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Stem cell lines let scientists see how it all starts
In what could be the first step toward re-creating a disease in a Petri dish, scientists have developed a new set of stem cell lines that contain the basic genetic components of 10 incurable diseases, from Down syndrome to diabetes and Parkinson’s.
The trove of stem cell lines will allow researchers "to watch the disease progress in a dish, to watch what goes right or wrong," says Doug Melton, co-director of the Harvard Stem Cell Institute.
"In these complex genetic diseases, we’re so ignorant at the moment we don’t even know when a patient gets diabetes if they all get it the same way," Mr. Melton says. "There could be 50 different ways to get Type 1 diabetes." The stem cell lines could help researchers hone in on the root causes of disease, in other words, "where is the weak point where you could try to prevent, or treat it?"
"We have good reason to believe that this will make it possible to find new treatments, and eventually drugs, to slow or even stop the course of a number of diseases," Mr. Melton said.
"If you have 10 genes and you figure that No. 7, if you corrected it, would actually correct the disease, then you have found the Achilles heel of the disease itself," says Mick Bhatia, scientific director of the McMaster Stem Cell and Cancer Research Institute at McMaster University.
"It gives you a live cell model of the disease, so that you can actually test them. You’re not just watching them as an observer, you’re actually interacting with them," Mr. Bhatia says.
"Right now, we know how to manage diabetes — give insulin. We know how to follow it up — we look at glucose. But what causes diabetes? No one knows."
Stem cells are capable of transforming themselves into blood, bone, nerve, muscles or other materials the body needs.
Researchers took skin and bone marrow cells from patients with the diseases and turned them into stem cells with the same genetic mistakes. These "pluripotent" cells behave like embryonic stem cells, the body’s "master cells" that can morph into all types of cells and tissues, and can grow forever.
"You can culture them forever. It’s an immortalization of that patient’s disease as embodied in the cells in the Petri dish," says lead researcher and Howard Hughes Medical Institute investigator Dr. George Daley. That gives researchers large amounts of material to study.
The cells can be reprogrammed into morphing into blood, muscle or other cells.
The cell lines the researchers created carry the genes or genetic components for Parkinson’s disease; type I diabetes; Huntington’s disease; Down syndrome; two forms of muscular dystrophy; an immune disease known as "boy-in-the-bubble disease;" Shwachman-Bodian-Diamond syndrome, a congenital defect in the infection-fighting white blood cells; Gaucher disease, in which a fatty substance accumulates in the body’s organs; and Lesch-Nyhan syndrome, in which uric acid builds up in body fluids.
Together, "they represent a collection of degenerative diseases for which there are no good treatments and no good animal models for the most part," Dr. Daley says.
Mice are mice, and humans are humans, he says, and mouse models aren’t always "faithful mimics" of human sickness, especially with diseases of the blood. But whether the discovery will translate anytime soon into new treatments is a bit like reading tea leaves, the researchers say.
To make the cells, the researchers mixed bone marrow and other cells from the diseased patients with benign viruses that smuggled genes into the cells. Those genes reprogrammed the cells, so that they behaved like stem cells.
"Whether or not we’re going to be able to figure out how to do it without viruses so we can use the cells therapeutically is, as of today, an unanswered question," Dr. Daley says. "I’m confident we’re going to get there."
The researchers aren’t taking diseased cells, correcting them and then putting them back into a person. But there’s no question that’s where people are heading, says Mr. Bhatia. "We just need to get some basic understanding first."
Journal Cell, August 2008
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