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Abstract: Parkinson's disease (PD) is a prevalent neurodegenerative disorder characterized by a progressive and extensive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and their terminals in the striatum, which results in debilitating movement disorders. This devastating disease affects over 1million individuals in the United States and is increasing in incidence worldwide. Currently available pharmacological and surgical therapies ameliorate clinical symptoms in the early stages of disease, but they cannot stop or reverse degeneration of DA neurons. Stem cell therapies have come to the forefront of the PD research field as promising regenerative therapies. The majority of preclinical stem cell studies in experimental models of PD are focused on the idea that stem cell-derived DA neurons could be developed for replacement of diseased neurons. Alternatively, our studies and the studies from other groups suggest that stem cells also have the potential to protect and stimulate regeneration of compromised DA neurons. This review is focused on strategies based on the therapeutic potential for PD of the neurotrophic and neuroregenerative properties of a subclass of stem cells, mesenchymal stem cells (MSCs). [Copyright &y& Elsevier]

This is a commentary on the developmental and therapeutic relevance of recent studies in the glial fibrillary acid protein (GFAP)-glial cell line-derived neurotrophic factor (GDNF) transgenic mouse reported by Zhao et al. (2004). This interesting study demonstrated that increased expression of GDNF in astrocytes increases the number of neighboring motoneurons of certain motoneuron subpopulations by diminishing programmed cell death during development. In addition, astrocyte-derived GDNF was shown to protect facial motoneurons from injury-induced cell death. Since this is the first direct demonstration that secretion of GDNF from astrocytes in the CNS can affect motoneuron development in utero and motoneuron survival after axotomy, novel approaches for motor neuron disease are suggested. The known target neurons that respond to GDNF are reviewed, as are studies using GDNF gene delivery in animal models of amyotrophic lateral sclerosis (ALS). It is postulated that GDNF is a factor to which many motoneurons respond along their whole extent from soma to axon to terminal. [Copyright &y& Elsevier]

Abstract: Corticospinal motor neurons (CSMN) are the cortical component of motor neuron circuitry, which controls voluntary movement and degenerates in diseases such as amyotrophic lateral sclerosis, primary lateral sclerosis and hereditary spastic paraplegia. By using dual labeling combined with molecular marker analysis, we identified AAV2–2 mediated retrograde transduction as an effective approach to selectively target CSMN without affecting other neuron populations both in wild-type and hSOD1G93A transgenic ALS mice. This approach reveals very precise details of cytoarchitectural defects within vulnerable neurons in vivo. We report that CSMN vulnerability is marked by selective degeneration of apical dendrites especially in layer II/III of the hSOD1G93A mouse motor cortex, where cortical input to CSMN function is vastly modulated. While our findings confirm the presence of astrogliosis and microglia activation, they do not lend support to their direct role for the initiation of CSMN vulnerability. This study enables development of targeted gene replacement strategies to CSMN in the cerebral cortex, and reveals CSMN cortical modulation defects as a potential cause of neuronal vulnerability in ALS. [Copyright &y& Elsevier]

Abstract: Human α-synuclein overexpression and its toxic accumulation in neurons or glia are known to play key roles in the pathogenesis of Parkinson's disease and other related neurodegenerative synucleinopathies. Several single point mutations in the α-synuclein gene, as well as gene duplication and triplication, have been linked to familial Parkinson's disease. Moreover, genetic variability of the α-synuclein gene promoter is associated with idiopathic Parkinson''s disease. Silencing of the human α-synuclein gene by vector-based RNA interference (RNAi) is a promising therapeutic approach for synucleinopathies. Here, we report identification of a 21-nucleotide sequence in the coding region of human α-synuclein that constitutes an effective target for robust silencing by RNAi and demonstrate allele-specific silencing of the A53T mutant of human α-synuclein. Furthermore, we have developed a plasmid vector-based RNAi for silencing of human α-synuclein in vitro. Lastly, using a dual cassette lentivirus that co-expresses an α-synuclein-targeting small hairpin RNA (shRNA) and enhanced green fluorescent protein (EGFP) as a marker gene, we demonstrate effective silencing of endogenous human α-synuclein in vitro in the human dopaminergic cell line SH-SY5Y and also of experimentally expressed human α-synuclein in vivo in rat brain. Our results demonstrate potent silencing of human α-synuclein expression in vitro and in vivo by viral vector-based RNAi and provide the tools for developing effective gene silencing therapeutics for synucleinopathies, including Parkinson''s disease. [Copyright &y& Elsevier]

Abstract: Caspase-9 is a critical downstream effector molecule involved in apoptosis, a cell death process thought to be involved in the demise of dopamine (DA) neurons in the substantia nigra (SN) affected by Parkinson''s disease (PD). In this study, we determined that a tetracycline-regulated adenovirus harboring a dominant-negative form of caspase-9 (Casp9DN) and the marker gene, enhanced green fluorescent protein (EGFP), under the control of a bidirectional promoter could each be regulated in vitro and in vivo by doxycycline. We next observed that Casp9DN gene delivery significantly protected against TNFα and cycloheximide-induced chromatin condensation in HeLa cells and prevented chromatin condensation and the appearance of the early apoptotic marker annexin V in 6-hydroxydopamine (6-OHDA) treated MN9D cells, a dopaminergic cell line. Effects of Casp9DN on DA neurons in vivo were also assessed. DA neurons were retrogradely labeled with fluorogold (FG) and transduced with Casp9DN and EGFP or EGFP alone. A progressive lesion of DA neurons was induced by striatal injection of 6-OHDA 1 week later. At 2 weeks post-lesion, a morphometric analysis of FG+ neurons in the SN revealed that the mean cell diameter of FG labeled neurons in the Casp9DN group was 8% and 21% larger than the EGFP and PBS groups, respectively (P < 0.05). However, there was no difference among the treatment groups in the number of neurons remaining in the lesioned SN. These results suggest that while inhibiting apoptosis at the level of caspase-9 is protective in vitro, it is not protective against 6-OHDA-induced cell death in vivo. [Copyright &y& Elsevier]