Once confined to science fiction, biologic therapies now harness growth factors and cellular signaling to reduce inflammation, restore function, and support natural healing.
By Dr. Edwin E. Spencer | Illustration prompted by Chelsie Hall
Appeared in Cityview Magazine, Vol. 42, Issue 2 (March/April 2026)
Do you remember Luke Skywalker being submerged in a Bacta tank in The Empire Strikes Back? Star Wars enthusiasts will. In the Star Wars series, patients could get immersed in the slimy fluid, and they could be healed from most any problem. Although technology in medicine is increasing at an exponential rate, we have not been able to create a Bacta tank. However, the field of biologics is heading in that direction by harnessing the body’s innate ability to heal.
Simply put, biologics are naturally occurring substances or processes that can stimulate the ability to heal. Examples in orthopaedics include platelet rich plasma (PRP) or bone marrow aspirate concentrate (BMAC). So, what exactly is PRP and how does it work?
Our blood is composed of many different elements that include red blood cells that carry oxygen, white blood cells that fight infection, and platelets. For a long time, we believed that platelets (which are fragments of a larger cell called a megakaryocyte) were only involved with clotting. You get a cut on your body, and the platelets come to the rescue to create a clot to prevent you from bleeding out. As it turns out, platelets do so much more. Platelets have granules inside them that house a plethora of growth factors. When these platelets arrive at the site of injury, these granules are released into the local environment, and the growth factors are distributed to do the work.
This is when the magic of healing begins. The growth factors act as small chemical signals that recruit and direct the action of other cells. Some growth factors recruit inflammatory cells while others signal to make blood vessels while still others stimulate fibroblasts to make a scaffold upon which to heal. It is a highly organized process that proceeds from inflammation to proliferation to remodeling. If this happens in such a predictable and consistent fashion, then why do we need to augment it? Why do we need to aid the body to heal with biologics?
Healing requires blood flow. Think of healing as a battle. The blood flow is the supply line feeding the army fighting the battle. If the supply line is deficient, then the front line cannot receive the supplies and win the battle. Tendons, ligaments and joints are privy to a limited blood supply. A tendon receives blood from the bone to which it is attached and the muscle on the other side. A ligament receives blood from the bones that it stabilizes. While joint cartilage receives nutrients from the synovial fluid and the underlying bone, there are very few vessels within each tendon and ligament. This makes blood supply and nutrients to tendons, ligaments and cartilage very tenuous. If the blood supply is deficient, then the ability to heal will be reduced.
This reduced blood flow is thought to be a reason for “chronic” tendon, ligament, and cartilage injuries. Have you ever been told that your injury is from old age or chronic? Imagine if you sustain a small injury that tears some of the fibers of a tendon, yet not enough to cause significant bleeding. Without ample blood and nutrients, this small tear will have a hard time
healing. Imagine this process happening repeatedly. Eventually, the tear enlarges until it becomes symptomatic. How can we aid the body to heal this tear? Biologics.
Biologics like PRP increase the normal number of platelets at a site of injury. The number of platelets can be increased by 4-10 times the normal amount. This in turn increases the number of growth factors that induce new vessels to form and a healing scaffold to be created.
I became very interested in this biologic space, especially for the treatment of partial tendon or ligament tears. Although these tears were partial thickness (the entire tendon was not pulled off the bone), they were still painful. Ask anyone with a partial thickness rotator cuff tear or tennis elbow and they will agree. It seemed, however, that there might be a better way to treat these partial tears other than surgical repair. Now we needed to test the hypothesis.
We chose a particular type of partial rotator cuff tear to evaluate that we thought would be amenable. One group in the study underwent surgical repair, and the other group was treated with an ultrasound-guided PRP injection into the tear site. While both groups performed equally well regarding pain relief and function, the PRP group recovered faster. This study was published in 2023. Based on these data, we expanded the use of PRP to other tendon and ligament tears with equally good success.
Let’s explore stem cells a bit. Stem cells are also a biologic that has received significant press. A stem cell is a cell that can differentiate into other cell types. There are different types of stem cells. Mesenchymal stem cells can differentiate into tendon, bone, or cartilage; while hematopoietic stem cells can differentiate into blood elements like red and white blood cells. We are blessed with stem cells all over our body to help us heal from damage.
In orthopaedics we have used stem cells harvested from bone marrow and fat to mainly treat arthritis. To call these stem cells might be a stretch, however. Yes, we can harvest stem cells in the US, but they cannot be expanded in culture to get them to the levels that have proven significant efficacy. Outside the US, stem cells can be harvested and expanded for 3-4 weeks and then given back to the patient. Here in the US, the harvested stem cells can be centrifuged or mechanically separated but not enzymatically processed. The FDA considers the stem cells to be a drug if they are manipulated more than just mechanically, and it is illegal. Stem cells harvested from the bone marrow are best termed bone marrow aspirate (BMA) and if centrifuged, bone marrow aspirate concentrate (BMAC), since they are not expanded in culture.
There are also allogenic (not from the patient) stem cells from umbilical cord, placenta, or Wharton’s Jelly, which are also not approved by the FDA. The theoretical benefit of these early stem cell lines is that they have a greater ability to differentiate into any cell line.
However, there is the possibility of a reaction to a foreign substance and transmission of any genetic disease from the original donor source to consider.
Another point to make about stem cells is that while we originally thought that it was the stem cells that actually made the new tissue, that doesn’t seem to be the case. The stem cells themselves have been shown to congregate at the site of damage. However, the stem cells seem
to have their effect through signaling other cells to do the work. Therefore, the name medicinal signaling cell is preferred to mesenchymal stem cell, although they share the same acronym.
The most potent effect of the stem cells seems to be a marked reduction in inflammation in the joint and thus a reduction in pain. As it turns out, that is exactly what patients desire. To believe that stem cells will create new cartilage in an arthritic joint is a stretch. This has been promulgated in the media and is where the media can get out over their skis. It is more realistic to think you may get a reduction in inflammation and pain for a certain time period. Most studies have shown much longer pain relief with biologics compared to cortisone, which is toxic to cartilage cells.
There is ongoing research in the US and outside the US demonstrating cartilage growth on biologic scaffolds. The future is promising, but we need to have realistic expectations of what we can accomplish with biologics today.
I think that we are able to get some tendons and ligaments to heal with PRP. This technology has been used and evaluated enough that we are dialing in on the specific types of PRP preparations that are best for tendon/ligament use and those for joint use. We are also starting to better understand the specific elements and molecules that are most important in healing and inflammation reduction.
We are not quite at the Bacta tank level yet, but great strides are being made. What intrigues me most is that this is not a drug. Rather, we are harnessing the body’s own ability to heal. With a better understanding of the biology, we can help people heal themselves. Isn’t that what we all want?
Comments are closed.