Targeting alpha-synuclein with a microRNA-embedded silencing vector in the rat substantia nigra: positive and negative effects.

BACKGROUND: Alpha-synuclein (SNCA) downregulation shows therapeutic potential for synucleinopathies, including Parkinson's disease (PD). Previously we showed that human (h)SNCA gene silencing using a short hairpin (sh)RNA in rat substantia nigra (SN) protects against a hSNCA-induced forelimb deficit, but not dopamine (DA) neuron loss. Furthermore, the shRNA increases cell death in vitro, but the same target sequence embedded in a microRNA30 transcript (mir30-hSNCA) does not. OBJECTIVE: Examine hSNCA gene silencing using mir30-hSNCA in vivo. METHODS: Rats were stereotaxically injected into one SN with adeno-associated virus serotype 2/8 (AAV)-hSNCA, AAV-hSNCA plus AAV-mir30-SNCA or AAV-hSNCA plus a control non-silencing mir30-embedded siRNA and DA neuron markers and associated behavior were examined. RESULTS: AAV2/8-mediated SN hSNCA expression induces a forelimb deficit and tyrosine hydroxylase-immunoreactive (TH-IR) neuron loss. hSNCA gene silencing using mir30-hSNCA protects against this forelimb deficit at 2 m and ameliorates TH-IR neuron loss. Striatal (ST) TH-IR fiber density and DA markers, assessed by western blot, are unaffected by AAV-hSNCA alone. Co-expression of either silencing vector reduces ST TH-IR fibers, panTH in SN and Ser40 phosphorylated TH in SN and ST, but does not affect vesicular monoamine transporter-2. However, hSNCA gene silencing promotes partial TH-IR fiber recovery by 2 m. Co-expression of either silencing vector also induces SN inflammation, although some recovery was observed by 2 m in hSNCA-silenced SN. CONCLUSION: hSNCA gene silencing with AAV-mir30-hSNCA has positive effects on forelimb behavior and SN DA neurons, which are compromised by inflammation and reduced TH expression, suggesting that AAV2/8-mir30-hSNCA-mediated gene silencing, although promising in vitro, is not a candidate for therapeutic translation for PD.

Hypothalamic IGF-I gene therapy prolongs estrous cyclicity and protects ovarian structure in middle-aged female rats.

There is substantial evidence that age-related ovarian failure in rats is preceded by abnormal responsiveness of the neuroendocrine axis to estrogen positive feedback. Because IGF-I seems to act as a permissive factor for proper GnRH neuronal response to estrogen positive feedback and considering that the hypothalamic content of IGF-I declines in middle-aged (M-A) rats, we assessed the effectiveness of long-term IGF-I gene therapy in the mediobasal hypothalamus (MBH) of M-A female rats to extend regular cyclicity and preserve ovarian structure. We used 3 groups of M-A rats: 1 group of intact animals and 2 groups injected, at 36.2 weeks of age, in the MBH with either a bicistronic recombinant adeno-associated virus (rAAV) harboring the genes for IGF-I and the red fluorescent protein DsRed2, or a control rAAV expressing only DsRed2. Daily vaginal smears were taken throughout the study, which ended at 49.5 weeks of age. We measured serum levels of reproductive hormones and assessed ovarian histology at the end of the study. Although most of the rats injected with the IGF-I rAAV had, on the average, well-preserved estrous cyclicity as well as a generally normal ovarian histology, the intact and control rAAV groups showed a high percentage of acyclic rats at the end of the study and ovaries with numerous enlarged cysts and scarce corpora lutea. Serum LH was higher and hyperprolactinemia lower in the treated animals. These results suggest that overexpression of IGF-I in the MBH prolongs normal ovarian function in M-A female rats.

Mesenchymal stem cells and neuroregeneration in Parkinson's disease.

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 1 million 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).

AAV2 mediated retrograde transduction of corticospinal motor neurons reveals initial and selective apical dendrite degeneration in ALS.

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 hSOD1(G93A) 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 hSOD1(G93A) 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.

An α-synuclein AAV gene silencing vector ameliorates a behavioral deficit in a rat model of Parkinson's disease, but displays toxicity in dopamine neurons.

Effects of silencing ectopically expressed hSNCA in rat substantia nigra (SN) were examined as a novel therapeutic approach to Parkinson's disease (PD). AAV-hSNCA with or without an AAV harboring a short-hairpin (sh)RNA targeting hSNCA or luciferase was injected into one SN. At 9weeks, hSNCA-expressing rats had reduced SN dopamine (DA) neurons and exhibited a forelimb deficit. AAV-shRNA-SNCA silenced hSNCA and protected against the forelimb deficit. However, AAV-shRNA-SNCA also led to DA neuron loss suggesting undesirable effects of chronic shRNA expression. Effects on nigrostriatal-projecting neurons were examined using a retrograde tract tracer. Loss of striatal-projecting DA neurons was evident in the vector injection site, whereas DA neurons outside this site were lost in hSNCA-expressing rats, but not in hSNCA-silenced rats. These observations suggest that high levels of shRNA-SNCA were toxic to DA neurons, while neighboring neurons exposed to lower levels were protected by hSNCA gene silencing. Also, data collected on DA levels suggest that neurons other than or in addition to nigrostriatal DA neurons contributed to protection of forelimb use. Our observations suggest that while hSNCA gene silencing in DA neurons holds promise as a novel PD therapy, further development of silencing technology is required.

A microRNA embedded AAV α-synuclein gene silencing vector for dopaminergic neurons.

Alpha-synuclein (SNCA), an abundantly expressed presynaptic protein, is implicated in Parkinson's disease (PD). Since over-expression of human SNCA (hSNCA) leads to death of dopaminergic (DA) neurons in human, rodent and fly brain, hSNCA gene silencing may reduce levels of toxic forms of SNCA and ameliorate degeneration of DA neurons in PD. To begin to develop a gene therapy for PD based on hSNCA gene silencing, two AAV gene silencing vectors were designed, and tested for efficiency and specificity of silencing, as well as toxicity in vitro. The same hSNCA silencing sequence (shRNA) was used in both vectors, but in one vector, the shRNA was embedded in a microRNA backbone and driven by a pol II promoter, and in the other the shRNA was not embedded in a microRNA and was driven by a pol III promoter. Both vectors silenced hSNCA to the same extent in 293T cells transfected with hSNCA. In DA PC12 cells, neither vector decreased expression of rat SNCA, tyrosine hydroxylase (TH), dopamine transporter (DAT) or the vesicular monoamine transporter (VMAT). However, the mir30 embedded vector was significantly less toxic to both PC12 and SH-SY5Y cells. Our in vitro data suggest that this miRNA-embedded silencing vector may be ideal for chronic in vivo SNCA gene silencing in DA neurons.

Glial cell line-derived neurotrophic factor-secreting genetically modified human bone marrow-derived mesenchymal stem cells promote recovery in a rat model of Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive degeneration of nigrostriatal dopaminergic (DA) neurons. The therapeutic potential of glial cell line-derived neurotrophic factor (GDNF), the most potent neurotrophic factor for DA neurons, has been demonstrated in many experimental models of PD. However, chronic delivery of GDNF to DA neurons in the brain remains an unmet challenge. Here, we report the effects of GDNF-releasing Notch-induced human bone marrow-derived mesenchymal stem cells (MSC) grafted into striatum of the 6-hydroxydopamine (6-OHDA) progressively lesioned rat model of PD. Human MSC, obtained from bone marrow aspirates of young, healthy adult volunteers, were transiently transfected with the intracellular domain of the Notch1 gene (NICD) to generate SB623 cells. SB623 cells expressing GDNF and/or humanized Renilla green fluorescent protein (hrGFP) following lentiviral transduction or nontransduced cells were stereotaxically placed into rat striatum 1 week after a unilateral partial 6-OHDA striatal lesion. At 4 weeks, rats that had received GDNF-transduced SB623 cells had significantly decreased amphetamine-induced rotation compared with control rats, although this effect was not observed in rats that received GFP-transduced or nontransduced SB623 cells. At 5 weeks, rejuvenated tyrosine hydroxylase-immunoreactive (TH-IR) fibers that appeared to be host DA axons were observed in and around grafts. This effect was more prominent in rats that received GDNF-secreting cells and was not observed in controls. These observations suggest that human bone-marrow derived MSC, genetically modified to secrete GDNF, hold potential as an allogeneic or autologous stem cell therapy for PD.

Glial cell line-derived neurotrophic factor (GDNF) gene delivery protects cortical neurons from dying following a traumatic brain injury.

PURPOSE: The therapeutic potential of glial cell line-derived neurotrophic factor (GDNF) gene delivery was examined in a rodent model of traumatic brain injury (TBI), the controlled cortical impact (CCI). METHODS: An adenoviral vector harboring human GDNF (AdGDNF) or green fluorescent protein (AdGFP) was injected unilaterally into the forelimb sensorimotor cortex (FL-SMC) of the rat one week prior to a unilateral CCI. Tests of forelimb function and asymmetry were administered for 2 weeks post-injury. At 2 weeks post-injury, animals were sacrificed and contusion size, neuronal survival, neurodegeneration, and virally-mediated GDNF and GFP protein expression were measured. RESULTS: Rats injected with AdGDNF had significantly smaller contusions, more surviving neurons, and less neurodegeneration than AdGFP injected and uninjected injured animals. GDNF gene delivery also resulted in significantly faster recovery of forelimb coordination and a smaller initial preference for the uninjured forelimb during exploration of the walls of a platform. However, overall recovery of symmetrical forelimb use was not achieved. CONCLUSIONS: The discrepancy between neural protection and behavioral recovery suggests that while GDNF gene delivery provided a high degree of protection of damaged cortical neurons in this model of TBI, it may not have fully protected their terminals and synaptic functioning, resulting in only mild protection against behavioral deficits.

Reversal of dopaminergic degeneration in a parkinsonian rat following micrografting of human bone marrow-derived neural progenitors.

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the selective loss of dopaminergic (DA) neurons in the midbrain. Various types of stem cells that have potential to differentiate into DA neurons are being investigated as cellular therapies for PD. Stem cells also secrete growth factors and therefore also may have therapeutic effects in promoting the health of diseased DA neurons in the PD brain. To address this possibility in an experimental model of PD, bone marrow-derived neuroprogenitor-like cells were generated from bone marrow procured from healthy human adult volunteers and their potential to elicit recovery of damaged DA axons was studied in a partial lesion rat model of PD. Following collection of bone marrow, mesenchymal stem cells (MSC) were isolated and then genetically modified to create SB623 cells by transient transfection with the intracellular domain of the Notch1 gene (NICD), a modification that upregulates expression of certain neuroprogenitor markers. Ten deposits of 0.5 microl of SB623 cell suspension adjusted from 6,000 to 21,000 cells/microl in PBS or PBS alone were stereotaxically placed in the striatum 1 week after the nigrostriatal projection had been partially lesioned in adult F344 rats by injection of 6-hydroxydopamine (6-OHDA) into the striatum. At 3 weeks, a small number of grafted SB623 cells survived in the lesioned striatum as visualized by expression of the human specific nuclear matrix protein (hNuMA). In rats that received SB623 cells, but not in control rats, dense tyrosine hydroxylase immunoreactive (TH-ir) fibers were observed around the grafts. These fibers appeared to be rejuvenated host DA axons because no TH-ir in soma of surviving SB623 cells or coexpression of TH and hNuMA-ir were observed. In addition, dense serotonin immunoreactive (5-HT-ir) fibers were observed around grafted SB623 cells and these fibers also appeared to be of the host origin. Also, in some SB623 grafted rats that were sacrificed within 2 h of dl-amphetamine injection, hot spots of c-Fos-positive nuclei that coincided with rejuvenated dense TH fibers around the grafted SB623 cells were observed, suggesting increased availability of DA in these locations. Our observations suggest that NICD-transfected MSC hold potential as a readily available autologous or allogenic cellular therapy for ameliorating the degeneration of DA and 5-HT neurons in PD patients.

Non-viral delivery of the gene for glial cell line-derived neurotrophic factor to mesenchymal stem cells in vitro via a collagen scaffold.

Recent advances in tissue engineering that combine an extracellular matrix-like scaffold with therapeutic molecules, cells, DNA encoding therapeutic proteins, or a combination of the three hold promise for treating defects in the brain resulting from a penetrating injury or tumor resection. The purpose of this study was to investigate a porous sponge-like collagen scaffold for non-viral delivery of a plasmid encoding for glial cell line-derived neurotrophic factor (pGDNF) to rat marrow stromal stem cells (also referred to as mesenchymal stem cells, MSCs). The effects of the following parameters on GDNF synthesis in the three-dimensional (3D) constructs were evaluated and compared with results in monolayer culture: initial plasmid load (2-50 microg pGDNF), ratio of a lipid transfection reagent to plasmid (5:10), culture environment during the transfection (static and dynamic), and cell density. The level of gene expression in the collagen scaffolds achieved therapeutic levels that had previously been found to support survival of dopaminergic and trigeminal neurons in vitro. For the highest loading of plasmid (50 microg), the level of GDNF protein remained six to seven times above the control level after 2 weeks, a significant difference. Cell density in the scaffold was of importance for an early increase in GDNF production, with accumulated GDNF being approximately 60% greater after 9 days of culture when scaffolds were initially seeded with 2 million rat MSCs compared to 500,000 cells. Application of orbital shaking during the 4 h of transfection had a positive effect on the production of GDNF on 3D constructs but not of the same magnitude as reported in monolayer studies. Overall, these results demonstrate that the combination of tissue engineering and non-viral transfection of MSCs for the over-expression of GDNF is a promising approach for the long-term production of GDNF and probably for neurotrophic factors in general.

The "perivascular pump" driven by arterial pulsation is a powerful mechanism for the distribution of therapeutic molecules within the brain.

We investigated the movement of interstitially infused macromolecules within the central nervous system (CNS) in rats with high and low blood pressure (BP)/heart rate and in rats euthanized immediately before infusion (no heart action). Adeno-associated virus 2 (AAV2), fluorescent liposomes, or bovine serum albumin was infused into rat striatum (six hemispheres per group) by convection-enhanced delivery (CED). After infusion, distribution volumes were evaluated. The rats with high BP/heart rate displayed a significantly larger distribution of the infused molecules within the injected site and more extensive transport of those molecules to the globus pallidus. This difference was particularly apparent for AAV2, for which a 16.5-fold greater distribution of viral capsids was observed in the rats with high BP/heart rate than in the rats with no heartbeat. Similar results were observed for liposomes, despite their larger diameter. The distribution of all infused molecules in all rats that had low or no blood flow was confined to the space around brain blood vessels. These findings show that fluid circulation within the CNS through the perivascular space is the primary mechanism by which viral particles and other therapeutic agents administered by CED are spread within the brain and that cardiac contractions power this process.

A tetracycline-regulated adenovirus encoding dominant-negative caspase-9 is regulated in rat brain and protects against neurotoxin-induced cell death in vitro, but not in vivo.

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 TNFalpha 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.