The demonstration that the technique, which was pioneered on mouse cells, also works on human skin cells raises the prospect of new treatments for incurable illnesses, from Parkinson’s to heart disease, based on regenerating diseased organs in situ from a patient’s own stem cells.
Although there is no intention to create human embryos from skin cells, scientists believe that it could, theoretically, be possible to do so given that entire mouse embryos have already been effectively created from the re-engineered blood cells of laboratory mice.
Creating the mouse embryos was the final proof the scientists needed to demonstrate that the stem cells were “pluripotent”, and so capable of developing into any specialised tissue of an adult animal, including the “germ cells” that make sperm and eggs.
Pluripotent stem cells could usher in a new age of medicine based on regenerating diseased organs or tissues with injections of tissue material engineered from a patient’s own skin or blood, which would pose few problems in terms of tissue rejection.
However, the technique also has the potential to be misused for cloning babies, although stem cell scientists believe there are formidable technical, legal and ethical obstacles that would make this effectively impossible.
A team of Japanese and American scientists converted human skin cells into stem cells using the same simple approach that had astonished scientists around the world last month when they announced that they had converted blood cells of mice into stem cells by bathing them in a weak solution of citric acid for 30 minutes.
The scientist who instigated the research programme more than a decade ago said that he now has overwhelming evidence that the same technique can be used to create embryonic-like stem cells from human skin cells.
Charles Vacanti, a tissue engineer at Brigham and Women’s Hospital in Boston, Massachusetts, said that the same team of researchers has generated stem cells from human dermal fibroblasts – skin cells – which came from a commercial source of human tissues sold for research purposes.
“The process was very similar to the one we used on mouse cells, but we used human dermal fibroblasts that we purchased commercially,” Dr Vacanti said. “I can confirm that stem cells were made when we treated these human cells. They do the same thing [as the mouse cells].
“They revert back to stem cells, and we believe the stem cells are not a contamination in the sample that we were inadvertently sent by the company, but that they are being made, although we still have to do the final tests to prove this,” he added.
“We have strong evidence that we have now made human stem cells by the same technique used on mouse cells and it suggests that there is probably a parallel process going on. I’m 98 per cent comfortable with the results so far.”
Detailed genetic tests and further experiments will be needed to prove beyond any doubt that the cells are true stem cells, although Dr Vacanti emphasised that he will not be carrying out the same experiments on the human stem cells that led to the creation of mouse embryos from mouse stem cells.
“My interest is to demonstrate the biological process, to grow your own perfect embryonic stem cells in order to repair your own damaged tissues – but without making an embryo,” Dr Vacanti said.
“In order to repair tissues you need embryonic stem cells, but the irony is that in order to show that you don’t need an embryo you have to sometimes create an embryo – in mice at least.”
Asked whether it would be possible in theory to follow on from the mouse research to show that skin cells could be turned into viable human embryos – effectively a clone of the donor of the skin samples – Dr Vacanti said: “This is an offshoot, an unintended consequence, so the answer is ‘yes’ …. This would be the natural conclusion, but I won’t be the one that does it.”
Robert Lanza, a stem cell expert at Advanced Cell Technology in Massachusetts, said that if the technique has been made to work on human cells as Dr Vacanti has described, then it could be a “paradigm changer” in terms of using stem cells for therapeutic purposes.
However, the development also raises serious questions about its possible unauthorised use for cloning babies,
“Because of the ease of the methodology, this research could have serious ethical ramifications,” Dr Lanza said. “If the cells are truly totipotent [able to develop into any cell type], then this technology could be used to clone organisms… and perhaps even humans.”
Haruko Obokata has stunned the world Of mice and men
Haruko Obokata, a young post-doctoral researcher now at the Riken Centre for Developmental Biology in Kobe, Japan, startled the world two weeks ago when she explained how she created embryonic stem cells from the blood of mice by simply bathing the murine blood cells in a weak solution of citric acid for half an hour.
Dr Obokata began the research in 2008 in the United States after being recruited to work in the laboratory of Charles Vacanti, a colourful and engaging scientist at the Brigham and Women’s Hospital in Boston, who first had the idea of creating stem cells from blood or skin cells by subjecting them to some kind of traumatic stress.
Dr Vacanti, along with his pathologist brother Martin, had previously published studies indicating that stem cells are spontaneously created when ordinary tissue is stressed by either mechanical injury or by rising acidity.
He believed this was the body’s natural repair mechanism, when damaged adult cells revert to an embryonic state which we call “stem cells”. His initial studies, published more than 10 years ago, were met with ridicule. On one occasion, Dr Vacanti was heckled at a scientific conference. “People said we were nuts. They said it was heresy, that we should withdraw our scientific papers,” Dr Vacanti said.
However, Dr Obokata’s painstaking research, now published in the journal Nature after unusually severe scrutiny by peer reviewers, appears to have proved Dr Vacanti right. Making embryonic stem cells from human skin or blood could not be any easier.