Biochemical
and Biotechnology -
Xenotransplantation
Introduction
Tragic shortage of donor organs has
compelled the researchers to explore their alternatives.
Among the several ways of approaching the alternatives
are the development of artificial organs and the growth
of replacement organs from human stem cells. But there
is another possibility that is the use of organs from
other species, viz. Xenotransplantation. Although the
concept of trans-species organ transplants seems bizarre,
the pace of developments may soon call for its practical
implementation.
Surprisingly the pig, rather than other primates, is
the best candidate for cross-species transplantation.
That is because its organs are around the same size
as those of humans. The major obstacle is not what the
pig can offer, but what the human body is willing to
accept. In the transplants from human donors, rejection
by the recipient's immune system is the greatest obstacle.
In the case of pigs, the substance that triggers the
biggest response by the human immune system is a sugar
named alpha-1-galactose, found on the surface of pig
cells. Human body does not have this sugar and so its
immune system treats it as a foreign antigen and mounts
an immune response. The resulting attack by antibodies
leads to the formation of blood clots that destroy the
function of the transplanted organ.
Recent advances in cloning and genetic manipulation
have made it possible to engineer pigs that lack this
sugar, and their organs may be suitable for xenotransplantation
without the fear of acute rejection. The British company
PPL Therapeutic (linked with Roslin Institute) that
cloned the sheep Dolly, and an American-South Korean
group (linked with Novartis) have reported success with
this strategy. Both announced the creation of piglets
that lack the gene for the enzyme responsible for attaching
the sugar cells. It is a major step forward in the development
of xenotransplantation as a practical form or organ
replacement therapy.
Japanese institute experimenting with pigs for xenotransplantation
has been pursuing a different strategy to overcome the
acute rejection response. The Animal Engineering Research
Institute, Tsukuba, has created lots of cloned pigs
that express certain human genes. But, now the strategy
of using gene knock-out and cloning techniques to create
useful animals for xenotransplantation has been validated
and apparently this is going to be the process for the
supply of organs for xenotransplantation, a field whose
world market is expected to grow to $ 5 billion.
Contact for more information
Science & Technology
Wing Embassy of India
2-2-11, Kudan Minami, Chiyoda-ku
Tokyo 102-0074, Japan
Tel: +81-3-3262-2391 to 97,
Fax: +81-3-3234-4866
E-mail:tandonus@hotmail.com
