Using technology developed for experiments on the International Space Station, British scientists have managed to grow human embryonic stem cells from umbilical cord blood, and turn them into human liver tissue.
This could be the first step towards a worldwide "library" of stem cells that could provide more than a million different tissue types. Such a collection, based on stem cells taken at birth and preserved for decades, would have the capacity to turn into most of the 200 to 300 types of tissue in an adult human. These could one day be used to treat liver disease, diabetes, strokes and heart conditions.
Researchers in Britain have begun experiments with embryo stem cells, which have even greater potential. But this research is contentious, even in Britain, which legally cleared the way for such attempts in 2001. Other teams have tested the promise of adult stem cells, found in bone marrow and blood.
"We have found a unique group of cells that brings together the essential qualities of both types of stem cells for the first time," said Colin McGuckin of Kingston University. He and colleagues report in Cell Proliferation today that they screened umbilical cord blood to get stem cells with the characteristics of an embryo.
The dream is that stem cells could one day be used to grow new organ tissue or nerve cells and treat diseases for which there is currently no treatment.
But stem cells are extremely rare. To serve any useful medical purpose, they must exist in quantity. The challenge is to find a small number and then culture them, while stopping them from differentiating into a range of unwanted tissue.
The British team worked with a Texan group to harness a technology, derived from Nasa research, to multiply the stem cells and then "grow" liver cells. A bioreactor, designed by one of Nasa's spin-off companies, was used to simulate the weightlessness of space, and amplify the original stem cells 168-fold.
"Acquiring stem cells from embryos also has major limitations because it is difficult to obtain enough cells to transplant, as well as getting the right tissue type for the patient," Dr McGuckin said. "Using cord blood gets over that obstacle because we can produce more stem cells, and, with a global birth rate of 100 million babies a year, there is a better chance of getting the right tissue type for the many patients out there waiting for stem cell therapy."
In Britain, the US and Europe, agencies have begun to collect and preserve umbilical cord blood samples at birth. It could be a decade before the first clinical trials could help treat diseases.
The Kingston team has begun to grow liver tissue in lumps of three dimensions, using a bioreactor that mimics the freefall of a spacecraft.
"You keep the stem cells in a state of freefall and they never really get to know where they are, they never really get to know which way is down, which way is up. You can grow the cells inside three-dimensional scaffolds into larger and larger amounts of tissue."
