Liquid PRF Reduces the Inflammatory Response and Osteoclastogenesis in Murine Macrophages

Immunoregulatory role of platelet derivatives in the macrophage-mediated immune response

Background

Macrophages are innate immune cells that display remarkable phenotypic heterogeneity and functional plasticity. Due to their involvement in the pathogenesis of several human conditions, macrophages are considered to be an attractive therapeutic target. In line with this, platelet derivatives have been successfully applied in many medical fields and as active participants in innate immunity, cooperation between platelets and macrophages is essential. In this context, the aim of this review is to compile the current evidence regarding the effects of platelet derivatives on the phenotype and functions of macrophages to identify the advantages and shortcomings for feasible future clinical applications.

Methods

A total of 669 articles were identified during the systematic literature search performed in PubMed and Web of Science databases.

Results

A total of 27 articles met the inclusion criteria. Based on published findings, platelet derivatives may play an important role in inducing a dynamic M1/M2 balance and promoting a timely M1-M2 shift. However, the differences in procedures regarding platelet derivatives and macrophages polarization and the occasional lack of information, makes reproducibility and comparison of results extremely challenging. Furthermore, understanding the differences between human macrophages and those derived from animal models, and taking into account the peculiarities of tissue resident macrophages and their ontogeny seem essential for the design of new therapeutic strategies.

Conclusion

Research on the combination of macrophages and platelet derivatives provides relevant information on the function and mechanisms of the immune response.

How to explain the beneficial effects of leukocyte- and platelet-rich fibrin

The survival of an organism relies on its ability to repair the damage caused by trauma, toxic agents, and inflammation. This process involving cell proliferation and differentiation is driven by several growth factors and is critically dependent on the organization of the extracellular matrix. Since autologous platelet concentrates (APCs) are fibrin matrices in which cells, growth factors, and cytokines are trapped and delivered over time, they are able to influence that response at different levels. The present review thoroughly describes the molecular components present in one of these APCs, leukocyte- and platelet-rich fibrin (L-PRF), and summarizes the level of evidence regarding the influence of L-PRF on anti-inflammatory reactions, analgesia, hemostasis, antimicrobial capacity, and its biological mechanisms on bone/soft tissue regeneration.

The Implications of Brain-Derived Neurotrophic Factor in the Biological Activities of Platelet-Rich Plasma

Platelet-rich plasma (PRP) is a biological blood-derived therapeutic obtained from whole blood that contains higher levels of platelets. PRP has been primarily used to mitigate joint degeneration and chronic pain in osteoarthritis (OA). This clinical applicability is based mechanistically on the release of several proteins by platelets that can restore joint homeostasis. Platelets are the primary source of brain-derived neurotrophic factor (BDNF) outside the central nervous system. Interestingly, BDNF and PRP share key biological activities with clinical applicability for OA management, such as anti-inflammatory, anti-apoptotic, and antioxidant. However, the role of BDNF in PRP therapeutic activities is still unknown. Thus, this work aimed to investigate the implications of BDNF in therapeutic outcomes provided by PRP therapy in vitro and in-vivo, using the MIA-OA animal model in male Wistar rats. Initially, the PRP was characterized, obtaining a leukocyte-poor-platelet-rich plasma (LP-PRP). Our assays indicated that platelets activated by Calcium release BDNF, and suppression of M1 macrophage polarization induced by LP-PRP depends on BDNF full-length receptor, Tropomyosin Kinase-B (TrkB). OA animals were given LP-PRP intra-articular and showed functional recovery in gait, joint pain, inflammation, and tissue damage caused by MIA. Immunohistochemistry for activating transcriptional factor-3 (ATF-3) on L4/L5 dorsal root ganglia showed the LP-PRP decreased the nerve injury induced by MIA. All these LP-PRP therapeutic activities were reversed in the presence of TrkB receptor antagonist. Our results suggest that the therapeutic effects of LP-PRP in alleviating OA symptoms in rats depend on BDNF/TrkB activity.

Evaluating the efficacy of platelet-rich plasma on orthodontic tooth movement rate: A systematic review and meta-analysis

BACKGROUND

The main objective of this study was to evaluate the effect of autologous platelet-rich plasma (PRP) on acceleration of the orthodontic tooth movement and assess the evidence based on the available literature.

METHODS

The trial was registered and reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Electronic databases including PubMed, Cochrane, Scopus, Central Register of Controlled Trials, and Google Scholar were searched for randomized controlled studies of PRP on the rate of tooth movement. The search was restricted to articles published in English between January 2000 to 31 December 2023. The search was completed by two reviewers independently and the risk of bias was evaluated using the Cochrane Risk of Bias tool (RoB 2.0) and meta-analysis was performed. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was done to determine the certainty of evidence.

RESULTS

Thirteen studies were included in the systematic review and 10 were included in the quantitative analysis. A random-effects model for meta-analysis of seven studies evaluating the rate of canine retraction revealed a statistically significant increase in the rate of orthodontic tooth movement of 0.38 mm/month in 1 month (121 patients; 95% confidence interval [CI] 0.27-0.49; I2 = 35%; P < 0.001) which decreased to 0.09mm/month in the fourth month (80 patients; 95% CI 0.02-0.17; I2 = 0%; P < 0.02). Three studies that considered en masse retraction revealed a mean difference of 0.36mm over 3 months (40 patients; 95% CI -0.23 to 0.94; I2 = 74%; P < 0.23).

CONCLUSIONS

The study suggests that PRP application can accelerate tooth movement, but its effects decreased over 4 months. The results should be interpreted cautiously due to the study's inherent limitations.

A Macrophage Membrane-Functionalized, Reactive Oxygen Species-Activatable Nanoprodrug to Alleviate Inflammation and Improve the Lipid Metabolism for Atherosclerosis Management

Atherosclerosis (AS) management typically relies on therapeutic drug interventions, but these strategies typically have drawbacks, including poor site specificity, high systemic intake, and undesired side effects. The field of cell membrane camouflaged biomimetic nanomedicine offers the potential to address these challenges thanks to its ability to mimic the natural properties of cell membranes that enable enhanced biocompatibility, prolonged blood circulation, targeted drug delivery, and evasion of immune recognition, ultimately leading to improved therapeutic outcomes and reduced side effects. In this study, a novel biomimetic approach is developed to construct the M1 macrophage membrane-coated nanoprodrug (MM@CD-PBA-RVT) for AS management. The advanced MM@CD-PBA-RVT nanotherapeutics are proved to be effective in inhibiting macrophage phagocytosis and facilitating the cargo delivery to the activated endothelial cells of AS lesion both in vitro and in vivo. Over the 30-day period of nanotherapy, MM@CD-PBA-RVT is capable of significantly inhibiting the progression of AS, while also maintaining a favorable safety profile. In conclusion, the biomimetic MM@CD-PBA-RVT shows promise as feasible drug delivery systems for safe and effective anti-AS applications.

Platelet-rich fibrin as an autologous biomaterial for bone regeneration: mechanisms, applications, optimization

Platelet-rich fibrin, a classical autologous-derived bioactive material, consists of a fibrin scaffold and its internal loading of growth factors, platelets, and leukocytes, with the gradual degradation of the fibrin scaffold and the slow release of physiological doses of growth factors. PRF promotes vascular regeneration, promotes the proliferation and migration of osteoblast-related cells such as mesenchymal cells, osteoblasts, and osteoclasts while having certain immunomodulatory and anti-bacterial effects. PRF has excellent osteogenic potential and has been widely used in the field of bone tissue engineering and dentistry. However, there are still some limitations of PRF, and the improvement of its biological properties is one of the most important issues to be solved. Therefore, it is often combined with bone tissue engineering scaffolds to enhance its mechanical properties and delay its degradation. In this paper, we present a systematic review of the development of platelet-rich derivatives, the structure and biological properties of PRF, osteogenic mechanisms, applications, and optimization to broaden their clinical applications and provide guidance for their clinical translation.

How to explain the beneficial effects of platelet-rich plasma

Platelet-rich plasma (PRP) is the platelet and leukocyte-containing plasmatic fraction of anticoagulated autologous blood. While evidence supporting the clinical use of PRP in dentistry is low, PRP is widely used in sports medicine, orthopedics, and dermatology. Its beneficial activity is commonly attributed to the growth factors released from platelets accumulating in PRP; however, evidence is indirect and not comprehensive. There is thus a demand to revisit PRP with respect to basic and translational science. This review is to (i) recapitulate protocols and tools to prepare PRP; (ii) to discuss the cellular and molecular composition of PRP with a focus on platelets, leukocytes, and the fibrin-rich extracellular matrix of coagulated plasma; and finally (iii) to discuss potential beneficial effects of PRP on a cellular and molecular level with an outlook on its current use in dentistry and other medical fields.

Treatment of a fractured humerus and partially torn supraspinatus tendon in a professional boxer with liquid platelet-rich fibrin and heat-coagulated albumin gel: a case report

INTRODUCTION

Fractures with delayed healing can be a serious complication, especially for athletes depending on quick return to sports. To our knowledge, no cases of increased healing of delayed union fractures with autologous biomedical interventions have been reported.

CASE PRESENTATION

A 33-year-old Swedish professional boxer with a fractured humerus with a delayed union and a partially torn supraspinatus tendon was treated with injections of liquid platelet-rich fibrin and heat-coagulated albumin gel. He recovered almost completely from both injuries in only 1 month and could return to professional boxing in 3 months.

CONCLUSION

This case raises the hypothesis that liquid platelet-rich fibrin and heat-coagulated albumin gel may be an effective, minimally invasive intervention in fractures with a delayed union. Further research is required to test this theory.

Extended platelet-rich fibrin

Platelet-rich fibrin (PRF) has been characterized as a regenerative biomaterial that is fully resorbed within a typical 2-3 week period. Very recently, however, a novel heating process was shown to extend the working properties of PRP/PRF from a standard 2-3 week period toward a duration of 4-6 months. Numerous clinicians have now utilized this extended-PRF (e-PRF) membrane as a substitute for collagen barrier membranes in various clinical applications, such as guided tissue/bone regeneration. This review article summarizes the scientific work to date on this novel technology, including its current and future applications in periodontology, implant dentistry, orthopedics and facial aesthetics. A systematic review was conducted investigating key terms including "Bio-Heat," "albumin gel," "albumin-PRF," "Alb-PRF," "extended-PRF," "e-PRF," "activated plasma albumin gel," and "APAG" by searching databases such as MEDLINE, EMBASE and PubMed. Findings from preclinical studies demonstrate that following a simple 10-min heating process, the transformation of the liquid plasma albumin layer into a gel-like injectable albumin gel extends the resorption properties to at least 4 months according to ISO standard 10 993 (subcutaneous animal model). Several clinical studies have now demonstrated the use of e-PRF membranes as a replacement for collagen membranes in GTR/GBR procedures, closing lateral windows in sinus grafting procedures, for extraction site management, and as a stable biological membrane during recession coverage procedures. Furthermore, Alb-PRF may also be injected as a regenerative biological filler that lasts extended periods with advantages in joint injections, osteoarthritis and in the field of facial aesthetics. This article highlights the marked improvement in the stability and degradation properties of the novel Alb-PRF/e-PRF technology with its widespread future potential use as a potential replacement for collagen membranes with indications including extraction site management, GBR procedures, lateral sinus window closure, recession coverage among others, and further highlights its use as a biological regenerative filler for joint injections and facial aesthetics. It is hoped that this review will pioneer future opportunities and research development in the field, leading to further progression toward more natural and less costly biomaterials for use in medicine and dentistry.

Praeruptorin A inhibits the activation of NF-κB pathway and the expressions of inflammatory factors in poly (I:C)-induced RAW264.7 cells

Praeruptorin A (PA), a natural coumarin compound, has significant anti-inflammatory effects. In this study, we evaluate the anti-inflammatory effect of PA on RAW 264.7 mouse macrophages induced by Polyinosinic acid-polycytidylic acid (poly (I:C)). RAW 264.7 mouse macrophages induced by poly (I:C) were treated with or without PA, the viability of which was determined to screen working solution of PA. RNA-sequencing was applied to analyze the differentially expressed genes (DEGs). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were carried out. The expressions of interleukin (IL)-1β, heme oxygenase 1 (HMOX1), prostaglandin-endoperoxide synthase 2 (PTGS2), ATP binding cassette subfamily A member 1 (Abca1) and NF-κB-related proteins were measured by enzyme-linked immunosorbent assay (ELISA), quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot. As a result, PA at 1, 2, 3, 4 and 5 μM slightly affected cell viability, while PA at 6 and 7 μM significantly inhibited cell viability. GO and KEGG analysis results revealed that DEGs were mainly enriched in the pathways related to inflammatory signaling. Through further analysis, we obtained five possible targets of PA, and verified that PA inhibited the expressions of IL-1β, HMOX1, PTGS2 and Abca1 as well as the activation of NF-κB pathway in poly (I:C)-induced RAW264.7 cells. To summarize, PA may inhibit expressions of the inflammation-related genes in poly (I:C)-induced RAW264.7 cells, which demonstrates its potential as a drug against virus related diseases.

Lipids of Platelet-Rich Fibrin Reduce the Inflammatory Response in Mesenchymal Cells and Macrophages

Platelet-rich fibrin (PRF) has a potent anti-inflammatory activity but the components mediating this effect remain unknown. Blood lipids have anti-inflammatory properties. The question arises whether this is also true for the lipid fraction of PRF. To answer this question, lipid fractions of solid and liquid PRF were tested for their potential to lower the inflammatory response of ST2 bone marrow stromal cells and primary bone marrow macrophages exposed to IL1β and TNFα, and LPS, respectively. Cytokine production and the underlying signalling pathway were analysed by RT-PCR, immunoassays, and Western blotting. We report here that lipids from solid and liquid PRF substantially lowered cytokine-induced expression of IL6, CCL2 and CCL5 in ST2 cells. Moreover, the inflammatory response induced by Pam3CSK4, the agonist of Toll-like receptor (TLR) TLR2, was partially reduced by the lipid extracts in ST2 cells. The PRF lipids further reduced the LPS-induced expression of IL1β, IL6 and CCL5 in macrophages at the transcriptional level. This was confirmed by showing the ability of PRF lipids to diminish IL6 at the protein level in ST2 cells and macrophages. Likewise, PRF lipid extracts reduced the phosphorylation of p38 and JNK and moderately decreased the phosphorylation of NFκB-p65 in ST2 cells. These findings suggest that the lipid fraction is at least partially responsible for the anti-inflammatory activity of PRF in vitro.

GARP Regulates the Immune Capacity of a Human Autologous Platelet Concentrate

Autologous platelet concentrates, like liquid platelet rich fibrin (iPRF), optimize wound healing; however, the underlying immunological mechanisms are poorly understood. Platelets, the main cellular component of iPRF, highly express the protein, Glycoprotein A repetitions predominant (GARP), on their surfaces. GARP plays a crucial role in maintaining peripheral tolerance, but its influence on the immune capacity of iPRF remains unclear. This study analyzed the interaction of iPRF with immune cells implicated in the wound healing process (human monocyte derived macrophages and CD4⁺ T cells) and evaluated the distinct influence of GARP on these mechanisms in vitro. GARP was determined to be expressed on the surface of platelets and to exist as a soluble factor in iPRF. Platelets derived from iPRF and iPRF itself induced a regulatory phenotype in CD4⁺ T cells, shown by increased expression of Foxp3 and GARP as well as decreased production of IL-2 and IFN-γ. Application of an anti-GARP antibody reversed these effects. Additionally, iPRF polarized macrophages to a "M0/M2-like" phenotype in a GARP independent manner. Altogether, this study demonstrated for the first time that the immune capacity of iPRF is mediated in part by GARP and its ability to induce regulatory CD4⁺ T cells.

Efficacy of biologics for alveolar ridge preservation/reconstruction and implant site development: An American Academy of Periodontology best evidence systematic review

BACKGROUND

The use of biologics may be indicated for alveolar ridge preservation (ARP) and reconstruction (ARR), and implant site development (ISD). The present systematic review aimed to analyze the effect of autologous blood-derived products (ABPs), enamel matrix derivative (EMD), recombinant human platelet-derived growth factor-BB (rhPDGF-BB), and recombinant human bone morphogenetic protein-2 (rhBMP-2), on the outcomes of ARP/ARR and ISD therapy (i.e., alveolar ridge augmentation [ARA] and maxillary sinus floor augmentation [MSFA]).

METHODS

An electronic search for eligible articles published from January 2000 to October 2021 was conducted. Randomized clinical trials evaluating the efficacy of ABPs, EMD, rhBMP-2, and rhPDGF-BB for ARP/ARR and ISD were included according to pre-established eligibility criteria. Data on linear and volumetric dimensional changes, histomorphometric findings, and a variety of secondary outcomes (i.e., clinical, implant-related, digital imaging, safety, and patient-reported outcome measures [PROMs]) were extracted and critically analyzed. Risk of bias assessment of the selected investigations was also conducted.

RESULTS

A total of 39 articles were included and analyzed qualitatively. Due to the high level of heterogeneity across studies, quantitative analyses were not feasible. Most studies in the topic of ARP/ARR revealed that the use of biologics rendered similar results compared with conventional protocols. However, when juxtaposed to unassisted healing or socket filling using collagen sponges, the application of biologics did contribute to attenuate post-extraction alveolar ridge atrophy in most investigations. Additionally, histomorphometric outcomes were positively influenced by the application of biologics. The use of biologics in ARA interventions did not yield superior clinical or radiographic outcomes compared with control therapies. Nevertheless, ABPs enhanced new bone formation and reduced the likelihood of early wound dehiscence. The use of biologics in MSFA interventions did not translate into superior clinical or radiographic outcomes. It was observed, though, that the use of some biologics may promote bone formation during earlier stages of healing. Only four clinical investigations evaluated PROMs and reported a modest beneficial impact of the use of biologics on pain and swelling. No severe adverse events in association with the use of the biologics evaluated in this systematic review were noted.

CONCLUSIONS

Outcomes of therapy after post-extraction ARP/ARR and ARA in edentulous ridges were comparable among different therapeutic modalities evaluated in this systematic review. Nevertheless, the use of biologics (i.e., PRF, EMD, rhPDGF-BB, and rhBMP-2) in combination with a bone graft material generally results into superior histomorphometric outcomes and faster wound healing compared with control groups.

The application of injectable platelet-rich fibrin in regenerative dentistry: A systematic scoping review of In vitro and In vivo studies

Background

Ongoing research in the dental field has begun to focus on the use of injectable platelet-rich fibrin (I-PRF) as a regenerative tool with the potential to prompt tissue regeneration. In this regard, this systematic scoping review aimed to collect, map, and appraise the in vitro and in vivo studies regarding the role of I-PRF in or soft and hard tissue regeneration in relation to oral and maxillofacial structures.

Methods

A systematic electronic search of Medline, Scopus, Web of Science, and Embase databases was performed from 2000 to December 2021 using a combination of keywords. All in vitro and in vivo studies, written in English and concerning the potential role of I-PRF in regenerative dentistry were considered.

Results

In total, 18 in vitro studies, 5 animal studies, 6 case reports, and 31 clinical studies have evaluated the effect of I-PRF on oral and maxillofacial soft and hard tissue regeneration. The investigated studies verified the anti-inflammatory, anti-microbial efficacy and the positive effects of I-PRF application for wound, periodontal, bone, cartilage, and pulp regeneration, as well as acceleration in tooth movement during orthodontic treatment.

Conclusions

Current literature approves the feasibility of I-PRF application as a promising regenerative adjunct to dental procedures.

Platelet-Rich Fibrin Reduces IL-1β Release from Macrophages Undergoing Pyroptosis

Background: Pyroptosis is a catabolic process relevant to periodontal disorders for which interleukin-1β (IL-1β) inflammation is central to the pathophysiology of the disease. Despite platelet-rich fibrin (PRF) anti-inflammatory properties and its application to support periodontal regeneration, the capacity of PRF to modulate pyroptosis, specifically the production and release of IL-1β, remains unknown. The question arises whether PRF could regulate IL-1β release from macrophages in vitro. Methods: To answer this question, RAW 264.7 macrophages and primary macrophages obtained from murine bone marrow were primed with PRF before being challenged by lipopolysaccharide (LPS). Cells were then analysed for the pyroptosis signalling components by gene expression analyses and IL-1β secretion at the protein level. The release of mitochondrial reactive oxygen species (ROS) was also detected. Results: PRF lowered the LPS-induced expression of IL-1β and NLRP3 inflammasome, caspase-11 and IL-18 in primary macrophages, and IL-1β and caspase-11 in RAW 264.7 cells. Additionally, PRF diminished the secretion of IL-1β at the protein level in LPS-induced RAW 264.7 cells. This was shown through immunoassays performed with the supernatant and further confirmed by analysing the lysates of permeabilised cells. Furthermore, PRF reduced the ROS release provoked by LPS in RAW 264.7 cells. Finally, to enhance IL-1β release from the LPS-primed macrophages, we introduced a second signal with adenosine triphosphate (ATP). In this setting, PRF significantly reduced IL-1β release in RAW 264.7 cells and a trend to diminish IL-1β release in primary macrophages. Conclusion: These findings suggest that PRF can reduce IL-1β release and, at least in part, inhibit pyroptosis-related factors in LPS-challenged macrophages.

Blood Clots versus PRF: Activating TGF-β Signaling and Inhibiting Inflammation In Vitro

The preparation of platelet-rich fibrin (PRF) requires blood centrifugation to separate the yellow plasma from the red erythrocyte fraction. PRF membranes prepared from coagulated yellow plasma are then transferred to the defect sites to support tissue regeneration. During natural wound healing, however, it is the unfractionated blood clot (UBC) that fills the defect site. It is unclear whether centrifugation is necessary to prepare a blood-derived matrix that supports tissue regeneration. The aim of the present study was to compare lysates prepared from PRF and UBC based on bioassays and degradation of the respective membranes. We report here that lysates prepared from PRF and UBC membranes similarly activate TGF-β signaling, as indicated by the expression of interleukin 11 (IL-11), NADPH oxidase 4 (NOX-4) and proteoglycan 4 (PRG4) in gingival fibroblasts. Consistently, PRF and UBC lysates stimulated the phosphorylation and nuclear translocation of Smad3 in gingival fibroblasts. We further observed that PRF and UBC lysates have comparable anti-inflammatory activity, as shown by the reduction in lipopolysaccharide (LPS)-induced IL-6, inducible nitric oxidase synthase (iNOS) and cyclooxygenase 2 (COX-2) expression in RAW264.7 cells. Moreover, inflammation induced by Poly (1:C) HMW and FSL-1, which are agonists of Toll-like receptor (TLR) 3 and 2/6, respectively, was reduced by both PRF and UBC. PRF and UBC lysates reduced the nuclear translocation of p65 in LPS-induced RAW264.7 cells. In contrast to the similar activity observed in the bioassays, UBC membranes lack the structural integrity of PRF membranes, as indicated by the rapid and spontaneous disintegration of UBC membranes. We show here that the lysates prepared from PRF and UBC possess robust TGF-β and anti-inflammatory activity. However, visual inspection of the PRF and UBC membranes confirmed the negative impact of erythrocytes on the structural integrity of membranes prepared from whole blood. The data from the present study suggest that although both UBC and PRF have potent TGF-β and anti-inflammatory activity, UBC does not have the strength properties required to be used clinically to prepare applicable membranes. Thus, centrifugation is necessary to generate durable and clinically applicable blood-derived membranes.

Biofunctionalization of Xenogeneic Collagen Membranes with Autologous Platelet Concentrate-Influence on Rehydration Protocol and Angiogenesis

Background: The aim of this study was to analyze possible interactions of different xenogeneic collagen membranes (CM) and platelet-rich fibrin (PRF). PH values were evaluated in the CM rehydration process with PRF, and their influence on angiogenesis was analyzed in vivo. Materials and Methods: Porcine (Bio-Gide®, Geistlich)- and bovine-derived collagen membranes (Symbios®, Dentsply Sirona) were biofunctionalized with PRF by plotting process. PRF in comparison to blood, saline and a puffer pH7 solution was analysed for pH-value changes in CM rehydration process in vitro. The yolk sac membrane (YSM) model was used to investigate pro-angiogenic effects of the combination of PRF and the respective CM in comparison to native pendant by vessel in-growth and branching points after 24, 48 and 72 h evaluated light-microscopically and by immunohistochemical staining (CD105, αSMA) in vivo. Results: Significantly higher pH values were found at all points in time in PRF alone and its combined variants with Bio-Gide® and Symbios® compared with pure native saline solution and pH 7 solution, as well as saline with Symbios® and Bio-Gide® (each p < 0.01). In the YSM, vessel number and branching points showed no significant differences at 24 and 48 h between all groups (each p > 0.05). For PRF alone, a significantly increased vessel number and branching points between 24 and 48 h (each p < 0.05) and between 24 and 72 h (each p < 0.05) was shown. After 72 h, CM in combination with PRF induced a statistically significant addition to vessels and branching points in comparison with native YSM (p < 0.01) but not vs. its native pendants (p > 0.05). Summary: PRF represents a promising alternative for CM rehydration to enhance CM vascularization.

Anti-Inflammatory Activity of a Demineralized Bone Matrix: An In Vitro Pilot Study

Demineralized bone matrix (DBM) is commonly used for the reconstruction of bone defects. Early graft consolidation involves a transient inflammatory process. It is, however, unclear whether DBM can modulate this process. To test this possibility, we prepared acid lysates of demineralized ground cortical (DGC) and moldable demineralized fibers (MDF). Murine RAW 264.7 and primary bone marrow macrophages were exposed to acid lysates of DGC and MFD prior to provoking an inflammatory response with lipopolysaccharide (LPS). Similarly, murine ST2 mesenchymal cells were exposed to DGC and MFD with and without interleukin 1β (IL1) and TNFα. We show here that acid lysates of DGC and MFD reduced the expression of IL1 and IL6 in RAW 264.7 macrophages, as determined by RT-PCR and, for IL6, by immunoassay. This response was confirmed with primary macrophages. Likewise, desalted acid lysates exert anti-inflammatory properties on RAW 264.7 cells and in ST2 cells, the forced expression of IL6, inducible nitric oxide synthase (iNOS) and chemokine ligand 5 (CCL5) was reduced. These in vitro findings suggest that DGC and MFD lower the inflammation-induced expression of inflammatory mediators in murine cell-based bioassays.

Platelet-Rich Fibrin Decreases the Inflammatory Response of Mesenchymal Cells

Chronic inflammation is a pathological process where cells of the mesenchymal lineage become a major source of inflammatory mediators. Platelet-rich fibrin (PRF) has been shown to possess potent anti-inflammatory activity in macrophages, but its impact on mesenchymal cells has not been investigated. The aim of this study was, therefore, to expose mesenchymal cells to inflammatory cytokines together with lysates generated from liquid platelet-poor plasma (PPP), the cell-rich buffy coat layer (BC; concentrated-PRF or C-PRF), and the remaining red clot layer (RC), following centrifugation of blood. Heating PPP generates an albumin gel (Alb-gel) that when mixed back with C-PRF produces Alb-PRF. Membranes prepared from solid PRF were also subjected to lysis. We report here that lysates of PPP, BC, and PRF decreased the cytokine-induced expression of interleukin 6 (IL6) and nitric oxide synthase (iNOS) in the bone marrow-derived ST2 cells. Consistently, PPP, BC, and PRF greatly decreased the phosphorylation and nuclear translocation of p65 in ST2 cells. The inflammatory response caused by Pam3CSK4 was reduced accordingly. Moreover, PPP, BC, and PRF reduced the enhanced expression of inflammatory mediators IL6 and iNOS in 3T3-L1 pre-adipocyte mesenchymal cells, and iNOS and CCL5 in murine calvarial cells. Surprisingly, PRF lysates were not effective in reducing the inflammatory response of human gingival fibroblasts and HSC2 epithelial cells. The data from the present study suggest that both liquid PRF and solid PRF exert potent anti-inflammatory activity in murine mesenchymal cells.

Second generation liquid platelet concentrates: A literature review

Liquid or injectable platelet rich fibrin (PRF) is a second-generation platelet concentrate which is completely autologous and free of external additives like bovine thrombin and calcium chloride. Additionally, it is the only one to be obtained in a liquid form among the second generation platelet concentrates. This allows for wide applications such as to maximize injections or mixing with biomaterials such as bone grafts or antibiotics. Since it was first introduced in 2015, several modifications of the original protocol have been proposed which aim at maximizing its biological and mechanical properties. This includes changes in centrifugation speed, time, and so on. The aim of this review is to summarize the various modifications of the injectable/liquid formation of PRF as well as to discuss the potential applications and future research direction.