“Red Blood Cells, Neutrophils and Platelets – A closer look at cell types and how they affect PRP treatments”
Blood is arguably the most important life sustaining component of the body. For our companion animals, blood comprises on average 7% of the dog’s body weight and carries out several critical functions including transportation of oxygen and nutrients to the cells, removal of waste products and healing of damaged tissues. Each component of blood is responsible for a specific function to maintain homeostasis. Red Blood Cells (RBCs) transport oxygen and carbon dioxide between tissues and lungs. White Blood Cells (WBCs), including neutrophils, eosinophils, basophils, lymphocytes and monocytes, function as part of the body’s defense mechanism to fight off infections and disease. Platelets, as we have learned from our previous blogs, are important for their clotting abilities as well as their growth factors for tissue repair and healing. Last but not least, plasma, which is the fluid portion of blood, is responsible for transporting the above cell types along with delivering important proteins and other dissolved nutrients to various tissues of the body.
Although each cell type has a specific and beneficial function in the circulating blood, their inclusion in the PRP sample can be detrimental to the tissue it is being used to treat. RBCs make up approximately 45% of the blood’s volume. Although they are important for the exchange of gas substances in tissues when circulating, they can also be damaging to cartilage and synovium. When RBC’s are exposed directly to any tissue without the barrier provided by a vessel, they produce harmful Reactive Oxygen Species and also increase the concentration of unwanted inflammatory mediators including IL-1 and TGF-α. Injection of RBC’s directly into a tissue would result in further tissue damage and could lead to increased pain for the patient. In short, we want to effectively exclude RBCs from our PRP sample to reduce the possibility of damaging the tissue and negating the positive effects of the PRP.
Neutrophils, which are the most abundant WBC, are the first line of defense against invading microorganisms. Typically observed in the early stages of infection, neutrophils have the ability to kill microorganisms immediately and non-specifically, without having a “learned” immune response. Although this is beneficial for the control of infections, neutrophils are detrimental to cartilage and synovium as observed in autoimmune diseases including Rheumatoid Arthritis and common tick-borne diseases including Lyme Disease. Neutrophils increase the concentrations of unwanted inflammatory mediators which include IL-1β, TNF-α, IL-6 and IL-8. It has also been observed that neutrophils, when included in a PRP sample, correlate with an increased concentration of MMP-9 which degrades collagen and other extracellular material. We can reason with this knowledge that neutrophils should also not be included in our final PRP sample due to their harmful effects on the tissue.
So what about the other White Blood Cell types? The jury is still out on whether there is an ideal concentration for monocytes, lymphocytes and the other cell types. Their elimination or inclusion is still under investigation and as regenerative medicine continues to evolve, our knowledge and understanding of what the “perfect” PRP sample will become clearer. What we do understand from our current knowledge of these cells and how they function is that in an ideal PRP sample, we want a higher concentration of platelets for their beneficial growth factors and we want a reduced number of RBC’s and neutrophils. For more information about the Companion Regenerative Therapies (CRT) System or to learn more about PRP therapy, please click here.
Stay tuned for our next blog where we look at the 5 most important things every vet should know about regenerative medicine!
