In Vitro Fertilization Procedures
Intracytoplasmic Injection (ICSI)
ICSI is a micromanipulation procedure during which an embryologist uses an inverted microscope and micromanipulators to carefully select and place a single sperm into each egg. First, the helper cells that accompanied the egg inside the follicle are removed. Next, the prepared sperm are added to a solution which slows down their swim pattern, allowing the embryologist to observe, select and finally pick up a single sperm cell inside an injection pipette. The pipette is oriented so that minimal damage to the fragile structures inside the egg will be sustained during the injection. Finally, a single sperm is deposited inside the cytoplasm of the egg.
A human egg undergoing ICSI
Whether inseminated by standard IVF insemination or by ICSI, fertilization is checked the following day. This first day of fertilization is Day 1 of embryo culture. It is actually quite common that only 50%-70% of the eggs inseminated fertilize and this rate can change significantly based on a patient’s diagnosis. A fertilized egg is referred to as an embryo. Embryos can be cultured in the laboratory for up to 6 days. Routinely, embryos are placed back in the uterus on Culture Day 5. For the first 3 days embryos divide based on instructions from the original egg. It is not until after this stage that the embryo begins to direct its own development. After about 3 successive rounds of division, the cells should begin to become tightly associated with each other. This is the morula stage. After the morula stage, a cavity begins to form inside and the embryo finally begins to grow in size. Around Day 5 or 6 the embryo should develop into a blastocyst. The blastocyst is composed of a hollow sphere of cells, called the trophectoderm, and an inner cell mass (ICM). The trophectoderm will interact with the uterine lining cells to implant and establish a pregnancy. Inside the sphere is the ICM from which the baby develops.
A fertilized egg (embryo) with 2 pronuclei clearly visible in the center
Assisted hatching is a micromanipulation procedure by which a small breach is caused in the egg shell (the zona pellucida). The zona pellucida has an extremely important function during fertilization, it allows one sperm to pass through to the egg and then becomes impenetrable to any other sperm. This is essential for development as the sperm is carrying half of the chromosomes necessary for a human being to develop and the egg is carrying the other half. If there are missing or extra copies of any chromosome, this will severely inhibit development to a healthy human being. However, when the embryo needs to interact with the uterine lining in order to implant, the zona pellucida becomes a barrier. All embryos must hatch from their zona pellucida in order to establish a pregnancy. In some cases, an inability of an embryo to do this unassisted can be the root cause of infertility. At NYU Langone RS of NY an extremely accurate focused diode laser can be used to make an incision in the zona pellucida.
A hatching blastocyst with cells blebbing from the breach visible at 5 o’clock
Cryopreservation is a way to hold cellular tissue indefinitely at a temperature which is so low that metabolic activity ceases. Without metabolic reactions taking place, these cells do not age in any way; essentially, time has stopped for them. Reproductive tissue can be cryopreserved at any point in time, although the success rates will vary based on what type of tissue and what method of cryopreservation is used. Cryopreservation of testicular and ovarian tissue can be performed for young patients who are facing imminent chemotherapy or radiation which can have devastating effects on their ability to reproduce in the future. This tissue can be removed from the body, cryopreserved and stored for use at a much later date when the patient is disease free and ready to start a family, although these options are considered experimental as the clinical reports of these procedures are currently limited.
Cryopreservation of sperm, embryos, and eggs on the other hand has been in use clinically for many years now. Cryopreservation of sperm from the ejaculate can be performed for men of puberty age and older who simply may not be available or able to produce a sample on the day of the scheduled IUI/IVF procedure or for fertility preservation. Cryopreservation of eggs can be performed for female patients who simply wish to preserve their fertility options for the future. Cryopreservation of embryos can be performed for patients who are able to go through the IVF procedure, but are not able to establish a pregnancy until a later date. Cryopreservation of embryos can also be performed if the patient has embryos in culture in excess of the number they wish to transfer back to their uterus. These embryos can remain in storage for many years and still yield good survival rates upon thawing.
NYU Langone RS of NY has two New York State Department of Health licensed tissue banks where your tissue can remain in storage under our care until such time that you are ready to use it to attempt to establish a pregnancy. NYU Langone RS of NY is also able to accept a patient’s previously frozen tissue from other facilities. Our staff is well educated and experienced in many protocols. We can obtain the necessary protocol from the facility which originally cryopreserved the tissue so that we can handle it with the utmost care. If the tissue was frozen at a facility which does not hold a New York State Department of Health license, a request must first be filed with that agency before we can accept the tissue in our tissue bank.
Embryo biopsy is a micromanipulation procedure in which a sample of the preimplantation embryo is taken. Preimplantation embryos are comprised of cells which are pluripotent, meaning each cell’s ultimate developmental fate has not been determined yet and they have the ability to give rise to multiple tissue types. This allows the embryologist to remove one or more of these cells without inhibiting the embryo’s ability to develop into a term baby. The sample can be sent to a genetics lab which specializes in this type of genetic testing (preimplantation genetic diagnosis or PGD) and the embryo is kept in culture here at NYU Langone RS of NY (or occasionally cryopreserved) until results are received.
A Day 3 embryo with one cell removed for genetic analysis