On the 12th of May 2017, a stallion named VICSI was born at the Faculty of Veterinary Medicine of Ghent University, Belgium. The foal was named after two crucial techniques that have been used to achieve this: vitrification and ICSI. Vitrification is a cryopreservation method during which oocytes are cooled very rapidly, resulting in the formation of a glass-like structure and avoiding the formation of ice crystals which can damage the oocyte. For ICSI or intracytoplasmic sperm injection, micromanipulation is used to inject a sperm cell into an oocyte. Oocytes are much more sensitive to low temperatures than embryos. Therefore, this report on oocyte vitrification means an important breakthrough in the field of assisted reproduction in the horse.
VICSI is the result of research at the department of Reproduction, Obstetrics and Herd Health, under supervision of professor Ann Van Soom. Nerea Ortiz Escribano, who makes a PhD on vitrification, collaborated with Katrien Smits, who works as a postdoctoral researcher of the FWO and who is specialized in ICSI.
The procedure from frozen oocyte to foal
The oocytes for this research were aspirated from equine ovaries collected at the slaughterhouse. These immature oocytes were vitrified and stored in liquid nitrogen for one week. After rapid warming, maturation of the oocytes was performed in the incubator. Mature oocytes were fertilized by ICSI and cultured in the incubator for 9 days. The resulting embryo was transferred to the uterus of a recipient mare on the 20th of June 2016 at the Animal Embryo Centre Diergaerderhof in the Netherlands. On the 29th of June 2016, examination by ultrasound confirmed that the mare was indeed pregnant.
Just like embryos, oocytes can now be stored too
Cryopreservation of oocytes offers several possibilities in veterinary medicine. Oocytes can be stored and transported for research or for clinical purposes. In the future it will be possible to store oocytes from a valuable mare, instead of embryos only. This provides more flexibility to the owner with respect to the choice of the stallion. Up to now, the owner had to decide immediately which stallion was going to be used for fertilization as the oocytes could not be stored.
A lot of potential, a bit of patience
Also for the conservation of genetics of rare or endangered horse breeds or equids like zebras, the freezing of immature oocytes provides a lot of opportunities. However, it requires some time to optimize a technique, which has been developed in a scientific research context, to a level allowing practical applications. In this study, which will be published in the Equine Veterinary Journal, only 34% of the vitrified oocytes matured and only 5% of the injected oocytes developed to a good embryo. Using fresh oocytes, the maturation rate is 60% and 20% of the fertilized oocytes develops into an embryo that can be transferred to a mare.
The birth of VICSI is an important step towards these practical applications. In 2009, SMICSI, the first Belgian test tube foal, was born at the faculty of Veterinary Medicine, Ghent University. At that time, ICSI was only used for research, but meanwhile the technique has also been used for clinical purposes. Oocytes of genetically valuable mares are collected at the clinic by means of ultrasound guided puncture of the ovaries (ovum pick up, OPU). As the oocytes are fertilized by ICSI, sperm with a poor quality or limited supply can be used. Subsequently, the embryos are cultured in the laboratory and transferred to a recipient mare. Several foals were born this year resulting from the combination of OPU and ICSI at the faculty of veterinary medicine.
VICSI = teamwork
The birth of VICSI is the consequence of the fruitful collaboration between veterinarians, Belgian and foreign researchers, technicians and animal caretakers within the department as well as veterinarians from embryo transfer centers in Belgium and abroad. This world scoop is the result of the long-lasting dedication of many talented individuals.
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