Comparison of Different Materials for Self-Pressurized Vitrification of Feline Oocytes-First Results.

Abstract

Simple SummaryIn endangered species, the remaining individuals live in small isolated groups. Cryobanking of gametes represents the possibility of saving genetic variability, and increasing diversity by being the bridge between populations. Therefore, it is an urgent need to provide reliable methods in order to preserve these valuable resources under well-established conditions. Self-pressurized freezing is a successful technique that can be performed in remote areas without special equipment, which is a requirement to rescue material from wild specimens. In this study, we aim to check the efficacy of this method to vitrify felid oocytes and to find a suitable material for this procedure. One hundred and eighty nine oocytes from domestic cat were frozen in three different material tubes: Aluminium, silver, and titanium. Aluminium presented toxic effects that were corroborated by the moderately lower cleavage rates (14.3%), followed by silver (18.2%). Furthermore, in the literature, silver has been related to biological alterations in the cells. A minor tendency for higher rates, in both maturation after warming of the oocytes (55.6%) and cleavage after fertilisation (20%), were obtained with titanium, nevertheless there was no statistical difference between the outcome. More studies are needed to improve the method and increase embryo development after warming.Cryobanking is a crucial part on species conservation. Nowadays, there is no suitable protocol for vitrification of feline oocytes. Self-pressurized rapid freezing of different cell types proved to mimic the advantages of high pressure freezing. As this method could also be applied for gamete rescue under field conditions, the aim here was to analyse the impact of self-pressurized vitrification on feline cumulus-oocyte-complexes (COCs) and to determine the appropriate material. Therefore, COCs of domestic cat were randomly vitrified (n = 189) in metal tubes of different materials: Aluminium, silver, and titanium. No significant differences were found on oocytes’ competence after thawing. On average, 44% of the COCs presented normal morphology and 48.2% of them showed a polar body after in vitro maturation (IVM) and were subsequently fertilised. Aluminium tubes were positive on toxicity tests, producing the lowest cleavage rates. Silver tubes showed no toxic effect, but the cleavage rate was lower than with titanium tubes, and a previous association with embryotoxicity and biological alterations makes us aware of its indiscriminate use. Titanium seems to be the only inert material of them, presenting a slightly higher maturation (55.6%) and cleavage (20%) rates. Nevertheless, more studies should follow to increase embryo competence after warming.