Rajvi H Mehta
03 August 2007
The birth of the first baby following Intracytoplasmic Sperm Injection (ICSI) into the oocyte was a result of serendipity or more so a technical ‘error’. Subsequently, this technique has been used for the treatment of male infertility due to low sperm counts and now has become an important tool in the field of assisted reproductive technologies.
One of the greatest challenges that a clinical embryologist performing ICSI faces is the ‘selection’ of the ‘right’ sperm for ICSI. Undoubtedly, the quality of the sperm determines the outcome of ICSI with reference to the occurrence of normal fertilization and the development of a normal embryo. The only method routinely used is to ‘visually’ select a sperm normal in appearance and use the same for injection. This method of selecting the sperm has both intrinsic and practical limitations.
The speed with which the process of ICSI is carried out is crucial and therefore, it is very unlikely that one can critically evaluate the morphological status of the sperm. A sperm that may morphologically appear normal may not essentially be genetically normal. Furthermore, the incidence of chromosomal abnormalities in spermatozoa is much higher in sperms from oligozoospermic and teratospermic men (Colombero et al; 1999) and it is these individuals who would be more likely to require ICSI. Therefore, the chances of selecting a genetically abnormal sperm in a visually normal appearing sperm is quite high. Taking these limitations into consideration, constant attempts are being made to develop a more objective method to ‘select’ the right sperm for ICSI.
The Hypo Osmotic Swelling Test was developed by Schrader et al in 1986 as a means to evaluate sperm membrane integrity and sperm viability. Later, Ved et al (1991) utilized this test for the detection of viable sperms when ICSI was to be performed in a case of total asthenozoospermia. However, this technique for sperm selection for ICSI could not be extended to all cases of ICSI because a sperm with good membrane integrity need not essentially have normal genetic material!
Bartoov et al (2002) from Israel made an attempt to determine the sperm morphology at a very high magnification (6300 x) and reported that optimal selection of sperm utilizing this method led to an improvement in pregnancy rate. But, the clarity and resolution of an image enlarged 6300x times became questionable. And, this method too did not find its way into routine use.
In the last ESHRE meeting, a South Korean group led by Dr. Pang at the Chung-Ang University in Gyeonggi-Do, reported that combined fluorescence in situ hybridisation (FISH), in which fluorescent DNA labels are used to identify whether chromosomes are missing, with the HOS test could facilitate the process of sperm selection for ICSI. Pang and his team analysed more than 16,000 sperms from three fertile men and six with low sperm counts, and found that the quality of osmotic swelling varied with reference to the chromosomal number. When this ‘special’ HOS method was used to select sperm from oligozoospermic men, there was a 20-fold decrease in the frequency of aneuploidy in the selected sperm compared with when no selection was used.
If the findings of this group are observed by other clinical embryologists then we may soon have an objective and more reliable method of ‘selection’ of sperms for ICSI.
References:
Schrader SM, Platek SF, Zaneveld LJ, Perez-Pelaez M, Jeyendran RS. (1986) Sperm viability: a comparison of analytical methods. Andrologia. 18:530-8.
Ved S, Montag M, Schmutzler A, Prietl G, Haidl G, van der Ven H. (1997) Pregnancy following intracytoplasmic sperm injection of immotile spermatozoa selected by the hypo-osmotic swelling-test: a case report. Andrologia 29:241-242.
Colombero LT, Hariprashad JJ, Tsai MC, Rosenwaks Z, Palermo GD. (1999) Incidence of sperm aneuploidy in relation to semen characteristics and assisted reproductive outcome. Fertil Steril 72:90-96.
Bartoov B, Berkovitz A, Eltes F, Kogosowski A, Menezo Y, Barak Y.(2002) Real-time fine morphology of motile human sperm cells is associated with IVF-ICSI outcome. J. Androl 23:1-8.
|
3.80 (out of 5)
|