Anke A. Dijkstra

The proliferative capacity of the subventricular zone is maintained in the parkinsonian brain

There are many indications that neurogenesis is impaired in Parkinsons disease, which might be due to a lack of dopamine in the subventricular zone. An impairment in neurogenesis may have negative consequences for the development of new therapeutic approaches in Parkinsons disease, as neural stem cells are a potential source for endogenous repair. In this study, we examined the subventricular zone of 10 patients with Parkinsons disease and 10 age- and sex-matched controls for proliferation and neural stem cell numbers. We also included five cases with incidental Lewy body disease, which showed Parkinsons disease pathology but no clinical symptoms and thus did not receive dopaminergic treatment. We quantified the neural stem cell number and proliferative capacity in the subventricular zone of these three donor groups. We found subventricular neural stem cells in each donor, with a high variation in number. We did not observe significant differences in neural stem cell number or in proliferation between the groups. Additionally, we were able to culture neural stem cells from post-mortem brain of several patients with Parkinsons disease, confirming the presence of viable neural stem cells in these brains. We have also examined the subventricular zone of a chronic, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsons disease mouse model, and again found no effect of dopaminergic denervation on precursor proliferation. Lastly, we investigated the proliferation capacity of two different human neural stem cell lines in response to dopamine. Both cell lines did not respond with a change in proliferation to treatment with dopamine agonists and an antagonist. In summary, the adult neural stem cell pool in the subventricular zone was not clearly affected in the human parkinsonian brain or a Parkinsons disease mouse model. Furthermore, we did not find evidence that dopamine has a direct effect on human neural stem cell proliferation in vitro. Thus, we conclude that the number of adult neural stem cells is probably not diminished in the parkinsonian brain and that dopamine depletion most likely has no effect on human neural stem cells.

Stage‐dependent nigral neuronal loss in incidental Lewy body and Parkinson's disease

To gain a better understanding of the significance of α‐synuclein pathological conditions during disease progression in Parkinsons disease, we investigated whether 1) nigral neuronal loss in incidental Lewy body disease and Parkinsons disease donors is associated with the local burden α‐synuclein pathological conditions during progression of pathological conditions; 2) the burden and distribution of α‐synuclein pathological conditions are related to clinical measures of disease progression. Post‐mortem tissue and medical records of 24 Parkinsons disease patients, 20 incidental Lewy body disease donors, and 12 age‐matched controls were obtained from the Netherlands Brain Bank for morphometric analysis. We observed a 20% decrease in nigral neuronal cell density in incidental Lewy body disease compared with controls. Nigral neuronal loss (12%) was already observed before the appearance α‐synuclein aggregates. The progression from Braak α‐synuclein stage 3 to 4 was associated with a significant decline in neuronal cell density (46%). Nigral neuronal loss increased with later Braak α‐synuclein stages but did not vary across consecutive Braak α‐synuclein stages. We observed a negative correlation between neuronal density and local α‐synuclein burden in the substantia nigra of Parkinsons disease patients (ρ = −0.54), but no relationship with Hoehn & Yahr stage or disease duration. In conclusion, our findings cast doubt on the pathogenic role of α‐synuclein aggregates in elderly, but do suggest that the severity of neurodegeneration and local burden of α‐synuclein pathological conditions are closely coupled during disease progression in Parkinsons disease.

Patterns of alpha-synuclein pathology in incidental cases and clinical subtypes of Parkinson's disease

Parkinsons disease (PD) is characterized by a gradual accumulation of neuropathology that may begin many years before a clinical diagnosis can be made using currently accepted criteria. Here, we first review the prevalence of α-synuclein neuropathology in elderly and discuss its clinical relevance in Parkinson patients. Subsequently, the results of a retrospective study focussing on the distribution of neuropathology in Parkinson patients with a tremor-dominant (TD), non-tremordominant (NTD) or rapid disease progression (RDP) subtype are presented. The study population recruited by the Netherlands Brain bank consisted of 149 non-neurological donors, 26 donors with incidental Lewy body disease (iLBD) and 111 Parkinson patients. In total, 89% of these cases could be classified in accordance with the Braak staging when taking into account the severity of α-synuclein pathology and adding an amygdala-predominant category of synucleinopathy. The pathological progression seemed to be non-linear. Interestingly, a strong correlation between neuronal loss and α-synuclein pathology was observed in the substantia nigra in Braak stages 3-6 (P < 0.01). However, there was no correlation between Hoehn & Yahr and Braak stages. Neuropathological progression may, however, vary between subtypes as cortical Lewy body load and Braak stages were higher in patients with NTD compared to TD and Alzheimer pathology was more prevalent in RDP patients. Recognition of clinical subtypes in neuropathological studies is essential to identify selective vulnerability to protein accumulation that may determine the clinical phenotype in PD.

Evidence for Immune Response, Axonal Dysfunction and Reduced Endocytosis in the Substantia Nigra in Early Stage Parkinson's Disease.

Subjects with incidental Lewy body disease (iLBD) may represent the premotor stage of Parkinson’s disease (PD). To elucidate molecular mechanisms underlying neuronal dysfunction and alpha-synuclein pathology in the premotor phase of PD, we investigated the transcriptome of the substantia nigra (SN) of well-characterized iLBD, PD donors and age-matched controls with Braak alpha-synuclein stage ranging from 0–6. In Braak alpha-synuclein stages 1 and 2, we observed deregulation of pathways linked to axonal degeneration, immune response and endocytosis, including axonal guidance signaling, mTOR signaling, EIF2 signaling and clathrin-mediated endocytosis in the SN. In Braak stages 3 and 4, we observed deregulation of pathways involved in protein translation and cell survival, including mTOR and EIF2 signaling. In Braak stages 5 and 6, we observed deregulation of dopaminergic signaling, axonal guidance signaling and thrombin signaling. Throughout the progression of PD pathology, we observed a deregulation of mTOR, EIF2 and regulation of eIF4 and p70S6K signaling in the SN. Our results indicate that molecular mechanisms related to axonal dysfunction, endocytosis and immune response are an early event in PD pathology, whereas mTOR and EIF2 signaling are impaired throughout disease progression. These pathways may hold the key to altering the disease progression in PD.

Evaluation of tracer kinetic models for analysis of [18F]FDDNP studies.

PurposeDifferent pharmacokinetic methods for [18F]FDDNP studies were evaluated using both simulations and clinical data.ProceduresMethods included two-tissue reversible plasma (2T4k), simplified reference tissue input (SRTM), and a modified 2T4k models. The latter included an additional compartment for metabolites (2T1M). For plasma input models, binding potential, BPND, was obtained both directly (=k3/k4) and indirectly (using volume of distribution ratios).ResultsFor clinical data, 2T1M was preferred over 2T4k according to Akaike criterion. Indirect BPND using 2T1M correlated better with SRTM then direct BPND. Fairly constant volume of distribution of metabolites was found across brain and across subjects, which was strongly related to bias in BPND obtained from SRTM as seen in simulations. Furthermore, in simulations, SRTM showed constant bias with best precision if metabolites entered brain.ConclusionsSRTM is the method of choice for quantitative analysis of [18F]FDDNP even if it is unclear whether labeled metabolites enter the brain.

UNFOLDED PROTEIN RESPONSE ACTIVATION IN C9ORF72 FRONTOTEMPORAL DEMENTIA CASES

P3-201 UNFOLDED PROTEIN RESPONSE ACTIVATION IN C9ORF72 FRONTOTEMPORAL DEMENTIA CASES Jeroen J. M. Hoozemans, Priya Gami, Irene van Dijken, Lieke H. H. Meeter, Shami Melhem, John C. van Swieten, Annemieke M. Rozemuller, Anke A. Dijkstra, VU University Medical Center, Amsterdam, Netherlands; Erasmus Medical Center, Rotterdam, Netherlands; Erasmus University Medical Center, Rotterdam, Netherlands; VU University Medical Center, Amsterdam Neuroscience, Amsterdam, Netherlands. Contact e-mail: JJM.Hoozemans@vumc.nl