Human-sheep hybrids have been created for the first time by scientists at Stanford University (see New advances and challenges in the production of human-animal chimeras). The scientists grew the embryos in a surrogate sheep, allowing them to gestate up to 3 weeks (see HERE ).

These experiments pave the way for the creation of farms of quasi-human hybrid animals, which can be used for transplants and, in this specific case, to treat Type 1 diabetes. The next step proposed is to implant human cells into genetically modified sheep embryos so that these can develop a pancreas with human DNA.

The team is now trying to obtain the necessary licenses that will allow them to extend the life of the chimeras to 70 days. In relation thereto, lead researcher of the group, Dr Hiro Nakuachi, believes that organs grown in animals will be available for use in transplantation within the next five or ten years. To support his statement, Nakuachi says that they have already generated a mouse pancreas in rats which, when transplanted into diabetic mice, completely cured their diabetes, without requiring immunosuppressant treatment.

Differences between human-pig and human-sheep experimentations

Similar experiments were conducted last year at the Salk Institute in California by the group led by Juan Carlos Izpisua, creating human-pig hybrids (read our special report HERE), although it seems that they have not yet obtained results that can be transferred to human medicine.

Human-animal hybrid utility and ethical aspects

In the organs developed, one in every 100,000 cells was human, but in the new study, they managed to create organs where one in every 10,000 cells was human. Organs grown in pigs and sheep could be used in humans because they are very similar in size.

However, in order for the experiments in pigs to be more successful, the efficiency needs to be improved, because transferring 40 or 50 embryos into surrogate sows obtained only 14 piglets, while transferring 3 or 4 embryos into surrogate ewes obtained 3 fetuses.

Another difficult problem that remains to be resolved, according to some experts, is to prevent rejection of the transplanted organs.

These are undoubtedly very promising experiments which, although they still offer ethical problems (as we said about Ispizua experimentation, HERE), if resolved could — if these are resolved — help to alleviate the shortage of organs for transplantation in human medicine.

Photo Daily Express