Stem cells are defined by two properties. First, they can ‘self-renew,’ that is they can divide and give rise to more stem cells of the same kind. Second, they can mature or ‘differentiate’ into specialized cells that carry out a specific function, such as in the skin, muscle, or blood. There are many different types of stem cells. These include embryonic stem cells that exist only at the earliest stages of development; and various types of ‘tissue-specific’ stem cells (sometimes referred to as ‘adult’ or ‘somatic’ stem cells) that are found in various tissues in our bodies. Recently, cells with properties similar to embryonic stem cells, referred to as induced pluripotent stem cells (iPS cells), have been engineered from specialized cells such as skin cells.
Stem cells have two important characteristics (features) that distinguish them from other types of cells. Self-renewal - the ability to go through numerous cycles of cell division while maintaining the undifferentiated state. Unlimited potency - under certain physiologic or experimental conditions, they can be induced to become cells with special functions such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas.
There are different types of stem cells depending upon the source they are derived. • Embryos – Embryonic stem cells (ESCs) • Fetal Tissue – Fetal stem cells • Cord Blood - Cord blood stem cells • Adult Tissue - Adult stem cells – which includes Hematopoietic stem cells Mesenchymal stem cells Neural stem cells Muscle derived stem cells Pancreatic stem cells Hepatic stem cells
Researchers and doctors hope stem cell studies can help to: Increase understanding of how diseases occur. By watching stem cells mature into cells in bones, heart muscle, nerves, and other organs and tissue, researchers and doctors may better understand how diseases and conditions develop. Generate healthy cells to replace diseased cells (regenerative medicine). Stem cells can be guided into becoming specific cells that can be used to regenerate and repair diseased or damaged tissues in people. People who might benefit from stem cell therapies include those with spinal cord injuries, type 1 diabetes, Parkinson's disease, heart disease, stroke, burns, cancer and osteoarthritis. Stem cells may have the potential to be grown to become new tissue for use in transplant and regenerative medicine. Researchers continue to advance the knowledge on stem cells and their applications in transplant and regenerative medicine. Test new drugs for safety and effectiveness. Before using investigational drugs in people, researchers can use some types of stem cells to test the drugs for safety and quality. This type of testing will most likely first have a direct impact on drug development first for cardiac toxicity testing. New areas of study include the effectiveness of using human stem cells that have been programmed into tissue-specific cells to test new drugs. For the testing of new drugs to be accurate, the cells must be programmed to acquire properties of the type of cells targeted by the drug. Techniques to program cells into specific cells continue to be studied. For instance, nerve cells could be generated to test a new drug for a nerve disease. Tests could show whether the new drug had any effect on the cells and whether the cells were harmed.
Cells or tissues from the same individual; an autologous bone marrow transplant involves one individual as both donor and recipient.
Allogeneic Cells: “Cells from another;” refers to cells that come from someone else’s tissue, like that of a donor. Also refers to the type of therapy that uses a tissue or cells that come from another person.
Cells derived from very early in development, usually the inner cell mass of a developing blastocyst. These cells are self-renewing (can replicate themselves) and pluripotent (can form all cell types found in the body).
Embryonic stem cells are obtained from early-stage embryos — a group of cells that forms when a woman's egg is fertilized with a man's sperm in an in vitro fertilization clinic. Because human embryonic stem cells are extracted from human embryos, several questions and issues have been raised about the ethics of embryonic stem cell research.
The ability to give rise to all the cells of the body and cells that aren’t part of the body but support embryonic development, such as the placenta and umbilical cord.
Stem cells that can become all the cell types that are found in an implanted embryo, fetus or developed organism. Embryonic stem cells are pluripotent stem cells.
Induced pluripotent cells (iPS cells) are stem cells that were engineered (“induced”) from non-pluripotent cells to become pluripotent. In other words, a cell with a specialized function (for example, a skin cell) that has been “reprogrammed” to an unspecialized state similar to that of an embryonic stem cell.
Stem cells derived from perinatal sources, such as amniotic fluid, placenta and placental membranes, the umbilical cord and Wharton’s jelly. These stem cells also have the ability to change into specialized cells.
Stem cells that can give rise to several different types of specialized cells in specific tissues; for example, blood stem cells can produce the different types of cells that make up the blood, but not the cells of other organs such as the liver or the brain.
These stem cells are found in small numbers in most adult tissues, such as bone marrow or fat. Compared with embryonic stem cells, adult stem cells have a more limited ability to give rise to various cells of the body.The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found.
Adult stem cells typically generate the cell types of the tissue in which they reside. However, a number of experiments over the last several years have raised the possibility that stem cells from one tissue may be able to give rise to cell types of a completely different tissue, a phenomenon known as plasticity. Examples of such plasticity include blood cells becoming neurons, liver cells that can be made to produce insulin, hematopoietic stem cells that can develop into heart muscle and mesenchymal stem cells have the potency to develop bone, neurons, myocardium, endothelium, muscle tissues etc. Adult stem cells are safer and have no ethical issues when compared to embryonic stem cells and therefore, exploring the possibility of using adult stem cells for cell-based therapies has become a very active area of investigation by researchers.
A general term for non-blood cells in the bone marrow, such as fibroblasts, adipocytes (fat cells) and bone- and cartilage-forming cells that provide support for blood cells. Contained within this population of cells are multipotent bone marrow stromal stem cells that can self-renew and give rise to bone, cartilage, adipocytes and fibroblasts.
A term used to describe cells isolated from the connective tissue that surrounds other tissues and organs. MSC’s are multipotent stem cells that can differentiate into a variety of cell types. MSCs were first isolated from the bone marrow and shown to be capable of making bone, cartilage and fat cells. MSCs are now grown from other tissues, such as fat, cord blood and cord tissue apart from other tissues of the body. Not all MSCs are the same and their characteristics depend on where in the body they come from and how they are isolated and grown.
In addition to having regenerative potential, mesenchymal stromal cells are safer and have no ethical issues when compared to embryonic stem cells. Therefore, they are being actively explored for the treatment of various disorders which as of now have no or limited cure.
Studies of human embryonic stem cells may yield information about the complex events that occur during human development. Medical researchers believe that stem cell therapy has the potential to radically change the treatment of human disease. A number of adult stem cell therapies already exist, particularly bone marrow transplants that are used to treat leukemia. In the future, medical researchers anticipate being able to use technologies derived from stem cell research for generation of cells and tissues that could be used for cell-based therapies.
Stem cell therapy, also known as regenerative medicine, promotes the repair response of diseased, dysfunctional or injured tissue using stem cells or their derivatives. A stem cell therapy is a treatment that uses stem cells, or cells that come from stem cells, to replace or to repair a patient’s cells or tissues that are damaged. The stem cells might be put into the blood, or transplanted into the damaged tissue directly, or even recruited from the patient’s own tissues for self-repair.
This process is also known as clinical translation. The process starts with very general research into how a tissue or cell usually works and what goes wrong in a particular disease or injury. This information is used to design and develop ways to diagnose, stop or fix what goes wrong. To test whether and how a new intervention might work for a particular disease or injury, studies are done first in vitro (in a dish), and then wherever possible in animals with a disease or injury like ours. These are referred to as preclinical studies; preclinical studies should be reviewed by other experts, published and repeated before moving to research in patients. After demonstrating a reasonable expectation that the treatment will work and be safe, permission is sought to conduct a clinical trial in humans, starting with a very small number of individuals. In some cases, new experimental treatments might be tried on a very small number of people before a clinical trial is started. As the safety and side effects are better understood and methods to get the treatment to the correct part of the body are improved, the number of patients is gradually increased and the new intervention is compared against existing treatments. Once safety and effectiveness is demonstrated through this formal process, a national l regulatory agency, for example, Indian Central Drugs Standard Control Organisation (CDSCO)), will approve the use of the treatment for particular diseases or conditions.
An approved clinical treatment is a medical practice that has been shown through a formal process of clinical trials to be reasonably safe and effective for treating a particular disease or condition. Normally, such treatments will be approved by a national regulatory agency, for example, the CDSCO. An experimental intervention is new, untested, or different from the usual medical treatment. It has not yet been proven that it is safe or that it will work in treating the particular disease.
No medical treatment can ever be described as completely safe. There are risks involved with all medical treatment, some small, some great. These risks, even if they are small, should be explained clearly to you by a medical professional.
You need to be sure that there is good scientific evidence that the treatment is safe and effective, and that your rights as a patient are being respected. To begin, ask for evidence that: Preclinical studies have been published, and reviewed and repeated by other experts in the field. The providers have approval from a National Regulatory Agency like CDSCO, for the safe conduct of clinical trials or medical use of a product for this disease.
Ask your medical doctor for advice on what is available in your area for your disease or condition. Different clinical trials are offered at different institutions. Remember that clinical trials have very strict entry criteria to safeguard the safety of participants and to make sure that researchers will be able to answer their research question. There are some databases that allow you to search for registered clinical trials. For example, the public may search a database of clinical trials at The Clinical Trials Registry- India (CTRI), hosted at the ICMR's National Institute of Medical Statistics. at http://ctri.nic.in/Clinicaltrials/login.php.