Papel de agentes antioxidantes na criopreservação de células germinativas e embriões / Role of Antioxidants Agents in Germ Cells and Embryos Cryopreservation

ABSTRACT

Background: Antioxidants are molecules or substances able to convert the reactive oxygen species (ROS) in water, preventing its overproduction. In an attempt to reduce or eliminate oxidative stress during cryopreservation, antioxidants, especially catalase and trolox®, have been added to the freezing medium to maximize cell survival after the process of freezing / thawing. These substances have been used mainly in the cryopreservation of semen, embryos and oocytes. Given the importance of adding these agents in cryopreservation of mammal germ cells, this review aims to describe issues related to the addition of catalase and trolox® for maintaining the viability of these cells in the cryopreservation process. Review Numerous protocols for germ cells cryopreservation have achieved satisfactory results in different species, although some points of these protocols still require adjustments in order to succeed in the repeatability of results. Cryopreservation can affect negativelly cell and / or tissues viability by several factors, including the formation of intracellular ice crystals, solution effect and toxicity caused by the inappropriate use of cryoprotective agents. Currently, several studies have emphasized the damage caused by the formation of ROS during cryopreservation processes, leading to oxidative stress. ROS formed during the cryopreservation process can degrade essential molecules to cells, including the polyunsaturated lipids present in the cell membrane (lipid peroxidation), leading them to death. In order to prevent oxidative stress that occurs during cryopreservation, some researchers have tested the addition of antioxidants to the freezing medium in order to achieve higher rates of cell survival after the thawing process. Antioxidants are substances that can neutralize ROS, thus reducing its power of chemical reaction.[...]