Embryo Biopsy Caryn Costa Trainee Center for Reproductive Medicine Cleveland Clinic
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Embryo Biopsy
Caryn CostaTrainee
Center for Reproductive MedicineCleveland Clinic
Summary
What is Embryo Biopsy.
What is the need for Embryo Biopsy.
How is embryo biopsy performed.
What is embryo biopsy
Procedure which involves removal of one or morenuclei from early embryos (Blastomere) or pre-implantation blastocyst (Trophectoderm).
Biopsy steps 1. Opening the zona pellucida2. Removal of the cellular material
PGT – Pre Implantation Genetic Testing
Biopsied samples are used for PGT.
Identify mutations in a gene sequence or aneuploidy.
Unaffected/euploid embryos can be selected.
Decrease pregnancy terminations and births withgenetic abnormalities.
Presenter
Presentation Notes
The primary goal of PGT is to identify genetic defects in embryos, like gene mutations and aneuploidy, before transferring them to the uterus, thus decreasing pregnancy terminations and births with genetic abnormalities
What are the different types of pre-implantation genetic testing?
Pre-implantation genetic diagnosis (PGD) One or both parents carry genetic abnormalities, diagnosis is
performed on the resultant embryo.
Pre-implantation genetic screening (PGS) Genetic parents are known or presumed to be genetically
normal and their embryos are screened for aneuploidy.
Indications
PGD PGS
Single gene disorders Women of advanced maternal age
Triple repeat disorders History of recurrentpregnancy loss
Human leukocyte antigen (HLA) matching
Repeated IVF failure
Carriers of structural chromosomal abnormalities
Severe male infertility
Female carriers of x-linked disorders
Sex selection
PGT - Flowchart
Ovarian hyper stimulation
Egg retrieval
In-vitro fertilization/Intracytoplasmic sperm injection
Embryo Biopsy
Embryo testing
Embryo transfer
When to perform biopsy? Polar body. Genetic analysis of the polar body extruded from the oocyte. Gives an accurate chromosomal evaluation of the oocyte. This approach gives no clue on the paternal contribution to
the embryo, and so it is unable to specify whether the participating sperm presents any genetic abnormality.
Day 3 (cleavage). Requires the extraction of one of the theoretical eight
blastomeres of the embryo. The embryo has the ability to compensate this loss, but it
also presents a higher risk from the technical point of view.
When to perform biopsy?
Day 5 (blastocyst).
o Once the embryo has reached the blastocyst stage, mechanical manipulation is safer, since the inner cell mass (ICM) can be left aside while extracting several cells form the trophectoderm (TE).
o Also, potential genetic abnormalities or aneuploidies which occurred during meiosis are likely to have been resolved at this point.
Zona Opening Procedures
Mechanical Partial Zona Dissection(PZD)
The embryo is held with a holding pipette while a microneedle is used to pierce the zona pellucida.
The embryo is released from the holding pipette, which isused to cut the ZP against the microneedle.
Also useful for Assisted Hatching.
Chemical Zona Drilling
Acid Tyrode (pH 2.3)
Larger, rounder hole than with PZD
Two separate pipettes are usually used (double holder). Drilling pipette with an inner ø of 5-7 μmplus the aspiration pipette.
Target site: between two blastomeres.
Embryo wash after AT exposure is recommended.
Chemical Zona Drilling
Limitations
Size cannot be controlled
Limiting the extent and duration of AT exposure is necessary to avoid acidification of medium and cell lysis
Laser-assisted zona opening
Microdissection of zona pellucida using a 1.48 μm diode laser beam.
Easily adapted to the microscope. Laser is transmitted trough a 45X objective.
Laser-assisted zona opening
Minimal, Superficial damage.
A direct relationship between the hole diameter (μm) and the exposure time (ms).
Safe, with no mechanical, thermal or mutagenic effects.
Increased implantation rate.
Early Embryo (Blastomere) biopsy
Methods of blastomere removal Aspiration The blastomere is aspirated with the biopsy pipette and
pulled out of the embryo
Methods of blastomere removal Displacement Two holes are made, media is injected through one hole and
the blastomere is displaced out of the other hole
Methods of blastomere removal Extrusion The embryo is pushed, causing the blastomere to come out
of the hole
Advantages and limitations of blastomere biopsy
Pre-implantation embryo (Blastocyst) Biopsy
Preimplantation embryo – Blastocystbiopsy strategies
Day 3 The hole is made on the third day of development and the
herniated cells are removed on day five.
Day 5 The hole is made on day 5 at the pole opposite to the inner
cell mass. The blastocysts are then left for 4-24 hours untilsome trophectoderm herniates through the slit. Whenherniation involves about 25% of the blastocyst, thetrophectoderm is excised.
Advantages and limitations of blastocyst biopsy
Conclusion Embryo Biopsy is the removal of one or more nuclei from
embryos for genetic testing.
The genetic testing can help prevent the births with geneticabnormalities and pregnancy terminations.
Microdissection of zona pellucida is usually made using eitheracid or a laser beam and removal of cells can be performedeither at D3 or D5.
Choice between biopsy on early embryos (D3) or on pre-implantation embryos (D5) should be made considering theET strategy and personnel experience.
Thank You !
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