What are Platelets?

Platelet Rich Plasma (PRP) is a concentrated source of platelets in blood plasma which contains several growth factors and cytokines that can stimulate healing of soft tissue and joints.
Main indication in sports medicine and orthopedics are acute muscle strains, tendinopathy, ligament injuries and osteoarthritis.
Main indications in dermatology for PRP are androgenic alopecia, wound healing, and skin rejuvenation.
For preparation of PRP, various protocols are used, with an underlying principle of concentrating platelets to 3–5 times physiological levels, then injecting this concentrate in the tissue where healing is desired.

PRP has several potential therapeutic effects.

PRP may reduce inflammation by inhibition of TGF-beta.
Growth factors secreted by platelets can improve tissue micro environment by formation of new blood vessels.
Platelets may directly interact with the T lymphocytes and modulate the immune system.
Finally, PRP can accelerate healing and promote tissue regeneration by promoting growth and proliferation of the endogenous progenitor cells.

Key Steps of Platelet Activation

Shape Change: Cytoskeletal remodeling transforms the flat platelet into a sphere with extended filopodia. This geometric shift maximizes its surface area to interact with other cells.
Granule Secretion: Platelets empty internal storage units (alpha and dense granules). This releases potent chemical signaling molecules, including Adenosine Diphosphate (ADP), serotonin, and newly generated thromboxane A2.
Positive Feedback Loop: The released chemicals bind to neighboring resting platelets. This rapidly recruits more cells to the injury zone to amplify the response.