Cryopreservation of Spermatozoa

Abstract

Cryopreservation of sperm has many applications in agriculture, biotechnology, and clinical medicine. The spermatozoon is a very specialized cell that loses the ability of biosynthesis, repair, growth and cell division during the final phase of spermatogenesis. Cryopreservation of sperm generally requires a reduction or arrest of the metabolism of cells, thereby prolonging their life. Semen samples of mammalian species are diluted with a suitable diluent [containing a complex extender (e.g., egg-yolk, milk, milk-whey), cryoprotectant (e.g., glycerol)] and processed through different freezing protocol prior to storage in liquid nitrogen (-196°C). Despite the use of complex media and cryoprotectants, a substantial portion of the cells die during freezing and thawing (recovery rate do not exceeds more than 50%). As the complex media contain large numbers of undefined biomolecules (proteins, lipids, carbohydrates), it is difficult to analyze the beneficial/detrimental effects of a particular compound on sperm cryopreservation. In the present book chapter we have briefly discussed the knowledge and limitations of the current semen cryopreservation technology and mainly focused on the development of a simple cryopreservation model using chemically-defined medium and goat cauda-epididymal sperm. Using this model system, several novel cryoprotectants have been identified and biochemical basis of sperm membrane damage during cryopreservation has been investigated.