Background/Objectives: The body’s reaction after the implantation of a biomaterial is a non-specific inflammatory response that is mainly initiated via the recruitment of polymorphonuclear cells (PMNs) to the implant site secreting cytokines and growth factors, followed by activation of monocytes/macrophages, finally leading to wound healing. The wound healing process is dependent on the priming of the PMNs that can be guided towards an inflammatory or a regenerative phenotype with the associated characteristic PMN cytokine profiles. Since the collagen-based Purified Reconstituted Bilayer Matrix (PRBM) triggers the wound healing process at the implant site in vivo, it is hypothesized that this positive effect might be due to a material-mediated priming of the PMNs towards the regenerative phenotype. With the use of the blood concentrate platelet-rich fibrin (PRF) containing high concentrations of leukocytes, including PMNs, the natural environment of the body after the implantation of a material can be mimicked in vitro. The aim of the present study was to characterize the phenotype of native blood-derived PMNs within PRF in response to the PRBM. Methods: PMNs within PRF gained from different relative centrifugal forces were characterized in a first step before PRF was combined with the PRBM for 4 h. Supernatants were harvested to analyze the phenotype of the PMNs via the evaluation of eight different cytokines using the ELISA. Results: Analysis of the PMN phenotype could assess cytokines commonly associated with neutrophils of the proinflammatory phenotype, such as TNFα, IL15, and IL1, as lower in supernatants when PRF was incubated in the presence of the PRBM and compared to the control PRF. On the other hand, cytokines related to the PMN regenerative phenotype, like TGFβ and IL10, could be detected as higher when PRF was incubated in the presence of the PRBM. Conclusions: This might suggest that PRBM significantly activates and primes neutrophils to the regenerative phenotype, leading to the resolution of inflammation. This might trigger the process of wound healing and tissue regeneration, making the PRBM a beneficial material for therapeutic applications.

Childhood trauma defects in the head and neck area are challenging in many aspects for patients and surgeons. One major issue is the still incomplete growth. Bone defect fixation measures have to consider biomechanical forces due to the bone growth from both sides, the bone growth possibly influencing and working against the fixation itself and vice versa. A solution will be the development of a stable but, at the same time, quickly degradable osteosynthesis system (OSS) specifically for the pediatric sector. Besides the physical demands, biocompatibility and low risk for unphysiological tissue response are exceptionally important. A newly developed PDLLA-derivate/chitosan hybrid material (PDLLA:CC:Mg+Chitosan) with promising features confirmed in vitro experimental set-ups has been tested in a critical size bone defect model in Wistar rats to confirm slow degradation and absence of unphysiological integration of the material, and of bone growth induced by the material itself. mCT and histologic analysis of implanted rat skulls after 1, 3, and 5 months confirmed slow degradation of the PDLLA:CC:Mg+Chitosan material without any unintended bone growth induction or morphologic changes due to the material. The results of this in vivo study confirmed the suitability of the material to serve as OSS in clinical practice.

Abstract Purpose Cumulating evidence supports the close association between periodontal diseases, neuroinflammation and neurodegenerative pathologies, except for peri-implantitis (PI). Thus, this study explored the association between experimental PI and neuropathological changes in the rat brain. Materials and methods After bilateral first molars extraction, experimental PI was induced at titanium implants placed in the maxillae by lipopolysaccharide injections and ligature placement. Following 28-weeks of disease progression, the maxillae and brains were retrieved from 6 rats. Healthy brains from 3 rats were used as control. Brains were analyzed by immunohistochemistry to detect signs of neuroinflammation (interleukin (IL)-6 and tumor necrosis factor (TNF)-α)), microglial activation (IBA-1) and astrogliosis (GFAP). To explore signs of neurodegeneration, hematoxylin/eosin and Nissl stainings were used. Also, four different antibodies against amyloid beta (Aβ 1–42) were tested. Results Chronic PI lesions showed peri-implant bone resorption accompanied by large inflammatory infiltrates. IL-6+ and TNF-α+ cells were found within the CA1 and Dentate Gyrus regions of the hippocampus of the PI-affected group, while almost no immune-positivity was detected in the control (p < 0.05). Detection of activated GFAP+ microglia and IBA-1+ astrocytes surface were significantly higher at the CA areas, and cerebral cortex of the PI-affected group, in comparison with control (p < 0.05). Shrunk neurons with pyknotic nuclei were inconsistently found among the PI-affected group, and these were almost not detected in control. No positive Aβ reactivity was detected in any of the samples. Conclusion Chronic experimental PI lesions led to an increased detection of IL-6 and TNF-α, GFAP+ microgliosis and IBA-1+ astrocytosis, and in some cases, neurodegeneration, in the rat brain.

AIM:To evaluate the T regulatory lymphocyte (Treg) profile and its potential contribution to peri-implant tissue destruction during peri-implantitis (PI). METHODS:PI granulation tissue and crevicular fluid collected during PI surgical (PI group, n = 23) and explantation (PI-X group, n = 23) therapy, with peri-implant healthy tissue from second-stage surgery (H group, n = 20) as controls, were analysed. The inflammatory infiltrate was characterised by H&E staining. The relative expression of Treg-associated transcription factors and cytokines was assessed by RT-qPCR. Forkhead box P3 (FOXP3) and neuropilin (NPR)-1 were detected by immunohistochemistry, and interleukin (IL)-10, TGF-β1 and IL-35 by ELISA. The clinical parameters, namely probing depth (PD), bleeding on probing (BOP) and vertical defect depth (VDD), were also recorded. RESULTS:PI and PI-X lesions showed up-regulation of FOXP3, HELIOS and IL35B and down-regulation of NRP1 and TGFβ1 mRNA expression, compared to H tissue (p < 0.05). Significantly more FOXP3+ cells and significantly less NRP-1+ area were detected in PI and PI-X lesions (p < 0.05). IL-35 levels were up-regulated, whereas TGF-β1 levels were down-regulated in PI and PI-X lesions, compared to H samples (p < 0.05). PD and VDD were significantly correlated with the down-regulation of FOXP3 and NRP-1 (p < 0.05). CONCLUSIONS:Treg dysfunction and altered cytokine profiles in PI are associated with inflammation and clinical disease severity.

Background/Objectives: Immune cells are integral to bone homeostasis, including the repair and remodeling of bone tissue. Chronic dysregulation within this osteoimmune network can lead to bone marrow defects of the jaw (BMDJ), particularly fatty degenerative osteonecrosis of the jaw (FDOJ). These localized pathologies are implicated in systemic immune dysfunctions. Methods: This study is designed to determine whether BMDJ/FDOJ samples are indicative of medullary bone pathology by evaluating FDOJ gene expression patterns using quantitative real-time PCR. Results: Comparative analyses between pathological and healthy samples evaluated the dysregulation of key molecular pathways. BMDJ/FDOJ samples showed significant upregulation of inflammatory mediators, including CCL5/RANTES, VEGF, IGF and KOR, and downregulation of structural proteins, such as collagen types I, II and IV, and osteogenesis-associated factors, such as SP7. Conclusions: The study provides new insights into the molecular mechanisms of BMDJ/FDOJ by identifying potential molecular changes suggesting a pro-inflammatory state in the affected jawbone which may contribute to systemic immune dysregulation. The findings are consistent with morphologic observations of BMDJ/FDOJ in degenerated jawbone and underscore the need for integrative approaches in dentistry and medicine while highlighting BMDJ/FDOJ as a potential target for therapeutic and preventive strategies against systemic diseases and emphasizing its clinical significance.

Periodontitis is a prevalent condition that leads to the destruction of periodontal tissue, making the regeneration of the periodontium a key focus in dental research. In this context, periodontal ligament cells (PDLCs) are particularly interesting due to their stem cell-like properties, including the ability to differentiate into various cell types and further contribute to tissue repair. This study aimed to isolate and characterize primary human PDLCs and examine the effects of both indirect and direct treatment with the blood concentrate platelet-rich fibrin (PRF), with particular focus on how PRF influences cell proliferation and differentiation. PDLCs were treated with PRF prepared using a low relative centrifugal force (600 rpm) either directly through a conditioned medium or indirectly using trans-well filter systems. The impact of PRF on PDLC proliferation and differentiation was assessed through viability assays, alkaline phosphatase assays, gene and protein expression analyses, and immunofluorescence. PDLCs exhibited cellular markers characteristic of stem cell-like cells. In addition, PRF treatment was found to suppress cell proliferation while concurrently promoting osteogenic differentiation and increase factors important for tissue regeneration. These effects were more pronounced when the cells were directly treated with PRF-conditioned medium compared to indirect treatment. Our findings support the hypothesis that PRF serves as a biologically active reservoir of growth factors that modulate PDLC behavior and might create a microenvironment favorable for periodontal repair.

Platelet-rich fibrin (PRF) has assumed an important role in supporting tissue regeneration in different fields. To date, the standard protocol for liquid PRF requires at least 10 mL of peripheral blood. The present study aimed to analyze the composition, growth factor release, and effects on the cell proliferation of PRF samples produced using 3 mL vs. 10 mL of peripheral blood in vitro. Peripheral venous blood from six healthy donors was used to prepare liquid PRF using either 3 mL or 10 mL tubes. Three different centrifugation protocols were used according to the low-speed centrifugation concept. The cellular distribution was evaluated using immunohistology and automated cell count. ELISA was used to determine the release of different growth factors (EGF, TGF-β1, and PDGF) and interleukin 8 at different time points. Primary human osteoblasts (pOBs) were cultivated for 7 days using PRF-conditioned media acquired from either 3 mL or 10 mL of peripheral blood. The results showed that 3 mL of peripheral blood is sufficient to produce a liquid PRF concentrate similar to that acquired when using 10 mL blood. The concentrations of platelets and leukocytes were comparable regardless of the initial blood volume (3 mL vs. 10 mL). Similarly, the release of growth factors (EGF, TGF-β1, and PDGF) and interleukin 8 was often comparable in both groups over 7 days. The cultivation of pOBs using PRF-conditioned media showed a similar proliferation rate regardless of the initial blood volume. This proliferation rate was also similar to that of pOBs treated with 20% FBS-conditioned media. These findings validated the use of 3 mL of peripheral blood to generate liquid PRF matrices according to the low-speed centrifugation concept, which may open new application fields for research purposes such as in vivo experiments and clinical applications such as pediatric surgery.

Platelet-rich fibrin (PRF), derived from human blood, rich in wound healing components, has drawbacks in direct injections, such as rapid matrix degradation and growth factor release. Marine polysaccharides, mimicking the human extracellular matrix, show promising potential in tissue engineering. In this study, we impregnated the self-assembled fucoidan/chitosan (FU_CS) hydrogels with PRF obtaining PRF/FU_CS hydrogels. Our objective was to analyze the properties of a hydrogel and the sustained release of growth factors from the hydrogel that incorporates PRF. The results of SEM and BET-BJH demonstrated the relatively porous nature of the FU_CS hydrogels. ELISA data showed that combining FU_CS hydrogel with PRF led to a gradual 7-day sustained release of growth factors (VEGF, EGF, IL-8, PDGF-BB, TGF-β1), compared to pure PRF. Histology confirmed ELISA data, demonstrating uniform PRF fibrin network distribution within the FU_CS hydrogel matrix. Furthermore, the FU_CS hydrogels revealed excellent cell viability. The results revealed that the PRF/FU_CS hydrogel has the potential to promote wound healing and tissue regeneration. This would be the first step in the search for improved growth factor release.

Nonmelanoma skin cancer (NMSC) presents a significant challenge to global healthcare due to its rising incidence, prompting the search for innovative treatments to overcome the limitations of current therapies. Our study aims to explore the potential effects of the liquid blood concentrate platelet-rich fibrin (PRF) on basal cell carcinoma cells (BCCs) and squamous cell carcinoma cells (SCCs) in order to obtain results that may lead to new possible adjunctive therapies for managing localized skin cancers, particularly NMSC. Basal cell carcinoma (BCC) cells and squamous cell carcinoma (SCC) cells were indirectly treated with PRF generated via different relative centrifugation forces, namely high and low RCF PRF, for 7 days. PRF-treated cells were comparatively analyzed for cell viability, proliferation and cell cycle- and apoptosis-related gene expression. Analysis of MTS assay results revealed a significant decrease in cell viability in both BCC and SCC cells following PRF treatment for 7 days. Ki-67 staining showed a decreased percentage of Ki-67-positive cells in both BCC and SCC cells after 2 days of treatment compared to the control group. The downregulation of CCND1 gene expression in both cell types at 2 days along with the upregulation of p21 and p53 gene expression in SCC cells demonstrated the effect of PRF in inhibiting cell proliferation and inducing cell cycle arrest, especially during the initial phases of treatment. Increased expression of caspase-8 and caspase-9 was observed, indicating the activation of both extrinsic and intrinsic apoptotic pathways by PRF treatment. Although the exact immunomodulatory properties of PRF require further investigation, the results of our basic in vitro studies are promising and might provide a basis for future investigations of PRF as an adjunctive therapy for managing localized skin cancers, particularly NMSC.

Blood concentrates like platelet rich fibrin (PRF) have been established as a potential autologous source of cells and growth factors with regenerative properties in the field of dentistry and regenerative medicine. To further analyze the effect of PRF on bone tissue regeneration, this study investigated the influence of liquid PRF matrices on human healthy primary osteoblasts (pOB) and co-cultures composed of pOB and human dermal vascular endothelial cells (HDMEC) as in vitro model for bone tissue regeneration. Special attention was paid to the PRF mediated influence on osteoblastic differentiation and angiogenesis. Based on the low-speed centrifugation concept, cells were treated indirectly with PRF prepared with a low (44 g) and high relative centrifugal force (710 g) before the PRF mediated effect on osteoblast proliferation and differentiation was assessed via gene and protein expression analyses and immunofluorescence. The results revealed a PRF-mediated positive effect on osteogenic proliferation and differentiation accompanied by increased concentration of osteogenic growth factors and upregulated expression of osteogenic differentiation factors. Furthermore, it could be shown that PRF treatment resulted in an increased formation of angiogenic structures in a bone tissue mimic co-culture of endothelial cells and osteoblasts induced by the PRF mediated increased release of proangiogenic growth factors. The effects on osteogenic proliferation, differentiation and vascularization were more evident when low RCF PRF was applied to the cells. In conclusion, PRF possess proosteogenic, potentially osteoconductive as well as proangiogenic properties, making it a beneficial tool for bone tissue regeneration. What is the context?The treatment of bone defects is still a challenge in the field of regenerative medicine. In this context, researchers and clinicians are continuously focusing on developing new therapeutic strategies like the use of autologous blood concentrates like Platelet rich fibrin (PRF) to improve regeneration by directly delivering wound healing promoting cells and growth factors to the defect side in order to restore the structure and functional integrity of damaged hard tissue in combination with adequate tissue regeneration.What is new?Focus of the present in vitro study was to further evaluate the potential of PRF paying particular attention to the PRF-mediated effect on osteogenic differentiation and angiogenesis of human primary osteoblasts as well as on a more complex tissue like co-culture consisting of osteoblasts and microvascular endothelial cells. We could demonstrate that PRF is able to support and affect a variety of processes involved in bone tissue regeneration including osteogenic proliferation, osteogenic differentiation as well as angiogenic structure formation.Treatment of PRF resulted in:- increased cell viability*- higher expression of osteogenic differentiation factors*- higher release of osteogenic growth factors*- increased formation of microvessel-like structures*(*compared to untreated control)What is the impact?PRF represents a beneficial autologous tool for regenerative purposes combining proosteogenic and proangiogenic properties. Therefore, PRF might be used for applications in versatile fields of medicine in the context of improving bone tissue regeneration.

Platelet-rich fibrin (PRF) is a widely used autologous blood concentrate in regenerative medicine. This study aimed to characterize the cellular composition and distribution of different PRF matrices generated by high (710 g) and low (44 g) relative centrifugal forces (RCFs) and to analyze their bioactivity on human primary osteoblasts (pOBs). PRF was separated into upper layer (UL) and buffy coat (BC) fractions, and their cellular contents were assessed using histological and immunohistochemical staining. The release of platelet-derived growth factor (PDGF) and transforming growth factor (TGF-β) was quantified using an ELISA. Indirect PRF treatment on pOBs was performed to evaluate cell viability and morphology. A histological analysis revealed higher quantities of leukocytes and platelets in the low-RCF PRF. TGF-β release was significantly higher in the low-RCF PRF compared to the high-RCF PRF. All PRF fractions promoted pOB proliferation regardless of the centrifugation protocol used. The low-RCF PRF showed higher TGF-β levels than the high-RCF PRF. These findings contribute to understanding the cellular mechanisms of PRF and provide insights into optimizing PRF protocols for bone regeneration, advancing regenerative medicine, and improving patient outcomes.

The understanding that tumor cells might evade immunity through various mutations and the potential of an augmented immune system to eliminate abnormal cells led to the idea of utilizing platelet-rich fibrin (PRF), a blood concentrate containing the body’s immune elements as an adjunctive therapy for localized tumors. This study is the first that evaluated the effect of PRF generated with different relative centrifugal forces (RCFs) on osteoblastic and fibroblastic tumor cell lines MG63 and HT1080 with regard to cell viability, cytokine and growth factor release, and the gene expression of factors related to the cell cycle and apoptosis. Our findings could demonstrate decreased cell proliferation of MG63 and HT1080 when treated indirectly with PRF compared to cell cultures without PRF. This effect was more distinct when the cells were treated with low-RCF PRF, where higher concentrations of growth factors and cytokines with reduced RCFs can be found. Similar patterns were observed when assessing the regulation of gene expression related to the cell cycle and apoptosis in both MG63 and HT1080 cells treated with PRF. Despite variations, there was a consistent trend of an up-regulation of tumor-suppressive genes and a down-regulation of anti-apoptotic genes in both cell types following treatment with high- and, particularly, low-RCF PRF formulations.

Human dental pulp stem cells (DPSCs) exhibit multilineage differentiation capabilities and superior clonogenic and proliferative properties. However, the use of animal-derived components such as FBS raises concerns regarding the clinical application of stem-cell-based therapies. Platelet-rich fibrin (PRF) derived from human blood is rich in fibrin, platelets, and growth factors and acts as a bioactive scaffold for grafting with biomaterials. In this study, we assessed the efficacy of PRF-conditioned medium (CM) in promoting DPSCs proliferation and osteogenic differentiation compared with the standard culture medium supplemented with FBS. A comparison of DPSCs cultured in FBS and PRF-CM revealed no differences in characteristics or morphology. However, cells cultured with PRF-CM exhibited inferior proliferation rates and cell numbers during passage in comparison with those cultured with FBS. In contrast, DPSCs cultured in PRF-CM showed significantly higher levels of calcification, and RT-PCR confirmed that the gene expression levels of markers associated with osteoblast differentiation were significantly increased. The PRF-CM approach offers a convenient, straightforward, and advantageous method for culturing DPSCs, without relying on animal-derived components. In summary, this study introduces a novel application of PRF-CM for enhancing the osteogenesis of DPSCs, which provides an alternative to FBS culture medium and addresses concerns associated with the use of animal-derived components in clinical settings.

During the present study, an in vitro coculture bone tissue mimic based on primary osteoblasts and primary endothelial cells was used for a complex and broad evaluation of a newly developed material for applications in pediatric maxillofacial traumatology. The biomaterial was composed of PDLLA (poly(D,L-lactide)) in various combinations with calcium carbonate (CC), magnesium (Mg), and chitosan (CH). Besides classical biocompatibility analyses, the present study evaluated material-dependent effects on fundamental processes that are essential for successful material integration and regeneration. Therefore, inflammation-associated factors such as E-selectin and interleukins were analyzed in the in vitro model system on gene expression and protein level depending on the different materials. Furthermore, in order to test the capability of vascularization of the material, the effect of the different materials on the formation of microvessel-like structures as well as the expression and release of proangiogenic factors was investigated in vitro in the bone coculture model. In addition, the mineralization capacity as well as the relative gene expression of osteogenic differentiation factors was analyzed in response to the different materials. As a result, the authors could assess the material combination PDLLA: CC CH as the most functionally tested material with regard to biocompatibility, inflammatory response, and microvessel-like structure formation as well as osteogenic differentiation in the in vitro coculture system. In conclusion, by using tissue-engineered human bone tissue equivalents as proposed here in an in vitro coculture model, biomaterial-mediated effects can be readily investigated. Moreover, it is proposed that these complex in vitro evaluations could contribute to the understanding and improvement of the development of novel materials for pediatric traumatological care for prospective clinical applications.

Objectives: This study evaluated the cellular response of primary osteoblasts exposed to two different presentations of a low-temperature non-sintered deproteinized bovine bone matrix (DBBM). Materials and methods: Six different baths of a commercially available DBBM block (Bonefill® Porous Block) and one of DBBM granule (Bonefill® Porous) were evaluated to identify the mineral structure and organic or cellular remnants. Samples of the same baths were processed in TRIZOL for RNA extraction and quantification. For the immunologic cell reaction assay, primary human osteoblasts (pOB) were exposed to DBMM block (pOB + B) or granules (pOB + G), or none (control) for 1, 3, or 7 days of cell cultivation. Expression of proinflammatory cytokines by pOB was evaluated by crosslinked ELISA assay. In addition, total DNA amount, as well as cell viability via LDH evaluation, was assessed. Results: Organic remnants were present in DBBM blocks; 45.55% (±7.12) of osteocytes lacunae presented cellular remnants in blocks compared to 17.31% (±1.31) in granules. In three of five batches of blocks, it was possible to isolate bovine RNA. The highest concentration of TGF-β1 was found in supernatants of pOB + G on day 7 (218.85 ± 234.62 pg/mL) (p < 0.05), whereas pOB + B presented the lowest amount of TGF-β1 secretion at the end of evaluation (30.22 ± 14.94 pg/mL, p < 0.05). For IL-6 and OPG, there was no statistical difference between groups, while pOB + G induced more IL-8 secretion than the control (3.03 ± 3.38 ng/mL, p < 0.05). Considering the kinetics of cytokine release during the study period, all groups presented a similar pattern of cytokines, estimated as an increasing concentration for IL-6, IL-8, and OPG during cultivation. Adherent cells were observed on both material surfaces on day 7, according to H&E and OPN staining. Conclusion: Neither tested material induced a pronounced inflammatory response upon osteoblast cultivation. However, further studies are needed to elucidate the potential influence of organic remnants in bone substitute materials on the regeneration process.

Impact statementPlatelet-rich fibrin (PRF) is prepared from autologous peripheral blood and is widely applied in research and clinical treatments. The centrifugation parameters used during the preparation of PRF directly influence its components and bioactivity. By using a standardized protocol, the present study demonstrated that adapting various centrifuges to a standardized relative centrifugal force and centrifugation protocol resulted in reproducible PRF matrices with similar bioactivity, regardless of the centrifuge rotor angle. These findings underline the necessity to carefully adapt and correctly report the used centrifuge and centrifugation protocols in scientific research to allow reproducible results. Platelet-rich fibrin (PRF) is an autologous blood concentrate that supports tissue regeneration. The effect of the centrifuge rotor angle in the fabrication of PRF is still not fully elucidated. The hypothesis of this study is: When applying the same g-force (relative centrifugal force [RCF]) and centrifugation time, PRF components and bioactivity are not modified using either a swing-out rotor or a fixed angle rotor. For this purpose, peripheral blood samples (from five donors) were used to gain solid (710 xg, 8 min) and liquid (44 xg, 8 min) PRF matrices using three different centrifuges (one fixed angle as a control and two different swing-out rotor centrifuges). The physical characteristics of the solid PRF were measured to evaluate the clot formation and cellular distribution. The liquid PRF was used to evaluate the cell number, bioactivity, and influence on primary human osteoblasts (pOBs) and primary human fibroblasts (pHFs) in vitro. Solid PRF clots were significantly larger in the group of fixed rotor centrifuges compared with either of the two evaluated swing-out rotor centrifuges. No differences were observed when evaluating the cellular distribution within the solid PRF. No statistically significant differences were documented in the cell's density in liquid PRF samples (platelets, lymphocytes, neutrophils, eosinophils, and basophils) among the differently gained PRF samples. No statistically significant differences were documented for the released growth factors (vascular endothelial growth factor, epidermal growth factor, and transforming growth factor beta 1) over 7 days. pOBs and pHFs viability after treatment with PRF conditioned media showed no statistically significant differences between the evaluated groups. However, the number of adherent cells treated with PRF obtained with the use of the fixed angle rotor was significantly higher when compared with those treated with PRF obtained by using the swing-out rotors. The presented results confirm that regardless of the centrifuge rotor used, the components and bioactivity of solid and liquid PRF matrices are modified by the applied RCF and centrifugation time. These findings are of great importance for highlighting the essential role of adapting the centrifugation protocols when using different centrifuges and to correctly report the used centrifugation protocols in scientific research to allow for reproducible results.

The combination of histological and biomolecular analyses provides deep understanding of different biological processes and is of high interest for basic and applied research. However, the available analytical methods are still limited, especially when considering bone samples. This study compared different fixation media to identify a sufficient analytical method for the combination of histological, immuno-histological and biomolecular analyses of the same fixed, processed and paraffin embedded bone sample. Bone core biopsies of rats' femurs were fixed in different media (RNAlater + formaldehyde (R + FFPE), methacarn (MFPE) or formaldehyde (FFPE)) for 1 week prior to decalcification by EDTA and further histological processing and paraffin embedding. Snap freezing (unfixed frozen tissue, UFT) and incubation in RNAlater were used as additional controls. After gaining the paraffin sections for histological and immunohistological analysis, the samples were deparaffined and RNA was isolated by a modified TRIZOL protocol. Subsequently, gene expression was evaluated using RT-qPCR. Comparable histo-morphological and immuno-histological results were evident in all paraffin embedded samples of MFPE, FFPE and R + FFPE. The isolated RNA in the group of MFPE showed a high concentration and high purity, which was comparable to the UFT and RNAlater groups. However, in the groups of FFPE and R + FFPE, the RNA quality and quantity were statistically significantly lower when compared to MFPE, UFT and RNAlater. RT-qPCR results showed a comparable outcome in the group of MFPE and UFT, whereas the groups of FFPE and R + FFPE did not result in a correctly amplified gene product. Sample fixation by means of methacarn is of high interest for clinical samples to allow a combination of histological, immunohistological and biomolecular analysis. The implementation of such evaluation method in clinical research may allow a deeper understanding of the processes of bone formation and regeneration.

Adsorbate biohybrids for BMP-2 delivery based on electrospun PDLLA-nanofiber fleeces loaded with 0.6 μg/cm2 rhBMP-2COL (E. coli) strongly induced microvessel- like structures when incubated for 14 days in cocultures of human outgrowth endothelial cells (OEC) together with human primary osteoblasts (pOB). Higher loaded rhBMP-2COL biohybrids (4.6 μg/cm2) were low- to noninductive. Adsorbate biohybrids of rhBMP-2CHO (CHO cells) loaded with 1.0-6.0 μg/cm2 induced only a classic cobblestone- like growth pattern without any microvessels. Concentration- response experiments (7 days) indicate a binding affinity of rhBMP-2COL for microvessel induction in the picomolar range with nanomolar concentrations being non-inductive

Introduction: Resorbable synthetic scaffolds are promising for different indications, especially in the context of bone regeneration. However, they require additional biological components to enhance their osteogenic potential. In addition to different cell types, autologous blood-derived matrices offer many advantages to enhance the regenerative capacity of biomaterials. The present study aimed to analyze whether biologization of a PCL-mesh coated using differently centrifuged Platelet rich fibrin (PRF) matrices will have a positive influence on primary human osteoblasts activity in vitro. A polymeric resorbable scaffold (Osteomesh, OsteoporeTM (OP), Singapore) was combined with differently centrifuged PRF matrices to evaluate the additional influence of this biologization concept on bone regeneration in vitro. Peripheral blood of three healthy donors was used to gain PRF matrices centrifuged either at High (710× g, 8 min) or Low (44× g, 8 min) relative centrifugal force (RCF) according to the low speed centrifugation concept (LSCC). OP-PRF constructs were cultured with pOBs. POBs cultured on the uncoated OP served as a control. After three and seven days of cultivation, cell culture supernatants were collected to analyze the pOBs activity by determining the concentrations of VEGF, TGF-β1, PDGF, OPG, IL-8, and ALP- activity. Immunofluorescence staining was used to evaluate the Osteopontin expression of pOBs. After three days, the group of OP+PRFLow+pOBs showed significantly higher expression of IL-8, TGF-ß1, PDGF, and VEGF compared to the group of OP+PRFHigh+pOBs and OP+pOBs. Similar results were observed on day 7. Moreover, OP+PRFLow+pOBs exhibited significantly higher activity of ALP compared to OP+PRFHigh+pOBs and OP+pOBs. Immunofluorescence staining showed a higher number of pOBs adherent to OP+PRFLow+pOBs compared to the groups OP+PRFHigh+pOBs and OP+pOBs. To the best of our knowledge, this study is the first to investigate the osteoblasts activity when cultured on a PRF-coated PCL-mesh in vitro. The presented results suggest that PRFLow centrifuged according to LSCC exhibits autologous blood cells and growth factors, seem to have a significant effect on osteogenesis. Thereby, the combination of OP with PRFLow showed promising results to support bone regeneration. Further in vivo studies are required to verify the results and carry out potential results for clinical translation.