Assessing Human Embryonic Stem Cell-Derived Dopaminergic Neuron Progenitor Transplants Using Non-invasive Imaging Techniques

PURPOSE

Human pluripotent stem cell (hPSC)-derived dopaminergic neuron progenitor cells (DAPCs) are a potential therapy for Parkinson's disease (PD). However, their intracranial administration raises safety concerns including uncontrolled proliferation, migration and inflammation. Here, we apply a bimodal imaging approach to investigate the fate of DAPC transplants in the rat striatum.

PROCEDURES

DAPCs co-expressing luciferase and ZsGreen or labelled with micron-sized particles of iron oxide (MPIOs) were transplanted in the striatum of RNU rats (n = 6 per group). DAPCs were tracked in vivo using bioluminescence and magnetic resonance (MR) imaging modalities.

RESULTS

Transgene silencing in differentiating DAPCs accompanied with signal attenuation due to animal growth rendered the bioluminescence undetectable by week 2 post intrastriatal transplantation. However, MR imaging of MPIO-labelled DAPCs showed that transplanted cells remained at the site of injection for over 120 days. Post-mortem histological analysis of DAPC transplants demonstrated that labelling with either luciferase/ZsGreen or MPIOs did not affect the ability of cells to differentiate into mature dopaminergic neurons. Importantly, labelled cells did not elicit increased glial reactivity compared to non-labelled cells.

CONCLUSIONS

In summary, our findings support the transplantation of hPSC-derived DAPCs as a safe treatment for PD.

Early constipation predicts faster dementia onset in Parkinson's disease

Constipation is a common but not a universal feature in early PD, suggesting that gut involvement is heterogeneous and may be part of a distinct PD subtype with prognostic implications. We analysed data from the Parkinson's Incidence Cohorts Collaboration, composed of incident community-based cohorts of PD patients assessed longitudinally over 8 years. Constipation was assessed with the MDS-UPDRS constipation item or a comparable categorical scale. Primary PD outcomes of interest were dementia, postural instability and death. PD patients were stratified according to constipation severity at diagnosis: none (n = 313, 67.3%), minor (n = 97, 20.9%) and major (n = 55, 11.8%). Clinical progression to all three outcomes was more rapid in those with more severe constipation at baseline (Kaplan-Meier survival analysis). Cox regression analysis, adjusting for relevant confounders, confirmed a significant relationship between constipation severity and progression to dementia, but not postural instability or death. Early constipation may predict an accelerated progression of neurodegenerative pathology.

The sleep and circadian problems of Huntington's disease: when, why and their importance

Introduction

Mounting evidence supports the existence of an important feedforward cycle between sleep and neurodegeneration, wherein neurodegenerative diseases cause sleep and circadian abnormalities, which in turn exacerbate and accelerate neurodegeneration. If so, sleep therapies bear important potential to slow progression in these diseases.

Findings

This cycle is challenging to study, as its bidirectional nature renders cause difficult to disentangle from effect. Likewise, well-controlled intervention studies are often impractical in the setting of established neurodegenerative disease. It is this that makes understanding sleep and circadian abnormalities in Huntington’s disease (HD) important: as a monogenic fully penetrant neurodegenerative condition presenting in midlife, it provides a rare opportunity to study sleep and circadian abnormalities longitudinally, prior to and throughout disease manifestation, and in the absence of confounds rendered by age and comorbidities. It also provides potential to trial sleep therapies at a preclinical or early disease stage. Moreover, its monogenic nature facilitates the development of transgenic animal models through which to run parallel pre-clinical studies. HD, therefore, provides a key model condition through which to gain new insights into the sleep-neurodegeneration interface.

Conclusions

Here, we begin by summarising contemporary knowledge of sleep abnormalities in HD, and consider how well these parallel those of Alzheimer’s and Parkinson’s as more common neurodegenerative conditions. We then discuss what is currently known of the sleep-neurodegeneration cyclical relationship in HD. We conclude by outlining key directions of current and future investigation by which to advance the sleep-neurodegeneration field via studies in HD.

Altered subcortical emotional salience processing differentiates Parkinson's patients with and without psychotic symptoms

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Emotional salience processing differentiates PD patients with and without psychosis.

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Enhanced striatal, hippocampal and midbrain responses in PD patients with psychosis.

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Indication for ‘jumping to conclusions’ bias in the same PD patients with psychosis.

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Aberrant top-down and salience processing associated with PD psychosis.

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Similar deficits as proposed in ‘aberrant salience hypothesis’ of schizophrenia.

Objective

Current research does not provide a clear explanation for why some patients with Parkinson’s Disease (PD) develop psychotic symptoms. The ‘aberrant salience hypothesis’ of psychosis has been influential and proposes that dopaminergic dysregulation leads to inappropriate attribution of salience to irrelevant/non-informative stimuli, facilitating the formation of hallucinations and delusions. The aim of this study is to investigate whether non-motivational salience is altered in PD patients and possibly linked to the development of psychotic symptoms.

Methods

We investigated salience processing in 14 PD patients with psychotic symptoms, 23 PD patients without psychotic symptoms and 19 healthy controls. All patients were on dopaminergic medication for their PD. We examined emotional salience using a visual oddball fMRI paradigm that has been used to investigate early stages of schizophrenia spectrum psychosis, controlling for resting cerebral blood flow as assessed with arterial spin labelling fMRI.

Results

We found significant differences between patient groups in brain responses to emotional salience. PD patients with psychotic symptoms had enhanced brain responses in the striatum, dopaminergic midbrain, hippocampus and amygdala compared to patients without psychotic symptoms. PD patients with psychotic symptoms showed significant correlations between the levels of dopaminergic drugs they were taking and BOLD signalling, as well as psychotic symptom scores.

Conclusion

Our study suggests that enhanced signalling in the striatum, dopaminergic midbrain, the hippocampus and amygdala is associated with the development of psychotic symptoms in PD, in line with that proposed in the ‘aberrant salience hypothesis’ of psychosis in schizophrenia.

Progression of Neuropsychiatric Symptoms over Time in an Incident Parkinson's Disease Cohort (ICICLE-PD)

BACKGROUND

Cross-sectional studies have identified that the prevalence of neuropsychiatric symptoms (NPS) in Parkinson's disease (PD) ranges from 70-89%. However, there are few longitudinal studies determining the impact of NPS on quality of life (QoL) in PD patients and their caregivers. We seek to determine the progression of NPS in early PD.

METHODS

Newly diagnosed idiopathic PD cases (n = 212) and age-matched controls (n = 99) were recruited into a longitudinal study. NPS were assessed using the Neuropsychiatric Inventory with Caregiver Distress scale (NPI-D). Further neuropsychological and clinical assessments were completed by participants, with reassessment at 18 and 36 months. Linear mixed-effects modelling determined factors associated with NPI-D and QoL over 36 months.

RESULTS

Depression, anxiety, apathy and hallucinations were more frequent in PD than controls at all time points (p < 0.05). Higher motor severity at baseline was associated with worsening NPI-D scores over time (β = 0.1, p < 0.05), but not cognition. A higher NPI total score was associated with poorer QoL at any time point (β = 0.3, p < 0.001), but not changed in QoL scores.

CONCLUSION

NPS are significantly associated with poorer QoL, even in early PD. Screening for NPS from diagnosis may allow efficient delivery of better support and treatment to patients and their families.

Abnormalities of age-related T cell senescence in Parkinson's disease

BACKGROUND

A wealth of evidence implicates both central and peripheral immune changes as contributing to the pathogenesis of Parkinson's disease (PD). It is critical to better understand this aspect of PD given that it is a tractable target for disease-modifying therapy. Age-related changes are known to occur in the immune system (immunosenescence) and might be of particular relevance in PD given that its prevalence rises with increasing age. We therefore sought to investigate this with respect to T cell replicative senescence, a key immune component of human ageing.

METHODS

Peripheral blood mononuclear cells were extracted from blood samples from 41 patients with mild PD (Hoehn and Yahr stages 1-2, mean (SD) disease duration 4.3 (1.2) years) and 41 age- and gender-matched controls. Immunophenotyping was performed with flow cytometry using markers of T lymphocyte activation and senescence (CD3, CD4, CD8, HLA-DR, CD38, CD28, CCR7, CD45RA, CD57, CD31). Cytomegalovirus (CMV) serology was measured given its proposed relevance in driving T cell senescence.

RESULTS

Markers of replicative senescence in the CD8+ population were strikingly reduced in PD cases versus controls (reduced CD57 expression (p = 0.005), reduced percentage of 'late differentiated' CD57_loCD28_hi cells (p = 0.007) and 'TEMRA' cells (p = 0.042)), whilst expression of activation markers (CD28) was increased (p = 0.005). This was not driven by differences in CMV seropositivity. No significant changes were observed in the CD4 population.

CONCLUSIONS

This study demonstrates for the first time that the peripheral immune profile in PD is distinctly atypical for an older population, with a lack of the CD8+ T cell replicative senescence which characterises normal ageing. This suggests that 'abnormal' immune ageing may contribute to the development of PD, and markers of T cell senescence warrant further investigation as potential biomarkers in this condition.

A Comparative Study of Preparation Techniques for Improving the Viability of Striatal Grafts Using Vital Stains, in Vitro Cultures, and in Vivo Grafts

Cell suspension grafts from embryonic striatal primordia placed into the adult rat striatum survive well and are able to alleviate a number of behavioral deficits caused by excitotoxic lesions to this structure. However, neither the anatomical connectivity between the graft and host nor the functional recovery elicited by the grafts is completely restored. One way in which the survival and function of embryonic striatal grafts may be enhanced is by the improvement of techniques for the preparation of the cell suspension prior to implantation, an issue that has been addressed only to a limited extent. We have evaluated a number of parameters during the preparation procedure, looking at the effects on cell survival over the first 24 h from preparation using vital dyes and the numbers of surviving neurons in vitro, after 4 days in culture, in addition to graft survival and function in vivo. Factors influencing cell survival include the type of trypsinization procedure and the age of donor tissues used for suspension preparation. The presence of DNase has no effect on cell viability but aids the dissociation of the tissue to form single cells. These results have important implications for the use of embryonic striatal grafts in animal models of Huntington's disease, and in any future clinical application of this research.

Transplanted Human Neural Precursor Cells Migrate Widely but Show no Lesion-Specific Tropism in the 6-Hydroxydopamine Rat Model of Parkinson's Disease

Parkinson's disease (PD), while primarily associated with degeneration of nigrostriatal dopamine neurons, is now increasingly recognized to have more widespread cell loss and so the most effective cell replacement therapy should target all these neuronal losses. Neural precursor cells might be ideal in this regard as in certain circumstances they have been shown to migrate widely following transplantation into the CNS. The aim of this study was to investigate whether transplanted human expanded neural precursor cells (hENPs) could migrate to sites of established or evolving pathology in the adult brain using the 6-hydroxydopamine (6-OHDA) rat model of PD. hENPs were grafted into the striatum prior to, at the same time as, or after the animals received a 6-OHDA lesion to the medial forebrain bundle. The presence of donor cells was then assessed in a distant site of cell loss (substantia nigra) or sites where cell death would not be expected (frontal cortex and globus pallidus). Donor cells were found distant from the site of implantation but the migration of these hENPs was not significantly greater in the 6-OHDA-lesioned brain and the cells did not specifically target the site of cell loss in the substantia nigra. The temporal relationship of grafting relative to the lesion, and therefore dopaminergic cell death, did not affect the migration of hENPs nor their differentiation. We conclude that while transplanted hENPs are capable of migration away from the site of implantation, they show no specific tropism for sites of ongoing or established nigral dopaminergic cell loss in this lesion model. Therefore, the use of such cells to replace the range of neurons lost in PD is likely to require a deeper understanding of the migratory cues in the damaged adult brain and some manipulation of these cells prior to transplantation.

Effects of Surgical Anaesthesia on the Viability of Nigral Grafts in the Rat Striatum

Only a small proportion of dopamine neurons in nigral grafts typically survive transplantation into the adult striatum. Since many anaesthetics reduce blood flow and disturb a variety of brain metabolites, surgical anaesthesia may be one of the factors that compromise graft survival. Conversely, the lowered core body temperature induced by some anaesthetics might promote the survival of grafted cells by slowing their metabolism. In an initial screen, the widely-used surgical anaesthetic, equithesin, was found to reduce core temperature, mean arterial blood pressure, and to increase the partial pressure of oxygen in arterial blood without producing any significant alteration in arterial pH or the partial pressure of carbon dioxide. In the main experiment, rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal bundle received dopamine-rich embryonic nigral grafts injected into the deafferented neostriatum via previously implanted guide cannulae, which allowed comparison to be made of graft survival after transplantation into awake and in re-anaesthetised animals. There were no significant differences between groups in either the functional effects of the grafts to compensate amphetamine-induced rotation, or in the survival and growth of the grafts as measured in post mortem histology. We therefore conclude that anaesthesia per se is not a major contributory factor in the relatively poor survival of dopamine neurons following transplantation into the rat striatum.

A Comparative Study of Preparation Techniques for Improving the Viability of Nigral Grafts using Vital Stains, in Vitro Cultures, and in Vivo Grafts

The intracerebral transplantation of embryonic dopaminergic nigral neurons, although relatively successful, leads to a fairly low yield of surviving cells. Many factors may influence the viability of dopaminergic grafts and one of these is the preparation of the tissue prior to transplantation. We have investigated the effects of different steps during the preparation and storage of embryonic rat nigral cell suspensions on their subsequent survival at a variety of different time points using a combination of techniques and studies. For studies concerned with the first 24 h we employed vital stains, in the period covering the next 7 days we used in vitro cultures, and in the long term experiment we used in vivo grafts. The results suggest that nigral cell suspensions may remain sufficiently viable for grafting for much longer periods than previously reported. In addition a number of parameters which affect cell survival have been characterised, including the age of the embryonic donor tissue, the use of proteolytic enzymes and the trituration procedure used during the preparation of the suspension. The optimal preparation technique, therefore, uses E13-E14 embryos with the dissected ventral mesencephalon being incubated in purified 0.1% trypsin solutions for 60 min and triturated using a flame polished Pasteur pipette. This may have important implications in improving intracerebral transplantation for Parkinson's disease.

Neural Transplantation in Huntington's Disease: The NEST-UK Donor Tissue Microbiological Screening Program and Review of the Literature

Neural transplantation of human fetal tissue for Huntington's disease (HD) is now entering the clinical arena. The safety of the procedure has now been demonstrated in a number of studies, although the efficacy of such an approach is still being investigated. Stringent but practicable screening of the donor tissue for potential pathogens is an essential prerequisite for successful implementation of any novel transplant program that uses human fetal tissue. In this article we summarize the UK-NEST protocol for the screening of human fetal tissue being grafted to patients with mild to moderate HD. We describe the results of microbiological screening of 87 potential tissue donors in a pilot study, and of the first four donor–recipient patients included in the UK-NEST series. The rationale for the adoption and interpretation of the various tests is described and our methodology is compared with those previously used by other centers. This article therefore presents a comprehensive, logical yet pragmatic screening program that could be employed in any clinical studies that use human fetal tissue for neurotransplantation.

Survival of Nigral Grafts within the Striatum of Marmosets with 6-Ohda Lesions Depends Critically on Donor Embryo Age

The study examined the importance of embryonic donor age for the survival of nigral grafts in 6-OHDA–lesioned marmosets. The issue as to whether donor age is critical for the survival of nigral grafts in primates is controversial, because several early reports suggested that relatively old tissue could survive transplantation and produce functional benefits in monkeys, in contrast to the restrictive time dependence observed in rodents. Embryonic marmoset donors embryos of three different ages were employed: 1) E74 (Carnegie stage 18-19); 2) E83-84 (Carnegie stage 23+); 3) E92-93 (foetal period). The nigral neurons derived from the ventral mesencephalon in the two older donor age groups did not survive well when grafted to the striatum of adult marmosets with unilateral 6-OHDA lesions. Although a few tyrosine hydroxylase (TH+) neurons could be identified by immunohistochemistry at graft sites in all recipients in older donor age groups, the numbers of surviving neurons in these were small, on average typically less than 100 TH+ cells. These small grafts were not sufficient to affect amphetamine-induced rotation. In contrast, many more TH+ cells typically survived transplantation in the recipients; of graft tissue derived from the youngest donors and amphetamine-induced rotation was significantly reduced in this group alone. The time course and extent of the reduction in rotation was remarkably similar to that observed in previous marmoset nigral graft studies, confirming the utility of amphetamine-induced rotation as a sensitive and reliable indicator of nigral graft function in this species. Considering these results and other recent evidence from monkey to monkey, human to rat, and human to human graft studies, the survival of embryonic nigral tissues derived from primate donors transplanted into the striatum does appear to be critically dependent on the age of the donor tissue.

Cerebral glucose metabolism and cognition in newly diagnosed Parkinson's disease: ICICLE-PD study

OBJECTIVE

To assess reductions of cerebral glucose metabolism in Parkinson's disease (PD) with 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET), and their associations with cognitive decline.

METHODS

FDG-PET was performed on a cohort of 79 patients with newly diagnosed PD (mean disease duration 8 months) and 20 unrelated controls. PD participants were scanned while on their usual dopaminergic medication. Cognitive testing was performed at baseline, and after 18 months using the Cognitive Drug Research (CDR) and Cambridge Neuropsychological Test Automated Battery (CANTAB) computerised batteries, the Mini-Mental State Examination (MMSE), and the Montreal Cognitive Assessment (MoCA). We used statistical parametric mapping (SPM V.12) software to compare groups and investigate voxelwise correlations between FDG metabolism and cognitive score at baseline. Linear regression was used to evaluate how levels of cortical FDG metabolism were predictive of subsequent cognitive decline rated with the MMSE and MoCA.

RESULTS

PD participants showed reduced glucose metabolism in the occipital and inferior parietal lobes relative to controls. Low performance on memory-based tasks was associated with reduced FDG metabolism in posterior parietal and temporal regions, while attentional performance was associated with more frontal deficits. Baseline parietal to cerebellum FDG metabolism ratios predicted MMSE (β=0.38, p=0.001) and MoCA (β=0.3, p=0.002) at 18 months controlling for baseline score.

CONCLUSIONS

Reductions in cortical FDG metabolism were present in newly diagnosed PD, and correlated with performance on neuropsychological tests. A reduced baseline parietal metabolism is associated with risk of cognitive decline and may represent a potential biomarker for this state and the development of PD dementia.

Formation of hippocampal mHTT aggregates leads to impaired spatial memory, hippocampal activation and adult neurogenesis

Huntington's disease (HD) is a genetic neurodegenerative disorder characterized by a triad of motor, psychiatric and cognitive deficits with the latter classically attributed to disruption of fronto-striatal circuits. However, emerging evidence suggests that some of the cognitive deficits in HD may have their origin in other structures including the hippocampus. Hippocampal abnormalities have been reported in HD mouse models particularly in terms of performance on the Morris Water Maze. However, in these animals, it is difficult to be certain whether the spatial memory deficits are due to local pathology within this structure or their poor mobility and motivation. Thus, a better model of hippocampal dysfunction in HD is needed especially given that we have previously shown that patients with HD have hippocampal-related problems from the very earliest stages of disease. In this study, our aim was therefore to understand the cellular and behavioural consequences of local overexpression of mutant huntingtin (mHTT) in the hippocampus of adult mice. We found that a targeted injection of a lentivirus, encoding an N-terminal of mHTT with 82 CAG repeats, into the murine hippocampus led to the focal formation of mHTT aggregates, long-term spatial memory impairments with decreased neurogenesis and expression of the immediate early gene c-fos. This study has therefore shown for the first time that local expression of mHTT in the dentate gyrus has deleterious effects, including its neurogenic capacity, with functional behavioural consequences, which fits well with recent data on hippocampal deficits seen in patients with HD.

Motor associations of iron accumulation in deep grey matter nuclei in Parkinson's disease: a cross-sectional study of iron-related magnetic resonance imaging susceptibility

BACKGROUND AND PURPOSE

To determine whether iron deposition in deep brain nuclei assessed using high-pass filtered phase imaging plays a role in motor disease severity in Parkinson's disease (PD).

METHODS

Seventy patients with mild to moderate PD and 20 age- and gender-matched healthy volunteers (HVs) underwent susceptibility-weighted imaging on a 3 T magnetic resonance imaging scanner. Phase shifts (radians) in deep brain nuclei were derived from high-pass filtered phase images and compared between groups. Analysis of clinical laterality and correlations with motor severity (Unified Parkinson's Disease Rating Scale, Part III, UPDRS-III) were performed. Phase shifts (in radians) were compared between HVs and three PD subgroups divided according to UPDRS-III scores using analysis of covariance, adjusting for age and regional area.

RESULTS

Parkinson's disease patients had significantly (P < 0.001) higher radians than HVs bilaterally in the putamen, globus pallidus and substantia nigra (SN). The SN contralateral to the most affected side showed higher radians (P < 0.001) compared to the less affected side. SN radians positively correlated with UPDRS-III and bradykinesia-rigidity subscores, but not with tremor subscores. ancova followed by post hoc Bonferroni-adjusted pairwise comparisons revealed that SN radians were significantly greater in the PD subgroup with higher UPDRS-III scores compared to both lowest UPDRS-III PD and HV groups (P < 0.001).

CONCLUSIONS

Increased nigral iron accumulation in PD appears to be stratified according to disease motor severity and correlates with symptoms related to dopaminergic neurodegeneration. This semi-quantitative in vivo iron assessment could prove useful for objectively monitoring PD progression, especially in clinical trials concerning iron chelation therapies.

Olfaction in Parkin single and compound heterozygotes in a cohort of young onset Parkinson's disease patients

BACKGROUND

Parkin related Parkinson's disease (PD) is differentiated from idiopathic PD by absent or sparse Lewy bodies, and preserved olfaction. The significance of single Parkin mutations in the pathogenesis of PD is debated.

OBJECTIVES

To assess olfaction results according to Parkin mutation status. To compare the prevalence of Parkin single heterozygous mutations in patients diagnosed with PD to the rate in healthy controls in order to establish whether these single mutations could be a risk factor for developing PD.

METHODS

Parkin gene mutation testing was performed in young onset PD (diagnosed <50 years old) to identify three groups: Parkin homozygous or compound heterozygote mutation carriers, Parkin single heterozygote mutation carriers, and non-carriers of Parkin mutations. Olfaction was tested using the 40-item British version of the University of Pennsylvania smell identification test (UPSIT).

RESULTS

Of 344 young onset PD cases tested, 8 (2.3%) were Parkin compound heterozygotes and 13 (3.8%) were Parkin single heterozygotes. Olfaction results were available in 282 cases (eight compound heterozygotes, nine single heterozygotes, and 265 non-carriers). In Parkin compound heterozygotes, the median UPSIT score was 33, interquartile range (IQR) 28.5-36.5, which was significantly better than in single Parkin heterozygotes (median 19, IQR 18-28) and non-carriers (median score 22, IQR 16-28) (ANOVA P < 0.001). These differences persisted after adjusting for age, disease duration, gender, and smoking (P < 0.001). There was no significant difference in UPSIT scores between single heterozygotes and non-carriers (P = 0.90).

CONCLUSIONS

Patients with Parkin compound heterozygous mutations have relatively preserved olfaction compared to Parkin single heterozygotes and non-carriers. The prevalence of Parkin single heterozygosity is similar to the 3.7% rate reported in healthy controls.

Modelling the natural history of Huntington's disease progression

BACKGROUND

The lack of reliable biomarkers to track disease progression is a major problem in clinical research of chronic neurological disorders. Using Huntington's disease (HD) as an example, we describe a novel approach to model HD and show that the progression of a neurological disorder can be predicted for individual patients.

METHODS

Starting with an initial cohort of 343 patients with HD that we have followed since 1995, we used data from 68 patients that satisfied our filtering criteria to model disease progression, based on the Unified Huntington's Disease Rating Scale (UHDRS), a measure that is routinely used in HD clinics worldwide.

RESULTS

Our model was validated by: (A) extrapolating our equation to model the age of disease onset, (B) testing it on a second patient data set by loosening our filtering criteria, (C) cross-validating with a repeated random subsampling approach and (D) holdout validating with the latest clinical assessment data from the same cohort of patients. With UHDRS scores from the past four clinical visits (over a minimum span of 2 years), our model predicts disease progression of individual patients over the next 2 years with an accuracy of 89-91%. We have also provided evidence that patients with similar baseline clinical profiles can exhibit very different trajectories of disease progression.

CONCLUSIONS

This new model therefore has important implications for HD research, most obviously in the development of potential disease-modifying therapies. We believe that a similar approach can also be adapted to model disease progression in other chronic neurological disorders.

Dopaminergic manipulations and its effects on neurogenesis and motor function in a transgenic mouse model of Huntington's disease

Huntington's disease (HD) is an inherited neurodegenerative disorder that is classically defined by a triad of movement and cognitive and psychiatric abnormalities with a well-established pathology that affects the dopaminergic systems of the brain. This has classically been described in terms of an early loss of dopamine D2 receptors (D2R), although interestingly the treatments most effectively used to treat patients with HD block these same receptors. We therefore sought to examine the dopaminergic system in HD not only in terms of striatal function but also at extrastriatal sites especially the hippocampus, given that transgenic (Tg) mice also exhibit deficits in hippocampal-dependent cognitive tests and a reduction in adult hippocampal neurogenesis. We showed that there was an early reduction of D2R in both the striatum and dentate gyrus (DG) of the hippocampus in the R6/1 transgenic HD mouse ahead of any overt motor signs and before striatal neuronal loss. Despite downregulation of D2Rs in these sites, further reduction of the dopaminergic input to these sites by either medial forebrain bundle lesions or receptor blockade using sulpiride was able to improve both deficits in motor performance and adult hippocampal neurogenesis. In contrast, a reduction in dopaminergic innervation of the neurogenic niches resulted in impaired neurogenesis in healthy WT mice. This study therefore provides evidence that D2R blockade improves hippocampal and striatal deficits in HD mice although the underlying mechanism for this is unclear, and suggests that agents working within this network may have greater effects than previously thought.

Putative cortical dopamine levels affect cortical recruitment during planning

Planning, the decomposition of an ultimate goal into a number of sub-goals is critically dependent upon fronto-striatal dopamine (DA) levels. Here, we examined the extent to which the val158met polymorphism in the catechol O-methyltransferase (COMT) gene, which is thought to primarily alter cortical DA levels, affects performance and fronto-parietal activity during a planning task (Tower of London). COMT genotype was found to modulate activity in the left superior posterior parietal cortex (SPC) during planning, relative to subtracting, trials. Specifically, left SPC blood oxygenation level-dependent (BOLD) response was reduced in groups with putatively low or high cortical DA levels (COMT homozygotes) relative to those with intermediate cortical DA levels (COMT heterozygotes). These set of results are argued to occur either due to differences in neuronal processing in planning (and perhaps subtracting) caused by the COMT genotype and/or the cognitively heterogeneous nature of the TOL, which allows different cognitive strategies to be used whilst producing indistinguishable behavioural performance in healthy adults. The implications of this result for our understanding of COMT's effect on cognition in health and disease are discussed.

The effects of multidisciplinary rehabilitation in patients with early-to-middle-stage Huntington's disease: a pilot study

BACKGROUND AND PURPOSE

Despite advances in the understanding of Huntington's disease (HD), treatment remains symptomatic. Multidisciplinary rehabilitation, however, appears to impact disease progression. Here we show the feasibility, safety and efficacy of a 9-month multidisciplinary rehabilitation programme in a small cohort of patients with early-to-middle-stage HD.

METHODS

Twenty patients with HD were assigned to two groups, equally matched for cognitive and motor scores. One group received the intervention, whilst the other served as control. The Unified-Huntington's-Disease-Rating-Scale-Total-Motor-Score was the primary outcome measure. Neurocognitive/psychological tests, body composition, postural stability, strength and quality of life assessments were secondary outcome measures.

RESULTS

The intervention reduced motor and postural stability deterioration, with minor improvements in depression, cognition and quality of life. Significant gains were observed for fat-free mass and strength.

CONCLUSION

This pilot study suggests that a prolonged multidisciplinary rehabilitation programme in early-to-middle-stage HD is feasible, well-tolerated and associated with therapeutic benefit. Further explorative, larger studies are warranted.

Neuropeptide Y and its role in CNS disease and repair

Neuropeptide Y (NPY) is widely expressed throughout the CNS and exerts a number of important physiological functions as well as playing a role in pathological conditions such as obesity, anxiety, epilepsy, chronic pain and neurodegenerative disorders. In this review, we highlight some of the recent advances in our understanding of NPY biology and how this may help explain not only its role in health and disease, but also its possible use therapeutically.

Coping processes and health-related quality of life in Parkinson's disease

OBJECTIVE

This study investigated the predictive value of various coping processes for the psychological and disease specific aspects of health-related quality of life (HRQoL) in Parkinson's disease (PD).

METHOD

Cross-sectional study of 85 participants with PD using the Ways of Coping Questionnaire (WCQ), Depression, Anxiety, and Stress Scale (DASS-21), quality of life (PDQ-39), and socio-demographic and clinical variables.

RESULTS

Greater use of planful problem solving coping was found to be significantly associated with better HRQoL in relation to cognitive impairment, communication and bodily discomfort. In addition to greater disease duration, greater use of escape-avoidance coping processes were identified as significant predictors of poorer HRQoL outcomes in the domains of mood and emotional well-being.

CONCLUSION

Psychological interventions such as mindfulness training, aimed at reducing the use of escape-avoidance copying, may help to improve HRQoL in PD.

Mild cognitive impairment in Parkinson disease: a multicenter pooled analysis

BACKGROUND

In studies of mild cognitive impairment (MCI) in Parkinson disease (PD), patients without dementia have reported variable prevalences and profiles of MCI, likely to be due to methodologic differences between the studies.

OBJECTIVE

The objective of this study was to determine frequency and the profile of MCI in a large, multicenter cohort of well-defined patients with PD using a standardized analytic method and a common definition of MCI.

METHODS

A total of 1,346 patients with PD from 8 different cohorts were included. Standardized analysis of verbal memory, visuospatial, and attentional/executive abilities was performed. Subjects were classified as having MCI if their age- and education-corrected z score on one or more cognitive domains was at least 1.5 standard deviations below the mean of either control subjects or normative data.

RESULTS

A total of 25.8% of subjects (95% confidence interval [CI] 23.5-28.2) were classified as having MCI. Memory impairment was most common (13.3%; 11.6-15.3), followed by visuospatial (11.0%; 9.4-13.0) and attention/executive ability impairment (10.1%; 8.6-11.9). Regarding cognitive profiles, 11.3% (9.7-13.1) were classified as nonamnestic single-domain MCI, 8.9% (7.0-9.9) as amnestic single-domain, 4.8% (3.8-6.1) as amnestic multiple-domain, and 1.3% (0.9-2.1) as nonamnestic multiple-domain MCI. Having MCI was associated with older age at assessment and at disease onset, male gender, depression, more severe motor symptoms, and advanced disease stage.

CONCLUSIONS

MCI is common in patients with PD without dementia, affecting a range of cognitive domains, including memory, visual-spatial, and attention/executive abilities. Future studies of patients with PD with MCI need to determine risk factors for ongoing cognitive decline and assess interventions at a predementia stage.

Onset and progression of pathologic atrophy in Huntington disease: a longitudinal MR imaging study

BACKGROUND AND PURPOSE

Longitudinal MR imaging measures provide an opportunity to track progression in HD before the emergence of clinical symptoms. This may prove useful in assessing disease-modifying treatments. We investigated how caudate and global volumes change as HD progresses from premanifest to early disease.

MATERIALS AND METHODS

Forty HD gene-positive individuals and 19 controls underwent serial volumetric MR imaging (baseline, 12 and 27 months; 2 or 3 scans per person). At baseline, 3 patients with HD were premanifest but developed overt motor features during the study, and 37 had early HD. All had dates of motor onset recorded. Caudates, lateral ventricles, and TIVs were measured using semiautomated procedures. Linear mixed models were used to investigate differences between HD and controls in relation to motor onset, controlling for TIV, sex, and age.

RESULTS

Extrapolating backwards in time, we found that differences in caudate and ventricular volumes between patients with HD and controls were evident 14 and 5 years, respectively, before motor onset (P < .05). At onset, caudate volume was 2.58 mL smaller than that in controls (P < .0001); ventricular volume was 9.27 mL larger (P < .0001). HD caudate atrophy rates were linear, showed low variability between subjects, and were approximately 10-fold higher than those in controls (P < .001). HD ventricular enlargement rates were variable between subjects, were approximately 4-fold higher than those in controls at onset (P < .001), and accelerated with disease duration (P = .02).

CONCLUSIONS

We provide evidence of acceleration of global atrophy in HD with disproportionate caudate involvement. Both caudate and global measures may be of use as early markers of HD pathology.

Dynamic causal modelling of effective connectivity from fMRI: are results reproducible and sensitive to Parkinson's disease and its treatment?

Dynamic causal modelling (DCM) of functional magnetic resonance imaging (fMRI) data offers new insights into the pathophysiology of neurological disease and mechanisms of effective therapies. Current applications can be used both to identify the most likely functional brain network underlying observed data and estimate the networks' connectivity parameters. We examined the reproducibility of DCM in healthy subjects (young 18–48 years, n = 27; old 50–80 years, n = 15) in the context of action selection. We then examined the effects of Parkinson's disease (50–78 years, Hoehn and Yahr stage 1–2.5, n = 16) and dopaminergic therapy. Forty-eight models were compared, for each of 90 sessions from 58 subjects. Model-evidences clustered according to sets of structurally similar models, with high correlations over two sessions in healthy older subjects. The same model was identified as most likely in healthy controls on both sessions and in medicated patients. In this most likely network model, the selection of action was associated with enhanced coupling between prefrontal cortex and the pre-supplementary motor area. However, the parameters for intrinsic connectivity and contextual modulation in this model were poorly correlated across sessions. A different model was identified in patients with Parkinson's disease after medication withdrawal. In “off” patients, action selection was associated with enhanced connectivity from prefrontal to lateral premotor cortex. This accords with independent evidence of a dopamine-dependent functional disconnection of the SMA in Parkinson's disease. Together, these results suggest that DCM model selection is robust and sensitive enough to study clinical populations and their pharmacological treatment. For critical inferences, model selection may be sufficient. However, caution is required when comparing groups or drug effects in terms of the connectivity parameter estimates, if there are significant posterior covariances among parameters.

A functional role for adult hippocampal neurogenesis in spatial pattern separation

The dentate gyrus (DG) of the mammalian hippocampus is hypothesized to mediate pattern separation-the formation of distinct and orthogonal representations of mnemonic information-and also undergoes neurogenesis throughout life. How neurogenesis contributes to hippocampal function is largely unknown. Using adult mice in which hippocampal neurogenesis was ablated, we found specific impairments in spatial discrimination with two behavioral assays: (i) a spatial navigation radial arm maze task and (ii) a spatial, but non-navigable, task in the mouse touch screen. Mice with ablated neurogenesis were impaired when stimuli were presented with little spatial separation, but not when stimuli were more widely separated in space. Thus, newborn neurons may be necessary for normal pattern separation function in the DG of adult mice.

BDNF val66met influences time to onset of levodopa induced dyskinesia in Parkinson's disease

BACKGROUND

Levodopa induced dyskinesias (LID) are a common problem which ultimately limit the effective treatment of patients with Parkinson's disease (PD). There is accumulating evidence that LID develop due to abnormal synaptic plasticity, which is in turn influenced by the release of brain derived neurotrophic factor (BDNF).

METHODS

The influence of a common functional polymorphism of the BDNF gene on the risk of developing dyskinesias in a large cohort of patients with PD (n = 315), who were independently and variably treated with levodopa and/or other dopaminergic treatments, was investigated.

RESULTS

Patients with the met allele of BDNF, associated with lower activity dependent secretion of BDNF, were at significantly higher risk of developing dyskinesias earlier in the course of treatment with dopaminergic agents (hazard ratio for each additional met allele 2.12, p = 0.001), which persisted following adjustment for potential confounding variables.

CONCLUSION

This functional polymorphism may help predict which individuals are most at risk of LID and is consistent with the known actions of BDNF on synaptic plasticity in the striatum.

Incidence of early-onset dementias in Cambridgeshire, United Kingdom

OBJECTIVE

To estimate the incidence of early-onset dementias in a defined area of Cambridgeshire served by Addenbrooke's Hospital.

METHODS

The area selected for the study was that covered by the local authority areas of Cambridge City, East Cambridgeshire, and South Cambridgeshire. Cases were identified from the specialist memory and dementia clinics held at Addenbrooke's Hospital and were defined as those patients resident in the target area at the time of diagnosis, who were diagnosed with dementia before the age of 65 years between June 1, 2000, and May 31, 2006.

RESULTS

No obvious pattern by sex was present. The incidence for all cases of primary dementia for the age range 45-64 years was estimated to be 11.5 cases per 100,000 person-years (95% CI 8.6-15.0). The incidence of frontotemporal dementia for the age range 45-64 years was estimated to be 3.5 cases per 100,000 person-years (95% CI 2.0-5.7); for Alzheimer disease the incidence for the same group was 4.2 (95% CI 2.5-6.6) and for Huntington disease the incidence rate of cases becoming affected (with or without dementia) was 0.8 (95% CI 0.2-2.3).

CONCLUSION

If the incidence rates were extrapolated across England and Wales, in the region of 460 new cases of frontotemporal dementia and 550 new cases of Alzheimer disease could be expected each year in the 45-64 years age group.

Long-term clinical and positron emission tomography outcome of fetal striatal transplantation in Huntington's disease

Two patients with moderate Huntington's disease (HD) received bilateral fetal striatal allografts. One patient demonstrated, for the first time, increased striatal D2 receptor binding, evident with 11C-raclopride positron emission tomography, and prolonged clinical improvement over 5 years, suggesting long term survival and efficacy of the graft. The other patient did not improve clinically or radiologically. Our results indicate that striatal transplantation in HD may be beneficial but further studies are needed to confirm this.

Parkinson's disease and dopaminergic therapy--differential effects on movement, reward and cognition

Cognitive deficits are very common in Parkinson's disease particularly for ‘executive functions’ associated with frontal cortico-striatal networks. Previous work has identified deficits in tasks that require attentional control like task-switching, and reward-based tasks like gambling or reversal learning. However, there is a complex relationship between the specific cognitive problems faced by an individual patient, their stage of disease and dopaminergic treatment. We used a bimodality continuous performance task during fMRI to examine how patients with Parkinson's disease represent the prospect of reward and switch between competing task rules accordingly. The task-switch was not separately cued but was based on the implicit reward relevance of spatial and verbal dimensions of successive compound stimuli. Nineteen patients were studied in relative ‘on’ and ‘off’ states, induced by dopaminergic medication withdrawal (Hoehn and Yahr stages 1–4). Patients were able to successfully complete the task and establish a bias to one or other dimension in order to gain reward. However the lateral prefrontal cortex and caudate nucleus showed a non-linear U-shape relationship between motor disease severity and regional brain activation. Dopaminergic treatment led to a shift in this U-shape function, supporting the hypothesis of differential neurodegeneration in separate motor and cognitive cortico–striato–thalamo–cortical circuits. In addition, anterior cingulate activation associated with reward expectation declined with more severe disease, whereas activation following actual rewards increased with more severe disease. This may facilitate a change in goal-directed behaviours from deferred predicted rewards to immediate actual rewards, particularly when on dopaminergic treatment. We discuss the implications for investigation and optimal treatment of this common condition at different stages of disease.

Hand tapping: a simple, reproducible, objective marker of motor dysfunction in Huntington's disease

Huntington's disease (HD) is a severe neurodegenerative condition in which the impairment in voluntary movement is related to functional disability. Clinical assessment of motor deficit currently relies largely on subjective rating scales without objective measurement. We have developed a quick and easy-to-use hand tapping device that enables measurement of (a) the number of taps in 30 seconds, (b) variability in tapping rhythm and (c) fatigue over the testing period. Initial cross-sectional testing of 178 consecutive HD clinic patients using an early model of the device showed that the total number of taps in 30 seconds correlated with the motor UHDRS (Spearmann's rho, r(s) = -0.81, p < 0.0001) and independence scores (r(s) = 0.78, p = 0.01). Longitudinal data from a small cohort followed over 10 years reveals a correlation between total number of taps in 30 seconds and motor UHDRS over time (rs = -0.49, p < 0.001), and suggests the technique may provide an objective measure of disease progression. Further tests on 15 HD patients and 9 controls were repeated three times in a single day using an updated device. The HD group made significantly fewer taps in 30 seconds (median HD = 79, control = 104, p = 0.009) and had greater variability of inter-tap interval (mean interdecile range HD = 148, control = 56, p = 0.016) compared to controls. Both the total number of taps and variability of inter-tap interval correlated with motor UHDRS. Of vital importance for any potential marker of disease progression is that these tapping parameters were reproducible with repeated measurement. Given that hand tapping parameters differ between HD and control populations, they correlate with motor UHDRS over time and are reproducible, we propose that assessment of hand tapping represents a useful objective adjunct to the clinical assessment of HD patients.

The utility of the Cambridge Behavioural Inventory in neurodegenerative disease

We investigated the utility of the Cambridge Behavioural Inventory (CBI), a carer-completed questionnaire, in a large cohort with Parkinson's disease (PD) (n = 215). In a sub-cohort of 112 patients with PD, the CBI was found to be a valid instrument compared with the Neuropsychiatric Inventory, PDQ-39 and UPDRS, with high internal consistency. Furthermore, in the whole cohort, the CBI was sensitive to changes in behaviour with disease progression. Comparison between CBI scores in PD and other neurodegenerative diseases, including Huntington's disease (HD) (n = 75), Alzheimer's disease (AD) (n = 96) and frontal variant frontotemporal dementia (fvFTD) (n = 64), revealed distinct profiles for each disease. Predominant deficits were "sleep"' and "self care" in PD; "memory" in HD and AD; and "motivation" and "stereotypic behaviours" in fvFTD. The CBI is a robust, easy-to-use and valid instrument, which has the capacity to discriminate between neurodegenerative diseases, and may be of value in monitoring therapeutic interventions.

Relapsing encephalopathy in a patient with alpha-methylacyl-CoA racemase deficiency

Alpha-methylacyl-CoA racemase (AMACR) deficiency is a rare disorder of fatty acid metabolism which has recently been described in three adult cases. We have identified a further patient with clinical features of a relapsing encephalopathy, seizures and cognitive decline over a 40 year period. Biochemical studies revealed grossly elevated plasma pristanic acid levels, and a deficiency of AMACR in skin fibroblasts. Sequence analysis of AMACR cDNA identified a homozygous point mutation (c154T>C). This case adds to the phenotypic variation seen in this peroxisomal disorder and highlights the importance of screening for plasma pristanic acid levels in patients with unexplained relapsing encephalopathies.

The effect of truncated human alpha-synuclein (1-120) on dopaminergic cells in a transgenic mouse model of Parkinson's disease

Alpha-Synuclein is thought to play an important role in the pathology of Parkinson's disease (PD). Truncated forms of this protein can be found in PD brain extracts, and these species aggregate faster and are more susceptible to oxidative stress than the full-length protein. We investigated the effect of truncated alpha-synuclein on dopaminergic cells using a transgenic mouse expressing alpha-synuclein (1-120) driven by the rat tyrosine hydroxylase promoter on a mouse alpha-synuclein null background. We found a selective reduction in the yield of dopaminergic cells from transgenic embryonic ventral mesencephalic cell cultures. However, in vivo the substantia nigra/ventral tegmentum dopaminergic cell counts were not reduced in transgenics, although these mice are known to have reduced striatal dopamine. When transplanted to the striatum in the unilateral 6-hydroxydopamine-lesioned mouse model of PD, dopaminergic cells derived from transgenic embryonic ventral mesencephala were significantly smaller at 6 weeks, and showed a trend towards being less effective at ameliorating rotational asymmetry than those from control alpha-synuclein null mice. These results suggest that alpha-synuclein (1-120) renders dopaminergic cells more susceptible to stress, which may have important implications as to how this truncated protein might contribute to dopaminergic cell death in sporadic PD.

Investigation of TGFB2 as a candidate gene in multiple sclerosis and Parkinson’s disease

Given the known roles of TGFbeta2 in both regulating the immune system and promoting the survival of dopaminergic neurons, it is feasible that genetic variations in TGFB2 might play an aetiological role in neurological diseases such as Multiple Sclerosis (MS) and Parkinson's disease (PD). Hence we performed an indirect association analysis of TGFB2 using 8 haplotype-tagging SNPs in a population of 937 MS patients, 538 PD cases and 2022 controls. We found no evidence for association with susceptibility or progression of MS, but have demonstrated a trend towards association of the 5' region of the gene with susceptibility to PD. Further analysis of TGFB2 is warranted in other PD cohorts.

Evolution of cognitive dysfunction in an incident Parkinson's disease cohort

We have previously performed detailed clinical and neuropsychological assessments in a community-based cohort of patients with newly diagnosed parkinsonism, and through analysis of a subcohort with idiopathic Parkinson's disease (PD), we have demonstrated that cognitive dysfunction occurs even at the time of PD diagnosis and is heterogeneous. Longitudinal follow-up of the cohort has now been performed to examine the evolution of cognitive dysfunction within the early years of the disease. One hundred and eighty (79%) eligible patients from the original cohort with parkinsonism were available for re-assessment at between 3 and 5 years from their initial baseline assessments. PD diagnoses were re-validated with repeated application of the UKPDS Brain Bank criteria in order to maximize sensitivity and specificity, following which a diagnosis of idiopathic PD was confirmed in 126 patients. Thirteen out of 126 (10%) had developed dementia at a mean (SD) of 3.5 (0.7) years from diagnosis, corresponding to an annual dementia incidence of 30.0 (16.4-52.9) per 1000 person-years. A further 57% of PD patients showed evidence of cognitive impairment, with frontostriatal deficits being most common amongst the non-demented group. However, the most important clinical predictors of global cognitive decline following correction for age were neuropsychological tasks with a more posterior cortical basis, including semantic fluency and ability to copy an intersecting pentagons figure, as well as a non-tremor dominant motor phenotype at the baseline assessment. This work clarifies the profile of cognitive dysfunction in early PD and demonstrates that the dementing process in this illness is heralded by both postural and gait dysfunction and cognitive deficits with a posterior cortical basis, reflecting probable non-dopaminergic cortical Lewy body pathology. Furthermore, given that these predictors of dementia are readily measurable within just a few minutes in a clinical setting, our work may ultimately have practical implications in terms of guiding prognosis in individual patients.

Cell repair in Parkinson’s disease

Parkinson’s disease (PD) is a progressive neurodegenerative movement disorder with the cardinal clinical features of muscular rigidity, resting tremor and bradykinesia. The prevalence of this disease is approximately 2% of those aged over 65 years, thus causing significant morbidity. The disease is characterized by degeneration of dopaminergic cells in the substantia nigra pars compacta, resulting in reduced dopaminergic input to the striatum. Significant clinical benefit can be achieved through the restoration of dopamine levels in this system with pharmacological interventions, although these therapies are only symptomatic and the disease progresses. Indeed, with disease progression other features often appear, including autonomic, affective and cognitive dysfunction, reflecting pathology at non-nigral sites. The occurrence of neural stem cells (NSCs) in the adult CNS, which, under certain conditions, are able to proliferate and renew neuronal numbers, has raised great expectations for alternative therapeutic applications in the treatment of PD. Indeed, it is potentially possible to harness this capacity either directly (increase of local proliferation, directed migration and differentiation) or indirectly (in vitro expansion before their transplantation), to facilitate the generation of specific cell types in order to replace missing neurons in neurodegenerative diseases. The manipulation of embryonic stem cells or their derivatives also offers a promising alternative as extensive proliferation may be achieved and, most importantly, directed differentiation to a dopaminergic phenotype is possible. Nevertheless, neuronal replacement will only be possible if proliferating or transplanted NSCs and their progeny can be harnessed at sites of pathology. It is the manipulation of stem cells both in vivo and in vitro, in the context of repairing the core pathological hallmark of PD, that is the main focus of this report.