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Progressive neurodegeneration or endogenous compensation in an animal model of Parkinson's disease produced by decreasing doses of alpha-synuclein.

Koprich JB, Johnston TH, Huot P, Reyes MG, Espinosa M, Brotchie JM - PLoS ONE (2011)

Bottom Line: By 6 weeks greater evidence of pathology was observed and included, reductions in SN DA neurons, striatal DA, TH and DA-transporter, along with a sustained behavioural deficit.In contrast, the 1:10 AAV1/2 A53T α-syn treated animals showed normalization between 3 and 6 weeks in paw use asymmetry, reductions in striatal TH, and increased DA turnover.Furthermore, these data highlight the need to characterize the titer of vector being utilized, when using AAV to express pathogenic proteins and model disease process, to avoid producing non-specific effects.

View Article: PubMed Central - PubMed

Affiliation: Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada. jkoprich@uhnres.utoronto.ca

ABSTRACT
The pathological hallmarks of Parkinson's disease (PD) are degeneration of dopamine (DA) neurons of the substantia nigra (SN) and the presence of alpha-synuclein (α-syn)-rich Lewy bodies in DA cells that remain. To model these aspects of the disease, we previously showed that high titer (5.1×10exp12 gp/ml) AAV1/2 driven expression of A53T α-syn in the SN of rats caused nigrostriatal pathology including a loss of DA neurons, but also with toxicity in the GFP control group. In the current study, we evaluate the effects of two lower titers by dilution of the vector (1∶3 [1.7×10exp12] and 1∶10 [5.1×10exp11]) to define a concentration that produced pathology specific for α-syn. In GFP and empty vector groups there were no behavioural or post-mortem changes at 3 or 6 weeks post-administration at either vector dose. Dilution of the AAV1/2 A53T α-syn (1:3) produced significant paw use asymmetry, reductions in striatal tyrosine hydroxylase (TH), and increases in DA turnover at 3 weeks in the absence of overt pathology. By 6 weeks greater evidence of pathology was observed and included, reductions in SN DA neurons, striatal DA, TH and DA-transporter, along with a sustained behavioural deficit. In contrast, the 1:10 AAV1/2 A53T α-syn treated animals showed normalization between 3 and 6 weeks in paw use asymmetry, reductions in striatal TH, and increased DA turnover. Progression of dopaminergic deficits using the 1:3 titer of AAV1/2 A53Tα-syn provides a platform for evaluating treatments directed at preventing and/or reversing synucleinopathy. Use of the 1:10 titer of AAV1/2 A53T α-syn provides an opportunity to study mechanisms of endogenous compensation. Furthermore, these data highlight the need to characterize the titer of vector being utilized, when using AAV to express pathogenic proteins and model disease process, to avoid producing non-specific effects.

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Dopamine neuron loss in the substantia nigra.Stereological counting of TH-ir neurons in the substantia nigra (SN) showed that AAV1/2 A53T α-synuclein (1∶3, 1.7×1012 gp/ml) reduces the number of dopamine neurons 6 weeks following intra-nigral injection, while quantification at 3 weeks or when using the 1∶10 dilution (5.1×1011 gp/ml) at either timepoint, showed no evidence of neuron loss. Panels A, B and C represent significant comparisons found in the AAV1/2 [1∶3] graphs. Scale bar in panel A is 1000 µm. * P<0.05 c.f. empty vector.
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pone-0017698-g003: Dopamine neuron loss in the substantia nigra.Stereological counting of TH-ir neurons in the substantia nigra (SN) showed that AAV1/2 A53T α-synuclein (1∶3, 1.7×1012 gp/ml) reduces the number of dopamine neurons 6 weeks following intra-nigral injection, while quantification at 3 weeks or when using the 1∶10 dilution (5.1×1011 gp/ml) at either timepoint, showed no evidence of neuron loss. Panels A, B and C represent significant comparisons found in the AAV1/2 [1∶3] graphs. Scale bar in panel A is 1000 µm. * P<0.05 c.f. empty vector.

Mentions: Three weeks following delivery of vectors coding for GFP, or α-syn and an empty vector, no difference in the number of TH-immunoreactive (ir) cells in the SN was evident (P>0.05). In contrast, at the 6 week timepoint, there was a significant difference in the number of TH-ir cells in the SN when compared across all three groups in the 1∶3 condition (Figure 3A–C) (F2,14 = 4.37, P<0.05). Post-hoc analysis revealed that animals that received the 1∶3 AAV1/2 A53T α-syn showed a significant decrease (by 28%) in TH-ir cells compared to EV controls (P<0.05) and no significant difference to GFP controls (P>0.05). There were no significant differences among conditions in the 1∶10 dilution at the 6 week timepoint (P>0.05). See Figure 3.


Progressive neurodegeneration or endogenous compensation in an animal model of Parkinson's disease produced by decreasing doses of alpha-synuclein.

Koprich JB, Johnston TH, Huot P, Reyes MG, Espinosa M, Brotchie JM - PLoS ONE (2011)

Dopamine neuron loss in the substantia nigra.Stereological counting of TH-ir neurons in the substantia nigra (SN) showed that AAV1/2 A53T α-synuclein (1∶3, 1.7×1012 gp/ml) reduces the number of dopamine neurons 6 weeks following intra-nigral injection, while quantification at 3 weeks or when using the 1∶10 dilution (5.1×1011 gp/ml) at either timepoint, showed no evidence of neuron loss. Panels A, B and C represent significant comparisons found in the AAV1/2 [1∶3] graphs. Scale bar in panel A is 1000 µm. * P<0.05 c.f. empty vector.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3049796&req=5

pone-0017698-g003: Dopamine neuron loss in the substantia nigra.Stereological counting of TH-ir neurons in the substantia nigra (SN) showed that AAV1/2 A53T α-synuclein (1∶3, 1.7×1012 gp/ml) reduces the number of dopamine neurons 6 weeks following intra-nigral injection, while quantification at 3 weeks or when using the 1∶10 dilution (5.1×1011 gp/ml) at either timepoint, showed no evidence of neuron loss. Panels A, B and C represent significant comparisons found in the AAV1/2 [1∶3] graphs. Scale bar in panel A is 1000 µm. * P<0.05 c.f. empty vector.
Mentions: Three weeks following delivery of vectors coding for GFP, or α-syn and an empty vector, no difference in the number of TH-immunoreactive (ir) cells in the SN was evident (P>0.05). In contrast, at the 6 week timepoint, there was a significant difference in the number of TH-ir cells in the SN when compared across all three groups in the 1∶3 condition (Figure 3A–C) (F2,14 = 4.37, P<0.05). Post-hoc analysis revealed that animals that received the 1∶3 AAV1/2 A53T α-syn showed a significant decrease (by 28%) in TH-ir cells compared to EV controls (P<0.05) and no significant difference to GFP controls (P>0.05). There were no significant differences among conditions in the 1∶10 dilution at the 6 week timepoint (P>0.05). See Figure 3.

Bottom Line: By 6 weeks greater evidence of pathology was observed and included, reductions in SN DA neurons, striatal DA, TH and DA-transporter, along with a sustained behavioural deficit.In contrast, the 1:10 AAV1/2 A53T α-syn treated animals showed normalization between 3 and 6 weeks in paw use asymmetry, reductions in striatal TH, and increased DA turnover.Furthermore, these data highlight the need to characterize the titer of vector being utilized, when using AAV to express pathogenic proteins and model disease process, to avoid producing non-specific effects.

View Article: PubMed Central - PubMed

Affiliation: Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada. jkoprich@uhnres.utoronto.ca

ABSTRACT
The pathological hallmarks of Parkinson's disease (PD) are degeneration of dopamine (DA) neurons of the substantia nigra (SN) and the presence of alpha-synuclein (α-syn)-rich Lewy bodies in DA cells that remain. To model these aspects of the disease, we previously showed that high titer (5.1×10exp12 gp/ml) AAV1/2 driven expression of A53T α-syn in the SN of rats caused nigrostriatal pathology including a loss of DA neurons, but also with toxicity in the GFP control group. In the current study, we evaluate the effects of two lower titers by dilution of the vector (1∶3 [1.7×10exp12] and 1∶10 [5.1×10exp11]) to define a concentration that produced pathology specific for α-syn. In GFP and empty vector groups there were no behavioural or post-mortem changes at 3 or 6 weeks post-administration at either vector dose. Dilution of the AAV1/2 A53T α-syn (1:3) produced significant paw use asymmetry, reductions in striatal tyrosine hydroxylase (TH), and increases in DA turnover at 3 weeks in the absence of overt pathology. By 6 weeks greater evidence of pathology was observed and included, reductions in SN DA neurons, striatal DA, TH and DA-transporter, along with a sustained behavioural deficit. In contrast, the 1:10 AAV1/2 A53T α-syn treated animals showed normalization between 3 and 6 weeks in paw use asymmetry, reductions in striatal TH, and increased DA turnover. Progression of dopaminergic deficits using the 1:3 titer of AAV1/2 A53Tα-syn provides a platform for evaluating treatments directed at preventing and/or reversing synucleinopathy. Use of the 1:10 titer of AAV1/2 A53T α-syn provides an opportunity to study mechanisms of endogenous compensation. Furthermore, these data highlight the need to characterize the titer of vector being utilized, when using AAV to express pathogenic proteins and model disease process, to avoid producing non-specific effects.

Show MeSH
Related in: MedlinePlus