Human Blastocyst Biopsy and Vitrification

Summary

Blastocyst biopsy and vitrification are required to efficiently conduct preimplantation genetic testing. An approach entailing the sequential opening of the zona pellucida and retrieval of 7-8 trophectoderm cells in day 5-7 post-insemination limits both the number of manipulations required and the exposure of the embryo to sub-optimal environmental conditions.

Abstract

Blastocyst biopsy is performed to obtain a reliable genetic diagnosis during IVF cycles with preimplantation genetic testing. Then, the ideal workflow entails a safe and efficient vitrification protocol, due to the turnaround time of the diagnostic techniques and to transfer the selected embryo(s) on a physiological endometrium in a following natural cycle. A biopsy approach encompassing the sequential opening of the zona pellucida and retrieval of 5-10 trophectoderm cells (ideally 7-8) limits both the number of manipulations required and the exposure of the embryo to sub-optimal environmental conditions. After proper training, the technique was reproducible across different operators in terms of timing of biopsy (~8 min, ranging 3-22 min based on the number of embryos to biopsy per dish), conclusive diagnoses obtained (~97.5%) and live birth rates after vitrified-warmed euploid blastocyst transfer (>40%). The survival rate after biopsy, vitrification and warming was as high as 99.8%. The re-expansion rate at 1.5 h from warming was as high as 97%, largely dependent on the timing between biopsy and vitrification (ideally ≤30 min), blastocyst morphological quality and day of biopsy. In general, it is better to vitrify a collapsed blastocyst; therefore, in non-PGT cycles, laser-assisted artificial shrinkage might be performed to induce embryo collapse prior to cryopreservation. The most promising future perspective is the non-invasive analysis of the IVF culture media after blastocyst culture as a putative source of embryonic DNA. However, this potential avant-garde is still under investigation and a reliable protocol yet needs to be defined and validated.

Introduction

The main goal of modern human embryology is to maximize the number live births per stimulated cycle and reduce costs, time and efforts to achieve a pregnancy. To accomplish this goal, validated approaches for embryo selection should be employed to identify reproductively competent embryos within a cohort obtained during an IVF cycle. According to the latest evidences, blastocyst culture¹ combined with comprehensive chromosomal testing and vitrified-warmed euploid embryo transfer (ET) is the most efficient framework to increase IVF efficiency². Clearly, aneuploidy testing requires an embryonic specimen, which at present i....

Protocol

The protocol for human blastocyst biopsy, here described, follows the guidelines of G.EN.E.R.A. Human Research Ethic Committee.

NOTE: Refer to the Table of Materials for materials required. Further material required entails laboratory footwear and outfit, surgical facemask, hair cover, surgical gloves, a permanent non-toxic marker, forceps and disinfectant. The use of surgical gown, disposable surgical gloves, facemask, hair cover is mandatory to prevent risk of contamination. All the working areas, as well as the equipment involved in the process, must be cleaned thoroughly with laboratory disinfectant (e.....

Results

Figure 6 represents a scheme of all the outcomes of a biopsy procedure that can be adopted to standardize the protocol and monitor the performance of each operator. The main procedural outcome is the timing to complete the biopsy/biopsies; the main technical outcome is the quality of the plot produced after genetic testing that might result in either a conclusive or inconclusive diagnosis, the latter of which requires a re-biopsy of the undiagnosed blastocyst.......

Discussion

Only well-experienced skilled embryologists who have completed their training period should perform both TE biopsy and blastocyst vitrification. Furthermore, a witness is required to monitor the procedures and guarantee an efficient traceability during i) the movements of the biopsied blastocyst from the biopsy dish (Supplementary Figure 1) to the post-biopsy dish (Supplementary Figure 1), then to the vitrification plate (Supplementary Figure 1) and lastly to the vitrifi.......

Materials

Name	Company	Catalog Number	Comments
Equipment
Cold tube rack	Biocision	XTPCR96
Electronic pipette controller	Fisher Scientific	710931
Flexipet adjustable handle set	Cook	G18674	Stripper holder
Gilson Pipetman	Gilson	66003	p20
IVF Electronic Witness System	CooperSurgical Fertility & Genomic Solutions		RI Witness ART Management System
Inverted microscope	Nikon	Eclipse TE2000-U
Laminar Flow Hood	IVF TECH		Grade A air flow
Laser objective	RI	Saturn 5
Microinjectors	Nikon Narishige	NT-88-V3
Mini centrifuge for PCR tubes	Eppendorf	CSLQSPIN	for 0.2ml PCR tubes
Stereomicroscope	Leica	Leica M80
Thermostat	Panasonic	MCO-5AC-PE
Tri-gas incubator	Panasonic	MCO-5M-PE	02/CO2
Consumables
Biopsy pipette	RI	7-71-30FB35720	30µm ID, flat 35°C
Cryolock	Cryolock	CL-R-CT
CSCM complete	Irvine Scientific	90165	IVF culture medium supplemented with HSA
Embryo Transfer Catheter	Cook	G17934
Flexipet pipette	Cook	G26712	140µm stripping pipette tip
Flexipet pipette	Cook	G46020	300µm stripping pipette tips
Holding pipette	RI	7-71-IH35/20	30µm ID, flat 35°C
Human Serum Albumin	Irvine Scientific	9988
IVF One well dish	Falcon	353653
Mineral Oil for embryo culture	Irvine Scientific	9305
Modified HTF Medium	Irvine Scientific	90126	Hepes-Buffered medium
Nuclon Delta Surface	Thermofisher scientific	176740	IVF dish 4-well plate with sliding lid
Primaria Cell culture dish	Corning	353802	60x15mm
Reproplate	Kitazato	83016
Serological pipette	Falcon	357551	10ml
Sterile disposable Gilson tips	Eppendorf	0030 075.021	200µl
Tubing Kit	Provided by the genetic lab		PCR tubes (0.2mL), loading solution, biopsy washing solution
Vitrification media	Kitazato	VT801	Equilibration and vitrification solutions
Warming media	Kitazato	VT802	Thawing and dilution solutions