Statement of Harold Varmus, M.D., Director,
National Institutes of Health, Before the Senate Appropriations
Subcommittee on Labor, Health and Human Services, Education
and Related Agencies, January 26, 1999 on research applications
of stem cells.
The isolation and culturing of human pluripotent stem cells
opens certain avenues of research for the first time. Let
me mention just three potential applications of human pluripotent
stem cells. The first is research focused on how stem cells
differentiate into specific types of cells. The goal is to
identify the genetic and environmental signals that direct
the specialization of a stem cell to develop into specific
cell types. Studying normal cell and tissue development will
provide an understanding of abnormal growth and development
which, in turn, could lead to the discovery of new ways to
prevent and treat birth defects and even cancer.
A second and more practical application of research using
these cells is in pharmaceutical development. Use of human
pluripotent stem cells could allow researchers to study the
beneficial and toxic effects of candidate drugs in many different
cell types and potentially reduce the numbers of animal studies
and human clinical trials required for drug development.
The third and most obvious potential application of these
human pluripotent stem cells is to direct the specialization
of the cells into cells and tissues that could be transplanted
into patients for the purpose of repairing injury and pathological
processes. A number of such examples are described in my December
testimony, but two are worth mentioning here.
(i) Transplantation of healthy heart muscle cells could provide
new hope for patients with heart disease. The hope is to develop
heart muscle cells from human pluripotent stem cells and then
transplant them into the failing heart muscle in order to
augment the function of the heart. Preliminary work in mice
and other animals has demonstrated that healthy heart muscle
cells transplanted into the heart successfully repopulate
the heart tissue and integrate with the host cells. These
experiments show that this type of transplantation is feasible.
(ii) In many individuals with Type I diabetes, the production
of insulin in the pancreas by specialized cells called islet
beta cells is disrupted. There is evidence that transplantation
of either the entire pancreas or isolated islet cells could
mitigate the need for insulin injections. Islet cell lines
derived from human pluripotent stem cells could be used for
this critical research and, ultimately, for transplantation.
Because human pluripotent stem cells continue to replicate
robustly, stem cells derived from a few embryos or from a
few fetuses could potentially be used in hundreds of individual