Showing papers by "Shin-ichi Muramatsu published in 2005"

Unrestricted Hepatocyte Transduction with Adeno-Associated Virus Serotype 8 Vectors in Mice

Abstract: Recombinant adeno-associated virus (rAAV) vectors can mediate long-term stable transduction in various target tissues. However, with rAAV serotype 2 (rAAV2) vectors, liver transduction is confined to only a small portion of hepatocytes even after administration of extremely high vector doses. In order to investigate whether rAAV vectors of other serotypes exhibit similar restricted liver transduction, we performed a dose-response study by injecting mice with -galactosidase-expressing rAAV1 and rAAV8 vectors via the portal vein. The rAAV1 vector showed a blunted dose-response similar to that of rAAV2 at high doses, while the rAAV8 vector dose-response remained unchanged at any dose and ultimately could transduce all the hepatocytes at a dose of 7.2 10 12 vector genomes/mouse without toxicity. This indicates that all hepatocytes have the ability to process incoming single-stranded vector genomes into duplex DNA. A single tail vein injection of the rAAV8 vector was as efficient as portal vein injection at any dose. In addition, intravascular administration of the rAAV8 vector at a high dose transduced all the skeletal muscles throughout the body, including the diaphragm, the entire cardiac muscle, and substantial numbers of cells in the pancreas, smooth muscles, and brain. Thus, rAAV8 is a robust vector for gene transfer to the liver and provides a promising research tool for delivering genes to various target organs. In addition, the rAAV8 vector may offer a potential therapeutic agent for various diseases affecting nonhepatic tissues, but great caution is required for vector spillover and tight control of tissue-specific gene expression. Liver-directed gene transfer with viral and nonviral vectors has been explored for the treatment of a variety of inherited and acquired diseases, including hemophilia (51), various metabolic diseases such as mucopolysaccharidosis (42), hyperlipidemia (24), tyrosinemia (41), and diabetes mellitus (25), and chronic viral hepatitis (29). Among the vectors used to deliver genes to hepatocytes in vivo, recombinant adeno-associated virus (rAAV) vectors are one of the most promising vehicles because they are based on nonpathogenic viruses, transduce both dividing and nondividing cells, and achieve long-term stable transgene expression with minimal toxicity and cellular immune response in animals. AAV is a small, nonpathogenic, replication-defective parvovirus with a single-stranded DNA genome. Among the various serotypes of AAV, rAAV vectors based on AAV serotype 2 (rAAV2) have been most extensively investigated as gene delivery vectors in vivo, demonstrating efficacy and safety. Based on successful results in a series of preclinical studies for rAAV2-mediated gene therapy, several clinical trials were initiated for the treatment of inherited diseases, including hemophilia B (22).

Cerebrospinal fluid neprilysin is reduced in prodromal Alzheimer's disease.

Abstract: Amyloid beta peptide (A beta) has been implicated in Alzheimer's disease (AD) as an initiator of the pathological cascades. Several lines of compelling evidence have supported major roles of A beta-degrading enzyme neprilysin in the pathogenesis of sporadic AD. Here, we have shown a substantial reduction of cerebrospinal fluid (CSF) neprilysin activity (CSF-NEP) in patients with AD-converted mild cognitive impairment and early AD as compared with age-matched control subjects. The altered CSF-NEP likely reflects changes in neuronal neprilysin, since transfer of neprilysin from brain tissue into CSF was demonstrated by injecting neprilysin-carrying viral vector into the brains of neprilysin-deficient mice. Interestingly, CSF-NEP showed an elevation with the progression of AD. Along with a close association of CSF-NEP with CSF tau proteins, this finding suggests that presynaptically located neprilysin can be released into CSF as a consequence of synaptic disruption. The impact of neuronal damages on CSF-NEP was further demonstrated by a prominent increase of CSF-NEP in rats exhibiting kainate-induced neurodegeneration. Our results unequivocally indicate significance of CSF-NEP as a biochemical indicator to pursue a pathological process that involves decreased neprilysin activity and A beta-induced synaptic toxicity, and the support the potential benefits of neprilysin up-regulation in ameliorating neuropathology in prodromal and early AD.

Efficient and stable Sendai virus-mediated gene transfer into primate embryonic stem cells with pluripotency preserved.

Abstract: Efficient gene transfer and regulated transgene expression in primate embryonic stem (ES) cells are highly desirable for future applications of the cells. In the present study, we have examined using the nonintegrating Sendai virus (SeV) vector to introduce the green fluorescent protein (GFP) gene into non-human primate cynomolgus ES cells. The GFP gene was vigorously and stably expressed in the cynomolgus ES cells for a year. The cells were able to form fluorescent teratomas when transplanted into immunodeficient mice. They were also able to differentiate into fluorescent embryoid bodies, neurons, and mature blood cells. In addition, the GFP expression levels were reduced dose-dependently by the addition of an anti-RNA virus drug, ribavirin, to the culture. Thus, SeV vector will be a useful tool for efficient gene transfer into primate ES cells and the method of using antiviral drugs should allow further investigation for regulated SeV-mediated gene expression.

Gene therapy for Parkinson's disease using recombinant adeno-associated viral vectors.

Abstract: Existing strategies for gene therapy in the treatment of Parkinson’s disease include the delivery of genes encoding dopamine (DA)-synthesising enzymes, leading to localised production of DA in the striatum; genes encoding factors that protect nigral neurons against ongoing degeneration, such as glial cell line-derived neurotrophic factor; and genes encoding p-roteins that produce the inhibitory transmitter γ-aminobutylic acid (GABA) in the subthalamic nucleus (STN), thus suppressing the hyperactive STN. Recombinant adeno-associated viral (rAAV) vectors, which are derived from non-pathogenic viruses, have been shown to be suitable for clinical trials. These rAAVs have been found to transduce substantial numbers of neurons efficiently and to express transgenes in mammalian brains for long periods of time, with m-inimum inflammatory and immunological responses. In vivo imaging using positron emission tomography is useful for monitoring transgene expression and for assessing the functional effects of gene del...

[Gene therapy for Parkinson's disease].

Abstract: Clinical studies of gene therapy for Parkinson's disease are based on three kinds of strategies. 1. Restoration of dopamine production in the putamen by introducing genes of dopamine-synthesizing enzymes. 2. Protection of nigrostriatal projections by gene transfer of neurotrophic factors into the putamen and substantia nigra. 3. Modulation of subthalamic nucleus neural activity by gene delivery of an enzyme to synthesize inhibitory transmitter y-aminobutyric acid. In all studies, procedures were well tolerated and no adverse effects attributed to viral vectors were reported. The beneficial effects of putaminal gene transfer on motor symptoms have also been confirmed in children with aromatic L-amino acid decarboxylase deficiency. For a neuroprotective strategy, early intervention is necessary before degeneration has proceeded too far.

[Gene therapy and cell transplantation for Parkinson's disease].

Abstract: Increasing enthusiasm in the field of stem cell research is raising the hope of novel cell replacement therapies for Parkinson's disease (PD), but it also raises both scientific and ethical concerns. In most cases, dopaminergic cells are transplanted ectopically into the striatum instead of the substantia nigra. If the main mechanism underlying any observed functional recovery with these cell replacement therapies is restoration of dopaminergic neurotransmission, then viral vector-mediated gene delivery of dopamine-synthesizing enzymes is a more straight forward approach. The development of a recombinant adeno-associated viral (AAV) vector is making gene therapy for PD a feasible therapeutic option in the clinical arena. Efficient and long-term expression of genes for dopamine-synthesizing enzymes in the striatum restored local dopamine production and allowed behavioral recovery in animal models of PD. A clinical trial to evaluate the safety and efficacy of AAV vector-mediated gene transfer of aromatic L-amino acid decarboxylase, an enzyme that converts L-dopa to dopamine, is underway. With this strategy patients would still need to take L-dopa to control their PD symptoms, however, dopamine production could be regulated by altering the dose of L-dopa. Another AAV vector-based clinical trial is also ongoing in which the subthalamic nucleus is transduced to produce inhibitory transmitters.