Fibrin Matrices Research Articles

Fibronectin Binding Modulates CXCL11 Activity and Facilitates Wound Healing

Engineered biomatrices offer the potential to recapitulate the regenerative microenvironment, with important implications in tissue repair. In this context, investigation of the molecular interactions occurring between growth factors, cytokines and extracellular matrix (ECM) has gained increasing interest. Here, we sought to investigate the possible interactions between the ECM proteins fibronectin (FN) and fibrinogen (Fg) with the CXCR3 ligands CXCL9, CXCL10 and CXCL11, which are expressed during wound healing. New binding interactions were observed and characterized. Heparin-binding domains within Fg (residues 15-66 of the β chain, Fg β15-66) and FN (FNI1-5, but not FNIII12-14) were involved in binding to CXCL10 and CXCL11 but not CXCL9. To investigate a possible influence of FN and Fg interactions with CXCL11 in mediating its role during re-epithelialization, we investigated human keratinocyte migration in vitro and wound healing in vivo in diabetic db/db mice. A synergistic effect on CXCL11-induced keratinocyte migration was observed when cells were treated with CXCL11 in combination with FN in a transmigration assay. Moreover, wound healing was enhanced in full thickness excisional wounds treated with fibrin matrices functionalized with FN and containing CXCL11. These findings highlight the importance of the interactions occurring between cytokines and ECM and point to design concepts to develop functional matrices for regenerative medicine.

The role of fibrin matrices and tissue factor in early-term trophoblast proliferation and spreading

Fibrin deposition in placenta is a common phenomenon which can be triggered by villous injury and coagulation activation. Fibrin abnormalities (hypo/dysfibrinogenemia) and factor XIII deficiency are associated with infertility and pregnancy loss. While trophoblasts are known to grow on fibrin matrices, the role of this protein in trophoblast repair processes remains unclear. We hypothesize that fibrin may have an essential role in trophoblast remodeling. Morphology and spreading of primary early-term human trophoblasts and villi explants were investigated on various fibrin components. Cross-linking of matrices was evaluated by D-dimer assay. TF procoaguant activity, protein and mRNA levels in cells and villi were determined by chromogenic assay, ELISA, immunohistochemistry and reverse-transcription PCR (RT-PCR). Fibrin but not fibrinogen, thrombin or fibronectin caused increased trophoblast proliferation and spreading. Trophoblasts cultured on factor XIII (FXIII) depleted fibrin caused their increased proliferation and spreading, associated with cross-linking. FXIII addition further increased this effect, while cell culturing on active FXIII without fibrin retained cellular proliferation. Decreased TF activity, antigen and RNA expression were demonstrated in fibrin-cultured trophoblasts and villi explants, compared to matrigel explants. Results obtained demonstrate distinct mechanisms underlying fibrin cross-linking, which can affect trophoblast proliferation. The excess of fibrin deposits may be limited by the decrease in TF levels, thus enabling adequate placental perfusion. These findings demonstrate fibrin importance for placental repair and may partly explain poor pregnancy outcome associated with certain fibrinogen/fibrin abnormalities and FXIII deficiency.

Rapid onset of perfused blood vessels after implantation of ECFCs and MPCs in collagen, PuraMatrix and fibrin provisional matrices

We developed an in vivo vascularization model in which human endothelial colony-forming cells (ECFCs) and human mesenchymal progenitor cells (MPCs) form blood vessel networks when co-injected (ECFC + MPC) into nude mice in rat tail type I collagen, bovine fibrin or synthetic peptide PuraMatrix matrices. We used three approaches to determine the onset of functional vascularization when ECFC + MPC suspended in these matrices were implanted in vivo. The first was immunohistochemistry to detect vessels lined by human endothelial cells and filled with red blood cells. The second was in vivo vascular staining by tail vein injection of a mixture of Ulex europaeus agglutinin I (UEA-I), a lectin specific for human endothelium, and Griffonia simplicifolia isolectin B4 (GS-IB4 ), a lectin specific for rodent endothelium. The third approach employed contrast-enhanced ultrasound to measure the perfusion volumes of implants in individual animals over time. Human endothelial-lined tubular structures were detected in vivo on days 1 and 2 after implantation, with perfused human vessels detected on days 3 and 4. Contrast-enhanced ultrasound revealed significant perfusion of ECFC + MPC/collagen implants on days 1-4, at up to 14% perfused vascular volume. ECFC + MPC implanted in fibrin and PuraMatrix matrices also supported perfusion at day 1, as assessed by ultrasound (at 12% and 23% perfused vascular volume, respectively). This model demonstrates that ECFC + MPC suspended in any of the three matrices initiated a rapid onset of vascularization. We propose that ECFC + MPC delivered in vivo provide a means to achieve rapid perfusion of tissue-engineered organs or for in situ tissue repair.

Sandwiched polymer fibre in fibrin matrices for the dictation of endothelial cells undergoing angiogenesis

We present here a three-dimensional (3D) sandwich system made by poly(ethylene terephthalate) (PET) fibre and fibrin extracellular matrix (ECM) for endothelial cell dictation and angiogenesis guidance. In this three-dimensional system, Human Umbilical Vein Endothelial cells (HUVECs) were firstly cultured for 2 (two) days to cover the PET fibre before sandwiched in two layer fibrin gel containing HUVECs. After 4 (four) days of culture, cel-to-cel connection, tube-like structure and multi-cellular lumen formation were then assessed and validated. Phase contrast and fluorescence imaging using an inverted microscope were used to determine cell-to-cell and cell-ECM interactions. Laser scanning confocal microscopy and histological techniques were used to confirm the development of tube-like structure and multi-cellular lumen formation. This study shows that polymer fibres sandwiched in fibrin gel can be used to dictate endothelial cells undergoing angiogenesis with potential application in cancer and cardiovascular study and tissue engineering vascularisation.

A synthetic oxygen carrier in fibrin matrices promotes sciatic nerve regeneration in rats

Tissue-engineering nerve conduits have been studied for a long time in bridging large nerve defects. However, the low oxygen availability within the nerve conduits, which results in death of migratory Schwann cells (SC) or loss of the newly formed tissue’s function, is still an obstacle for axonal regeneration. Thus, it was hypothesized that an oxygen-enriched conduit would enhance axonal regeneration and functional recovery in vivo. To address this issue, perfluorotributylamine (PFTBA) enriched fibrin hydrogel was prepared and injected into collagen–chitosan conduits. The conduit containing PFTBA-enriched fibrin hydrogel was then used to bridge a 12-mm sciatic nerve defect in rats. The control rats were bridged with collagen–chitosan conduits filled with fibrin matrices without PFTBA. It was found that axonal regeneration and functional recovery in the combined PFTBA group were significantly higher than those in the control group without PFTBA. Further investigations showed that the mRNA and protein levels of S-100, brain-derived neurotrophic factor and nerve growth factor were enhanced by PFTBA at 1 and 3weeks after surgery. However, the mRNA and protein levels of vascular endothelial growth factor were in a similar range between the combined PFTBA group and the control group without PFTBA. In addition, immunohistochemical results showed that the morphological appearances of regenerated nerve and survival of SC were enhanced by PFTBA at 4 and 12weeks after surgery. In conclusion, PFTBA-enriched nerve conduit is capable of enhancing axonal regeneration, which provides a new avenue for achieving better functional recovery in the treatment of nerve defect.

Cooperative Plasminogen Recruitment to the Surface of Streptococcus canis via M Protein and Enolase Enhances Bacterial Survival

ABSTRACTStreptococcus canis is a zoonotic pathogen capable of causing serious invasive diseases in domestic animals and humans. Surface-exposed M proteins and metabolic enzymes have been characterized as major virulence determinants in various streptococcal species. Recently, we have identified SCM, the M-like protein of S. canis, as the major receptor for miniplasminogen localized on the bacterial surface. The present study now characterizes the glycolytic enzyme enolase as an additional surface-exposed plasminogen-binding protein. According to its zoonotic properties, purified S. canis enolase binds to both human and canine plasminogen and facilitates degradation of aggregated fibrin matrices after activation with host-derived urokinase-type plasminogen activator (uPA). Unlike SCM, which binds to the C terminus of human plasminogen, the S. canis enolase interacts N terminally with the first four kringle domains of plasminogen, representing angiostatin. Radioactive binding analyses confirmed cooperative plasminogen recruitment to both surface-exposed enolase and SCM. Furthermore, despite the lack of surface protease activity via SpeB in S. canis, SCM is released and reassociated homophilically to surface-anchored SCM and heterophilically to surface-bound plasminogen. In addition to plasminogen-mediated antiphagocytic activity, reassociation of SCM to the bacterial surface significantly enhanced bacterial survival in phagocytosis analyses using human neutrophils.

Bridging the gap

In this study, Lu et al. investigated the ability of neural stem cells (NSCs) to repair the spinal cord following injury. Embryonic rat NSCs or human stem cell lines were embedded into fibrin matrices containing various growth factors and were grafted at spinal lesion sites in adult rats. After 7 weeks, around one-third of the grafted cells had differentiated into neurons, many of which extended axons that formed functional synapses with host neurons. Furthermore, axon outgrowth was found to be dependent on mammalian target of rapamycin signalling. Importantly, electrophysiological analysis suggested synaptic transmission and functional recovery of spinal cord relay circuits.

Long-Distance Growth and Connectivity of Neural Stem Cells after Severe Spinal Cord Injury

Neural stem cells (NSCs) expressing GFP were embedded into fibrin matrices containing growth factor cocktails and grafted to sites of severe spinal cord injury. Grafted cells differentiated into multiple cellular phenotypes, including neurons, which extended large numbers of axons over remarkable distances. Extending axons formed abundant synapses with host cells. Axonal growth was partially dependent on mammalian target of rapamycin (mTOR), but not Nogo signaling. Grafted neurons supported formation of electrophysiological relays across sites of complete spinal transection, resulting in functional recovery. Two human stem cell lines (566RSC and HUES7) embedded in growth-factor-containing fibrin exhibited similar growth, and 566RSC cells supported functional recovery. Thus, properties intrinsic to early-stage neurons can overcome the inhibitory milieu of the injured adult spinal cord to mount remarkable axonal growth, resulting in formation of new relay circuits that significantly improve function. These therapeutic properties extend across stem cell sources and species.

Platelet-rich plasma injections for tendinopathy and osteoarthritis

Tendinopathy and osteoarthritis are common chronic musculoskeletal conditions that are associated with frequent pain and reduced function. With the advent of autologous platelet-rich plasma (PRP), new opportunities are available to elucidate potential healing mechanisms and elaborate safe injection therapies. PRP therapy involves the use of autologous activated platelets retained in fibrin matrices as a source of growth factors and cytokines that are active in healing mechanisms, such as inflammation, angiogenesis, cell migration and proliferation. Here we provide an overview of the main components of PRP products relevant to the mechanism of action in tendinopathy and osteoarthritis, and emphasize the importance of identifying and exploiting principal molecular components in PRP for therapeutic benefit. We review the clinical applications of PRP in osteoarthritis and tendinopathy and discuss the current existing challenges.

Opticin Exerts Its Anti-angiogenic Activity by Regulating Extracellular Matrix Adhesiveness

Opticin is an extracellular matrix glycoprotein that we identified associated with the collagen network of the vitreous humor of the eye. Recently, we discovered that opticin possesses anti-angiogenic activity using a murine oxygen-induced retinopathy model: here, we investigate the underlying mechanism. Using an ex vivo chick chorioallantoic membrane assay, we show that opticin inhibits angiogenesis when stimulated by a range of growth factors. We show that it suppresses capillary morphogenesis, inhibits endothelial invasion, and promotes capillary network regression in three-dimensional matrices of collagen and Matrigel(TM). We then show that opticin binds to collagen and thereby competitively inhibits endothelial cell interactions with collagen via α(1)β(1) and α(2)β(1) integrins, thereby preventing the strong adhesion that is required for proangiogenic signaling via these integrins.

The attenuation of restenosis following arterial gene transfer using carbon nanotube coated stent incorporating TAT/DNAAng1+Vegf nanoparticles

This study report the development of a nanobiohybrid hydrogel based endovascular stent device capable of preventing postangioplasty in-stent restenosis (ISR) by promoting significant vascular endothelial recovery in a site-specific manner. The hydrogel is comprised of fibrin matrices, assembled layer-by-layer (LbL) on stent surface with alternate layers carrying endosomolytic Tat peptide/DNA nanoparticles (NPs) or NPs hybridized to polyacrylic acid (PAA) wrapped single-walled carbon nanotubes (NP–CNT). Here, the hydrogel works as a reservoir to carry, protect, and simultaneously deliver pro-angiogenic, vascular endothelial growth factor (Vegf) and Angiopoietin-1(Ang1), gene carrying NPs to the target site. In vitro results demonstrated that CNTs incorporated in the hydrogel layers play a major role in tuning the bioactivity of the stent. In addition, the developed stent formulation can significantly reduce the loss of therapeutics while traversing through the vessel and during deployment. In vivo experiments in balloon-injured canine femoral artery demonstrated that the NCS (+) group, carrying NPvegf+Ang1, can significantly enhance re-endothelialization of injured artery compared to control NCS (−), carrying NPNull, and bare metal stent (BMS) groups, attenuate stenosis (18.5±9.03% vs 39.56±13.8 vs 45.34±8.3%; n=8, p<0.05) and prevent neointima formation (1.53±0.36mm2 vs 2.51±0.27mm2 vs 2.66±0.14mm2; n=8, p<0.05) as analyzed angiography and histomorphometric analysis. These data collectively implicate that this new technology can be useful for stent and other biomedical devices through controlled delivery of multiple biotherapeutics.

Soft fibrin gels promote selection and growth of tumorigenic cells

The identification of stem-cell-like cancer cells through conventional methods that depend on stem-cell markers is often unreliable. We developed a mechanical method of selecting tumourigenic cells by culturing single cancer cells in fibrin matrices of ~100 Pa in stiffness. When cultured within these gels, primary human cancer cells or single cancer cells from mouse or human cancer cell lines grew within a few days into individual round colonies that resembled embryonic stem-cell colonies. Subcutaneous or intravenous injection of 10 or 100 fibrin-cultured cells in syngeneic or severe-combined-immunodeficiency mice led to the formation of solid tumours at the site of injection or at the distant lung organ much more efficiently than control cancer cells selected using conventional surface marker methods or cultured on conventional rigid dishes or on soft gels. Remarkably, as few as 10 such cells were able to survive and form tumours in the lungs of wild-type non-syngeneic mice.

Culture on fibrin matrices maintains the colony-forming capacity and osteoblastic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSC) are multipotent cells capable of differentiating into a number of mesenchymal tissues including bone, cartilage, and tendon. Low numbers in vivo means exponential growth is needed in culture to enable therapeutic applications. MSC can expand rapidly in culture but usually lose their extensive capacity for differentiation that makes them therapeutically attractive. To try and maintain their capacity for differentiation and expansion in vitro, we cultured MSC on fibrin gels of different concentrations to create more physiological growth conditions for the cells. The cells were then re-plated onto tissue culture plastic and analysed. The cells that had been pre-cultured for seven days on fibrin, proliferated and maintained their differential potential to the osteogenic lineage better than tissue culture plastic expanded MSC. A concentration relationship between colony number and fibrin concentration was seen with decreasing numbers as fibrin concentration increased. These data support the concept that substrate signals significantly influence MSC growth and differentiation and that growth on a fibrin matrix could be used to maintain a stem cell phenotype during MSC expansion.

Individual versus collective fibroblast spreading and migration: Regulation by matrix composition in 3D culture

Extracellular matrix (ECM) supplies both physical and chemical signals to cells and provides a substrate through which fibroblasts migrate during wound repair. To directly assess how ECM composition regulates this process, we used a nested 3D matrix model in which cell-populated collagen buttons were embedded in cell-free collagen or fibrin matrices. Time-lapse microscopy was used to record the dynamic pattern of cell migration into the outer matrices, and 3D confocal imaging was used to assess cell connectivity and cytoskeletal organization. Corneal fibroblasts stimulated with PDGF migrated more rapidly into collagen as compared to fibrin. In addition, the pattern of fibroblast migration into fibrin and collagen ECMs was strikingly different. Corneal fibroblasts migrating into collagen matrices developed dendritic processes and moved independently, whereas cells migrating into fibrin matrices had a more fusiform morphology and formed an interconnected meshwork. A similar pattern was observed when using dermal fibroblasts, suggesting that this response is not unique to corneal cells. We next cultured corneal fibroblasts within and on top of standard collagen and fibrin matrices to assess the impact of ECM composition on the cell spreading response. Similar differences in cell morphology and connectivity were observed – cells remained separated on collagen but coalesced into clusters on fibrin. Cadherin was localized to junctions between interconnected cells, whereas fibronectin was present both between cells and at the tips of extending cell processes. Cells on fibrin matrices also developed more prominent stress fibers than those on collagen matrices. Importantly, these spreading and migration patterns were consistently observed on both rigid and compliant substrates, thus differences in ECM mechanical stiffness were not the underlying cause. Overall, these results demonstrate for the first time that ECM protein composition alone (collagen vs. fibrin) can induce a switch from individual to collective fibroblast spreading and migration in 3D culture. Similar processes may also influence cell behavior during wound healing, development, tumor invasion and repopulation of engineered tissues.

Cytotoxic T Lymphocyte Trafficking and Survival in an Augmented Fibrin Matrix Carrier

Cell-based therapies have intriguing potential for the treatment of a variety of neurological disorders. One such example is genetically engineered cytotoxic T lymphocytes (CTLs) that are being investigated in brain tumor clinical trials. The development of methods for CTL delivery is critical to their use in the laboratory and clinical setting. In our study, we determined whether CTLs can migrate through fibrin matrices and if their migration, survival, and function could be modulated by adding chemokines to the matrix. Our results indicated that CTLs can freely migrate through fibrin matrices. As expected, the addition of the monocyte chemotactic protein-1 (MCP-1), also known as chemokine C-C motif ligand 2 (CCL2), to the surrounding media increased egress of the CTLs out of the fibrin clot. Interleukin (IL) -2 and/or IL-15 embedded in the matrix enhanced T cell survival and further promoted T cell migration. The interleukin-13 receptor alpha 2 specific (IL-13R alpha2) T cells that traveled out of the fibrin clot retained the capacity to kill U251 glioma cells. In summary, CTLs can survive and migrate robustly in fibrin matrices. These processes can be influenced by modification of matrix constituents. We conclude that fibrin matrices may be suitable T cell carriers and can be used to facilitate understanding of T cell interaction with the surrounding microenvironment.

The effects of the modulation of the fibronectin-binding capacity of fibrin by thrombin on osteoblast differentiation

Fibrin is a natural provisional matrix involved in wound healing and is widely utilized for tissue regeneration. The biological performance of fibrin is largely dependent on its composition and related structures. In this study, we examined the effect of thrombin, which is engaged with fibrin, on osteoblast differentiation and its mode of action. Fibrin matrices were prepared with different concentrations of thrombin, and MC3T3-E1 pre-osteoblasts were cultured on the fibrin matrices. Thrombin-promoted fibrin-enhanced osteoblast differentiation in a dose-dependent manner, as confirmed by the extent of calcium deposition, alkaline phosphatase activity, and the level of Runx2. The synthetic activating peptide of protease-activated receptor 1 (PAR1), a prototype receptor of thrombin in osteoblast, did not alter the level of Runx2. Instead, the thrombin that was engaged with fibrin in a dose-dependent manner increased the phosphorylation of integrins β1 and β3. The integrin-blocking peptide RGDS reduced the thrombin-enhanced Runx2 in the cells grown on fibrin, whereas the non-functional peptide RGES did not change the level of Runx2. Furthermore, thrombin dose-dependently increased the fibronectin-binding of fibrin. The thrombin-induced integrin phosphorylation and Runx2 expression were also attenuated through the use of a blocking peptide to inhibit the binding of fibronectin to fibrin. The results in this study provide evidence that thrombin engaged with fibrin accelerates osteoblast differentiation via integrins but not PAR1 by modulating the fibronectin-binding capacity of fibrin.

Embryonic Stem Cell-Based Cardiopatches Improve Cardiac Function in Infarcted Rats

Pluripotent stem cell-seeded cardiopatches hold promise for in situ regeneration of infarcted hearts. Here, we describe a novel cardiopatch based on bone morphogenetic protein 2-primed cardiac-committed mouse embryonic stem cells, embedded into biodegradable fibrin matrices and engrafted onto infarcted rat hearts. For in vivo tracking of the engrafted cardiac-committed cells, superparamagnetic iron oxide nanoparticles were magnetofected into the cells, thus enabling detection and functional evaluation by high-resolution magnetic resonance imaging. Six weeks after transplantation into infarcted rat hearts, both local (p < .04) and global (p < .015) heart function, as well as the left ventricular dilation (p < .0011), were significantly improved (p < .001) as compared with hearts receiving cardiopatches loaded with iron nanoparticles alone. Histological analysis revealed that the fibrin scaffolds had degraded over time and clusters of myocyte enhancer factor 2-positive cardiac-committed cells had colonized most of the infarcted myocardium, including the fibrotic area. De novo CD31-positive blood vessels were formed in the vicinity of the transplanted cardiopatch. Altogether, our data provide evidence that stem cell-based cardiopatches represent a promising therapeutic strategy to achieve efficient cell implantation and improved global and regional cardiac function after myocardial infarction.

Enhanced Angiogenic Efficacy through Controlled and Sustained Delivery of FGF-2 and G-CSF from Fibrin Hydrogels Containing Ionic-Albumin Microspheres

Neo-vessel formation in ischemic tissues relies on numerous growth factors and cell fractions for the formation of mature, stable, functional vasculature. However, the efforts to regenerate tissues typically rely on the administration of a single growth factor or cells alone. Conversely, polymeric matrices have been investigated extensively to deliver multiple growth factors at pre-determined rates to form stable blood vessels in ischemic tissues. We report on a novel sequential delivery system of a fibrin hydrogel containing ionic-albumin microspheres that allows for the controlled release of two growth factors. The use of this system was investigated in the context of therapeutic angiogenesis. Material properties were determined based on degree of swelling measurements and degradation characteristics. Release kinetics of model angiogenic polypeptides FGF-2 and G-CSF were determined using ELISA and the bioactivity of released protein was evaluated in human endothelial cell cultures. The release of growth factors from ionic-albumin microspheres was significantly delayed compared to the growth factor released from fibrin matrices in the absence of spheres. The scaffolds were implanted in a murine critical limb ischemia model at two concentrations, 40 ng (low) and 400 ng (high), restoring 92% of the blood flow in a normally perfused limb using a fibrin hydrogel releasing FGF-2 containing albumin–PLL microspheres releasing G-CSF (measured by LDPI at the high concentration), a 3.2-fold increase compared to untreated limbs. The extent of neo-vessel formation was delineated by immunohistochemical staining for capillary density (CD-31+) and mature vessel formation (α-SMA+). In conclusion, our study demonstrated that the release kinetics from our scaffold have distinct kinetics previously unpublished and the delivery of these factors resulted in hindlimb reperfusion, and robust capillary and mature vessel formation after 8 weeks compared to either growth factor alone or bolus administration of growth factor.

Engineered insulin-like growth factor-1 for improved smooth muscle regeneration

Insulin-like growth factor-1 (IGF-1) has been shown to induce potent mitogenic responses in various cell types, yet its sustained local delivery is still an underdeveloped domain in the clinic. We report here an engineered IGF-1 that facilitates extended local delivery to a site through its immobilization capacity within fibrin. Through recombinant fusion with a substrate sequence tag derived from α 2-plasmin inhibitor (α 2PI 1-8), the resulting variant, α 2PI 1-8–IGF-1, was covalently incorporated into fibrin matrices during normal thrombin/factor XIIIa-mediated polymerization. Bioactivity of the variant was confirmed to be equivalent to wild type (WT) IGF-1 via IGF-1 receptor phosphorylation and cell proliferation studies in urinary tract-derived cells in 2-D. Assessment of functional retention within 3-D fibrin matrices demonstrated that incorporation of α 2PI 1–8–IGF-1 induced a 1.3- and 1.5-fold more robust proliferative response in smooth muscle cells (SMCs) than WT IGF-1 and negative control matrices, respectively, when release was not contained. Sustained α 2PI 1–8–IGF-1 availability at bladder lesion sites in vivo evoked a considerable increase in SMC proliferation and a favorable host tissue response after 28 days in rats. We conclude that the sustained local IGF-1 availability from fibrin provided by our variant protein enhances smooth muscle regeneration better than the WT form of the protein.

Fibrin- and Collagen-Based Matrices Attenuate Inflammatory and Procoagulant Responses in Human Endothelial Cell Cultures Exposed toStaphylococcus aureus

Infective endocarditis (IE) remains a serious complication after heart valve replacement. Autologous valves constructed by matrix-based tissue engineering are under investigation to increase biocompatibility. The impact of the underlying matrix on the risk to develop IE is not known. The IE is characterized by bacterial adhesion and subsequent interactions of disseminating bacteria with endothelial cells (ECs) and monocytes, evoking endothelial proinflammatory and procoagulant activity, leading to heart valve destruction. In the current study, we, therefore, have seeded human ECs on a fibrin versus collagen gel matrix and, at confluence, infected them with Staphylococcus aureus, Streptococcus sanguis, and Staphylococcus epidermidis. Especially Sta. aureus infected ECs grown on fibrin (4.2% of the inoculum) and collagen (3.7%) matrices, more than on ECs grown on noncoated plates (1.2%; p<0.01). This was associated with higher monocyte adhesion (61%; p<0.01 on fibrin and 43%; p<0.05 on collagen) versus control cultures (30%), even at comparable EC surface expression of intercellular adhesion molecule-1 and vascular adhesion molecule-1. The collagen matrix attenuated the Sta. aureus-induced monocyte chemoattractant protein 1 expression 2.0-fold, compared with the noncoated control ECs. This reduction coincided with a 4.2-5.0-fold reduction of the procoagulant activity, triggered in ECs grown on noncoated wells, as a consequence of tissue factor (TF) expression by ECs, further stimulated by EC-bound monocytes. Overall, moderate responses were seen on infection with Str. sanguis and Sta. epidermidis for both gel matrices. Thus, even when fibrin and collagen gel matrices equally increase bacterial adhesion, and subsequent monocyte adhesion to infected ECs, these matrices modulate EC responses to these stimuli, thus resulting in attenuated cytokine production and attenuated adherent monocyte-dependent TF production by the ECs. Further investigations will need to confirm whether also in vivo, EC-matrix interactions can attenuate EC responses to bacteria and inflammatory cells to reduce IE at infected endovascular sites.