What are Stem Cells?
Stem cells are unspecialised (immature) cells that have the unique potential to develop into specialised cells that perform specific functions. They serve as the foundation from which all other cells develop in the human body. They are found in the foetus, embryo, and some adult tissues, as well.
Unique Characteristics of Stem Cells
- Self-renewal: Capacity to divide and renew themselves for long periods.
- Differentiation: Potential to produce specialised types of cells that constitute different tissues and organs.
Sources of Stem Cells:
- Embryonic stem cells: obtained from embryos
- Adult stem cells: present in adult tissues such as bone marrow, blood
- Cord blood stem cells: obtained from umbilical cord
Different Types of Stem Cells
1. Human embryonic stem cells:
- Human embryonic (pluripotent) stem cells
- Non-embryonic (multipotent) stem cells
- Induced pluripotent stem cells
They are obtained from unused embryos that are developed for in vitro fertilization (IVF), or those that are donated for research. They are capable of producing any type of cell in the body (pluripotent).
Under the right experimental conditions, they can be cultured and studied in their unspecialised state. These cells enable researchers gain insight in to early human developmental processes, study diseases, and establish different modes of treatment that could eventually help restore or replace damaged tissues.2. Non-embryonic stem cells:
Also known as multipotent/adult/somatic/tissue-specific stem cells, they are found in the umbilical cord, placenta, amniotic fluid, and mature adult tissues such as bone marrow. They differentiate themselves to a certain extent and are capable of producing only those cells that make up the organ system they originate from (tissue or organ-specific). Their main function is to repair and replace damaged (worn out or injured) or dead cells.3. Induced pluripotent stem cells:
These are adult cells that are genetically “reprogrammed” so that they become pluripotent, i.e., they lose their specific functioning ability and can give rise to various cells of the body. However, their potential applications need further validation through additional research.
Potential Uses of Human Stem Cells
- Study abnormal cell development: This can help in the development of new methods of treatment for certain medical conditions, such as cancer and birth defects, which are a result of abnormal cell division and differentiation.
- Grow cells to replace tissues or whole organs (cell-based therapy): Given their unique differentiating ability, stem cells serve as a source to renew damaged or dead cells and tissues, and treat a variety of conditions such as spinal cord injuries, heart disease, osteoarthritis, burns, type 1 diabetes, Alzheimer’s disease, Parkinson disease.
- New drug testing: New medications can be first tested on stem cells before they can be used for humans.
What is Stem Cell Therapy?
It is the infusion of stem cells to replace or repair a patient’s damaged or diseased cells. If successful, the replaced stem cells will integrate into the body and produce more cells that can perform functions specific to the tissue.Current Stem Cell Therapies
Currently, there are only a few conditions for which stem cell therapy is shown to be effective. In patients suffering from cancer, chemotherapy or radiation therapy destroys the healthy cells along with the cancerous cells. Blood-forming or haematopoietic stem cells, when transplanted in patients with lymphoma, leukaemia, and various inherited blood disorders, help in the production of new blood cells. Bone marrow forms a source of these haematopoietic stem cells. Umbilical cord blood can serve as an alternative to bone marrow transplantation.Potential Stem Cell Therapies
Other stem cell transplants, although promising, are still in experimental stages. Some of the conditions which could benefit from stem cell transplant include:
Challenges of Stem Cell Therapy
- Alzheimer’s disease
- Parkinson’s disease
- Type 1 Diabetes
- Various injuries (spinal cord, etc)
- Eye diseases
- Cardiovascular diseases
Although stem cell therapy offers the potential to treat a wide array of diseases, there are several challenges that need to be addressed:
- Identification of stem cells in adult tissues: The process of identifying, isolating, and growing the right kind of stem cells in adult tissues is rather complex and difficult.
- Close match between donor and recipient tissue: Immunological rejection is a major concern in stem cell transplants. Hence, closer the match, lower the risk of rejection.
- Stem cell integration: The success of the transplant depends on its effective integration into the recipient’s body.