الفهرس 
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Abstract
Cryopreservation of human spermatozoa is considered an important step in assisted reproductive techniques in andrology laboratory and fertility centers. Cryopreservation offers a preventive pretherapeutic possibility of preserving progenity in patients with testicular tumours or other malignancies where impairment of testicular function is expected. Also, patients with obstructive azoospermia and spinal cord lesions can benefit from cryopreservation.
The cryopreserved sperm is chosen according to several parameters e.g. viability, morphology, motility and concentration. All these factors affect the sperm recovery after thawing and its fertilization capacity.
According to the previous studies, cryopreservation can be applied to either seminal, epididymal or testicular sperm. Each type has its own preparation method. The seminal sperm can be prepared by special processing techniques to obtain the best quality of sperm after thawing such as swim–up technique and density gradient concentration.
Cryopreservation of spermatozoa can be applied by conventional method i.e. gradual freezing at -196oC in liquid nitrogen followed by gradual thawing at 37oC in a water bath.
While the recent method of vitrification in which rapid freezing at -196oC in liquid nitrogen and rapid thawing at 37oC has been proven to be superior to the conventional method to get a suitable sperm for IVF or ICSI.
It is inevitable to add a cryoprotective agent during sperm cryopreservation to protect the sperm from osmotic injury and formation of intracellular ice crystals by the effect of ROS, emerged during cryopreservation, in changing phospholipids: cholesterol ratio in the cell membrane. These cryoproctants include glycerol, HSPM and TEST-yolk buffer. Pentoxifylline as a sperm enhancer can also be added during cryopreservation process to improve sperm motility and fertilization capacity.
Deleterious outcome of sperm cryopreservation should be considered especially control of bacterial and viral infections loaded in the sperm itself e.g., hepatitis C virus and HIV. Moreover, ethical consideration towards cryovials for dead patients which should be burnt out after death to keep cryopreservation of human spermatozoa valuable and reliable step in ART.