They are called chimeras, hybrid creatures that are part animal, part human.
In 2003, Chinese scientists at the Shanghai Second Medical University were the first to successfully create human-animal chimeras when they fused rabbit eggs with human cells. The embryos were allowed to develop a few days and then they were destroyed to harvest their stem cells.
Now the borders between animal and human have been blurred even further with the creation of animals that have the body of sheep and organs that are half human. These hybrids are the result of 7 years of research at the cost of almost $10 million by Professor Esmail Zanjani of the University of Nebraska. Zanjani injected adult human cells into the fetus of a sheep. The result is a sheep with 15% human cells, 85% animal cells.
Zanjani foresees a day when the organs from chimeras can be transplanted into humans. He was already produced a sheep liver which has a significant proportion of human cells.
Future plans include using a transplant patient's own stem cells to produce their own flock of sheep. When stem cells from the bone marrow of a donor are injected into the peritoneum of a sheep's fetus, it will produce a lamb with heart, lungs, liver and brain that are partially human. Then anytime the patient needs an organ transplant, there is an exact match readily available.
According to Zanjani: "The two ounces of stem cell or bone marrow cell we get would provide enough stem cells to do about ten fetuses. So you don't just have one organ for transplant purposes, you have many available in case the first one fails."
This type of research is not without its critics. The question of whether scientists have the right to play God once again rears its head. In this particular circumstance, the issue of silent viruses comes into play. Silent viruses are harmless in animals but can be disastrous when introduced into the human body.
Dr. Patrick Dixon, international lecturer on biological trends, has sounded a loud warning: "Many silent viruses could create a biological nightmare in humans. Mutant animal viruses are a real threat, as we have seen with HIV."
There is also the fear that animal and human cells will fuse together, producing a hybrid creature with features and characteristics of a sheep and human.
Professor Zanjani disputes that possibility. "Transplanting the cells into fetal sheep at this early stage does not result in fusion at all," he said.
