Gene therapy for cerebrovascular disease

Tethering of spherical DOTAP liposome gold nanoparticles on cysteamine monolayer for sensitive label free electrochemical detection of DNA and transfection

Construction of spherical liposomes is critical for developing tools for targeted gene and drug delivery applications in biotechnology and medicine, however, it has been demonstrated only in solution phase until now. Spherical liposome tethering on pristine thiol monolayer on gold transducer and its application to label free DNA sensing and transfection has rarely been reported. Here, we report tethering of spherical 1,2-dioleoyltrimethylammoniumpropane liposome-gold nanoparticle (DOTAP-AuNP) on amine terminated monolayer by simple electrostatic interaction on gold transducer for the first time. Cuddling of cationic liposome by AuNP prevents spherical vesicle fusion in both liquid and solid phases, an essential criterion required for gene and drug delivery applications. The spherical nature of DOTAP-AuNPs on a gold surface is confirmed electrochemically using both [Fe(CN)6](3-/4-) and [Ru(NH3)6](3+) redox probes. Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS) and ultraviolet-visible (UV) spectroscopic techniques confirm the robust nature of spherical liposome-AuNPs on solid and in liquid phases. The surface is applied for label free DNA hybridization and single nucleotide polymorphism detections sensitively and selectively without signal amplification. The lowest target DNA concentration detected is 100 attomole. DNA transfection is made simply by dropping E. coli cells on DOTAP-AuNP-DNA immobilized transducer surface. The difference between the fluorescent image of transfected E. coli and the differential interference contrast image of E. coli cells by confocal laser scanning microscopy (CLSM) confirms the efficiency and simplicity of the transfection method developed in terms of reduced cost and reagents.

THE TRANSGENIC ARTERIOVENOUS FISTULA IN THE RAT: AN EXPERIMENTAL MODEL OF GENE THERAPY FOR BRAIN ARTERIOVENOUS MALFORMATIONS

OBJECTIVE

To introduce the transgenic arteriovenous fistula model in the rat, constructed by interposing mouse aorta in a fistula between the common carotid artery and external jugular vein in a nude rat, and to describe the model's technical feasibility, long-term patency, and expression of reporter genes.

METHODS

Carotid-jugular fistulae were surgically created in 112 rats. In 25 immunodeficient nude rats, wild-type mouse thoracic aorta (TAo) was interposed in the fistula; in 10 immunocompetent rats, TAo was interposed; in 19 nude rats, transgenic TAo with reporter genes for beta-galactosidase or green fluorescent protein was interposed; in 18 nude rats, wild-type mouse ascending aorta was interposed; and in 40 rats, a simple fistula was constructed without an interpositional graft. Host tolerance and graft viability were analyzed by histopathology and immunohistochemistry for CD31 (mouse endothelial cell marker), endothelial nitric oxide synthase, smooth muscle actin, fibronectin, beta-galactosidase, and green fluorescent protein.

RESULTS

The transgenic arteriovenous fistula was technically feasible and immunologically tolerated in nude rats but not in immunocompetent rats. The overall angiographic patency rate was 41% with TAo grafts and 56% with ascending aorta grafts, both lower than the 98% patency rate in fistulae with a single anastomosis and no interpositional graft. Mouse endothelium survived on the graft for 3 months according to CD31 staining, but longer survival by transgenic smooth muscle cells resulted in continued expression of beta-galactosidase for 6 months and green fluorescent protein for 4 months. Endothelium and smooth muscle in the fistula were functional, with normal expression of endothelial nitric oxide synthase as well as smooth muscle actin and fibronectin, respectively.

CONCLUSION

The transgenic arteriovenous fistula model enhances other carotid-jugular fistula models by integrating transgenic tissue, thereby creating an experimental system for investigating the molecular biology of and gene therapies for arteriovenous malformations.

Translational paradigms in cerebrovascular gene transfer

Gene transfer involves the use of an engineered biologic vehicle known as a vector to introduce a gene encoding a protein of interest into a particular tissue. In diseases with known defects at a genetic level, gene transfer offers a potential means of restoring a normal molecular environment via vector-mediated entry (transduction) and expression of genes encoding potentially therapeutic proteins selectively in diseased tissues. The technology of gene transfer therefore underlies the concept of gene therapy and falls under the umbrella of the current genomics revolution. Particularly since 1995, numerous attempts have been made to introduce genes into intracranial blood vessels to demonstrate and characterize viable transduction. More recently, in attempting to translate cerebrovascular gene transfer technology closer to the clinical arena, successful transductions of normal human cerebral arteries ex vivo and diseased animal cerebral arteries in vivo have been reported using vasomodulatory vectors. Considering the emerging importance of gene-based strategies for the treatment of the spectrum of human disease, the goals of the present report are to overview the fundamentals of gene transfer and review experimental studies germane to the clinical translation of a technology that can facilitate genetic modification of cerebral blood vessels.

Endovascular restorative neurosurgery: a novel concept for molecular and cellular therapy of the nervous system

The amalgam of molecular biology and neurosurgery offers immense promise for neurorestoration and the management of neurodegenerative deficiencies, developmental disorders, neoplasms, stroke, and trauma. This article summarizes present strategies for and impediments to gene therapy and stem cell therapy of the central nervous system and advances the concept of a potential new approach, namely endovascular restorative neurosurgery. The objectives of gene transfer to the central nervous system are efficient transfection of host cells, selective sustained expression of the transgene, and lack of toxicity or immune excitation. The requisite elements of this process are the identification of candidate diseases, the construction of vehicles for gene transfer, regulated expression, and physical delivery. In the selection of target disorders, the underlying genetic events to be overcome, as well as their spatial and temporal distributions, must be considered. These factors determine the requirements for the physical dispersal of the transgene, the duration of transgene expression, and the quantity of transgene product needed to abrogate the disease phenotype. Vehicles for conveying the transgene to the central nervous system include viral vectors (retroviruses, lentiviruses, adenoviruses, adeno-associated viruses, and herpes simplex virus), liposomes, and genetically engineered cells, including neural stem cells. Delivery of the transgene into the brain presents several challenges, including limited and potentially risky access through the cranium, sensitivity to volumetric changes, restricted diffusion, and the blood-brain barrier. Genetic or cellular therapeutic agents may be injected directly into the brain parenchyma (via stereotaxy or craniotomy), into the cerebrospinal fluid (in the ventricles or cisterns), or into the bloodstream (intravenously or intra-arterially). The advantages of the endovascular route include the potential for widespread distribution, the ability to deliver large volumes, limited perturbation of neural tissue, and the feasibility of repeated administration.

Prevention of impairment of cerebral blood flow autoregulation during acute stage of subarachnoid hemorrhage by gene transfer of Cu/Zn SOD-1 to cerebral vessels

The present study determined whether gene transfer of human copper/zinc superoxide dismutase-1 (Cu/Zn SOD-1) prevented the autoregulatory impairment of CBF induced by subarachnoid hemorrhage (SAH). After application of recombinant adenovirus (100 microL of 1 x 10(10) pfu/mL, intracisternally) encoding human Cu/Zn SOD-1 3 days before experiments, Cu/Zn SOD-1 activity significantly increased in association with increase in Cu/Zn SOD-1 mRNA and protein expression in the cerebral vasculature of both sham-operated and SAH rats as determined by reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry, and SAH-induced increase in superoxide anion was markedly reduced in accordance with increased nitric oxide production. In line with these findings, rats that received human Cu/Zn SOD-1 therapy showed the prominent restoration of blunted vasodilation of the pial artery in response to calcitonin gene-related peptide and levcromakalim, and the recovery of impaired autoregulatory vasodilation in response to acute hypotension, thereby leading to significant restoration of CBF autoregulation. These results provide a rational basis for application of Cu/Zn SOD-1 gene therapy for protection of the impairment of autoregulatory CBF during the acute stage of SAH.

Evaluation of lipid-based reagents to mediate intracellular gene delivery

We characterized different cationic lipid-based gene delivery systems consisting of both liposomes and nonliposomal structures, in terms of their in vitro transfection activity, resistance to the presence of serum, protective effect against nuclease degradation and stability under different storage conditions. The effect of lipid/DNA charge ratio of the resulting complexes on these properties was also evaluated. Our results indicate that the highest levels of transfection activity were observed for complexes prepared from nonliposomal structures composed of FuGENE 6. However, their DNA protective effect was shown to be lower than that observed for cationic liposome formulations when prepared at the optimal (+/-) charge ratio. Our results suggest that lipoplexes are resistant to serum up to 30% when prepared at a 2:1 lipid/DNA charge ratio. However, when they were prepared at higher (+/-) charge ratios, they become sensitive to serum for even lower concentrations (10%). Replacement of dioleoyl-phosphatidylethanolamine (DOPE) by cholesterol enhanced the resistance of the complexes to the inhibitory effect of serum. This different biological activity in the presence of serum was attributed to different extents of binding of serum proteins to the complexes, as evaluated by the immunoblotting assay. Studies on the stability under storage show that lipoplexes maintain most of their biological activity when stored at -80 degrees C, following their fast freezing in liquid nitrogen.

Gene transfer of Cu/Zn SOD to cerebral vessels prevents FPI-induced CBF autoregulatory dysfunction

The goal of this study was to determine whether gene transfer of human copper-zinc (Cu/Zn) superoxide dismutase (SOD) has preventive effects on cerebral blood flow (CBF) autoregulatory dysfunction after fluid percussion injury (FPI). Rats subjected to FPI (2-2.5 atm) exhibited enhanced activity of reduced NADP (NADPH) oxidase in the cerebral vasculature. In line with these findings, the rats showed not only reduced vasodilation of the pial artery in response to calcitonin gene-related peptide and levcromakalim but also impaired autoregulatory vasodilation in response to acute hypotension. The FPI-induced hemodynamic alterations were significantly prevented by pretreatment with diphenyleneiodonium (10 micromol/l), an NAD(P)H oxidase inhibitor. Intracisternal application of recombinant adenovirus (100 microl of 1 x 10(10) pfu/ml)-encoding human Cu/Zn SOD 3 days before FPI prevented the impairment of vasodilation to hypotension and vasorelaxants, resulting in the restoration of CBF autoregulation. Our findings demonstrate that FPI-induced impairment of CBF autoregulation is closely related with NAD(P)H oxidase-derived superoxide anion, and these alterations can be prevented by the recombinant adenovirus-mediated transfer of human Cu/Zn SOD gene to the cerebral vasculature.

Transduction of human neural progenitor cells using recombinant adeno-associated viral vectors

Human neural progenitor cells (hNPCs) represent an attractive source for cell therapy of neurological disorders. Genetic modification of hNPCs may allow a controlled release of therapeutic proteins, suppress immune rejection, or produce essential neurotransmitters. In search of an effective gene delivery vehicle, we evaluated the efficiency of a recombinant adeno-associated viral (rAAV) vector expressing enhanced green fluorescent protein (CAGegfp). Our study demonstrated that CAGegfp efficiently transduced both proliferating and differentiated hNPCs in vitro. EGFP expression was detected as early as 1 day after exposure to CAGegfp and was detectable for up to 4 months. Following transduction, the growth rate of hNPCs slowed down, but they were still able to differentiate into neurons and glia. Furthermore, CAGegfp-modified hNPCs survived, differentiated and expressed EGFP after transplanting into spinal cord of adult rats. Our results indicated that rAAV vectors might be a useful tool in hNPC-based cell and gene therapy for neurological disorders.

Gene transfer for experimental saccular aneurysms

SUMMARY

Reinforcing an aneurysmal wall is one possible way to prevent from aneurysm rupture. We preliminarily tried focal gene transfer against the wall of experimental aneurysms to aim the transgene remodeling of aneurysmal wall. Two experimental saccular aneurysms were created on canine common carotid artery with an artificial dissecting method, which resemble clinical aneurysms. Adenovirus vector (AxCALacZ, 10(8) pfu) was slowly injected into the aneurysm cavity for over 30 minutes under the condition of intraaneurysmal flow arrest using balloon-assisted neck-plasty technique. The arteries and aneurysms were evaluated 48 hours after the transduction with X-gal staining, and beta-galactosidase expression was detected mainly in the intima in both cases. No adverse effects on the normal carotid wall and no systemic complications were observed after the procedure. This experimental study suggests the possibility of gene therapy for cerebral aneurysms.

Adenoviral-mediated transfer of tissue plasminogen activator gene into brain capillary endothelial cells in vitro

Tissue plasminogen activator (tPA) has a critical role in fibrinolysis, converting plasminogen into active protease plasmin. Because intravenous tPA has only limited effectiveness as acute stroke therapy, enhancement of endogenous tPA represents a potential alternative to stroke treatment. Adenoviral-mediated gene transfer was used to enhance production of tPA in bovine brain capillary endothelial cells (BEC). Antigen and activity levels of tPA and plasminogen activator inhibitor-1 (PAI-1) in media from BEC infected with AdCMVtPA were analyzed. Conditioned media were analyzed for thrombomodulin, the integral membrane antithrombotic molecule that co-activates protein C. BEC infected with AdCMVtPA demonstrated enhanced expression of tPA antigen (40.2 +/- 0.4 ng/mL vs 1.1 +/- 1.5 ng/mL [p<0.001] and 0.3 +/- 0.5 ng/mL [p<0.0001], respectively) and increased tPA enzymatic activity (27.4 +/- 5.7 IU/mL vs 8.3 +/- 1.7 IU/mL [p<0.05] and 13.3 +/- 3.2 IU/mL [p<0.05], respectively) compared to BEC infected with the control adenovirus (Adl327) or uninfected BEC. There was a moderate increase in PAI-1 protein 4 days after transfection with AdCMVtPA, and the integral membrane protein thrombomodulin was released into media by transfected BEC. These results demonstrate that adenoviral-mediated delivery in vitro of the human tPA gene resulted in high levels of expression of tPA in BEC. Transient overexpression of tPA by gene transfer might be a useful strategy to protect against thrombotic occlusion during the period of risk of acute stroke.

Characterization and quality control of recombinant adenovirus vectors for gene therapy

Highly purified recombinant adenovirus undergoes routine quality controls for identity, potency and purity prior to its use as a gene therapy vector. Quantitative characterization of infectivity is measurable by the expression of the DNA binding protein, an early adenoviral protein, in an immunofluorescence bioassay on permissive cells as a potency determinant. The specific particle count, a key quality indicator, is the total number of intact particles present compared to the number of infectious units. Electron microscopic analysis using negative staining gives a qualitative biophysical analysis of the particles eluted from anion-exchange HPLC. One purity assessment is accomplished via the documented presence and relative ratios of component adenoviral proteins as well as potential contaminants by reversed-phase HPLC of the intact virus followed by protein peak identification using MALDI-TOF mass spectrometry and subsequent data mining. Verification of the viral genome is performed and expression of the transgene is evaluated in in vitro systems for identity. Production lots are also evaluated for replication-competent adenovirus prior to human use. For adenovirus carrying the human IL-2 transgene, quantitative IL-2 expression is demonstrated by ELISA and cytokine potency by cytotoxic T lymphocyte assay following infection of permissive cells. Both quantitative and qualitative analyses show good batch to batch reproducibility under routine test conditions using validated methods.

In vivo protein expression from mRNA delivered into adult rat brain

The expression of proteins after local mRNA delivery has a great potential for analysis of protein function in vivo. To explore the feasibility of such a technique within the central nervous system (CNS), we delivered luciferase-encoding mRNA into the rat brain. The tissue distribution and stability of injected mRNA were analyzed using in situ detection and Northern hybridization, while luciferase expression was measured by enzymatic assay. Following intracerebral injection of lipofectin-complexed mRNA, expression of luciferase was detectable as early as 1 h, was maximal at 2-3 h, but was below the level of detection by 24 h. The extent of luciferase expression correlated with the amount of mRNA delivered. Luciferase expression was higher when lipofectin-complexed rather than naked mRNA was injected. In addition, the luciferase expression increased significantly by adding a 50 nt-long poly(A) tail to the 3'-end of the mRNA. Delivering mRNA to the cerebral cortex or hippocampus resulted in measurable luciferase activity at the injection sites but not in adjacent areas. Accordingly, the luciferase mRNA was also localized to the injection site, and the amount of intact transcript was significantly higher at 3 h compared to 24 h after injection. These results demonstrate that in vivo mRNA delivery is a feasible technique for immediate, transient overexpression of desired proteins in the CNS and, therefore, can serve as a model system to study the neurobiological effects of specific proteins.

Gene therapy for brain tumors

"Gene therapy" can be defined as the transfer of genetic material into a patient's cells for therapeutic purposes. To date, a diverse and creative assortment of treatment strategies utilizing gene therapy have been devised, including gene transfer for modulating the immune system, enzyme prodrug ("suicide gene") therapy, oncolytic therapy, replacement/therapeutic gene transfer, and antisense therapy. For malignant glioma, gene-directed prodrug therapy using the herpes simplex virus thymidine kinase gene was the first gene therapy attempted clinically. A variety of different strategies have now been pursued experimentally and in clinical trials. Although, to date, gene therapy for brain tumors has been found to be reasonably safe, concerns still exist regarding issues related to viral delivery, transduction efficiency, potential pathologic response of the brain, and treatment efficacy. Improved viral vectors are being sought, and potential use of gene therapy in combination with other treatments is being investigated.

Canine models for human genetic neurodegenerative diseases

1. Canine models of human neurodegenerative disorders are uncommon. However, the similarity between canines and humans in body sizes and physiology provides an exceptional opportunity to use these models to study human diseases. 2. The authors will present a review on the neurological deficits that have been observed in canine models of genetic neurodegenerative diseases, and summarize the current gene therapy treatments being developed for some of these conditions.

Introduction to gene therapy in neurological surgery

Gene therapy is an exciting new discipline in which neurosurgery and neurosurgeons can have a direct impact on both patient care and emerging scientific developments. Unlike other organs, the brain is unique in that it has a blood–brain barrier, often preventing efficient systemic gene delivery to the area of interest. Therefore, not only is gene delivery required, but it will often need to be accomplished in a local and specific manner. Although brain neoplasms have been the most commonly studied application of genetic therapeutics in neurological surgery, there are many other potential applications of this technology to neurosurgical disorders, including spinal instability, neurodegenerative disease, neurogenetic diseases, central nervous system (CNS) injury, aneurysms, trauma, stroke, and epilepsy. As the field of gene therapy for the CNS develops from the preclinical setting to clinical trials to mainstream therapy, the need for safe and specific gene delivery will be increasingly apparent. Neurosurgeons are in an enviable position as there is nobody more qualified to address the issue of how a gene can be delivered to the central nervous system. Not only do we have the training to operate on the nervous system and its coverings, but we have the ability to recognize and take care of complications that may arise from these procedures. However, the neurosurgeon's role in gene therapy for the brain and spine should not be confined to gene delivery only. Instead, we also need to understand and have a role in deciding what genes could have therapeutic utility in our patients. Herein lies our challenge in gene therapy: how can we as neurosurgeons interface with our basic science colleagues to address rapidly all of the problems that are blocking the advancement of nucleic acid therapeutics into the clinical setting.

Reprogramming the male gamete genome: a window to successful gene therapy

Hematopoiesis and spermatogenesis both initiate from a stem cell capable of renewal and differentiation. Each pathway reflects the expression of unique combinations of facultative, i.e. tissue-specific and constitutive, i.e. housekeeping, genes in each cell type. In spermatogenesis, as in hematopoiesis, commitment is mediated by the mechanism of potentiation whereby specific chromatin domains are selectively opened along each chromosome. Within each open chromatin domain, a unique battery of gene(s) is availed to tissue-specific and ubiquitous transacting factors that are necessary to initiate transcription. In the absence of an open domain, trans-factor access is denied, and the initiation of transcription cannot proceed. Cell-fate is thus ultimately defined by the unique series of open-potentiated cell-specific chromatin domains. Defining the mechanism that opens chromatin domains is fundamental in understanding how differentiation from stem cells is controlled and whether cell-fate can be modified. A recent examination of the mammalian spermatogenic pathway [Kramer, J.A., McCarrey, J.M, Djakiew, D., Krawetz, S.A., 1998. Differentiation: the selective potentiation of chromatin domains. Development 125, 4749-4755] supports the view that cell fate is mediated by global changes in chromatin conformation. This stride underscores the possibility of moderating differentiation through chromatin conformation. It is likely that gene therapeutics capable of selectively potentiating individual genic domains in populations of differentiating and/or replicating cells that modify cellular phenotype will be developed in the next millennium.