Stem Cell FAQs


Stem cells can be thought of as the master cells from which other cell types are derived.  They are present in the fetus, child and adult and can come from different sources.  All stem cells, regardless of their source, have three general properties:

1. They are capable of dividing and renewing themselves for long periods.
2. They are unspecialized.
3. They become specialized cell types (this is called cell differentiation).

Understanding some of the fundamental properties of stem cells that relate to their long-term self-renewal may bring an understanding of how cell proliferation is regulated during normal embryonic development, as well as during the abnormal cell division that leads to cancer.    

What are adult stem cells? 
Adult stem cells are undifferentiated cells that can become the major specialized cell types of a given tissue or organ.  They can be found in children and well as adults. 

Adult stem cells are capable of dividing to replenish dying cells and regenerate damaged tissue. They are found throughout the body—in tissues such as bone marrow, brain, muscle and liver. Because adult stem cells are not differentiated into specialized cell types, they remain immature. When tissue becomes damaged, the adult stem cells divide to produce new cells. Some of the resulting cells divide, but unlike stem cells they mature to take over for the damaged cells. Within any organ or tissue, generally only the stem cells have the ability to self-renew and appear to be the only cells that regenerate tissues when they become damaged.   

What can be learned by studying adult stem cells? 
Research on adult stem cells has generated a great deal of excitement.  Certain kinds of adult stem cells seem to have the ability to differentiate into a number of different cell types. Given the right conditions they may have utility in regenerative medicine, where stem cells are induced to differentiate into the specific cell type required to repair damaged or destroyed cells and tissue. If differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of therapies for many serious common diseases.

Studying adult stem cells can teach researchers about processes that lead to cancer and other diseases. Most mature cells of the body no longer divide. In many cancerous tissues, genes that block the cell from dividing and direct cells to mature are turned down or off, and genes that stimulate division are turned on. In many cancers studied thus far, a small population of cells, called cancer stem cells, self-renews to replenish the growing cancer. These cancer stem cells can use the same genes that adult stem cells use in the process of self-renewal. By studying adult stem cells to learn more about the genes involved in self-renewal, it may be possible to identify new targets for drug and immune therapies that destroy the self-renewing cancer stem cells. 

One important area of research involves learning whether all cancers have cancer stem cells. Learning which genes are used in self-renewing adult stem cells compared with cancer stem cells in the same tissue is also important since both cells self-renew, but only the cancer cells grow indefinitely and spread to other organs.  Identifying which genes are mutated or used differently in the cancer cells may help researchers develop drugs to block that behaviour. 

Adult stem cells are also used to learn more about the adult tissues from which those stem cells derive. Researchers have already identified adult stem cells in the brains of mice and humans, and can now use those stem cells to understand how the cells of the developing brain differentiate into the many different cell types found in the adult brain. This work may bring an understanding of what processes become skewed in neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. Identifying adult stem cells from other tissues may bring an understanding of how the tissues develop and what goes wrong when those tissues become diseased.   

How can adult stem cells be used to treat disease? 
Adult stem cells can be used to replenish damaged tissue. One current example of this is in bone marrow transplants, where blood-forming stem cells regenerate the blood of transplant recipients who receive otherwise lethal doses of chemotherapy to destroy all the cancer cells in the body. But there is hope that large populations of adult stem cells can be grown outside of the body and be used in the future to treat diseases like diabetes, Parkinson’s and traumatic injuries.  

What are embryonic stem cells? How are they different from adult stem cells? 
Embryonic (also known as pluripotent) stem cells have the ability to become many different kinds of cells in the body. Like adult stem cells, pluripotent stem cells are capable of self-renewal. Pluripotent stem cells are unique.  They provide the starting material for every organ and tissue, and have the potential to develop into each of the more than 200 cell types in the human body—bone, muscle, skin, blood, etc., but are not able to form a complete organism.  

Adult stem cells from a given tissue appear to only form cells found in that tissue.  Pluripotent stem cells are derived from very early embryos, at the stage when the embryo is just visible with the naked eye and consists of only 100 or so cells.  These embryos or blastocysts develop from eggs that have been fertilized in vitro—in an in vitro fertilization clinic—and are donated for research purposes with the informed consent of donors.  They are not derived from eggs fertilized in a woman’s body.  

Pluripotent stem cells that have proliferated in cell culture for six or more months without differentiating and appear genetically normal, are referred to as an embryonic stem cell line.    

What can be learned by studying pluripotent stem cells? 
Studying mouse pluripotent stem cells carrying disease-causing mutations has already greatly enhanced scientific and medical knowledge of how genetic diseases develop. The hope is that a similar knowledge explosion will take place by studying human pluripotent stem cell lines carrying mutations found in such genetic disorders as cancer, Parkinson’s disease, Alzheimer’s disease, Lou Gehrig’s disease, adult and juvenile diabetes, autoimmune diseases, allergic disorders, and early onset heart and cardiovascular disease. 

By studying stem cells that carry DNA with disease-causing mutations, researchers might learn more about how these mutations cause the cell to become diseased. They may also learn how the proteins made by the mutated genes fail to function properly, leading to an understanding of the molecular basis of the disease. This may enable researchers to generate drugs or therapies that make up for the genetic defect and treat the disease.  

How can pluripotent stem cells be used to treat disease? 
Pluripotent or embryonic stem cells have enormous promise for treating degenerative disease because they can be grown in very large numbers and can differentiate into many different cell types in the body. Researchers have to first learn better how to grow the stem cells in a lab so they take on the characteristics of the cells they are meant to replace. At this time it isn’t clear whether pluripotent or adult stem cells will be best in this type of therapy.   

What is the controversy over stem cell research? 
Research with pluripotent stem cell lines is controversial because some people feel, for religious and ethical reasons, that the blastocysts used to generate the cell lines are fully human and should not be used as the source of pluripotent cells. For now, the question of when personhood develops in an individual cannot be settled scientifically, and so it will remain the subject of controversy and debate.   

What are Canadian guidelines regarding stem cell research?
Controversy over stem cell research has prompted authorities around the world to seek regulatory frameworks.

Recognizing the urgent need for clear guidelines that would allow for response to rapidly evolving science and shifting public opinion, and to ensure ethical and scientific oversight, the Canadian Institutes of Health Research (CIHR) announced guidelines for human pluripotent stem cell research in March 2002. The guidelines have been adopted into the Tri-Council Policy Statement: Ethical Conduct for Research Involving Humans, in a manner that is consistent with federal legislation— Bill C-6—which became law in March 2004. Adherence to the guidelines is a condition of agency-funded research. 

Canadian researchers have been pioneers in the area of stem cell research and with the introduction of the guidelines, Canadian researchers are able to move forward and remain at the forefront of their field while conducting their research according to explicit ethical standards. Funding agencies, research ethics boards and universities rely on this framework to guide their evaluation and approval decisions. 

Because of the complex ethical issues and public concern in this area, a Canadian Stem Cell Oversight Committee has been created to conduct ethical review of all human pluripotent stem cell research proposals recommended for approval by federal granting agencies’ scientific peer review panels, or conducted under the auspices of institutions receiving agency funding. All research proposals falling within the scope of these guidelines require approval from this committee, as well as from the local Research Ethics Board and where appropriate, the Animal Care Committee before funds can be released to the researcher.   

Why is SickKids Research Institute involved with stem cell research? 
Although stem cell research is at a very early stage, this field holds enormous potential. Stem cell therapy has the potential to radically change the treatment of human disease.  One day, we will be able to use stem cells to repair cells damaged through accident and disease.  

SickKids has a history of embracing new technologies to aid in the discovery of treatments for children’s diseases. Our scientists work with legal experts and ethicists, always putting respect for patients first and foremost in the mission of advancing knowledge and improving the lives and health of children around the world. 

Ultimately, physicians and scientists have the obligation to pursue the best medical therapies, making sure to do no harm, by translating today’s science into tomorrow’s treatments.