Xenotransplantation still out of reach

January 3, 2006

Xenotransplantation, the transplantation of tissue and organs between different species, has been a hot potato in the scientific community ever since 1902 when the Viennese surgeon H. Ullman transplanted a pig kidney to a human arm. The transplantation failed, and so have all the others ever since. In 1966-1993, eleven liver transplantations from apes and one from a pig were performed on humans who all died within a couple of months.

"As my teachers put it: xenotransplantation has been around the corner for 30 years and still is," says Professor Krister Höckerstedt, head of Transplantation and Liver Surgery at the Helsinki University Central Hospital.

The problems with xenotransplantation include rejection of animal tissue by the human immune system, dangerous viruses possibly transferred with the transplant and ethical issues. Apes and pigs have turned out to be the most suitable donors for humans, although pig protein differs from that of humans. In pig blood, there is a sugar molecule against which there are antibodies in human blood. These antibodies produce protein that destroys the transplanted organ in a matter of minutes.

"Even when two species are closely related, there are tens of thousands of tiny differences between them. It makes xenotransplantation rather challenging," Höckerstedt says.

Xenotransplantation research is very active, however, and some progress has been made. Rejection can be partly prevented with the genetic manipulation of pigs. Anti-rejection medication has been tested in transplantations between pigs and apes.

Future donors can be pigs or apes, but the need for transplantation keeps growing. In 2004, a record number of 276 transplantations were performed in Finland. There are 300 patients alone waiting for a new kidney.

Every year some 20 to 30 people die waiting for a transplant. Instead of animal organs, we really need to find other ways to solve the problem.

"My solution would be to increase the use of transplants from brain dead people," Höckerstedt says.

Text: Kai Maksimainen

Photo: Veikko Somerpuro

www.helsinki.fi/digitalcommunications

Translation: Valtasana Oy

Copyright © 2003-2005 University of Helsinki.

This article posted January 28, 2006.