Abstract: Platelet concentrates such as platelet-rich plasma (PRP) have gained popularity in sports
medicine and orthopaedics to promote accelerated physiologic healing and return to function. Each
PRP product varies depending on patient factors and the system used to generate it. Blood from some
patients may fail to make PRP, and most clinicians use PRP without performing cell counts on either
the blood or the preparation to confirm that the solution is truly PRP. Components in this milieu have
bioactive functions that affect musculoskeletal tissue regeneration and healing. Platelets are activated by collagen or other molecules and release growth factors from alpha granules. Additional substances are released from dense bodies and lysosomes. Soluble proteins also present in PRP function in hemostasis, whereas others serve as biomarkers of musculoskeletal injury. Electrolytes and soluble
plasma hormones are required for cellular signaling and regulation. Leukocytes and erythrocytes are
present in PRP and function in inflammation, immunity, and additional cellular signaling pathways.
This article supports the emerging paradigm that more than just platelets are playing a role in clinical responses to PRP. Depending on the specific constituents of a PRP preparation, the clinical use can theoretically be matched to the pathology being treated in an effort to improve clinical efficacy.