PROSPECTS OF APPLICATION OF ARTIFICIAL FERTILIZATION FOR OBTAINING PIG EMBRYOS IN VITRO

Abstract

Literary data about the method using artificial insemination for receiving pigs’ embryos in vitro (intracytoplasmic injection spermatozoon in oocyte (ICSI – Intracytoplasmic sperm injection)) for application of such approach to preserve and improve the gene pool of domestic pig breeds were presented. In pig breeding there is a threat of extinction of breeds due to periodic outbreaks of infectious diseases. Scientists are constantly paying attention to the preservation of the gene pool of this species, but approaches to cryopreservation of gametes and embryos still do not provide stable and high results. Some biotechnological manipulations were only informative, although practical approaches to gene pool conservation are essential. The ICSI method is an artificial insemination of oocytes in vitro during which one spermatozoon is injected into a mature oocyte at the stage of metaphase II meiosis. It is currently well established on female oocytes, but for oocytes of other mammalian species remains insufficiently optimized to achieve the same percentage of fertilization and embryo formation. In our country there is very little data on the use of ICSI method for artificial insemination of animals, including pigs, although this method will increase the efficiency of fertilization and the formation of full-fledged pig embryos in vitro. It was shown that the level of blastocyst formation in pigs that were cleaved from thawed immature oocytes fertilized by ICSI was 5.2%. It has been proven that the efficiency of fertilization by a modified ICSI method increases when using hyaluronic acid for sperm selection called PICSI. Because only mature sperm have a receptor for hyaluronic acid, which is contained on the zona pellucida of the oocyte, so only mature spermatozoa are selected for fertilization. It has long been thought that damage to the head of the sperm leads to damage to the genetic material, which in turn leads to lack of fertilization or the formation of abnormal embryos. Therefore, among the requirements for ICSI the main was the damage of the tail and avoidance of the sperm head and neck injury. Disulfide bridges of the sperm head, which are formed through the passage through the epididymis, have been shown to make the sperm nucleus resistant to chemical and physical ruptures. Chinese scientists published in 2020 the results of studies on the treatment of oocytes during the ICSI procedure with urhodeoxycholic acid and showed that this approach increases the percentage of zygotes obtained. This phenomenon is explained by the ability of this substance to reduce oxidative stress caused during this procedure in the endoplasmic reticulum and prevent apoptosis. Thus, the ICSI method provides effective fertilization with the involvement of a minimum number of sperm, which is extremely convenient in working with extinct species and species that are on the verge of extinction. Our data on the application of the ICSI method with various modifications indicate the prospects for the application of the ICSI method for its implementation in practice.