Imaging dopamine transporters in Parkinson’s disease

Diagnosis of Parkinson's disease by eliciting trait-specific eye movements in multi-visual tasks

BACKGROUND

Parkinson's Disease (PD) is a neurodegenerative disorder, and eye movement abnormalities are a significant symptom of its diagnosis. In this paper, we developed a multi-task driven by eye movement in a virtual reality (VR) environment to elicit PD-specific eye movement abnormalities. The abnormal features were subsequently modeled by using the proposed deep learning algorithm to achieve an auxiliary diagnosis of PD.

METHODS

We recruited 114 PD patients and 125 healthy controls and collected their eye-tracking data in a VR environment. Participants completed a series of specific VR tasks, including gaze stability, pro-saccades, anti-saccades, and smooth pursuit. After the tasks, eye movement features were extracted from the behaviors of fixations, saccades, and smooth pursuit to establish a PD diagnostic model.

RESULTS

The performance of the models was evaluated through cross-validation, revealing a recall of 97.65%, an accuracy of 92.73%, and a receiver operator characteristic area under the curve (ROC-AUC) of 97.08% for the proposed model.

CONCLUSION

We extracted PD-specific eye movement features from the behaviors of fixations, saccades, and smooth pursuit in a VR environment to create a model with high accuracy and recall for PD diagnosis. Our method provides physicians with a new auxiliary tool to improve the prognosis and quality of life of PD patients.

Missed Insights for Earlier Management of Parkinson's Disease and the Value of Dopamine Transporter (DAT) Scans

Background/Objectives: This retrospective study focused on the role of Dopamine Transporter (DAT) scans in diagnosing Parkinson's Disease (PD) in older adults with cognitive impairment (CI). Methods: We retrospectively analyzed brain imaging of 6483 individuals aged 60 and above with CI. Among these, 297 underwent a DAT scan, with 189 testing positive and 89 starting dopamine therapy. In contrast, 173 patients exhibited PD-associated structural changes on CT or MRI without receiving DAT scans or treatment. Results: Of these patients, 50 (29%) experienced falls. This points towards a potential missed diagnosis of PD, which can respond to therapy in the early stages. Conclusions: Our results suggest that providers may overlook subtle signs of parkinsonism in patients with CI, resulting in symptoms worsening and treatment delay. Since CI is often first brought to the attention of PCPs, our findings call for an increased effort to inform PCPs of the role of DAT scans in aiding the diagnosis of dopamine deficiency states. By understanding PD-related structural changes seen on brain imaging and using a DAT scan to confirm dopamine deficiency, treatment for PD or related states might be started earlier or a timely referral made to a specialist, reducing patient disability and improving their quality of life.

Age and gender effects on striatal dopamine transporter density and cerebral perfusion in individuals with non-degenerative parkinsonism: a dual-phase 18F-FP-CIT PET study

BACKGROUND

Dual-phase fluorine-18 labeled N-3-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (18F-FP-CIT) positron emission tomography (PET) scans could be used to support disorders like Parkinson's disease (PD). Dopamine transporter (DAT) binding and cerebral perfusion are associated with ageing and gender. We investigated the effects of age and gender on non-degenerative parkinsonism, using automated quantification in striatum: specific binding ratios (SBRs) for DAT binding in delayed phase PET (dCIT) and standardized-uptake-value ratios (SUVRs) for cerebral perfusion in early phase PET (eCIT). We also examined the correlations between SBR and SUVR.

METHODS

This retrospective study analyzed subjects with dual-phase 18F-FP-CIT PET scans. The eCIT images were acquired immediately post-injection, and dCIT images were taken 120 min later. With Brightonix software, automated quantification of SBRs for dCIT and SUVRs for eCIT were acquired from visually normal scans. The effects of aging and gender were assessed by regressing SBRs and SUVRs on age for both genders. The correlations between SUVRs and SBRs were evaluated.

RESULTS

We studied 79 subjects (34 males and 45 females). An age-related reduction in SBRs was observed in the dorsal striatum, ventral striatum, caudate nucleus, and putamen for both genders. SUVRs were found to negatively correlate with age in the dorsal striatum, ventral striatum, caudate nucleus, and putamen for males and in the dorsal striatum and caudate nucleus for females. Positive correlations between SBRs and SUVRs in the dorsal striatum, ventral striatum, caudate nucleus, and putamen for male and in the dorsal striatum, caudate nucleus, and putamen for females.

CONCLUSIONS

Using quantified values from dual-phase 18F-FP-CIT PET with a single injection, we demonstrate a negative impact of age on SBRs (DAT binding) in the striatum for both genders and SUVRs (cerebral perfusion) in the dorsal striatum and caudate nucleus for both genders and in the ventral striatum and putamen for males. Additionally, we found positive associations between SBR and SUVR values in the dorsal striatum, caudate nucleus, and putamen for both genders and in the ventral striatum for males.

The complex role of inflammation and gliotransmitters in Parkinson's disease

Our understanding of the role of innate and adaptive immune cell function in brain health and how it goes awry during aging and neurodegenerative diseases is still in its infancy. Inflammation and immunological dysfunction are common components of Parkinson's disease (PD), both in terms of motor and non-motor components of PD. In recent decades, the antiquated notion that the central nervous system (CNS) in disease states is an immune-privileged organ, has been debunked. The immune landscape in the CNS influences peripheral systems, and peripheral immunological changes can alter the CNS in health and disease. Identifying immune and inflammatory pathways that compromise neuronal health and survival is critical in designing innovative and effective strategies to limit their untoward effects on neuronal health.

Spatiotemporal patterns of putaminal dopamine processing in Parkinson's disease: A multi-tracer positron emission tomography study

Alterations in different aspects of dopamine processing may exhibit different progressive behaviours throughout the course of Parkinson's disease. We used a novel data-driven multivariate approach to quantify and compare spatiotemporal patterns related to different aspects of dopamine processing from cross-sectional Parkinson's subjects obtained with: 1) 69 [¹¹C]±dihydrotetrabenazine (DTBZ) scans, most closely related to dopaminergic denervation; 2) 73 [¹¹C]d-threo-methylphenidate (MP) scans, marker of dopamine transporter density; 3) 50 6-[¹⁸F]fluoro-l-DOPA (FD) scans, marker of dopamine synthesis and storage. The anterior-posterior gradient in the putamen was identified as the most salient feature associated with disease progression, however the temporal progression of the spatial gradient was different for the three tracers. The expression of the anterior-posterior gradient was the highest for FD at disease onset compared to that of DTBZ and MP (P = 0.018 and P = 0.047 respectively), but decreased faster (P = 0.006) compared to that of DTBZ. The gradient expression for MP was initially similar but decreased faster (P = 0.015) compared to that for DTBZ. These results reflected unique temporal behaviours of regulatory mechanisms related to dopamine synthesis (FD) and reuptake (MP). While the relative early disease upregulation of dopamine synthesis in the anterior putamen prevalent likely extends to approximately 10 years after symptom onset, the presumed downregulation of dopamine transporter density may play a compensatory role in the prodromal/earliest disease stages only.

Virtual Rehabilitation in Parkinson Disease: A Dopamine Transporter Imaging Study

OBJECTIVE

The aim of the study was to verify the effect of a virtual rehabilitation protocol for patients with Parkinson disease, primarily assessing striatal dopamine transporters and secondarily motor symptoms and quality of life.

DESIGN

Nineteen patients with Parkinson disease underwent an 8-wk virtual rehabilitation protocol using XBOX 360S. Evaluation of dopamine transporters was performed by single-photon emission computed tomography using TRODAT-1 as the radioligand. Participants were clinically assessed using the Unified Parkinson Disease Rating Scale to quantify motor symptoms. Moreover, the Parkinson Disease Questionnaire and Short-Form Health Status Survey were used to assess quality of life and the Berg Balance Scale to assess balance.

RESULTS

Regarding our primary outcome, dopamine transporter was significantly increased in the putamen contralateral to the clinically most affected body side (P = 0.034) considering preintervention and postintervention measurements. Furthermore, we observed significant improvement in Unified Parkinson Disease Rating Scale (10-point reduction, P = 0.001), Parkinson Disease Questionnaire (11.3-point reduction, P = 0.001), Short-Form Health Status Survey ("Functional capacity," P = 0.001; "Pain," P = 0.006; and "Mental Health" domains, P < 0.001), and Berg Balance Scale (5-point increase, P = 0.015).

CONCLUSIONS

In our group of Parkinson disease patients, this virtual rehabilitation protocol enabled a dopamine transporter increase in the region of the putamen contralateral to the clinically most affected body side. Moreover, motor signs and quality of life were significantly improved.

Parkinson's disease laterality: a 11C-PE2I PET imaging study

Asymmetry of striatal dopaminergic deficits and motor symptoms is a typical characteristic of idiopathic Parkinson's disease (PD). This study aims to characterise the trend of asymmetry in moderate-stage PD. We performed a 19-month longitudinal study in 27 patients with PET-CT imaging and appropriate clinical assessments. 11C-PE2I non-displaceable binding potential (BPND) was calculated bilaterally for the striatum at baseline and follow-up to estimate the in vivo density of striatal dopamine transporters (DAT). Changes in striatal 11C-PE2I BPND over time were more prominent in the ipsilateral as compared to contralateral side. Changes in MDS-UPDRS-III (motor component of the Movement Disorders Society Unified PD Rating Scale) were not different between the clinically most and least affected body sides. Our data support that the asymmetry in striatal dopaminergic degeneration becomes less prominent in moderate-stage PD. In contrast, during the above period, the asymmetry of motor symptoms was maintained between the clinically most and least affected body sides.

Joint pattern analysis applied to PET DAT and VMAT2 imaging reveals new insights into Parkinson's disease induced presynaptic alterations

Most neurodegenerative diseases are known to affect several aspects of brain function, including neurotransmitter systems, metabolic and functional connectivity. Diseases are generally characterized by common clinical characteristics across subjects, but there are also significant inter-subject variations. It is thus reasonable to expect that in terms of brain function, such clinical behaviors will be related to a general overall multi-system pattern of disease-induced alterations and additional brain system-specific abnormalities; these additional abnormalities would be indicative of a possible unique system response to disease or subject-specific propensity to a specific clinical progression. Based on the above considerations we introduce and validate the use of a joint pattern analysis approach, canonical correlation analysis and orthogonal signal correction, to analyze multi-tracer PET data to identify common (reflecting functional similarities) and unique (reflecting functional differences) information provided by each tracer/target. We apply the method to [11C]-DTBZ (VMAT2 marker) and [11C]-MP (DAT marker) data from 15 early Parkinson's disease (PD) subjects; the behavior of these two tracers/targets is well characterized providing robust reference information for the method's outcome. Highly significant common subject profiles were identified that decomposed the characteristic dopaminergic changes into three distinct orthogonal spatial patterns: 1) disease-induced asymmetry between the less and more affected dorsal striatum; 2) disease-induced gradient with caudate and ventral striatum being relatively spared compared to putamen; 3) progressive loss in the less affected striatum, which correlated significantly with disease duration (p < 0.01 for DTBZ, p < 0.05 for MP). These common spatial patterns reproduce all known aspects of these two targets/tracers. In addition, orthogonality of the patterns may indicate different mechanisms underlying disease initiation or progression. Information unique to each tracer revealed a residual striatal asymmetry when targeting VMAT2, consistent with the notion that VMAT2 density is highly related to terminal degeneration; and a residual DAT disease-induced gradient in the striatum with relative DAT preservation in the substantia nigra. This finding may be indicative either of a possible DAT specific early disease compensation and/or related to disease origin. These results demonstrate the applicability and relevance of the joint pattern analysis approach to datasets obtained with two PET tracers; this data driven method, while recapitulating known aspects of the PD-induced tracer/target behaviour, was found to be statistically more robust and provided additional information on (i) correlated behaviors of the two systems, identified as orthogonal patterns, possibly reflecting different disease-induced alterations and (ii) system specific effects of disease. It is thus expected that this approach will be very well suited to the analysis of multi-tracer and/or multi-modality data and to relating the outcomes to different aspects of disease.

Discriminating among degenerative parkinsonisms using advanced (123)I-ioflupane SPECT analyses

(123)I-ioflupane single photon emission computed tomography (SPECT) is a sensitive and well established imaging tool in Parkinson's disease (PD) and atypical parkinsonian syndromes (APS), yet a discrimination between PD and APS has been considered inconsistent at least based on visual inspection or simple region of interest analyses. We here reappraise this issue by applying advanced image analysis techniques to separate PD from the various APS. This study included 392 consecutive patients with degenerative parkinsonism undergoing (123)I-ioflupane SPECT at our institution over the last decade: 306 PD, 24 multiple system atrophy (MSA), 32 progressive supranuclear palsy (PSP) and 30 corticobasal degeneration (CBD) patients. Data analysis included voxel-wise univariate statistical parametric mapping and multivariate pattern recognition using linear discriminant classifiers. MSA and PSP showed less ioflupane uptake in the head of caudate nucleus relative to PD and CBD, yet there was no difference between MSA and PSP. CBD had higher uptake in both putamen relative to PD, MSA and PSP. Classification was significant for PD versus APS (AUC 0.69, p < 0.05) and between APS subtypes (MSA vs CBD AUC 0.80, p < 0.05; MSA vs PSP AUC 0.69 p < 0.05; CBD vs PSP AUC 0.69 p < 0.05). Both striatal and extra-striatal regions contain classification information, yet the combination of both regions does not significantly improve classification accuracy. PD, MSA, PSP and CBD have distinct patterns of dopaminergic depletion on (123)I-ioflupane SPECT. The high specificity of 84-90% for PD versus APS indicates that the classifier is particularly useful for confirming APS cases.

Precision Medicine: Clarity for the Complexity of Dementia

Three key elements to precision medicine are stratification by risk, detection of pathophysiological processes as early as possible (even before clinical presentation), and alignment of mechanism of action of intervention(s) with an individual's molecular driver(s) of disease. Used for decades in the management of some rare diseases and now gaining broad currency in cancer care, a precision medicine approach is beginning to be adapted to cognitive impairment and dementia. This review focuses on the application of precision medicine to address the clinical and biological complexity of two common neurodegenerative causes of dementia: Alzheimer disease and Parkinson disease.

Molecular imaging of neuropsychiatric symptoms in Alzheimer's and Parkinson's disease

Neuropsychiatric symptoms (NPS) are very common in neurodegenerative diseases and are a major contributor to disability and caregiver burden. There is accumulating evidence that NPS may be a prodrome and/or a "risk factor" of neurodegenerative diseases. The medications used to treat these symptoms in younger patients are not very effective in patients with neurodegenerative disease and may have serious side effects. An understanding of the neurobiology of NPS is critical for the development of more effective intervention strategies. Targeting these symptoms may also have implications for prevention of cognitive or motor decline. Molecular brain imaging represents a bridge between basic and clinical observations and provides many opportunities for translation from animal models and human post-mortem studies to in vivo human studies. Molecular brain imaging studies in Alzheimer's disease (AD) and Parkinson's disease (PD) are reviewed with a primary focus on positron emission tomography studies of NPS. Future directions for the field of molecular imaging in AD and PD to understand the neurobiology of NPS will be discussed.

Single vial freeze-dried TRODAT-1 kit: preparation and demonstration of clinical efficacy of [(99m)Tc]TRODAT-1 in Indian scenario

A single vial freeze-dried kit formulation for preparation of three patients' dose of [(99m)Tc]TRODAT-1 has been developed for early diagnosis of Parkinson's disease (PD). Kits were evaluated to ascertain the purity, stability and batch to batch variations. Preclinical evaluation was carried out in laboratory animals and clinical imaging was performed in human patients with PD. The labeling yield and purity of [(99m)Tc]TRODAT-1 was >90%. Swiss mice showed retention of [(99m)Tc]TRODAT-1 in the mid brain region. Clinical studies showed decreased striatal uptake with increasing severity of PD.

Evaluation of progression markers in the premotor phase of Parkinson's disease: the progression markers in the premotor phase study

BACKGROUND

The clinical diagnosis of Parkinson's disease (PD) is proposed to be too late for the application of beneficial neuroprotective treatment. Thus, it is important to identify and follow individuals at risk for PD in order to gain knowledge about the prodromal course of the disease. Substantia nigra hyperechogenicity (SN+) has been confirmed as a risk factor for PD and appears promising as a predictor of PD, particularly in combination with other putative PD markers. We present the design and initial data of a 2-year longitudinal investigation of subjects proposed to be at high risk of developing PD (HRPD), compared to early PD patients and control subjects. The aim of the presented study is to monitor progression of the neurodegenerative process to motor PD.

METHODS

In total, 40 HRPD, 16 PD and 41 control individuals were recruited. The HRPD subjects had SN+ and additionally either 1 cardinal PD motor sign or 2 further risk (e.g. positive family history) or prodromal markers (e.g. hyposmia). In this cohort, motor function, olfaction, mood and blood markers will be evaluated every 6 months, complemented by a comprehensive clinical, imaging and electrophysiological assessment.

RESULTS

PD, HRPD and control subjects did not differ significantly regarding age, but the HRPD group consisted mainly of males (72.5% of HRPD subjects vs. 43.9% of controls; p = 0.013). Mean disease duration in PD patients was 31 months (range 15-56). HRPD subjects were predominantly recruited according to the occurrence of slight motor signs (HRPD 77.5%, PD 100%, p = 0.05; controls 0%, HRPD vs. controls, p < 0.017). The Unified Parkinson's Disease Rating Scale motor score (mean, range) indicated that the HRPD group (4, 0-12) had values between those of controls (0, 0-2; p < 0.017) and PD subjects (26, 9-55; p < 0.017). Among nonmotor symptoms, hyposmia was more common in both HRPD (47.5%) and PD subjects (75%) than in controls (5.1%; p < 0.017 for both comparisons).

CONCLUSIONS

Here, we describe the recruitment of a highly enriched-risk cohort and a promising study design to assess progression to motor PD. Whether the HRPD group indeed suffers from early, PD-specific neurodegeneration remains to be verified in the ongoing follow-up examinations.

Progressive loss of striatal dopamine terminals in MPTP-induced acute parkinsonism in cynomolgus monkeys using vesicular monoamine transporter type 2 PET imaging ([(18)F]AV-133)

The 1-methyl-4-phenyl-1,2,3,4-tetrahydropyridine (MPTP)-induced parkinsonism model, particularly in non-human primates, remains the gold-standard for studying the pathogenesis and assessing novel therapies for Parkinson's disease. However, whether the loss of dopaminergic neurons in this model is progressive remains controversial, mostly due to the lack of objective in vivo assessment of changes in the integrity of these neurons. In the present study, parkinsonism was induced in cynomolgus monkeys by intravenous administration of MPTP (0.2 mg/kg) for 15 days; stable parkinsonism developed over 90 days, when the symptoms were stable. Noninvasive positron emission tomographic neuroimaging of vesicular monoamine transporter 2 with 9-[(18)F] fluoropropyl-(+)-dihydrotetrabenazine ([(18)F]AV-133) was used before, and 15 and 90 days after the beginning of acute MPTP treatment. The imaging showed evident progressive loss of striatal uptake of [(18)F]AV-133. The dopaminergic denervation severity had a significant linear correlation with the clinical rating scores and the bradykinesia subscores. These findings demonstrated that [(18)F]AV-133 PET imaging is a useful tool to noninvasively evaluate the evolution of monoaminergic terminal loss in a monkey model of MPTP-induced parkinsonism.

Nigrostriatal dopamine terminal imaging with dopamine transporter SPECT: an update

This article gives an update on nigrostriatal dopamine terminal imaging, with emphasis on SPECT performed with the presynaptic dopamine transporter (DAT) ligand (123)I-FP-CIT. The paper covers the rational use of this technique in the diagnostic work-up of patients with known or suspected parkinsonian syndromes. In detail, it addresses the impact of the method for the proof or exclusion of neurodegenerative parkinsonism, for its early and preclinical diagnosis, and for the evaluation of disease progression. The importance of normal DAT binding for differentiating symptomatic parkinsonism and relevant tremor syndromes from neurodegeneration is highlighted. Particularly emphasized is the role of DAT SPECT for diagnosing Lewy body dementia and its separation from Alzheimer dementia. Finally, some remarks deal with the economic aspects of the use of these imaging techniques in the clinical setting.

A phenotypic model recapitulating the neuropathology of Parkinson's disease

This study was undertaken to develop a phenotypic model recapitulating the neuropathology of Parkinson's disease (PD). Such a model would show loss of dopamine in the basal ganglia, appearance of Lewy bodies, and the early stages of motor dysfunction. The model was developed by subcutaneously injecting biodegradable microspheres of rotenone, a complex I inhibitor in 8-9 month old, ovariectomized Long-Evans rats. Animals were observed for changes in body weight and motor activity. At the end of 11-12 weeks animals were euthanized and the brains examined for histopathological changes. Rotenone treated animals gain weight and appear normal and healthy as compared to controls but showed modest hypokinesia around 5-6 weeks posttreatment. Animals showed loss of dopaminergic (DA) neurons and the appearance of putative Lewy bodies in the substantia nigra. Neuroinflammation and oxidative stress were evidenced by the appearance of activated microglia, iron precipitates, and 8-oxo-2'-deoxyguanosine a major product of DNA oxidation. The dorsal striatum, the projection site of midbrain DA neurons, showed a significant reduction in tyrosine hydroxylase immunostaining, together with an increase in reactive astrocytes, an early sign of DA nerve terminal damage. Levels of vesicular monoamine transporter 2 (VMAT2) were significantly reduced in the dorsal striatum; however, there was an unexpected increase in dopamine transporter (DAT) levels. Old, ovariectomized females treated with rotenone microspheres present with normal weight gain and good health but a modest hypokinesia. Accompanying this behavioral phenotype are a constellation of neuropathologies characteristic of PD that include loss of DA neurons, microglia activation, oxidative damage to nuclear DNA, iron deposition, and appearance of putative Lewy bodies. This phenotypic model recapitulating the neuropathology of Parkinson's disease could provide insight into early mechanisms of pathogenesis and could aid in the identification of biomarkers to identify patients in early stage, PD.

A progressive dopaminergic phenotype associated with neurotoxic conversion of α-synuclein in BAC-transgenic rats

Conversion of soluble α-synuclein into insoluble and fibrillar inclusions is a hallmark of Parkinson's disease and other synucleinopathies. Accumulating evidence points towards a relationship between its generation at nerve terminals and structural synaptic pathology. Little is known about the pathogenic impact of α-synuclein conversion and deposition at nigrostriatal dopaminergic synapses in transgenic mice, mainly owing to expression limitations of the α-synuclein construct. Here, we explore whether both the rat as a model and expression of the bacterial artificial chromosome construct consisting of human full-length wild-type α-synuclein could exert dopaminergic neuropathological effects. We found that the human promoter induced a pan-neuronal expression, matching the rodent α-synuclein expression pattern, however, with prominent C-terminally truncated fragments. Ageing promoted conversion of both full-length and C-terminally truncated α-synuclein species into insolube and proteinase K-resistant fibres, with strongest accumulation in the striatum, resembling biochemical changes seen in human Parkinson's disease. Transgenic rats develop early changes in novelty-seeking, avoidance and smell before the progressive motor deficit. Importantly, the observed pathological changes were associated with severe loss of the dopaminergic integrity, thus resembling more closely the human pathology.

Striatal presynaptic dopamine in schizophrenia, Part I: meta-analysis of dopamine active transporter (DAT) density

BACKGROUND

Striatal dopaminergic neurotransmission has been postulated to be fundamental to the emergence of key symptoms of schizophrenia, such as psychotic symptoms, and is targeted by currently available dopaminergic drugs. A specific marker of the integrity of presynaptic dopamine neurons in the striatum, the density of striatal dopamine terminals, can be quantified through molecular neuroimaging of the dopamine active transporter (DAT). However, the currently available results using this approach in schizophrenia are inconsistent.

METHODS

Thirteen Single Photon Emission Tomography or Positron Emission Tomography (PET) studies investigating DAT density in the striatum of schizophrenic patients and matched controls were included in a quantitative meta-analysis. Binding potentials in the striatum, caudate, and putamen, as well as demographic, clinical, and methodological variables, were extracted from each publication. Hedges' g was used as a measure of effect size.

RESULTS

The overall database contained 202 subjects with schizophrenia and 147 controls, well matched with respect to sociodemographic variables. Striatal DAT density was not significantly different between patients and controls. Similar negative findings were regionally confirmed in the putamen and caudate. There was no moderating effect for external factors.

CONCLUSIONS

Our meta-analysis uncovered no evidence indicating altered density of striatal dopamine terminals in schizophrenia. Moreover, striatal DAT density did not seem to be influenced by antipsychotic medication or illness duration. Our data suggest that altered integrity of striatal dopaminergic synapses is not critical for the emergence of schizophrenia or its treatment. These findings should be useful in further refining dopaminergic hypotheses of schizophrenia.

Iodine-123 metaiodobenzylguanidine scintigraphy and iodine-123 ioflupane single photon emission computed tomography in Lewy body diseases: complementary or alternative techniques?

PURPOSE

To compare myocardial sympathetic imaging using (123)I-Metaiodobenzylguanidine (MIBG) scintigraphy and striatal dopaminergic imaging using (123)I-Ioflupane (FP-CIT) single photon emission computed tomography (SPECT) in patients with suspected Lewy body diseases (LBD).

METHODS

Ninety-nine patients who performed both methods within 2 months for differential diagnosis between Parkinson's disease (PD) and other parkinsonism (n = 68) or between dementia with Lewy bodies (DLB) and other dementia (n = 31) were enrolled. Sensitivity, specificity, accuracy, positive and negative predictive values of both methods were calculated.

RESULTS

For (123) I-MIBG scintigraphy, the overall sensitivity, specificity, accuracy, positive and negative predictive values in LBD were 83%, 79%, 82%, 86%, and 76%, respectively. For (123)I-FP-CIT SPECT, the overall sensitivity, specificity, accuracy, positive and negative predictive values in LBD were 93%, 41%, 73%, 71%, and 80%, respectively. There was a statistically significant difference between these two methods in patients without LBD, but not in patients with LBD.

CONCLUSIONS

LBD usually present both myocardial sympathetic and striatal dopaminergic impairments. (123)I-FP-CIT SPECT presents high sensitivity in the diagnosis of LBD; (123)I-MIBG scintigraphy may have a complementary role in differential diagnosis between PD and other parkinsonism. These scintigraphic methods showed similar diagnostic accuracy in differential diagnosis between DLB and other dementia.

Neural progenitor cells derived from adult bone marrow mesenchymal stem cells promote neuronal regeneration

AIM

It is well known that neural stem/progenitor cells (NS/PC) are an ideal cell type for the treatment of central nervous system (CNS) disease. However, ethical problems have severely hampered fetal NS/PC from being widely used as a source for stem cell therapy. Recently, it has been demonstrated that autologous bone marrow mesenchymal stem cells (BMSC) can transdifferentiate into neural progenitor cells (NPC). The biological function of BMSC derived NPC (MDNPC) in neuronal systems remains unknown. In the present study, we aimed to investigate whether MDNPC can promote in vitro neural regeneration, a process comprising mainly the generation of neurons and neurotransmitters.

MAIN METHODS

We co-cultured BMSC, MDNPC or fetal NS/PC with PC12 cells and studied their roles on proliferation, neurite formation and dopamine release from PC12 cells. Furthermore, we also explored the mechanisms by which MDNPC regulate dopamine secretion from PC12 derived neural cells using Western blot.

KEY FINDINGS

We found that both MDNPC and NS/PC had similar morphologies and there were no significant differences between MDNPC and NS/PC in promoting PC12 cell proliferation, neurite outgrowth, and dopamine release. We also demonstrated that NS/PC induced dopamine secretion was associated with an upregulation of dopamine transporter (DAT) levels.

SIGNIFICANCE

In summary, MDNPC were comparable to NS/PC in promoting neural regeneration, indicating that MDNPC are a promising candidate source of neural stem cells for the treatment of neurological diseases.

QSAR study and synthesis of new phenyltropanes as ligands of the dopamine transporter (DAT)

The dopamine transporter (DAT) plays a pivotal role in the regulation of dopamine neurotransmission, and is involved in a number of physiological functions and brain disorders. Furthermore the DAT analysis by molecular imaging techniques is a useful tool for the diagnosis and follow up treatment of diseases involving the DAT. In order to predict the affinity of new derivatives for the DAT, different QSAR molecular modeling models based on cocaine were compared. We have evaluated in these models tropane derivatives synthesized with original synthons which coupled properties of both fluorine and iodine atoms. One compound showed a high in vitro affinity and selectivity for the DAT (K(i)=0.87±0.04 nM). This compound should be radiolabeled with radioiodine for further investigations by SPECT.

Modelling of Parkinson's disease in mice

Although progress has been made in the symptomatic treatment of Parkinson's disease since the discovery of L-dopa in the 1960s, no neuroprotective therapy is yet available. Absence of adequate animal models of the disease that enable prediction of clinical success of potential treatments is often cited as a major impediment to progress and discourages researchers and pharmaceutical companies from investing resources to develop such treatments. Classic models are still widely used, but have been disappointing, and development of genetic models has given new hope. However, can a human disease be faithfully reproduced in a mouse? In this Review we summarise evidence that some genetic mouse models do reproduce key features of Parkinson's disease and show that much can be learned from even imperfect models. The hope is that this information could be used to advance the search for neuroprotective therapies for Parkinson's disease.

α-Synuclein and tau concentrations in cerebrospinal fluid of patients presenting with parkinsonism: a cohort study

BACKGROUND

Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy are brain disorders characterised by intracellular α-synuclein deposits. We aimed to assess whether reduction of α-synuclein concentrations in CSF was a marker for α-synuclein deposition in the brain, and therefore diagnostic of synucleinopathies.

METHODS

We assessed potential extracellular-fluid markers of α-synuclein deposition in the brain (total α-synuclein and total tau in CSF, and total α-synuclein in serum) in three cohorts: a cross-sectional training cohort of people with Parkinson's disease, multiple system atrophy, dementia with Lewy bodies, Alzheimer's disease, or other neurological disorders; a group of patients with autopsy-confirmed dementia with Lewy bodies, Alzheimer's disease, or other neurological disorders (CSF specimens were drawn ante mortem during clinical investigations); and a validation cohort of patients who between January, 2003, and December, 2006, were referred to a specialised movement disorder hospital for routine inpatient admission under the working diagnosis of parkinsonism. CSF and serum samples were assessed by ELISA, and clinical diagnoses were made according to internationally established criteria. Mean differences in biomarkers between diagnostic groups were assessed with conventional parametric and non-parametric statistics.

FINDINGS

In our training set, people with Parkinson's disease, multiple system atrophy, and dementia with Lewy bodies had lower CSF α-synuclein concentrations than patients with Alzheimer's disease and other neurological disorders. CSF α-synuclein and tau values separated participants with synucleinopathies well from those with other disorders (p<0·0001; area under the receiver operating characteristic curve [AUC]=0·908). In the autopsy-confirmed cases, CSF α-synuclein discriminated between dementia with Lewy bodies and Alzheimer's disease (p=0·0190; AUC=0·687); in the validation cohort, CSF α-synuclein discriminated Parkinson's disease and dementia with Lewy bodies versus progressive supranuclear palsy, normal-pressure hydrocephalus, and other neurological disorders (p<0·0001; AUC=0·711). Other predictor variables tested in this cohort included CSF tau (p=0·0798), serum α-synuclein (p=0·0502), and age (p=0·0335). CSF α-synuclein concentrations of 1·6 pg/μL or lower showed 70·72% sensitivity (95% CI 65·3-76·1%) and 52·83% specificity (39·4-66·3%) for the diagnosis of Parkinson's disease. At this cutoff, the positive predictive value for any synucleinopathy was 90·7% (95% CI 87·3-94·2%) and the negative predictive value was 20·4% (13·7-27·2%).

INTERPRETATION

Mean CSF α-synuclein concentrations as measured by ELISA are significantly lower in Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy than in other neurological diseases. Although specificity was low, the high positive predictive value of CSF α-synuclein concentrations in patients presenting with synucleinopathy-type parkinsonism might be useful in stratification of patients in future clinical trials.

FUNDING

American Parkinson Disease Association, Stifterverband für die Deutsche Wissenschaft, Michael J Fox Foundation for Parkinson's Research, National Institutes of Health, Parkinson Research Consortium Ottawa, and the Government of Canada.