KIDNEYS successfully transplanted from pigs into monkeys have brought the
prospect of transplanting a pig organ into a human a stage closer. 杏吧原创s
from Imutran, a Cambridge-based company, reported in Barcelona this week at an
international conference on transplants that all seven monkeys in the trial
survived鈥攐ne for as long as seven weeks鈥攁fter receiving kidneys from
genetically engineered pigs.
Imutran rates the experiments a success because none of the kidneys was
rejected within minutes of transplant. The company鈥檚 researchers have
genetically engineered a herd of pigs so that their organs would not be
recognised as foreign when transplanted into primates. Normally, these
鈥渪enotransplants鈥� are destroyed within minutes by a part of the immune system
called complement, which turns the organ into a sticky black mess.
Organs from the genetically engineered pigs contain genes that produce a
human protein called decay accelerating factor. This protein occurs on human
organs and instructs complement not to attack. In effect, the protein hides the
genetically engineered pig organs from primate complement (This Week, 9 March, p
4).
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But Imutran鈥檚 kidney experiments were not without problems. The four monkeys
that lived the longest all eventually had to be put down because of progressive
anaemia. Another monkey died as a result of a kidney blockage, while two others
died at eight days from acute vascular rejection, a form of rejection kept at
bay in human-to-human transplants with drugs that suppress the patient鈥檚 immune
system.
鈥淭he four cases of anaemia in the monkeys were nothing to do with the
transferred human gene,鈥� says a company spokeswoman. Imutran blames the anaemia
on the inability of erythropoietin, a protein produced by the transplanted pig
kidney, to stimulate the growth of red blood cells in the monkey bone
marrow.
Imutran, which earlier this year was taken over by the Swiss multinational
Sandoz, hopes to perform the first pig-to-human transplant within the next 12
months. Sandoz supplies virtually all the world鈥檚 cyclosporin, the main
immunosuppressive drug given to transplant patients.
