Stem cell therapies are sprouting like weeds. This is a good thing. The medical community is rushing into the biologic sciences, opening up the field of stimulating tissues to heal — rather than suppressing them with steroids, anti-inflammatories or joint replacement surgeries. Here is my take on where the field is now and where it is going …
Adult and amniotic stem cells are growth factor engines. While fetal stem cells can transform into any tissue in the body, the stem cells derived from adult fat, bone and amniotic fluid are potent tissue stimulation factors. Evolution designed these cells to rush to the site of an injury. There, they release a wide variety of cell-modification factors, initiating the repair process. The stem cells instruct surrounding cells to participate in the healing process as well — and then die. When injected into joints or injured tissues, the stem cells generally live for several days, but their effects may last forever.
So how is a patient to choose which cells to use and when? Here, the science is clouded by a large variety of weak studies, confusing information, hype and vast potential. There are loud voices proclaiming that only their version of stem cell and growth factor therapy works.
First, some facts as we understand them today:
When you are in utero, surrounded by the amniotic sac and fluid, you are growing very rapidly as a result of the nutrition provided by the cells of your mother. The reason you are not rejected — despite the fact that half of your cells are foreign to your mother’s body — is because the amniotic tissue produces specialized stem cells. These suppress inflammation and modify the immune system. They are antimicrobial and potently anabolic. You grow quickly, protected by these magical cells and the growth factors they produce.
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Once born, your own stem cells live on the walls of your own blood vessels. They respond to injury, repairing and regenerating your growing tissues, then continue to maintain your health in adult life. When you are young, it is estimated one in 10,000 cells in our bodies are stem cells. As you reach adulthood, this number declines to one in several million.
As a therapeutic source for injured tissues and arthritic knees, adult stem cells and growth factors suppress inflammation and orchestrate tissue repair. These cells can be harvested from your bone marrow, although the number of cells available is small. Only your central bones, such as your pelvis, have any significant amount at all. They can also be harvested from your fat, which, since it is very vascular, has far more cells (though not very many of the fat cells are believed to be true stem cells).
The older you are, the fewer active stem cells you have; your peripheral blood has lots of cells, but not stem cells. However, it does have platelets, which have abundant growth factors within them. These growth factors (in what is called PRP) can be concentrated and injected, though it is doubted they have the wide variety of healing powers possessed by stem cells.
Each of the cell-harvesting techniques has risks and benefits. More pain is associated with bone marrow aspirates, and more soft tissue complications with fat aspirates. The various technologies used to concentrate them all provide varying numbers of cells and growth factors.
It appears the most available, highly concentrated and potent source of stem cells and growth factors is amniotic fluid derived from young, healthy mothers who choose to donate their fluid at the time of a cesarean section. If this fluid is not harvested and processed carefully, however, the stem cells are frequently killed. When harvested correctly, amniotic fluid appears to be the closest thing we have to the mythical “Fountain of Youth.”
This biologic field will hopefully soon be regulated — at least enough to provide standards that allow both doctor and patient to know what, exactly, is in each version of a specific therapy. Only then will we be able to perform comparative testing and move toward product optimization.
The direction of our own research, along with research being done at other clinics, is to identify which injury and arthritis conditions have which joint biochemical profiles. An injured knee with a torn ACL, for instance, would have a very different joint fluid chemical profile from an arthritic knee — and each person may have a unique anabolic and degradative enzyme pattern in their joint fluid that should be specifically treated.
In an Institutional Review Board-approved research study focused on patients with joint pain, we are taking fluid from all of such joints, before and after joint injection, to identify these patterns and assess how each condition responds to each of four biologic therapies.
Today, clinicians are injecting everything they believe to be helpful. Tomorrow, we will have custom, personalized profiles of each joint condition and targeted therapeutic injections. Maybe then, the myth and the reality of stem cell therapy will merge. For now, though, there appear to be few downsides to anabolic therapies — other than their cost and uncertainty. Given the “do no harm” imperative of medicine, it is quite rare to have so potent a treatment with so little risk.
Dr. Kevin R. Stone is an orthopedic surgeon at The Stone Clinic and chairman of the Stone Research Foundation in San Francisco.