Session I | Session II
Stem Cell Research
Elias A. Zerhouni, M.D.
Director, National Institutes of Health
May 22, 2003
Mr. Chairman, Senator Harkin, and Members of the Subcommittee, I am pleased to appear before you
today to testify about the progress of human embryonic stem cell research. In FY2002, NIH spent
approximately $11 million for human embryonic stem cell research to increase the availability of
stem cell lines for federal research, train scientists how to use these technically-challenging
cells, and conduct basic, pre-clinical research that represents the first steps toward
understanding how stem cells might be used to treat injuries and diseases.
More than 60 investigators at 48 institutions have received NIH awards, including 14
investigator-initiated grants and 44 administrative supplements. The administrative supplements
allow investigators to rapidly incorporate research on human embryonic stem cells into their
ongoing work. As you know, there are 78 lines fully eligible for Federal funding, in various
stages of development. NIH support has helped increase to 11 the number of human embryonic stem
cell lines that are widely available for all researchers. More lines will become available in the
future, as we help the scientific community capitalize on this opportunity. I can report to you
today that NIH's implementation of the policy set by the President on August 9, 2001 has enabled
the field of stem cell research to advance. We continue to acquire new knowledge about human
embryonic stem cells (hESCs). Some of the significant discoveries include the following research
- NIH-supported researchers at the University of Wisconsin recently succeeded in replacing a
specific stretch of DNA in human embryonic stem cells. This technique, called homologous
recombination, opens the door to scientists who want to study the function of specific genes
within these cells and also provides a way to modify hESC-derived tissues in a very precise
matter for use in treating patients.
- Scientists at NIH have been able to demonstrate that differentiated mouse embryonic stem
cells can be directed to become specialized cells in order to repair damage when transplanted
into the brain or spinal cord. This finding could lead to the development of replacement
therapy for cells that are destroyed through injury or disease, such as stroke, Parkinson's
disease or Alzheimer's disease.
- In vitro studies have produced more specialized cells from human embryonic cells that might
be used for blood cell transplantation therapies for patients with blood malignancies such as
leukemia or myeloma.
- Scientists are currently working to identify those genes that are involved in the
differentiation of hESCs, as well as those genes that permit embryonic stem cells to
self-renew. This knowledge, along with research involving gene transfer techniques,
potentially will allow scientists to coax hESCs into becoming insulin-producing beta cells to
treat insulin-dependent diabetes
- Until recently, all hESCs were grown on mouse feeder layers. Now scientists are
establishing conditions that allow hESCs to grow in the presence of human feeder cell layers.
NIH-supported scientists in the United States, using stem cells eligible for federal research,
have tested the ability of human feeder cells derived from fetal or adult tissues to support
the growth of human embryonic stem cell lines. Both fetal and adult human feeder cells were
able to support and maintain the cells in an undifferentiated state. Also, we have seen
published research on the existence of one cell line, developed in Singapore, that was created
and developed using human feeder layers. However, the Food and Drug Administration has
informed NIH that, given the complexity of this area of research, it is difficult to predict
whether newly derived human embryonic stem cells grown exclusively on human feeder cells would
result in clinical trials sooner than the existing eligible cell lines either grown exclusively
on mouse feeder cells or adapted to human feeder cells.
At the same time, we continue to learn more about other types of stem cells, including adult and
those derived from umbilical cord blood.
- An NIH-supported researcher at the University of Minnesota isolated multipotent adult
progenitor cells from human bone marrow. These cells demonstrate the potential to
differentiate beyond bone marrow stem cells into other cell types, including liver, neurons
and blood vessels.
- In a laboratory of the National Institute of Dental and Craniofacial Research, NIH
intramural scientists have recently characterized a population of stem cells found in the
dental pulp of deciduous, or "baby"teeth. These stem cells have the potential to become
cells expressing molecular markers characteristic of dentin, bone, fat and nerve cells and
may provide an accessible source of stem cells to repair damaged teeth, regenerate bone, and
treat nerve injury or disease.
- Scientists established a number of years ago that umbilical cord stem cells can repopulate
the bone marrow of a small child. Umbilical stem cells can be used today to treat certain
childhood disorders such as Fanconi's anemia. With the current technology, however, these
cord blood stem cells can only be harvested in small numbers, which limits their clinical
utility. We are seeking methods to expand these cells in the laboratory to generate very
large numbers of the cells needed for many other clinical applications.
Human embryonic stem cell research is still in its nascent stages, and there are many basic
research studies that will be required before we can begin to plan clinical trials. NIH is
supporting preliminary research to understand how to direct differentiation along specific
pathways, to establish techniques for isolating specific cell types, to control cell proliferation,
and to control interactions between the host immune system and transplanted cells that might
mediate graft rejection.
Research using hESCs offers the potential to inform us about the earliest molecular and
cellular processes that regulate normal development, and provides a tool to discover how a cell
is able to be both pluripotent and indefinitely self-renewing. In addition, research using
hESCs will help the scientific community to understand the molecular signals that specify
differentiation into specific cell types, some of which may ultimately be useful for cell-based
treatment of disorders, such as Type 1 diabetes or Parkinson's disease, that involve loss of a
specific cell type.
As we continue our work with the research community to fund new research and facilitate the
availability of additional stem cell lines, the NIH Stem Cell Task Force is continuously and
vigorously evaluating the state of the science to lead the implementation of a vigorous research
program envisioned by the President. Attaining basic knowledge about the characteristics and
potential use of stem cells remains the immediate challenge before the research community today.
Until we understand the basics, we cannot know with certainty the future research requirements
for advancing into clinical trials using embryonic stem cells. The NIH will continue to monitor
the state of the science and assimilate the body of research evidence in order to make informed,
evidence-based recommendations on this important issue.
We are working hard to promote stem cell research, based on recommendations received from the
research community by the NIH Stem Cell Task Force. The newest effort is the establishment of the
NIH Characterization Unit, located on our campus in Bethesda, Maryland. This unit will provide
reliable and standardized data derived from assays performed on human embryonic stem cell lines
available for shipment to the research community. The unit will provide a direct side-by-side
comparison to be made among the cell lines, and will facilitate comparison with adult stem cells.
These data will be publicly available and will arm the scientific community with state-of-the-art
information, so scientists can make an informed choice when ordering one or more of the available
In response to additional recommendations from the research community, we continue our efforts
to recruit new scientists to the field, to help mid-career investigators begin studies on embryonic
stem cells, to monitor the state-of-the science through the NIH Stem Cell Task Force, to fund
investigator-initiated grants, to disseminate information about the science and initiatives via the
NIH Stem Cell Task Force website and to plan for a symposium that will bring together two hundred
stem cell researchers from all over the country and several foreign universities.
Again, I want to assure the committee of NIH's commitment to pursuing embryonic stem cell
research, as well as continuing our advances in the field of adult stem cell research. The
President's policy has provided us the opportunity to be at the forefront of the latest
groundbreaking discoveries in the culturing, characterization and differentiation of stem cells,
and I am confident that NIH will keep its premier place in this field for years to come.