Frequently Asked Questions
- What are stem cells and why do we hear so much about them?
- How are stem cells obtained?
- Why is stem cell research so important?
- What is the difference between embryonic and adult stem cells?
- Why is there so much controversy surrounding embryonic stem cell research?
- What is the source of embryos used for deriving embryonic stem cells?
- What is somatic cell nuclear transfer?
- What is the difference between therapeutic and reproductive cloning?
- What are induced pluripotent stem (iPS) cells?
- Can iPS cells eliminate the need for embryonic stem cells in research?
- How have the changes in policy under the Obama administration affected stem cell research and its funding?
- Have embryonic stem cells been used to treat any diseases in humans?
- When will stem cell research lead to new disease cures?
- Are there other uses of stem cells beside using them to treat disease?
- Why create a Stem Cell Institute at Harvard?
- What types of research does HSCI support?
- What is the source of HSCI funding?
- Where can I learn more about HSCI activities?
- How can I give money to the HSCI to support its mission?
What are stem cells and why do we hear so much about them?
Scientists have known of the existence of stem cells - the foundation of every organ, tissue, and cell within the human body - for over a century. Yet it has been only since the late 1990s, when human embryonic stem cells were first cultured in the laboratory, that the field of stem cell research has become the focus of intense scientific interest, social and political controversy, and therapeutic potential.
Like a blank microchip that can be programmed to perform many different tasks, stem cells are undifferentiated, 'blank' cells that do not yet have a specific physiological function. When the proper conditions occur in the body or in the laboratory, stem cells begin to develop into specialized tissues and organs. Stem cells are also distinguished from other cells by their ability to self-renew. In other words, to divide and give rise to more stem cells.
How are stem cells obtained?
There are several sources of stem cells used in research. Embryonic stem cells are obtained from the inner cell mass of a blastocyst. The blastocyst is formed when the fertilized egg, or zygote, divides and forms two cells, then again to form four, and so on until it becomes a hollow ball of about 150 cells. The ball of cells, now called the blastocyst, actually contains two types of cells -- the trophoblast, and the inner cell mass. The inner cell mass contains the pluripotent stem cells that can be isolated and cultured.
Stem cells are also found in differentiated tissues and organs througout the body. Often referred to as adult stem cells, or tisssue-specific cells, they have not been identified in all tissues and organs, but in many cases they do exist and have a confirmed roll in repairing and maintaining tissue that has been injured or damaged by disease. The adult stem cells can be isolated from samples of the tissue, with the cells suspended in liquid and separated based on cell surface markers using fluorescence activated cell sorting (FACS).
Blood from the umbilical cord of a newborn baby also contains blood stem cells and is often harvested and banked for future use, either for the benefit of research or for future treatments that the donor may require. The amniotic fluid is another rich source of stem cells that are multipotent and often more robust than stem cells derived by other means.
Lastly, induced pluripotent stem cells (iPS cells) can be derived from the large pool of differentiated cells in the body (e.g. skin, fat, muscle, etc), which are tranformed into an embryonic-like stem cell state.
Why is stem cell research so important?
Stem cells are the source of all tissues of the body, and understanding their properties is fundamental to our understanding of human biology in health and disease. In particular, stem cells offer the possibility of a renewable source of replacement cells to treat a wide variety of diseases and disabilities, including diabetes, neurological disease, cardiovascular disease, blood disease and many other conditions. Stem cells can also provide a source of material for growing and maintaining cells in the laboratory for specific tissues, or even with specific diseases, enabling more relevant and informative biological assays. Defective stem cells also appear to underlie many forms of cancer, and by understanding their properties it should be possible to develop new types of anti-cancer therapy.
What is the difference between embryonic and adult stem cells?
Some organs contain stem cells, called adult stem cells, that persist throughout life and contribute to the maintenance and repair of those organs. Not every organ has been shown to contain these cells, and generally adult stem cells have restricted developmental potential, in that their capacity for proliferation is limited and they can give rise only to a few cell types. Embryonic stem cells, by contrast, can divide almost indefinitely and can give rise to every cell type in the body, suggesting that they may be the most versatile source of cells for research and transplantation therapy.
What are induced pluripotent stem (iPS) cells?
Induced pluripotent cells are derived from somatic (adult, non-germline) cells, which have been reverted to an embryonic stem cell-like state. Like embryonic stem cells, iPS cells can be differentiated into any cell in the body, and are therefore considered pluripotent. The process of creating these cells, often referred to as "reprogramming," involves introducing a combination of three to four genes for transcription factors delivered by retroviruses into the somatic cell. More recent methods have replaced and reduced the number of genes required for the transformation, used alternative delivery methods to get the genes into the cell, or sought to replace the genes with chemical factors.
Cells can be taken from patients with specific diseases such as ALS, Parkinson's, or cardiovascular disease and induced to form iPS cells. Multiple uses can be derived from iPS cells when they are differentiated to more specialized cell types, including the development of assays for studying disease processes, scanning drug candidates for safety and effectiveness, or application to regenerative medicine.
Can iPS cells eliminate the need for embryonic stem cells in research?
Although scientists would welcome alternative sources to obtaining pluripotent cells from embryos, they remain the only reliable source. iPS cells share many of the characteristics of embryonic stem cells including pluripotency, but differences remain. One study identified 271 genes that were expressed differently between iPS and embryonic stem cells, and variability in iPS cells has been observed depending on their tissue source. Technological hurdles remain for iPS cells to be used in a clinical setting, because several of the genes used to induce transformation from adult cell to an embryonic-like state are linked to cancer. Work continues on finding safer methods of induction and determining whether iPS cells can fully replace the function and capabilities of true embryonic stem cells.
Embryonic stem cells remain the gold standard. If iPS technology (often referred to as "reprogramming") is to eventually replace embryonic stem cells in research, it will be because the results were compared and refined against stem cells from a true embryonic source. As it is today, all methods and stem cell sources -- reprogramming, somatic cell nuclear transfer, adult stem cells and embryonic stem cells -- are an essential part of the research effort to improve our undertanding of disease, its underlying causes, and potential cures.
Why is there so much controversy surrounding embryonic stem cell research?
At present, the only known way to derive embryonic stem cells involves the destruction of an unimplanted blastocyst-stage embryo at the sixth to eighth day of development. Some people are opposed to this research because they consider the blastocyst to be morally equivalent to a human individual. Proponents argue that the embryo at this stage has only the potential, but not the moral equivalence of a human, and that embryonic stem cell research holds great promise for understanding and curing diabetes, Parkinson’s disease, spinal cord injury, and other debilitating conditions. The controversy around the ethics of stem cell research has grown in the last 10 years as political parties use it as a dividing line to gain the support of constituents.
What is the source of embryos used for making embryonic stem cells?
The human embryonic stem cell lines that have been created at Harvard are derived from frozen embryos left over after in vitro fertilization (IVF) treatment and would otherwise have remained unused or discarded. These early stage embryos were donated, with informed consent, by patients who had completed their treatment. Harvard researchers also hope to derive embryonic stem cells by somatic cell nuclear transfer, or by producing embryonic-like induced pluripotent stem (iPS) cells through the reprogramming of mature adult cells.
What is somatic cell nuclear transfer?
Somatic cell nuclear transfer (SCNT), sometimes known as '"therapeutic cloning," involves transferring a nucleus from a donor cell, such as a skin cell, into an unfertilized egg. The injected egg is then induced to divide, and when it reaches a few hundred cells, the so-called blastocyst stage, it can be used to derive embryonic stem cells that are genetically identical to the original donor. No sperm is involved, and, therefore, no fertilization occurs in this procedure. Moreover, because the blastocyst is not implanted in a uterus, no pregnancy is established. SCNT has great therapeutic promise because the resulting stem cells could be transplanted into the original donor and would be recognized as "self," thereby avoiding the problems of rejection and immunosuppression that occur with transplants from unrelated donors. In addition to providing a source of material for transplantation therapy, SCNT can also be used to make stem cells that carry disease genes. These cells could provide a powerful new tool for studying the basis of human disease and for discovering new drugs.
What is the difference between therapeutic and reproductive cloning?
Reproductive cloning involves creating an embryo by nuclear transfer and then implanting it into a uterus and allowing it to establish a pregnancy. This has been achieved for sheep and several other mammalian species. It is not known whether it could be made to work in humans, but the vast majority of researchers in the field are strongly opposed to attempting such an experiment. Many countries and some US states have already enacted legislation that permits therapeutic cloning, which produces embryos to obtain stem cells only and are not implanted, while prohibiting reproductive cloning. Harvard has supported such legislation in Massachusetts.
How have the changes in policy under the Obama administration affected stem cell research and its funding?
Under the previous administration policy, only about 22 embryonic stem cell lines (created before August 2001) were available for distribution to researchers under federal funding. These federally approved cell lines were limited in their utility for a variety of reasons, including lack of genetic diversity, chromosomal abnormalities, exposure to and potential contamination by mouse feeder cells, and poor growth characteristics. Other sources of funding existed to support research and the creation of new embryonic stem cell lines, but equipment and facilities had to be duplicated in order to avoid using federally funded resources for anything linked to embryonic stem cell research.
In March of 2009, President Obama signed an executive order overturning Bush-era stem cell research policies. The new order allows for federal grants to support studies using existing embryonic stem cells regardless of when they were created, and on new cell lines if they were created from embryos left over from in vitro fertilzation (IVF) and with the donor's consent. The change in policy has not opened the floodgates of funding for this area of research, as investigators must now compete with all other areas of research for scarce NIH grants. Furthermore, restrictions on the funding of embryonic stem cell research continues, as the Obama order stipulates only discarded IVF embryos may be used, and not new embryos provided by donors.
Have embryonic stem cells been used to treat any diseases in humans?
Not yet. Although embryonic stem cell research has shown great potential, the field is still relatively new. Moreover, in the US and some other countries, progress has been slowed by funding and regulatory restrictions. Nevertheless, progress has been made in the introduction of the first clinical trial using embryonic stem cells in the area of treating spinal cord injury.
While research and new treatments using embryonic stem cells may see a resurgence with new federal policies on funding, a great deal of focus is now turning toward induced pluripotent stem (iPS) cells, which are derived from adult cells and not embryos. iPS cells could be used to generate specific tissues for regenerative medicine, but technological hurdles remain - including the need for iPS protocols that do not rely on genes and delivery vectors linked to cancer.
When will stem cell research lead to new disease cures?
Adult stem cell-based therapies are already in widespread clinical use and have been for over 40 years, in the form of bone marrow transplants. These procedures, used to teat leukemia, lymphoma and inherited blood disorders, save many lives every year, and demonstrate the validity of stem cell transplantation as a therapeutic concept. New clinical applications are being explored using stem cells for the treatment of multiple sclerosis, cardiavascular disease, stroke, autoimmune and metabolic disorders, and chronic inflammatory diseases in addition to blood cancers. While human clinical trials have begun in many of these applications, it may still be a matter of years before these treatments become widely available to the patient. Nevertheless, we are optimistic that successes will be possible, and that new stem cell based treatments will become available as they complete clinical trials.
Are there other uses of stem cells beside using them to treat disease?
Yes. Stem cells can be used to generate cell lines specific to a particular patient with a particular disease. By matching the biological data from these cells with the clinical history of the patient, it may be possible to extract more relevant information on the linkage between molecular pathways and the causes of disease.
Cell lines can be derived from stem cells for specific tissues, such a heart muscle, specific types of neurons, kidney cells, etc. and used in biological assays to screen thousands of chemical compounds for their safety and effectiveness in treating disease.
Stem cells also play an important role in expanding our understanding of embryonic and fetal development, helping us to identify the cells and molecules responsible for guiding the patterns of normal (and abnormal) tissue and organ formation.
So stem cells are more than just a source of potential replacement parts. They provide us today with an essential tool for better understanding normal and disease biology, and evaluating other modes of treatment.
Why create a Stem Cell Institute at Harvard?
Stem cells represent an extraordinary opportunity and challenge that involves areas of expertise not encompassed in any one discipline, department or school. For example, basic biology must interface with medical expertise if the promise of this field is to be fully realized. At the same time, clinical and laboratory scientists must engage with those attuned to the political, societal and ethical implications of the research. The excessively politicized and emotional debate engendered by stem cell research requires a champion institution whose tradition of rational deliberation can balance the voices of opinion with a strong counterweight of exceptional science. Harvard, with its tradition of academic excellence, its diversity of basic and clinical expertise, and its strong links to a thriving local biotechnology community, is exceptionally well positioned to play such a role and to establish itself as the world's leading center for stem cell research.
What types of research does HSCI support?
HSCI supports research into all aspects of stem cell biology, including both embryonic and adult stem cells, and the development of new and improved technologies, such as the production of induced pluripotent stem cells. Our primary emphasis is on the search for new therapies for serious diseases, including, among others, diabetes, neurological disease, cardiovascular disease, kidney disease, blood disease and cancer.
What is the source of HSCI funding?
HSCI is supported primarily by private philanthropic donations. These donations allow us to support a wide range of research activities that could not be supported from other sources such as NIH funding. In the future, we also expect to apply to NIH and other funding agencies for support of activities that are eligible for such funding.
Where can I learn more about HSCI activities?
Further details of our research programs and other activities are given throughout this web site and in our annual report, available here in PDF format. Click here for information on how to join HSCI's mailing list.
How can I donate money to the HSCI?
Since many of our research activities are not eligible to receive federal funding, the HSCI depends upon philanthropic support. To learn more about how to support our programs, please visit our Support section by clicking here.