Gene therapy in vascular medicine: recent advances and future perspectives

Thymosin β4-Enhancing Therapeutic Efficacy of Human Adipose-Derived Stem Cells in Mouse Ischemic Hindlimb Model

Thymosin β4 (Tβ4) is a G-actin sequestering protein that contributes to diverse cellular activities, such as migration and angiogenesis. In this study, the beneficial effects of combined cell therapy with Tβ4 and human adipose-derived stem cells (hASCs) in a mouse ischemic hindlimb model were investigated. We observed that exogenous treatment with Tβ4 enhanced endogenous TMSB4X mRNA expression and promoted morphological changes (increased cell length) in hASCs. Interestingly, Tβ4 induced the active state of hASCs by up-regulating intracellular signaling pathways including the PI3K/AKT/mTOR and MAPK/ERK pathways. Treatment with Tβ4 significantly increased cell migration and sprouting from microbeads. Moreover, additional treatment with Tβ4 promoted the endothelial differentiation potential of hASCs by up-regulating various angiogenic genes. To evaluate the in vivo effects of the Tβ4-hASCs combination on vessel recruitment, dorsal window chambers were transplanted, and the co-treated mice were found to have a significantly increased number of microvessel branches. Transplantation of hASCs in combination with Tβ4 was found to improve blood flow and attenuate limb or foot loss post-ischemia compared to transplantation with hASCs alone. Taken together, the therapeutic application of hASCs combined with Tβ4 could be effective in enhancing endothelial differentiation and vascularization for treating hindlimb ischemia.

Control the intracellular NF-κB activity by a sensor consisting of miRNA and decoy

Many diseases are associated with the abnormal activation of NF-κB and its signaling pathway. NF-κB has become an important target for disease treatment and development of new drugs. Many various NF-κB inhibitors were therefore developed; however, they have difficulties to become clinical drugs due to their adverse side effects resulted from the affected normal physiological functions of this transcription factor. To overcome this limitation, this study construct a transgenic vector that can express an artificial miRNA targeting NF-κB RelA under the control of a NF-κB-specific promoter. The promoter consists of a NF-κB decoy and a minimal promoter. The vector was named as decoy minimal promoter-artificial microRNA (DMP-amiRNA). This study verified that this vector can sense and control the intracellular NF-κB activity upon transfection. Working of the vector forms a perfect feedback loop that realizes the NF-κB self-control. With the vector in cells, the higher NF-κB activity, the higher DMP transcriptional activity, and the more amiR533 expression. DMP-amiRNA can moderately inhibit the intracellular NF-κB activity but exert no significant effect on cell viability. This study therefore develops a new strategy for inhibiting over activity of NF-κB, which should has great potential in clinical application.

Thymosin β4: multiple functions in protection, repair and regeneration of the mammalian heart

INTRODUCTION

Despite recent improvements in interventional medicine, cardiovascular disease still represents the major cause of morbidity worldwide, with myocardial infarction being the most common cardiac injury. This has sustained the development of several regenerative strategies based on the use of stem cells and tissue engineering approaches in order to achieve cardiac repair and regeneration by enhancing coronary neovascularization, modulating acute inflammation and supporting myocardial regeneration to provide new functional muscle.

AREAS COVERED

The actin monomer binding peptide, Thymosin β4 (Tβ4), has recently been described as a powerful regenerative agent with angiogenic, anti-inflammatory and cardioprotective effects on the heart and which specifically acts on its resident cardiac progenitor cells. In this review we will discuss the state of the art regarding the many roles of Tβ4 in preserving and regenerating the mammalian heart, with specific attention to its ability to activate the quiescent adult epicardium and specific subsets of epicardial progenitor cells for repair.

EXPERT OPINION

The therapeutic potential of Tβ4 for the treatment of cardiac failure is herein evaluated alongside existing, emerging and prospective novel treatments.

Coronary vessel development and insight towards neovascular therapy

Formation of the coronary arteries consists of a precisely orchestrated series of morphogenetic and molecular events which can be divided into three distinct processes: vasculogenesis, angiogenesis and arteriogenesis (Risau 1997; Carmeliet 2000). Even subtle perturbations in this process may lead to congenital coronary artery anomalies, as occur in 0.2-1.2% of the general population (von Kodolitsch et al. 2004). Contrary to the previously held dogma, the process of vasculogenesis is not limited to prenatal development. Both vasculogenesis and angiogenesis are now known to actively occur within the adult heart. When the need for regeneration arises, for example in the setting of coronary artery disease, a reactivation of embryonic processes ensues, redeploying many of the same molecular regulators. Thus, an understanding of the mechanisms of embryonic coronary vasculogenesis and angiogenesis may prove invaluable in developing novel strategies for cardiovascular regeneration and therapeutic coronary angiogenesis.

Gene therapy of Cav1.2 channel with VIP and VIP receptor agonists and antagonists: a novel approach to designing promotility and antimotility agents

Recent findings show that the enteric neurotransmitter VIP enhances gene transcription of the alpha1C subunit of Cav1.2 (L-type) Ca2+ channels in the primary cultures of human colonic circular smooth muscle cells and circular smooth muscle strips. In this study, we investigated whether systemic infusion of VIP in intact animals enhances the gene transcription and protein expression of these channels to accelerate colonic transit. We also investigated whether similar systemic infusions of VPAC1/2 receptor antagonist retards colonic transit by repressing the constitutive gene expression of the alpha1C subunit. We found that the systemic infusion of VIP for 7 days by a surgically implanted osmotic pump enhances the gene and protein expression of the alpha1C subunit and circular muscle contractility in the proximal and the middle rat colons, but not in the distal colon. A similar systemic infusion of VPAC1/2 receptor antagonist represses the expression of the alpha1C subunit and circular smooth muscle contractility in the proximal and the middle colons. The VIP infusion accelerates colonic transit and pellet defecation by rats, whereas the infusion of VPAC1/2 receptor antagonist retards colonic transit and pellet defecation. VPAC1 receptors, but not VPAC2 receptors, mediate the above gene transcription-induced promotility effects of VIP. We conclude that VIP and VPAC(1) receptor agonists may serve as potential promotility agents in constipation-like conditions, whereas VPAC receptor antagonists may serve as potential antimotility agents in diarrhea-like conditions produced by enhanced motility function.

Unilateral Lung-Selective Gene Transfer Following the Administration of Naked Plasmid DNA onto the Pulmonary Pleural Surface in Mice

The purpose of the present study was to examine unilateral lung-selective gene transfer following the administration of naked plasmid DNA (pDNA) onto the pulmonary pleural surface in mice. Naked pDNA was administered intravenously, intraperitoneally, and instilled onto the right pulmonary pleural surface. Four hours later, right pulmonary pleural surface instillation of naked pDNA resulted in high gene expression in the right lung. On the contrary, intravenous and intraperitoneal administration of naked pDNA resulted in no detectable gene expression. After instilling naked pDNA onto the right or left pulmonary pleural surface, gene expressions in the applied lung were significantly higher than those in the other lung and tissues. In addition, gene expressions were detected only in the intrathoracic tissues, not in the intraperitoneal tissues. Four hours after instillation of naked pDNA onto the right pulmonary pleural surface, gene expression in the right lung was the highest, and thereafter gene expression in the right lung decreased gradually. This novel gene transfer method is expected to be a safe and effective treatment against serious lung diseases.

Growth factor activation in myocardial vascularization: therapeutic implications

A rapid growth of the coronary vasculature occurs during prenatal and early postnatal periods as precursor cells from the epi- and sub-epicardium differentiate, migrate and form vascular structures (vasculogenesis) which then fuse, branch and in some cases recruit cells to form three tunics (angiogenesis). These processes are tightly controlled by temporally and spatially expressed growth factors which are stimulated by metabolic and mechanical factors. The process of angiogenesis in the myocardium is not limited to developmental periods of life, but may occur when the heart is challenged by enhanced loading conditions or during hypoxia or ischemia. This review focuses on the activation of growth factors by metabolic and mechanical stimuli in the developing heart and in the adult heart undergoing adaptive responses. Experimental studies support the hypotheses that both metabolic (hypoxia) and mechanical (stretch) factors serve as powerful stimuli for the up-regulation of growth factors which facilitate angiogenesis and arteriogenesis. Both hypoxia and stretch are powerful inducers of VEGF and its receptors, and provide for paracrine and autocrine signaling. In addition to the VEGF family, bFGF and angiopoietins play major roles in myocardial vascularization. Sufficient evidence supports the hypothesis that mechanical (e.g., bradycardia) and metabolic (e.g., thyroxine analogs) may provide effective non-invasive angiogenic therapies for the ischemic and post-infarcted heart.

Unilateral Kidney-Selective Gene Transfer Following the Administration of Naked Plasmid DNA to the Kidney Surface in Mice

We developed a gene transfer following the administration of naked plasmid DNA (pDNA) to the kidney surface in mice, and found that the luciferase levels produced in the applied kidney were significantly higher than those produced in another kidney. In contrast, stable renal gene expression was not observed in the case of intraperitoneal or intravenous administration of pDNA. The level of gene expression after instillation of pDNA to the kidney surface reached maximum at 12 h and gradually diminished thereafter. The production of luciferase was saturated at 5 microg of pDNA, and was not affected by instillation volume. Furthermore, pDNA uptake from the kidney surface was proved by in situ experiments using a glass-made diffusion cell. We demonstrated a novel unilateral kidney-selective gene transfer following the administration of naked pDNA to the kidney surface in mice.

Liver site-specific gene transfer following the administration of naked plasmid DNA to the liver surface in mice

The present study was undertaken to investigate liver site-specific gene transfer following the administration of naked plasmid DNA (pDNA) to the liver surface in mice. We examined whether genes could be delivered to the liver site specifically by utilizing the glass-made diffusion cell that is able to limit the contact dimension between the liver surface and pDNA solution administered. Gene expression was detected at the site of diffusion cell attachment (site 1) and was significantly higher than in other liver sites and tissues. Moreover, gene expression was also detected at deeper site from the liver surface (noncontact side with pDNA solution). The level of gene expression at site 1 did not change significantly with pDNA treatment for 10, 30, and 60 min. In conclusion, we demonstrated that naked pDNA administered to the liver surface in mice was taken up from its surface, and subsequently the protein encoded by pDNA could be produced site specifically.

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.

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.

The antimycotic ciclopirox olamine induces HIF-1alpha stability, VEGF expression, and angiogenesis

The heterodimeric hypoxia-inducible factor (HIF)-1 is a master regulator of oxygen homeostasis. Protein stability and transactivation function of the alpha subunit are controlled by iron- and oxygen-dependent hydroxylation of proline and asparagine residues. The anti-mycotic ciclopirox olamine (CPX) is a lipophilic bidentate iron chelator that stabilizes HIF-1alpha under normoxic conditions at lower concentrations than other iron chelators, probably by inhibiting HIF-1alpha hydroxylation. As shown by the inhibition of iron-dependent quenching of FITC-labeled deferoxamine (DFX) fluorescence, CPX appears to have an even higher affinity for iron than DFX. Initial observations that treatment with 1% CPX, but not with placebo, occasionally caused reddening of wound margins in a mouse skin wound model prompted us to investigate the capability of CPX to induce angiogenesis. CPX-induced HIF-1-mediated reporter gene activity and endogenous HIF-1 target gene expression, including elevation of transcription, mRNA, and protein levels of the vascular endothelial growth factor (VEGF). In the chick chorioallantoic membrane assay, inert polymer disks containing CPX but not the solvent alone induced angiogenesis. In summary, these results suggest that CPX induces angiogenesis in vivo via HIF-1 and VEGF induction. Therefore, CPX might serve as an alternative to recombinant VEGF treatment or to VEGF gene therapy for therapeutic angiogenesis.

Synthesis and application of functional peptides as cell nucleus-directed molecules in the treatment of malignant diseases

The unique functions of biomolecules, including transport across biological membranes (e.g. the cell membrane, the nuclear envelope), modulation of protein function, gene transcription, reconstitution of the malignant transformation, and viral, bacterial and fungal activities underlie a high pharmaceutical potential. The development of combinatorial functional peptide modules in this important area has been slow, in contrast to the rapid development in the synthesis of small biopolymers. The conjugation of a short transmembrane transport peptide module with a cell nucleus address peptide module and with any substance is attractive for preparation of BioShuttle-based peptides because of the well-established automated synthesis of peptides. Variation of the different functional modules for drug targeting and the choice of substances can be combined to create novel bioconjugates with unique properties. This article provides an overview of previous work on the BioShuttle technology and outlines the promising use of this approach in combinatorial peptide synthesis and drug discovery.

Baroreceptor reflex pathways and neurotransmitters: 10 years on

The central nervous system plays a critical role in the management of blood flow to the tissues and its return to the heart and lungs. This is achieved by a complex interplay of neural efferent pathways, humoral mechanisms and afferent pathways. In this review, we focus on recent progress (within the past 10 years) that has been made in the sympathetic control of arterial blood pressure with a special emphasis on the role of baroreceptor mechanisms and central neurotransmitters. In particular, we focus on new features since 1991, such as neurotransmission in the nucleus tractus solitarius, the role of neurons in the most caudal part of the ventrolateral medulla oblongata and the increasing understanding of the exquisite control of different sympathetic pathways by different neurotransmitter systems.