Striatal Pleiotrophin Overexpression Provides Functional and Morphological Neuroprotection in the 6-Hydroxydopamine Model

Abstract

Neurotrophic factors are integrally involved in the development of the nigrostriatal system and in combination with gene therapy, possess great therapeutic potential for Parkinson's disease (PD). Pleiotrophin (PTN) is involved in the development, maintenance, and repair of the nigrostriatal dopamine (DA) system. The present study examined the ability of striatal PTN overexpression, delivered via psueudotyped recombinant adeno-associated virus type 2/1 (rAAV2/1), to provide neuroprotection and functional restoration from 6-hydroxydopamine (6-OHDA). Striatal PTN overexpression led to significant neuroprotection of tyrosine hydroxylase immunoreactive (THir) neurons in the substantia nigra pars compacta (SNpc) and THir neurite density in the striatum, with long-term PTN overexpression producing recovery from 6-OHDA-induced deficits in contralateral forelimb use. Transduced striatal PTN levels were increased threefold compared to adult striatal PTN expression and approximated peak endogenous developmental levels (P1). rAAV2/1 vector exclusively transduced neurons within the striatum and SNpc with approximately half the total striatal volume routinely transduced using our injection parameters. Our results indicate that striatal PTN overexpression can provide neuroprotection for the 6-OHDA lesioned nigrostriatal system based upon morphological and functional measures and that striatal PTN levels similar in magnitude to those expressed in the striatum during development are sufficient to provide neuroprotection from Parkinsonian insult.

Pleiotrophin overexpression regulates amphetamine-induced reward and striatal dopaminergic denervation without changing the expression of dopamine D1 and D2 receptors: Implications for neuroinflammation

“…To evaluate the potential neuroprotective role of PTN against amphetamine-induced neurotoxicity, we have now studied the effects of this drug in the striatum of mice with transgenic overexpression of PTN in the brain. In support of this rationale, studies with parkinsonian toxins had previously shown that overexpression of PTN exerts neuroprotection in mouse models of PD (Gombash et al, 2012;. Unexpectedly, we found that amphetamine-induced loss of striatal TH and DAT contents is increased in PTN-Tg mice, suggesting that dopaminergic denervation caused by amphetamine is facilitated by PTN overexpression.…”

Recombinant adenoassociated virus 2/5-mediated gene transfer is reduced in the aged rat midbrain

“…rAAV2/5-mediated protein expression in young adult rats is not maximal until 1 month after injection (Gombash et al , 2012), and it is possible that the aged brain may require more time to achieve maximal GFP expression. Therefore, we utilized protein immunoblotting to more accurately quantify GFP protein levels at varying time points after rAAV2/5 GFP injection.…”

“…Quantification of TH immunoreactive (THir) neurons in the SN pars compacta (SNpc) or total number of GFP immunoreactive (GFPir) cells was completed as previously described (Gombash et al , 2012). Briefly, stereology was performed using a Nikon Eclipse 80i microscope (Nikon), StereoInvestigator software (Microbrightfield Bioscience, Williston, VT) and Retiga 4000R camera (Qimaging, Surrey, BC Canada).…”

“…Preclinical studies using viral vector-mediated gene transfer have been successful in ameliorating symptoms and rescuing nigral dopamine neuron loss in PD models (Emborg et al , 2009; Gash et al , 1996; Gasmi et al , 2007; Gombash et al , 2012; Herzog et al , 2008; Kordower et al , 2000), yet human clinical trials have not experienced similar success (Bartus et al , 2011; ClinicalTrials.gov, 2013; Marks et al , 2010; Stocchi and Olanow, 2013). This discrepancy may be, in part, attributable to the almost exclusive use of young adult animals in preclinical studies that fail to recapitulate the aged host brain environment typical of most PD patients.…”

Neuroprotective potential of pleiotrophin overexpression in the striatonigral pathway compared with overexpression in both the striatonigral and nigrostriatal pathways

“…14,15 We have previously demonstrated that intrastriatal recombinant AAV delivery to overexpress PTN before 6-hydroxydopamine (6-OHDA) is protective of both nigral neurons and terminals and can be functionally restorative; 16 however, neuroprotection was not complete. PTN transduction patterns following intrastriatal delivery indicated significant expression in the striatonigral direct pathway resulting in robust PTN immunoreactivity within terminals in the SN pars reticulata (SNpr), whereas transduction of SNpc DA neurons following intrastriatal vector injection was limited and only observed in unlesioned rats.…”