Scientists have successfully used rats as hosts to grow new pancreases for mice, a procedure that may have enormous implications for the future of human organ transplant capability. Researchers took stem cells from mice and put them into rats where a new pancreas was generated. The new organ was then transplanted from the rats back into mice. The hybrid pancreas organ then began to produce insulin in the mice, effectively curing them of diabetes.
The research was carried out at the Stanford University School of Medicine in California. Leading the effort was stem cell biologist Hiromitsu Nakauchi who published the results in the Jan. 26 issue of Nature.
The success of the rat-to-mice organ generation method suggests that the same procedure might eventually be developed for human subjects. That would require transplanting human stem cells into another species large enough to grow human-sized organs. Rats and mice are simply not large enough for human interaction, and are incompatible in other biological ways. One of the host animals most often suggested is a pig.
Use of pigs in conjunction with human medical applications actually has a long history. For example, pig valves are still commonly used today in heart transplants. Artificial insulin for diabetics was for years generated in pigs. The process has since been replaced by recombinant DNA technology, but pig or bovine-based insulin was once the only source.
Still another human-use product derived from pigs are tissues that are processed for wound closure applications. The fact is, using pig tissues to treat human subjects is well-established territory in medicine.
Ethical Medicine or Frankenstein Monsters
The rapidly developing science of inter-species growth of organs, hormones, various tissues and other products remains an area fraught with thorny ethical questions. From a common-sense point of view, many people feel that growing a body part in one animal for use in an entirely different species seems a fundamental violation of what Mother Nature intended. For many, on the other hand, it’s a deeply religious issue.
But there are also many legitimate concerns from a strictly scientific point of view. There are worries that interchanging biological components between species opens the door to dangerous contamination between human and animal species. For example, some fear that deeply embedded viruses or genetic diseases that can infect only pigs may somehow find itself into the human biology pool, potentially creating a catastrophic disease that could spread across the globe.
Another major ethical sticking point relates to the process in which mice pancreases were created with rat stem cells. Such stem cells are called pluripotent cells. To create a human organ using a pig, for example, researchers would have to inject large numbers of pluripotent cells into the animal. This theoretically could result in the generation of a large proportion of human cells throughout the animal body — but that might include brain cells — or the cells that lead to the development of human sperm and ovum.
Avoiding The Dangers
One does not have to be a professional medical biologist to understand the frightening implications of accidentally growing human brain cells or reproductive cells in animals – but those involved in such research today insist that extremely rigorous protocols are in place to prevent such a situation from ever arising.
Proponents of using human stem cells to grow hybrid organs in animals point to the dire shortage of human organs needed for life-saving transplants today. There are currently 121,678 people waiting for organ transplants in the U.S. Of these, 100,791 are kidney transplants. The average wait time for a kidney is 3.6 years, and 13 people die every day waiting for a donor.
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