Ultrastructure of preimplantation genetic diagnosis-derived human blastocysts grown in a coculture system after vitrification

A comprehensive review and update on human fertility cryopreservation methods and tools

The broad conceptualization of fertility preservation and restoration has become already a major concern in the modern western world since a large number of individuals often face it in the everyday life. Driven by different health conditions and/or social reasons, a variety of patients currently rely on routinely and non-routinely applied assisted reproductive technologies, and mostly on the possibility to cryopreserve gametes and/or gonadal tissues for expanding their reproductive lifespan. This review embraces the data present in human-focused literature regarding the up-to-date methodologies and tools contemporarily applied in IVF laboratories' clinical setting of the oocyte, sperm, and embryo cryopreservation and explores the latest news and issues related to the optimization of methods used in ovarian and testicular tissue cryopreservation.

Viability assessment using fluorescent markers and ultrastructure of human biopsied embryos vitrified in open and closed systems

RESEARCH QUESTION

Are there any differences in viability and ultrastructure amongst embryos biopsied on Day 5 versus Day 3 following vitrification in open and closed systems and compared to fresh embryos?

DESIGN

One hundred human embryos (40 blastocysts biopsied on Day 5 and subsequently vitrified in open or closed systems and 60 Day 3 biopsied embryos that developed to blastocysts but were rejected for transfer following preimplantation genetic testing for monogenic/single gene defects and for aneuploidies were either treated fresh [n = 20] or vitrified [n = 40] in open or closed systems) and following warming and culture for 4 h were subjected to viability staining with carboxyfluorescein-diacetate succinimidylester/propidium iodide or processed for transmission electron microscopy.

RESULTS

No statistically significant differences were observed in the viability of human biopsied embryos following vitrification in open and closed systems. Compared to fresh embryos, vitrified ones had a higher incidence of damage (propidium iodide-stained cells) irrespective of the vitrification method (P = 0.005). These damaged cells were more prominent in Day 5 biopsied blastocysts and mainly located at the position of cutting. Characteristic lipofuscin droplets (representative of apoptosis) and a higher number of vacuoles and distension of mitochondria were also more evident in vitrified embryos, although this was not statistically assessed.

CONCLUSIONS

Vitrification in open and closed systems does not adversely affect the viability and ultrastructure of Day 5 and Day 3 biopsied embryos as revealed by the minimal yet statistically significant cell damage observed. This damage may be compensated by the embryos, which in their attempt to fully recover following vitrification, potentially enable 'rescue' processes to eliminate it.

Survival, re-expansion and cell survival of human blastocysts following vitrification and warming using two vitrification systems

PURPOSE

This study evaluated and compared survival, re-expansion, and percentage of live cells of individual Days 5 and 6 human blastocysts that were vitrified and warmed with the Vit Kit Freeze/Thaw (Irvine Scientific, CA), or with two protocols using the Global Fast Freeze/Thaw Kits (LifeGlobal, Canada).

METHODS

Frozen/thawed Day 2-3 or discarded embryos were cultured to blastocyst (culture day 5-6). Group 1 blastocysts were vitrified with the Vit Kit (n = 29) and High Security Vitrification (HSV) devices. Group 2 (n = 47) and Group 3 (n = 48) blastocysts were cryopreserved with the Global Fast Freeze Kit and 0.25 ml straws, using a direct plunge or a -100 °C holding step, respectively. Group 4 (Controls, n = 30) were not vitrified. Blastocysts were subsequently cultured for 24 h, assessed for survival and expansion, and then stained individually with propidium iodide and Hoechst. Live and total cell number was assessed with ImageJ (NIH), and the percentage of live cells calculated for each blastocyst.

RESULTS

The percentage of live cells was not different between vitrified and control (non-vitrified) blastocysts, thus vitrification did not affect cell survival. Survival (following thawing and after 24 h culture), re-expansion, and percentage of live cells were not different for blastocysts vitrified and warmed between the two vitrification/warming kits, or between the two protocols for the Global Fast Freeze/Thaw Kits.

CONCLUSIONS

Blastocyst vitrification can be achieved with equal success using simplified protocols and cheaper and easy to load freezing straws, providing simultaneously increased safety, and efficiency with lower cost, when compared with vitrification using specialized embryo vitrification devices.

A new safe, simple and successful vitrification method for bovine and human blastocysts

This study examined a new method for vitrification of blastocysts that is safe, simple and easy to learn and use. Current vitrification techniques have shortcomings that include the use of dimethyl sulphoxide, one of the more toxic cryoprotectants, and minute containers that are difficult to handle and are usually open to contamination. Cell handling and loading times are very short, which allows no room for user-associated errors and increases the difficulty of the procedure. This study describes a method of vitrification without these shortcomings. Human and bovine blastocysts were exposed to a series of three cryoprotectant solutions and loaded into a 0.25 ml sterile straw, heat sealed at both ends and vitrified. This technique allowed sufficient time for cryoprotectant exposure, loading, sealing and vitrification. Research blastocysts were thawed, cultured for 24 h, and stained for cell viability. The majority survived and on average had few lysed cells. In clinical studies from three different centres, 81.4% of vitrified blastocysts were intact after thawing. Out of 43 transfers with 76 blastocysts replaced, 44.7% implanted, 43.4% yielded a fetal heart beat, and a total of 32 babies have been delivered or are ongoing. The overall clinical pregnancy per transfer rate was 60.4%. The high survival rates and clinical pregnancy rates obtained with this new, safe and easy-to-use vitrification procedure are encouraging.

Vitrification of preimplantation genetically diagnosed human blastocysts and its contribution to the cumulative ongoing pregnancy rate per cycle by using a closed device

OBJECTIVE

To evaluate the survival rate and clinical results of our vitrification procedure on preimplantation genetic diagnosis (PGD) blastocysts and to calculate its actual contribution to the reproductive outcome per cycle.

DESIGN

Retrospective clinical study.

SETTING

University Institute IVI, Valencia, Spain.

PATIENT(S)

Patients who requested cryotransfer of surplus PGD blastocysts after failed fresh elective transfer.

INTERVENTION(S)

Retrospectively collected data during 2 years of experience with blastocyst vitrification.

MAIN OUTCOME MEASURE(S)

Primary outcome measures were the following: blastocyst recovery and survival; cryotransfer cancellation; and the implantation, pregnancy (PR), and ongoing-pregnancy rates. The secondary outcome measure was cumulative ongoing PR (COPR).

RESULT(S)

Cocultured vitrified PGD blastocysts were recovered and progressed in development after overnight culture (survival rate) at rates comparable to those of non-PGD blastocysts (49% and 42%, respectively). After transfer to 64% of patients, no statistical differences were found between PGD and non-PGD blastocyst groups concerning the following: PR (44% vs. 37%), implantation rate (40% vs. 27%), and ongoing-pregnancy rate (32% vs. 37%). Moreover, blastocyst vitrification significantly increased the COPR in both PGD and non-PGD cycles, from 47% (62/133) to 53% (70/133) and from 45% (24/53) to 53% (28/53), respectively.

CONCLUSION(S)

A preimplantation genetic diagnosis blastocyst vitrification procedure showed survival rates and improvements on the COPR that were comparable to those in non-PGD blastocyst cycles. Moreover, vitrification of biopsied and diagnosed embryos at the more advanced stages instead of at earlier cleavage stages is presented as an attractive strategy to consider in PGD programs.