Five years ago today, scientists reported that,
for the first time, they were growing do-it-all human cells. These
embryonic stem cells form shortly after fertilization and their
offspring eventually specialize into every cell in the body. Scientists
had long known that blood stem cells could form other blood cells,
but before there is a blood stem cell, there must be an embryonic
stem (ES) cell.
Christopher Reeve, paralyzed from a riding accident, favors stem cell
research as a key to regenerating spinal cord and other nervous system
tissue. James Thomson and John Gearhart are two pioneers in stem cell
research. Courtesy The
American Society for Cell Biology
And that's why the announcement, from a group
headed by developmental biologist James Thomson at the University
of Wisconsin-Madison, sparked such excitement. "There is almost
no realm in medicine that might not be touched by this innovation,"
gushed Harold Varmus, who was then running the National Institutes
In normal human development, ES cells are driven by a
genetic program to automatically change, through a multi-step process,
into the 220 human cell types. But even after 100 generations, Thomson's
ES cells remained "totipotent" -- able to make any body cell.
Much like a car-parts catalog on steroids, the offspring of ES cells include page after page of must-have items: Replacement cells? Just name the variety. Replacement tissues? Nothing more than a collection of similar cells. Replacement organs? Well, aren't they just a batch of tissues?
People with damaged cells took notice. Hoping that stem cells can be grown into neurons to repair his spinal cord, paralyzed actor Christopher Reeve, for example, just made a pitch for ES cell research.
In theory, at some point, after a lot more time and money is spent, the descendents of do-it-all cells may supplement or replace myriad diseased or dead cells:
Pancreatic cells might treat juvenile diabetes, a deadly scourge to 1 million Americans.
Replacement dopamine-producing cells in the brain might treat Parkinson's disease -- which robs half-a-million American adults of mobility.
Made-to-order heart-muscle cells might treat heart disease, the nation's
Long before ES cells treat any disease (and we are talking five years minimum), they may help researchers understand:
How genes and chemical signals control development.
The function of specific genes
The structure and function of various cell types.
Drug effects and side-effects.
Yet despite the long list of possible benefits, ES research quickly fell under a cloud. Human embryos die when the stem cells are removed, so if you think life begins at conception, this research amounts to murder.
Thus even though the embryos are left over by fertility-clinic clients, there was pressure to restrict or ban the research. (It didn't help that Thomson's 1998 report (see "Embryonic Stem Cell Lines Derived..." in the bibliography) appeared less than two years after a truly bizarre bit of scientific news: the cloning of Dolly the sheep.
In August, 2001, almost three years after Thomson's discovery, Pres. George W. Bush announced that the federal government would fund ES cell research -- but only on 60 or 70 existing lines of cells. These so-called "presidential stem cells," were deemed ethically acceptable because they would not require the destruction of more embryos.
If you wanted to work on other lineages, you could find
your own money, or move to a country with less government
regulation. (Speaking of which, Singapore is making a push to become
a center of ES cell research, and many stem cell researchers we
tried to reach were in Singapore for a meeting.)
Microscopic view of colonies (rounded, dense
masses of cells) of human embryonic stem cells in biologist James
Thomson's research lab. The skinny cells are fibroblasts that help
keep the ES cells in a primitive state. Copyright
It seemed like a good compromise, but for a couple of "buts." First, more than two years later, nowhere near the 60-plus cell lines mentioned by Bush are available. Most estimates we saw were closer to one dozen.
Second, those cell lines were experimental, created to explore the culture of embryonic stem cells rather than treat disease. Because the cells were grown in contact with mouse cells, they could be a conduit for new infections. "Human therapy could be done on the existing cell lines," says Thomson, "but if I were a patient, I'd prefer it to be based on better lines." Any medical use, he stresses, is at least five years away. Beyond the infection problem, more must be learned about controlling differentiation and preventing runaway growth -- cancer.
Nonetheless, embryonic stem cell research is exploding. Globally, about 200 labs are working with the do-it-all cells. The Bush compromise, Thomson says, "is probably slowing the research [in the United States], but it could have been stopped altogether."
How close are embryonic stem cells to meeting those Texas-sized hopes?