STochastic Optical Reconstruction Microscopy (STORM) reveals the nanoscale organization of pathological aggregates in human brain

AIMS

Histological analysis of brain tissue samples provides valuable information about the pathological processes leading to common neurodegenerative disorders. In this context, the development of novel high-resolution imaging approaches is a current challenge in neuroscience.

METHODS

To this end, we used a recent super-resolution imaging technique called STochastic Optical Reconstruction Microscopy (STORM) to analyse human brain sections. We combined STORM cell imaging protocols with neuropathological techniques to image cryopreserved brain samples from control subjects and patients with neurodegenerative diseases.

RESULTS

This approach allowed us to perform 2D-, 3D- and two-colour-STORM in neocortex, white matter and brainstem samples. STORM proved to be particularly effective at visualizing the organization of dense protein inclusions and we imaged with a <50 nm resolution pathological aggregates within the central nervous system of patients with Alzheimer's disease, Parkinson's disease, Lewy body dementia and fronto-temporal lobar degeneration. Aggregated Aβ branches appeared reticulated and cross-linked in the extracellular matrix, with widths from 60 to 240 nm. Intraneuronal Tau and TDP-43 inclusions were denser, with a honeycomb pattern in the soma and a filamentous organization in the axons. Finally, STORM imaging of α-synuclein pathology revealed the internal organization of Lewy bodies that could not be observed by conventional fluorescence microscopy.

CONCLUSIONS

STORM imaging of human brain samples opens further gates to a more comprehensive understanding of common neurological disorders. The convenience of this technique should open a straightforward extension of its application for super-resolution imaging of the human brain, with promising avenues to current challenges in neuroscience.

Cognitive deficit, and neuropathological correlates, in the oldest-old

Several disorders are usually involved in the cognitive deficit of the oldest old. Alzheimer disease is the commonest. It is usually characterized by progressive memory impairment - neocortical symptoms occurring much later in the course of the disease. Alzheimer disease should not be considered any more as the single cause of a cognitive deficit in a very old patient. Vascular alterations, possibly causing microinfarcts, are commonly associated, especially in cerebral amyloid angiopathy. A slowly progressive memory deficit with negative CSF biomarkers of Alzheimer's disease may be due to hippocampal sclerosis that may be the consequence of multiple causes: in most of the cases, it is associated with neuronal TDP-43 inclusions. Recently, a distribution of these inclusions to a territory more extensive than the hippocampus has been reported and attributed to a new entity, called Limbic-predominant Age-related TDP-43 Encephalopathy (LATE) with or without hippocampal sclerosis. The presence of cortical Lewy bodies may cause an intellectual deficit or contribute to it. The prevalence of dementia with cortical Lewy bodies in the oldest old is discussed. Tau inclusions in cortical glia have also been shown to participate to the intellectual deficit. Association of neurodegenerative and vascular changes is the most frequent situation in the very old patients. Systemic diseases such as diabetes or heart failure, prescription drugs (when misused), or toxic such as alcohol may also contribute to the cognitive impairment and be amenable to treatment.

Modifications of the endosomal compartment in peripheral blood mononuclear cells and fibroblasts from Alzheimer's disease patients

Identification of blood-based biomarkers of Alzheimer's disease (AD) remains a challenge. Neuropathological studies have identified enlarged endosomes in post-mortem brains as the earliest cellular change associated to AD. Here the presence of enlarged endosomes was investigated in peripheral blood mononuclear cells from 48 biologically defined AD patients (25 with mild cognitive impairment and 23 with dementia (AD-D)), and 23 age-matched healthy controls using immunocytochemistry and confocal microscopy. The volume and number of endosomes were not significantly different between AD and controls. However, the percentage of cells containing enlarged endosomes was significantly higher in the AD-D group as compared with controls. Furthermore, endosomal volumes significantly correlated to [C(11)]PiB cortical index measured by positron emission tomography in the AD group, independently of the APOE genotype, but not to the levels of amyloid-beta, tau and phosphorylated tau measured in the cerebrospinal fluid. Importantly, we confirmed the presence of enlarged endosomes in fibroblasts from six unrelated AD-D patients as compared with five cognitively normal controls. This study is the first, to our knowledge, to report morphological alterations of the endosomal compartment in peripheral cells from AD patients correlated to amyloid load that will now be evaluated as a possible biomarker.

Sicca syndrome and dementia in a patient with hepatitis C infection: a case report with unusual bifocal extrahepatic manifestations

INTRODUCTION

Hepatitis C virus (HCV) infections are associated with extrahepatic manifestations in 40-75 % of cases. Sialitis and secondary Sjögren syndrome are well characterized complications of chronic HCV infections but the mechanisms (primary or secondary) leading to xerostomia are not understood. Similarly, brain lesions due to HCV can be primary or secondary but the pathology of primary HCV-related brain lesions is not well described.

CASE REPORT

We report the postmortem case of a 60-year old patient initially presenting with sicca syndrome and dementia. HCV was identified in the brain but not in the salivary glands using transcription-mediated amplification (TMA). Focal sialitis was found in submandibular glands. Neuropathological examination revealed the presence of multiple dot-sized demyelination foci.

CONCLUSION

Sicca syndrome is a common concern in chronic HCV infections and may be due to secondary immune mechanisms (we could not isolate HCV in salivary gland tissues). TMA had never been applied to the detection of viruses in salivary glands and neural tissues and proves to be a promising technique. Neuropathological reports in HCV infections are rare and the lesions we report may be the first characterization of the direct effect of HCV on brain cells. More cases are needed to define the full spectrum of lesions potentially caused by the direct action of the HCV on salivary glands and neural tissues.

Neurodegenerative lesions: seeding and spreading

Accumulation of specific proteins has replaced loss of specific populations of neurons in the definition of most neurodegenerative diseases. In some cases, the amino-acid sequence of the protein that accumulates is altered by a mutation in the gene that codes for it but most generally, the primary structure is normal. Much evidence from human neuropathology has been collected over the years indicating that the progression of the lesions in such neurodegenerative diseases as Alzheimer's disease, Parkinson's disease and progressive supranuclear palsy follow the neuroanatomical connections. More recently, injection of aggregates of the specific proteins in the brain of experimental animals has been attempted in various experimental settings. Brain homogenates containing Aβ aggregates induce the early development of Aβ deposits in APP transgenic mice. Brain homogenates from various human tauopathies induce tau aggregates in transgenic mice expressing normal human tau. Finally, synthetic preformed fibrils of alpha-synuclein initiate the development of alpha-synuclein accumulation resembling Parkinson's disease in wild-type mice. Experiments in cell cultures suggest that the protein has to be in some specific state of oligomerization or fibrillation to be endocytosed and transported by the neuron. These data suggest that the protein that accumulates in a specific disease is initially misfolded and that this misfolding contaminates normal protein in a prion-like manner - in some cases through the neuronal connections.

Prevalence of nephroangiosclerosis in patients with fatal stroke

BACKGROUND

Glomerular filtration rate and decline in renal function can be improved by global cardiovascular prevention. However, the prevalence of nephroangiosclerosis in patients with stroke is unknown.

METHODS

Using an autopsy data bank, we studied the prevalence of nephroangiosclerosis in 820 consecutive autopsies of neurologic patients.

RESULTS

Among the 820 autopsies, 354 had pathologic evidence of stroke and 466 had other neurologic diseases. Nephroangiosclerosis was found in 39.8% (95% confidence interval [CI], 34.7-44.9) of patients with stroke vs 9.0% (95% CI, 6.4-11.6) in patients with other neurologic diseases. The odds ratio (OR) for nephroangiosclerosis, adjusted for age and sex, was 4.37 (95% CI, 2.92-6.52), and was 2.94 (95% CI, 1.83-4.74) after further adjustment for cardiovascular risk factors. Among the 354 stroke patients, the prevalence of nephroangiosclerosis was similar in patients with brain infarction and in those with brain hemorrhage, in patients with or without parenchymal abnormalities related to small-vessel disease, and across ischemic stroke subtypes except for those with coexisting causes. After multivariable analysis, nephroangiosclerosis was independently associated with age and history of hypertension in patients with stroke, and with age in those with other neurologic diseases.

CONCLUSIONS

Nephroangiosclerosis is common in patients with fatal stroke. The association is independent of age, sex, and other cardiovascular risk factors. Impaired renal function should be monitored and prevented in stroke patients with high blood pressure.

[Morphologic and molecular neuropathology of Alzheimer's disease]

Alzheimer disease lesions include the abnormal accumulation of two proteins normally present in neurons: tau protein and Abeta peptide. Tau protein aggregates into fibrils in the cell body of neurons (neurofibrillary tangles), in dendrites (neuropil threads) and in degenerating axons that constitute the corona of the senile plaque. Tau pathology progresses in the brain areas in a stereotyped manner and in parallel with the clinical symptoms. Abeta extracellular deposits may be diffuse or focal. The Abeta focal deposit constitutes the core of the senile plaque. Progression of the Abeta lesions, which initially affect the isocortex, then the hippocampus, basal ganglia, various brainstem nuclei and cerebellum, is not directly correlated with symptoms. Mutations involving the genes implicated in Abeta peptide metabolism are responsible for familial Alzheimer disease. Mutations of the tau gene are not associated with Alzheimer disease but with frontotemporal dementia. The link between altered Abeta peptide metabolism and tau pathology has not been fully elucidated. Animal models mimic several aspects of the disease and have contributed to a better understanding of the mechanisms of the lesions.

Clinical and neuropathologic study of a French family with a mutation in the neuroserpin gene

Familial encephalopathy with neuroserpin inclusion bodies is a recently described neurodegenerative disease that is responsible for progressive myoclonic epilepsy or presenile dementia. In a French family with the S52R mutation of the neuroserpin gene, progressive myoclonic epilepsy was associated with a frontal syndrome. The typical cerebral inclusions (Collins bodies) were abundant in the frontal cortex and in the head of the caudate nucleus but spared the cerebellum.

Mutations in the SPG3A gene encoding the GTPase atlastin interfere with vesicle trafficking in the ER/Golgi interface and Golgi morphogenesis

Mutations in SPG3A causing autosomal dominant pure spastic paraplegia led to identification of atlastin, a new dynamin-like large GTPase. Atlastin is localized in the endoplasmic reticulum, the Golgi, neurites and growth cones and has been implicated in neurite outgrowth. To investigate whether it exerts its activity in the early secretory system, we expressed normal and mutant atlastin in cell culture. Pathogenic mutations in the GTPase domain interfered with the maturation of Golgi complexes by preventing the budding of vesicles from the endoplasmic reticulum, whereas mutations in other regions of the protein disrupted fission of endoplasmic reticulum-derived vesicles or their migration to their Golgi target. Atlastin, therefore, plays a role in vesicle trafficking in the ER/Golgi interface. Furthermore, atlastin partially co-localized with proteins of the p24/emp/gp25L family that regulate vesicle budding and trafficking in the early secretory pathway, and co-immunoprecipitated p24, suggesting a functional relationship that should be further explored.

[Nosology of dementias: the neuropathologist's point of view]

The diagnosis of degenerative dementias heavily relies on the identification of neuronal or glial inclusions. Tauopathy is probably the largest group including Alzheimer and Pick disease, mutation of the tau gene, progressive supranuclear palsy, corticobasal degeneration, and argyrophilic grain disease. Lewy bodies, when numerous in the cerebral cortex, are usually associated with the cognitive deficit of Parkinson disease dementia or of dementia with Lewy bodies--both conditions being distinguished by clinical information. The inclusions of the dentate gyrus, only labeled by anti-ubiquitin antibodies, isolate a subgroup of fronto-temporal dementia (FTDu), sometimes familial and sometimes associated with amyotrophic lateral sclerosis. Mutations of the progranulin gene have been recently discovered among a significant proportion of these patients. Neuronal Intermediate Filament Inclusion Disease (NIFID) is a rare, apparently sporadic dementia, characterized by the presence of large inclusions in the cell body of many neurons. These inclusions react with antibodies directed against neurofilaments or against other intermediate filaments (such as alpha-internexin). The diagnostic value of some of these inclusions allowing the classification of the degenerative dementias has been discussed. The link between the inclusions and the pathogenetic mechanism is indeed probably variable. It should however be stressed that whenever their composition has been elucidated, the inclusions have given important clues to the pathogenesis of the disease in which they had been found.

Valosin-containing protein gene mutations: clinical and neuropathologic features

BACKGROUND

Hereditary inclusion body myopathy (IBMPFD) with Paget disease of bone (PDB) and frontotemporal dementia (FTD) is a rare multisystem disorder with autosomal dominant inheritance. Recently, missense mutations in the gene encoding valosin-containing protein (VCP) have been found in individuals with IBMPFD. VCP/P97, which exerts a variety of cellular functions, plays a key role in the ubiquitin-proteasome dependent degradation of cytosolic proteins and in the retrotranslocation of misfolded proteins from the endoplasmic reticulum into the cytoplasm.

METHODS

The authors describe the clinical features of two kindreds in which VCP R93C and R155C missense mutations segregate and perform a histopathologic examination of brain, muscle, bone, and liver of three subjects harboring the R155C mutation.

RESULTS

Frontotemporal dementia was present in 100% of affected subjects in Family F1 and 70% in Family F2, as compared with an average of 30% in previously described IBMPFD families. In contrast, PDB was a more inconstant clinical feature. Biochemical and histopathologic data are consistent with the hypothesis that VCP R155C mutation disrupts normal VCP function, leading to diffuse accumulation of ubiquitinated proteins within the cells.

CONCLUSIONS

VCP mutations are present in two families in which FTD is the most prominent symptom. The histopathologic study performed in patients harboring the R155C mutation supports the hypothesis that this mutation disrupts normal VCP function, leading to diffuse accumulation of ubiquitinated proteins within the cells. IBMPFD belongs to a class of genetic diseases associated with an alteration of the ubiquitin-proteasome system.

Clinical and neuropathologic variation in neuronal intermediate filament inclusion disease

BACKGROUND

Recently described neuronal intermediate filament inclusion disease (NIFID) shows considerable clinical heterogeneity.

OBJECTIVE

To assess the spectrum of the clinical and neuropathological features in 10 NIFID cases.

METHODS

Retrospective chart and comprehensive neuropathological review of these NIFID cases was conducted.

RESULTS

The mean age at onset was 40.8 (range 23 to 56) years, mean disease duration was 4.5 (range 2.7 to 13) years, and mean age at death was 45.3 (range 28 to 61) years. The most common presenting symptoms were behavioral and personality changes in 7 of 10 cases and, less often, memory loss, cognitive impairment, language deficits, and motor weakness. Extrapyramidal features were present in 8 of 10 patients. Language impairment, perseveration, executive dysfunction, hyperreflexia, and primitive reflexes were frequent signs, whereas a minority had buccofacial apraxia, supranuclear ophthalmoplegia, upper motor neuron disease (MND), and limb dystonia. Frontotemporal and caudate atrophy were common. Histologic changes were extensive in many cortical areas, deep gray matter, cerebellum, and spinal cord. The hallmark lesions of NIFID were unique neuronal IF inclusions detected most robustly by antibodies to neurofilament triplet proteins and alpha-internexin.

CONCLUSION

NIFID is a neuropathologically distinct, clinically heterogeneous variant of frontotemporal dementia (FTD) that may include parkinsonism or MND. Neuronal IF inclusions are the neuropathological signatures of NIFID that distinguish it from all other FTD variants including FTD with MND and FTD tauopathies.