Growth Factors Release of PRF and PRGF

Overview

Background: platelet concentrate could enhance growth factors (GF) crevicular fluid levels which might be crucial to proper tissue repair and wound healing. However, the open usually contaminated nature of periodontal defects could affect negatively GF availability and activity. To test this assumption, this study was designed to evaluate levels of VEGF and PDGF-BB in gingival crevicular fluid (GCF) during the early stages of healing of localized intrabony defects treated with platelet rich in growth factor (PRGF) and platelet rich fibrin (PRF) as compared with xenograft defect filling control. Methods: Thirty non-smoking patients with severe chronic periodontitis participated in this prospective, randomized and single blinded trial. Each patient contributed one interproximal defect that was randomly assigned to the bone substitute grafting control (n=10) G1, experimental PRGF (n=10) G2 and PRF (n=10) G3. Plaque index, gingival index, probing depth (PD), clinical attachment level (CAL) and the intrabony depth of the defect (IBD) were measured at baseline for patient enrollment. Gingival crevicular fluid (GCF) samples were collected on days 1 and 3, 7, 14, 21, and 30 days after therapy. The primary outcome variable was the change in VEGF and PDGF-BB levels for sites treated by PRGF and PRF compared to that of the xenograft treated cases.

Owing to the lots of challenges that facing the use of recombinant growth factors in periodontal therapy, it is important to look for an alternative that combine ease of preparation and physiologic mode of delivery. Platelet concentrate has been developed for this purpose with many debates about the duration of GF availability in the defect area. Platelet-rich fibrin (PRF) is a leucocyte- and platelet-rich fibrin biomaterial. This dense fibrin membrane was claimed to releases high quantities of three main growth factors (Transforming Growth Factor b-1 (TGFβ-1), platelet derived growth factor AB, PDGF-AB; vascular endothelial growth factor, VEGF) and an important coagulation matricellular glycoprotein (thrombospondin-1, TSP-1). It has a natural fibrin framework that can protect growth factors from proteolysis. It is shown that PRF can release growth factors gradually and keep their activity to a relatively long period compared with platelet rich plasma (PRP). Levels of released TGF-1 and PDGF-AB markedly increased and reached the highest amount at day , then decreased mildly. In contrast, PRP experienced uncontrollable and short-term release of TGF-1 and PDGF-AB, which reached the highest amount at day 1 and then decreased rapidly.Clinically, it was found that PRF can improve clinical parameters associated with human intrabony periodontal defects and BPBM (bovine porous bone mineral) has the ability to augment effects of PRF in reducing pocket depth, improving clinical attachments levels, and promoting defect fill. On the other hand studies reported similar PD (probing depth) reduction, CAL (clinical attachment level) gain, and bone fill at sites treated with PRF or PRP compared with conventional open flap debridement. Preparation rich in growth factors (PRGF-Endoret) technology was claimed to circumvent many of the limitations of other reported platelet-rich preparations. Sodium citrate and calcium chloride are used as an anticoagulant and a clot activator, respectively. Addition of calcium chloride promotes the formation of native thrombin, mimicking the physiological clotting process and enabling a more sustained release of growth factors, which might be crucial to proper tissue repair and wound healing. Moreover, this procedure obviates immunological reactions and the risk of disease transmission associated with the use of exogenous bovine thrombin. Anitua et al reported that PRGF contains a moderately elevated platelet concentration of \~6x105 platelets, which has been reported to induce the optimal biological benefit. Lower platelet concentrations can lead to suboptimal effects, whereas higher concentrations might have an inhibitory effect. PRGF application after extraction improved the healing process in diabetic patients by accelerating socket closure (epithelialization) and tissue maturation, proving the association between PRGF use and improved wound healing in diabetic patients. In the present study it was proposed that the opened, constantly contaminated nature periodontal defects could be a source of continuous catabolic bacterial and tissue enzymes and binding proteins that affect platelet concentrate contained GF availability and activity. To confirm this assumption, this study was designed to evaluate levels of platelet derived growth factor - BB (PDGF-BB) and vascular endothelial cell growth factor (VEGF) in GCF during the early stages of healing for sites treated with PRF and PRGF in intrabony periodontal defects and to correlate GF levels with the clinical findings. This could figure out the potentials of these 2 commonly used platelet concentrate in the periodontal defects ecology.