It has been considered unethical to breed humans to be sources for organ transplants. A controversial alternative has been achieved instead: a chimera that has a sheep's body but organs which are said to be half-human.
Though the sheep have 85 percent animal cells and 15 percent human cells, it is not a forgone conclusion that any one such sheep could provide an organ that would transplant without problems. Thus it has been conceived that a flock of sheep could be raised in order to have enough organs at a particular patient's disposal.
It has taken Esmail Zanjani, Chair of the Department of Animal Biotechnology at the University of Nevada School of Medicine, seven years to hone the technique, in which the cells of an adult human are injected into the peritoneum of the fetus of a sheep. He has even made a sheep liver with human cells in large proportion. The eventual aim of his work is to create a match between sheep and patient, with the stem cells of the latter utilized in the creation of the necessary flock. Two ounces of stem cells taken from one human patient's bone marrow would provide enough material for use with approximately ten animal fetuses, allowing multiple transplant attempts per flock (which would be harder on the many sheep than on the one human).
As of 2005 he could boast of having crafted sheep that had human cells in their pancreas, liver and heart.
Scientists from both Newcastle's North East Stem Cell Institute and London's King's College have made applications to the Human Fertilisation and Embryology Authority (HFEA — which regulates in vitro work) for permission to commence chimera work.
Animal rights activists are leery of potential cellular fusion, which might create a hybrid of man and sheep. Zanjani said that his process would not cause this.
There are other hazards as well. One commentator, Dr. Patrick Dixon, spoke of the danger that silent viruses from animals could cause "a biological nightmare in humans."
Over the years, many have questioned how far scientific experiment should precede along the lines of mixing humans and animals. In 2005, Jeremy Rifkin, author of The Biotech Century, wondered (as quoted by CBS News) that if this is permitted, "what will we ever say no to?"
The television program Animal Farm reported the work on Britain's Channel 4 in late March 2007.
— Douglas Chapman
Daily Mail — The Mail on Sunday, http://www.mailonsunday.co.uk/pages/live/articles/news/news.html?in_article_id=444436&in_page_id=1770&in_a_source, 3/27/07
Esmail D. Zanjani, Ph.D., CMB — People, http://www.unr.edu/cmbprog/ezanjani-new.htm
CBS News, http://www.cbsnews.com/stories/2005/02/24/eveningnews/main676424.shtml, 2/24/05
Human Fertilisation and Embryology Authority — Wikipedia, the free encyclopedia, http://en.wikipedia.org/wiki/HFEA