Stimulation of PAI-1 expression in endothelial cells by cultured vascular smooth muscle cells

Transcriptional drifts associated with environmental changes in endothelial cells

Environmental cues, such as physical forces and heterotypic cell interactions play a critical role in cell function, yet their collective contributions to transcriptional changes are unclear. Focusing on human endothelial cells, we performed broad individual sample analysis to identify transcriptional drifts associated with environmental changes that were independent of genetic background. Global gene expression profiling by RNA sequencing and protein expression by liquid chromatography-mass spectrometry directed proteomics distinguished endothelial cells in vivo from genetically matched culture (in vitro) samples. Over 43% of the transcriptome was significantly changed by the in vitro environment. Subjecting cultured cells to long-term shear stress significantly rescued the expression of approximately 17% of genes. Inclusion of heterotypic interactions by co-culture of endothelial cells with smooth muscle cells normalized approximately 9% of the original in vivo signature. We also identified novel flow dependent genes, as well as genes that necessitate heterotypic cell interactions to mimic the in vivo transcriptome. Our findings highlight specific genes and pathways that rely on contextual information for adequate expression from those that are agnostic of such environmental cues.

Endothelial heterogeneity in the umbilico-placental unit: DNA methylation as an innuendo of epigenetic diversity

The endothelium is a multifunctional heterogeneous tissue playing a key role in the physiology of every organ. To accomplish this role the endothelium presents a phenotypic diversity that is early prompted during vascular development, allowing it to cope with specific requirements in a time- and site-specific manner. During the last decade several reports show that endothelial diversity is also present in the umbilico-placental vasculature, with differences between macro- and microvascular vessels as well as arterial and venous endothelium. This diversity is evidenced in vitro as a higher angiogenic capacity in the microcirculation; or disparity in the levels of several molecules that control endothelial function (i.e., receptor for growth factors, vasoactive mediators, and adhesion molecules) which frequently are differentially expressed between arterial and venous endothelium. Emerging evidence suggests that endothelial diversity would be prominently driven by epigenetic mechanisms which also control the basal expression of endothelial-specific genes. This review outlines evidence for endothelial diversity since early stages of vascular development and how this heterogeneity is expressed in the umbilico-placental vasculature. Furthermore a brief picture of epigenetic mechanisms and their role on endothelial physiology emphasizing new data on umbilical and placental endothelial cells is presented. Unraveling the role of epigenetic mechanisms on long term endothelial physiology and its functional diversity would contribute to develop more accurate therapeutic interventions. Altogether these data show that micro- versus macro-vascular, or artery versus vein comparisons are an oversimplification of the complexity occurring in the endothelium at different levels, and the necessity for the future research to establish the precise source of cells which are under study.

Effects of plasminogen activator inhibitor-1-specific RNA aptamers on cell adhesion, motility, and tube formation

The serine protease inhibitor (serpin) plasminogen activator inhibitor-1 (PAI-1) is associated with the pathophysiology of several diseases, including cancer and cardiovascular disease. The extracellular matrix protein vitronectin increases at sites of vessel injury and is also present in fibrin clots. Integrins present on the cell surface bind to vitronectin and anchor the cell to the extracellular matrix. However, the binding of PAI-1 to vitronectin prevents this interaction, thereby decreasing both cell adhesion and migration. We previously developed PAI-1-specific RNA aptamers that bind to (or in the vicinity of) the vitronectin binding site of PAI-1. These aptamers prevented cancer cells from detaching from vitronectin in the presence of PAI-1, resulting in an increase in cell adhesion. In the current study, we used in vitro assays to investigate the effects that these aptamers have on human aortic smooth muscle cell (HASMC) and human umbilical vein endothelial cell (HUVEC) migration, adhesion, and proliferation. The PAI-1-specific aptamers (SM20 and WT15) increased attachment of HASMCs and HUVECs to vitronectin in the presence of PAI-1 in a dose-dependent manner. Whereas PAI-1 significantly inhibited cell migration through its interaction with vitronectin, both SM20 and WT15 restored cell migration. The PAI-1 vitronectin binding mutant (PAI-1AK) did not facilitate cell detachment or have an effect on cell migration. The effect on cell proliferation was minimal. Additionally, both SM20 and WT15 promoted tube formation on matrigel that was supplemented with vitronectin, thereby reversing the PAI-1's inhibition of tube formation. Collectively, results from this study show that SM20 and WT15 bind to the PAI-1's vitronectin binding site and interfere with its effect on cell migration, adhesion, and tube formation. By promoting smooth muscle and endothelial cell migration, these aptamers can potentially eliminate the adverse effects of elevated PAI-1 levels in the pathogenesis of vascular disease.

Systemic versus localized coagulation activation contributing to organ failure in critically ill patients

In the pathogenesis of sepsis, inflammation and coagulation play a pivotal role. Increasing evidence points to an extensive cross-talk between these two systems, whereby inflammation not only leads to activation of coagulation but coagulation also considerably affects inflammatory activity. The intricate relationship between inflammation and coagulation may not only be relevant for vascular atherothrombotic disease in general but has in certain clinical settings considerable consequences, for example in the pathogenesis of microvascular failure and subsequent multiple organ failure, as a result of severe infection and the associated systemic inflammatory response. Molecular pathways that contribute to inflammation-induced activation of coagulation have been precisely identified. Pro-inflammatory cytokines and other mediators are capable of activating the coagulation system and downregulating important physiological anticoagulant pathways. Activation of the coagulation system and ensuing thrombin generation is dependent on an interleukin-6-induced expression of tissue factor on activated mononuclear cells and endothelial cells and is insufficiently counteracted by physiological anticoagulant mechanisms and endogenous fibrinolysis. Interestingly, apart from the overall systemic responses, a differential local response in various vascular beds related to specific organs may occur.

Oncostatin M-enhanced vascular endothelial growth factor expression in human vascular smooth muscle cells involves PI3K-, p38 MAPK-, Erk1/2- and STAT1/STAT3-dependent pathways and is attenuated by interferon-γ

The pleiotropic cytokine oncostatin M (OSM), a member of the glycoprotein (gp)130 ligand family, plays a key role in inflammation and cardiovascular disease. As inflammation precedes and accompanies pathological angiogenesis, we investigated the effect of OSM and other gp130 ligands on vascular endothelial growth factor (VEGF) production in human vascular smooth muscle cells (SMC). Human coronary artery SMC (HCASMC) and human aortic SMC (HASMC) were treated with different gp130 ligands. VEGF protein was determined by ELISA. Specific mRNA was detected by RT-PCR. Western blotting was performed for signal transducers and activators of transcription1 (STAT1), STAT3, Akt and p38 mitogen-activated protein kinase (p38 MAPK). OSM mRNA and VEGF mRNA expression was analyzed in human carotid endaterectomy specimens from 15 patients. OSM increased VEGF production in both HCASMC and HASMC derived from different donors. OSM upregulated VEGF and OSM receptor-specific mRNA in these cells. STAT3 inhibitor WP1066, p38 MAPK inhibitors SB-202190 and BIRB 0796, extracellular signal-regulated kinase1/2 (Erk1/2) inhibitor U0126, and phosphatidylinositol 3-kinase (PI3K) inhibitors LY-294002 and PI-103 reduced OSM-induced VEGF synthesis. We found OSM expression in human atherosclerotic lesions where OSM mRNA correlated with VEGF mRNA expression. Interferon-γ (IFN-γ), but not IL-4 or IL-10, reduced OSM-induced VEGF production in vascular SMC. Our findings that OSM, which is present in human atherosclerotic lesions and correlates with VEGF expression, stimulates production of VEGF by human coronary artery and aortic SMC indicate that OSM could contribute to plaque angiogenesis and destabilization. IFN-γ reduced OSM-induced VEGF production by vascular SMC.

Drug packaging and delivery using perfluorocarbon nanoparticles for targeted inhibition of vascular smooth muscle cells

AIM

To investigate the in vitro release profile of drugs encapsulated within perfluorocarbon (PFC) nanoparticles (NPs) and their ability to inhibit the activity of vascular smooth muscle cells (SMCs).

METHODS

Dexamethasone phosphate (DxP) or dexamethasone acetate (DxA) was encapsulated into PFC nanoparticles using a high-pressure homogenous method. The morphology and size of the NPs were examined using scanning electron microscopy (SEM) and a laser particle size analyzer. Drug loading and in vitro release were assessed by high-performance liquid chromatography (HPLC). The impact of NP capsules on SMC proliferation, migration and apoptosis in vitro was assessed using cell counting kit-8, transwell cell migration and flow cytometry assays.

RESULTS

The sizes of DxP-NPs and DxA-NPs were 224+/-6 nm and 236+/-9 nm, respectively. The encapsulation efficiency (EE) of DxP-NPs was 66.4%+/-1.0%, with an initial release rate of 77.2%, whereas the EE of DxA-NPs was 95.3%+/-1.3%, with an initial release rate of 23.6%. Both of the NP-coated drugs could be released over 7 d. Human umbilical artery SMCs were harvested and cultured for four to six passages. Compared to free DxP, SMCs treated with tissue factor (TF)-directed DxP-NPs showed significant differences in the inhibition of proliferation, migration and apoptosis (P<0.05).

CONCLUSION

The results collectively suggest that PFC nanoparticles will be beneficial for targeted drug delivery because of the sustained drug release and effective inhibition of SMC proliferation and migration.

Expression of Fibrinolytic and Coagulation Factors in Cocultured Human Endothelial and Smooth Muscle Cells

Interactions between endothelial cells and smooth muscle cells are interesting from a tissue-engineering point of view. We have developed a coculture system that allows direct contact between these two cell types. The fibrinolytic factors PAI-1, tPA, and uPA and the coagulation factor TF, were studied at the gene level by RT-PCR and at the protein level by ELISA. Significant changes of all studied factors were seen at the gene level in cocultured endothelial cells. tPA and TF were upregulated 4- and 7-fold, respectively, and PAI-1 and uPA were downregulated 4- and 1.5-fold, respectively, compared with single-cultured controls. In cocultured smooth muscle cells alterations of PAI-1 and TF were significant, with a 1.5-fold upregulation of PAI-1 and a 2.5-fold downregulation of TF. Results at the protein level mirrored the gene expression results. These findings indicate that cocultured endothelial cells are rendered both hypercoagulative and hyperfibrinolytic.

Ability of various inserts to promote endothelium cell culture for the establishment of coculture models

To select an insert suitable for human umbilical vein endothelial cell (HUVEC) culture, we compared several available inserts of 0.2 to 0.45 micron porosity: Cellagen (ICN), Transwell-COL (Costar), Millicell-HA and CM (Millipore), Anopore (Nunc), Cyclopore (Falcon) in comparison with a control surface (Thermanox). The requirements were: (i) to promote attachment, adhesion and proliferation of HUVEC (judged by [3H]thymidine incorporation into DNA at days 1, 3, 7); (ii) to allow HUVEC visualization by inverted, fluorescence microscopy for uptake of DiI-Ac-LDL and scanning electron microscopy, performed at day 9 after seeding. Because Transwell and Cellagen are collagen precoated and CM has to be coated for cell culture, we performed collagen coating (types I + III or IV) for non-pretreated inserts for the purpose of comparison. Our preferences comprise Transwell-COL, Cyclopore not coated or coated (whatever the collagen type), and Cellagen. However, on a quality/price ratio criterion, Cyclopore, even uncoated, is the insert of choice. The HA, CM and Anopore inserts, even coated, do not allow HUVEC growth but do not alter positive uptake of acetylated LDL.

Fibrinolysis and atherosclerosis

The link between impaired fibrinolytic function and CHD has been reinforced considerably in the past couple of years. This has been achieved by a combination of epidemiological, clinical, cell biological and molecular biological studies. The molecular mechanisms for the identified associations between more established risk factors for atherosclerotic disease and impaired fibrinolytic function now need to be disentangled to promote the design of specific drugs that may pave the way for intervention. The possibility that some of the observed relations are epiphenomena should also not be disregarded. The concept of genotype-specific differences in the susceptibility of the individual to common metabolic disturbances needs to be examined in greater detail. Basic research on the role of fibrinolysis in atherosclerosis and its thrombotic complications should be given high priority, because the modulation of fibrinolytic function is likely to become an important approach to prevention.