An alternative way to make stem cells could open a window on human disease.
Alonzo
Scientists have been talking about the medical promise of stem cells
for more than a decade, even before human embryonic stem cells were
successfully isolated in 1998. Most of the public attention has
focused on their regenerative power: since stem cells can renew
themselves and differentiate into specialized cell types, they could
potentially be used to build replacement organs, heal spinal-cord
injuries, or repair damaged brain tissue. But the research world has
also pursued another, even broader-reaching goal: using the cells of
patients with various illnesses to derive pluripotent stem cells,
which can give rise not just to the specialized cells in a particular
organ or tissue but to virtually any cell type. Those cells could be
used to create laboratory models of disease. For example, a cell from
a Parkinson's patient could be turned into a neuron, which would
exhibit the progressive molecular changes at work in the
neurodegenerative disorder. This type of tool could capture the
details of human disease with unprecedented accuracy, and it could
revolutionize the way researchers search for new treatments.
Studying human disease in the lab is an enormously challenging task.
It's difficult to obtain brain tissue from a living Alzheimer's
patient, for example, and impossible to study how that tissue changes
as the disease progresses. Animal models can offer only rough
approximations of a human illness, capturing at best a few of its
symptoms or causes. But iPS cells could yield a much more
comprehensive picture. Because each cell line comes from a human
patient, the cells reflect the complex array of factors that led to
the patient's disease: the genetic mutations, the effects of
environmental history. And because those cells can be prodded to
develop into a variety of tissue types, scientists can watch the
disease unfold in a petri dish. They can observe, for example, the
subtle molecular changes that take place in the neurons of a patient
with Alzheimer's long before the telltale signs of the disease, such
as amyloid plaques, can be seen in the brain. It's the difference
between trying to piece together the details of a plane crash from
photos of the wreckage and watching a video of the crash from every
angle, with the ability to stop, zoom in, and rewind at will.