• Diptaman Chatterjee, Daniel Saiz Sanchez, Emmanuel Quansah, Nolwen L Rey, Sonia George, Katelyn Becker, Zachary Madaj, Jennifer A Steiner, Jiyan Ma, Martha L Escobar Galvis, Jeffrey H Kordower, and Patrik Brundin.
• Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, USA.
• J Parkinsons Dis. 2019 Jan 1; 9 (2): 315-326.

BackgroundParkinson's disease (PD) is a synucleinopathy that has multiple neuropathological characteristics, with nigrostriatal dopamine system degeneration being a core feature. Current models of PD pathology typically fail to recapitulate several attributes of the pathogenic process and neuropathology. We aimed to define the effects of combining a mouse model exhibiting multiple PD-like changes with intrastriatal injections of α-synuclein (α-syn) pre-formed fibril (PFFs) aggregates. We employed the heterozygous Engrailed 1 (En1+/-) mouse that features several pathophysiological hallmarks of clinical PD.ObjectiveTo test the hypothesis that the neuropathological changes in the En1+/- mice will promote formation of α-syn aggregates following intrastriatal injections of pathogenic human α-syn PFFs.MethodsWe unilaterally injected PFFs into the striata of 1-month-old En1+/- and control wild-type mice and euthanized animals at 3 months for post-mortem analysis.ResultsUsing immunohistochemistry and unbiased stereology, we established that PFF-injected En1+/- mice exhibited a near-threefold increase in pS129-α-syn-positive neurons in the substantia nigra compared to PFF-injected wild-type mice. The PFF-injected En1+/- mice also displayed significant increases in pS129-α-syn-positive neurons in the amygdala and ventral tegmental area; regions of known PD pathology with projections to the striatum. Additionally, we observed amplified pS129-α-syn-positive aggregation in En1+/- mice in multiple cortical regions.ConclusionsFollowing intrastriatal injection of PFFs, absence of an En1 allele leads to additional aggregation of pathological α-syn, potentially due to En1-loss mediated nigrostriatal impairment. We propose that further development of this double-hit model could result in a PD mouse model that predicts which experimental therapies will be effective in PD.

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