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 of 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