MEASURE(S)

Maturation after warming.

RESULT(S)

Oocyte development up to MII stage after vitrification with DMSO was 71% in the group with "rapid" cooling, and in groups with "slow" cooling, 68% and 72% for long and short exposure to DMSO, respectively. The maturation rate of GV-oocytes after slow cooling without DMSO was 51%. In the vitrification with long-term contact of oocytes with DMSO group, a high rate of parthenogenesis was observed. When vitrification with short-term contact of oocytes with DMSO at room temperature was used, no parthenogenesis was observed.

CONCLUSION(S)

Cryopreservation of human GV-oocytes in open-pulled straws OPS) using an aseptic slow cooling method gives high maturation rates but only in combination with DMSO. To avoid spontaneous parthenogenesis, the exposure to DMSO must occur for a reduced time and at room temperature.

Effective method for in-vitro culture of cryopreserved human ovarian tissue

It is widely accepted that it is possible to successfully cryopreserve human ovarian tissue by direct plunging into liquid nitrogen using permeable cryoprotectants only, without disaccharides. This study aimed to search for and test a new method for in-vitro culture of vitrified tissue. Ovarian biopsies were obtained during operative laparoscopy. Pieces of ovarian tissue were vitrified and warmed. After warming, tissue pieces were randomly distributed into three groups for further culture: in 2 ml of culture medium which was regularly renewed (group 1), in 30 ml of culture medium without agitation (group 2) and in 30 ml of culture medium with agitation (group 3). During the 2-week and 6-week culture, the growth of follicles within the vitrified-warmed ovarian tissue pieces was investigated. After 2 weeks of culture, mean numbers of non-degenerated follicles per mm(2) of tissue were 1.5, 1.7 and 4.5 for groups 1, 2 and 3 respectively (groups 1 and 2 versus group 3, P < 0.05). Agitation during culture of ovarian tissue is beneficial, and can be used as a prognostic tool for future warming and autotransplantation of ovarian tissue.

Are programmable freezers still needed in the embryo laboratory? Review on vitrification

The predictable answer to the provocative question of whether programmable freezers are still needed in the embryo laboratory is an even more provocative 'no'. However, such a radical statement needs strong support. Based on the extensive literature of the past 5 years, the authors collected arguments either supporting or contradicting their opinion. After an overview of the causes of cryoinjuries and strategies to eliminate them, the evolution of vitrification methods is discussed. Special attention is paid to the biosafety issues. The authors did not find any circumstance in oocyte or embryo cryopreservation where slow freezing offers considerable advantages compared with vitrification. In contrast, the overwhelming majority of published data prove that the latest vitrification methods are more efficient and reliable than any version of slow freezing. Application of the proper vitrification methods increases the efficiency of long-term storage of stem cells and opens new perspectives in cryopreservation of oocytes, both for IVF and somatic cell nuclear transfer. However, lack of support from regulatory authorities, and conservative approachs regarding novel techniques can slow down the implementation of vitrification. The opinion of the authors is that vitrification is the future of cryopreservation. The public have the final say in whether they want and allow this future to arrive.