What is a Stem Cell? Part 2
Stem Cells for Orthopedic injuries
Last time we introduced the concept of multipotent or “adult stem cells” as the ones we use to treat orthopedic injuries. There is a more specific name for these, coined by Dr. Arnold Caplan in 1991 “Mesenchymal Stem Cells” or MSCs for short. Then, in 2017 Dr. Caplan chose to label these cells “Medicinal signaling cells” to further describe their actions. He states that this name “more accurately reflects the fact that these cells home in on sites of injury or disease and secrete bioactive factors that are immunomodulatory and trophic (regenerative) meaning that these cells make therapeutic drugs in the body that are medicinal. It is, indeed, the patient’s own site-specific and tissue-specific resident stem cells that construct the new tissue as stimulated by the bioactive factors secreted by the exogenously supplied MSCs.”
Why would we use MSCs for Orthopedics? MSCs help contruct the types of tissue we are interested in – bone, cartilage, fat, muscle, connective tissue, and blood vessels. This works out great because not only are they available for us to get in an adult, but they are targeted for the exact type of injuries and causes of pain that we are most often trying to treat.
Bone vs. Fat Harvest
Where should we get them? This debate is ongoing, but we know they exist in the highest numbers in bone marrow and fat. Some people argue that we should take these cells from fat, but most of them are located in a special part of the fat called the SVF (stromal vascular fraction). The only problem is: we cannot get to this part of the fat unless we change or alter the fat using a chemical to digest it. Because of this, the FDA does not allow us to use this source in the US unless it is through a clinical trial.
We know the MSC’s make up only 0.001% to 0.01% of the cells in the bone marrow, but we know most of them live in the back of the hip bone. So how do we get enough of them? After numbing a patient so they do not feel any pain, we take these cells from the back of the hip bone (posterior iliac crest) and put them in a special machine (centrifuge) that spins at incredibly fast speeds. This separates out the cells we don’t want and packs the good cells that we do into a layer in the middle of the tube.
Risks of Complications with BMAC
These cells can then be injected in a sterile fashion so that patients have minimal risk of infection. We use either a sound wave probe (ultrasound) or an X-ray to very precisely guide them back into the area of disease. Amazingly, there is less than 1% risk of complication from large scale studies with this method of taking cells from the bone marrow. We call this method Bone Marrow Aspirate Concentrate or BMAC for short. Stay tuned for Part 3 where we will discuss how these cells actually work.