Seisenbayeva A.S., Toishibekov Y.M., Iglmanov U.I., Valieva B.A., Yessimsiitova Z.B. Influence of various cryoprotectors on survival of sheep’s ovarian tissuewith freezing in vapors of liquid nitrogen

1Institute of Experimental Biology named after F. Mukhamedgaliyev, Kazakhstan, Almaty 2Al-Farabi Kazakh National University, Kazakhstan, Almaty

Abstract

Biological diversity is the key to maintaining life. Therefore preservation of biodiversity is important for sustaining a healthy Earth, but it also is immensely valuable to
the health and lifestyle of human society. Today new methods of auxiliary reproductive
technology allow using them not only for preservation of reproductive potential of the
person, and also for preservation a biodiversity of wild and endangered species of farm
animals. Captive breeding programs, genetic resource banks and artificial reproductive
techniques have been suggested as important tools for conservation. Today, biotechnological methods, such as artificial insemination and transplantation of embryos are well
developed and are used in programs of animal husbandry and preservation. Receiving
oocytes and embryos requires stimulation of ovaries on what some time depending on
a species of animals usually is required. These methods are not acceptable in case of
emergency, and the in vivo received oocytes in smaller quantity do not guarantee the
maximum storage of genetic material. Therefore an alternative method of preservation of
genetic material is the cryopreservation of immature oocytes in the primordial follicles
which are located in ovary cortex. The procedure of ovarian tissue cryopreservation permits conservation of hundreds of immature oocytes kept within the protective environment of the original ovarian tissue. An important advantage of this technique that the
hormonal stimulation is not required in this case. Additionally, because the primordial
follicles are small and have a simple structure, they are much more tolerant to manipulation and to the freeze-thaw procedure compared with the large growing follicles. A key
element of a good cryopreservation to cell survival is the physiochemical relationship
of heat and water transport between the intra- and extracellular environment. The art of
cryobiology involves the addition of one or more cryoprotectants which generally reduce
both the eutectic and freezing points. Therefore the purpose of this work is identification
of an optimum method of a cryopreservation of sheep‘s ovarian tissue using of various
cryoprotectors. In the present study, the cryopreservation of indigenous Chui population sheep’s ovarian tissue was conducted in vapors of liquid nitrogen at distance of 5
cm from surface within 20 minutes with use of various cryoprotectors: 1,5 M dimethyl
sulfoxide (DMSO), 1,5 M propylene glycol (PG), 1,5 M ethylene glycol (EG) and 1,5 M
glycerol (HL). The analysis of comparative histology studying shows that use 1,5 M PG
and 1,5 M DMSO has more effective effect on viability of ovarian follicles, than use 1,5
M EG and 1,5 M HL.
Key words: dimethyl sulfoxide, ethylene glycol, freezing, follicles, glycerol, ovarian
tissue, propylene glycol.