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At Utrecht ľ¹Ï¸£ÀûÓ°ÊÓ, all kinds of things are happening in the field of artificial insemination of horses. For instance, there is a clinic where horses from all over Europe come for treatments and where a team of scientists work every day. They look for solutions to current problems in the artificial insemination of horses and humans. Clinician Anthony Claes and scientist Marta de Ruijter talk about their work, in which they collaborate a lot. De Ruijter says: ‘If we make a discovery in research, we immediately think about how to apply it in the clinic.’

Claes and De Ruijter’s foreign accents immediately reveal that neither of them are from the Netherlands. Claes has the cosy accent of our southern neighbours. ‘I’m indeed from Belgium’, Claes says while smiling. De Ruijter’s accent is more difficult to identify. ‘As a little girl, I lived in Milan’, she explains. ‘I already loved horses back then, but my parents were not so keen on horse riding as a hobby. Of course, that’s not easy in a big city. Fortunately, my grandfather lived outside the city, so I could start horse riding after all when I turned eight. That was inevitable because my passion for horses was so great.’ Since then, both of them have moved to the Netherlands and they work in the same team in Utrecht.

Embryos from the lab

The reasons for the artificial insemination of horses and humans are not the same. For humans, it is usually done when the normal way of getting pregnant does not succeed. For horses, the reason is often that a mare is old or participating in sports competitions. Claes says: ‘We remove egg cells from the mare, make embryos out of them in the lab and then place them in surrogate mares.’ The technique they use for that in horses is called Intracytoplasmic Sperm Injection (ICSI). That looks like the more well-known method IVF, which is often used for humans. But there is one important difference. ‘In IVF, a sperm cell in a Petri dish fertilises a ripe egg cell by itself, while we inject the sperm cell in the egg cell in ICSI.’

Successfully making foals

Claes proudly answers the question of why many international customers come to Utrecht. ‘We have a strong team. In Utrecht, we’re good at two things. For instance, we often succeed in making multiple embryos in one go.’ Claes explains that making embryos does not always succeed, but if it does - about sixty to seventy percent – the result is something to be proud of. ‘2.4 embryos on average. Occasionally, it can even go as high as ten embryos. However, with such successes, you’re not there yet. You also need to place these embryos in surrogates, and that can go wrong too. However, we also excel in that and the percentage of mares that become pregnant after the insertion of an embryo is one of the highest in the world here.’ According to Claes, we do not have to worry about the well-being of the surrogate mares. ‘We place the embryos in the surrogates in an early stage, and after birth, the foal stays with the surrogate for about six months. That’s not very different from the normal situation.’

The percentage of mares that become pregnant after the insertion of an embryo is one of the highest in the world here

Foal of a deceased mare

There is one customer Claes will never forget. ‘I’ve seen many customers over the years, each with their own stories. But I’ll never forget this mare. She suddenly died during a ride about two years ago, probably because of a ruptured blood vessel. The owner immediately called in a vet, but he could no longer save her. The owner really wanted another foal. That vet then called us with the question whether or not, if he were to extract the ovaries from the mare, we could still extract egg cells from them in Utrecht. That’s possible, but only if it’s done very quickly, preferably within six hours. It was in the weekend, so everyone had the day off. We immediately called our team. Within three hours, all the people required were at the faculty, and we extracted the egg cells from the ovaries. We succeeded in making two embryos, which we placed in surrogates. This finally resulted in one foal. The owner was very happy.’ De Ruijter continues: ‘The biological mother was a good sports horse. The bloodline can be continued this way. On top of that, the mare had a big emotional value for the owner.’

Expensive embryos

A lot of money is involved in the trade of horse embryos. Claes says: ‘If horse owners sell embryos from successful mares, then these are very expensive.’ De Ruijter adds: ‘I once thawed out an embryo for an embryo transfer, and my hands were shaking. The owner had sold the embryo for tens of thousands of euros.’ Smiling, she says: ‘That makes you feel the pressure. Fortunately, it went well.’

Embryo does not implant

The scientists in the team unravel the process of artificial insemination. More knowledge is needed so that, eventually, more mares and women can become pregnant by means of artificial insemination. ‘The problems differ between humans and horses’, De Ruijter explains. ‘In horses, the process often fails in the development from egg cells to embryos, while in humans, the difficulty lies more in the development of the embryo after it’s been reinserted into the uterus.’ In humans, only 35 percent of the reinserted embryos result in babies. In horses, that’s sixty percent. ‘In both humans and horses, this is caused by the embryo failing to implant. That’s usually due to a problem during cell division. We want to know what exactly goes wrong. Together with scientists from the European Molecular Biology Laboratory in Heidelberg, we’ve developed a new technique that allows us to make certain proteins of the embryos fluorescent. With this technique, we became the first in the world to follow the cell division and development of live embryos under the microscope.’ If De Ruijter and her colleagues can find the reason for the failed cell division, then that could result in advantages for the artificial insemination of horses and humans.

Improving fertility in humans

De Ruijter says that some scientists in human fields are keen to collaborate with them. ‘As you can imagine, research on human embryos quickly comes up against ethical boundaries. In many countries, also in the Netherlands, you can’t inseminate human egg cells for research purposes. This is why research on animals is ahead of research on humans. Therefore some researchers on humans are keen to collaborate with us. Horses and cows are good models for humans. By collaborating, we can also contribute to artificial insemination of humans.’

Just like humans, old mares become pregnant less easily and have miscarriages more often

Pregnant at an older age

Furthermore, the scientists in Utrecht also focus on the ageing of egg cells. Just like humans, old mares become pregnant less easily and have miscarriages more often. On top of that, older women’s babies have an elevated risk of Down’s syndrome. Claes says: ‘From the sixteenth year of their lives onwards, horses’ fertility decreases. From twenty years onwards, it can be really difficult to get these mares pregnant.’ De Ruijter continues: ‘Miscarriage and Down’s syndrome are caused by problems in cell division. The egg cell has to divide its chromosomes twice in order to become ripe, which often goes wrong. We’re trying to figure out why that goes  wrong.’

To customers’ foals in the weekend

Just like De Ruijter, Claes spent much time around horses as a small child. ‘No one rode horses within our family, but my uncle had horses. That’s why as a small boy, I spent all my free time at my uncle’s place.’ When we ask Claes whether or not he also spends time with horses besides his work, he laughs. Claes says: ‘I sometimes go to customers to look at their foals in the weekend or go on a walk with a horse together with my children. However, horses continue to be a real passion.’ Claes and De Ruijter no longer ride themselves. De Ruijter says: ‘It costs a lot of time and is therefore hard to combine with a busy job and a family. Fortunately, our passion for horses is interwoven with our work.’

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