What is platelet-rich plasma?
Platelet-rich plasma (PRP) is an increased concentration of autologous platelets suspended in a small amount of plasma after centrifugation and used for injection into a wound or a particular skin condition. Platelet-rich plasma is also called autologous platelet gel, plasma rich in growth factors (PRGF), and platelet concentrate (PC).
Blood normally consists of approximately 93% red blood cells (RBC), 1% white blood cells (WBC) and 6% platelets, suspended in plasma. The normal platelet count range is 150,000–350,000 per µL of blood. In platelet-rich plasma, the RBC count is lowered to 5 while the platelet count is increased to 94% (three to eight-fold greater than normal).
PRP is ‘autologous’, meaning that it comes from the patient's own body.
How is platelet-rich plasma collected?
Blood is withdrawn from a patient’s arm by syringe.
- The tubes containing withdrawn blood are placed in a centrifuge and spun using a carefully determined protocol.
- The speed and duration of centrifugation are very important to ensure the platelets are not damaged.
- Centrifuging separates the red and white blood cells and platelets and concentrates them at various levels in the tubes.
- Blood plasma that is rich in platelets is drawn off from the appropriate level for therapeutic use.
- An activating agent (eg, calcium chloride) is added to activate the platelets and release their content prior to use.
- Predictable and efficient compact systems to develop PRP are available commercially (eg, RegenLab, Switzerland) and can be used in office and hospital settings.
Background information about platelet-rich plasma
Platelets are probably best known as components of the blood clotting system. When injury disrupts a blood vessel and causes bleeding, platelets are activated and help with the formation of a clot that stems the flow of blood.
In addition, every platelet is also a biochemical storehouse of regulatory, signalling and growth-factor molecules that participate in recovery and healing of tissue in response to injury.
As an autologous preparation, PRP is safer to use than allogenic or homologous preparations and is free from concerns over transmissible diseases such as HIV, hepatitis, West Nile fever, and Creutzfeldt-Jakob disease.
PRP requires no special considerations regarding antibody formation, effectively preventing the risk of graft vs. host disease and leading to better acceptance by patients.
Role of platelet-rich plasma in wound healing
PRP effects soft tissue healing via growth factors released after platelet degranulation. These growth factors initiate and enhance physiological processes that contribute to tissue recovery and healing after injury.
Growth-factor molecules associated with platelets include:
- Platelet-derived growth factor (PDGF-AA, PDGF-BB, PDGF-AB)
- Transforming growth factor-beta (TGF-b1, TFG-b2)
- Vascular endothelial growth factor (VEGF)
- Epidermal growth factor (EGF)
- Pro- and anti-inflammatory cytokines (interleukin [IL]-4), IL-8, IL-13, IL-17, tumour necrosis factor-alpha, and interferon-alpha)
- Fibroblast growth factor-2 (FGF-2)
- Insulin-like growth factor (IGF)
- Fibrin, fibronectin, vitronectin, thrombin.
These growth factors aid healing by:
- Attracting undifferentiated stem cells into the newly formed matrix and triggering cell division
- Suppressing cytokine release and limiting inflammation
- Attracting macrophages to improve tissue healing and regeneration
- Promoting new capillary growth (new blood vessel formation), and accelerating epithelialisation.
Indications for platelet-rich plasma injections
There is accumulating evidence that PRP can help wound healing.
- Venous and arterial leg ulcers
- Diabetic foot ulcers
- Pressure ulcers (bedsores)
- Skin graft donor sites
- First and second-degree thermal burns
- Superficial injuries, cuts, abrasions and surgical wounds
- Hair loss – PRP has been shown to reinvigorate dormant hair follicles and stimulate new hair growth in male pattern alopecia
- Post-traumatic scars – PRP combined with centrifuged fat tissue and fractional laser resurfacing improve the cosmetic appearance of scars
- Facial rejuvenation
- Ocular indications may include dry eye and eyelid injection
- Urological indications may include urinary incontinence and sexual wellness
- Sports medicine and dentistry
Safety, complications and contraindications with platelet-rich plasma
PRP is immunologically neutral and poses no danger of allergy, hypersensitivity or foreign-body reactions.
Sterile technique must be used at every stage of PRP preparation and application. Sterile technique is especially important if a patient has an underlying medical condition that predisposes to infection.
The PRP may be injected intralesional or perilesional or mixed with autologous thrombin at a 9:1 ratio, forming a platelet gel and used topically.
When administered by intradermal injection, a brief period of inflammation at wound sites may be experienced. Nerve trauma is another potential complication.
The following medical conditions are a contraindication for use of PRP:
- Critical thrombocytopenia (low platelet count)
- Haemodynamic instability (collapse)
- Sepsis (infection)
- Acute and chronic infections
- Chronic liver disease
- Anti-coagulation therapy (warfarin, dabigatran, heparin).
What is the evidence to support platelet-rich plasma in wound healing?
Available data are largely based on case series. These studies have demonstrated:
- Healing of post-traumatic and vascular wounds, diabetic and chronic ulcers with a combination of PRP and autologous fat supported by a 3-dimensional matrix of hyaluronic acid
- Cosmetic improvement of scars with fat grafts mixed with PRP, followed by skin resurfacing with a nonablative laser
- Healing of open and chronic wounds of the heel and ankle with a combination of PRP and hyaluronic acid
- Healing of dehiscent infected sternal wounds with a local application of PRP.
Case studies conducted in a number of countries have also shown that for patients who may have moderate wrinkling due to exposure to sunlight and/or simply due to age can benefit from PRP treatment.
- Results show that when PRP is applied by superficial or deep dermal injection, the skin texture, tone and firmness can improve within 3 weeks with ongoing improvements over the next few months.
- Areas commonly treated using PRP for rejuvenation include cheeks, around the eyes, jawline, back of hands, neck, knees, elbows, upper arms and post-pregnancy stretch marks.