Platelet-rich fibrin (PRF): a second-generation platelet concentrate. Part II: platelet-related biologic features.

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, TGFbeta-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.     

Platelet-rich fibrin (PRF): a second-generation platelet concentrate. Part III: leucocyte activation: a new feature for platelet concentrates?

Platelet-rich fibrin (PRF) belongs to a new generation of platelet concentrates, with simplified processing and without biochemical blood handling. In this third article, we investigate the immune features of this biomaterial. During PRF processing, leucocytes could also secrete cytokines in reaction to the hemostatic and inflammatory phenomena artificially induced in the centrifuged tube. We therefore undertook to quantify 5 significant cell mediators within platelet poor plasma supernatant and PRF clot exudate serum: 3 proinflammatory cytokines (IL-1beta, IL-6, and TNF-alpha), an antiinflammatory cytokine (IL-4), and a key growth promoter of angiogenesis (VEGF). Our data are correlated with that obtained in plasma (nonactivated blood) and in sera (activated blood). These initial analyses revealed that PRF could be an immune regulation node with inflammation retrocontrol abilities. This concept could explain the reduction of postoperative infections when PRF is used as surgical additive.     

Platelet-rich fibrin (PRF): a second-generation platelet concentrate. Part IV: clinical effects on tissue healing.

Platelet-rich fibrin (PRF) belongs to a new generation of platelet concentrates, with simplified processing and without biochemical blood handling. In this fourth article, investigation is made into the previously evaluated biology of PRF with the first established clinical results, to determine the potential fields of application for this biomaterial. The reasoning is structured around 4 fundamental events of cicatrization, namely, angiogenesis, immune control, circulating stem cells trapping, and wound-covering epithelialization. All of the known clinical applications of PRF highlight an accelerated tissue cicatrization due to the development of effective neovascularization, accelerated wound closing with fast cicatricial tissue remodelling, and nearly total absence of infectious events. This initial research therefore makes it possible to plan several future PRF applications, including plastic and bone surgery, provided that the real effects are evaluated both impartially and rigorously.     

Platelet-rich fibrin (PRF): a second-generation platelet concentrate. Part V: histologic evaluations of PRF effects on bone allograft maturation in sinus lift.

OBJECTIVE: Platelet-rich fibrin (PRF) belongs to a new generation of platelet concentrates, with simplified processing and without biochemical blood handling. The use of platelet gel to improve bone regeneration is a recent technique in implantology. However, the biologic properties and real effects of such products remain controversial. In this article, we therefore attempt to evaluate the potential of PRF in combination with freeze-dried bone allograft (FDBA) (Phoenix; TBF, France) to enhance bone regeneration in sinus floor elevation. STUDY DESIGN: Nine sinus floor augmentations were performed. In 6 sites, PRF was added to FDBA particles (test group), and in 3 sites FDBA without PRF was used (control group). Four months later for the test group and 8 months later for the control group, bone specimens were harvested from the augmented region during the implant insertion procedure. These specimens were treated for histologic analysis. RESULTS: Histologic evaluations reveal the presence of residual bone surrounded by newly formed bone and connective tissue. After 4 months of healing time, histologic maturation of the test group appears to be identical to that of the control group after a period of 8 months. Moreover, the quantities of newly formed bone were equivalent between the 2 protocols. CONCLUSIONS: Sinus floor augmentation with FDBA and PRF leads to a reduction of healing time prior to implant placement. From a histologic point of view, this healing time could be reduced to 4 months, but large-scale studies are still necessary to validate these first results.     

Basic studies on the clinical applications of platelet-rich plasma

Platelets, which contain many growth factors such as platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta), are being used in clinical applications as platelet-rich plasma (PRP). Only a few studies, however, have been conducted on the growth factors present in PRP and on the clinical applications using the drug delivery system (DDS). For the purpose of clinical application, we first modified the PRP preparation method and assessed the amounts of growth factors contained in the human platelet concentrates. Furthermore, we assessed fibrin glue as a DDS of platelet concentrates. Platelet precipitations were made by twice centrifuging human whole blood. The precipitated platelet was resuspended to yield the platelet concentrates. The growth factor concentrations were measured. Fibrin glue sheets containing this platelet concentrate were implanted in rabbit pinna and samples were obtained for immunostaining (anti-PDGF antibody) to assess the use of PRP over time using the fibrin glue as the DDS. The mean concentration of growth factors present in the platelet concentrates was three times or greater than that of conventional PRP. Furthermore, the results indicated that when the platelet concentrate was used with fibrin glue as a carrier, the contents were released over a period of about 1 week. This raises the possibility that this system may be useful in clinical applications.     

Bioactivity and stability of endogenous fibrogenic factors in platelet-rich fibrin

Platelet‐rich fibrin (PRF^®) is an autologous fibrin sealant (FS) enriched with a platelet concentrate (>1,000,000 platelets/μL) produced by the automated Vivostat^® system and used to enhance wound healing. The effects of PRF were compared with supernatant from thrombin‐activated platelet concentrate, recombinant human platelet‐derived growth factor (rhPDGF) isoforms, and a homologous FS in cultured normal human dermal fibroblasts. Also, the release of selected endogenous growth factors from PRF and their stability against proteolytic degradation were studied. The proliferative effect of PRF exceeded that of FS and rhPDGF‐BB, although it was lower than thrombin‐activated platelet concentrate possibly due to sustained growth factor release from platelets in PRF. Anti‐PDGF antibody blocked the mitogenic effect of rhPDGF‐BB but not that of PRF in growth‐arrested fibroblasts. PRF promoted secretion of carboxyterminal propeptide of type I collagen into conditioned medium while rhPDGF‐AB had no significant effect on collagen biosynthesis. Limited proteolysis of PDGF‐AB and no proteolysis of transforming growth factor‐β1 (TGF‐β1) in PRF were observed with trypsin treatment, whereas rhPDGF‐AB and rhTGF‐β1 in bovine serum albumin, matching the total protein concentration of PRF, were almost completely degraded after 24 hours at 37 °C. To conclude, PRF provides sustained release and protection against proteolytic degradation of endogenous fibrogenic factors important for wound healing.     

PRF促进急性创面愈合的研究进展

伤口愈合很大程度上依赖于机体自身的修复能力,而组织损伤会激活多种细胞分泌生长因子参 与炎症反应过程,调节蛋白质和其他细胞成分的合成、分解,从而促进细胞增殖、基质形成、血管再生 及肉芽形成,达到创面修复的目的。富血小板纤维蛋白（PRF）是第二代血小板浓缩物,与富血小板血 浆（PRP）不同,PRF制备时未加入抗凝剂和其他化学成分,有效避免了过敏反应。PRF富含生长因子, 可持续释放生长因子至少1周以上,同时具有良好的立体纤维蛋白空间结构,可为创面提供理想的细胞支 架,能有效促使细胞迁移和增殖,从而达到促进创面愈合的作用。本文为探究PRF促进急性创面愈合的研 究进展,现就伤口愈合过程、PRF应用于急性伤口愈合时的作用机制作一综述。     

Preclotting of knitted Dacron prosthesis. A scanning electron microscope study.

A scanning electron microscope study of preclotting on knitted Dacron prosthesis is reported. Five steps of the interaction are well identified: (1) before any blood contact (virgin Dacron), (2) during the first 3 minutes (fibrin and platelet aggregates), (3) fifth minute of contact (clotting), (4) 15 minutes of contact with heparinized blood (thin fibrin network), and (5) the following minutes (invasion of fibrin, which enmeshes blood cells).     

New approach in vaginal prolapse repair: mini-invasive surgery associated with application of platelet-rich fibrin

Introduction and hypothesis

Platelet-rich fibrin (PRF) matrix is an autologous leukocyte and PRF biomaterial. PRF is a fibrin matrix polymerized in a tetramolecular structure with the incorporation of platelets, leukocytes, cytokines, and circulating stem cells. The three-dimensional structure of PRF is optimal for migration of endothelial cells and fibroblasts. It permits rapid angiogenesis and easier remodeling of fibrin in a more resistant connective matrix. In vaginal surgery, PRF may act as a graft material with better healing and better functional outcome.

Methods

We performed a prospective observational study on ten consecutive women requiring surgery for prolapse recurrence (stage II or higher). These women had high risks for recurrence, erosion with graft materials, and intraoperative and postoperative complications with traditional pelvic reconstructive surgical procedures. ICS score and P-QoL Questionnaire results were assessed preoperatively and postoperatively. Surgery consisted of anterior, posterior, or apical repair plus PRF. Follow-up was performed at 1, 6, 12, 18, and 24?months.

Results

Anatomically, the success rate was 80%. Prolapse symptoms improved by 100%. Sexual activity increased by 20% without dyspareunia. The surgical time was satisfactory (mean, 38.5?min). There were no intraoperative or postoperative complications.

Conclusions

The use of PRF for site-specific prolapse repair is associated with a good functional outcome because of the healing and mechanical properties of PRF.     

Efficacy of platelet rich fibrin in the reduction of the pain and swelling after impacted third molar surgery: Randomized multicenter split-mouth clinical trial

Background

Impacted third molar removal is a routine procedure in oral and maxillofacial surgery. Platelet-rich fibrin (PRF) is a second generation platelet concentration which is produced by simplified protocol. The aim of this study was to assess the effectiveness of PRF in the healing process by evaluating the changes in pain and swelling after third molar surgery.

Methods

Fifty-six patients (23 male, 33 female) who provide the inclusion criteria were selected to participate in this study. The evaluation of the facial swelling was performed by using a horizontal and vertical guide. The pain was evaluated in the postoperative period using a visual analog scale (VAS) of 100 mm.

Results

Horizontal and vertical measurements showed more swelling at the control side (without PRF) in 3th day postoperatively (p?<?0.05). There were no statistically significant differences regarding pain among the groups.

Conclusion

As a conclusion, PRF seems to be effectiveness on postoperative horizontal swelling after third molar surgery. PRF could be used on a routine basis after third molar extraction surgery.

     

Use of autologous platelet rich fibrin in urethracutaneous fistula repair: preliminary report

Urethrocutaneous fistula (UCF) is one of the most common complications occurring after hypospadias repair. Despite the surgical advancement in hypospadias, multiple failed fistula closures are commonly referred to paediatric urologists. Although several techniques have been described to interpose a waterproof layer between urethral and skin closures, occurrence of urethrocutaneous fistula cannot be eliminated completely. In addition to several local tissue grafts, autologous and homologous fibrin sealants are used to prevent UCF. Platelet rich fibrin (PRF) is known as an autologous source of growth factors obtained from the sera of the patient. PRF supports collagen synthesis and tissue repair and accelerates wound healing. We aimed to present our initial experience about the use of autologous PRF in a 3‐year‐old boy with a UCF after hypospadias repair.     

Evaluation of the effect of pharmacologic agents on crush-avulsion arterial injuries: a scanning electron microscopy study.

This study was designed to investigate the short-term formation and composition of thrombus occurring at sites of arterial intimal injury in rabbits. Anti-coagulants, platelet anti-aggregation agents, and fibrinolytic agents were evaluated for their influence upon the developing thrombus, utilizing scanning electron microscopy to determine thrombus surface composition. These agents included: heparin, aspirin, dextran 40, streptokinase, and prostacyclin. The results are consistent with the known nature of each of these agents. When two agents were given simultaneously, each acting on different aspects of thrombogenesis (platelets vs. fibrin), the outcome appeared synergistic, with substantial reduction in thrombus accumulation; clear inhibition of both platelet aggregation and fibrin polymerization was noted. These findings support the clinical use of two agents used simultaneously, one inhibiting fibrin strand formation and the other inhibiting platelet adherence aggregation, for the prevention of micro-arterial thrombosis.     

血小板减少时纤维蛋白原水平对血栓弹力测定参数的影响

背景 纤维蛋白原及纤维蛋白与血小板的结合,在正常的止血过程中发挥着重要作用.血小板-纤维蛋白相互作用的程度可通过旋转式血栓弹力测定法(ROTEM)测量血凝块粘弹性的强度进行评估.在本试验中,我们研究了纤维蛋白原浓度对ROTEM测得整体血凝强度的影响及其发挥的作用.方法 采集健康志愿者的血样作为研究样品.通过ROTEM检...     

Whole blood thrombin: development of a process for intra-operative production of human thrombin

Thrombin-based clotting agents currently used for topical hemostasis with absorbable sponges, fibrin sealants, and platelet gels are primarily derived from bovine or pooled human plasma sources. Autologous thrombin has important safety advantages in that it does not carry the same safety concerns as pooled plasma-derived products and it avoids exposure to risks associated with bovine-derived proteins. The goal of our research was to develop a rapid, reliable, and simple to perform process to generate autologous human thrombin in the intraoperative setting, from patient whole blood as the starting source material. Using whole blood instead of plasma as the starting material, it is possible to avoid the inherent delay in thrombin availability associated with a primary step of plasma isolation. In this study, we varied several key processing parameters to maximize thrombin production, reproducibility and stability. Autologous thrombin production was generated using a dedicated, single use disposable with a sterile reagent. The disposable consists of a tubular reaction chamber containing glass microsphere beads to activate the alternative pathway of the coagulation cascade. At the end of the process, thrombin-activated serum was harvested from the reaction chamber. The average activity of the thrombin produced at room temperature by this system was 82.8 +/- 15.9 IU/mL. The total processing time was < 30 minutes. The system was compatible with Anticoagulant Citrate Dextrose-Solution A (ACD-A) (8%-12%). The average volume of thrombin harvested from each aliquot of blood was 7.0 +/- 0.3 mL, and the stability of thrombin was observed to be temperature dependent, with cold storage better preserving thrombin activity. Clot times with platelet concentrates at 1:4.3 and 1:11 ratios (thrombin to platelet concentrate) were < 10 and 20 seconds, respectively. A process for the preparation of thrombin from whole blood, under conditions compatible with the resources of an operating room, has been developed. The device is simple to use, requires 30 minutes, and can consistently produce thrombin solutions that achieve rapid clotting of platelet concentrates, plasma, and fibrinogen concentrates even when mixed at thrombin to blood product ratios of 1:11.     

Platelet-rich fibrin as an alternative adjunct to tendon-exposed wound healing: A randomized controlled clinical trial

BackgroundThe use of platelet-rich fibrin (PRF) has attracted great interest in the treatment of oral and maxillofacial procedures, gingival recessions, and bone healing. However, PRF has been reported hardly to prepare wound bed before skin grafting. This randomized clinical study sought to identify the effect of PRF as an alternative adjunct to tendon-exposed wound healing.MethodsThirty-six patients with tendon-exposed wounds were treated by applying Integra or PRF (n = 18 per group). The take rate of Integra or PRF and pain levels assessed with the four-point verbal rating scale (VRS-4) for the first 5 days after application were measured for each condition. Data of texture change analysis were assessed and recorded for a duration of 3 months postoperatively.ResultsThe take rate was less in the Integra group than in the PRF group (92.39 vs 97.83 P < 0.001). After surgery, compared to the Integra group, the patients in the PRF group reported significantly lower pain scores (P < 0.001). Texture changes from the Integra group were rated higher than those from the PRF (P < 0.001).ConclusionThe use of PRF could be an option for tendon exposed areas where the wound is unfit for standard skin grafting or flap transfer.     

Assessment of the resonance thromboelastograph CS-3 for differentiation of coagulation disorders: a pilot in vitro investigation of simulated post-cardiopulmonary bypass coagulopathies.

Resonance thromboelastography (RTG), a further development of the thromboelastogram (TEG), has been designed for improved differentiation of the effect of the plasmatic coagulation factors (increasing F-leg) and platelets (decreasing P-leg) on clot formation. It is based on the effect of clot elasticity on the resonance of a swinging wire. We assessed the RTG for its ability to differentiate coagulation disorders that frequently occur after cardiac surgery. The RTG was performed with a CS-3 Analyzer. Samples from 10 healthy volunteers were investigated after the following preparations: (1) baseline values, (2) dilution to a hematocrit of 30% and 20% with either hydroxyl ethyl starch (HES) 10% or plasma; (3) addition of 0.25, 0.5, and 1.0 IU/mL porcine heparin with and without heparinase; and (4) addition of 1.0, 3.0, 4.0, and 5.0 microg/mL of the antiplatelet agent abciximab (ReoPro). Increasing concentrations of abciximab led to a slower decrease or in the case of higher concentrations, to a persistent elevation of the platelet leg of the RTG. Dilution of the hematocrit with plasma had no effect on the fibrin and platelet leg; whereas, dilution with HES 10% led to an inhibition of the fibrin and platelet leg. Dilution of the plasmatic coagulation factors resulted in an inhibition of both the fibrin and the platelet leg. The addition of 0.25 and 0.5 IU/mL of heparin led to an increased coagulation time and inhibition of the fibrin and platelet legs. These effects were eliminated by the addition of heparinase. The RTG enables the evaluation of platelet function under the condition of a nonimpaired plasma coagulation system. Depletion of plasma coagulation factors and the administration of small amounts of heparin do not enable the distinction between residual effects of an anticoagulant, coagulation factor deficiency, or impaired platelet function. However, the heparin effects can be eliminated by the addition of heparinase. Further improvement may be achieved using a modified RTG by adding plasma coagulation factors in one channel for an improved evaluation of platelet function, even under the condition of a loss of procoagulants.     

Rapid polymerizing fibrin glue from autologous or single-donor blood: preparation and indications.

A recipe for the preparation of a rapid polymerizing fibrin glue from single-donor or autologous blood products is presented. An in vitro investigation of different recipes with study of polymerization times, consistency, and in vitro survival of the product is described. The preparation in the operating room and the indications for clinical use of this glue in neurosurgery are discussed. The results of its use in a series of 38 patients is presented, including those undergoing surgery of the skull base, pituitary gland, cranial nerves, and the spine.     

Platelet-rich fibrin (PRF) in implant dentistry in combination with new bone regenerative technique in elderly patients

IntroductionSome studies have demonstrated that platelet rich fibrin (PRF) is a healing biomaterial with a great potential for bone and soft tissue regeneration, without any inflammatory reactions and may be used alone or in combination with bone grafts, promoting hemostasis, bone growth, and maturation. PRF appears as a natural and satisfactory aid in bone regenerative surgery in elderly patients with favorable results and low risks.AimThis study wants to demonstrate how PRF in association with a new split crest augmentation technique can be a great aid in implant rehabilitation, especially in the elderly patients, when bone regeneration is required.Materials and methodsTen patients were treated in this study, five following the flapless split crest new procedure and other five patients following traditional procedure without split crest as control. Five patients with an average age between 50 and 60 years were selected to be operated with a split crest flapless modified technique in order to optimize the regenerative conditions with a bone augmentation and implant insertion in one single stage procedure. For all the patients autologous PRF has been used to fill the split crest gap or simply as regenerative material. Orthopantomography, intraoral radiography and CT DentaScan/CT Cone beam were performed for every patient before the treatment and at follow-up time exeption made for CT.ResultsAll cases were successful, there were no problems at surgery time, at post-operative and at osteointegration periods. All implants achieved osteointegration. These results were obtained by accurately managing immediate and late post operative period in all of the operated cases. Mean difference for height bone loss between the two groups of patients was 2.4 mm at T1 and 2.2 mm at T3.DiscussionThe rationale of this split crest flapless modified technique is to obtain a proper buccal cortex expansion preserving its vascular supply avoiding periosteal elevation for better cortical bone nourishing. Moreover, advantages are reported related to the use of PRF. The effectiveness of PRF is shown in promoting the healing of surgical wounds, it has, in fact, platelet growth factors that can improve the vascularisation of the surgical site, promoting neoangiogenesis. Furthermore, by simply changing the settings of the centrifuge, it is possible to obtain a normal gelling if it has to be used as regenerative and stimulating material, or more consistent substance to be used as a filler in the split crest gap.ConclusionsThe main advantages in using the platelet-rich fibrin are healing and bone regenerative properties in combination with its complete resorption after surgery, thus avoiding a second surgery time, important factor in the elderly patients. Currently, it is a minimally invasive technique with low risks and satisfactory clinical results such preventing complications or implant failure particularly in elderly patients for age related conditions.     

Early versus delayed heparin reversal after carotid endarterectomy in the dog. A scanning electron microscopy study

The present study investigates the hematological reaction to arterial injury during the first 10 minutes after endarterectomy in dogs to determine if heparin reversal during this early period predisposes to thrombus formation. Known platelet physiology would predict that heparinization during this early period would be useful to allow a fibrin-free platelet monolayer to form. After systemic heparinization (145 mu/kg) of the experimental animals, 42 endarterectomies were performed. Blood flow was then resumed for specific periods of time, and the vessels were prepared for scanning electron microscopy. Group 1 vessels (from the unheparinized control group) revealed mural thrombus formation after 10 minutes of blood flow. Group 2 vessels revealed the progressive formation of a fibrin-free platelet monolayer after 2, 5, or 10 minutes of blood flow resumption under systemic heparinization. Group 3 arteries, harvested at 10 minutes, underwent immediate (within 1 to 2 minutes after resumption of flow) heparin reversal with protamine sulfate, and demonstrated numerous patches of fibrin covering the platelet monolayer. Group 4 arteries, studied after 3 hours of blood flow, also underwent immediate heparin reversal. Two of these seven specimens had clumps of fibrin overlying the platelet monolayer. The Group 5 vessels had heparin reversal at 10 minutes, and demonstrated no fibrin overlying the platelet monolayer after 3 hours of blood flow. This study demonstrates the formation of a fibrin-free platelet monolayer over the endarterectomized vessel wall within 10 minutes of resumption of flow under systemic heparinization. These findings suggest that heparin may safely be reversed following a carotid endarterectomy if one awaits the initial critical 10 minutes of blood flow.     

Platelet-rich plasma and platelet gel: a review

Strategies to reduce blood loss and transfusion of allogeneic blood products during surgical procedures are important in modern times. The most important and well-known autologous techniques are preoperative autologous predonation, hemodilution, perioperative red cell salvage, postoperative wound blood autotransfusion, and pharmacologic modulation of the hemostatic process. At present, new developments in the preparation of preoperative autologous blood component therapy by whole blood platelet-rich plasma (PRP) and platelet-poor plasma (PPP) sequestration have evolved. This technique has been proven to reduce the number of allogeneic blood transfusions during open heart surgery and orthopedic operations. Moreover, platelet gel and fibrin sealant derived from PRP and PPP mixed with thrombin, respectively, can be exogenously applied to tissues to promote wound healing, bone growth, and tissue sealing. However, to our disappointment, not many well-designed scientific studies are available, and many anecdotic stories exist, whereas questions remain to be answered. We therefore decided to study perioperative blood management in more detail with emphasis on the application and production of autologous platelet gel and the use of fibrin sealant. This review addresses a large variety of aspects relevant to platelets, platelet-rich plasma, and the application of platelet gel. In addition, an overview of recent animal and human studies is presented.