ICSI, IMSI, PICSI
The quality of sperm is of great importance for the effectiveness of in vitro fertilization. During a standard IVF procedure, one spermatozoid of the best quality penetrates the ovum, the remaining tens of thousands ensure the penetration of this one.
ICSI (intracytoplasmic sperm injection). If the number of spermatozoa is small or their activity is reduced, the embryologist resorts to the ICSI procedure — sperm injection into the cytoplasm of the egg cell. The manipulation is carried out at magnification by 400 times, with the help of holding and injection needles. For ICSI, the fastest morphologically normal spermatozoid is selected. It is immobilized and placed into a microneedle. Then while holding the egg on the micro-suction cup, an embryologist pierces the egg shell with a micro-needle and injects the spermatozoid into it.
Initially, the ICSI method was introduced to treat the most severe cases of male infertility, but it proved to be so effective that it is increasingly used as the main method of fertilization without additional indications.
Indications for ICSI:
- a decreased number of spermatozoa;
- reduced sperm motility;
- numerous pathological forms of spermatozoa;
- combined sperm pathology;
- fertilization with spermatozoa thawed after freezing;
- fertilization with oocytes thawed after freezing;
- absence of spermatozoa in sperm (azoospermia), when spermatozoa are retrieved surgically from a testicle (TESE) or epididymis (PESA);
- obtaining spermatozoa from urine in case of retrograde ejaculation;
- immunological infertility (positive MAR test);
- fertilization failure after conventional IVF.
IMSI. With male infertility and a considerable decrease in the number of spermatozoa that have normal morphological characteristics, the search for a suitable spermatozoid for fertilization grows much more difficult. In this case IMSI technology (intracytoplasmic injection of morphologically selected spermatozoa) is used — a relatively new technique that allows choosing the best sperm cell at magnification by 6,600 times. This magnification allows specialists to determine the smallest changes in the morphology of spermatozoa.
Selection of spermatozoa at IMSI is a very long and laborious process. In particularly difficult cases, the search for a normal spermatozoid can last several hours. The use of IMSI reduces the risk of having a child with congenital malformations.
PICSI. In addition to the morphological structure, maturity of spermatozoa is important for their selection for ICSI. If there are a lot of immature forms in sperm, it is necessary to use the PICSI method (Physiological Intracytoplasmic Sperm Injection, physiological ICSI), which allows choosing the best spermatozoid for ICSI taking into account its physiological maturity.
The envelope surrounding the egg contains a natural hyaluronan biopolymer. In natural conditions mature spermatozoa only come into contact with it as they have a complete set of receptors necessary for fertilization. As a result, one of the mature spermatozoa penetrates into the egg cell.
The ability of mature spermatozoa to get bound with hyaluronan is in the basis of the PICSI method, which allows reconstructing the natural fertilization process as closely to natural conditions as possible and predicting behavior of a spermatozoid during fertilization.
PICSI makes use of special plates on the bottom of which this biopolymer is applied. When on such a plate spermatozoa get bound with hyaluronan, by the nature of the bond the embryologist can identify the most suitable spermatozoa for carrying out PICSI. Later on from the selected spermatozoa the best ones can be chosen based on their morphological characteristics.
Research has shown that when carrying out PICSI, bonds with hyaluronan are formed by spermatozoa that have less DNA damage and fewer chromosomal abnormalities than those selected on the basis of exclusively morphological characteristics. PICSI gives the best quality of embryos, increases the likelihood of implantation and reduces the chances of abortion.
However, with ‘good’ sperm PICSI practically does not affect the result. In order to understand whether PICSI is needed in a particular case, an HBA test (Hyaluronan binding assay) is carried out.
Indications for PICSI:
- NBA test <= 65%;
- a high level of DNA fragmentation;
- poor quality of embryos in previous attempts;
- repeated absence implantation in previous ART attempts;
- repeated incidents of spontaneous abortions in previous ART attempts;
- a low content of morphologically normal spermatozoa forms;
- low fertilization after IVF or ICSI;
- age of a woman> 38.