National Geographic News
It might be possible to transplant embryonic stem cells from pigs into humans to grow new organs, a new study shows.
The idea is not new. For more than two decades, scientists have pointed to the potential of embryonic pig tissues as a source for organ transplantation.
Studies in the past, however, have had little success when tissue has been taken relatively late in a pig embryo's development.
The new study shows that, for the transplantation to be successful, the stem cells need to come from specific stages of an embryo's development.
"By implantation of pig embryonic tissues into immune-deficient mice, we have now determined for the first time distinct gestational time windows for the growth of transplanted pig embryonic liver, pancreas, and lung precursor tissue into functioning tissue," said Yair Reisner, a professor in the department of immunology at the Weizmann Institute of Science in Rehovot, Israel.
Using pig tissue to replace failing human organs could help patients with diseases such as diabetes, Parkinson's, and liver failure.
Reisner directed the study, which is reported this week in the U.S. research journal Proceedings of the National Academy of Sciences.
Researchers say the supply of human organs will always be insufficient to satisfy demands, making xenotransplantationthe act of transplanting organs or tissue between two speciesan attractive alternative.
The thought of combining parts from different species goes back to ancient Greece. And as early as 1682 a Russian physician is said to have repaired the skull of a wounded nobleman using bone from a dog. Today faulty human heart valves are routinely replaced with ones taken from cows and pigs.
The major obstacle for xenotransplantation is the immune barrier. The primary cause of organ transplant failure is rejection of the graft organ by the host. In xenotransplantation, the molecular incompatibility between host and donor tissue is greater than it is in human-to-human transplantation.
Embryonic tissues, however, are less likely to provoke an immune response. Still, researchers have not figured out the optimal time to harvest the stem cells in an embryo's development.
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