Biologic healing works like a football team. When all the players fill their roles at the right times, when the indefinable chemistry is right, when the coaching provides encouragement at just the right times and when the preparation and fitness are ideal, winning — or healing — occurs.
Without all of these facets in place, random events sometimes lead to victory — or to disorganized failures.
Injuries are like spontaneous game times. The injury occurs, and the call goes out to the team: Jump into action!
Multiple events occur simultaneously at the moment of injury. The cells of the injured tissues leak their contents into the surrounding tissues. These materials are chemotactic: This means they call other cells and blood factors to the site of healing. First, they clean up and carry away the damaged tissues. Then, they lay down new collagen, the backbone of all tissues in the body. Next, nerve endings in the tissues send signals to the brain recording both the pain and the site of the injury. This provides directional information, protecting the injury with limping, muscle contraction or natural splinting of the area.
A sequence of healing usually characterized by inflammation, tissue remodeling and (eventually) scar formation follows. The quality of the healing depends on the guidance and coaching of rehabilitation and exercise, along with physical, chemical and hormonal influences.
All of these sequences occur successfully only if all the components are working. The creation of life on Earth required an all-star team of all the right chemical, biological and physical players, along with and energy from the sun (and coaching?) to create and stimulate living organisms. The recreation of healthy tissues is the same.
But plenty of things can go wrong.
If the body is low on red cells (a condition called anemia), the healing is sometimes poor, due to the low delivery of oxygen to the injury site. If the injured person is depressed, endorphins may not be released in the right combination to stimulate a healthy tissue response.
The point is, healing occurs due to the collection of all the players on the team. Only when all members are present and ready does the natural healing response work ideally.
This brings us to stem cells. Much is written in the press, and millions of dollars are being spent on stem cell injections for every injury. Yet only a very few, truly effective outcomes from stem cell injections alone have been documented — and most are in the eye. Those that have been documented in joints have occurred only when the tissues are already in the repair process, or can be stimulated to start healing. In this case, stem cells are used to assist (and possibly accelerate) healing.
The reason for the failures is the lack of the team. A stem cell is a growth factor engine, called to the site of injury to release growth factors that stimulate or augment the repair process. When an injury site has all the other factors necessary for repair to occur, the stem cell can encourage the process.
But when injected alone — especially into sites that do not have the healing stimulus, such as an arthritic joint — they have little chance of being effective. To address this deficit, we add combinations of factors to injections and use amniotic stem cells, with their native regenerative ability, to induce a healing response.
The stem cell is like a star football quarterback. Without a strong offensive line in front of him and a talented receiver, without momentum and coaching, his team often fails to win. The biology of healing is no different: The successful biologic therapies of today combine stem cells with other techniques and implants to create a complete healing environment.
The lesson? Beware of the solitary Heisman Trophy winner. Bet on the All-Star team.
Dr. Kevin R. Stone is an orthopedic surgeon at The Stone Clinic and chairman of the Stone Research Foundation in San Francisco.