Stem cell therapies – you’ve no doubt heard of them and their use in today’s medical science. Is it hype or do they really work?
What are stem cells?
Stem cells are the basic cells of an organism from which all other specialized cells are created. (These specialized cells are called daughter cells.)
Embryonic v. adult stem cells
There are two types of stem cells, embryonic stem cells and adult stem cells. Embryonic stem cells come from embryos that are three to five days old. They are versatile and can divide into any type of cell. Adult stem cells are found in adult tissues, such as bone marrow or fat.
How do stem cells work?
Stem cells give rise to specialized cells by a process called differentiation. In order for this to happen, the cells must receive an internal or external signal. Internal signals are given from the cells’ genes, as printed on long strands of DNA. External signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the cells’ microenvironment. It has generally been accepted that adult stem cells cannot change themselves into other types of cells. For example, a blood-forming cell in the bone marrow, called a hematopoietic stem cell, cannot give rise to cells of very different tissue, such as nerve cells in the brain. However, experiments over the last several years have purported to show that stem cells from one tissue may in fact be able to give rise to cell types of a completely different tissue. This remains an area of great debate within the research community.
Medical use of stem cells
Stem cells are used medically to generate healthy cells to replace diseased cells (regenerative medicine). New drugs are being tested for safety and effectiveness.
Use of stem cells in orthopedics
In orthopedics, we are interested in discovering the factors that stimulate stem cells to relocate to sites of injury or damage, and how this process can be enhanced for better healing.
The reason stem cells are particularly beneficial in osteoarthritis treatment is because cartilage cells cannot regenerate. Once the smooth articular cartilage that protects the ends of the joints is damaged, it cannot heal itself. Instead, the injury begins a chain of events that leads to more cartilage loss, in a process called apoptosis, where the surrounding cartilage cells die. In the same way as a tiny piece of paint chipped off some furniture gradually becomes bigger, there is a constant loss of cartilage throughout that region, which over time, results in the loss of cartilage in all parts of the joint.
If this process can be changed and the damaged cartilage cover rebuilt, the progress of wear and tear can be reduced drastically.
Stem cell paste graft
To promote cartilage regrowth, we must target stem cells into the damaged area.
For osteoarthritis of the knee, the stem cells are best taken from the same area of the body, such as bone marrow from the femoral notch inside the knee, so that they have both the internal and external signals for regrowth and differentiation. When the cells are combined with a favorable healing environment, such as a paste of cartilage and bone, they are able to form new cartilage, repairing the arthritic area. A technique called an articular cartilage paste graft, is one of several techniques designed to repair cartilage and solve the arthritis problem. A paste, including the stem cells from the patient’s own bone marrow, is packed into the arthritic defect. The stem cells recruit other cells for healing and then differentiate into specified hyaline cartilage cells instead of fibrous cartilage.
Growth Factors and Stem Cells
Additionally, blood stem cells (haemapoetic stem cells) can be recruited by using injections of specific factors found in substances such as Platelet Rich Plasma, (PRP), the growth factors released from blood platelets. For the management of knee injuries pre and post arthritis we inject the growth factors, which cause the release of stem cells from their resting places on vascular walls, and stimulate a healing environment.
Harnessing the body’s own natural healing process is most promising area of orthopedics today and will become ever more influential in the future of medicine.