Platelet-rich plasma (PRP) and platelet derivatives for topical therapy. What is true from the biologic view point?

Background  PubMed accessed on January 23 revealed 160 items about ‘platelet gel or releasate’ associated to topical therapy. Yahoo! provided 8580 items; Altavista 8650; Google 25 300. Companies providing blood separators are going to offer devices to prepare platelet-rich plasma (PRP) for topical therapy. Several devices are filling the marketplace aiming to produce platelet gels for human therapy. Never-ending lists of clinical conditions supposed to benefit from platelet gel application are published. Clinical benefits include bactericidal activity, pain reduction, tissue repair and regeneration. Are platelet derivatives the magic bullet for topical therapy? Methods  Many in vitro studies account for clinical benefit from platelet gel. Several in vivo studies provide clinical evidence about healing of tissue repair induced by platelet derivatives. Nevertheless, systematic reviews reveal inadequate studies providing enough methodological strength to confirm evidence-based efficacy. At present we must deal the subject with care using mostly inductive criteria. Only reproducible scientific data are to be considered. Every effort should be made for commercial, private and personal popularity-related scenarios to be rejected from our consideration. Sometimes, this is not so simple to be done. Results  There is a list of more than 60 biologically active platelet-derived factors directly involved in tissue repair mechanisms: chemotaxis, cell proliferation, angiogenesis, extracellular matrix deposition and remodelling. Biological functions are also indirectly mediated by platelet-derived growth factors; such functions are triggered by chemokines and cytokines produced by bystander cells such as fibroblasts, macrophages, endothelial cells, lymphocytes, under platelet-derived factor stimulation. All of this is well demonstrated. Clinical studies endorsed with stringent randomized controlled trials are lacking. However, several serious studies have been published reporting clinical efficacy of platelet derivatives in many clinical areas. Considering these papers seriously, we maintain that in most cases, clinical efficacy is by far more than just a suggestion. Discussion  Although we consider evidence-based medicine (EBM) highly meaningful, we emphasize that medicine moved forwards also before EBM was conceived. We do not consider platelet gel and releasate such as a ‘magic bullet’, but we are strongly impressed by the results our group, and other groups have obtained treating a variety of tissue lesions in a variety of clinical conditions. Clinical benefits are a composite result of the lesion state, severity and duration, coexisting pathologies, patient's age and product characteristics. From our point of view, the last is a pivotal variable that has strong influence over the clinical outcome. Platelet-rich plasma, platelet gel and platelet releasate need stringent definitions. Too many methods are used to prepare these products. Both methods and product need definition, validation, specific quality parameters and clinical indications. Further biologic and biochemical studies are needed as well to understand (if possible to modulate) the inner mechanisms of healing induced by topical treatment with platelet derivatives.