Discovery: Bone Marrow Cell Can Morph Into Liver, Lung, Gut, Skin, More
A New Rule Book
All of this is impossible, according to the current rules of biology.
The textbooks say that only an embryo has stem cells that can turn into any type of cell. Adults are only supposed to have more mature stem cells destined to become specific organs or types of tissue.
Recently, however, several different laboratories have shown that pieces of one organ -- the bone marrow -- can give rise to cells of other organ such as the brain and the liver.
But what was in the original piece of tissue? Maybe there were cells in the batch that were already destined to be another type of organ. To rule this out, scientists have to find the single adult cell capable of changing into another type of adult cell. Nobody has been able to do this -- and then Sharkis came up with an idea.
Sharkis knew that the adult stem cell everyone has been looking for has an interesting property: When placed in the body, it quickly goes back to its home in the bone marrow. So he took bone marrow from a male mouse and injected it into a female mouse whose own marrow had been destroyed by radiation.
After two days, he looked inside bone from the female mouse and found some of the cells he had injected. He then gave 30 new marrow-depleted female mice a transplant with just one of these male cells. The transplant rescued five of the animals.
The male cells divided quickly and repopulated the females' marrow. They also turned into cells that, to a greater or lesser extent, repopulated the animals' lungs, liver, skin, and digestive tract. The greatest repopulation was seen in the lung -- possibly because the cells were repairing damage caused by the original radiation.
"This is the final nail in the coffin of the idea that cells have such rigid restrictions on what they can do," Theise says. "A new paradigm is required to accommodate this data."
If these versatile stem cells exist in mice, they should exist in humans. But if we already have them, why don't they repair damaged organs?