Biocompatibility assessment of polytetrafluoroethylene/wollastonite composites using endothelial cells and macrophages

The aim of the study was to prepare a composite of polytetrafluoroethylene/wollastonite (PTFE/W) and evaluate its biocompatibility with endothelial cells. A composite of PTFE with wollastonite in the proportion 90/10 w/w was prepared. The dynamic storage modulus of composite is found to increase from 260 to about 453 MPa at room temperature while a marginal increase is observed in the compressive modulus. Higher values of storage modulus of PTFE/W relative to pristine PTFE over a range of temperature indicated the contribution of wollastonite in improving the rigidity of PTFE. Electron microscopic visualization of composite surface indicates suitable morphology for cell growth with the cross-section showing no evidence of bonding between PTFE and wollastonite. The water contact angle of the composite indicates increased hydrophilicity over native PTFE due to the presence of wollastonite. A direct-contact test did not show any deleterious effects on endothelial cell morphology and viability, indicating its compatibility. Leached-out products (LOP) from the composite were determined to be non-toxic as tested by tetrazolium (MTT) and Neutral red uptake (NRU) assays. Mouse peritoneal macrophages cultured in the presence of the composites did not show upregulation of activation markers such as CD11b/CD18 (Mac-1), CD45, CD14, and CD86 (B7.2) in comparison to macrophages cultured in contact with PTFE alone, indicating its nonactivating nature. LOP did not induce proliferation of mouse splenic lymphocytes suggesting its immuno-tolerance. In static incubation assay contact with composite did not lead to hemolysis thus exhibiting preliminary hemocompatibility of the material. Suitable physico-chemical properties and well tolerance by endothelial cells and macrophages make this composite a prospective biomaterial. One could foresee the applications of this composite in areas where materials need to possess high rigidity and are subject to elevated temperatures.     

Preparation, characterization and in vitro biocompatibility evaluation of poly(butylene terephthalate)/wollastonite composites

The aim of the study was to prepare composites of poly(butylene terepthalate)/wollastonite (PBT/W), evaluate their properties and in vitro biocompatibility. Composites of PBT with wollastonite in two different proportions, viz. 70/30 (PW-30), 50/50 (PW-50) were prepared. The DSC studies indicate marginal changes in the melting behavior and enhanced crystallization in PBT/W composites. The mechanical properties of the composites such as tensile modulus shows remarkable improvement as a result of incorporation of wollastonite. SEM studies of fractured surfaces of impact samples showed no evidence of bonding between PBT and wollastonite. Water contact angle of PW30 and PW50 was 73.7 and 78.7, respectively. In vitro biocompatibility of PW-30 was evaluated as a representative composite. Direct cell contact test did not show deleterious effects on NIH3T3 fibroblast morphology and DNA integrity indicating its compatibility. Leach out products (LOP) of PW-30 were evaluated non-toxic as tested by MTT assay. Mouse peritoneal macrophages in contact with PW-30 showed comparable expression of CD 11b/18, CD45, CD14 and B7.2 to macrophages in contact with PTFE control indicating its non-activating nature. LOP did not induce proliferation of mouse splenic lymphocytes suggesting its immuno-tolerance. PW-30 also exhibited preliminary blood compatibility. These physical properties and biocompatibility of PBT/W composites show their suitability as potential biomaterials.     

Polyamide 6 composite membranes: properties and in vitro biocompatibility evaluation

The aim of the present study was to develop polyamide 6 membrane blended with gelatin and chondroitin sulfate using the phase precipitation method and evaluate its in vitro biocompatibility. Morphology of membranes was studied by laser scanning confocal microscopy which allowed the nondestructive visualization of internal bulk morphology of membranes. Membranes exhibited porous morphology with pores spanning across the membrane width with interconnections at various depths. Membranes showed adequate mechanical properties with tensile strengths of 20.10 +/- 0.64 MPa, % strain of 3.01+/-0.07, and modulus of 1082.50+/-23.50 MPa. In vitro biocompatibility of membranes by direct contact test did not show degenerative effects on NIH3T3 cells and also its leach-out products (LOP), as determined by tetrazolium (MTT) and neutral red uptake (NRU) assay. Mouse peritoneal macrophage cultured in contact with membranes and PTFE control showed comparable expression of activation markers such as CD11b/CD18, CD45, CD14, and CD86 suggesting the membranes' non-activating nature. Membrane LOP did not induce excessive proliferation of mouse splenocytes suggesting its non-antigenic nature. Preliminary blood compatibility of membranes was observed with no detectable hemolysis in static incubation assay. Taken collectively, the present data demonstrate that polyamide 6 composite membranes are biocompatible and prospective candidates for tissue engineering applications.     

Polyamide 6 composite membranes: Properties and in vitro biocompatibility evaluation

The aim of the present study was to develop polyamide 6 membrane blended with gelatin and chondroitin sulfate using the phase precipitation method and evaluate its in vitro biocompatibility. Morphology of membranes was studied by laser scanning confocal microscopy which allowed the nondestructive visualization of internal bulk morphology of membranes. Membranes exhibited porous morphology with pores spanning across the membrane width with interconnections at various depths. Membranes showed adequate mechanical properties with tensile strengths of 20.10 ± 0.64 MPa, % strain of 3.01±0.07, and modulus of 1082.50±23.50 MPa. In vitro biocompatibility of membranes by direct contact test did not show degenerative effects on NIH3T3 cells and also its leach-out products (LOP), as determined by tetrazolium (MTT) and neutral red uptake (NRU) assay. Mouse peritoneal macrophage cultured in contact with membranes and PTFE control showed comparable expression of activation markers such as CD11b/CD18, CD45, CD14, and CD86 suggesting the membranes' non-activating nature. Membrane LOP did not induce excessive proliferation of mouse splenocytes suggesting its non-antigenic nature. Preliminary blood compatibility of membranes was observed with no detectable hemolysis in static incubation assay. Taken collectively, the present data demonstrate that polyamide 6 composite membranes are biocompatible and prospective candidates for tissue engineering applications.     

Modulation of angiogenic functions in human macrophages by biomaterials

We examined the ability of polyvinylchloride (PVC), polytetrafluorethylene (PTFE) and tissue culture polystyrene (TCPS) to affect angiogenic functions in human monocyte-derived macrophages by measuring the mRNA expression of genes encoding angiogenic and anti-angiogenic molecules including basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and thrombospondin-1 (Tsp-1). The angiogenic activity of the corresponding macrophage conditioned media (CM) was measured by the proliferation of endothelial cells and the sprouting of new capillaries from fragments of human placental blood vessels. We determined that bFGF was not expressed in macrophages while VEGF and Tsp-1 mRNAs were expressed constitutively. Ang-1 was expressed in macrophages cultured up to 7 days on PTFE and TCPS independent of the culture stage. In contrast, macrophages cultured on PVC did not produce detectable amounts of Ang-1 mRNA after 7 days. CM from macrophages cultured either on PTFE or TCPS stimulated angiogenesis whereas CM from macrophages cultured on PVC inhibited it. The results demonstrate that polymers can cause differential expression of the angiogenic molecule Ang-1 in macrophages. They also induce different phenotypes of macrophages, which can either stimulate or inhibit angiogenesis suggesting a material-dependent influence on neovascularization.     

Plasma sprayed wollastonite/TiO2 composite coatings on titanium alloys

Wollastonite/TiO2 composite coatings were prepared using plasma spraying technology onto Ti-6Al-4V substrate. The composite coatings exhibit obvious lamellar structure with alternating wollastonite coating and TiO2 coating. No obvious cracks exist on the interface between coatings and substrate. In the case of composite coatings, the primarily crystalline phases of the coatings are wollastonite and rutile, indicating wollastonite and TiO2 did not react during plasma spraying process. Some of rutile in the powders transforms into anatase due to plasma spraying. The mean bond strength of the composite coatings is higher than 30 MPa. The Vickers microhardness of coatings increase with the increase in the content of TiO2. Wollastonite/TiO2 composite coatings were soaked in simulated body fluid to examine their bioactivity. Carbonate-containing hydroxyapatite (CHA) layer was formed on the surface of the wollastonite and W7T3 coatings soaked in simulated body fluid, while was not formed on the surface of the TiO2 and W3T7 coatings after immersion. In addition, a rich-silica layer appeared at the interface of CHA and wollastonite and W7T3 coatings. In order to investigate the cytocompatibility of the coatings, osteoblast was seeded onto the surface of the coatings. The scanning electron microscopy observation showed that the addition of wollastonite promote the proliferation of osteoblast. It is enough to prove that the wollastonite and wollastonite/TiO2 composite coatings possess excellent cytocompatibility.     

Is it possible to obtain "true endothelial progenitor cells" by in vitro culture of bone marrow mononuclear cells?

In vitro-cultured bone marrow cells have been shown to contain some low-density lipoprotein (LDL) uptake-positive cells. Although a small portion of LDL uptake-positive cells had expression for endothelial markers, all of them demonstrated a phagocytosis function similar to monocyte/macrophages and expression of the panleukocyte surface marker CD45 and monocyte marker CD14. These LDL uptake-positive cells did not show significant proliferative capacity and died out gradually in long-term culture. In contrast, the bone marrow-derived LDL uptake-negative cells showed strong proliferation and expression of typical mesenchymal surface markers CD29 and CD44. Although cultured under endothelial promoting conditions, these mesenchymal stem cells (MSCs) did not show any sign of differentiation toward endothelial cells. In conclusion, adult bone marrow-derived LDL uptake-positive cells that have been reported so far actually are monocytes/macrophages that can express some endothelial markers but are not "true endothelial progenitor cells" (EPCs). MSCs, which are the only cell type that shows strong proliferation during long-term adherent culture for bone marrow cells, do not differentiate toward the endothelial lineage when grown under endothelial promoting conditions.     

Effects of wollastonite on proliferation and differentiation of human bone marrow-derived stromal cells in PHBV/wollastonite composite scaffolds

In this study, the effects of wollastonite on proliferation and differentiation of human bone marrow-derived stromal cells (hBMSCs) have been investigated based on a polyhydroxybutyrate-co-hydroxyvalerate (PHBV)/ wollastonite (W) composite scaffolds system. Cell morphology, proliferation, and differentiation were measured. The results showed that the incorporation of wollastonite benefited hBMSCs adhesion, proliferation, and differentiation rate. In addition, an increase of proliferation and differentiation rate was observed when the wollastonite content in the PHBV/W composite scaffolds increased from 10 to 20 wt%. Based on our previous studies on PHBV/W composite discs, the differentiation measurements in this paper further proved that the wollastonite itself can stimulate the hBMSCs to differentiate toward osteoblasts without any osteogenic medium, and the ionic products (Ca and Si) released from wollastonite might contribute to this advantage. It is also suggested that the osteogenic differentiation of the hBMSCs can be affected by adjusting the wollastonite content in the composite scaffolds.     

Suitability of cellulose molecular dialysis membrane for bioartificial pancreas: in vitro biocompatibility studies

The success of immunoisolation devices for islet transplantation depends on the properties and biocompatibility of semipermeable immunobarrier membranes. In the present study, we have evaluated the in vitro biocompatibility of the cellulose membrane Spectra/Por 2 (MW no larger than 12- 14,000) for its possible application in islet immunoisolation. The membrane was found to be hydrophilic (octane contact angle: 153.2+/-0.66 degrees) and exhibited decreased protein adsorption. It showed mechanical stability after 1 month of storage in PBS (pH 7.4) with tensile strength, percent elongation, and Young's modulus of 88.88 MPa, 36.22, and 291.8 MPa, respectively. It allowed regulated transport of glucose and insulin in an in vitro diffusion assay. The high viability of NIH3T3 fibroblasts and the inability of lymphocytes to proliferate in vitro on exposure to the membrane leach-out products suggested its noncytotoxic and nonimmunogenic nature. Macrophages, when cultured on membranes, did not show increased expression of inflammatory surface marker such as CD11b/CD18, CD45, CD14, and B 7.2. Image analysis studies showed integrity and intact morphology of mouse islets cultured on and inside the membranes with high viability (91%, 89.7%). These islets also retained their functionality, as judged by insulin secretion. The present study provides sufficient documentation to consider cellulose molecular dialysis membrane Spectra/Por 2 (MW no larger than 12-14,000) as a potential candidate for immunoisolation of islets.     

CD40-CD154 interactions between macrophages and natural killer cells during sepsis are critical for macrophage activation and are not interferon gamma dependent

Natural killer (NK) cell interactions with macrophages have been shown to be important during bacterial sepsis in activating macrophages to improve bacterial clearance. The mechanism for this increased activation, however, is unclear. This study determines the relative roles of interferon (IFN)-gamma and CD40/CD154 direct cell interactions on macrophage and NK cell activation in an experimental model of sepsis. Splenic NK cells and peritoneal macrophages were isolated and cultured alone or in coculture, with and without LPS. CD69 expression on NK cells, phagocytosis ability of macrophages, and cell cytokine production was assessed at 24 and 48 h. Coculture of NK cells and macrophages significantly increased activation levels of both cell types, and through experiments culturing NK cells with supernatants from stimulated macrophages and macrophages with supernatants from stimulated NK cells, this activation was determined to be cell-contact-dependent. Similar experiments were conducted using NK cells from IFN-gamma deficient (-/-) mice, as well as anti-IFN-gamma neutralizing antibody. These experiments determined that IFN-gamma is not required for NK or macrophage activation, although it did augment activation levels. Experiments were again repeated using peritoneal macrophages from CD40-/- mice or splenic NK cells from CD154-/- mice. CD40/CD154 interactions were important in the ingestion of bacteria by macrophages, but did not affect NK cell activation at 24 h. There was, however, a protective effect of CD40/CD154 interactions on NK cell activation-induced cell death that occurred at 48 h. CD40/CD154 interactions between macrophages and NK cells are therefore important in macrophage phagocytosis, and are not dependent on IFN-gamma.     

Preparation and characterization of bioactive mesoporous wollastonite – Polycaprolactone composite scaffold

A well-defined mesoporous structure of wollastonite with high specific surface area was synthesized using surfactant P123 (triblock copolymer) as template, and its composite scaffolds with poly(?-caprolactone) (PCL) were fabricated by a simple method of solvent casting-particulate leaching. The measurements of the water contact angles suggest that the incorporation of either mesoporous wollastonite (m-WS) or conventional wollastonite (c-WS) into PCL could improve the hydrophilicity of the composites, and the former was more effective than the later. The bioactivity of the composite scaffold was evaluated by soaking the scaffolds in a simulated body fluid (SBF) and the results show that the m-WS/PCL composite (m-WPC) scaffolds can induce a dense and continuous layer of apatite after soaking for 1 week, as compared with the scattered and discrete apatite particles on the c-WS/PCL composite (c-WPC) scaffolds. The m-WPC had a significantly enhanced apatite-forming bioactivity compared with the c-WPC owing to the high specific surface area and pore volume of m-WS. In addition, attachment and proliferation of MG₆₃ cells on m-WPC scaffolds were significantly higher than that of c-WPC, revealing that m-WPC scaffolds had excellent biocompatibility. Such improved properties of m-WPC should be helpful for developing new biomaterials and may have potential use in hard tissue repair.     

Evidence that the Receptor for Soluble CD14:LPS Complexes may not be the Putative Signal-Transducing Molecule Associated with Membrane-Bound CD14

Membrane-bound CD14 acts as a receptor for lipopolysaccharide (LPS) on monocytes/macrophages and neutrophils. Studies have suggested that the activation of monocytes/macrophages by the binding of LPS to membrane-bound CD14 may require the association of a signal-transducing molecule with membrane-bound CD14. The observation that non-CD14 expressing cells, such as endothelial cells, can nevertheless be activated by a complex of LPS and a soluble form of CD14 (sCD14) suggests that the receptor for this complex may be identical to the signal transducing molecule associated with membrane-bound CD14. The studies described show that two CD14-specific MoAb are able to block the LPS-induced activation of endothelial cells but do not affect the response of monocytes to LPS. This suggests that the interaction of the sCD14:LPS complex with endothelial cells is distinct from the interaction of membrane-bound CD14 with its putative signal-transducing molecule.     

LNFPIII/LeX-stimulated macrophages activate natural killer cells via CD40-CD40L interaction

Lacto-N-fucopentaose III (LNFPIII) is a human milk sugar containing the biologically active Lewis X (LeX) trisaccharide. LNFPIII/LeX is also expressed by immunosuppressive helminth parasites, by bacteria, and on a number of tumor/cancer cells. In this report, we first demonstrate that LNFPIII activates macrophages in vitro as indicated by upregulation of Gr-1 expression on F4/80(+) cells. Further, we investigated the effect of LNFPIII-activated macrophages on NK cell activity. We found that LNFPIII-stimulated F4/80(+) cells were able to activate NK cells, inducing upregulation of CD69 expression and gamma interferon (IFN-gamma) production. The experiments show that NK cell activation is macrophage dependent, since NK cells alone did not secrete IFN-gamma in response to LNFPIII. Furthermore, we found that activation of NK cells by glycan-stimulated macrophages required cell-cell contact. As part of the cell-cell contact mechanism, we determined that CD40-CD40L interaction was critical for IFN-gamma secretion by NK cells, as the addition of anti-CD40L antibodies to the coculture blocked IFN-gamma production. We also demonstrated that LNFPIII-stimulated macrophages secrete prostaglandin E(2), interleukin-10 (IL-10), and tumor necrosis factor alpha (TNF-alpha) but a very low level of IL-12. Interestingly, addition of anti-TNF-alpha, anti-IL-10, or anti-IL-12 monoclonal antibodies did not significantly alter NK cell activity. Our data show that these soluble mediators are not critical for LNFPIII-stimulated macrophage activation of NK cells and provide further evidence for the importance of cell-cell contact and CD40-CD40L interactions between macrophages and NK cells.     

Flow and High Affinity Binding Affect the Elastic Modulus of the Nucleus,Cell Body and the Stress Fibers of Endothelial Cells

Cell mechanical properties are important in the adhesion of endothelial cells to synthetic vascular grafts exposed to shear flow. We hypothesized that the local apparent elastic modulus of the nucleus and the cell body would increase to a greater extent for cells adherent via the dual ligand (integrin-fibronectin/avidin-biotin) and exposed to flow, than for cells treated with either ligand alone. High affinity avidin-biotin bonds and in vitro flow exposure were used to improve adhesion to grafts thereby altering the mechanical properties of endothelial cells. Introduction of the dual ligand chemistry at the cell-substrate interface increased the apparent elastic modulus of the cells as compared to cells adherent with the fibronectin-integrin bonds only. Cells cultured on the dual ligand surface exhibited higher elastic moduli of the nucleus and cell body relative to cells cultured on fibronectin alone. Exposure of cells to flow increased the apparent elastic modulus of the cell body, nucleus, and stress fibers of cells adherent to the fibronectin surface. A similar effect was seen for cells adherent to the dual ligand surface, although there was little effect on the elastic modulus of the nucleus. While the dual ligand surface produces an increase in adhesion strength, focal contact area and elastic modulus, the change in elastic modulus after exposure to flow is due only to an increase in stress fibers and not an increase in contact area.     

Fabrication and characterization of bioactive wollastonite/PHBV composite scaffolds

Composite scaffolds of polyhydroxybutyrate-polyhydroxyvalerate (PHBV) with bioactive wollastonite were fabricated by a compression moulding, thermal processing, and salt particulate leaching method. Structure and mechanical properties of the scaffolds were determined. The bioactivity of the composites was evaluated by soaking in a simulated body fluid (SBF), and the formation of the hydroxyapatite (HAp) layer was determined by Scanning Electron Microscope (SEM) and Energy-Dispersive Spectrometer (EDS). The results showed that the wollastonite/PHBV composites were bioactive as it induced the formation of HAp on the surface of the composite scaffolds after soaking in SBF for 14 days. In addition, the measurements of the water contact angles suggested that incorporation of wollastonite into PHBV could improve the hydrophilicity of the composites and the enhancement was dependent on the wollastonite content. Furthermore, the pH and ion concentration changes of SBF solutions with composite scaffolds showed that the composites released Ca and Si ions, which could neutralize the acidic by-products of the PHBV and stabilize the pH of the SBF solutions between 7.2 and 7.8 within a 3-week soaking period. All of these results suggest that the incorporation of wollastonite was a useful approach to obtain composite scaffolds with improved properties.     

Free heme is a danger signal inducing expression of proinflammatory proteins in cultured cells derived from normal rat hearts

Endogenous molecules from damaged tissue act as danger signals to trigger or amplify the immune/inflammatory response. In this study, we examined whether free heme induced pro-inflammatory proteins in cultured cells derived from normal hearts and investigated the cells targeted by heme, together with its mechanism of action in these cells. We cultured collagenase-isolated heart-derived cells from normal rats and examined whether free heme induced pro-inflammatory proteins, reactive oxygen species (ROS) production and NF-κB activation, by quantitative RT-PCR, ELISA and flow cytometry. Free heme increased mRNA of various pro-inflammatory proteins in cultured cardiac resident cells (CCRC) (at least 100-fold) and induced intracellular ROS formation. Approximately 85-90% of CCRC are fibroblast/smooth muscle cells and 10-15% are CD11bc-positive macrophages; therefore to examine individual target cells, macrophage-deleted (CD11bc-negative) CCRC, primary cultured cells (cardiac fibroblasts, arterial smooth muscle cells and cardiac microvascular endothelial cells) and macrophage cells lines (NR8383) were similarly treated. Free heme activated NF-κB and induced expression of some pro-inflammatory proteins, including IL-1 and TNF-α in NR8383. On the other hand, macrophage-deleted CCRC strongly increased expression of these proteins on treatment with IL-1 or TNF-α, but not free heme. Induction of expression of pro-inflammatory proteins by free heme was not inhibited by intracellular ROS reduction, but by protease and proteasome inhibitors capable of regulating NF-κB. These data suggest that free heme strongly induces various pro-inflammatory proteins in injured hearts through NF-κB activation in cardiac resident macrophages and through cross-talk between macrophages and fibroblast/smooth muscle cells mediated inter alia by IL-1, TNF-α.     

The biology and tumour-related properties of monocyte tissue factor

Tissue factor (TF, coagulation factor III, CD142) is not only the main physiological initiator of normal blood coagulation, but is also important in the natural history of solid malignancies in that it potentiates metastasis and angiogenesis and mediates outside-in signalling. TF is expressed constitutively by many tissues which are not in contact with blood and by other cells upon injury or activation; the latter include endothelial cells, tissue macrophages, and peripheral blood monocytes. It can exist encrypted and unavailable functionally in the plasma membrane and the appearance of functional TF may be due to synthesis and/or de-encryption. Inflammatory cells often express TF and act to induce its production or de-encryption by other cells locally and, apparently, at remote sites. Inappropriate expression of TF by endothelial cells, macrophages or monocytes is thought to be an important trigger of coagulation in various pathological conditions. Several studies have shown that measurements of monocyte TF (mTF) may provide clinically significant information, particularly in patients with malignant and inflammatory diseases.     

Atheromatous plaque macrophages produce plasminogen activator inhibitor type-1 and stimulate its production by endothelial cells and vascular smooth muscle cells.

The capacity of macrophages to influence directly and indirectly fibrinolytic processes in atherosclerosis was studied using macrophages isolated from atherosclerotic plaques of patients undergoing surgical repair of distal aortic and femoral arteries. These cells were characterized by their morphology, adherence, esterase positivity, and expression of CD14 antigen. Production of plasminogen activator inhibitor type-1 (PAI-1) by plaque macrophages (6.7 +/- 2.7 ng/10(5) cells/24 hours [mean +/- SEM]) was significantly greater than PAI-1 production by blood monocytes isolated simultaneously from the same patients (1.8 +/- 1.5 ng/10(5) cells/24 hours). Production of tissue type plasminogen activator and urokinase type was not augmented compared to blood monocytes. Conditioned medium from cultured plaque macrophages significantly increased production of PAI-1 by endothelial cells (85 +/- 11% above basal) and vascular smooth muscle cells (25 +/- 10%) in vitro. This response was significantly greater than the response to monocyte-conditioned medium (endothelial cells 38 +/- 11%, vascular smooth muscle cells 2.5 +/- 2.0%). Stimulation of endothelial cell PAI-1 production by macrophage-conditioned medium was partially inhibitable by a monoclonal antibody to transforming growth factor-beta. Tissue type plasminogen activator production by endothelial cells and vascular smooth muscle cells was not affected by plaque macrophage- or monocyte-conditioned medium. Urokinase type plasminogen activator production by endothelial cells and vascular smooth muscle cells was undetectable in control medium and was augmented to similar levels in response to plaque macrophage- and monocyte-conditioned media. These results demonstrate upregulation of PAI-1 production by macrophages in atheromatous plaques and the capacity of soluble products from plaque macrophages to upregulate PAI-1 production by endothelial cells and vascular smooth muscle cells in vitro. These data suggest that macrophages in atherosclerotic plaques may inhibit thrombolysis both directly and indirectly by effects of their soluble products on endothelial cells and vascular smooth muscle cells.     

紫外线对两种聚四氟乙烯电荷储存稳定性的影响

利用在室温下的栅控恒压电晕充电后经不同强度紫外线辐照的表面电位测量,研究了紫外线对聚四氟乙烯(polytetrafluoroethylene,PTFE)多孔膜、聚四氟乙烯非多孔膜驻极体电荷储存稳定性的影响,探讨了两种聚四氟乙烯驻极体医疗产品使用紫外消毒方法的可行性.结果:(1)在常温条件下,紫外线辐照对两种聚四氟乙烯驻极体的电荷储存稳定性的影响不大;(2)聚四氟乙烯多孔膜驻极体的电荷储存能力随环境湿度的提高而略有下降;(3)聚四氟乙烯医用驻极体产品可采用紫外消毒法消毒.     

Human blood-derived macrophages enhance barrier function of cultured primary bovine and human brain capillary endothelial cells

The characteristic properties of the blood-brain barrier (BBB) forming brain capillary endothelial cells (BCEC) are modulated by their microenvironment, but the cellular sources of the induction signals are still unclear. Apart from astrocytes, another cell type in close contact with cerebral blood vessels is the perivascular macrophages, which are known to be regularly replaced by blood-derived monocytic precursor cells. It is unknown if, and how, these cells may interact with the cerebral endothelium and modulate its BBB-specific functions. In the present study, a cell culture model of the BBB was used to investigate the effect of blood-derived human macrophages on the permeability of cultured bovine and human BCEC, determined by a transendothelial electrical resistance (TEER) measurement. We found that the TEER of postconfluent BCEC was considerably increased by a non-contact coculture with macrophages. After 24 h, we found a TEER augmentation of over 50 % compared with the control without coculture, and this effect was comparable to the response of BCEC to a C6 glioma cells coculture. Stimulation or HIV-1 infection of the macrophages did not alter their effect on BCEC monolayer permeability. Investigation of signal transduction pathways showed that TEER increase of BCEC due to macrophage coculture was cAMP-independent and involves neither phospholipase C, protein kinase C nor calmodulin. Our findings demonstrate that macrophages are able to modulate BBB-specific functions in cultured BCEC. Thus, these cells or cerebral cells of monocytic origin (e.g. perivascular macrophages), may be part of the microenvironment of BCEC that modulates their specific properties in vivo .