Human-Sheep Hybrids

Hi Readers,

I read an article today about a new breakthrough in which human-sheep hybrids have been created for the first time. This is an exciting development as it could be a potential cure for type 1 diabetes – a great example of how veterinary and medicine can work together.

This was a project done at Stanford university where scientists transplanted human stem cells into preimplantation embryos of sheep. The next step is to implant human stem cells into sheep embryos which have been genetically modified so they cannot grow a pancreas, in the hope that human DNA will fill in the missing code.

“We have already generated a mouse pancreas in rats and then transplanted those in to diabetic mouse and were able to show almost a complete cure without any immunosuppressants,” Dr Hiro Nakuachi, who is leading the research, said. He believes that organs grown in animals will be available for transplant within the next five to ten years.

These embryos were allowed to grow for a week before being implanted into a surrogate sheep. Current rules ban labs from allowing the survival of hybrids beyond 21 days, so the surrogate animal was slaughtered after three weeks.

This is the part of the article that caught my attention the most. There will always be ethical implications for example, if the human cells were to spread further than intended, these experiments to grow organs inside the animals could be impossible to approve for ethical reasons. However, I also thought this part of the experiment could be classed as unethical as well – if the sheep was healthy, should it really have been PTS? Of course, the rules must be followed and therefore does this make it ethical, after all it is to advance medical research?

I weighed up the pros and cons of this research:

Pros Cons
6,500 in the UK are on an organ transplant list, and it can take up to five years to reach the top. This research could help with the organ shortage crisis. The article reads “the first stage towards growing an unlimited supply of human organs for transplants and even providing a cure for Type 1 diabetes.” Whilst a cure for Type 1 is important, the wording ‘growing an unlimited supply’ implies we may starting ‘farming’ organs – is this ethical?
Scientists previously hoped pig/sheep organs could be used directly because they are roughly the same size as a human. However they were always rejected. This research gets round the rejection problem because it uses stem cells directly from a human patient. Robin Lovell-Badge (a British scientist most famous for his discovery, along with Peter Goodfellow, of the SRY gene on the Y-chromosome that is the determinant of sex in mammals. He is currently a Group Leader and Head of the Division of Stem Cell Biology and Developmental Genetics at the Francis Crick Institute in Central London) warned the organs may still be rejected by the body. “Even if they succeed in replacing all pancreatic cell types in the sheep with human cells, the blood vessels within the pancreas will be sheep derived,” he warned. “The organs could not be used for transplants into humans without triggering the immune system to reject them – and this would probably be a very fast rejection.”
Using sheep prove much more effective than pigs which have previously been used in similar experiments. Transplanting around 40 to 50 embryos into pig surrogates only leads to up to 14 piglets, while transferring three to four sheep embryos brings yields of up to three foetuses. Should we be slaughtering healthy animals because they carry embryos we have placed inside them? Can we justify this with just ‘for medical advancements’?

I am interested to see the results of this research and to read veterinary opinions on the topic in a few days time.



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