Dr. Bill Nordt Discusses the State of Stem Cell Therapy

 In Cartilage, Knee Injuries, orthopedics, stem cells, Uncategorized

 Stem Cell Therapy or OrthoBiologics is in the press a lot today and is creating quite a bit of hype about what these therapies are able to do medically.  We as scientists in medicine are trying to understand the ramifications of stem cell therapy.  We don’t have all the answers yet. In fact, stem cell therapy discussion generally raises more questions than answers. Several years ago I looked at stem cell therapy in a negative light but as more science is emerging, my viewpoint is shifting and stem cell therapy is beginning to have an increasing place in our treatment plans.

Anatomy: What are knee cartilage lesions or articular cartilage lesions?  

Healthy articular cartilage is the smooth, shiny, slippery, gristle surface on the ends of all of the bones that compose your joints. Articular cartilage, the surface of your joints, can be damaged in several ways. One is traumatic, that is you bang or you twist your joint and acutely injure the joint surface.  This can happen when you slip on ice or twist your knee playing tennis. Damage can also come from overuse, which is the repetitive  impact that might occur in a long distance runner.  Lastly, damage can be degenerative, which is the progressive deterioration knee cartilage over time through the aging process.  This typically referred to as arthritis.

Most of us cannot escape articular cartilage damage as we age.  The question is, how do be in the relatively few who do not fall victim to degeneration of articular cartilage?

Lets start with an anatomy and physiology.  A joint is a complex organ system and not a simple structure. For that reason, stem cell research is complicated because of the complex and intricate system of processes that work together to make functioning joint. What are the parts of a joint? As previously discussed, there is the joint surface composed of articular cartilage.  Beneath the cartilage surface is structural bone known as subchondral bone. The synovial lining, the tissue lining your joint, that produces and maintains fluid in your joint. The synovial lining secretes a myriad of mediators, i.e., chemicals and molecules that circulate in the joint to modulate the joint health. The structure that supports the synovial lining is capsule.  The structures that maintain joint stability are the ligaments, or tough elastic bands connecting the bones of the joint.  Lastly, are the muscles and tendons that power joint motion.  We can further subdivide each of the above-mentioned components into many more intricate parts, all of which are vitally important for a joint to function in a healthy and normal manner. 

Articular cartilage is a beautiful and miraculous substance. That surface of your joints is amazing: it has to have the right stiffness, the right resilience, and just the right “bounce.” The surface of your joint must be a frictionless, gliding substance, The coefficient of friction is a measure of slipperiness.   Articular cartilage has an extremely low coefficient of friction.  It is in the top slipperiest substances known to man. And more incredible is that it maintains this low friction over millions of miles of wear.  We can’t reproduce it in the laboratory.   You’ve got this beautiful substance that can just glide so frictionlessly, that can hold up for just years and years—a lifetime!  There is no man made material that can do such a thing.  Incredible stuff, indeed, that Mother Nature has put in our joints. 

Normal Cartilage

 

Degenerative Cartilage

There is, however, a small flaw in mother nature’s design, that is, once cartilage is injured, it doesn’t heal well.  Why?  The surface of such a material that can withstand the loads of a lifetime needs to be dense, with little room for blood vessels.  No blood flow means no healing.  That is the unfortunate problem.  When cartilage does get damaged, its capacity for healing is limited.  Furthermore, when a small area of cartilage does become damaged, the surrounding cartilage can become overloaded, and the area of damage slowly expands.  Healing largely occurs by way of the fluid mediators in the joint.  As the joint does try to heal itself, the progressive edge of deterioration often exceeds the healing.  

Osteoarthritis of the knee

The early stage of cartilage breakdown is called chondromalacia or chondrosis.  The late stage of cartilage damage is called arthritis.  The very end stage is referred to as bone-on-bone osteoarthritis.

Osteoarthritis is the wear and tear of your knee when the gristle surface wears down, sometimes to the raw bone surface.  The osteoarthritic cascade is what scientists call the process of cartilage breakdown. Mechanical fragmentation of the surface occurs. The synovial lining of your joint reacts with inflammation and the release of a litany of mediators–some beneficial and some destructive.  This is a cyclical process that, over time, may end in joint destruction.  The question becomes, how can we control or limit joint destruction and allow you to maintain an active lifestyle.

Normal Knee

 

Arthritic Knee

A typical pattern of knee degeneration is the inner side of the knee wears down to bone on bone.

The question becomes; how can we control or limit joint destruction and allow you to maintain your daily activities?

The first thing that happens in the osteoarthritic cascade is the smooth cartilage surface of the knee wears down. It becomes rough and uneven.  The wear process continues over years until, eventually,  the  underlying bone incurs damage.  Pain from arthritis is variable.  This depends on the amount of inflammation.  Not infrequently, patients that have bone on bone may have no pain whatsoever.  Conversely, we see people who have minor disease that are in terrible pain.  The degree of pain usually corresponds to the degree of inflammation, both of the joint fluid and the bone itself.

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 How can we promote healing of the joint ? 

The basis of nature is that it can heal itself. Inanimate objects can’t heal themselves.  Biological organisms, like ourselves, can heal.  The phases of healing are the same whether you crush your ankle in a snowmobile accident, or you scratch your skin with poison ivy.  Every tissue in the human body goes through three stages of healing: the inflammatory stage, the proliferative stage, and the maturation stage.  This is the process in which the body heals itself, and it is an exceedingly complicated process, with thousands of microscopic reactions.  Cells divide and produce matrix, which is the substance that glues your cells together.  An essential aspect of the healing cascade is the activation of platelets.  Platelets are a component cell in your bloodstream that carry many of the essential growth factors that stimulate healing.

How do we promote the internal environment of knee health and equally the external factors on the joint? 

  • Decreasing your weight can certainly take the tension off your joint.
  • Improving your muscle strength can help act as shock absorbers. 
  • Keeping your knee muscles strong will help maintain a healthy joint surface. 

How do you enhance the healing environment in your joint? 

The thinking today is that OrthoBiologics can promote the healing environment in our joint. To help heal, we want to decrease inflammation. Inflammation is necessary for healing to a degree but if not turned off it becomes destructive. 

How can we improve the chemical environment of the knee?

  • Viscosupplementation, hyaluronic acid, is a lubrication injected into your joints. It basically, makes your joint slipperier. It is a biologic although it can be made synthetically. as well.
  • PRP or platelet rich plasma: We draw blood from your arm and centrifuge it to separate the layers of cells types.. Platelets are cells that contain the healing factors or growth factors in your body. The isolated platelets are injected into the joint.  Generally speaking, 80% of people see some favorable response. PRP is not covered by insurance, and it can be pricey. Some conditions require one treatment and some require up to three treatments. There are favorable studies showing that PRP promotes tissue healing and controls inflammation. As a licensed orthopedic surgeon with the American Academy of Orthopedic Surgeons, AAOS, I have to follow their guidance and for now they don’t recommend or deny the efficacy of PRP.  Therefore PRP is considered experimental. There are patients who see favorable results and those who don’t. 
  • Stem Cells are progenitor cells. These are cells that can turn into anything: they can transform into blood, into bone, to liver, etc. When you’re an infant, your body is surging with stem cells, and slowly as we age we have less and less progenitor cells.  That is why as we age it is harder and harder for us to heal. With the correct signal, a stem cell can turn into muscle, blood, nerve or other tissues. The challenge is to how to deliver that signal. In clinical practice, there are generally three types of stem cells: bone marrow derived stem cells, adipose derived stem cells (from your fat), allogeneic stems—such as those derived from from umbilical cords of newborn babies.  
  • Stem cells and PRP will affect the healing milieu inside the joint.  Will it grow a new cartilage layer? These results are variable.  Stem cells and PRP will not completely regenerate a bone on bone knee back to normal, as pictured in the Xray.  However it is possible that these orthobiologics will promote degrees and healing and pain control, sometimes through immunomodulatation.  Stem cells may affect the nerve cells in your joint and in such a way turn down the amplitude of pain in your joint. 
  • Most studies show that the use of PRP and stem cells will decrease joint pain.  

Conclusion: 

I’m convinced that stem cells are the future although there is still much to learn. It is likely that there is a missing ingredient; stem cells plus an accelerator. We don’t yet have that additional ingredient that will predictably ensure a robust response to stem cell therapy.  Little by little we are getting closer.  In the meantime, strengthen those leg muscles, stay active and maintain a healthy weight and lifestyle.

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knee pain, knee diagnosis