What is Platelet-Rich Plasma (PRP)?
An Advanced Overview for Medical Practitioners
Biological Basis of PRP
Platelet-rich plasma (PRP) is an autologous blood-derived preparation produced at the point of care by centrifuging a patient’s own blood to produce a supraphysiological concentration of platelets suspended in plasma. Platelets contain a range of growth factors, cytokines, and signalling molecules involved in haemostasis, inflammation, angiogenesis, and tissue signalling.
The average baseline platelet count in human peripheral blood is ~200,000 ± 75,000/µL. In whole blood, platelets remain in a quiescent state, with an in vivo half-life of approximately 7–10 days. Upon activation by exposure to collagen, thrombin, or calcium ions, platelets release their intracellular alpha and dense granule contents in a controlled, sequenced manner.
The biological profile of PRP is influenced by multiple variables, including baseline platelet count, platelet recovery efficiency, leukocyte inclusion, and final injectate volume. As a result, PRP is not a single uniform product but a preparation whose composition depends on both patient factors and the preparation system used.
The Phases of PRP-Mediated Healing
PRP accelerates and enhances the body’s intrinsic healing cascade, particularly in poorly vascularised tissues. The three primary overlapping phases are:
1. Inflammation (Days 1–3)
Platelet degranulation triggers clot formation and release of pro-inflammatory cytokines
Neutrophil and macrophage recruitment facilitates debridement and release of further mediators (IL-1β, TNF-α, MCP-1)
Dense granules release ADP, serotonin, and calcium to promote platelet aggregation and vascular constriction
2. Proliferation (Days 3–21)
Proliferation and migration of fibroblasts, endothelial cells, and keratinocytes
Type III collagen deposition
Neoangiogenesis via VEGF, FGF, and TGF-β signalling
Epithelialisation and granulation tissue development
3. Remodelling (Weeks to Months)
Type III collagen is replaced with Type I
Matrix metalloproteinases (MMPs) and tissue inhibitors (TIMPs) regulate ECM turnover
Vascular maturation and functional restoration of tissue
The Importance of Platelet Concentration
The regenerative efficacy of PRP is directly correlated with the dose of functional platelets delivered to the target tissue. Therapeutic PRP must meet or exceed baseline platelet counts to elicit a clinically relevant biological effect.
Alocuro Evidence-Based Targets:
Aesthetic applications: 3–5× baseline concentration
Orthopaedics/MSK: 6–9× baseline
Surgical/wound healing: varies by application and tissue type
However, many commercial PRP kits:
Achieve only ~2× baseline platelet concentration due to plasma dilution
Recover only ~60% of total platelets
Include residual red blood cells and neutrophils, which may exacerbate inflammation