At the time of ejaculation, millions of sperms are deposit by into the upper part of vagina from where the sperm travel the female genital track to reach the oocyte and fertilization occur. In humans, all the about 10% of ejaculated spermatozoa will enter the cervix, 1% the uterus and 0.1 % the fallopian tube, thus a diminutive percentage of ejaculated sperm reached the oocyte. Eventually single spermatozoa fertilized the egg. This proved that the female genital track place and active and straight role in selected the best sperm essential for producing a healthy offspring.
Conventional sperm preparation technique (swim up, density gradient, etc.) bypass to wearying technique extents the natural selection process taking place in female genital track. In case of ICSI, all natural barriers are bypassed, and the entire sperm is introduced into the oocyte. Since sperm DNA damage cannot be assessed real time visually, there is a high chance of sperm with DNA fragmentation being injected into the oocyte, subsequently resulting to pregnancy loss.
Thus, conventional sperm preparation technique might not necessarily select the most competent spermatozoa. To overcome this issue, advanced sperm selection techniques have been devised based on physiological selection procedure. One of the chief principles involves molecular binding.
Hyaluronic acid is chief component of the extra cellular matrices of the cumulus. In the human, plasma membrane remolding is known to take place during the final stage of spermatogenesis that facilitates binding of the male germ cell hyaluronun and the zona pellucida. The human sperm has HA receptor, of which at least three hyaluronun binding protein are involved in crucial steps like sperm maturation, acrosome reaction, motility, hyaluronized activity, and sperm zona binding.
A petri dish, with immobilized hyaluronic acid on it, comprises the PICSI dish. Prepared spermatozoa suspension are placed over there spots of HA and incubated at 37degree Celsius for 15 minutes. By gently rinsing the HA droplet, the frequently moving spermatozoa are removed thus removing the unbounded sperms. The bounded spermatozoa are picked with ICSI injection pipette and injected into the oocyte.