Widely touted as a source of great hope for use in regenerative medicine, stem cells are being investigated for use in the development of new drugs to prevent and treat illnesses including Parkinson’s disease, spinal cord injury and peripheral vascular disease.
Stem cells are cells in the body that can specialize into particular types of cells. The process of specializing is known as differentiation. Differentiation occurs when specific genes are activated or silenced to induce cell behaviour in accordance with its function.
Adult stem cells occur naturally in different parts of the body but typically grow slowly, are rare and difficult to isolate, and can only develop into a limited range of other cell types. For research purposes, embryonic stem cells are preferred as they can be readily expanded in culture and grown indefinitely, and they also possess the unique potential to form any tissue in the body (aside from extra-embryonic tissues such as placenta).
Haematopoietic stem cells—those that give rise to all different blood types—are currently used for the clinical treatment of leukemia and lymphoma via autologous (cells are reintroduced into the same patient) or allogeneic (cells are donated from a different individual who is closely matched) transplant.
Human embryonic stem cells are derived from the cells of an early pre-embryo less than six days old (and consisting of less than 100 cells) that has not yet implanted in the uterus wall.
Induced pluripotent stem cells (iPS cells) are derived typically from fully differentiated cells that have been genetically altered, or reprogrammed, to possess the same properties and behaviour as embryonic cells, giving them the ability to differentiate into any of the 220 different cell types in the body, and can be cultured to reproduce indefinitely.
Lunenfeld researchers have switched virtually all human embryonic stem cell work to iPS stem cell-derived cells, which are typically made from skin fibroblasts. Of note, any research using human embryonic stem cell lines is conducted under strict ethical guidance.
For research purposes, iPS cells are preferred because they do not
require embryos as starting points, and can be used to generate cells
from many adult tissues, including skin cells.
Another advantage of using iPS cells is that they allow for cell lines to be genetically customized to patients, reducing the issue of immune rejection that is common during tissue transplantation therapies.
CONTENT FOR SIDEBAR:
What researchers at the Samuel Lunenfeld Research Institute of Mount
Sinai Hospital are contributing to this growing field:
• The first two human embryonic stem cell lines in Canada were established by Dr. Andras Nagy following strict ethical review procedures. These have been approved by the Canadian Institutes of Health Research (CIHR) for use by other scientists and have enabled new insights into stem cell biology and regenerative medicine.
• Dr. Nagy also devised a process for creating stem cells without the use of a viral vector. This new method eliminates the chance of inherited or de novo DNA mutations where there would either be an excess or deletion of DNA segments. His team is also currently exploring each phase of the programming process, to help make future stem-cell based applications safer and more efficient.
• Dr. Ian Rogers is on the forefront of creating stem-cell based treatments for diabetes and peripheral vascular disease. He and his colleagues are using stem cells to create natural replacements for essential cells in the pancreas that are destroyed by the illness, specifically in type 1 diabetes.
• Dr. Rita Kandel and her team are developing biologic replacements for damaged joints and tissues, using stem cells from the patient’s own tissues.