Stem Cells, Repair Cells, & Growth Factors: What is the Latest?
Stem cells, once seen as pluripotent cells that were going to cure all diseases, are having a recession. The science is revealing that, as is almost always the case, the story is more complicated than a “super cell” coming to the rescue. Here is an update.
Yes, stem cells exist. Yes, they are the origin of all the other cells in the body and, in a few cases (particularly in the eye), have successfully cured specific diseases. In most other cases, it’s the products of those cells that have been the best effectors of healing. At injury, when tissues have been torn or crushed, signaling factors are released from the cells within them.
Think of grapes at harvest, crushed into juice. The aroma of the crush, the fluid that is expressed, even the sound of the presses—all elicit a sensory response in the winemaker. This causes their lips to moisten, their noses to flare, and their mind to become excited at the anticipation of that year’s wine.
A similar thing happens within your body when an injury occurs (but without the pleasure). Here, the injury elicits a healing response. The signals that stimulate this response are produced primarily from proteins called cytokines, which are released from broken blood vessels at the site injury. Other stimulants include fluid that was once inside the cells of the tissues—but is now in the extracellular space, causing swelling and bruising—and messages sent by nerve fibers that, when injured, signal the brain to start an additional cascade of healing responses.
A major part of this healing response is directed by self-repair cells—think of them as the “sons and daughters” of stem cells. They rush to the site of injury, directing the next stages of healing. A subset of cells called M1 macrophages removes dead tissue, while M2 macrophages suppress inflammation and help the remaining healthy cells lay down new collagen during the rebuilding process.
What this means for the clinician caring for an injured patient is that there are many ways to interact with, and even accelerate, the healing response. The most potent tools we have are growth factors from either the patient’s own blood components (called platelets) or from birth tissues and amniotic fluid that surround a growing fetus. These birth products are donated at the time of C-section from healthy mothers then provided by tissue banks for use in the clinic.
Our research, and that of others, has shown that these factors can directly affect the chemistry of injured tissues or arthritic joints and generate a much more robust call for self-repair cells. Simply put, we can insert the signaling factors that direct healing more effectively than we can harvest cells. And since the human body has billions of stem cells, self-repair cells, and other injury response systems, it makes more sense to inject factors that recruit and stimulate these healing cells than to try to inject “stem” cells harvested from fat or bone.
Today’s injections are mixtures of the strongest growth factors and cytokines. Our goal is to shorten the healing time of any injury. We then let the patient’s body make the wine.