An increasingly popular treatment for Androgenetic Alopecia (AGA) is Platelet Rich Plasma (PRP) therapy (1). Despite the complicated term, it is actually a fairly simple concept.
This article will review what PRP is and its biological mechanism for treating hair loss before reviewing the kind of results it can produce, as well as the typical success rates.
What is PRP?
Platelet Rich Plasma (PRP) therapy is a procedure where plasma is extracted, processed, and re-injected into the patient.
Blood is made up of two major components: the cellular part (i.e. red blood cells, white blood cells, platelets) and the fluid part, or plasma. The plasma consists primarily of water and proteins. To make plasma, whole blood is centrifuged or spun at high speed, separating it into its cellular and plasma components.
To prepare PRP, 10 to 60ml of blood are drawn from the patient, centrifuged, and then with a special syringe the platelet-rich portion of the plasma is extracted. Platelets are the component of blood that allows it to clot, and due to the way PRP is prepared and extracted, it contains a much higher concentration of platelets relative to whole blood. After the application of local anesthetic, the PRP is then injected into the balding area of the scalp.
There are various ways to prepare the PRP, and these relate not only to the particulars of the centrifugation, but also the addition or not of so-called “activators.” The activators, primarily calcium or thrombin, are meant to accelerate the release of growth factors from the platelets.
PRP is broadly classed as a regenerative medicine practice (2). It is based on the idea that the high density of platelets delivers growth factors (including VEGF, PDGF, EGF, TGF-β, and FGF) that prompt the body to heal itself through stem cell regeneration and soft tissue remodeling. These growth factors are contained in the 40 to 80 organelles within each platelet and are called alpha-granules; when these are activated the growth factors are released, helping the body to heal itself (3).
Uses for PRP
Though this article focuses on its use in AGA, PRP is not a treatment specific to AGA. It has a history of more than half a century, and it was originally developed for use in hematology patients (4). Quickly surgeons incorporated it into their practice and started using it to facilitate various kinds of surgery (5).
PRP is also used to accelerate healing in other dermatological conditions like ulcers, vitiligo, acute traumatic wounds, as well as musculoskeletal injuries and problems with tendons and ligaments (6, 7).
Despite the fact that PRP is only administered by licensed physicians, its use is somewhat controversial among the medical community. The crucial point involves the relative scarcity of controlled clinical trials, as well as the limited understanding of the underlying mechanism. Perhaps the most important issue is the lack of standardization and dramatically differing treatment protocols, which will be discussed below. This has led some medical bodies to view the procedure with suspicion.
PRP as a Treatment for AGA
Applied to AGA, PRP is thought to promote hair growth by increasing the survival and proliferation of hair follicle cells, stimulating follicles to transition from the resting to the anagen growth phase of the hair cycle, as well as prolonging the anagen phase. The combination of higher density and hairs that are growing out for longer periods of time leads to improved hair coverage.
There is no agreement on the exact biological mechanism through which PPR accomplishes this, which is not surprising considering many doctors do not even consider PRP an effective treatment (8).
According to one theory, the growth factors released by the platelets stimulate the dermal papilla cells in the hair follicles, which play a key role in the regulation of the hair growth cycle. They also induce the formation and proliferation of blood vessels, which sends a signal to the follicles to transition to anagen.
The Evidence of its Efficacy
Though PRP studies are nowhere near as abundant as for example, those of finasteride or minoxidil, there is at this point a sufficient body of evidence to allow for literature review and metanalyses (9, 10). Both literature reviews and metanalyses are more revealing compared to any one study, since they involve far larger sample sizes. The difference between the two is that a literature review offers a qualitative assessment, whereas a meta-analysis will use statistical methods to put a numerical value on PRP’s effectiveness.
This does not mean that meta-analyses are necessarily superior to literature review. The various PRP studies use different treatment protocols, different measures of efficacy, and involve differing patient populations. This means a meta-analyses has to use statistical manipulations to make all the data points comparable and there are clear limits to how far disparate data points can be jointly analyzed.
The first literature review was published in 2018, and looked at 12 studies that took place between 2011 and 2017 (11). In total 295 male and female patients with AGA were recruited in these studies.
Ten of the 12 studies produced positive results, and the remaining two showed negative ones. Of the ten that showed an effect for PRP, six used objective statistical analyses of quantifiable parameters like hair density and diameter, while the other four did not perform statistical analyses. All the studies with three or more treatment sessions reported positive results. The study with the longest follow-up period found that a number of patients (four out of 23) started to lose their new hair 12 months after the last treatment (12).
The review highlights the marked differences between the various treatment protocols, which go far beyond the different methods of preparing the PRP. The intervals between sessions range from two, three or four weeks all the way up to three months, and the total number of sessions administered are between one and six. The differences are equally pronounced with regards to the PRP preparation and administration itself, starting with the duration and speed of centrifugation, the addition or not of activators as well as the type of activator used, and the volume of blood and PRP used. There are also large differences in the number, distribution, and type of injections to the scalp.
The second literature review was published a year later and looked at a set of nine studies, which largely overlapped with the 12 studies in the earlier review (13). Seven of the nine studies showed positive results.
The review found minimal side effects, primarily transient pain at the site of the injections. No other major or unexpected side effects were reported. Once again, the review highlights the large disparity of treatment protocols and lack of standardization. Based on the evidence, it recommends PRP as a possible adjunct (adjuvant) treatment, i.e. one given to support the primary treatment, be it finasteride or minoxidil. It also suggests a standardized protocol that involves one centrifugation and the addition of an activator. With regards to treatment frequency, the recommendation is monthly treatments for the first three months, followed by once every three thereafter until a year after the first treatment.
The most recent meta-analysis was published in 2017, and it analyzed the results of six studies that fulfilled the meta-analysis’ inclusion and exclusion criteria (14). To be included in the meta-analysis, a study should only have patients with AGA (minimum 10), there should be some kind of control or comparator, and the increase in hairs per cm2 should be recorded. This is arguably the most common efficacy measure used in the hair loss literature and allows studies on PRP to be compared not only against each other, but also against studies of other AGA treatments.
The meta-analysis found the mean hair regrowth per cm2 was 17.9 hairs, which is comparable to minoxidil (15 to 20 hairs per cm2). PRP treatment also resulted in a statistically significant difference in hair cross-section, as reported in a pair of studies.
What is the Percentage of Responders?
The problem with this figure of 17.9 hairs per cm2 is that it is an average, calculated by combining results from patients who had zero regrowth with those who experienced mild, moderate, or marked regrowth. An alternative way of measuring effectiveness is to compare the percentage of responders to non-responders.
A 2017 study out of Barcelona, Spain is illuminating in this regard (15). The researchers recruited 19 men and 59 men with AGA and administered a total of six PRP sessions. 71.4% of the men showed some degree of improvement, 21.4% remained stable and 7.1% deteriorated. The figures for women were similar (73.4%, 16.3%, and 10.2% respectively). You can see here the before and after photos of a successfully treated man, and here those of a woman.
Is PRP for Androgenetic Alopecia a Sensible Option?
A yes-or-no answer to this question would probably have to be no. This is not due to the lack of efficacy, since as discussed here PRP most probably works, though not spectacularly. The problem lies with the cost.
Depending on where you live, a single PRP session can cost between $500 to $1000 or more. This means five sessions can total in excess of $5000. It is impossible to justify this outlay given it is not far off the cost of a minor transplant, which will give you far better results (16). And if you are prepared to travel to a foreign destination like Mexico or Turkey, you will actually be spending less money for a full-scale transplant.
For the average man with hair loss, the opportunity cost is simply too large. Unfortunately, many men will not perform this cost-benefit calculation prior to starting treatment, meaning they will forego treatment options that would yield them superior results for the money invested.
Having said that, PRP might be an option worth considering for a particular group of male patients, and particularly those for whose budget is not an issue. An increasing number of hair surgeons are incorporating PRP as an adjunct treatment for their transplant patients, noting that it increases graft survival and gives better long-term results. For men with a more diffuse pattern of hair likely to respond well to finasteride or minoxidil, the administration of a few PRP sessions to kickstart regrowth can also be considered. Women might also benefit from PRP administered in this fashion.
The fact that results are long-lasting (though probably not permanent), as well as the minimal time commitment and near complete lack of side effects, are also factors that undoubtedly weigh in favor of PRP over other standard AGA treatments.
PRP is rapidly gaining in popularity among dermatologists and other health care professionals, though the medical community as a whole remains divided on this treatment, with some researchers dismissing it altogether as ineffective. A cynical observer might remark that part of this treatment’s appeal for doctors lies not so much in its effectiveness, but in its high money-earned to effort-expended ratio. In other words, it is a relatively simple procedure that can generate large revenue in a short amount of time.
While the limited data to date suggest that PRP is effective, the effect is likely small, on par with minoxidil. For most men with hair loss, this will make PRP an impractical solution, especially when considering that most insurance companies in the US will not cover this procedure.
Exceptions include those who can afford to undertake PRP as an adjunct to a hair transplant or medical treatment, as well as those who for one reason or another have ruled out other treatment options. Another group of patients who could consider PRP are those who have developed resistance to long-term finasteride treatment.