Platelet-rich plasma (PRP) is a regenerative therapy that harnesses the body’s natural healing mechanisms to treat various injuries and conditions. It is a biological product created from a patient’s own blood, which is then concentrated and reintroduced to the site of injury. This method relies on isolating specific components of the blood to deliver bioactive proteins directly to damaged tissue. The goal of using PRP is to stimulate a localized healing cascade, promoting cellular repair and tissue regeneration. This autologous approach minimizes the risk of rejection or disease transmission, making it a well-tolerated procedure.
Defining Platelet-Rich Plasma
Platelet-rich plasma is defined as a volume of plasma that contains a platelet concentration significantly above the patient’s baseline whole blood concentration. Normal platelet counts range from 150,000 to 450,000 platelets per microliter, but effective PRP typically aims for a concentration of at least five to ten times this level. Platelets are known for their role in blood clotting, but they also serve as reservoirs for hundreds of signaling proteins stored within their alpha-granules.
When activated, platelets release a complex mixture of these proteins, including various growth factors that initiate and regulate the healing process. These concentrated factors are the biological agents responsible for the therapeutic effects of PRP. Examples include Platelet-Derived Growth Factor (PDGF), Transforming Growth Factor-beta (TGF-beta), and Vascular Endothelial Growth Factor (VEGF). The final composition, including the presence of white blood cells, can vary depending on the preparation method used.
The Preparation Process
The creation of platelet-rich plasma begins with a venipuncture, where a small volume of the patient’s whole blood is drawn. This blood is immediately collected into specialized tubes containing an anticoagulant, such as acid citrate dextrose (ACD-A), to prevent premature clotting. The collected sample is then placed into a centrifuge machine for processing.
The preparation involves a two-step differential centrifugation process to separate blood components based on their densities. The first, slower spin (often 100 to 300g), separates the heavier red blood cells from the plasma and the platelet-rich buffy coat layer. The plasma layer, which contains the platelets, is then transferred to a new tube, leaving the red blood cells behind.
A second, faster spin (commonly 400 to 750g) is performed on this plasma sample to pellet the platelets at the bottom of the tube. The majority of the platelet-poor plasma (PPP) is then removed. The concentrated platelets are resuspended in the remaining small volume of plasma, resulting in the final Platelet-Rich Plasma product, ready for injection.
Mechanisms of Healing
Once injected into an injured area, the concentrated platelets become activated, leading to the rapid release of their stored growth factors. This surge of bioactive molecules initiates the cascade of tissue repair by stimulating local cell populations. Platelet-Derived Growth Factor (PDGF) and Transforming Growth Factor-beta (TGF-beta) are important, promoting the migration and proliferation of stem cells and fibroblasts to the site.
Fibroblasts are prompted to synthesize new collagen and extracellular matrix components, which are the structural building blocks for new tissue. Vascular Endothelial Growth Factor (VEGF) stimulates angiogenesis, the formation of new blood vessels, improving blood supply and nutrient delivery. This complex cellular signaling environment works to replace damaged tissue with healthy, regenerated cells.
Common Medical Applications
Platelet-rich plasma is widely utilized across several fields, with orthopedic medicine being the most common application. It is employed to treat chronic tendinopathies, such as elbow tendinosis and Achilles tendinopathy, and to address ligament sprains. In these musculoskeletal applications, the goal is to promote the healing of tissues that have limited capacity for self-repair due to poor blood supply.
PRP has also found uses in aesthetic medicine, notably for skin rejuvenation and hair restoration treatments. For hair loss treatment, the concentrated growth factors are injected into the scalp to stimulate dormant hair follicles and prolong the hair growth phase. However, the therapeutic success of PRP can be variable across different conditions and patient populations.
Regulatory bodies often classify PRP preparation systems as medical devices cleared for use in blood processing. However, the clinical application of the final PRP product for most indications (such as treating a torn tendon or hair loss) is frequently considered an “off-label” use. This distinction exists because the product is derived from the patient’s own body, exempting it from the traditional drug approval process. The scientific consensus on its efficacy continues to evolve with ongoing research.