Gene delivery to the nervous system

Challenges and progress of neurodrug: bioactivities, production and delivery strategies of nerve growth factor protein

Nerve growth factor (NGF) is a vital cytokine that plays a crucial role in the development and regeneration of the nervous system. It has been extensively studied for its potential therapeutic applications in various neural diseases. However, as a protein drug, limited natural source seriously hinders its translation and clinical applications. Conventional extraction of NGF from mouse submandibular glands has a very high cost and potentially induces immunogenicity; total synthesis and semi-synthesis methods are alternatives, but have difficulty in obtaining correct protein structure; gene engineering of plant cells is thought to be non-immunogenic, bioactive and economical. Meanwhile, large molecular weight, high polarity, and negative electrical charge make it difficult for NGF to cross the blood brain barrier to reach therapeutic targets. Current delivery strategies mainly depend on the adenovirus and cell biodelivery, but the safety and efficacy remain to be improved. New materials are widely investigated for the controllable, safe and precise delivery of NGF. This review illustrates physiological and therapeutic effects of NGF for various diseases. Moreover, new progress in production and delivery technologies for NGF are summarized. Bottlenecks encountered in the development of NGF as therapeutics are also discussed with the countermeasures proposed.

The mRVG-9R peptide as a potential therapeutic vector to the central nervous system cells

Our research group has developed a cell-penetrating peptide-based delivery system that includes the Asn194Lys mutation in the rabies virus glycoprotein-9R peptide (mRVG-9R). This system has the capacity to deliver DNA in astrocytes and SH-SY5Y cells. The aim of this study was to evaluate the ability of the mRVG-9R peptide to deliver DNA molecules to murine brain cells. The mRVG-9R peptide, a karyophilic peptide (KP) and a plasmid encoding green fluorescent protein (GFP) were bound by electrostatic charges to form the mRVG-9R complex. mRVG-9R complex was injected into the cerebral cortex, striatum and hippocampus of C57BL/6 mice by stereotactic surgery. After 2, 4, and 20 days, the animals were sacrificed and their brains were prepared for quantitative reverse-transcription polymerase chain reaction and histological analysis. We detected the GFP expression in neurons and glial cells in the cerebral cortex, striatum, and hippocampus of the murine brain. The results suggest that the mRVG-9R peptide has the ability to deliver DNA molecules to murine brain cells. Also, the expression of the reporter gene is maintained at least up to 20 days after injection in neurons, astrocytes, oligodendrocytes, and microglia cells. Thus, the in vivo transfection ability of the mRVG-9R peptide, makes it a promising candidate as a therapeutic gene delivery vector to the central nervous system cells.

Asn194Lys mutation in RVG29 peptide increases GFP transgene delivery by endocytosis to neuroblastoma and astrocyte cells

OBJECTIVES

A cell-penetrating peptide-based delivery system could target specific types of cells for therapeutic genes delivery. To increase the gene delivery efficiency into neuronal phenotype cells, we introduced an Asn194Lys mutation to RVG29 peptide derived from rabies virus glycoprotein and added a nuclear localization signal to enhance its nuclear import.

METHODS

Mutant RVG or wild-type RVG peptide, a karyophilic peptide (KP) and a plasmid encoding green fluorescent protein (pGL) were bound by electrostatic charges to form four different kinds of RVG complexes. Immunofluorescence was used to assess the gene transfection efficiency into astrocytes, oligodendrocyte precursor cells (OPCs), SH-SY5Y, HeLa and NIH/3T3 cells. The cellular uptake mechanism of RVG29 complexes was examined using endocytosis inhibitors.

KEY FINDINGS

The mRVG29 peptide has the ability to enhance the nuclear import of plasmids. The Asn194Lys mutation in RVG29 peptide of the pGL-mRVG29 complex and the addition of KP to the pGL-RVG29-KP complex increased the capacity to deliver DNA by endocytosis in astrocytes and SH-SY5Y cells.

CONCLUSIONS

The complexes pGL-mRVG29 and pGL-RVG29-KP have specificity for transfecting astrocytes and SH-SY5Y cells. The karyophilic capacity of this new mRVG peptide render it promising candidate to act as gene delivery vector into the brain cells.

Gene therapy and respiratory neuroplasticity

Breathing is a life-sustaining behavior that in mammals is accomplished by activation of dedicated muscles responsible for inspiratory and expiratory forces acting on the lung and chest wall. Motor control is exerted by specialized pools of motoneurons in the medulla and spinal cord innervated by projections from multiple centers primarily in the brainstem that act in concert to generate both the rhythm and pattern of ventilation. Perturbations that prevent the accomplishment of the full range of motor behaviors by respiratory muscles commonly result in significant morbidity and increased mortality. Recent developments in gene therapy and novel targeting strategies have contributed to deeper understanding of the organization of respiratory motor systems. Gene therapy has received widespread attention and substantial progress has been made in recent years with the advent of improved tools for vector design. Genes can be delivered via a variety of plasmids, synthetic or viral vectors and cell therapies. In recent years, adeno-associated viruses (AAV) have become one of the most commonly used vector systems, primarily because of the extensive characterization conducted to date and the versatility in targeting strategies. Recent studies highlight the power of using AAV to selectively and effectively transduce respiratory motoneurons and muscle fibers with promising therapeutic effects. This brief review summarizes current evidence for the use of gene therapy in respiratory disorders with a primary focus on interventions that address motor control and neuroplasticity, including regeneration, in the respiratory system.

Translational neurophysiology in sheep: measuring sleep and neurological dysfunction in CLN5 Batten disease affected sheep

Creating valid mouse models of slowly progressing human neurological diseases is challenging, not least because the short lifespan of rodents confounds realistic modelling of disease time course. With their large brains and long lives, sheep offer significant advantages for translational studies of human disease. Here we used normal and CLN5 Batten disease affected sheep to demonstrate the use of the species for studying neurological function in a model of human disease. We show that electroencephalography can be used in sheep, and that longitudinal recordings spanning many months are possible. This is the first time such an electroencephalography study has been performed in sheep. We characterized sleep in sheep, quantifying characteristic vigilance states and neurophysiological hallmarks such as sleep spindles. Mild sleep abnormalities and abnormal epileptiform waveforms were found in the electroencephalographies of Batten disease affected sheep. These abnormalities resemble the epileptiform activity seen in children with Batten disease and demonstrate the translational relevance of both the technique and the model. Given that both spontaneous and engineered sheep models of human neurodegenerative diseases already exist, sheep constitute a powerful species in which longitudinal in vivo studies can be conducted. This will advance our understanding of normal brain function and improve our capacity for translational research into neurological disorders.

Region-specific genetic alterations in the aging hippocampus: implications for cognitive aging

Aging is associated with cognitive decline in both humans and animals and of all brain regions, the hippocampus appears to be particularly vulnerable to senescence. Age-related spatial learning deficits result from alterations in hippocampal connectivity and plasticity. These changes are differentially expressed in each of the hippocampal fields known as cornu ammonis 1 (CA1), cornu ammonis 3 (CA3), and the dentate gyrus. Each sub-region displays varying degrees of susceptibility to aging. For example, the CA1 region is particularly susceptible in Alzheimer's disease while the CA3 region shows vulnerability to stress and glucocorticoids. Further, in animals, aging is the main factor associated with the decline in adult neurogenesis in the dentate gyrus. This review discusses the relationship between region-specific hippocampal connectivity, morphology, and gene expression alterations and the cognitive deficits associated with senescence. In particular, data are reviewed that illustrate how the molecular changes observed in the CA1, CA3, and dentate regions are associated with age-related learning deficits. This topic is of importance because increased understanding of how gene expression patterns reflect individual differences in cognitive performance is critical to the process of identifying new and clinically useful biomarkers for cognitive aging.

Gene-based approaches in the study of pathological pain

Chronic pathological pain is characterized by extensive plasticity of the systems involved in pain signal transmission and modulation and tissue remodeling in several CNS structures. These long-lasting alterations are mediated by, or associated with, changes in the production of key molecules of nociceptive processing. Gene-based approaches offer the unique possibility of using local or even cell-type specific interventions to correct the abnormal production of some of these proteins, modulate the activity of signal transduction pathways, or overproduce various therapeutic secreted proteins. We showed that certain viral-derived vectors are particularly suitable for mediating gene transfer highly preferential for instance into the primary sensory neurons or into the spinal cord glial cells that represent particularly pertinent targets in the search for new therapeutic strategies of pathological pain.

Role of the H1 haplotype of microtubule-associated protein tau (MAPT) gene in Greek patients with Parkinson's disease

Background

The extended tau haplotype (H1) that covers the entire human microtubule-associated protein tau (MAPT) gene has been implicated in Parkinson's disease (PD). Nevertheless, controversial results, such as two studies in Greek populations with opposite effects, have been reported. Therefore, we set out to determine whether the H1 haplotype and additional single nucleotide polymorphisms (SNPs) included in H1 are associated with PD in a sample of Greek patients.

Methods

We analysed MAPT haplotypes in cohorts of 122 patients and 123 controls of Greek origin, respectively. SNP genotyping was performed with Taqman assays and genotyping results were confirmed by sequencing.

Results

The presence of the H1 haplotype was significantly associated with PD (odds ratio for H1H1 vs. H1H2 and H2H2: 1.566; 95% CI: 1.137–2.157; P = 0.006) and remained so after adjustment for sex. Further analysis of H1 sub-haplotypes with three single nucleotide polymorphisms (rs242562, rs2435207 and rs3785883) demonstrated no significant association with PD.

Conclusion

Our data support the overall genetic role of MAPT and the H1 haplotype for PD susceptibility in Greek patients. However, the previously supported association of H1 sub-haplotypes with PD could not be confirmed in our study.

Lentiviral vectors for gene transfer into the spinal cord glial cells

Activated glial cells in the dorsal spinal cord participate in the development and maintenance of pain after peripheral nerve injury. Our understanding of mechanisms involved in functional changes of spinal glia remains incomplete. Excepting drugs that completely disrupt glial function, pharmacological studies fail to target glia and to modify locally its function to really discriminate the function of neuronal versus glial cells in chronic pain. Lentivirus-derived vectors fulfill several criteria that make them potentially interesting for this preferential targeting of glial cells in the spinal cord. We showed that in vivo single microdelivery of vesicular stomatitis virus G pseudotyped lentiviral vectors into the rat dorsal spinal cord led to a highly preferential expression of transgenes in astrocytes and microglial cells. This local and glia-targeted intervention allowed, for instance, the blockade of intracellular nuclear factor kappaB signaling pathway leading then to downregulation of the enhanced expression of several markers related to inflammation and pain, and, finally, to prolonged antihyperalgesic and antiallodynic effects. Targeted modulation of the expression of gene of interest in glial cells, closely restricted to a particular region of the spinal cord, may thus represent an interesting approach to refine the understanding of mechanisms by which spinal glial cells participate in pain processing.

Peptide-modified vectors for nucleic acid delivery to neurons

Neuron-targeted nucleic acid delivery systems are important technologies for realizing the potential of gene therapy for nervous system disorders. However, neurons are difficult cells to transfect using non-viral vectors due in part to the specific and unique delivery challenges present in these cells. We have investigated several bioactive peptides for their ability to assist in overcoming delivery barriers in mammalian cells. We summarize here our recent progress in developing and applying peptide-modified polycations for nucleic acid delivery. In addition, we present data demonstrating the potential of using multicomponent, peptide-modified polycations for nucleic acid delivery to neurons.