Advanced platelet-rich fibrin: a new concept for cell-based tissue engineering by means of inflammatory cells

Local Application of Autologous Platelet-Rich Fibrin Patch (PRF-P) Suppresses Regulatory T Cell Recruitment in a Murine Glioma Model

The immunosuppressive microenvironment is one of the major factors promoting the growth of glioblastoma multiforme (GBM). Infiltration of CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) into the tumor microenvironment plays a significant role in the suppression of the anti-tumor immunity and portends a dismal prognosis for patients. Glioma-mediated secretion of chemo-attractant C-C motif ligand 2 and 22 (CCL2/22) has previously been shown by our group to promote Treg migration in vitro. In this study, we show that a local implantation of platelet-rich fibrin patch (PRF-P) into the brain of GL261 glioma-bearing mice prolonged the survival of affected animals by 42.85% (p = 0.0011). Analysis performed on brain tumor tissue harvested from PRF-P-treated mice revealed a specific decrease in intra-tumoral lymphocytes with a preferential depletion of immunosuppressive Tregs. Importantly, co-culture of GL261 or chemo-attractants (CCL2/22) with PRF-P abrogated Treg migration. Pharmacological blockade of the CCL2/22 interaction with their receptors potentiated the inhibitory effect of PRF-P on Tregs recruitment in culture. Moreover, our findings revealed the soluble CD40 ligand (sCD40L) as a major Treg inhibitory player produced by activated platelets entrapped within the fibrin matrix of the PRF-P. Blockade of sCD40L restored the migratory capacity of Tregs, emphasizing the role of PRF-P in preventing the Treg migration to glioma tissue. Our findings highlight autologous PRF-P as a personalized, Treg-selective suppression platform that can potentially supplement and enhance the efficacy of glioma therapies.

Impact of incubation method on the release of growth factors in non-Ca2+-activated PRP, Ca2+-activated PRP, PRF and A-PRF

The aim of this study was to investigate the influence of different incubation methods on the growth factor content of lysates of platelet-rich fibrin (PRF), advanced-platelet-rich fibrin (A-PRF) and platelet-rich plasma (PRP) products. A comparison of related studies suggests that the method of sample preparation has a significant influence on growth factor content. There are few reports on the comparison of non-Ca²⁺-activated PRP, Ca²⁺-activated PRP, A-PRF, and PRF, along with a lack of information on the release of PDGF-BB, TGF-β1, and VEGF among the different incubation methods. The lysate preparation was made of non-Ca²⁺-activated PRP, Ca²⁺-activated PRP, PRF, and A-PRF, using a room-temperature, 37 °C, or freeze-thaw-freeze incubation method. Afterwards the VEGF, PDGF-BB, and TGF-β1 content was investigated by running ELISA tests. Growth factor levels were significantly increased in the non-Ca²⁺-activated PRP with freeze-thaw-freeze incubation, and in the PRF preparation there was a significant disadvantage to using room temperature incubation for releasing growth factors. In conclusion, the freeze-thaw-freeze method is sufficient for releasing growth factors, and calcium activation is not necessary. Finally, the study demonstrates the possibility of preparing PRP products from platelet concentrates, so that preoperative blood sampling might not be required.

Influence of concentration and preparation of platelet rich fibrin on human bone marrow mononuclear cells (in vitro)

Large bone defects have always been a big challenge. The use of bone marrow mononuclear cells (BMCs) combined with an osteoconductive scaffold has been proved a good alternative for the treatment of large bone defects. Another autologous source for tissue engineering is platelet rich fibrin (PRF). PRF is a blood concentrate system obtained through a one-step centrifugation. The generated 3D matrix of the PRF clot serves as a reservoir of growth factors. Those growth factors might support the regenerative response of BMC, and therefore the effect of PRF, centrifuged with either high medium (208 g) or low (60 g) relative centrifugation force (RCF) on BMCs was evaluated in vitro in the present study. The two PRF matrices obtained were initially characterized and compared to human serum. Significantly increased concentrations of insulin-like growth factor (IGF), soluble intercellular adhesion molecule-1 (sICAM1) and transforming growth factor (TGF)-β were found in PRF compared to human serum whereas VEGF concentration was not significantly altered. A dose-response study revealed no further activation of BMC's metabolic activity, if concentration of both PRF matrices exceeded 10% (v/v). Effect of both PRF preparations [10%] on BMC was analyzed after 2, 7, and 14 days in comparison to human serum [10%]. Metabolic activity of BMC increased significantly in all groups on day 14. Furthermore, gene expression of matrix metalloproteinases (MMP)-2, -7, and -9 was significantly stimulated in BMC cultivated with the respective PRF matrices compared to human serum. Apoptotic activity of BMC incubated with PRF was not altered compared to BMC cultivated with serum. In conclusion, PRF could be used as a growth factor delivery system of autologous or allogeneic source with the capability of stimulating cells such as BMC.

Individualized Titanium Mesh Combined With Platelet-Rich Fibrin and Deproteinized Bovine Bone: A New Approach for Challenging Augmentation

Autologous bone transfer is regarded as the gold standard for ridge augmentation before dental implantation, especially in severe bony defects caused by tumor resection or atrophy. In addition to the advantages of autologous bone, transplantation has several disadvantages, such as secondary operation, increased morbidity and pain. The present study reports, for the first time, a combination of a xenogeneic bone substitute (BO) with platelet-rich fibrin (PRF), which is a fully autologous blood concentrate derived from the patient's own peripheral blood by centrifugation. Solid A-PRF+ and liquid i-PRF together with an individualized 3-D planned titanium mesh were used for reconstruction of a severe tumor-related bony defect within the mandible of a former head and neck cancer patient. The BO enriched with regenerative components from PRF allowed the reconstruction of the mandibular resective defect under the 3-D mesh without autologous bone transplantation. Complete rehabilitation and restoration of the patient's oral function were achieved. Histological analysis of extracted bone biopsies confirmed that the new bone within the augmented region originated from the residual bone. Within the limitations of the presented case, the applied concept appears to be a promising approach to increase the regenerative capacity of a bone substitute material, as well as decrease the demand for autologous bone transplantation, even in cases in which autologous bone is considered the golden standard. PRF can be considered a reliable source for increasing the biological capacities of bone substitute materials.

Bioengineered surgical repair of a chronic oronasal fistula in a cat using autologous platelet-rich fibrin and bone marrow with a tailored 3D printed implant

Clinical summary: A tissue engineering approach was used to aid the surgical repair of a chronic oronasal fistula (ONF) in a 13-year-old cat. A three-dimensional (3D) printed mesh, tailored to the size and shape of the ONF, was created to support a soft tissue flap used to close the defect; and also to provide a matrix for mesenchymal stromal cells present in bone marrow aspirate and bioactive cytokines and growth factors present in platelet-rich fibrin harvested from the patient. A CT scan at day 75 after surgery revealed the formation of new tissue in the defect and the healing process was complete at follow-up 6 months after surgery. Relevance and novel information: Complications are frequently reported following surgical repair of ONFs and include dehiscence of the palatal suture line, flap necrosis due to damage to the greater palatine artery and maxillary osteomyelitis, mainly due to chronic infection and bone lysis. The case described here demonstrates how input from a multidisciplinary team and the use of a biomaterial, processed by sophisticated technologies, can create a precision regenerative medicine strategy adapted to the patient's clinical needs; this provided a novel therapeutic solution for an otherwise hard to treat clinical problem.

Biofabrication of a novel leukocyte-fibrin-platelet membrane as a cells and growth factors delivery platform for tissue engineering applications

Autologous platelet-rich hemocomponents have emerged as potential biologic tools for regenerative purpose, but their therapeutic efficacy still remains controversial. This work represents the characterization study of an innovative autologous leukocyte-fibrin-platelet membrane (LFPm), which we prepared according to a novel protocol involving multiple cycles of apheresis. The high content in fibrinogen gave to our hemocomponent the appearance of a manipulable and suturable membrane with high elasticity and deformation capacity. Moreover, being highly enriched with platelets, leukocytes, and monocytes/macrophages, the LFPm sustained the local release of bioactive molecules (platelet derived growth factor, vascular endothelial growth factor, interleukin-10, and tumour necrosis factor alpha). In parallel, the evaluation of stemness potential highlighted also that the LFPm contained cells expressing pluripotency and multipotency markers both at the messenger ribonucleic acid (NANOG, SOX2, THY1, NT5E, and ENG) and surface-protein level (CD44^high /CD73⁺ /CD34⁺ /CD117⁺ /CD31⁺ ). Finally, biodegradation analysis interestingly showed a good stability of the membrane for at least 3 weeks in vitro and 1 week in vivo. In both cases, biodegradation was associated with progressive exposure of fibrin scaffold, loss/migration of cellular elements, and release of growth factors. Overall, collected evidence could shed some light on the regenerative effect that LFPms may exert after the autologous implant on a defect site.

Can platelet-rich fibrin improve healing after surgical treatment of medication-related osteonecrosis of the jaw? A pilot study

OBJECTIVE

The aim of this study was to evaluate the efficacy of platelet-rich fibrin (PRF) after bone surgery compared to surgery alone in the treatment of medication-related osteonecrosis of the jaw (MRONJ).

STUDY DESIGN

A total of 47 patients with diagnosis of stage II or III of MRONJ were recruited at the Academic Hospital of Magna Graecia University of Catanzaro and allocated to 2 groups: In the first, patients were treated with PRF in addition to surgery (PRF group), in the other, only bone surgery was performed (non-PRF group). Fisher's exact and Student t tests were used to evaluate differences between the 2 surgical protocols in terms of mucosal integrity, absence of infection, and pain evaluation at scheduled follow-ups of 1 month (T1), 6 months (T2), and 1 year (T3).

RESULTS

Analysis of mucosal integrity, absence of infection, and pain evaluation showed a significant difference between the 2 groups in favor of PRF only at T1 (P < .05), whereas no differences were determined at T2 and T3 (P > .05).

CONCLUSIONS

Our results suggested that local application of PRF after bone surgery may improve the quality of life limited to the short-term follow-up and reduce pain and postoperative infections.

The use of platelet-rich fibrin with platelet-rich plasma support meniscal repair surgery

Introduction

Platelet-rich fibrin (PRF) is the only autologous blood product that releases growth factors and has scaffolding properties. We hypothesized that the use of PRF and Platelet-rich plasma (PRP) would improve operative results, including the recovery of function and repaired meniscus.

Materials and Methods

Seventeen patients underwent arthroscopic meniscus repair with PRF and PRP (PRF group) using our novel device for the injection of the PRF into the joint. Another five patients as a control group underwent meniscal repair without PRF and PRP (non-PRF group). The groups were compared in terms of clinical results (Tegner Activity Level Scale, Lysholm Knee Scoring Scale, and International Knee Documentation Committee [IKDC] scores) and changes in magnetic resonance imaging (MRI) findings before surgery and 6 months after surgery.

Results

The Lysholm and IKDC scores improved in all patients postoperatively. However, there was no significant differencies in the postoperative score between the PRF group and the non-PRF group. Follow-up MRI findings did not clearly show improvements.

Conclusions

PRF and PRP are autologous, safe, and cost-effective sources of growth factors. Therefore, we propose a new application of PRF and PRP for autologous transplantation in meniscus repair surgery.

Telomere length and genetic variations affecting telomere length as biomarkers for facial regeneration with platelet-rich fibrin based on the low-speed centrifugation concept

BACKGROUND

Platelet-Rich Fibrin (PRF), a fibrin matrix produced by single blood centrifugation that contains leukocytes, platelets, and growth factors, is increasingly being utilized for facial regeneration purposes. However, our understanding of the involved pathophysiological mechanisms affecting regeneration is limited and current protocols require better optimization. Biomarkers that are related to skin aging such as telomere length (TL) have been proposed as a mean to analyze patients' stratification.

OBJECTIVE

Our aim is to study whether the outcomes of a facial regeneration protocol performed with PRF are related to TL and genetic variations affecting TL. This can aid in the standardization of a surgical aesthetic protocol.

PATIENTS AND METHODS

In all, 41 patients treated with PRF produced with the low-speed centrifugation concept were included in this observational study. The correlation between TL and genetic variations were assessed versus treatment outcomes, namely the number of sessions and aesthetic results utilizing the FACE-Q skin satisfaction questionnaire.

RESULTS

In all, 39 of the 41 patients completed the treatment. TL correlated with the initial responses to FACE-Q (ρ = .33, P = .05). Genetic variations affecting TL was related to the change of FACE-Q (ρ = .35, P = .034) as well as to the number of treatment sessions (ρ = .38, P = .019).

CONCLUSIONS

Telomere length (TL) was related to patient perceived facial skin appearance. In addition, genetic variations affecting TL were related to the final outcomes (number of sessions and improvements of FACE-Q results) and may be a useful biomarker for future regenerative procedures performed with PRF for facial regeneration.

Comparison of two surgical techniques in the treatment of multiple gingival recessions sandwiched with a combination of A-PRF and L-PRF

Aim

The aim of this study is to compare semilunar vestibular incision technique with pouch and tunnel technique in combination with A-PRF and L-PRF for treatment of Miller’s class I and II multiple gingival recessions.

Method

This is a randomized, controlled, double-blinded, split mouth study which consists of 16 systemically healthy patients with 96 sites and a mean age of 34.2 years, and divided randomly into 2 groups, Group A consists of semilunar vestibular incision technique sandwiched with A-PRF and L-PRF and Group B consists of Pouch and tunnel technique sandwiched with A-PRF and L-PRF. Clinical parameters were recorded at baseline, 3 months and 6 months which include plaque index, gingival index, recession depth, recession width, clinical attachment loss and width of keratinized tissue.

Results

All the clinical parameters showed significantly better levels for both the groups from baseline to 6 months. Semilunar vestibular incision technique showed greater significance when compared to pouch and tunnel technique from baseline to 6 months post operatively.

Conclusion

The combination of A-PRF and L-PRF with pouch and tunnel technique and semilunar vestibular technique showed better outcome 6 months post operatively. Semilunar vestibular incision technique showed promising results than pouch and tunnel technique for the treatment of multiple gingival recessions.

Enhancement of post-orthodontic tooth stability by carbonated hydroxyapatite-incorporated advanced platelet-rich fibrin in rabbits

OBJECTIVE

To evaluate the effect of carbonated hydroxyapatite-incorporated advanced platelet-rich fibrin on relapse and bone remodelling in rabbits.

MATERIALS AND METHODS

Forty-five rabbits were divided into 3 groups (n = 15): a control group, carbonated hydroxyapatite (CHA) and carbonated hydroxyapatite-incorporated advanced platelet-rich fibrin (CHA-aPRF) group. The lower incisors were subjected to an orthodontic force of 50 cN. During the retention period, CHA and CHA-aPRF hydrogel were gently injected in the mesial gingival sulcus every 7 days. Next, the appliances were debonded to allow relapse. At 5 subsequent time points (0, 3, 7, 14 and 21 days after debonding), the distance between the mesial tips of rabbits incisors was measured using a digital calliper, osteoblast quantity was evaluated using haematoxylin-eosin staining and osteoclast activity was examined using tartrate-resistant acid phosphatase (TRAP) staining.

RESULTS

The relapse rate of CHA-aPRF group was lower than that of the other groups, and the relapse distances were significantly lower on days 14 and 21 (P < .05). Histological analysis revealed that the number of osteoblasts was significantly higher and that the osteoclast activity was significantly lower in the CHA-aPRF group compared with the other groups (P < .05).

CONCLUSIONS

Intrasulcular injection of hydrogel CHA incorporated aPRF can locally reduce orthodontic relapse in rabbits.

Allogeneic bone block for challenging augmentation-a clinical, histological, and histomorphometrical investigation of tissue reaction and new bone formation

OBJECTIVES

The aim of the present study was the histological investigation of an allogeneic spongious bone block for horizontal and vertical ridge augmentation in humans. The amount of new bone, soft tissue, and residual bone substitute were histomorphometrically assessed after a mean healing period of 6 months.

MATERIALS AND METHODS

Fourteen patients received augmentation with an allogeneic spongious bone block (Tutobone^®, Tutogen Medical, Neunkirchen, Germany). After 6 months of healing, 28 implants were placed with simultaneous harvesting of bone biopsies for histological and histomorphometrical analysis. Moreover, samples from the bone blocks were collected as blanks and analyzed histologically. The formation of new bone, connective tissue, and remaining bone substitute material as well as vascularization and formation of multinucleated giant cells (MNCGs) within the augmentation bed were analyzed.

RESULTS

New bone formation could be observed primarily in close proximity to the bone block. Histomorphometrical analyses showed 18.65 ± 12.20% newly formed bone, 25.93 ± 12.36% allogeneic spongious bone block, and 53.45 ± 10.34% connective tissue. MNCGs were observed on the biomaterial surface. Furthermore, organic residues were evident, as donor-related cellular remnants within the osteocyte lacunae were found in the blank bone blocks and in the analyzed biopsies.

CONCLUSION

Despite the presence of donor-related organic remnants, the bone block shows the ability to serve as a scaffold for new bone formation. Within the limits of the present study, the detect organic remnants seemed not to affect the bone formation or influence the host in the long term.

CLINICAL RELEVANCE

Clinicians have to make a conscious choice of the applied biomaterials with regard to their components and structure to support tissue regeneration and maintain patient safety.

Early Placement of Dental Implants in Maxillary Sinus Grafted With Leukocyte and Platelet-Rich Fibrin and Deproteinized Bovine Bone Mineral

This case report aimed to describe the effects of leukocyte and platelet-rich fibrin (L-PRF) associated with demineralized bovine bone mineral (DBBM) and absorbable collagen membrane (CM) on bone regeneration in maxillary sinus augmentation. A 59-year-old male patient was referred to the Department of Periodontology for implant rehabilitation of his edentulous upper jaw. The treatment plan involved maxillary sinus augmentation followed by implant installations. A split-mouth design was employed in which the right maxillary sinus was filled using L-PRF, DBBM, and CM; the left side was filled with DBBM and CM. After 4 and 8 months postoperatively, 2 dental implants were installed in each of the right and left maxillary sinuses. Cone-beam computerized tomography (CBCT) was taken before and after sinus augmentation for evaluation of tridimensional bone volume alterations. Bone biopsies were harvested from the implant sites for histomorphometric evaluation. Resonance frequency analysis was employed immediately after implant placement and before prosthetic rehabilitation for evaluation of implant stability. Implants were loaded 10 months after sinus augmentation. CBCT analysis showed a higher resorption rate in the right side of the maxillary sinus (L-PRF + DBBM) compared to the left side (22.25% and 8.95%, respectively). Implant stability quotients were above 68 in all time-points for both groups. Histomorphometric analysis showed a high amount of newly formed bone when L-PRF was used compared with DBBM alone (2 118 102 and 975 535 mm³, respectively). Taken together, both techniques were effective for maxillary sinus augmentation, however the addition of L-PRF to the graft allowed early implant placement and accelerated bone healing in the conditions studied.

Comparative Evaluation of Antimicrobial Efficacy of Platelet-rich Plasma, Platelet-rich Fibrin, and Injectable Platelet-rich Fibrin on the Standard Strains of Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans

Context:

Platelet concentrates are commonly used to promote periodontal soft- and hard-tissue regeneration. Recently, their antimicrobial efficacy is also explored. Various platelet concentrates have evolved which differ in the centrifugation protocols. Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa) have been found to have an important role in periodontal pathology.

Aims:

In this study, PRP, PRF, and I-PRF are compared for their antibacterial effect against Pg and Aa.

Materials and Methods:

Blood samples were obtained from ten systemically and periodontally healthy individuals. Platelet concentrates were prepared using standardized centrifugation protocol. Antimicrobial activity was examined on standard strains of Pg and Aa using well diffusion method.

Statistical Analysis Used:

Means for the width of zones of inhibition were calculated along with standard deviations, and the comparison was made using Wilcoxon signed-rank test.

Results:

In case of Pg, I-PRF had the widest zone of inhibition which was significantly wider as compared to PRF. Furthermore, PRP had significantly wider zone of inhibition against PRF. In case of Aa, PRP had wider zone of inhibition which was significantly wider as compared to that of PRF and I-PRF.

Conclusions:

All the three platelet concentrates PRP, PRF, and I-PRF have antibacterial activity, but PRP and I-PRF are more active as compared to PRF. I-PRF being autologous and easy to prepare can be a very useful adjunct to the surgical therapy in bringing down the bacterial count helping in wound healing and regeneration.

Sugar-based collagen membrane cross-linking increases barrier capacity of membranes

OBJECTIVES

This study examines the permeability and barrier capacity of a sugar cross-linked resorbable collagen membrane ex vivo and in vivo.

MATERIALS AND METHODS

In an ex vivo study, injectable platelet-rich fibrin (i-PRF), a peripheral blood-derived human leukocyte-and-platelet-rich plasma was used to analyze membrane permeability. in vivo subcutaneous implantation in Wistar rats (n = 4 per time point and group) was used to investigate the barrier capacity of the membrane. The induced in vivo cellular reaction was evaluated at 3, 15, and 30 days and compared to sham OP (control) without biomaterial using histological, immunohistochemical, and histomorphometric methods.

RESULTS

Ex vivo, the membrane was impenetrable to leukocytes, platelets, and fibrin from peripheral human blood concentrate (PRF). In vivo, the membrane maintained its structure and remained impervious to cells, connective tissue, and vessels over 30 days. CD-68-positive cell (macrophage) numbers significantly decreased from 3 to 15 days, while from day 15 onwards, the number of multinucleated giant cells (MNGCs) increased significantly. Correspondingly, a rise in implantation bed vascularization from 15 to 30 days was observed. However, no signs of degradation or material breakdown were observed at any time point.

CONCLUSION

Ex vivo and in vivo results showed material impermeability to cellular infiltration of human and murine cells, which highlights the membrane capacity to serve as a barrier over 30 days. However, whether the induced MNGCs will lead to material degradation or encapsulation over the long term requires further investigation.

CLINICAL RELEVANCE

The data presented are of great clinical interest, as they contribute to the ongoing discussion concerning to what extent an implanted material should be integrated versus serving only as a barrier membrane.

Mechanical and degradation properties of advanced platelet-rich fibrin (A-PRF), concentrated growth factors (CGF), and platelet-poor plasma-derived fibrin (PPTF)

BACKGROUND

Fibrin clot membranes prepared from advanced platelet-rich fibrin (A-PRF) or concentrated growth factors (CGF), despite their relatively rapid biodegradability, have been used as bioactive barrier membranes for alveolar bone tissue regeneration. As the membranes degrade, it is thought that the growth factors are gradually released. However, the mechanical and degradable properties of these membranes have not well been characterized. The purpose of this study was to mechanically and chemically characterize these membranes.

METHODS

A-PRF and CGF clots were prepared from blood samples collected from non-smoking, healthy donors and were compressed to form 1-mm-thick membranes. Platelet-poor plasma-derived fibrin (PPTF) clots were prepared by adding bovine thrombin to platelet-poor plasma. A tensile test was performed at the speed of 1 mm/min. Morphology of the fibrin fibers was examined by SEM. A digestion test was performed in PBS containing trypsin and EDTA.

RESULTS

In the tensile test, statistical difference was not observed in Young's modulus, strain at break, or maximum stress between A-PRF and CGF. In strain at break, PPTF was significantly weaker than CGF. Likewise, fibrin fiber thickness and crosslink density of PPTF were less than those of other membranes, and PPTF degraded faster than others.

CONCLUSIONS

Although the centrifugal conditions are different, A-PRF and CGF are prepared by essentially identical mechanisms. Therefore, it is conceivable that both membranes have similar mechanical and chemical properties. Only PPTF, which was prepared by a different mechanism, was characterized as mechanically weaker and enzymatically more degradable.

Effects of single- and double-layered resorbable membranes and platelet-rich fibrin on bone healing

OBJECTIVES

Research has been ongoing on achieving optimum bone healing in the reconstruction of bone loss. Clinically, soft tissue migration into the already existing bone defects is the leading cause of unfavourable bone healing. Platelet-rich fibrin, a recent material that is used to promote bone healing, was compared with single- and double-layered resorbable collagen membranes to determine whether a healing protocol which increases patient comfort is possible.

MATERIALS AND METHODS

Sixty adult female Sprague-Dawley rats were used. The rats were divided into five main groups as a sacrification group, a control group, and three experimental groups. The bone defects experimental group 1 were covered with a single-layer collagen membrane, and experimental group 2 were covered with the double-layered collagen membrane. Defects on the experimental group 3 were covered with platelet-rich fibrin membranes which were derived from the sacrification group. The animals in the main groups were also divided into eight subgroups arranged by sacrification periods on day 7 and day 28.

RESULTS

Statistical analysis of our study revealed that new bone formation in experimental group 3 was significantly higher than in other groups. Fibrosis was found to be lower in experimental group 3 than in any other group. No significant differences were found between experimental group 1 and the control group.

CONCLUSION

Platelet-rich fibrin, which can be used as an autologous membrane which promotes bone healing, yields better clinical result compared to collagen membranes.

CLINICAL RELEVANCE

Histopathologic evaluation has been carried out regarding the effect of platelet-rich fibrin and collagen membranes applied on bone recovery. Our objective is to contribute to barrier membrane studies that continue to guide and accelerate bone recovery.

Reduction of the relative centrifugal force influences cell number and growth factor release within injectable PRF-based matrices

Platelet rich fibrin (PRF) is a blood concentrate system obtained by centrifugation of peripheral blood. First PRF matrices exhibited solid fibrin scaffold, more recently liquid PRF-based matrix was developed by reducing the relative centrifugation force and time. The aim of this study was to systematically evaluate the influence of RCF (relative centrifugal force) on cell types and growth factor release within injectable PRF- in the range of 60-966 g using consistent centrifugation time. Numbers of cells was analyzed using automated cell counting (platelets, leukocytes, neutrophils, lymphocytes and monocytes) and histomorphometrically (CD 61, CD- 45, CD-15+, CD-68+, CD-3+ and CD-20). ELISA was utilized to quantify the concentration of growth factors and cytokines including PDGF-BB, TGF-β1, EGF, VEGF and MMP-9. Leukocytes, neutrophils, monocytes and lymphocytes had significantly higher total cell numbers using lower RCF. Whereas, platelets in the low and medium RCF ranges both demonstrated significantly higher values when compared to the high RCF group. Histomorphometrical analysis showed a significantly high number of CD61+, CD-45+ and CD-15+ cells in the low RCF group whereas CD-68+, CD-3+ and CD-20+ demonstrated no statistically significant differences between all groups. Total growth factor release of PDGF-BB, TGF-β1 and EGF had similar values using low and medium RCF, which were both significantly higher than those in the high RCF group. VEGF and MMP-9 were significantly higher in the low RCF group compared to high RCF. These findings support the LSCC (low speed centrifugation concept), which confirms that improved PRF-based matrices may be generated through RCF reduction. The enhanced regenerative potential of PRF-based matrices makes them a potential source to serve as a natural drug delivery system. However, further pre-clinical and clinical studies are required to evaluate the regeneration capacity of this system.

Obtention of injectable platelets rich-fibrin (i-PRF) and its polymerization with bone graft: technical note

The use of autologous platelet concentrates, represent a promising and innovator tools in the medicine and dentistry today. The goal is to accelerate hard and soft tissue healing. Among them, the platelet-rich plasma (PRP) is the main alternative for use in liquid form (injectable). These injectable form of platelet concentrates are often used in regenerative procedures and demonstrate good results. The aim of this study is to present an alternative to these platelet concentrates using the platelet-rich fibrin in liquid form (injectable) and its use with particulated bone graft materials in the polymerized form.

Platelet-rich fibrin-based matrices to improve angiogenesis in an in vitro co-culture model for bone tissue engineering

In the context of prevascularization strategies for tissue‐engineering purposes, co‐culture systems consisting of outgrowth endothelial cells (OECs) and primary osteoblasts (pOBs) have been established as a promising in vitro tool to study regeneration mechanisms and to identify factors that might positively influence repair processes such as wound healing or angiogenesis. The development of autologous injectable platelet‐rich fibrin (PRF), which can be generated from peripheral blood in a minimal invasive procedure, fulfils several requirements for clinically applicable cell‐based tissue‐engineering strategies. During this study, the established co‐culture system of OECs and pOBs was mixed with injectable PRF and was cultivated in vitro for 24 h or 7 days. The aim of this study was to analyse whether PRF might have a positive effect on wound healing processes and angiogenic activation of OECs in the co‐culture with regard to proinflammatory factors, adhesion molecules and proangiogenic growth factor expression. Histological cell detection revealed the formation of lumina and microvessel‐like structures in the PRF/co‐culture complexes after 7 days of complex cultivation. Interestingly, the angiogenic activation of OECs was accompanied by an upregulation of wound healing‐associated factors, as well as by a higher expression of the proangiogenic factor vascular endothelial growth factor, which was evaluated both on the mRNA level as well as on the protein level. Thus, PRF might positively influence wound healing processes, in particular angiogenesis, in the in vitro co‐culture, making autologous PRF‐based matrices a beneficial therapeutic tool for tissue‐engineering purposes by simply profiting from the PRF, which contains blood plasma, platelets and leukocytes.

Maxillary sinus augmentation with leukocyte and platelet-rich fibrin and deproteinized bovine bone mineral: A split-mouth histological and histomorphometric study

OBJECTIVES

To evaluate the effect of leukocyte and platelet-rich fibrin (L-PRF) in combination with deproteinized bovine bone mineral (DBBM) on bone regeneration in maxillary sinus augmentation.

MATERIAL AND METHODS

Thirteen patients (nine males and four females, mean age ± SD; 49.92 ± 10.37) were enrolled to the study. 26 maxillary sinus augmentation procedures were randomly performed using DBBM and L-PRF mixture (test) or DBBM alone (control) in a split-mouth design. The same surgical procedures were performed in both groups, and bone biopsies were harvested from the implant sites 6 months postoperatively for histological and histomorphometric evaluations as the primary outcome of the study. Implants were placed and then loaded in the augmented sites after 6 months. The secondary outcomes included clinical and radiographic data and were obtained pre- and postoperatively.

RESULTS

There was no qualitative difference in histological analyses among the groups. In all samples, a newly formed bone was in direct contact with the residual material. The percentages of newly formed bone (test; 21.38 ± 8.78% and control; 21.25 ± 5.59%), residual bone graft (test; 25.95 ± 9.54% and control; 32.79 ± 5.89%), bone graft in contact with the newly formed bone (test; 47.33 ± 12.33% and control; 54.04 ± 8.36%), and soft tissue (test; 52.67 ± 12.53% and control; 45.96 ± 8.36%) were similar among the groups (p < .05). Similar radiographic bone height in the augmented area was observed, and implant survival rate was 100% for both groups.

CONCLUSIONS

Both techniques were effective for maxillary sinus augmentation, and after 6 months of healing, the addition of L-PRF in DBBM did not improve the amount of regenerated bone or the amount of the graft integrated into the newly formed bone under histological and histomorphometric evaluation.

Synergistic effects of the combined use of human-cultured periosteal sheets and platelet-rich fibrin on bone regeneration: An animal study

A human-cultured alveolar bone-derived periosteal (hCP) sheet is an osteogenic grafting material used clinically in periodontal regenerative therapy, while platelet-rich fibrin (PRF), a platelet concentrate with fibrin clot, is considered to augment the wound healing process. Therefore, whether the combined use of hCP-PRF complex could facilitate bone regeneration synergistically was evaluated in animal models. Human periosteal segments (1 × 1 mm) were cultured initially on plastic dishes and formed an hCP sheet. The hCP sheet was implanted with freshly prepared human PRF into subcutaneous tissue (hCP: n = 4, hCP + PRF: n = 4) and 4 mm diameter calvarial bone defect models (hCP: n = 4, hCP + PRF: n = 4, control [defect-only]: n = 4) that prepared in nude mice. At 4 weeks postimplantation, new bone formation was evaluated by using μCT. Cell growth and neovascularization were evaluated by histochemical and immunohistological methods. In the subcutaneous tissue, mineral deposit formation, collagen deposition, and number of vessels were higher in the hCP + PRF group than in the hCP alone group. In the calvarial defect models, new bone formation was significantly higher in the hCP + PRF group than in the hCP alone group and defect-only control group. The numbers of vessels and PCNA-positive cells in calvarial defects were also increased in the hCP + PRF group more than in the hCP alone group. Platelet-rich fibrin preparations support the proliferation and the growth of periosteal cells to form well-combined active biological materials. Platelet-rich fibrin also stimulates the local angiogenesis in the implantation site. Therefore, the combined use of hCP and PRF could be clinically applicable in bone regeneration therapy.

White cell and platelet content affects the release of bioactive factors in different blood-derived scaffolds

Platelet-derived factors are biomaterials that might accelerate healing process in oral, maxillofacial, and several other applications. Release of specific factors by platelet concentrates is critical to achieving a successful outcome. Here, we have shown that platelet-rich fibrin (PRF) clots were beneficial sources of leukocytes, which may directly affect the release of chemokines and growth factors. When compared with the standard leukocyte-PRF (L-PRF), the experimental low-force modified procedure [defined as advanced-PRF (A-PRF)] entrapped the same content of viable leukocytes, released a similar amount of inflammatory cytokines, but secreted 3-, 1.6-, 3-, and 1.2-fold higher levels of Eotaxin, CCL5, platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), respectively. A leukocyte-free scaffold, such as plasma rich in growth factors (PRGF), released only platelet-specific factors and, in particular, the F3 fraction, the richest in growth factors, secreted higher amount of CCL5 and PDGF compared to F1 and F2 fractions. In conclusion, different procedures and leukocyte content affect cytokine, chemokines, and growth factor release from platelet derivatives, which may be helpful in different clinical settings.

Effects of platelet rich plasma (PRP) on human gingival fibroblast, osteoblast and periodontal ligament cell behaviour

BACKGROUND

The use of platelet rich plasma (PRP, GLO) has been used as an adjunct to various regenerative dental procedures. The aim of the present study was to characterize the influence of PRP on human gingival fibroblasts, periodontal ligament (PDL) cells and osteoblast cell behavior in vitro.

METHODS

Human gingival fibroblasts, PDL cells and osteoblasts were cultured with conditioned media from PRP and investigated for cell migration, proliferation and collagen1 (COL1) immunostaining. Furthermore, gingival fibroblasts were tested for genes encoding TGF-β, PDGF and COL1a whereas PDL cells and osteoblasts were additionally tested for alkaline phosphatase (ALP) activity, alizarin red staining and mRNA levels of osteoblast differentiation markers including Runx2, COL1a2, ALP and osteocalcin (OCN).

RESULTS

It was first found that PRP significantly increased cell migration of all cells up to 4 fold. Furthermore, PRP increased cell proliferation at 3 and 5 days of gingival fibroblasts, and at 3 days for PDL cells, whereas no effect was observed on osteoblasts. Gingival fibroblasts cultured with PRP increased TGF-β, PDGF-B and COL1 mRNA levels at 7 days and further increased over 3-fold COL1 staining at 14 days. PDL cells cultured with PRP increased Runx2 mRNA levels but significantly down-regulated OCN mRNA levels at 3 days. No differences in COL1 staining or ALP staining were observed in PDL cells. Furthermore, PRP decreased mineralization of PDL cells at 14 days post seeding as assessed by alizarin red staining. In osteoblasts, PRP increased COL1 staining at 14 days, increased COL1 and ALP at 3 days, as well as increased ALP staining at 14 days. No significant differences were observed for alizarin red staining of osteoblasts following culture with PRP.

CONCLUSIONS

The results demonstrate that PRP promoted gingival fibroblast migration, proliferation and mRNA expression of pro-wound healing molecules. While PRP induced PDL cells and osteoblast migration and proliferation, it tended to have little to no effect on osteoblast differentiation. Therefore, while the effects seem to favor soft tissue regeneration, the additional effects of PRP on hard tissue formation of PDL cells and osteoblasts could not be fully confirmed in the present in vitro culture system.

Use of platelet-rich fibrin in regenerative dentistry: a systematic review

OBJECTIVES

Research across many fields of medicine now points towards the clinical advantages of combining regenerative procedures with platelet-rich fibrin (PRF). This systematic review aimed to gather the extensive number of articles published to date on PRF in the dental field to better understand the clinical procedures where PRF may be utilized to enhance tissue/bone formation.

MATERIALS AND METHODS

Manuscripts were searched systematically until May 2016 and separated into the following categories: intrabony and furcation defect regeneration, extraction socket management, sinus lifting procedures, gingival recession treatment, and guided bone regeneration (GBR) including horizontal/vertical bone augmentation procedures. Only human randomized clinical trials were included for assessment.

RESULTS

In total, 35 articles were selected and divided accordingly (kappa = 0.94). Overall, the use of PRF has been most investigated in periodontology for the treatment of periodontal intrabony defects and gingival recessions where the majority of studies have demonstrated favorable results in soft tissue management and repair. Little to no randomized clinical trials were found for extraction socket management although PRF has been shown to significantly decrease by tenfold dry sockets of third molars. Very little to no data was available directly investigating the effects of PRF on new bone formation in GBR, horizontal/vertical bone augmentation procedures, treatment of peri-implantitis, and sinus lifting procedures.

CONCLUSIONS

Much investigation now supports the use of PRF for periodontal and soft tissue repair. Despite this, there remains a lack of well-conducted studies demonstrating convincingly the role of PRF during hard tissue bone regeneration. Future human randomized clinical studies evaluating the use of PRF on bone formation thus remain necessary.

CLINICAL RELEVANCE

PRF was shown to improve soft tissue generation and limit dimensional changes post-extraction, with little available data to date supporting its use in GBR.

Harnessing macrophage plasticity for tissue regeneration

Macrophages are versatile and plastic effector cells of the immune system, and contribute to diverse immune functions including pathogen or apoptotic cell removal, inflammatory activation and resolution, and tissue healing. Macrophages function as signaling regulators and amplifiers, and influencing their activity is a powerful approach for controlling inflammation or inducing a wound-healing response in regenerative medicine. This review discusses biomaterials-based approaches for altering macrophage activity, approaches for targeting drugs to macrophages, and approaches for delivering macrophages themselves as a therapeutic intervention.

Release kinetics and mitogenic capacity of collagen barrier membranes supplemented with secretome of activated platelets - the in vitro response of fibroblasts of the periodontal ligament and the gingiva

Background

Platelet preparations can stimulate the healing process and have mitogenic properties. We hypothesized that collagen barrier membranes (CBM), clinically used in guided bone regeneration and guided tissue regeneration, can serve as carriers for platelet secretome.

Methods

Secretome was generated from washed platelets and unwashed platelets (washed/unwashed PSEC) and lyophilized onto CBM. Overall appearance of CBM was evaluated by scanning electron microscopy. The impact of PSEC on cell attachment was measured based on fluorescence microscopy with DiI-labeled cells. To assess the release kinetics, supernatants of CBM were collected and medium was replaced at hour 1–48. The mitogenic effect was evaluated with periodontal fibroblasts. Furthermore, the release of total protein, platelet-derived growth factor (PDGF)-BB, and transforming growth factor (TGF) β1 was measured.

Results

CBM overall appearance and cell attachment was not modulated by PSEC. Supernatants taken after one hour induced a mitogenic response in fibroblasts and showed the highest levels of total protein, TGFβ1 and PDGF-BB. These effects decreased rapidly in subsequent supernatants. While supernatants of CBM loaded with unwashed PSEC induced a stronger mitogenic response than supernatants of CBM loaded with washed PSEC this difference between the PSEC preparations was not observed when cells were seeded on 48–hours-washed CBM.

Conclusions

CBM release platelet-derived factors in continuously declining release kinetics.

Reduction of relative centrifugal forces increases growth factor release within solid platelet-rich-fibrin (PRF)-based matrices: a proof of concept of LSCC (low speed centrifugation concept)

Purpose The present study evaluated the platelet distribution pattern and growth factor release (VEGF, TGF-β1 and EGF) within three PRF (platelet-rich-fibrin) matrices (PRF, A-PRF and A-PRF+) that were prepared using different relative centrifugation forces (RCF) and centrifugation times. Materials and methods immunohistochemistry was conducted to assess the platelet distribution pattern within three PRF matrices. The growth factor release was measured over 10 days using ELISA. Results The VEGF protein content showed the highest release on day 7; A-PRF+ showed a significantly higher rate than A-PRF and PRF. The accumulated release on day 10 was significantly higher in A-PRF+ compared with A-PRF and PRF. TGF-β1 release in A-PRF and A-PRF+ showed significantly higher values on days 7 and 10 compared with PRF. EGF release revealed a maximum at 24 h in all groups. Toward the end of the study, A-PRF+ demonstrated significantly higher EGF release than PRF. The accumulated growth factor releases of TGF-β1 and EGF on day 10 were significantly higher in A-PRF+ and A-PRF than in PRF. Moreover, platelets were located homogenously throughout the matrix in the A-PRF and A-PRF+ groups, whereas platelets in PRF were primarily observed within the lower portion. ​Discussion the present results show an increase growthfactor release by decreased RCF. However, further studies must be conducted to examine the extent to which enhancing the amount and the rate of released growth factors influence wound healing and biomaterial-based tissue regeneration. ​Conclusion These outcomes accentuate the fact that with a reduction of RCF according to the previously LSCC (described low speed centrifugation concept), growth factor release can be increased in leukocytes and platelets within the solid PRF matrices.

Reduction of relative centrifugation force within injectable platelet-rich-fibrin (PRF) concentrates advances patients' own inflammatory cells, platelets and growth factors: the first introduction to the low speed centrifugation concept

Purpose

The aim of this study was to analyze systematically the influence of the relative centrifugation force (RCF) on leukocytes, platelets and growth factor release within fluid platelet-rich fibrin matrices (PRF).

Materials and methods

Systematically using peripheral blood from six healthy volunteers, the RCF was reduced four times for each of the three experimental protocols (I–III) within the spectrum (710–44 g), while maintaining a constant centrifugation time. Flow cytometry was applied to determine the platelets and leukocyte number. The growth factor concentration was quantified 1 and 24 h after clotting using ELISA.

Results

Reducing RCF in accordance with protocol-II (177 g) led to a significantly higher platelets and leukocytes numbers compared to protocol-I (710 g). Protocol-III (44 g) showed a highly significant increase of leukocytes and platelets number in comparison to -I and -II. The growth factors’ concentration of VEGF and TGF-β1 was significantly higher in protocol-II compared to -I, whereas protocol-III exhibited significantly higher growth factor concentration compared to protocols-I and -II. These findings were observed among 1 and 24 h after clotting, as well as the accumulated growth factor concentration over 24 h.

Discussion

Based on the results, it has been demonstrated that it is possible to enrich PRF-based fluid matrices with leukocytes, platelets and growth factors by means of a single alteration of the centrifugation settings within the clinical routine.

Conclusions

We postulate that the so-called low speed centrifugation concept (LSCC) selectively enriches leukocytes, platelets and growth factors within fluid PRF-based matrices. Further studies are needed to evaluate the effect of cell and growth factor enrichment on wound healing and tissue regeneration while comparing blood concentrates gained by high and low RCF.

Behavior of Gingival Fibroblasts on Titanium Implant Surfaces in Combination with either Injectable-PRF or PRP

Various strategies have been employed to speed tissue regeneration using bioactive molecules. Interestingly, platelet concentrates derived from a patient's own blood have been utilized as a regenerative strategy in recent years. In the present study, a novel liquid platelet formulation prepared without the use of anti-coagulants (injectable-platelet-rich fibrin, i-PRF) was compared to standard platelet-rich plasma (PRP) with gingival fibroblasts cultured on smooth and roughened titanium implant surfaces. Standard PRP and i-PRF (centrifuged at 700 rpm (60× g) for 3 min) were compared by assays for fibroblast biocompatibility, migration, adhesion, proliferation, as well as expression of platelet-derived growth factor (PDGF), transforming growth factor-β (TGF-β), collagen1 (COL1) and fibronectin (FN). The results demonstrate that i-PRF induced significantly higher cell migration, as well as higher messenger RNA (mRNA) levels of PDGF, TGF-β, collagen1 and fibronectin when compared to PRP. Furthermore, collagen1 synthesis was highest in the i-PRF group. These findings demonstrate that liquid platelet concentrates can be formulated without the use of anticoagulants and present much translational potential for future research. Future animal and clinical trials are now necessary to further investigate the potential of utilizing i-PRF for soft tissue regenerative protocols in combination with various biomaterials.

Comparative evaluation of platelet count and antimicrobial efficacy of injectable platelet-rich fibrin with other platelet concentrates: An in vitro study

Background:

Platelet concentrates are used in various medical procedures to promote soft- and hard-tissue regeneration. In recent times, their antimicrobial efficacy is also explored. However, various platelet concentrates have evolved which differ in the centrifugation protocols. One such recently introduced platelet concentrate is injectable platelet-rich fibrin (i-PRF) concentrate. Hence, the aim was to evaluate the antimicrobial property, and platelet count of i-PRF in comparison to other platelet concentrates, i.e., PRF, platelet-rich plasma (PRP), and control (whole blood).

Materials and Methods:

Blood samples were obtained from 10 chronic generalized marginal gingivitis patients. Platelet concentrates were prepared using standardized centrifugation protocol. Platelet count was evaluated by manual counting method using smear preparation of each sample. Subsequently, antimicrobial activity against oral bacteria was examined on blood agar using disc diffusion method to quantify the inhibitory effects.

Results:

Statistical significance was analyzed by one-way analysis of variance (ANOVA). P <0.05 was considered statistically significant. Mean zone of inhibition around i-PRF (P < 0.01) and PRF (P < 0.05) showed statistical significance. Although a distinct zone of inhibition was seen with PRP, it was not statistically significant (P > 0.05). i-PRF showed statistically significant difference (P < 0.001) in platelet count when compared to control. It was also significant when compared to PRP (P < 0.01), PRF (P < 0.001).

Conclusion:

i-PRF has maximum antimicrobial efficacy and higher platelet count in comparison to other platelet concentrates, thereby indicating to have a better regenerative potential then others.

Basic characteristics of plasma rich in growth factors (PRGF): blood cell components and biological effects

Platelet-rich plasma (PRP) is widely used in regenerative medicine because of its high concentrations of various growth factors and platelets. However, the distribution of blood cell components has not been investigated in either PRP or other PRP derivatives. In this study, we focused on plasma rich in growth factors (PRGF), a PRP derivative, and analyzed the distributions of platelets and white blood cells (WBCs). Peripheral blood samples were collected from healthy volunteers (N = 14) and centrifuged to prepare PRGF and PRP. Blood cells were counted using an automated hematology analyzer. The effects of PRP and PRGF preparations on cell proliferation were determined using human periosteal cells. In the PRGF preparations, both red blood cells and WBCs were almost completely eliminated, and platelets were concentrated by 2.84-fold, whereas in the PRP preparations, both platelets and WBCs were similarly concentrated by 8.79- and 5.51-fold, respectively. Platelet counts in the PRGF preparations were positively correlated with platelet counts in the whole blood samples, while the platelet concentration rate was negatively correlated with red blood cell counts in the whole blood samples. In contrast, platelet counts and concentration rates in the PRP preparations were significantly influenced by WBC counts in whole blood samples. The PRP preparations, but not the PRGF preparations, significantly suppressed cell growth at higher doses in vitro. Therefore, these results suggest that PRGF preparations can clearly be distinguished from PRP preparations by both inclusion of WBCs and dose-dependent stimulation of periosteal cell proliferation in vitro.

Platelet-Rich Fibrin and Soft Tissue Wound Healing: A Systematic Review

The growing multidisciplinary field of tissue engineering aims at predictably regenerating, enhancing, or replacing damaged or missing tissues for a variety of conditions caused by trauma, disease, and old age. One area of research that has gained tremendous awareness in recent years is that of platelet-rich fibrin (PRF), which has been utilized across a wide variety of medical fields for the regeneration of soft tissues. This systematic review gathered all the currently available in vitro, in vivo, and clinical literature utilizing PRF for soft tissue regeneration, augmentation, and/or wound healing. In total, 164 publications met the original search criteria, with a total of 48 publications meeting inclusion criteria (kappa score = 94%). These studies were divided into 7 in vitro, 11 in vivo, and 31 clinical studies. In summary, 6 out of 7 (85.7%) and 11 out of 11 (100%) of the in vitro and in vivo studies, respectively, demonstrated a statistically significant advantage for combining PRF to their regenerative therapies. Out of the remaining 31 clinical studies, a total of 8 reported the effects of PRF in a randomized clinical trial, with 5 additional studies (13 total) reporting appropriate controls. In those clinical studies, 9 out of the 13 studies (69.2%) demonstrated a statistically relevant positive outcome for the primary endpoints measured. In total, 18 studies (58% of clinical studies) reported positive wound-healing events associated with the use of PRF, despite using controls. Furthermore, 27 of the 31 clinical studies (87%) supported the use of PRF for soft tissue regeneration and wound healing for a variety of procedures in medicine and dentistry. In conclusion, the results from the present systematic review highlight the positive effects of PRF on wound healing after regenerative therapy for the management of various soft tissue defects found in medicine and dentistry.