The role of vascular endothelial cells in transplantation.

The interface between an allograft and the recipient's immune system is the endothelium of the allograft vasculature. In this boundary position, endothelial cells may play important roles in the afferent and efferent phases of allograft rejection, in the response of the allograft to pretransplant perfusion and to drug therapy, and in the response to viral infection of the host. The expression by endothelial cells of granule membrane protein-140 (GMP-140) and endothelial leukocyte adhesion molecule-1 (ELAM-1), increased tissue factor activity, increased secretion of plasminogen activator inhibitor, and decreased thrombomodulin may all contribute to hyperacute rejection. Similarly, endothelial cells may actively participate in acute cellular rejection and in the development of transplant-associated arteriopathy as a result of induction of antigen-presenting function (ie, HLA class II expression), upregulation of adhesion molecules for lymphocytes and monocytes, and release of platelet-derived growth factors. Endothelial cell functions, which are important for normal inflammatory responses and vessel behavior, may be pathogenic in the allograft.     

The role of vascular endothelial cells in tumor metastasis

Vascular endothelial cells (VECs) are an integral component of the inner lining of blood vessels, and their functions are essential for the proper functioning of the vascular system. The tight junctions formed by VECs act as a significant barrier to the intravasation and extravasation of tumor cells (TCs). In addition to that, the proliferation, activation, and migration of VECs play a vital role in the growth of new blood vessels, a process known as tumor angiogenesis, which is closely related to the malignant progression of tumors. However, during tumor progression, VECs undergo endothelial-to-mesenchymal transition (EndMT), which further promotes tumor progression. Furthermore, VECs act as the first line of defense against effector immune cells and help prevent immune cells from infiltrating into tumor tissues. VECs also secrete various cytokines that can contribute to regulating the stemness of tumor stem cells. Thus, it has been increasingly recognized that dysfunction of VECs is one of the key driving forces behind tumor metastasis, and therapeutic strategies targeting VECs have the potential to be an effective means of antitumor therapy. This review aims to present a comprehensive overview of the role and mechanisms of VECs in regulating tumor progression and metastasis, providing insights into the possibilities for the development of novel antitumor therapies that target VECs.     

Paracrine mechanisms of endothelial progenitor cells in vascular repair

Endothelial progenitor cells (EPCs) play an important role in repairing damaged blood vessels and promoting neovascularization. However, the specific mechanism of EPCs promoting vascular repair is still unclear. Currently, there are two different views on the repair of damaged vessels by EPCs, one is that EPCs can directly differentiate into endothelial cells (ECs) and integrate into injured vessels, the other is that EPCs act on cells and blood vessels by releasing paracrine substances. But more evidence now supports the latter. Therefore, the paracrine mechanisms of EPCs are worth further study. This review describes the substances secreted by EPCs, some applications based on paracrine effects of EPCs, and the studies of paracrine mechanisms in cardiovascular diseases--all of these are to support the view that EPCs repair blood vessels through paracrine effects rather than integrating directly into damaged vessels.     

循环血管内皮祖细胞血管修复作用的研究进展

循环内皮祖细胞在血管损伤的情况下,可归巢到受损区域,增殖分化为成熟内皮细胞,并分泌营养因子,促进内皮新生。但是,由于其干细胞特性,在微环境改变的情况下,可能无法分化为功能细胞,甚至表达纤维化、成骨分化等表型,加速血管损伤。因此,纯化单一细胞群,稳定微环境,明确病程是决定循环内皮祖细胞发挥积极作用的关键。     

血管内皮细胞在生物材料引起血栓形成过程中的作用

血管内皮细胞——这一铺展于血管内腔、包绕着循环血的细胞,可合成和释放多种活性物质调节血液的凝血与抗凝平衡,在生物材料引起血栓形成的过程中起着重要的作用。同时它促栓和抗栓功能的异常改变也是衡量生物材料血液相容性优劣的灵敏指标。本文就近年来对内皮细胞对凝血—抗凝系统的调节及其在生物材料引起血栓形成中的作用等方面的研究以及尚待解决的一些问题作一综述。     

补阳还五汤促进内皮祖细胞修复损伤血管内皮

目的:探讨补阳还五汤(BYHWD)促进内皮祖细胞(EPCs)修复损伤血管内皮的作用及相关机制。方法:以补阳还五汤灌胃及EPCs尾静脉输注作用于内皮损伤的模型大鼠,从血管内皮的形态、功能和EPCs归巢等方面评价内皮损伤修复情况;从血管内环境改善和基质细胞衍生因子-1(SDF-1)及其受体趋化因子受体-4相关蛋白表达了解该方促进EPCs修复受损血管的机制。结果:与单用EPCs组和单用BYHWD组比较,BYHWD联合EPCs组内膜厚度明显减少,甘油三酯、总胆固醇及血钙含量降低,高密度脂蛋白含量升高;此外,BYHWD联合EPCs组血管内皮型一氧化氮合酶(e NOS)及血管SDF-1蛋白表达均显著增加。结论:补阳还五汤能促进EPCs修复损伤的血管内皮,其作用机制可能与调控内环境以及促进EPCs的归巢有关。     

Microtubule-actin interactions may regulate endothelial integrity and repair.

An important mechanism for the initiation and progression of atherosclerosis is the loss of endothelial integrity, which is required for normal blood vessel function. The important components of the endothelial cell cytoskeleton system that regulate endothelial integrity include actin microfilaments and microtubules, which are both associated with protein complexes that regulate cell-cell and cell-substratum adhesion. To date, studies have shown that microfilaments are essential in maintaining the structural integrity of the endothelium while microtubules regulate the directional cell migration during repair. When microtubules are disrupted at the onset of wounding, neither centrosome reorientation, which is essential for efficient endothelial cell wound repair, nor cell migration occurs. Disruption of microfilaments is also associated with inefficient endothelial cell migration and repair. How then might these systems be associated with one another? Linker proteins, which may facilitate interaction between microtubules and actin microfilaments, have recently been identified in nonendothelial systems. It is likely that microtubule-microfilament interactions are important in the complex regulation of endothelial integrity and repair especially as they relate to atherosclerotic plaque formation.     

The role of fucosylation in the promotion of endothelial progenitor cells in neovascularization and bone repair

Bone marrow-derived endothelial progenitor cells (EPCs) are being tested as a therapy to treat a variety of ischemic diseases. Poor homing to targeted tissues is one of the major factors limiting the therapeutic efficacy of EPCs. Here, we show that human cord blood-derived EPCs expressed little sialyl Lewis X (sLe^x) antigen that is necessary for selectin-mediated cell–cell interactions. Expression of α1,3-fucosyltransferase VI (FucT VI) in the EPCs enhanced sLe^x synthesis, E- and P-selectin-binding, and EPC adhesion to tumor necrosis factor-α-stimulated human umbilical vein endothelial cells in culture. In a mouse model of hind limb ischemia, in which EPCs were injected intravenously, FucT VI expression increased EPC homing, neovascularization, and blood flow in ischemic muscles. In another mouse model of femoral fracture, FucT VI-expressing EPCs were more efficient than control EPCs in targeting to peri-fracture tissues to enhance angiogenesis, blood flow and bone repair. These results indicate that fucosylated EPCs may be used to as an improved cellular source to treat ischemic diseases.     

The role of plasma factors in the adherence of leucocytes to vascular endothelial cells

Studies have been undertaken to search for humoral factors present in the plasma from animals undergoing inflammation which may promote specific cell types to adhere to vascular endothelium. We have tested both plasma from animals with “acute” pleural inflammation and animals with “chronic” carrageenan air pouch granulomata for the presence of leucocyte pro-adhesive activity. Plasma from animals with carrageenan pleurisy had augmented polymorph adhesive activity. This activity was absent in the plasma from animals with air pouch granulomata. No such pro-adhesive activity for mononuclear cells was detected in this plasma. We conclude that the initial influx of polymorphs during the early stages of inflammation may in part be due to systemic pro-adhesive factors. It is proposed that these factors in combination with chemotaxins released at the lesion site are responsible for the early dominance of polymorphs.     

Interactions of T lymphocytes with human vascular endothelial cells: role of endothelial cells surface antigens

We have studied the interactions of peripheral blood T lymphocytes with cultured human vascular endothelial cells, focusing upon endothelial cell surface antigens important for T cell recognition. Under standard culture conditions endothelial cells express class I but not class II major histocompatibility complex (MHC) antigens. However, class II antigens may be induced by activated T cells or T cell products, including the lymphokine immune interferon. Immune interferon concomitantly increases class I antigen expression and causes a change in cell shape. In addition to vascular endothelial cells, we have found that vascular smooth muscle cells and human dermal fibroblasts may also be induced by immune interferon to express class II antigens. All known human class II antigens are induced (i.e. HLA-DR, DC and SB) as is the associated invariant chain. Induced antigen expression in these cells is stable over several days, although mRNA levels decline rapidly upon withdrawal of interferon. Vascular and stromal cell class II antigens are functional, in that they can be recognized by cytolytic and helper T cell clones. Several non-MHC antigens are also involved in the recognition of endothelial and stromal cells by T cells. We propose a model for the role of inducible class II molecules on endothelium and stromal cells in vivo: The induction of class II MHC antigens on endothelial cells, locally mediated by activated T cells, enables endothelium to present an immunogenic cell surface structure, comprised of antigen plus self class II polymorphic determinants, which in turn, serves to recruit additional antigen-specific T cells from the circulation into the site of a developing cell mediated immune response. Class II molecules on stromal cells, also induced locally at the site of a developing response, confers immune accessory function on these cells and may serve to augment and sustain a T cell response.     

The role of endothelial cells in allograft rejection

Endothelial cells (EC) are crucially involved in allograft rejection. They are prime targets of alloreactivity but also key players in the recruitment and extravasation of immune cells. These mechanisms also become clear in allograft biopsies with antibody-mediated complement deposition on EC and associated intracapillary accumulation of immune cells. HLA molecules are the most prominent targets of alloantibodies in AB0 compatible transplantation. Clinically relevant antibodies against other antigens such as MICA (MHC class I-related chain A) or the angiotensin II Type-1 receptor could also be convincingly demonstrated. The lack of generally available diagnostic tests for such non-HLA antibodies hampers their introduction into clinical practice. Alloantibodies undoubtedly cause allograft rejection. However, our knowledge of the molecular mechanisms underlying graft dysfunction in antibody-mediated rejection (AMR) is still fragmentary. Activation of EC by anti-endothelial cell antibodies was demonstrated in several experimental systems. Recent animal studies employing immune cell deficient transplant recipients or in-vitro assays, however, failed to demonstrate an immediate response of EC upon antibody binding and complement activation. It might therefore be considered that direct antibody- or complement-mediated EC damage is not necessarily the leading event in acute AMR. Antibody- and/or complement-induced recruitment of immune cells might rather be of crucial importance at least in the early phases of AMR.     

The role of endothelial cell reactive antibodies in peripheral vascular disease

The mechanism by which a small but significant proportion of patients with peripheral vascular disease (PVD) rapidly progress to critical ischaemia is unclear. Both experimental and clinical data suggest a role for autoantibodies in the pathogenesis of atherosclerotic disease, particularly in the accelerated atherosclerosis seen in patients with systemic lupus erythematosus and the anti-phospholipid syndrome. This review examines the evidence for a role for endothelial cell reactive autoantibodies in PVD and the potential mechanisms by which these autoantibodies could contribute to the acceleration of atherosclerosis in a proportion of patients. The identification of such markers could lead to the identification of patients with PVD who are at risk of developing critical ischaemia and may warrant early and aggressive intervention.     

Nitric oxide attenuates vascular endothelial cadherin‐mediated vascular integrity in human chronic inflammation

In this study, we examined the role of nitric oxide (NO) in controlling vascular integrity mediated by vascular endothelial (VE)‐cadherin in chronic inflammation. Periapical granulomas were analysed for the expression of inducible NO synthase (iNOS) and VE‐cadherin, and more iNOS expression than VE‐cadherin was shown. Human umbilical vein endothelial cells (HUVECs) were stimulated with proinflammatory cytokines and lipopolysaccharide extracted from Porphyromonas gingivalis and it induced iNOS expression, whereas it reduced VE‐cadherin expression, compared with negative controls. On the other hand, pre‐incubation with 1400W, an iNOS‐specific inhibitor, markedly reduced iNOS expression in stimulated HUVECs and restored VE‐cadherin expression to its control level, suggesting that vascular integrity was modulated in conjunction with the reduction of NO. Immunocytochemistry confirmed the functional role of NO in cultured HUVEC monolayers with or without 1400W. These data are consistent with a hypothesis suggesting that NO could attenuate VE‐cadherin‐mediated vascular integrity in human chronic inflammation.     

The role of vascular endothelial growth factor in the tissue specific in vivo growth of prostate cancer cells

Despite the fact that cancer cells can be found in many vascular beds, continued growth of the metastatic tumor focus exhibits a significant degree of 'organ tropism', with only certain organs exhibiting the ravages of metastatic disease. Since a limiting factor to the growth of metastases beyond 2 mm in diameter, may be a lack of angiogenesis, we sought to determine whether tumor overexpression of vascular endothelial growth factor (VEGF), a potent angiogenic factor related to prostate cancer metastasis, is causally related to organ specific tumor growth in a prostate cancer xenograft model. LnCaP-C4-2 is a subline of the human prostate cancer cell line LnCaP which unlike its parent, has a predilection for growth in bone, a common site for human prostate cancer metastasis. LnCaP-C4-2, is tumorigenic when injected intrafemorally in mice but requires co-injection of stromal components (Matrigel) to be tumorigenic in the subcutaneous site. Because of this site-specific tumorigenicity profile and relatively low VEGF mRNA and protein expression, this line was transfected with a full length cDNA encoding the 165 isoform of VEGF. Cells either overexpressing or not expressing the transfected gene were selected for study in vivo and in vitro. Overexpression of VEGF did not seem to affect in vitro cell growth. Such overexpression did affect tumorigenicity and in vivo tumor growth rates when cells were inoculated in the subcutaneus site. Interestingly, the dependency of subcutaneous tumorigenicity on Matrigel co-inoculation was still observed in cells overexpressing VEGF. In contrast to the impact that VEGF overexpression has on subcutaneous tumorigenicity, no such effect was observed when cells were inoculated in orthotopic/prostate (primary) or intrafemoral (metastatic) sites. In view of the importance of tumor-stromal interactions in growth of xenografts, we sought to determine if the host strain is important to the observed tumorigenicity effects of VEGF overexpression. No differences in subcutaneous tumorigenicity as a function of either Matrigel use or VEGF expression levels were observed when SCID/bg and RAG/pfp mouse strains were compared. In conclusion, our data indicate that the biological impact of prostate tumor VEGF overexpression is organ/site specific, leading to the speculation that it may play a part in the observed organ tropism of metastatic spread. In addition, these results highlight the importance of the tumor microenvironment in determining the biological impact of transfected and overexpressed genes in the study of tumor biology.     

血管内皮祖细胞与缺血性心血管病的血管新生

1997年Ｔａｋａｙｕｋｉ等[1] 在Ｓｃｉｅｎｃｅ杂志发表论文报道血管内皮祖细胞 (ｅｎｄｏｔｈｅｌｉａｌｐｒｏｇｅｎｉｔｏｒｃｅｌｌｓ ,ＥＰＣ)分离成功 ,并可用于体内血管新生 (ａｎｇｉｏｇｅｎｅｓｉｓ)。当时提出的血管内皮祖细胞认为是假定的 (ｐｕｔａｔｉｖｅ)。但是 ,近年来随着干细胞研究的深入 ,血管内皮祖细胞的存在基本已经确认 ,而且它与血管新生间的关系日益受到重视[2 ,3 ] 。本文将讨论血管内皮祖细胞的特征 ,它与缺血性心血管疾病中血管新生的关系及其可能的应用前景。1　血管内皮祖细胞的特征　　血管内皮祖细胞是血…     

Uraemic serum induces dysfunction of vascular endothelial cells: role of ubiquitin-proteasome pathway

The ubiquitin-proteasome pathway (UPP) has been indicated to contribute to dysfunction of endothelial cells (ECs). Nevertheless, the relationship between UPP and vascular complications of uraemia remains unknown. We aimed to determine whether the UPP is activated in vascular ECs when cultured with uraemic serum, and to examine the role of the UPP on dysfunction of ECs in uraemia. Rabbit aortic endothelial cells (RAECs) were cultured with normal serum or different concentrations of uraemic serum. The expression of the ubiquitin-activating enzyme (E1), an indicator of the UPP, was detected by real-time RT-PCR and Western blot; proteasome activity was determined by fluorescence spectrophotometry; and nuclear factor-κB (NF-κB) activity and expression, as well as tumour necrosis factor-α (TNF-α) expression, were also detected. We found that the expression of E1 and the activities of three kinds of proteasomes were increased significantly in RAECs after incubation with uraemic serum. Proliferation of RAECs was increased significantly by incubation with 3-15% uraemic serum but decreased markedly when incubated with uraemic serum above 15% (increased apoptosis). Incubation of RAECs with uraemic serum induced increased NF-B DNA-binding activity and nuclear translocation of NF-κB, decreased nitric oxide production and increased expression of TNF-α, which is the final effector of inflammatory activation of cells. All of these responses in RAECs were suppressed by the specific proteasome inhibitor, MG132. The inhibition of inflammatory responses by MG132 was further supported by a parallel experiment with pyrrolidine dithiocarbamate, a specific inhibitor of κNF-B. These findings suggest that the UPP was activated in RAECs by administration of uraemic serum, and played a pivotal role in the dysfunction of vascular ECs, such as inflammatory activation.     

血管内皮生长因子与促血管生成素1对大鼠血管内皮细胞的作用

背景：血管内皮生长因子、促血管生成素1是血管形成过程中始动并且使之持续的重要因子,研究其对血管内皮细胞的作用具有重要的意义。 目的：观察血管内皮生长因子与促血管生成素1对培养血管内皮细胞迁移与增殖能力的影响,并探讨其在血管生成方面的作用机制。 方法：在大鼠脐静脉内皮细胞内单独或联合加入血管内皮生长因子、促血管生成素1后,划痕实验和MTT检测对细胞迁移与增殖的影响,观察内皮细胞形态、活性、迁移能力。 结果与结论：划痕实验显示单独血管内皮生长因子作用时,与空白对照组细胞迁移无明显差异,单独促血管生成素1作用时,不仅不能增加细胞的迁移作用,反较空白对照组有所减弱,当血管内皮生长因子与促血管生成素1联合作用时,细胞迁移较空白对照组明显增强;MTT实验结果表明：单纯加入血管内皮生长因子或促血管生成素1,均不能起到有效促进内皮细胞增殖的作用;联合应用血管内皮生长因子及促血管生成素1可有效促进增殖。结果可见当血管内皮生长因子与促血管生成素1联合应用时,才能有效促内皮细胞迁移与增殖,发挥促血管生成作用。     

microRNA-133b在低切应力诱导血管内皮细胞影响血管平滑肌细胞增殖中的作用

目的研究血管内皮细胞(endothelial cells,ECs)直接感受低切应力刺激后分泌类胰岛素生长因子-1(insulinlike growth factor-1,IGF-1)影响血管平滑肌细胞(vascular smooth muscle cells,VSMCs)增殖这一过程中microRNAs(miRs)的作用。方法用平行平板流动腔系统对ECs施加1.5 Pa正常切应力(normal shear stress,NSS)和0.5 Pa低切应力(low shear stress,Low SS),Real-time PCR检测VSMCs的miRs变化。用miRs预测网站预测miR-133b靶基因并验证。Western blotting检测核糖核酸结合蛋白1(polypyrimidine tract binding protein 1,Ptbp1)和N-myc下游调节基因1(N-myc downstream regulated 1,Ndrg1)的蛋白水平变化。Ed U流式检测miR-133b对VSMCs增殖的影响。结果 IGF-1静态刺激后,VSMCs的miR-133b和miR-378a表达上升。Low SS条件下,VSMCs的miR-133b表达显著上升,miR-378a表达无明显变化。下调VSMCs的miR-133b表达,Ptbp1、Ndrg1的mRNA水平均显著升高,上调VSMCs的miR-133b的表达,Ptbp1、Ndrg1的mRNA和蛋白水平显著降低,并且显著促进VSMCs增殖。结论在Low SS条件下ECs分泌IGF-1可能通过调控联合培养VSMCs的miR-133b和靶基因Ptbp1和Ndrg1促进VSMCs增殖。研究结果为心血管疾病治疗提供了一个新的潜在靶标。