OVU Surrogacy & Fertility Network
Posted on 08/04/2022 in Fertility Treatment Options

What is ICSI: the risks and your chance of success?

What is ICSI: the risks and your chance of success?

The intracytoplasmic sperm injection (ICSI) technique is successfully used to resolve the most severe cases of male infertility enabling fertilizing the oocytes using the partner’s sperm. While being effective for overcoming low or absent fertilization in couples with abnormal semen parameters, ICSI is also frequently used in combination with assisted reproductive technologies for treating the other causes of infertility. The average fertilization rates with ICSI range from 70% to 80%, depending on the case.

 

Being a microsurgical procedure performed on a single oocyte, ICSI involves using a glass ICSI micropipette with extra–long parallel taper (glass needle) to aspirate and inject the one living spermatozoon directly into the oocyte), a micromanipulator (precision positioning device) to control the movement of the ICSI micropipette, and a microinjector. During ICSI, the Embryologist microinjects a single motile spermatozoon directly into the center of an oocyte, bypassing a thick extracellular coat called the zona pellucida (ZP). 

 

 

Indications for ICSI technique 

Male factor infertility:

Obstructive azoospermia (the absence of sperm cells in the ejaculate despite the testes producing enough sperm, but there is a plumbing problem that prevents the sperm from traveling out of the testes)

Non–obstructive (secretory) azoospermia (the absence of sperm cells in the ejaculate because the testes do not produce the sperm)

Oligospermia also called oligozoospermia (low sperm count and severely low sperm count in the semen) 

Cryptozoospermia (an extremely low concentration of sperm in semen)

Asthenozoospermia (sperm cells with low or absent motility)

Teratozoospermia (abnormal sperm morphology)

Anejaculation (ejaculation dysfunction)

Immune infertility: the presence of elevated levels of antisperm antibodies (immunoglobulins) binding to antigens of the gametes and interfering sperm–oocyte interaction

 

 

Female factor infertility: 

Retrieval of a low number of oocytes during follicular aspiration

Poor oocyte quality, including the cases of thick zona pellucida.

 

 

The other cases when ICSI is performed: 

Previous fertilization failures with conventional Ivf

In cases requiring PGT (preimplantation genetic or chromosomal testing) of embryos 

Cycles with epididymal or testicular sperm samples (cryopreserved and fresh)

Cycles with cryopreserved semen samples

Cycles with vitrified oocytes

Cycles with cryopreserved ovarian tissue 

Cycle with oocytes after IVM (in vitro maturation)

 

 

Revealing the mystery of ICSI 

ICSI is done in the Ivf lab using a Multi–Zone ART/Ivf Workstation. The Workstation usually is equipped with an inverted microscope which has a CCD camera that is linked to a monitor to allow for real–time visualization, micromanipulators, and microinjectors for performing fertilization. 

 

Intracytoplasmic sperm injection can be described with the following steps: (1) denudation of the oocyte from the surrounding cells, (2) selection and immobilization of a viable sperm cell, (3) aspiration of the spermatozoon before injection; (4) positioning and fixing the oocyte with the holding pipette before injection, (5) aspiration of the oocyte; (6) rupture of the oolemma before the release of the sperm into the oocyte; (7) slow release of the spermatozoon in the ooplasm; (8) accurate removal of the ICSI micropipette from the oocyte; (9) release of the oocyte after injection. 

 

 

ICSI involves microinjecting a single motile spermatozoon into the oocyte, bypassing the Zona Pellucida, and introducing the sperm cell into either cytoplasm or nucleus of the oocyte. The oocytes, denuded from their surrounding cells (cumulus and corona cells), are placed in several surrounding medium microdroplets in the ICSI dish. After that, an Embryologist drops into the ICSI dish a special solution that slows the motility of sperm and adds ±1 μL of the sperm. 

 

In the ICSI micropipette, which is filled with a special solution that prevents sperm cells from sticking to it, a single motile (the motility of the sperm cell, even if it is only a slight twitching of the tail, indicates that it is living), and morphologically normal sperm cell is aspirated. Then, the sperm cell is released in a perpendicular position to the ICSI pipette, which facilitates immobilization.

 

Immobilization of a sperm cell can be done with the ICSI needle or with a laser (laser–induced immobilization). Both techniques result in identical fertilization rates. Immobilization is essential for oocyte activation and is achieved by the release of sperm cytosolic factors via the ruptured membrane. It involves rubbing the tail with the ICSI micropipette against the bottom of the dish, which results in breakage in the midpiece region or cutting the tail below the midpiece region, or cutting halfway between the head and the tip of the tail, or dissecting the tail at the tip.

 

After immobilization, the sperm cell is again aspirated (but now tail–first) to allow the injection of a minimal volume of medium together with the sperm cell. The oocyte is held in position with minimal close touch by the holding pipette and its polar body is located at the 6 o’clock position to avoid damage to the oocyte’s spindle. 

 

The ICSI microinjection needle will be positioned just over the oocyte and then lowered slowly until a slight depression can be seen on the cell surface. After the correct needle position has been visualized, the needle is then moved slightly to prepare for an injection. Preparation for injection allows the microinjector to introduce the sperm into the oocyte using computer–controlled settings.

 

If both the holding pipette and the oocyte are in perfect focus, the injection microneedle, containing the immobilized sperm cell near the tip, can be introduced into the oocyte. The ICSI microneedle gets past the barrier of the cell (the plasma membrane) by drilling a hole in it. Passing through the zona pellucida is seamless and done by advancing the injection pipette with positive pressure. If drilling is done correctly, the oocyte membrane will close back up when the ICSI needle is removed, leaving behind minimal cellular damage.

 

In contrast, the oolemma is not always pierced by a simple injection of the ICSI needle and usually needs a little bit more pressure. If the ooplasm enters the injection micropipette, and sudden acceleration of the flow is visible, it indicates that the membrane has been ruptured. At this moment, aspiration is immediately stopped, the sperm cell is slowly released into the oocyte with a minimal volume of medium, and the ICSI pipette is accurately removed.

 

While doing intracytoplasmic sperm injection, the Embryologist controls the injection volume, injection pressure, and post–injection pressure for minimal cellular damage after fertilization. The volume of injection is limited to only spermatozoon and some solution that is to be introduced, or the oocyte could burst. The injection pressure should be higher when introducing the sperm cell inside the oocyte, and the post–injection pressure should be lower for removing the microneedle accurately but higher than the pressure used for drilling the oocyte. 

 

Without pressure control, the contents from the cytoplasm or nucleus would be forced back into the ICSI needle by a positive pressure created by the introduction of the injected material. Such a loss of cytoplasmic or nuclear material could entail the death of an oocyte.

 

 

Risks while doing ICSI 

If visualization of the ICSI process is not clear (for ex., the low–resolution microscope is used), it would interfere with fixing or releasing an oocyte using the holding pipette, as well as aspiring and injecting a spermatozoon with the injection pipette. 

 

ICSI micropipette should be filled with a special solution to prevent sticking of the sperm cell to the pipette; otherwise, the manipulation won’t be successful, and it would be also hard to control the fluid in the microinjection needle. 

 

Motility is a vital indicator of sperm viability. If there is not even a slight twitching of the tail, it seems that the spermatozoon is not alive or nearly dead, and cannot be used for fertilization. In such a case, the new one should be selected for ICSI. 

 

Despite achieving higher ICSI fertilization rates after aggressive damage to the sperm tail plasma membrane during immobilization, too aggressive damage or the damage of the other regions may lead to the death of spermatozoon.

 

If after immobilization the sperm cell is aspired head–first, it may lead to the injection of a maximum volume of medium together with spermatozoon causing the burst of the oocyte. 

 

If both the holding pipette and the oocyte are not in perfect focus, it would be easy to puncture the oocyte. 

 

Too much pressure while penetrating the oocyte’s ZP may lead to an undesirable result. If drilling is done non–correctly, the oocyte membrane won’t close back up when the ICSI needle is removed, leaving behind maximum cellular damage.

 

Sperm cell should be introduced at the moment when ooplasm enters the injection micropipette, and sudden acceleration of the flow is visible, indicating that the oolemma membrane has been ruptured. 

 

The volume of microinjection must be limited to only sperm and some solution that is to be introduced or the oocyte could burst. The same thing for the injection pressure, the sperm cell should be slowly released into the oocyte.

 

If the Embryologist doesn’t control the injection volume, injection pressure, and post–injection pressure while doing ICSI, the oocyte damage will be maximum. 

 

 

Risks after performing ICSI

While ICSI has overcome many fertilization problems, it does not completely eliminate TFF (Total Fertilization Failure).

Embryonic arrest 

Reduced number of top–quality embryos

Delayed embryo transfer

Cancelled embryo transfer

Not all Ivf–ICSI embryos left after the transfer can be vitrified for future FET cycle(s)

Implantation failure & miscarriage or ectopic pregnancy

Negative pregnancy test after embryo transfer

No heartbeat detected on high–resolution ultrasound after positive pregnancy test 

Multiple pregnancies 

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