From human IVF to IVF in horses
John CM Dumoulin, PhD
Laboratory Director, IVF-Laboratory, Maastricht University Medical Center, the Netherlands
Laboratory Director, Equine Fertility Centre, Maria Hoop, the Netherlands
The world’s first baby after In Vitro Fertilisation (IVF), Louise Brown, was born in 1978. The scientist who contributed mostly to the development of the IVF technique was Robert Edwards. At first, the safety of IVF was questioned and ethical concerns were raised. However, during the almost 4 decades that have passed after the birth of Louise Brown, IVF has turned out to be a safe and successful treatment which offers subfertile couples a last chance to have genetic children of their own. Edwards was awarded the 2010 Nobel Prize for the development of human IVF therapy. At present, more than 5 million IVF babies have been born worldwide. In developed countries, approximately 1 out of 40 children has been born after IVF.
The IVF technique was also successful applied in livestock species. In cattle, after the first live calf resulting from IVF was born in 1981, IVF on a commercial basis has grown into a mature worldwide industry resulting in an annual number of more than 400,000 in vitro produced embryos (1).
In the horse, however, development and application of modern reproduction techniques was slow. After the first two live foals were born in 1990 following standard IVF after ovum pick-up (OPU) (2), limited studies have been performed on IVF using recovered oocytes from live mares. There are several barriers to successful equine IVF. One of those are the major costs involved, both the high costs of performing the OPU, ICSI and in vitro culture of embryos as well as the maintenance of a sufficient number of recipient mares that can be used for transfer. There are also many aspects of oocyte recovery, maturation, fertilization, and embryo development in the horse that differ from those in other species (3, 4). First, success of superovulation to induce multiple ovulation is limited in mares (5). Second, the recovery rate of oocytes during the OPU is relatively low because of the close attachment of the equine oocyte to the follicle wall (3, 4). Third, after in vitro maturation, approximately only 50-80% of oocytes show signs of nuclear maturation while the percentage of oocytes that has also fully completed cytoplasmic maturity is probably lower (5). Fourth, conventional IVF remains almost unsuccessful and not repeatable to the present day. Therefore, fertilization in vitro is usually achieved using intracytoplasmic sperm injection (ICSI). And last, developmental competence of in vitro matured oocytes is relatively low: rates of blastocyst development obtained are between 25-35% at most (3, 4), while in some publications only 14% is reported (6).
At the Equine Fertility Centre, development of the IVF/ICSI treatment was started in 2009. A successful collaboration was established with the Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, resulting in the first ICSI foal in the Benelux (7). During the period of 2010 – 2013, a collaboration with the IVF-Laboratory of the Maastricht University Medical Center resulted in the establishment of the ICSI laboratory and the safe recovery of oocytes from live mares during OPU. IVF/ICSI methods used are similar to those published from the Texas A&M University group (3, 4). In 2014, OPUs and IVF/ICSI were performed on a regular basis, resulting in 17 pregnancies of which 12 are ongoing or have already resulted in the birth of live, healthy foals. These results are in the range of those published in the scientific literature (3, 4, 6).
(1) Hasler (2014) Theriogenology, 81, 152–169
(2) Palmer et al. (1991) J. Reprod. Fert. Suppl. 44-375-384.
(3) Hinrichs (2010) Mol. Reprod. & Dev. 77:651–661
(4) Hinrichs (2010) Reprod. Dom. Anim., 45 (Suppl. 2), 3–8
(5) Squires et al. (2003) Theriogenology 59, 151-170.
(6) Galli et al. (2013) Anim. Reprod., 10, 334-343
(7) Smits et al. (2010) Vlaams Diergeneeskundig Tijdschrift, 79