What is the Composition of Platelet-Rich Plasma (PRP)?
PRP is a biologic isolated from whole blood that is preferentially enriched for platelets. While platelets are the primary component of PRP, preparations may also contain other cellular components such as white blood cells (WBCs) and peripheral stem cells. These components all play a biological role in the healing process and are provided at concentrated levels in PRP. Thus, PRP may help optimize the conditions for healing of bone and soft tissue.
Platelets play a critical role in several aspects of the healing process. Activated platelets release adhesion molecules that support clot formation for hemostasis. They also release several antimicrobial peptides that deliver infection control properties. Most importantly, as it relates to healing, platelets also release numerous growth factors, including PDGF, TGF-β, VEGF, and SDF-1α30,33 that have been shown to orchestrate the key biological processes, including angiogenesis, inflammation resolution and tissue regeneration.
WBCs (or leukocytes) play a key role in protecting the body from infection and coordinating the inflammatory response. The three primary classes of cells found in the WBC population each provide unique biological functionalities:
GRANULOCYTES (OR NEUTROPHILS)
- The “immediate response” cells for prevention of infection
- Key mediators of inflammatory response through phagocytosis and release of reactive oxygen species (ROS)
- T-lymphocytes help regulate the function of other immune cells and directly attack various infected cells and tumors
- B-lymphocytes make antibodies, which are proteins that target unwanted bacteria, viruses and other foreign materials
- Assist in pathogen recognition
- Eventually become macrophages, which engulf and destroy pathogens
The illustration below shows how WBCs travel through the body to address inflammatory conditions.
NONSPECIFIC INFLAMMATORY RESPONSE
Stem cells are at the core of the tissue regeneration process. They are required to rebuild and repair damaged tissue at an injury site.6 Platelets release several growth factors, such as SDF-1α, that function to induce migration of stem cells to the damaged tissue during the healing process. PRP provides these growth factors in high concentrations. In addition, some PRP preparations also contain stem cells isolated directly from the blood sample during processing, which can directly support tissue regeneration.
The concept behind the clinical use of PRP is to harness the natural biological components of a patient’s blood―primarily platelets―which may help optimize the conditions for healing, improve inflammatory response, control infection and promote angiogenesis.13,17,18
Compared with other biologics, such as concentrated BMA and adipose tissue, PRP possesses higher concentrations of platelets. Platelets facilitate healing through release of many growth factors actively involved in this process. Thus, PRP offers the physician an alternative to widespread treatments, such as steroid injections. Such treatments provide short-term relief by masking symptoms such as pain and inflammation that are the result of an injury, rather than actually addressing the cause of the injury directly through repair of damaged tissue.42,43
This chart compares the impact of PRP versus corticosteroid treatment on the pain levels of patients post-procedure. Although results may vary, the benefit of corticosteroid treatment was lost over time, while PRP generated continued improvement even two years after the procedure.42