Researchers produce first African lion in-vitro embryos after vitrification of juvenile oocytes

Overview

• Post By : Kumar Jeetendra


• Source: Research Association Berlin eV (FVB)


• Date: 18 Jan,2021

A team of scientists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in Germany, Givskud Zoo – Zootopia in Denmark and the University of Milan in Italy succeeded in producing the very first African lion in-vitro embryos after the vitrification of immature oocytes. For this specific method of cryopreservation, oocytes are collected right after an animal is castrated or dead and immediately frozen at -196°C in liquid nitrogen.

This technique allows the storage of oocytes of precious animals for an unlimited time, so that they can be used to produce offspring with the help of assisted reproduction techniques. The purpose is to further enhance and apply these methods to save highly endangered species like the Asiatic lion from extinction. The current research on African lions as a model species is an important step in this direction.

We could demonstrate a high proportion of surviving and matured oocytes in the group of vitrified oocytes. Almost 50 % of them had matured, a proportion similar to that in the control group.”

Jennifer Zahmel, Scientist, Department of Reproduction Biology, Leibniz Institute for Zoo and Wildlife Researc

Lion oocytes are presumed to be quite sensitive to chilling because of their high lipid content, leading to poor revival following slow cooling. Vitrification can circumvent this problem, as the cells are frozen in ultra-fast speeds in solutions with a very significant concentration of cryoprotective agents. This technique prevents the formation of ice crystals in the cells, which might destroy them, and permits them to remain intact for an infinite time to permit their use later on.

For the present research, the scientists gathered oocytes from four African lionesses from Givskud Zoo – Zootopia after the animals had been euthanized with the goal of population management. Half of the oocytes (60) were vitrified instantly. Following six days of storage in liquid nitrogen, the vitrified oocytes were thawed and exposed toin-vitromaturation in an incubator at 39°C for a total of 32-34 hours. The other half (59) were used as control group and directly exposed toin-vitromaturation without a step of vitrification.

“To our knowledge, this is the first time thatin-vitroembryos were produced after vitrification of oocytes from African lion or some other wild cat species,” says Martina Colombo from the University of Milan and guest scientist in the Leibniz-IZW.

In a recent scientific research on the domestic cat, conducted in collaboration with colleagues from the University of Milan and the University of Veterinary Medicine Vienna, the reproduction biology group of the Leibniz-IZW demonstrated an immediate on-site vitrification of felid oocytes is the best choice to obtain a large number of good quality gametes and consequently a higher number of developing embryos.

This study was also published in Cryobiology. On-site vitrification is particularly helpful if samples are collected from wildlife kept in zoos and need to be transported to a suitable lab. “Transport of new oocytes and ovarian tissue across international boundaries is often intricate and critical concerning time, whereas onsite vitrification of oocytes enables a safe time period for transport. The oocytes can be fertilized at a later point, once they have been transported to a suitable laboratory and sperm of a man is available,” Zahmel describes.

Clarifying the pathways that are affected by vitrification would be important to get a better comprehension of the particular needs vitrified oocytes may have after thawing. “Though embryo growth was still impaired, our results give hope that felid oocytes can be cryopreserved and stored in biobanks in future,” says Katarina Jewgenow, Head of the Department Reproduction Biology at the Leibniz-IZW. “Our intent is to further improve these methods in model species like domestic cats and African lions in order to use them one day for the assisted breeding of endangered felids like the Asiatic lion,” Jewgenow adds.