Why are doctors and scientists so excited about stem cells?
Stem cells have potential in many different areas of health and medical research.
- Studying stem cells will help us to understand how stem cells transform into the array of specialized cells that make up the human body. Some of the most serious medical conditions, such as cancer and birth defects, may result from problems that occur in this process of differentiation. A better understanding of normal cell development will allow us to understand and perhaps correct the errors that cause these medical conditions.
- Stem cells will provide a tool for pharmacologic development. Stem cell research should allow the development of cell populations with a specific 'disease.'These cell populations can then be used for initial testing with candidate drugs.
- Finally, perhaps the most exciting potential application of stem cells is cell therapy. Pluripotent stem cells offer the possibility of a renewable source of replacement cells and possibly tissues to treat a myriad of diseases, conditions, and disabilities including Parkinson's disease, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis.
What are the differences between adult stem cells and embryonic stem cells?
Adult and embryonic stem cells differ in the type of cells that they can develop into.Embryonic stem cells can become all cell types of the body (they are pluripotent). Adult stem cells are found in mature tissues (bone marrow, skin, brain, etc.) and give rise to other cell types from their tissue or origin (they are are multipotent). For example, adult blood stem cells give rise to red blood cells, white blood cells and platelets.
Why not use adult stem cells instead of using human embryonic stem cells in research?Adult stem cells are thought to exist in every type of tissue in the body. But, to date, the isolation of many types of adult stem cells has been limited. Hematopoietic (blood) stem cells are readily available via bone marrow aspiration. But stem cells for solid organs such as liver or brain have proven more difficult to identify and derive. The hope is that hESCs can be used to derive every type of adult stem cell in the body and allow research that is currently not possible.
Where do human embryonic stem cells come from?
Embryonic stem cells are isolated from 3 to 5 day old human embryos at the blastocyst stage. The blastocyst is a hollow microscopic cluster of several hundred undifferentiated cells.
What is a human embryonic stem cell line?
This is a culture of hESCs derived from a single embryo. Because stem cells can self-replicate, just a few hESCs can give rise to a whole population of identical hESCs, or a cell line.
Why do scientists want to use stem cell lines?
Once established, a cell line can be grown in the laboratory indefinitely and cells may be frozen for later use or distributed to other researchers. Because each cell line has its own distinct genetic footprint, researchers are often interested in using the same cell line for a number of related experiments.
Have human embryonic stem cells been used successfully to treat any human diseases yet?
No. At this point, the promise is huge, but hESC research is still in its early stages. Human embryonic stem cell (hESC) research only began in 1998, when a group led by Dr. James Thomson at the University of Wisconsin developed a technique to isolate and grow the cells.
In late January 2009, the California-based company Geron received FDA clearance to begin the first human clinical trial of cells derived from human embryonic stem cells.
In contrast, research with adult stem cells such as blood-forming stem cells in bone marrow (called hematopoietic stem cells, or HSCs) has been active for over decades. And this research has resulted in treatment of patients; for example, bone marrow (stem cell) transplants have been conducted for over 40 years.
In addition, studies with a limited number of patients have demonstrated the clinical potential of adult stem cells in the treatment of other human diseases that include diabetes and advanced kidney cancer.
What are induced pluripotent stem cells?
Induced pluripotent stem cells (iPS cells) are cells that began as normal adult cells (for example, a skin cell) and were engineered (‘induced’) by scientists to become pluripotent, that is, able to form all cell types of the body. This process is often called 'reprogramming.' While iPS cells and embryonic stem cells share many characteristics they are not identical. Scientists are currently exploring whether they differ in clinically significant ways.
Do iPS cells eliminate the need for embryonic stem cells?
The technology used to generate iPS cells holds great promise for creating patient- and disease-specific cell lines for research purposes. These cells are already useful tools for drug development and scientists hope to use them in transplantation medicine. However, additional research is needed before the reprogramming techniques can be used to generate stem cells suitable for safe and effective therapies.
What is Somatic Cell Nuclear Transfer?
Somatic cell nuclear transfer (SCNT), is a technique in which the nucleus of a somatic cell (any cell of the body except sperm and egg cells) is injected, or transplanted, into an egg, that has had its nucleus removed. The product of SCNT has the same genetic material as the somatic cell donor.
Is Somatic Cell Nuclear Transfer the same as Cloning?
Yes. SCNT is a technique of cloning. The product of SCNT is nearly genetically identical to the somatic cell used in the process. (Of note, the product of SCNT is not technically 100% identical in that the cytoplasm of the oocyte includes mitochondrial DNA.) While SCNT is considered cloning, it is important to differentiate between therapeutic and reproductive cloning. The following FAQ addresses these differences.
What is the difference between therapeutic cloning and reproductive cloning?
Reproductive cloning includes the placement of the product of SCNT into a uterus for the purpose of a live birth. The resulting organism would, in theory, be the genetic copy of the somatic cell donor. Reproductive cloning has been performed in animals for many years and is burdened by many technical and biological problems. Only about 1 percent of all the eggs that receive donor DNA can develop into normal surviving clones. Therapeutic cloning uses SCNT for the sole purpose of deriving cells for research, and potentially in the future for therapy. In therapeutic cloning, the product of SCNT is not placed into a uterus and hence a live birth is never a possibility. Therapeutic cloning provides two potential benefits.
- The first is for studying specific diseases. If the somatic cell donor has a genetic disease, such as muscular dystrophy, the product of SCNT would also have muscular dystrophy genes. Cells derived from this SCNT product could then be used to study the biology of muscular dystrophy with the goal of finding new ways to prevent, treat or even cure the disease.
- The second is to create 'designer cells' for transplantation. Whenever cells, tissue or entire organs are transplanted from one person to another, the recipient's immune system sees the new material as foreign and tries to reject the transplant. In order to avoid this, transplant recipients are given drugs that modulate the recipient's immune system to avoid rejection. Therapeutic cloning offers a possible solution. If Ms. Jones needs a transplant, a somatic cell from Ms. Jones could be used for SCNT. The resultant product would have the same genetics as Ms. Jones. The cells derived and grown for transplant would be accepted by Ms. Jones' immune system as one of their own.
Does Massachusetts state law permit human embryonic stem cell research?
Yes. Massachusetts state law that was enacted in May 2005 allows hESC research and it allows the derivation of hESCs from embryos that were created for reproductive purposes and are no longer needed for reproduction and from somatic cell nuclear transfer.
What are the NAS guidelines?
The National Academy of Sciences (NAS) issued guidelines for hESC research in April 2005, and subsequently updated those guidelines in 2007 and 2008. The current guidelines contain detailed recommendations with regard to many aspects of hESC research, including:
- donor recruitment and informed consent
- how stem cells should be characterized, handled, transferred, and stored
- the establishment of local Embryonic Stem Cell Research Oversight (ESCRO) Committees
- guidance on what kinds of research should be considered for approval and what kinds should be prohibited at this time
Is Institutional Review Board (IRB) approval required for all hESC research?
No. IRB approval is required for:
- the derivation of hESCs from existing embryos or SCNT
- research using hESCs if the identity of the gamate and/or somatic cell donors is known to the researcher. No IRB approval is required for the use of de-identified exising hESCs.
Does the federal government fund embryonic stem cell research?
Until recently, the federal government limited its funding to specific hESCs derived before August 9, 2001. Specifically, federal funds were only allowed for research on hESCs listed on the National Institutes of Health (NIH) Registry, and on derivative products from hESCs on the NIH Registry. On March 9, 2009, President Obama signed an executive order clearing the way for the NIH and other federal agencies to fund research using all kinds of hESCs.
What is the source of the Center for Regenerative Medicine’s human embryonic stem cell research funding?
Human embryonic stem cell research at the Center for Regenerative Medicine has been supported in part by private philanthropic donations. These donations allowed us to support a wide range of research activities that could not have been supported from other sources such as NIH funding. In the future, we expect to receive support for eligible activities from NIH and other funding agencies.
How can I donate money to the Center for Regenerative Medicine?
The Center for Regenerative Medicine depends upon philanthropic support. To find out how you can help accelerate research and discovery, please click here.
What’s unique about the Center for Regenerative Medicine?
The Center for Regenerative Medicine is dedicated to understanding how tissues are formed and may be repaired in settings of injury. Embedded at Mass General Hospital, the Center's primary goal is to develop novel therapies to regenerate damaged tissues and thereby overcome debilitating chronic disease. The success of this effort requires a cohesive team of scientists and clinicians with diverse areas of expertise, but with a shared mission and dedication to the larger goal.
The Center for Regenerative Medicine has extensive interactions with other investigators at MGH and in the broader Harvard-MIT community. The Center helped galvanize the establishment of the Harvard Stem Cell Institute (HSCI), which is co-directed by Dr. Scadden and Dr. Douglas Melton of Harvard's Department of Stem Cell and Regenerative Biologyand the Howard Hughes Medical Institute. As an important confederated partner of HSCI, the Center brings specific features that augment other elements of HSCI, including unique stem cell clinical investigation expertise and ongoing collaborative clinical trials using stem cell transplantation. The Center emphasizes technologies that will ultimately be critical for the success of stem cell based medicine, including bioengineering, biomaterials expertise, close links to in vivo imaging capability and its GMP facility for sophisticated cell manipulation.