Platelet-rich plasma

Platelet-rich plasma (PRP), also known as autologous conditioned plasma, is a concentrate of platelet-rich plasma protein derived from whole blood, centrifuged to remove red blood cells. Though promoted to treat an array of medical problems, evidence for benefit is mixed as of 2020, with some evidence for use in certain conditions and against use in other conditions.

As a concentrated source of blood plasma and autologous conditioned plasma, PRP contains several different growth factors and other cytokines that can stimulate healing of soft tissue and joints. There are some indications for use in sports medicine and orthopedics (acute muscle strains, tendinopathy and muscle-fascial injuries and osteoarthritis), or dermatology (androgenic alopecia, wound healing, and skin rejuvenation) or even in proctology (fistula-in-ano). 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. Besides the use in clinical practice PRP has been utilized for various tissue engineering applications in the context of bone, cartilage, skin, and soft tissue repair. It has been reviewed to serve as a source for the "delivery of growth factors and/or cells within tissue-engineered constructs, often in combination with biomaterials".

The second generation of PRP is known as platelet-rich fibrin (PRF).

Medical use

Evidence for benefit of PRP is mixed, with some evidence for use in certain conditions and against use in other conditions. It has been investigated for chronic tendinitis, osteoarthritis, in oral surgery, and in plastic surgery.

A 2019 review found it not to be useful in rotator cuff disease. While an older review found that it may be useful. Tentative evidence supports its use in osteoarthritis (OA) of the knee. A 2019 meta-analysis found that PRP might be more effective in reducing pain and improving function than hyaluronic acid in knee OA.

A 2009 review found few randomized controlled trials that adequately evaluated the safety and efficacy of PRP treatments and concluded that PRP was "a promising, but not proven, treatment option for joint, tendon, ligament, and muscle injuries". As compared to other conservative treatments for non-surgical orthopedic illnesses (e.g. steroid injection for plantar fasciitis), evidence does not support the use of PRP as a conservative treatment. A 2018 review found that evidence was lacking for Achilles tendinopathy. A 2019 meta-analysis found that, for most outcomes in Achilles tendinopathy, PRP treatment did not differ from placebo treatment.

A 2010 Cochrane review of use in sinus lifts during dental implant placement found no evidence of benefit. A 2013 review stated more evidence was needed to determine effectiveness for hair regrowth.

A 2014 Cochrane review of PRP in musculoskeletal injuries found very weak evidence for a decrease in pain in the short term, and no difference in function in the short, medium or long term. There was weak evidence that suggested that harm occurred at comparable, low rates in treated and untreated people. Similarly, another 2017 review for treating pain on skin graft donor sites found the evidence for benefit was poor.

It has not been shown to be useful for bone healing. A 2016 review of PRP use to augment bone graft found only one study reporting a difference in bone augmentation, while four studies found no difference.

Adverse effects

Adverse effects have been poorly studied. The single systematic review of the literature did not report of the types and number of adverse events. In 2019, Health Canada stated that most autologous cell therapies have little evidence showing they work and can pose risks, such as cross-contamination between people if equipment is not sterilized properly or potentially dangerous immune reactions. Health Canada stopped Canadian clinics from offering these types of services with a donor-patient model. Health Canada later clarified that PRP treatments harvested from, and given back to, the same person (in a single procedure) was not covered by its initial guidance as the procedure falls under health care provider regulatory bodies (rather than Health Canada).

Composition

There are four general categories of preparation of PRP based on its leukocyte and fibrin content: leukocyte-rich PRP (L-PRP), leukocyte reduced PRP (P-PRP; leukocyte reduced or pure PRP), leukocyte platelet-rich fibrin and pure platelet-rich fibrin (PRF).

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 the mentioned 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 A
* vascular endothelial growth factor C
* epidermal growth factor
* Interleukin 8
* keratinocyte growth factor
* connective tissue growth factor
* Hepatocyte growth factor
* Stromal cell-derived factor 1
* Endostatin

Manufacturing

PRP is prepared by taking blood from the person, and then putting it through two stages of centrifugation designed to separate PRP from platelet-poor plasma and red blood cells. This is usually done by the clinic offering the treatment, using commercially available kits and equipment. The resulting substance varies from person to person and from facility to facility, making it difficult to understand how safe and effective any specific use is.

File:Blood drawn from patient.JPG, Blood drawn from patient
File:Removal of PRP after double centrifugation.JPG, Removal of PRP after double centrifugation
File:PRP is Injected into area of injury via ultrasound guidance.JPG, PRP is Injected into area of injury via ultrasound guidance

Society and culture

PRP has received attention in the popular media as a result of its use by athletes. Use in an office setting is not approved by the FDA.

In the 2010s, contentious cosmetic procedures marketed under the name of "vampire facials" grew in popularity, fueled by celebrity endorsement. These "vampire facials" generally center on PRP treatment, and usually (but not always) involve microneedling.

PRP has also been injected into the vagina, in a procedure called "O-shot" or "orgasm shot", with claims that this will improve orgasms. There is no evidence, however, to support these claims.

There are concerns from researchers studying PRP that it may be overused in a clinical setting including by for-profit unproven stem cell clinics, which market it for dozens of conditions mostly without evidence.

Doping

Some concern exists as to whether PRP treatments violate anti- doping rules. As of 2010, it was not clear if local injections of PRP could have a systemic impact on circulating cytokine levels, affecting doping tests and 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".

History

In the early 1940s clinicians used extracts of growth factors and cytokines for healing. The term 'platet-rich plasma' was first used in 1954 by Kingsley and in the 1960s the first PRP blood banks were established, becoming popular by the 1970s. In the 1970s PRP was used in the field of hematology, originally for transfusions to treat thrombocytopenia. Ten years later it was used for maxillofacial surgeries. PRP was first used in Italy in 1987 in an open heart surgery procedure. Ferrari M, Zia S, Valbonesi M, Henriquet F, Venere G, Spagnolo S, Grasso MA, Panzani I. A new technique for hemodilution, preparation of autologous platelet-rich plasma and intraoperative blood salvage in cardiac surgery. Int J Artif Organs. 1987 Jan;10(1):47-50. PMID: 3570542 In 2006 PRP was starting to be considered of potential use for both androgenic alopecia and alopecia areata, though research remained mixed.

See also

* Autologous blood injection
* Autologous conditioned serum
* Hypoxia preconditioned plasma
* Platelet-rich fibrin matrix
* Platelet swirling

References

{{DEFAULTSORT:Platelet-Rich Plasma
Blood products
Transfusion medicine