McGill team harvests stem cells from skin
Research offers hope that scientists can find sources other than embryos
CAROLYN ABRAHAM, MEDICAL REPORTER
Saturday, August 18, 2001
Researchers in Montreal have for the first time captured stem cells from the skin of adult mice and humans capable of growing into brain cells and a range of other tissues.
The feat offers new hope for treating neurological disorders, and comfort to U.S. President George W. Bush. Last week he set strict limits on publicly funded American research using stem cells derived from human embryos, which are destroyed when the powerful cells are extracted.
The Canadian research, published today in Nature Cell Biology, bolsters the view that scientists can find alternative -- and less controversial -- sources of stem cells, which have the unique power to divide indefinitely before growing into the various tissues and parts that constitute any living being.
The stem cells harvested at McGill University's Montreal Neurological Institute have grown into smooth muscle cells, fat cells and brain cells -- including neurons, the individual thinking units of the human mind.
"They are beautiful neurons," said molecular biologist and co-author Freda Miller. "You kind of look at them and say, this can't be true. But then you go back and do it 10 times, and you realize it is true."
While no one yet knows if these neurons can transmit electrical and chemical signals as they do in the brain, one aspect of growing them from stem cells found in skin is that scientists could have a vast and easily accessible supply.
"It's from skin," said Dr. Miller. "There's so much, and it's right there, and this is a non-controversial source."
Ronald Worton, scientific director of the Ottawa Health Research Institute and head of Canada's Stem Cell Network, said stem cells that can produce brain cells have been found in the brain, but this is first time they have been grown from stem cells found in skin.
"Two years ago I would have said this is a big surprise and I wouldn't have believed it unless it could be widely reproduced," Dr. Worton said. "But then the dogma used to be that if you were a stem cell in [adult] bone marrow, you could only make blood cells, or if you were a stem cell in skin, you only make skin. There's now enough lab work to say the dogma was wrong."
Scientists hope to one day chemically goad stem cells into becoming replacement tissues for ailing patients, such as insulin-producing cells for diabetics, brain cells that pump out dopamine for Parkinson's sufferers, or cells rich in dystrophin for people with muscular dystrophy.
Patients receiving new tissue grown from stem cells taken from their own skin would face far fewer problems of rejection, if any, than they would after receiving a transplant of stem cells derived from human embryos.
Dr. Miller and Jean Toma, the paper's lead author, thought several years ago that because skin, like blood, regenerates itself on a rapid and regular basis, it could be a rich source of stem cells.
In particular, they wondered about cells beneath the epidermis in the skin's second layer, the dermis. That layer contains nerve cells that relay sensations such as touch and temperature to the brain. Since these cells regenerate after injuries such as burns or gashes, the Montreal group looked for the precursors of these sensory cells, hoping to find the stem cells that produce them.
They isolated them first in the nasal passages of mice. But the source was not practical, given the difficulty of extracting enough from a tiny, damp airway. Then they tested their hypothesis with skin from mice and from a human scalp.
They diced the skin samples and added enzymes to break down the cells and "to filter out the hair and other junk," Dr. Miller said. Next they placed the molecular mash in a tightly closed tissue-culturing flask, where the cells began to divide and grow along the electrically charged plastic bottom.
The stem cells separated from the rest of the cellular group, snuggling around one another like a cluster of grapes. After three weeks, the researchers tested their versatility by exposing them to various proteins, which encourage them to differentiate into a number of cell types.
Some of them grew into fat cells -- big and round and filled with translucent bubbles. Others turned into the svelte cells of smooth muscle, which lines blood vessels and intestines. Impressively, they also blossomed into a variety of precious brain cells, including neurons, with branches sprouting across their surface to send and receive neurochemical messages, and glial cells which, among other things, produce the fatty white sheaths around nerve fibres in the brain that speed signals between neurons.
This, said Dr. Miller, is especially welcome news since these fatty sheaths are worn and frayed in patients with multiple sclerosis.
Samuel Weiss, a University of Calgary cellular biologist who first showed in the early 1990s that the adult brain of mice retains stem cells, cautioned that researchers still have to prove that stem cells from adults have long-term viability.
"We still have to answer the question as to whether or not it will be an effective treatment to replace cells," he said.