Gene therapy for neurodegenerative diseases: fact or fiction?

Self-Assembled Tetrahedral DNA Nanostructures Promote Neural Stem Cell Proliferation and Neuronal Differentiation

Stem cell-based therapy is considered a promising approach for the repair of nervous tissues. Neural stem cells (NSCs) cannot proliferate or differentiate efficiently; hence, different biomaterials have been explored to improve NSC proliferation and differentiation. However, these agents either had low bioavailability or poor biocompatibility. In this work, our group investigated the effects of tetrahedral DNA nanostructures (TDNs), a novel DNA biological material, on the self-renew and differentiation of neuroectodermal (NE-4C) stem cells. We observed that TDN treatment promoted self-renew of the stem cells via activating the Wnt/β -catenin pathway. In addition, our findings suggested that NE-4C stem cells' neuronal differentiation could be promoted effectively by TDNs via inhibiting the notch signaling pathway. In summary, this is the first report about the effects of TDNs on the proliferation and differentiation of NE-4C stem cells and the results demonstrate that TDNs have a great potential in nerve tissue regeneration.

Liver-Directed Adenoviral Gene Transfer in Murine Succinate Semialdehyde Dehydrogenase Deficiency

Murine succinate semialdehyde dehydrogenase (SSADH) deficiency (OMIM 271980; EC 1.2.1.24), a model of the corresponding human disorder, displays 100% mortality at weeks 3-4 of life, associated with lethal tonic-clonic seizures. The biochemical hallmark, gamma-hydroxybutyrate (GHB), accumulates in both human and murine disorders. In the current study we evaluated rescue of the murine model with liver-directed gene therapy using the E1-deleted adenoviral vector AD:pAD-RSV-humanSSADH. Our working hypotheses were: (1) liver expresses considerable SSADH activity and therefore represents a major source of GHB output, (2) correction of liver enzyme deficiency will reduce GHB load both peripherally and in the central nervous system, and (3) SSADH expression will improve survival. SSADH(-/-) and SSADH(+/+) mice were treated under two protocols: (A) intraperitoneal injection of 10(8)-10(11) viral particles by day 10 of life or (B) retro-orbital injection of 10(11) viral particles at day 13 of life. Intravenous administration was prohibited by the small size and fragility of the mice. Maximal survival (39%; P<0.001) was achieved with intraperitoneal administration (10(8) particles) at day 10; intraperitoneal (10(10) and 10(11) particles) and retro-orbital administration (10(11) particles) yielded lower survival of 11-25% (P<0.02). Under both protocols, the maximal hepatic SSADH enzyme activity was approximately 20% of SSADH(+/+) liver activity (retro-orbital > ip). At various time points postinjection, ip-treated animals (10(8) viral particles) demonstrated upward of 80% reduction in liver GHB concentrations, with little impact on brain or serum GHB levels except at 48-72 h posttreatment (approximately 50% reduction for both tissues). Accordingly, we harvested retro-orbitally treated animals at 72 h and observed significant reductions of 60-70% for GHB in liver, kidney, serum, and brain extracts. Histochemical analysis of liver from retro-orbitally treated mutants demonstrated substantial SSADH staining, but with variability both within tissues and between animals. Our studies provide proof-of-principle that liver-mediated gene therapy has efficacy in treating SSADH deficiency and that hepatic tissue contributes significantly to the pool of GHB within the CNS.

Amelioration of chronic neuropathic pain after partial nerve injury by adeno-associated viral (AAV) vector-mediated over-expression of BDNF in the rat spinal cord

Changing the levels of neurotrophins in the spinal cord micro-environment after nervous system injury has been proposed to recover normal function, such that behavioral response to peripheral stimuli does not lead to chronic pain. We have investigated the effects of recombinant adeno-associated viral (rAAV)-mediated over-expression of brain-derived neurotrophic factor (BDNF) in the spinal cord on chronic neuropathic pain after unilateral chronic constriction injury (CCI) of the sciatic nerve. The rAAV-BDNF vector was injected into the dorsal horn at the thirteenth thoracic spinal cord vertebra (L(1) level) 1 week after CCI. Allodynia and hyperalgesia induced by CCI in the hindpaws were permanently reversed, beginning 1 week after vector injection, compared with a similar injection of a control rAAV-GFP vector (green fluorescent protein) or saline. In situ hybridization for BDNF demonstrated that both dorsal and ventral lumbar spinal neurons contained an intense signal for BDNF mRNA, at 1 to 8 weeks after vector injection. There was no similar BDNF mRNA over-expression associated with either injections of saline or rAAV-GFP. These data suggest that chronic neuropathic pain is sensitive to early spinal BDNF levels after partial nerve injury and that rAAV-mediated gene transfer could potentially be used to reverse chronic pain after nervous system injuries in humans.

Thinking preventively about dementia: a review

BACKGROUND

The dementias of late life now constitute a major public health challenge to our society.

OBJECTIVE

To examine the contributions of neuroscience, clinical treatment and health-care policy to the building of a national programme for preventive approaches to dementia.

METHOD

Critical review of the literature, making use of international databases (Medline, Embase, Psychlit) and British official publications.

RESULTS

Recent developments in a number of research fields afford prospects for advances in primary and secondary prevention. These include findings from case-control and cohort studies of associations with earlier head injury and vascular disease, possibilities of pharmacological protection for persons at high risk for Alzheimer's disease, and the use of more effective anti-dementia drugs in the mild to moderate stages of severity. Research aimed at tertiary prevention is lagging behind, but there are some indications that the worst features of late-stage decline could already be mitigated by improvements in community support services and nursing-home care.

CONCLUSIONS

Containment of the growing social and economic burdens of dementia calls for a national policy to ensure that new research findings can be translated into practice and applied to the benefit of all old people who stand in need. For this purpose the most appropriate conceptual framework is supplied by a preventive model, broadly similar to those already developed for some other forms of chronic degenerative disease.