This meta-analysis of ten studies that involved 395 adults in clinical trials on PRP therapy, either in combination with other therapy or alone, showed a significant reduction in mMASI score from pre-treatment to post-treatment. The overall efficacy evaluation of PRP showed that patients or doctors had a high degree of satisfaction with the treatment of melasma by PRP. In addition, the PRP in combination with other therapies, microneedling in particular, received higher subjective satisfaction rating than PRP treatment alone and in combination with intradermal injection.

Previous studies have shown that TGF-β1 in PRP can inhibit melanin synthesis by delaying activation of extracellular signal-regulated kinase [29]. Concomitantly, PDGF in PRP may also lead to increased skin volume (angiogenesis, collagen synthesis and extracellular matrix formation), resulting in reduced pigmentation and skin luster [14]. It has also been determined that the levels of leukocyte differentiation antigen-4, interleukin-17 and cyclooxygenase-2 are higher in patients with melasma than in normal control [30]. Thus, it can be speculated that the curative effect of PRP is not only related with pigment metabolism, but also with its multiple repair function, its antibacterial or anti-inflammatory effect and its skin imperceptible blood-vessel remodeling function, all of which play a role in the several major pathology and pathogenesis of melasma, namely impaired skin barrier function, inflammation [31], pigment metabolic disorders and vascular changes.

PRP is a relatively new strategy in the treatment of melasma. To our best knowledge, this paper is the first systematic review and meta-analysis of PRP for melasma. Our research has three main advantages: First, we have comprehensively and systematically evaluated and analyzed the role of PRP in the treatment of melasma by using publication bias, regression analysis, subgroup analysis and mean subjective evaluation methods. Second, we rigorously included articles, extracted, analyzed and grouped the data by two individuals, and selected the most common and reliable MASI scoring method [32] to achieve a relatively small heterogeneity among included studies. Third, the studies we included were all very recent studies, with publication dates concentrated between 2019 and 2021.

Among the studies included in our meta-analysis, there was one study [25] with greater heterogeneity compared with the other studies that achieved a more obvious efficacy with PRP microneedle injection. Microneedles provide a minimally invasive and painless route of drug delivery by forming microchannels in the skin to enhance the penetration of active substances. It has already been used to treat skin conditions, such as wrinkles, acne scarring and discoloration, as well as to help facial rejuvenation. Combined with the results of subjective efficacy evaluation, we have reason to believe that microneedling may be a good route of PRP administration.

In terms of improving treatment with PRP, we can try to improve or develop new administration routes of PRP to facilitate its clinical application. For example, a recent study reported that a single-hand synchronous application of PRP and microneedling by attaching a derma roller with a 5-ml pipette secured by a sterile micropore tape [33]. Another recent study [28] showed that PRP significantly outperformed tranexamic acid in treatment for melasma from week 4 through week 24, suggesting that PRP therapy may be superior to other procedures; however, more randomized controlled studies are needed to confirm this. In addition to regaining a more balanced and stable complexion, many patients with PRP also have improved skin quality, including wrinkle levels, elasticity and skin hydration [23, 34]. Therefore, it would be valuable to offer a more personalized combination therapy to patients who want to treat melasma and improve skin quality simultaneously. In terms of mechanism study, it is meaningful to study the upstream and downstream molecules interacting with TGF-β in melasma, such as transcription of activating protein-1, PAX3, p53, MITF, tyrosinase-related protein 1 and tyrosinase [35].

There are a number of limitations associated with this meta-analysis. First, some of the included studies were of different duration and used treatment modalities of PRP. Second, not all of the included studies were strictly randomized controlled designs, which leads to reduced credibility in their results. Third, the MASI score of patients may be affected by a number of subjectively observed differences in the grading process. Fourth, due to insufficient data in the literature, we cannot determine the influence of melasma type or severity on the therapeutic effect of PRP.