Transfection of human endothelial cells

STING inhibition enables efficient plasmid-based gene expression in primary vascular cells: A simple and cost-effective transfection protocol

Plasmid transfection in cells is widely employed to express exogenous proteins, offering valuable mechanistic insight into their function(s). However, plasmid transfection efficiency in primary vascular endothelial cells (ECs) and smooth muscle cells (SMCs) is restricted with lipid-based transfection reagents such as Lipofectamine. The STING pathway, activated by foreign DNA in the cytosol, prevents foreign gene expression and induces DNA degradation. To address this, we explored the potential of STING inhibitors on the impact of plasmid expression in primary ECs and SMCs. Primary human aortic endothelial cells (HAECs) were transfected with a bicistronic plasmid expressing cytochrome b5 reductase 4 (CYB5R4) and enhanced green fluorescent protein (EGFP) using Lipofectamine 3000. Two STING inhibitors, MRT67307 and BX795, were added during transfection and overnight post-transfection. As a result, MRT67307 significantly enhanced CYB5R4 and EGFP expression, even 24 hours after its removal. In comparison, MRT67307 pretreatment did not affect transfection, suggesting the inhibitor's effect was readily reversible. The phosphorylation of endothelial nitric oxide synthase (eNOS) at Serine 1177 (S1177) by vascular endothelial growth factor is essential for endothelial proliferation, migration, and survival. Using the same protocol, we transfected wild-type and phosphorylation-incapable mutant (S1177A) eNOS in HAECs. Both forms of eNOS localized on the plasma membrane, but only the wild-type eNOS was phosphorylated by vascular endothelial growth factor treatment, indicating normal functionality of overexpressed proteins. MRT67307 and BX795 also improved plasmid expression in human and rat aortic SMCs. In conclusion, this study presents a modification enabling efficient plasmid transfection in primary vascular ECs and SMCs, offering a favorable approach to studying protein function(s) in these cell types, with potential implications for other primary cell types that are challenging to transfect.

Microvesicles transfer mitochondria and increase mitochondrial function in brain endothelial cells

We have demonstrated, for the first time that microvesicles, a sub-type of extracellular vesicles (EVs) derived from hCMEC/D3: a human brain endothelial cell (BEC) line transfer polarized mitochondria to recipient BECs in culture and to neurons in mice acute brain cortical and hippocampal slices. This mitochondrial transfer increased ATP levels by 100 to 200-fold (relative to untreated cells) in the recipient BECs exposed to oxygen-glucose deprivation, an in vitro model of cerebral ischemia. We have also demonstrated that transfer of microvesicles, the larger EV fraction, but not exosomes resulted in increased mitochondrial function in hypoxic endothelial cultures. Gene ontology and pathway enrichment analysis of EVs revealed a very high association to glycolysis-related processes. In comparison to heterotypic macrophage-derived EVs, BEC-derived EVs demonstrated a greater selectivity to transfer mitochondria and increase endothelial cell survival under ischemic conditions.

Promoter Assay Using Luciferase Reporter Gene in the A549 Cell Line

The development of reporters systems has simplified the study of promoter activity in different areas of knowledge, and represents an easy and fast approach to study genetic variations. In this chapter, we show a transfection protocol of A549 lung epithelial cells with a reporter vector, using the Luciferase-Renilla dual system for studying the variations caused by several polymorphisms in the promoter region of a gene.

Targeting REDV peptide functionalized polycationic gene carrier for enhancing the transfection and migration capability of human endothelial cells

Targeting gene engineering should be considered as an effective method for promoting endothelialization of vascular grafts. Herein, we developed a targeting REDV peptide functionalized polycationic gene carrier for carrying the pEGFP-ZNF580 plasmid with the aim of enhancing the transfection and migration capability of human endothelial cells. This polycationic gene carrier with the REDV peptide (mPEG-P(LA-co-CL)-PEI-REDV) was prepared by the conjugation of the Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide with the amphiphilic block copolymer methoxy poly(ethylene glycol) ether-poly(l-lactide-co-ε-caprolactone)-poly(ethyleneimine) (mPEG-P(LA-co-CL)-PEI). mPEG-P(LA-co-CL)-PEI nanoparticles (NP) and mPEG-P(LA-co-CL)-PEI-REDV nanoparticles (REDV-NP) were formed by the self-assembly of the corresponding polycationic polymers, and then their pEGFP-ZNF580 complexes were prepared via the electrostatic interaction with pEGFP-ZNF580 plasmids, respectively. Gel electrophoresis results show that the targeted REDV-NPs could compress pEGFP-ZNF580 plasmids into stable complexes and protect the plasmids against desoxyribonuclease degradation. MTT assay indicates that these targeted REDV-NP/pEGFP-ZNF580 complexes exhibit better cyto-compatibility than the non-targeted NP/pEGFP-ZNF580 complexes and the control PEI 1800 Da/pEGFP-ZNF580 complexes. In vitro transfection experiments and western blot analysis of EA.hy926 endothelial cells show that the pEGFP-ZNF580 plasmid expression and the relative protein level transfected by targeted REDV-NP/pEGFP-ZNF580 complexes are roughly consistent with that transfected by PEI 25 kDa/pEGFP-ZNF580 complexes. More importantly, the scratch wound assay results demonstrate that the migration capability of EA.hy926 cells has been improved significantly by the expression of the pEGFP-ZNF580 plasmid. Our results indicate that the polycationic polymer with functional REDV peptides can be a potential candidate as a pEGFP-ZNF580 plasmid delivery carrier and may be used in the endothelialization of vascular grafts.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.

Enhanced bone morphogenic protein adenoviral gene delivery to bone marrow stromal cells using magnetic nanoparticle

Objectives

This study investigated the question of whether adenoviral magnetofection can be a suitable method for increasing the efficacy of gene delivery into bone marrow stromal cell (BMSC) and for generation of a high level of bone morphogenic protein (BMP) secretion at a minimized viral titer.

Materials and Methods

Primary BMSCs were isolated from C57BL6 mice and transduced with adenoviral vectors encoding β galactosidase or BMP2 and BMP7. The level of BMP secretion, activity of osteoblast differentiation, and cell viability of magnetofection were measured and compared with those of the control group.

Results

The expression level of β galactosidase showed that the cell transduction efficiency of AdLacZ increased according to the increased amount of magnetic nanoparticles. No change in cell viability was observed after magnetofection with 2 µL of magnetic nanoparticle. Secretion of BMP2 or BMP7 was accelerated after transduction of AdBMP2 and 7 with magnetofection. AdBMP2 adenoviral magnetofection resulted in up to 7.2-fold higher secretion of BMP2, compared with conventional AdBMP2-transduced BMSCs. Magnetofection also induced a dramatic increase in secretion of BMP7 by up to 10-fold compared to the control. Use of only 1 multiplicity of infection (moi) of magnetofection with adenoviral transduction of AdBMP2 or AdBMP7 resulted in significantly higher transgene expression compared to 20 moi of conventional adenoviral transduction.

Conclusion

Magnetic particle-mediated gene transudation is a highly efficient method of gene delivery to BMSCs. Magnetofection can lower the amount of viral particles while improving the efficacy of gene delivery.

Efficient nanoparticle mediated sustained RNA interference in human primary endothelial cells

Endothelium forms an important target for drug and/or gene therapy since endothelial cells play critical roles in angiogenesis and vascular functions and are associated with various pathophysiological conditions. RNA mediated gene silencing presents a new therapeutic approach to overcome many such diseases, but the major challenge of such an approach is to ensure minimal toxicity and effective transfection efficiency of short hairpin RNA (shRNA) to primary endothelial cells. In the present study, we formulated shAnnexin A2 loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles which produced intracellular small interfering RNA (siRNA) against Annexin A2 and brought about the downregulation of Annexin A2. The per cent encapsulation of the plasmid within the nanoparticle was found to be 57.65%. We compared our nanoparticle based transfections with Lipofectamine mediated transfection, and our studies show that nanoparticle based transfection efficiency is very high (~97%) and is more sustained compared to conventional Lipofectamine mediated transfections in primary retinal microvascular endothelial cells and human cancer cell lines. Our findings also show that the shAnnexin A2 loaded PLGA nanoparticles had minimal toxicity with almost 95% of cells being viable 24 h post-transfection while Lipofectamine based transfections resulted in only 30% viable cells. Therefore, PLGA nanoparticle based transfection may be used for efficient siRNA transfection to human primary endothelial and cancer cells. This may serve as a potential adjuvant treatment option for diseases such as diabetic retinopathy, retinopathy of prematurity and age related macular degeneration besides various cancers.

Viscolin reduces VCAM-1 expression in TNF-α-treated endothelial cells via the JNK/NF-κB and ROS pathway

Viscolin, a major active component in a chloroform extract of Viscum coloratum, has antioxidative and anti-inflammatory properties. We focused on its effects on the expression of vascular cell adhesion molecule-1 (VCAM-1) in tumor necrosis factor-α (TNF-α)-treated human umbilical vein endothelial cells (HUVECs). The TNF-α-induced expression of VCAM-1 was significantly reduced by respectively 38±7 or 34±16% when HUVECs were pretreated with 10 or 30μM viscolin, as shown by Western blotting, and was also significantly reduced by pretreatment with the antioxidants N-acetylcysteine, diphenylene iodonium chloride, and apocynin. Viscolin also reduced TNF-α-induced VCAM-1 mRNA expression and promoter activity, decreased reactive oxygen species (ROS) production, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and significantly reduced the binding of monocytes to TNF-α-stimulated HUVECs. The attenuation of TNF-α-induced VCAM-1 expression and cell adhesion was partly mediated by a decrease in JNK phosphorylation. Furthermore, viscolin reduced VCAM-1 expression in the aorta of TNF-α-treated mice in vivo. Taken together, these data show that viscolin inhibits TNF-α-induced JNK phosphorylation, nuclear translocation of NF-κB p65, and ROS generation and thereby suppresses VCAM-1 expression, resulting in reduced adhesion of leukocytes. These results also suggest that viscolin may prevent the development of atherosclerosis and inflammatory responses.

Lentiviral-mediated overexpression of Bcl-xL protects primary endothelial cells from ischemia/reperfusion injury-induced apoptosis

BACKGROUND

Endothelial cells (EC) respond to mild injurious stimuli by upregulating anti-apoptotic gene expression to maintain endothelial integrity. EC dysfunction and apoptosis resulting from ischemia/reperfusion injury may contribute to chronic allograft rejection. We optimized conditions for lentiviral vector (LVV) transduction of rat aortic endothelial cells (RAEC) and investigated whether LVV delivery of the anti-apoptotic gene, Bcl-xL, protects RAEC from apoptotic death using in vitro models of hypoxia and ischemia/reperfusion injury.

METHODS

LVV containing Bcl-xL were generated from a human immunodeficiency virus (HIV)-1 construct. EC were prepared from rat aorta. Hypoxia/reperfusion (H/R) or ischemia/reperfusion (I/R) injury was induced in vitro and apoptosis was assessed using caspase-3 activity, Annexin V/PI and TUNEL staining.

RESULTS

After in vitro induction of H/R or I/R injury, RAEC showed duration-dependent apoptosis. We confirmed the damaging effect of the reperfusion phase. Endogenous Bax expression increased with I/R injury, whereas endogenous Bcl-xL remained constant. RAEC transduced with LVV expressing Bcl-xL were protected from early apoptosis caused by I/R injury, correlating with reduced cytochrome c release into the cytosol.

CONCLUSIONS

Overexpressing Bcl-xL protects RAEC from I/R injury. This protective effect may be attributed to altering the balance of pro- and anti-apoptotic proteins, resulting in sequestration of the harmful Bax protein, and may open up new strategies for controlling chronic allograft rejection.

Phosphate-buffered saline-based nucleofection of primary endothelial cells

Although various nonviral transfection methods are available, cell toxicity, low transfection efficiency, and high cost remain hurdles for in vitro gene delivery in cultured primary endothelial cells. Recently, unprecedented transfection efficiency for primary endothelial cells has been achieved due to the newly developed nucleofection technology that uses a combination of novel electroporation condition and specific buffer components that stabilize the cells in the electrical field. Despite superior transfection efficiency and cell viability, high cost of the technology has discouraged cardiovascular researchers from liberally adopting this new technology. Here we report that a phosphate-buffered saline (PBS)-based nucleofection method can be used for efficient gene delivery into primary endothelial cells and other types of cells. Comparative analyses of transfection efficiency and cell viability for primary arterial, venous, microvascular, and lymphatic endothelial cells were performed using PBS. Compared with the commercial buffers, PBS can support equally remarkable nucleofection efficiency to both primary and nonprimary cells. Moreover, PBS-mediated nucleofection of small interfering RNA (siRNA) showed more than 90% knockdown of the expression of target genes in primary endothelial cells. We demonstrate that PBS can be an unprecedented economical alternative to the high-cost buffers or nucleofection of various primary and nonprimary cells.

Nanoparticles as nonviral gene delivery vectors

Gene therapy, as therapeutic treatment to genetic or acquired diseases, is attracting much interest in the research community, leading to noteworthy developments over the past two decades. Although this field is still dominated by viral vectors, nonviral vectors have recently received an ever increasing attention in order to overcome the safety problems of their viral counterpart. This review presents the biological aspects involved in the gene delivery process and explores the recent developments and achievements of nonviral gene carriers.

Inactivity of nitric oxide synthase gene in the atherosclerotic human carotid artery

OBJECTIVE

Nitric oxide (NO) inhibits thrombus formation, vascular contraction, and smooth muscle cell proliferation. We investigated whether NO release is enhanced after endothelial NO synthase (eNOS) gene transfer in atherosclerotic human carotid artery ex vivo.

METHODS AND RESULTS

Western blotting and immunohistochemistry revealed that transduction enhanced eNOS expression; however, neither nitrite production nor NO release measured by porphyrinic microsensor was altered. In contrast, transduction enhanced NO production in non-atherosclerotic rat aorta and human internal mammary artery. In transduced carotid artery, calcium-dependent eNOS activity was minimal and did not differ from control conditions. Vascular tetrahydrobiopterin concentrations did not differ between the experimental groups. Treatment of transduced carotid artery with FAD, FMN, NADPH, L-arginine, and either sepiapterin or tetrahydrobiopterin did not alter NO release. Superoxide formation was similar in transduced carotid artery and control. Treatment of transduced carotid artery with superoxide dismutase (SOD), PEG-SOD, PEG-catalase did not affect NO release.

CONCLUSIONS

eNOS transduction in atherosclerotic human carotid artery results in high expression without any measurable activity of the recombinant protein. The defect in the atherosclerotic vessels is neither caused by cofactor deficiency nor enhanced NO breakdown. Since angioplasty is performed in atherosclerotic arteries,eNOS gene therapy is unlikely to provide clinical benefit.

Role of protein phosphatase 2A in the regulation of endothelial cell cytoskeleton structure

Our recently published data suggested the involvement of protein phosphatase 2A (PP2A) in endothelial cell (EC) barrier regulation (Tar et al. [2004] J Cell Biochem 92:534-546). In order to further elucidate the role of PP2A in the regulation of EC cytoskeleton and permeability, PP2A catalytic (PP2Ac) and A regulatory (PP2Aa) subunits were cloned and human pulmonary arterial EC (HPAEC) were transfected with PP2A mammalian expression constructs or infected with PP2A recombinant adenoviruses. Immunostaining of PP2Ac or of PP2Aa + c overexpressing HPAEC indicated actin cytoskeleton rearrangement. PP2A overexpression hindered or at least dramatically reduced thrombin- or nocodazole-induced F-actin stress fiber formation and microtubule (MT) dissolution. Accordingly, it also attenuated thrombin- or nocodazole-induced decrease in transendothelial electrical resistance indicative of barrier protection. Inhibition of PP2A by okadaic acid abolished its effect on agonist-induced changes in EC cytoskeleton; this indicates a critical role of PP2A activity in EC cytoskeletal maintenance. The overexpression of PP2A significantly attenuated thrombin- or nocodazole-induced phosphorylation of HSP27 and tau, two cytoskeletal proteins, which potentially could be involved in agonist-induced cytoskeletal rearrangement and in the increase of permeability. PP2A-mediated dephosphorylation of HSP27 and tau correlated with PP2A-induced preservation of EC cytoskeleton and barrier maintenance. Collectively, our observations clearly demonstrate the crucial role of PP2A in EC barrier protection.

Cardiovascular gene delivery: The good road is awaiting

Atherosclerotic cardiovascular disease is a leading cause of death worldwide. Despite recent improvements in medical, operative, and endovascular treatments, the number of interventions performed annually continues to increase. Unfortunately, the durability of these interventions is limited acutely by thrombotic complications and later by myointimal hyperplasia followed by progression of atherosclerotic disease over time. Despite improving medical management of patients with atherosclerotic disease, these complications appear to be persisting. Cardiovascular gene therapy has the potential to make significant clinical inroads to limit these complications. This article will review the technical aspects of cardiovascular gene therapy; its application for promoting a functional endothelium, smooth muscle cell growth inhibition, therapeutic angiogenesis, tissue engineered vascular conduits, and discuss the current status of various applicable clinical trials.

Gene transfer of prostaglandin synthase maintains patency of the newborn lamb arterial duct

In congenital heart disease with left- or right-sided obstruction, prostaglandin E (PGE)1 or PGE2 is infused to maintain ductus arteriosus (DA) patency. We hypothesized that transfection of the DA with PGE synthase would lead to a greater production of PGE2 in situ and, hence, patency of the DA. The cDNA for human prostaglandin synthase was sequenced and ligated into a eukaryotic expression vector. The negative control was created by ligating the cDNA encoding the bacterial protein chloramphenicol acetyltransferase into the same plasmid. Transfection (600 microg DNA) was achieved in lambs within the first 24 h of life using the hemagglutinating virus of Japan (HVJ)-liposome transfection method with a custom-made, basket-weave-perforated catheter. Echocardiography was performed to assess DA patency until the time of sacrifice. To confirm expression of the transgene, PGE2 concentration was measured in organ culture of the DA by immunoassay and by Western immunoblotting of homogenized DA tissue. Patency of the DA was demonstrated by color Doppler in all the lambs (7/7) in which the PGE synthase was delivered, whereas functional closure was seen in the control group (6/6). The PGE2 concentration in the culture medium of the explanted DA in the treatment group was 3-fold higher than that of the control groups. Western immunoblotting confirmed the presence of PGE synthase in the treatment group. Gene transfer of PGE synthase to the DA is feasible and will maintain patency for at least 1 wk.

Transfection efficiency and uptake process of polyplexes in human lung endothelial cells: a comparative study in non-polarized and polarized cells

BACKGROUND

Following systemic administration, polyplexes must cross the endothelium barrier to deliver genes to the target cells underneath. To design an efficient gene delivery system into lung epithelium, we evaluated capture and transfection efficiencies of DNA complexed with either Jet-PEI (PEI-polyplexes) or histidylated polylysine (His-polyplexes) in human lung microvascular endothelial cells (HLMEC) and tracheal epithelial cells.

METHODS

After optimizing growth conditions to obtain a tight HLMEC monolayer, we characterized uptake of polyplexes by flow cytometry and evaluated their transfection efficiency. Polyplexes were formulated as small particles. YOYO-labelled plasmid fluorescence intensity and luciferase activity were used as readouts for uptake and gene expression, respectively.

RESULTS

PEI-polyplexes were more efficiently taken up than His-polyplexes by both non-polarized (2-fold) and polarized HLMEC (10-fold). They were mainly internalized by a clathrin-dependent pathway whatever the cell state. In non-polarized cells, His-polyplexes entered also mainly via a clathrin-dependent pathway but with an involvement of cholesterol. The cell polarization decreased this way and a clathrin-independent pathway became predominant. PEI-polyplexes transfected more efficiently HLMEC than His-polyplexes (10(7) vs. 10(5) relative light units (RLU)/mg of proteins) with a more pronounced difference in polarized cells. In contrast, no negative effect of the cell polarization was observed with tracheal epithelial cells in which both polyplexes had comparable efficiency.

CONCLUSIONS

We show that the efficiency of polyplex uptake by HLMEC and their internalization mechanism are polymer-dependent. By contrast with His-polyplexes, the HLMEC polarization has little influence on the uptake process and on the transfection efficiency of PEI-polyplexes.

Gene therapy in tissue-engineered blood vessels

Cardiovascular disease is the leading cause of morbidity and mortality in Western society. More than 1 million arterial bypass procedures are performed annually in the United States, where either autologous veins or synthetic grafts are used to replace arteries in the coronary or peripheral circulation. Tissue engineering of blood vessels from autologous cells has the potential to produce biological grafts for use in bypass surgery. Ex vivo development of vascular grafts also provides an ideal target of site-specific gene therapy to optimize the physiology of the developing conduit, and for the possible delivery of other therapeutic genes to a vascular bed of interest. In this article, we demonstrate that by using a novel retroviral gene delivery system, a target gene of interest can be specifically delivered to the endothelial cells of a developing engineered vessel. Further, we demonstrate that this technique results in stable incorporation of the delivered gene into the target endothelial cells for more than 30 days. These data demonstrate the utility of the retroviral gene delivery approach for optimizing the biologic phenotype of engineered vessels. This also provides the framework for testing an array of genes that may improve the function of engineered blood vessels after surgical implantation.

Nitric oxide synthase gene transfer inhibits biological features of bypass graft disease in the human saphenous vein

BACKGROUND

Bypass graft disease is related to proliferation and migration of vascular smooth muscle cells and to platelet activation with thrombus formation. Nitric oxide inhibits these biological responses; it has never been demonstrated, however, whether this occurs in intact human vascular tissue after endothelial nitric oxide synthase gene transfer.

METHODS

We examined whether endothelial nitric oxide synthase overexpression inhibits biological features of bypass graft disease in saphenous vein tissue.

RESULTS

The nitric oxide donor diethylenetriamineNONOate inhibited proliferation (P <.001) and migration (P <.001) of human saphenous vein vascular smooth muscle cells in response to 20% serum in a concentration-dependent manner. A similar effect on proliferation (P <.05) and migration (P <.05) without any cytotoxicity was observed after adenoviral endothelial nitric oxide synthase transfection. Staining of saphenous vein tissue for placental alkaline phosphatase demonstrated that adenoviral transfection was efficient. Consistent with this observation, endothelial nitric oxide synthase protein expression and nitric oxide release were enhanced in transfected tissue. Further, endothelial nitric oxide synthase overexpression inhibited vascular smooth muscle cell outgrowth from saphenous vein explants over 21 days; 48% +/- 12% of explants exhibited outgrowth after treatment with endothelial nitric oxide synthase adenovirus as compared with 69% +/- 10% in those infected with control adenovirus and 90% +/- 5% in uninfected tissue (P <.05). Similarly, platelet adhesion to human saphenous vein tissue was inhibited by endothelial nitric oxide synthase overexpression; adhesion was reduced in segments infected with endothelial nitric oxide synthase adenovirus (58% +/- 6%) as compared with those infected with control adenovirus (107% +/- 8%) or uninfected saphenous vein (100%; P <.05).

CONCLUSIONS

These data demonstrate that endothelial nitric oxide synthase gene transfer inhibits biological features of bypass graft disease in intact human saphenous vein tissue. Therefore, endothelial nitric oxide synthase transfection represents a promising gene transfer approach to prevent venous bypass graft disease.

A highly efficient electroporation method for the transfection of endothelial cells

Several approaches have been described for improving transfection efficiencies of endothelial cells but the general observations have indicated that yields of transfected endothelial cells are low, irrespective of the techniques used. Here we describe a transfection procedure performed by means of electroporation, with efficiencies up to 85%, by optimizing several parameters such as the electroporation buffer, number of cells, voltage, capacitance and pulse length. The protocol was applied to three endothelial cell types (HUVECs, HUAECs and HMEC-1) commonly used in 'in vitro' angiogenic assays. We did not observe functional impairment between transfected and non-transfected cells in their adhesion to different components of the extracellular matrix, migration, or the development of capillary-like structures. Our experiments show that this electroporation procedure does not alter the physiology of endothelial cells and can be applied to functional studies, as exemplified by the successful transfection of the isoform 1 of calcipressin 1 (CALP1L).

Magnetofection potentiates gene delivery to cultured endothelial cells

Modification of cellular functions by overexpression of genes is increasingly practised for research of signalling pathways, but restricted by limitations of low efficiency. We investigated whether the novel technique of magnetofection (MF) could enhance gene transfer to cultured primary endothelial cells. MF of human umbilical vein endothelial cells (HUVEC) increased transfection efficiency of a luciferase reporter gene up to 360-fold compared to various conventional transfection systems. In contrast, there was only an up to 1.6-fold increase in toxicity caused by MF suggesting that the advantages of MF outbalanced the increase in toxicity. MF efficiently increased transfection efficiency using several commercially available cationic lipid transfection reagents and polyethyleneimine (PEI). Using PEI, even confluent HUVEC could be efficiently transfected to express luciferase activity. Using a green fluorescent protein vector maximum percentages of transfected cells amounted up to 38.7% while PEI without MF resulted in only 1.3% transfected cells. Likewise, in porcine aortic endothelial cells MF increased expression of a luciferase or a beta-galactosidase reporter, reaching an efficiency of 37.5% of cells. MF is an effective tool for pDNA transfection of endothelial cells allowing high efficiencies. It may be of great use for investigating protein function in cell culture experiments.

AP-4F, antennapedia peptide linked to an amphipathic alpha helical peptide, increases the efficiency of Lipofectamine-mediated gene transfection in endothelial cells

Typically, endothelial cells are difficult to transfect. In this study, we report that antennapedia peptide (AP) linked to L-4F, a water-soluble, amphipathic alpha helical peptide that avidly binds lipids (AP-4F) increases Lipofectamine 2000-mediated transfection of bovine coronary endothelial cell cultures. Transfection efficiency was monitored by flow cytometry and fluorescent microscopy. Lipofectamine 2000 transfection of endothelial cell cultures with green fluorescence protein (GFP)-DNA typically yields transfection efficiencies of 35.4+/-3.3% with low levels of cell death (8.1+/-1.0%). Pre-treatment of the Lipofectamine 2000-GFP-DNA complexes with AP-4F for 5 min increased transfection to 58.2+/-2.8% without increasing cell death. AP-4F increases Lipofectamine 2000-mediated transfection in a time-dependent fashion (within 10-20 min). Systematic studies reveal that the individual components of AP-4F, i.e., AP and L-4F alone, are ineffective in increasing Lipofectamine 2000-mediated transfection and that AP-4F must be directly associated with DNA liposomes prior to transfection for optimal uptake by endothelial cells. These observations demonstrate that AP-4F may be useful for increasing the transfection efficiency of endothelial cell cultures with standard commercially available reagents.

Magnetofection--a highly efficient tool for antisense oligonucleotide delivery in vitro and in vivo

Delivery of antisense oligodesoxynucleotides (ODN) into primary cells is a specific strategy for research with therapeutic perspectives but transfection-associated difficulties. We established the technique of magnetofection to enhance ODN delivery at low toxicity and procedure time in vitro and in vivo. In vitro, target knockout was assessed at protein and mRNA levels and by measuring superoxide generation after antisense magnetofection against the p22(phox) subunit of endothelial NAD(P)H-oxidase. Under magnetic field guidance, low-dose magnetic particle-bound ODN were transfected to 84% human umbilical vein endothelial cells within 15 min followed by nuclear accumulation within 2 h, which required 24 h using standard methods. Antisense magnetofection against p22(phox) significantly decreased basal and prevented stimulated superoxide release due to loss of NAD(P)H-oxidase activity by mRNA knockout as assessed after 24 h. Knockout of endothelial phosphatase SHP-1 and connexin 37 proteins confirmed the method's efficiency. Transfection-associated toxicity was minimal. Twenty-four hours after injection of fluorescence-labeled ODN into femoral arteries of male mice, there was specific ODN uptake only into cremaster vessels exposed to magnetic fields during injection. Magnetofection is an ideal tool for delivery of functionally active ODN to difficult-to-transfect cells to study gene/protein function and a promising strategy for targeted ODN delivery in vivo.

Genetic therapies and xenotransplantation

The number of patients in need of an organ transplant is increasing, while the number of satisfactory sources of organs has declined in many countries [101]. The resulting shortage of human organs has spurred an urgent effort to investigate alternative therapies, including the use of animal organs, tissues and cells (i.e., xenotransplantation). Advances in genetic engineering have provided essential tools for the development of practical solutions to human disease. The area of xenotransplantation is no exception. In fact, the use of genetic therapies is especially attractive in the transplant setting as it offers an opportunity to manipulate the donor tissue rather than the recipient. This review will describe the obstacles in the clinical application of xenotransplantation and how genetic engineering might be used to address them.

Characterization of nanoparticle uptake by endothelial cells

Endothelium is an important target for drug or gene therapy because of its important role in the biological system. In this paper, we have characterized nanoparticle uptake by endothelial cells in cell culture. Nanoparticles were formulated using poly DL-lactide-co-glycolide polymer containing bovine serum albumin as a model protein and 6-coumarin as a fluorescent marker. It was observed that the cellular uptake of nanoparticles depends on the time of incubation and the concentration of nanoparticles in the medium. The uptake of nanoparticles was rapid with confocal microscopy demonstrating their localization mostly in the cytoplasm. The mitogenic study demonstrated biocompatability of nanoparticles with the cells. The study thus demonstrates that nanoparticles could be used for localizing therapeutic agents or gene into endothelial cells. Nanoparticles localized in the endothelium could provide prolonged drug effects because of their sustained release characterics, and also could protect the encapsulated agent from enzymatic degradation.

Genetic modification of alphaGal expression in xenogeneic endothelial cells yields a complex immunological response

The source of cells for tissue engineering applications remains a hurdle, predominantly for procedures in which there is insufficient time to harvest a patient's own cells. Animal cells are readily available, but undergo immune rejection. Rejection of animal (i.e., xenogeneic) tissue involves practically every component of the immune system. The initial phase, hyperacute rejection (HAR), involves natural xenoreactive antibodies and the complement system, and leads to endothelial cell lysis and rapid tissue destruction. The cell-surface epitope, galactose-alpha(1,3)-galactose (alphaGal), is presumed to play a key role in HAR. The later stage of immune response (delayed xenograft rejection or DXR), is mediated by immune cells such as monocytes. Carbohydrates are likely also involved in DXR, but their role in this phase of the immune response is less clear. A better understanding of all stages of xenogeneic immune rejection may make it feasible to create cell lines that are immune tolerant. In these studies, we have genetically modified bovine endothelial cells to study the roles of carbohydrates in immune rejection. Our studies suggest that one or more epitopes other than alphaGal may influence complement-mediated lysis. Furthermore, antibodies, as instigators in the complement response, and monocytes appear to recognize different cell surface epitopes.

Liposome-mediated high-efficiency transfection of human endothelial cells

Liposome-mediated transfection of endothelial cells provides a valuable experimental technique to study cellular gene expression and may also be adapted for gene therapy studies. However, the widely recognized disadvantage of liposome-mediated transfection is low efficiency. Therefore, studies were performed to optimize transfection techniques in human endothelial cells. The majority of the experiments were performed with primary cultures of human umbilical vein endothelial cells (HUVEC). In addition, selected experiments were performed using human brain microvascular endothelial cells and human dermal microvascular endothelial cells. To study transfection rates, HUVEC were transfected with the pGL3 vector, containing the luciferase reporter gene, complexed with several currently available liposomes, such as different Perfect Lipid (pFx) mixtures, DMRIE-C, or lipofectin. The optimal transfection rate was achieved in HUVEC transfected for 1.5 h with 5 microg/ml of DNA plasmid in the presence of 36 microg/ml of pFx-7. In addition, transfection with the VR-3301 vector encoding for human placental alkaline phosphatase revealed that, under the described conditions, transfection efficiency in HUVEC was approximately 32%. Transfections mediated by other liposomes were less efficient. The usefulness of the optimized transfection technique was confirmed in HUVEC transfected with NF-kappaB or AP-1-responsive constructs and stimulated with TNF or LPS. We conclude that among several currently available liposomes, pFx-7 appears to be the most suitable for transfections of cultured human endothelial cells.

Cationic liposome-mediated gene transfer to rat salivary epithelial cells in vitro and in vivo

BACKGROUND

Previously we have shown that gene transfer to salivary gland epithelial cells readily occurs via recombinant adenoviruses, although the response is short-lived and results in a potent host immune response. The aim of the present study was to assess the feasibility of using cationic liposomes to mediate gene transfer to rat salivary cells in vitro and in vivo.

METHODS

Initially, for transfection in vitro, we used two cationic liposome formulations (GAP-DLRIE/DOPE and DOSPA/DOPE) complexed with plasmid encoding human growth hormone (hGH) as a reporter gene. Thereafter, using GAP-DLRIE/DOPE, plasmids were transferred to rat salivary glands in vivo, and hGH levels measured in saliva, serum and gland extracts.

RESULTS

Under optimal conditions, transfection of rat submandibular glands (SMGs) was consistently observed. Approximately 95% of the cells transfected with a plasmid encoding beta-galactosidase were acinar cells. Maximal hGH expression was obtained during the first 48 h post-transfection using a plasmid encoding the hGH cDNA and complexed with GAP-DLRIE/DOPE. hGH was detected in gland extracts and saliva, and occasionally in serum. No systemic or local gland pathology was consistently or significantly observed.

CONCLUSIONS

The levels of the reporter gene product, hGH, obtained after GAP-DLRIE/DOPE-mediated gene transfer are considerably lower (<0.5%) than those achieved with adenoviral vectors (10(8) PFU). Nonetheless, cationic liposome-mediated gene transfer to salivary glands may be useful for potential therapeutic applications.

High-efficiency transient transfection of endothelial cells for functional analysis

The definition of signaling pathways in endothelial cells has been hampered by the difficulty of transiently transfecting these cells with high efficiency. This investigation was undertaken to develop an efficient technique for the transfection of endothelial cells for functional analyses. Cells cotransfected with plasmid expressing green fluorescent protein (GFP) and the plasmid of interest were isolated by fluorescence-activated cell sorting (FACS) based on GFP expression. In the sorted cell population, a 2.5-fold enhancement in the number of cells expressing the gene of interest was observed, as confirmed by FACS analysis and Western blotting. Sorted cells retained functional properties, as demonstrated by chemotaxis to the agonist sphingosine 1-phosphate (SPP). To demonstrate the usefulness of this method for defining cellular signaling pathways, cells were cotransfected with plasmids encoding GFP and the carboxyl-terminal domain of the beta-adrenergic receptor kinase (beta ARKct), which inhibits signaling through the beta gamma dimer of heterotrimeric G-proteins. SPP-induced chemotaxis in sorted cells coexpressing beta ARKct was inhibited by 80%, demonstrating that chemotaxis was driven by a beta gamma-dependent pathway. However, no significant inhibition was observed in cells transfected with betaARKct but not enriched by sorting. Thus, we have developed a method for enriching transfected cells that allows the elucidation of crucial mechanisms of endothelial cell activation and function. This method should find wide applicability in studies designed to define pathways responsible for regulation of motility and other functions in these dynamic cells.

Toxicity, uptake kinetics and efficacy of new transfection reagents: increase of oligonucleotide uptake

Human arterial smooth muscle cell (haSMC) proliferation is stimulated by platelet-derived growth factor (PDGF) release of human arterial endothelial cells (haEC) whereas transforming growth factor-beta(1) (TGF-beta(1)) secretion by haSMC promotes extracellular matrix formation. Inhibitory concepts with antisense oligonucleotides (ASO) against those growth factors might be promising, requiring, however, sufficient transfection efficacy. Thus, toxicity and efficacy of new transfection reagents were examined. MTT tests showed that high doses >1.6 microg/ml of the liposome Cytofectin GSV((R)) (CF) and the dendrimer SuperFect (SF) reduced mitochondrial activity of haEC after > or =4 h transfection whereas viability of haSMC was not influenced. DAC-30((R)) showed significant toxic effects on haEC and haSMC at each dose after > or =4 h and Lipofectin((R)) (LF) caused complete detachment of haEC and haSMC in medium containing 10% serum. Uptake studies demonstrated that 'naked' ASO were not incorporated intracellularly whereas transfection within CF or SF resulted in a strong cytoplasmic and nuclear labeling after 2-5 h. With DAC-30, only a slight cytoplasmic fluorescence was found. SF caused an unexpected stimulation of endothelial PDGF-AB synthesis. Thus, CF was favored for inhibition studies. ELISA, Western and Northern blotting showed a significant inhibition of endothelial PDGF-B and smooth muscle TGF-beta(1) mRNA expression and synthesis after transfection for 3-5 h using 0.1-1.0 microM ASO versus control oligonucleotides. We conclude that Cytofectin GSV is superior to the other transfection reagents, predominantly at haEC, showing an improved efficacy and less toxicity than the classical liposome Lipofectin. Cytofectin GSV might offer a promising tool for antisense strategies in the treatment of vascular disorders.

Gene therapy and heart transplantation

The application of gene transfer technologies to the field of solid organ transplantation is uniquely appealing due to open access to the donor organ at the time of removal and the need for a local biological effect limited to the allograft. The objectives of gene transfer technology in the field of experimental heart transplantation include: firstly, modification of allograft phenotype and secondly, modulation of the host alloimmune response. Both objectives can theoretically decrease or eliminate the need for lifelong immunosuppression with its attendant risks. This article will review the principles and current methodology of gene transfer technology, applications of gene transfer technology to allo- and xeno- transplantation and the current status of clinical trials on gene therapy.

Nitric oxide modulates expression of cell cycle regulatory proteins: a cytostatic strategy for inhibition of human vascular smooth muscle cell proliferation

BACKGROUND

We examined the effect of NO on the proliferation and cell cycle regulation of human aortic vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

The NO donor diethylenetriamineNONOate (10(-5) to 10(-3) mol/L) inhibited proliferation in response to 10% fetal calf serum (FCS) and 100 ng/mL platelet-derived growth factor-BB in a concentration-dependent manner. This effect was not observed with disintegrated diethylenetriamineNONOate or with the parent compound, diethylenetriamine. Adenoviral transfection of endothelial NO synthase (NOS) inhibited proliferation in response to FCS, which was prevented with N(G)-nitro-L-arginine methyl ester. NOS overexpression did not inhibit proliferation in response to platelet-derived growth factor, although the transfection efficiency and protein expression were similar to those of FCS-stimulated cells. Nitrate release was selectively enhanced from FCS-treated cells, indicating that NOS was activated by FCS only. NO caused G(1) cell cycle arrest. Cytotoxicity was determined with trypan blue exclusion, and apoptosis was assessed with DNA fragmentation. Cyclin-dependent kinase 2 expression level, threonine phosphorylation, and kinase activity were inhibited. Cyclin A expression was blunted, whereas cyclin E remained unchanged. p21 expression was induced, and p27 remained unaltered. The effect on cyclin A and p21 started within 6 hours and preceded the changes in cell cycle distribution. Proliferation in response to 10% FCS was barely inhibited with 8-bromo-cGMP (10(-3) mol/L) but was blunted with both forskolin and 8-bromo-cAMP. Proliferation in response to 2% FCS was inhibited with 8-bromo-cGMP, but it did not mimic the cell cycle effects of NO.

CONCLUSIONS

NO inhibits VSMC proliferation by specifically changing the expression and activity of cell cycle regulatory proteins, which may occur independent of cGMP. Adenoviral overexpression of endothelial NOS represents a cytostatic strategy for gene therapy of vascular disease.

Roles for insulin receptor, PI3-kinase, and Akt in insulin-signaling pathways related to production of nitric oxide in human vascular endothelial cells

BACKGROUND

Previously, we demonstrated that insulin stimulates production of nitric oxide (NO) in endothelial cells. However, specific insulin-signaling pathways mediating production of NO have not been elucidated.

METHODS AND RESULTS

We developed methods for transfection of human umbilical vein endothelial cells (HUVECs) and direct measurement of NO to begin defining insulin-signaling pathways related to NO production. HUVECs were cotransfected with enhanced Green Fluorescent Protein (eGFP) and another gene of interest. Transfection efficiencies >95% were obtained by selecting cells expressing eGFP. Overexpression of insulin receptors in HUVECs resulted in an approximately 3-fold increase in production of NO in response to insulin. In contrast, HUVECs overexpressing a tyrosine kinase-deficient mutant insulin receptor had a dose-response curve similar to that of control cells. Overexpression of inhibitory mutants of either phosphatidylinositol 3-kinase (PI3K) or Akt resulted in nearly complete inhibition of insulin-stimulated production of NO. Overexpression of an inhibitory mutant of Ras had a much smaller effect.

CONCLUSIONS

Receptor kinase activity is necessary to mediate production of NO through the insulin receptor. Both PI3K and Akt contribute importantly to this process, whereas the contribution of Ras is small.

Gene-transfer systems for human endothelial cells. stewart.martin@nottingham.ac.uk

By virtue of its location and importance in a number of pathophysiological processes the endothelium represents an attractive target tissue for gene-transfer and gene-therapy strategies. Although it is important to maximise gene-transfer to endothelial cells in such strategies primary human endothelial cells have proven to be rather intransigent to a variety of transfection techniques both in vitro and in vivo. We report on the variety of techniques in current use, revealing their strengths and weaknesses, indicate the steps that should ideally be taken to optimise expression and discuss the usefulness and future directions for viral mediated transduction.

c-Jun triggers apoptosis in human vascular endothelial cells

In endothelial cells (ECs), the transcription factor c-Jun is induced by a variety of stimuli that perturb EC function. To extend our understanding of the role of c-Jun in EC physiology, we have directed overexpression of c-Jun in human umbilical vein ECs by using a tetracycline-regulated adenoviral expression system. In this study, we report a novel observation using this system. Specific expression of c-Jun is a sufficient trigger for ECs to undergo apoptosis, as demonstrated by a set of combined assays including an ELISA specific for histone-associated DNA fragmentation, DNA laddering, and TdT-mediated dUTP nick end labeling (TUNEL). Tetracycline can effectively shut off c-Jun overexpression and prevent EC apoptosis. Cleavage of poly(ADP-ribose) polymerase was also detected in ECs overexpressing c-Jun. Moreover, inhibitors of cysteine proteases blocked the apoptosis, suggesting a caspase-associated mechanism involved in proapoptotic effects of c-Jun. To gain further insight into the role of c-Jun as a pathophysiological regulator of EC death, TAM67, a dominant-negative mutant of c-Jun, was overexpressed in human umbilical vein ECs to abrogate endogenous c-Jun/activator protein-1 activation. H(2)O(2)-triggered apoptosis was largely attenuated in ECs overexpressing TAM67. Together, these results suggest that c-Jun, as a proapoptotic molecule, may play a role in mediating the cell death program in vascular endothelium.

Adenovirus-mediated overexpression of c-Jun and c-Fos induces intercellular adhesion molecule-1 and monocyte chemoattractant protein-1 in human endothelial cells

As distal targets and mediators of signal transduction pathways, activator protein-1 (AP-1), c-Jun, and c-Fos are among the primary regulators of genes involved in cell function, proliferation, and differentiation. By using adenovirus-mediated gene transfer, we show that overexpression of AP-1 proteins directly causes coinduction of gene expression of an adhesion molecule, intercellular adhesion molecule-1 (ICAM-1), and a chemokine, monocyte chemoattractant protein-1 (MCP-1), in human vascular endothelial cells (ECs). The AP-1-induced gene expression occurs through a mechanism independent of nuclear factor-kappaB. Because the induced expression of ICAM-1 and MCP-1 in ECs has been implicated in endothelial activation and a number of important vascular disorders, it is suggested that AP-1 activation may play an important role in the pathogeneses of inflammation, angiogenesis, and atherogenesis.

Endothelial cell DNA transfer and expression using petri dish electroporation and the nonreplicating vaccinia virus/T7 RNA polymerase hybrid system

The nonreplicating vaccinia virus MVA/T7 RNA polymerase hybrid system was tested with Petri dish electroporation for ectopic gene expression in human umbilical vein endothelial cells (HUVECs). A range of voltages (150-450 V), pulse times (10-40 ms), DNA concentrations (0-20 microg/ml) and infection levels (0-15 multiplicities of infection) were tested for effects on T7 promoter-directed chloramphenicol acetyltransferase (CAT) activity after MVA/T7RP infection. MVA/T7RP-directed expression was transient and at least 10 000-fold in excess of nonviral, cytomegalovirus enhancer-directed expression. Use of a Petri dish electrode with the MVA/T7RP system showed increased viability compared with a cuvette electrode. Overexpression of interleukin-2 alpha subunit (IL2Ralpha) pro- tein followed by anti-IL2Ralpha-directed magnetic immunoaffinity cell sorting allowed isolation of the transfected population. The high fidelity of cellular sorting was shown by segregation of CAT activity in the IL2Ralpha-sorted population after transfection of T7 promoter-directed bicistronic IL2Ralpha/CAT DNA. Expression of a panel of proteins including the fluorophore green fluorescent protein as detected by fluorescence microscopy and p21cip1, p27kip1, pp60c-src, FGF-1, pRb, p107 and pRb2/p130 proteins was also achieved. Thus, use of the nonreplicating vaccinia virus/T7 RNA polymerase expression system with Petri dish electroporation is feasible for certain applications for the manipulation of HUVECs by gene transfer.