Platelet-rich plasma (Abbreviation: PRP) is blood plasma that has been enriched with platelets. As a concentrated source of autologous platelets, PRP contains (and releases through degranulation) several different growth factors and other cytokines that stimulate healing of bone and soft tissue.
The efficacy of certain growth factors in healing various injuries and the concentrations of these growth factors found within PRP are the theoretical basis for the use of PRP in tissue repair. The platelets collected in PRP are activated by the addition of thrombin and calcium chloride, which induces the release of these factors from alpha granules. The growth factors and other cytokines present in PRP include:
- platelet-derived growth factor
- transforming growth factor beta
- fibroblast growth factor
- insulin-like growth factor 1
- insulin-like growth factor 2
- vascular endothelial growth factor
- epidermal growth factor
- Interleukin 8
- keratinocyte growth factor
- connective tissue growth factor
There are, at present, two methods of PRP preparation approved by the U.S. Food and Drug Administration. Both processes involve the collection of whole blood (that is anticoagulated with citrate dextrose) before undergoing two stages of centrifugation (TruPRP) (Harvest) designed to separate the PRP aliquot from platelet-poor plasma and red blood cells. In humans, the typical baseline blood platelet count is approximately 200,000 per µL; therapeutic PRP concentrates the platelets by roughly five-fold. There is however broad variability in the production of PRP by various concentrating equipment and techniques.
In humans, PRP has been investigated and used as clinical tool for several types of medical treatments, including nerve injury, tendinitis, osteoarthritis, cardiac muscle injury, bone repair and regeneration, plastic surgery, and oral surgery. PRP has also received attention in the popular media as a result of its use in treating sports injuries in professional athletes.
The use and clinical validation of PRP is still in the early stages. Results of basic science and preclinical trials have not yet been confirmed in large-scale controlled clinical trials. For example, clinical use of PRP for nerve injury and sports medicine has produced "promising" but "inconsistent" results in early trials. A 2009 systematic review of the scientific literature stated that there are few controlled clinical trials that have adequately evaluated the safety and efficacy of PRP treatments and concluded that PRP is "a promising, but not proven, treatment option for joint, tendon, ligament, and muscle injuries".
Proponents of PRP therapy argue that negative clinical results are associated with poor quality PRP produced by inadequate single spin devices. The fact that most gathering devices capture a percentage of a given thrombocyte count is a bias, since there is significant inter-individual variability in the platelet concentration of human plasma. More is not necessarily better in this case. The variability in platelet concentrating techniques may alter platelet degranulation characteristics that could affect clinical outcomes.
Implications for doping
Some concern exists as to whether PRP treatments violate anti-doping rules, such as those maintained by the World Anti-Doping Agency. It is not clear if local injections of PRP can have a systemic impact on circulating cytokine levels, in turn affecting doping tests; it is also not clear whether PRP treatments have systemic anabolic effects or affect performance. In January 2011, the World Anti-Doping Agency removed intramuscular injections of PRP from its prohibitions after determining that there is a "lack of any current evidence concerning the use of these methods for purposes of performance enhancement".
- Borrione P, Gianfrancesco AD, Pereira MT, Pigozzi F (2010). "Platelet-rich plasma in muscle healing". Am J Phys Med Rehabil 89 (10): 854–61. doi:10.1097/PHM.0b013e3181f1c1c7. PMID 20855985.
- Yu W, Wang J, Yin J (2011). "Platelet-Rich Plasma: A Promising Product for Treatment of Peripheral Nerve Regeneration After Nerve Injury". Int J Neurosci 121 (4): 176–180. doi:10.3109/00207454.2010.544432. PMID 21244302.
- Arora NS, Ramanayake T, Ren YF, Romanos GE (2009). "Platelet-rich plasma: a literature review". Implant Dent 18 (4): 303–10. doi:10.1097/ID.0b013e31819e8ec6. PMID 19667818.
- Marx RE (2004). "Platelet-rich plasma: evidence to support its use". Journal of Oral and Maxillofacial Surgery 62 (4): 489–96. doi:10.1016/j.joms.2003.12.003. PMID 15085519.
- Dohan Ehrenfest DM, Rasmusson L, Albrektsson T (2009). "Classification of platelet concentrates: from pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF)". Trends in Biotechnology 27 (3): 158–67. doi:10.1016/j.tibtech.2008.11.009. PMID 19187989.
- Gonshor A (2002). "Technique for producing platelet-rich plasma and platelet concentrate: background and process". The International Journal of Periodontics & Restorative Dentistry 22 (6): 547–57. PMID 12516826.
- Weibrich G, Kleis WK, Hafner G, Hitzler WE, Wagner W (2003). "Comparison of platelet, leukocyte, and growth factor levels in point-of-care platelet-enriched plasma, prepared using a modified Curasan kit, with preparations received from a local blood bank". Clinical Oral Implants Research 14 (3): 357–62. doi:10.1034/j.1600-0501.2003.00810.x. PMID 12755786.
- Mishra A, Pavelko T (2006). "Treatment of chronic elbow tendinosis with buffered platelet-rich plasma". The American Journal of Sports Medicine 34 (11): 1774–8. doi:10.1177/0363546506288850. PMID 16735582.
- Mishra A, Woodall J, Vieira A (2009). "Treatment of tendon and muscle using platelet-rich plasma". Clinics in Sports Medicine 28 (1): 113–25. doi:10.1016/j.csm.2008.08.007. PMID 19064169.
- Andia I, Sanchez M, Maffulli N (2012). "joint pathology and platelet-rich plasma therapies". Expert Opinion in Biological Therapies 12 (1): 7–22. doi:10.1517/14712598.2012.632765. PMID 22171664.
- Mishra A, Velotta J, Brinton TJ, et al. (2010). "RevaTen platelet-rich plasma improves cardiac function after myocardial injury". Cardiovasc Revasc Med 12 (3): 158–63. doi:10.1016/j.carrev.2010.08.005. PMID 21122486.
- Griffin XL, Smith CM, Costa ML (2009). "The clinical use of platelet-rich plasma in the promotion of bone healing: a systematic review". Injury 40 (2): 158–62. doi:10.1016/j.injury.2008.06.025. PMID 19084836.
- Marx RE, Garg AK (1999). "Bone Graft Physiology with Use of Platelet-Rich Plasma and Hyperbaric Oxygen". In Jensen OT. The Sinus Bone Graft. Chicago: Quintessence. pp. 183–9. ISBN 0-86715-343-1.
- Por YC, Shi L, Samuel M, Song C, Yeow VK (2009). "Use of tissue sealants in face-lifts: a metaanalysis". Aesthetic Plastic Surgery 33 (3): 336–9. doi:10.1007/s00266-008-9280-1. PMID 19089492.
- Aimetti M, Romano F, Dellavia C, De Paoli S (2008). "Sinus grafting using autogenous bone and platelet-rich plasma: histologic outcomes in humans". The International Journal of Periodontics & Restorative Dentistry 28 (6): 585–91. PMID 19146054.
- Alan Schwarz (2009-02-16). "A Promising Treatment for Athletes, in Blood". New York Times (New York).
- Gretchen Reynolds (2011-01-26). "Phys Ed: Does Platelet-Rich Plasma Therapy Really Work?". New York Times.
- Carina Storrs (2009-12-18). "Is Platelet-Rich Plasma an Effective Healing Therapy?". Scientific American.
- Gina Kolata (2010-01-12). "Popular Blood Therapy May Not Work". New York Times.
- Foster TE, Puskas BL, Mandelbaum BR, Gerhardt MB, Rodeo SA (2009). "Platelet-rich plasma: from basic science to clinical applications". Am J Sports Med 37 (11): 2259–72. doi:10.1177/0363546509349921. PMID 19875361.
- "World Anti-Doping Agency announces changes to Prohibited List". Irish Medical Times. 2011-01-10.