运用植块法培养脑微血管内皮细胞

探讨简易可行的脑微血管内皮细胞(brain microvascular endothelial cells,BMECs培)养方法,为研究BMECs细胞在脑血管疾病中的重要作用提供技术支持。分离出生后1~7天内的SD乳鼠大脑皮质区,植块法培养BMECs细胞。用倒置显微镜观察BMECs细胞的形态以及从皮质块迁出的过程;MTT比色法检测BMECs细胞的生长曲线;采用免疫组化染色检测VIII因子相关抗原和CD34抗原,以鉴定内皮细胞。结果发现,大脑皮质块植块法培养的大鼠BMECs细胞呈单层贴壁生长,细胞形态以长梭形、多角形三角形、四边形为主,呈典型的“铺路石”样征象,经鉴定为内皮细胞,第三代纯度达95%以上。提示该方法具有经济、简便、要求条件不高,易于纯化的优点,可作为大鼠BMECs细胞体外培养的良好模型。     

大鼠脑微血管内皮细胞培养及其药物转运体Oatp2和P-gp的表达

贴块法培养脑微血管内皮细胞(BMECs),倒置显微镜动态观察细胞生长及形态,Ⅷ因子相关抗原、CD34免疫细胞化学联合鉴定细胞并确定纯度。免疫细胞化学和Western印迹法检测药物转运体有机阴离子转运多肽亚型2(Oatp2)及P-糖蛋白(P-gp)在培养内皮细胞上的表达。结果显示,获得的BMECs呈多角形或铺路石形,单层贴壁生长;培养细胞Ⅷ因子相关抗原免疫细胞化学、CD34免疫荧光染色均为阳性,细胞纯度90%;培养细胞有Oatp2及P-gp表达,且二者均主要表达于BMECs细胞膜。提示贴块法可获得原代培养BMECs,方法简便易行,细胞纯度较高。原代培养的BMECs上有药物转运体Oatp2及P-gp的表达,为血脑屏障上药物转运体的体外研究提供了可能途径。     

Isolation of Primary Murine Brain Microvascular Endothelial Cells

The blood-brain-barrier is ultrastructurally assembled by a monolayer of brain microvascular endothelial cells (BMEC) interconnected by a junctional complex of tight and adherens junctions. Together with other cell-types such as astrocytes or pericytes, they form the neurovascular unit (NVU), which specifically regulates the interchange of fluids, molecules and cells between the peripheral blood and the CNS. Through this complex and dynamic system BMECs are involved in various processes maintaining the homeostasis of the CNS. A dysfunction of the BBB is observed as an essential step in the pathogenesis of many severe CNS diseases. However, specific and targeted therapies are very limited, as the underlying mechanisms are still far from being understood. Animal and in vitro models have been extensively used to gain in-depth understanding of complex physiological and pathophysiological processes. By reduction and simplification it is possible to focus the investigation on the subject of interest and to exclude a variety of confounding factors. However, comparability and transferability are also reduced in model systems, which have to be taken into account for evaluation. The most common animal models are based on mice, among other reasons, mainly due to the constantly increasing possibilities of methodology. In vitro studies of isolated murine BMECs might enable an in-depth analysis of their properties and of the blood-brain-barrier under physiological and pathophysiological conditions. Further insights into the complex mechanisms at the BBB potentially provide the basis for new therapeutic strategies.This protocol describes a method to isolate primary murine microvascular endothelial cells by a sequence of physical and chemical purification steps. Special considerations for purity and cultivation of MBMECs as well as quality control, potential applications and limitations are discussed.     

大肠杆菌yijP侵袭蛋白诱导人脑微血管内皮细胞凋亡

为研究大肠杆菌的脑微血管内皮细胞侵袭基因yijP的功能,将yijP基因（1．04kb）克隆到pQE30表达载体,构建表达产物为N末端带有6个组氨酸（His）序列的yijP汇合蛋白,以M15（pREP4）为受体菌,大量表达（His）6-yijP汇合蛋白,利用Ni—NTA亲和层析纯化汇合蛋白,将经透析法复性的一定浓度的（His）6-yijP蛋白加入到体外培养的人脑微血管内皮细胞中,结果显示yijP蛋白对人脑微血管内皮细胞有较强的细胞毒作用：在相差显微镜下可观察到细胞皱缩、胞膜呈泡状膨出,随着时间延长细胞逐渐脱落;荧光显微镜下可见细胞核呈现为致密团块状或圆形浓染颗粒状,呈凋亡样改变：DNA琼脂糖凝胶电泳可见DNA阶梯状条带;流式细胞仪显示在正常二倍体峰之前出现一个亚二倍体峰;Western印迹可检测到caspase-3的活性片段。这些现象均出现在yijP蛋白作用于人脑微血管内皮细胞的16h之后,提示在大肠杆菌侵袭人脑微血管内皮细胞过程中,yijP蛋白可能起到诱导脑微血管内皮细胞迟发性凋亡的毒素作用。     

Long-Term Infection and Transformation of Dermal Microvascular Endothelial Cells by Human Herpesvirus 8

Human herpesvirus 8 (HHV8) infects Kaposi's sarcoma (KS) spindle cells in situ, as well as the lesional endothelial cells considered to be spindle cell precursors. The HHV8 genome contains several oncogenes, suggesting that infection of endothelial and spindle cells could induce cellular transformation and tumorigenesis and promote the formation of KS lesions. To investigate the potential of HHV8 infection of endothelial cells to contribute to the development of KS, we have developed an in vitro model utilizing dermal microvascular endothelial cells that support significant HHV8 infection. In contrast to existing in vitro systems used to study HHV8 pathogenesis, the majority of dermal endothelial cells are infected with HHV8 and the viral genome is maintained indefinitely. Infection is predominantly latent, with a small percentage of cells supporting lytic replication, and latency is responsive to lytic induction stimuli. Infected endothelial cells develop a spindle shape resembling that of KS lesional cells and show characteristics of a transformed phenotype, including loss of contact inhibition and acquisition of anchorage-independent growth. These results describe a relevant model system in which to study virus-host interactions in vitro and demonstrate the ability of HHV8 to induce phenotypic changes in infected endothelial cells that resemble characteristics of KS spindle cells in vivo. Thus, our results are consistent with a direct role for HHV8 in the pathogenesis of KS.     

Differential Activation of Acid Sphingomyelinase and Ceramide Release Determines Invasiveness of Neisseria meningitidis into Brain Endothelial Cells

The interaction with brain endothelial cells is central to the pathogenicity of Neisseria meningitidis infections. Here, we show that N. meningitidis causes transient activation of acid sphingomyelinase (ASM) followed by ceramide release in brain endothelial cells. In response to N. meningitidis infection, ASM and ceramide are displayed at the outer leaflet of the cell membrane and condense into large membrane platforms which also concentrate the ErbB2 receptor. The outer membrane protein Opc and phosphatidylcholine-specific phospholipase C that is activated upon binding of the pathogen to heparan sulfate proteoglycans, are required for N. meningitidis-mediated ASM activation. Pharmacologic or genetic ablation of ASM abrogated meningococcal internalization without affecting bacterial adherence. In accordance, the restricted invasiveness of a defined set of pathogenic isolates of the ST-11/ST-8 clonal complex into brain endothelial cells directly correlated with their restricted ability to induce ASM and ceramide release. In conclusion, ASM activation and ceramide release are essential for internalization of Opc-expressing meningococci into brain endothelial cells, and this segregates with invasiveness of N. meningitidis strains.     

Tetramethylpyrazine Protects Against Oxygen-Glucose Deprivation-Induced Brain Microvascular Endothelial Cells Injury via Rho/Rho-kinase Signaling Pathway

Tetramethylpyrazine (TMP, also known as Ligustrazine), which is isolated from Chinese Herb Medicine Ligustium wollichii Franchat (Chuan Xiong), has been widely used in China for the treatment of ischemic stroke by Chinese herbalists. Brain microvascular endothelial cells (BMECs) are the integral parts of the blood–brain barrier (BBB), protecting BMECs against oxygen-glucose deprivation (OGD) which is important for the treatment of ischemic stroke. Here, we investigated the protective mechanisms of TMP, focusing on OGD-injured BMECs and the Rho/Rho-kinase (Rho-associated kinases, ROCK) signaling pathway. The model of OGD-injured BMECs was established in this study. BMECs were identified by von Willebrand factor III staining and exposed to fasudil, or TMP at different concentrations (14.3, 28.6, 57.3 µM) for 2 h before 24 h of OGD injury. The effect of each treatment was examined by cell viability assays, measurement of intracellular reactive oxygen species (ROS), and transendothelial electric resistance and western blot analysis (caspase-3, endothelial nitric oxide synthase (eNOS), RhoA, Rac1). Our results show that TMP significantly attenuated apoptosis and the permeability of BMECs induced by OGD. In addition, TMP could notably down-regulate the characteristic proteins in Rho/ROCK signaling pathway such as RhoA and Rac1, which triggered abnormal changes of eNOS and ROS, respectively. Altogether, our results show that TMP has a strong protective effect against OGD-induced BMECs injury and suggest that the mechanism might be related to the inhibition of the Rho/ROCK signaling pathway.     

The Contribution of TRPV4-Mediated Calcium Signaling to Calcium Homeostasis in Endothelial Cells

A large variety of cation transport systems are involved in the regulation of calcium homeostasis in endothelial cells. The focus of the present study is to determine the contribution of nonselective cation channels from the TRP (transient receptor potential) family to cellular calcium homeostasis of porcine aortic endothelial cells (PAEC). One member of the TRPV (vanniloid) subfamily, TRPV4, has previously been shown to be involved in cation transport induced by a large variety of stimulations including osmolarity, temperature, mechanical stress, and phosphorylation. Here, we demonstrate the existence of several TRP proteins, including TRPV4, in PAEC using RT-PCR. To test whether this channel is functional, we performed FURA-2 calcium measurements and whole-cell patch-clamp experiments. We observed the induction of large calcium signals following mechanical stress, altered extracellular temperature, and the selective TRPV4 activator 4-α -PDD. These effects were diminished in the presence of the TRPV4 inhibitor miconazole, suggesting the involvement of this channel in mediating endothelial calcium signals. The large amounts of transported calcium and the short signaling ways suggest a potentially important role of this channel in many physiological processes.     

Integrin-mediated Signaling Events in Human Endothelial Cells

Vascular endothelial cells are important in a variety of physiological and pathophysiological processes. The growth and functions of vascular endothelial cells are regulated both by soluble mitogenic and differentiation factors and by interactions with the extracellular matrix; however, relatively little is known about the role of the matrix. In the present study, we investigate whether integrin-mediated anchorage to a substratum coated with the extracellular matrix protein fibronectin regulates growth factor signaling events in human endothelial cells. We show that cell adhesion to fibronectin and growth factor stimulation trigger distinct initial tyrosine phosphorylation events in endothelial cells. Thus, integrin-dependent adhesion of endothelial cells leads to tyrosine phosphorylation of both focal adhesion kinase and paxillin, but not of several growth factor receptors. Conversely, EGF stimulation causes receptor autophosphorylation, with no effect on focal adhesion kinase or paxillin tyrosine phosphorylation. Adhesion to fibronectin, in the absence of growth factors, leads to activation of MAPK. In addition, adhesion to fibronectin also potentiates growth factor signaling to MAPK. Thus, polypeptide growth factor activation of MAPK in anchored cells is far more effective than in cells maintained in suspension. Other agonists known to activate MAPK were also examined for their ability to activate MAPK in an anchorage-dependent manner. The neuropeptide bombesin, the bioactive lipid lysophosphatidic acid (LPA), and the cytokine tumor necrosis factor α, which signal through diverse mechanisms, were all able to activate MAPK to a much greater degree in fibronectin-adherent cells than in suspended cells. In addition, tumor necrosis factor α activation of c-Jun kinase (JNK) was also much more robust in anchored cells. Together, these data suggest a cooperation between integrins and soluble mitogens in efficient propagation of signals to downstream kinases. This cooperation may contribute to anchorage dependence of mitogenic cell cycle progression.     

Epithelial Ovarian Cancer-Induced Angiogenic Phenotype of Human Omental Microvascular Endothelial Cells May Occur Independently of VEGF Signaling

Epithelial ovarian cancer (EOC) metastasizes transcoelomically to the peritoneum and omentum, and despite surgery and chemotherapy, recurrent disease is likely. Metastasis requires the induction of proangiogenic changes in the omental microenvironment and EOC-induced omental angiogenesis is currently a key therapeutic target. In particular, antiangiogenic therapies targeting the vascular endothelial growth factor A (VEGFA) pathway are commonly used, although, with limited effects. Here, using human omental microvascular endothelial cells (HOMECs) and ovarian cancer cell lines as an in vitro model, we show that factors secreted from EOC cells increased proliferation, migration, and tube-like structure formation in HOMECs. However, EOC-induced angiogenic tube-like formation and migration were unaffected by inhibition of tyrosine kinase activity of VEGF receptors 1 and 2 (Semaxanib; SU5416) or neutralization of VEGFA (neutralizing anti-VEGFA antibody), although VEGFA₁₆₅-induced HOMEC migration and tube-like structure formation were abolished. Proteomic investigation of the EOC secretome identified several alternative angiogenesis-related proteins. We screened these for their ability to induce an angiogenic phenotype in HOMECs, i.e., proliferation, migration, and tube-like structure formation. Hepatocyte growth factor (HGF) and insulin-like growth factor binding protein 7 (IGFBP-7) increased all three parameters, and cathepsin L (CL) increased migration and tubule formation. Further investigation confirmed expression of the HGF receptor c-Met in HOMECs. HGF- and EOC-induced proliferation and angiogenic tube structure formation were blocked by the c-Met inhibitor PF04217903. Our results highlight key alternative angiogenic mediators for metastatic EOC, namely, HGF, CL, and IGFBP-7, suggesting that effective antiangiogenic therapeutic strategies for this disease require inhibition of multiple angiogenic pathways.     

Glycosyltransferase Activities in Cultured Endothelial Cells of Bovine Brain Microvascular Origin

Bovine brain microvascular endothelial cells (BMECs) express GM3 (NeuAc) and GM3 (NeuGc) as the major gangliosides, and GM1, GD1a, GD1b, GT1b as well as sialosylparagloboside and sialosyllactosaminylparagloboside as the minor species. To investigate the metabolic basis of this ganglioside pattern, the activities of eight glycosyltransferases (GM3-, GD1a-, GD3-, LM1-, GM2 (NeuAc)-, GM2 (NeuGc)-, LacCer-, and GM1-synthases) in cultured BMECs were studied. It was found that BMECs possessed high activities of GM3- and GD1a-synthases, and low activities of GM2-, GM1-, and GD3-synthases. Thus, the present study provides evidence that endothelial cells are capable of synthesizing gangliosides in situ and that the high content of GM3 in BMEC is closely associated with high activities of GM3-synthase and low activities of GM2-, GM1-, and GD3-synthases.     

Synthesis of Apolipoprotein A-1 in Pig Brain Microvascular Endothelial Cells

In an approach toward the identification of hitherto unknown proteins involved in the function of the blood-brain barrier, we constructed a pig brain microvessel-derived cDNA library that is enriched in blood-brain barrier specific sequences by means of subtractive cloning. Sequence analysis of selected clones revealed that one of the cDNAs encoded porcine apolipoprotein (apo) A-1. The identity of apo A-1 mRNA was further confirmed by in vitro translation of RNA from brain microvascular endothelial cells and subsequent immunoprecipitation with an antibody against human apo A-1. We further investigated the expression of apo A-1 mRNA in several tissues and in endothelial cells of the pig. It is shown that cultured brain microvascular endothelial cells provide an in vitro model to study the expression and function of apo A-1 in the microvasculature of the brain.     

Neisseria meningitidis Induces Brain Microvascular Endothelial Cell Detachment from the Matrix and Cleavage of Occludin: A Role for MMP-8

Disruption of the blood-brain barrier (BBB) is a hallmark event in the pathophysiology of bacterial meningitis. Several inflammatory mediators, such as tumor necrosis factor alpha (TNF-α), nitric oxide and matrix metalloproteinases (MMPs), contribute to this disruption. Here we show that infection of human brain microvascular endothelial cells (HBMEC) with Neisseria meningitidis induced an increase of permeability at prolonged time of infection. This was paralleled by an increase in MMP-8 activity in supernatants collected from infected cells. A detailed analysis revealed that MMP-8 was involved in the proteolytic cleavage of the tight junction protein occludin, resulting in its disappearance from the cell periphery and cleavage to a lower-sized 50-kDa protein in infected HBMEC. Abrogation of MMP-8 activity by specific inhibitors as well as transfection with MMP-8 siRNA abolished production of the cleavage fragment and occludin remained attached to the cell periphery. In addition, MMP-8 affected cell adherence to the underlying matrix. A similar temporal relationship was observed for MMP activity and cell detachment. Injury of the HBMEC monolayer suggested the requirement of direct cell contact because no detachment was observed when bacteria were placed above a transwell membrane or when bacterial supernatant was directly added to cells. Inhibition of MMP-8 partially prevented detachment of infected HBMEC and restored BBB permeability. Together, we established that MMP-8 activity plays a crucial role in disassembly of cell junction components and cell adhesion during meningococcal infection.     

Reoxygenation Injury of Human Brain Capillary Endothelial Cells

1. Many studies have demonstrated that endothelial cells from several species can generate oxygen free radicals when subjected to anoxia and reoxygenation. However, due to the heterogeneity of the endothelium within different organs and species, the effects of superoxide dismutase (SOD), catalase, and allopurinol on reoxygenated cultured cells remain quite controversial.2. This review outlines the possible sources of oxygen free radicals within brain endothelial cells.3. We examine the aspects of the effects of SOD catalase and allopurinol on cultured human brain capillary endothelial cells upon reoxygenation.4. Also, we introduce briefly a method of culturing human brain capillary endothelial cells and present our experimental results on the effects of SOD, catalase, and allopurinol in these cultured cells following anoxia and reoxygenation.     

The Involvement of CXCL11 in Bone Marrow-Derived Mesenchymal Stem Cell Migration Through Human Brain Microvascular Endothelial Cells

Bone marrow-derived mesenchymal stem cells (MSCs) transplant into the brain, where they play a potential therapeutic role in neurological diseases. However, the blood–brain barrier (BBB) is a native obstacle for MSCs entry into the brain. Little is known about the mechanism behind MSCs migration across the BBB. In the present study, we modeled the interactions between human MSCs (hMSCs) and human brain microvascular endothelial cells (HBMECs) to mimic the BBB microenvironment. Real-time PCR analysis indicated that the chemokine CXCL11 is produced by hMSCs and the chemokine receptor CXCR3 is expressed on HBMECs. Further results indicate that CXCL11 secreted by hMSCs may interact with CXCR3 on HBMECs to induce the disassembly of tight junctions through the activation of ERK1/2 signaling in the endothelium, which promotes MSCs transendothelial migration. These findings are relevant for understanding the biological responses of MSCs in BBB environments and helpful for the application of MSCs in neurological diseases.     

应用激光共聚焦扫描显微镜技术检测缺氧人肺微血管内皮细胞内钙离子浓度动态变化

目的：探讨应用激光共聚焦扫描显微镜（LSCM）技术检测缺氧状态的人肺微血管内皮细胞（HPMVEC）内钙离子（Ca2＋）浓度动态变化的价值。方法：HPMVEC常规培养,按观察时间点不同分为5个缺氧培养组（1h hyp组、2h hyp组、4h hyp组、6h hyp组和8h hyp组）以及1个对照组（0h con组）共6个组,每组设8个复孔,应用LSCM技术测定缺氧后HPMVEC内Ca2＋浓度水平及随时间推移的变化。结果：LSCM技术显示HPMVEC内Ca2＋的荧光强度1h hyp组与0h con组比较、2h hyp组与1h hyp组比较、4h hyp组与2h hyp组比较、6h hyp组与4h hyp组比较、8h hyp组与6h hyp组比较有显著差异（P〈0.05）。线性回归分析结果显示Ca2＋荧光强度与缺氧时间成正相关（r=0.969,P〈0.01）。结论：HPMVEC内Ca2＋浓度随缺氧时间增长而增高;LSCM在动态检测缺氧状态下HPMVEC内的Ca2＋浓度变化中具有明显优势。     

钙离子浓度动态变化

目的:探讨应用激光共聚焦扫描显微镜(LSCM)技术检测缺氧状态的人肺微血管内皮细胞(HPMVEC)内钙离子(Ca2+)浓度动态变化的价值。方法:HPMVEC常规培养,按观察时间点不同分为5个缺氧培养组(1h hyp组、2h hyp组、4h hyp组、6h hyp组和8h hyp组)以及1个对照组(0h con组)共6个组,每组设8个复孔,应用LSCM技术测定缺氧后HPMVEC内Ca2+浓度水平及随时间推移的变化。结果:LSCM技术显示HPMVEC内Ca2+的荧光强度1h hyp组与0h con组比较、2h hyp组与1h hyp组比较、4h hyp组与2h hyp组比较、6h hyp组与4h hyp组比较、8h hyp组与6h hyp组比较有显著差异(P<0.05)。线性回归分析结果显示Ca2+荧光强度与缺氧时间成正相关(r=0.969,P<0.01)。结论:HPMVEC内Ca2+浓度随缺氧时间增长而增高;LSCM在动态检测缺氧状态下HPMVEC内的Ca2+浓度变化中具有明显优势。