Transplant hope after kidneys are grown in mice By Tim Radford Science editor   23 December 2002

Israeli stem cell research creates working organs from tiny grafts.

Israeli scientists have found a way to “grow” human kidneys from tiny grafts of tissue.  The technique so far works only in mice, but the experiment could, within a few years, offer fresh hope for the tens of thousands of people awaiting kidney transplants.

            The researchers used stem cells, those rare precursor cells that make such things as bone marrow, skin or heart tissue.

            Yair Reisner of the Weizmann Institute reports in Nature Medicine today that he and colleagues transplanted human and pig kidney stem cells from foetal tissue into laboratory mice.  Both sets of transplanted tissue grew into perfectly formed, normal-sized mice kidneys.  They accepted blood from the mice hosts, and they produced urine.

            The team calculated that, provided they timed the tissue transplants carefully, there was a lower risk of rejection by the host’s immune system.  In normal transplants, tissue types have to be matched carefully and even then there is a high risk of rejection.  Some patients spend the rest of their lives taking immunosuppressive drugs.

            Humans and other mammals start as a single fertilised egg and end as trillions of cells of 200 or more different kinds.  Stem cells are the agents that create the new, specialized tissues.  US and European scientists are racing to find ways of using them to repair damaged organs.  There have been encouraging signs that cell transplants could lead to new growth or even repair of failing tissue.  But nobody expected a tiny graft of alien tissue to turn into a fully formed organ.

            The trick seems to be in the timing.  Prof. Reisner and his team report that stem cells of a certain age – seven to eight weeks in humans – seem to be just right for making new kidneys.

            If transplanted too early, the stem cells could grow into a mix of organ tissues, such as bone, cartilage, and muscle, as well as kidney cells.  If the graft is too late, the foreign tissue will have developed a kind of identity badge that will guarantee its rejection.

            At any time, around 5,000 people in Britain are waiting for kidney transplants.  There are too few donors.  In the US, 2,000 people died this year while waiting for a match and the number of people hoping for a transplant has reached 50,000.

            Britain leads the world in research into stem cells but there has also been intense research into the use of more advanced stem cells to treat once-intractable illnesses.  Even adult stem cells seem to be able to morph into different kinds of tissue.

            One US team turned fat left over from liposuction into bone, muscle and cartilage that could be used for transplant surgery.  Two teams in New York have used bone marrow stem cells to repair heart damage in rats and mice.

            A team in Hammersmith reported two years ago that they had grown liver cells from a patient’s bone marrow.

            There are teams looking for ways to persuade damaged nerves to repair themselves, with the use of transplanted stem cells, offering new hope for people paralysed by injury, or crippled by stroke or neurodegenerative diseases.

GUARDIAN