Oral and Maxillofacial Surgery
Platelet-rich fibrin (PRF): A second-generation platelet concentrate. Part II: Platelet-related biologic features

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Platelet-rich fibrin (PRF) belongs to a new generation of platelet concentrates, with simplified processing and without biochemical blood handling. In this second article, we investigate the platelet-associated features of this biomaterial. During PRF processing by centrifugation, platelets are activated and their massive degranulation implies a very significant cytokine release. Concentrated platelet-rich plasma platelet cytokines have already been quantified in many technologic configurations. To carry out a comparative study, we therefore undertook to quantify PDGF-BB, TGFβ-1, and IGF-I within PPP (platelet-poor plasma) supernatant and PRF clot exudate serum. These initial analyses revealed that slow fibrin polymerization during PRF processing leads to the intrinsic incorporation of platelet cytokines and glycanic chains in the fibrin meshes. This result would imply that PRF, unlike the other platelet concentrates, would be able to progressively release cytokines during fibrin matrix remodeling; such a mechanism might explain the clinically observed healing properties of PRF.

Section snippets

Biologic mechanisms

Formed in bone marrow from megacaryocytes, platelets are discoidal and anuclear structures. Their lifespan is 8 to 10 days, and the cytoplasm contains many granules whose contents are secreted at the time of activation.

α-Granules contain many proteins, platelet specific (such as β-thromboglobulin) or nonplatelet specific (fibronectin, thrombospondin, fibrinogen, and other factors of coagulation, growth promoters, fibrinolysis inhibitors, immunoglobulins, etc.). The dense granules contain

Platelet distribution in PRF

Preliminary hematologic studies revealed that platelet in the acellular supernatant (platelet-poor plasma (PPP)) or in the red blood corpuscles base, did not remain. A few histologic analyses were sufficient enough to determine the platelet distribution within the various layers of the centrifuged collection tube: They accumulate in the lower part of the fibrin clot, mainly at the junction between the red corpuscles (red thrombus) and the PRF clot itself (Fig. 1). This last observation

Material and methods

Blood collection was carried out on 15 healthy volunteers, nonsmoker males from 20 to 28 years of age. In accordance with French law no. 88-1138 of December 20, 1988, dealing with the protection of people participating in biomedical research, and the World Medical Association Helsinki Declaration, volunteers received clear and honest information about the nature and the objectives of our study before testing.

Blood samples were treated according to the PRF protocol with a PC-02 table centrifuge

Results

Two major items of data were highlighted by statistical analysis of the results.

First, there are no significant differences (P < 5%) between the cytokine concentrations measured in PPP supernatant and those in the actual PRF clot.

Second, PDGF-BB and TGFβ-1 rates measured in supernatants and PRF clots exudates are all quite significantly lower than those obtained with the several cPRP protocols (Fig. 5, Fig. 6). On the other hand, for IGF-I the supernatant and exudate rates are both

Interpretation of results

The analysis of our results makes it possible to establish significant working hypotheses concerning biologic PRF features. After comparison of our values with those obtained by other authors and vast range of cPRP protocols,20, 21, 22, 23 it is possible to consider that on the whole, PRF platelet cytokines remain trapped in the fibrin meshes, and probably even in the fibrin polymers.24

Indeed, during PRF processing, the absence of anticoagulant in the collection tube necessarily induced massive

Conclusion

This first biochemical analysis of the PRF composition indicates that this biomaterial consists of an intimate assembly of cytokines, glycanic chains, and structural glycoproteins enmeshed within a slowly polymerized fibrin network. These biochemical components have well known synergetic effects on healing processes. As an example, fibronectin, as cell proliferation and migration guide, potentiates the stimulative effects from PDGF-BB. These preliminary data therefore imply that PRF would not

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    This article is the English translation of: Dohan, S., J. Choukroun, A. Dohan, J.-M. Donsimoni, D. Gabrieleff, F. Fioretti, G. Korb, and D. Dohan, Platelet Rich Fibrin (PRF): un nouveau biomatériau de cicatrisation. 2ème partie: Plaquettes et cytokines. Implantodontie 2004;13:99-108. Published in the French journal Implantodontie, Elsevier SAS. All rights reserved.

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