The Great Stem Cell Divide

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.

The Great Stem Cell Divide The Stone Clinic

Adult and amniotic stem cells are growth factor engines. While fetal stem cells can transform into any tissue in the body, the progenitor cells derived from adult fat, bone, and amniotic tissues 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-cell-derived progenitor cells instruct surrounding cells to participate in the healing process as well—and then die. When injected into joints or injured tissues, the 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.

Once born, your own stem cells live on the walls of your own blood vessels and within various tissues. They respond to injury by producing daughter cells called progenitor cells which direct the repair and regeneration of your growing tissues, then continue to maintain your health in adult life. When you are young, it is estimated 1 in 10,000 cells in our bodies are stem cells. As you reach adulthood, this number declines to 1 in several million.

As a therapeutic source for injured tissues and arthritic knees, adult stem-cell-derived 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.

The older you are, the fewer 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.

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.

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 IRB (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.


Medically authored by
Kevin R. Stone, MD
Orthopaedic surgeon, clinician, scientist, inventor, and founder of multiple companies. Dr. Stone was trained at Harvard University in internal medicine and orthopaedic surgery and at Stanford University in general surgery.