In a study published in February in the Proceedings of the National Academy of Sciences, researchers at the Weizmann Institute of Science published the results of their experiments in implanting embyronic stem cells from pigs into mice.
The researchers wanted to establish at what point it was best to implant the embryonic stem cells, so it took stem cells from varying stages of development of the pig embryo, and implanted them in the liver, pancreas and lungs of immune-deficient mice.
The researchers discovered that transplanting embyronic stem cells at too early or too late a stage would not result in new cell growth, but that if transplanted during the correct window of opportunity, the pig stem cells did lead to cell growth in the mice. Dr. Bernard Herring, at the Diabetes Institute for Immunology and Transplantation at the University of Minnesota, told National Geographic News,
What he [lead researcher Yair Reisner] has shown is that there’s a window of opportunity . If you obtain this tissue at a very defined point in time, then you can see development into islets [portions of the pancreas that secrete hormones like insulin] without risks such as teratoma formation. That’s clearly something that makes us feel very strongly that this could be a real opportunity, one that can be translated into tangible benefits much faster than other technologies.
In a statement about the research, Reisner said,
Considering the ethical issues associated with human embryonic stem cells or with precursor tissue obtained from human abortions, we believe that the use of embryonic pig tissue could afford a more simple solution to the shortage of organs.
This finding helps explain, in part, why previous efforts to transplant pig embryonic stem cells failed, since previous research had harvested the cells at a much later gestational age than what Reisner’s study found was optimal.
Of course there are still a number of major hurdles to overcome before such technologies could be used in human beings even if researchers figure out how to make embryonic stem cells produce cells in human beings, including producing pigs free of viruses that could possibly infect human beings and avoiding an immune response to the transplant of such cells.
Pig Stem Cells to Be Used to Grow Human Organs? Stefan Lovgren, National Geographic News, February 15, 2005.
New Organs Could Come from Pig Embryos – Study. Reuters, February 14, 2005.