Pons Medical Research

Since Robert Edwards, the Nobel Prize laureate, discovered in-vitro fertilization to help infertile couples to overcome their health issues, scientists continued to work with this method with the goal to improve it. Classical IVF is still widespread enough, according to the European Register for Assisted Reproductive Technologies (provided by the European Society of Human Reproduction and Embryology). Nonetheless, we have now additional options to choose from, according medical indications, because two new methods of artificial fertilization were invented: ICSI (Intracytoplasmic Sperm Injection) and pICSI (physiological Intracytoplasmic Sperm Injection). Let’s go into more details about each one of these methods.

There are a lot of cases of infertility, caused by combined (male+female) or just male infertility factors. This means that spermatozoa are affected in such patients and can contain genetic problems or be pathological. In usual in-vitro fertilization, clinical embryologists incubate oocytes with spermatozoa during a specific time and in some cases it can lead to two bad outcomes: one, where morphologically or genetically bad spermatozoon could fertilize an oocyte and another one, where more than one spermatozoon will fertilize an oocyte. In both situations it may lead to genetic abnormalities in embryos, which can be expressed in congenital anomalies or diseases of the future fetus.

To prevent this, the methods listed above can be used. They are very similar, but let’s catch the main point: this is a fertilization procedure, guided and controlled directly by the embryologist. Oocytes of a donor or of an intended biological mother are placed in drops of a special medium, and spermatozoa are placed in a separate medium inside the same laboratory dish. Under a strong inverted microscope, which is built into an ICSI station,the clinical embryologist selects the best spermatozoa, according to a morphological quality evaluation, and “injects” them inside the cytoplasm of oocytes, with the help of micromanipulators: one spermatozoid per one oocyte.


This procedure is not traumatic for oocytes, due to the plasticity of the oocyte membrane while at the same time preventing any abnormal fertilization by more than one spermatozoid or by pathological spermatozoa.

A little modification of this approach leaded to another method, which is called pICSI. To understand this, we need to focus on studying some of the basics of reproductive biology: to fertilize an oocyte, only a little part of the spermatozoid should get inside the cytoplasm: the content of its head. During the usual fertilization, a process called “capacitation” occurs, whose main outcome is the softening of the spermatozoid´s head membrane and the successful penetration of the genetic material into the oocyte through its membrane. The process starts because of the contact between the spermatozoid´s head and some chemical substances on the oocyte´s outer membrane, one of them being “hyaluronic acid”. Due to some genetic or acquired problems, some spermatozoa lose the capability to start the capacitation process and in consonance cannot successfully fertilize the oocyte. To overcome this problem, the embryologist will use the pICSI method: this technique is very similar to the usual ICSI, but a drop of spermatozoa is applied over a layer of hyaluronic acid, which is already located within special ICSI dishes. Spermatozoa caught up or immobilized by the layer of hyaluronic acid can then be used for fertilization in the same way as in the previous ICSI procedure.

The reproductologist doctor, together with a clinical embryologist will determine the right method according to result of some medical tests as well as the medical history of the patient.

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