Glial tangles in Pick's disease

Cellular tau pathology and immunohistochemical study of tau isoforms in sporadic tauopathies

Pathological inclusions in neurons and glial cells containing fibrillary aggregates of abnormally hyperphosphorylated tau protein are characteristic features in sporadic tauopathies. In the first part of this paper we outline the morphological features of some major sporadic tauopathies. In the second part, to better define the tau isoform composition, we report on the immunohistochemistry of tau isoforms in autopsied brains, including two cases with AD, two with diffuse neurofibrillary tangles with calcification, four with Pick's disease with Pick bodies (PiD), seven with progressive supranuclear palsy (PSP), six with corticobasal degeneration (CBD) and seven cases with argyrophilic grain disease. We used two monoclonal antibodies, RD3 and RD4, and a polyclonal antibody for exon 10 that effectively distinguish between three-repeat (3R) tau and four-repeat (4R) tau. Neuronal neurofibrillary tangles (NFT) in AD and diffuse neurofibrillary tangles with calcification contained both 3R-tau and 4R-tau. The Pick bodies were immunopositive for 3R-tau in two cases; however, in two other cases they were mainly immunopositive for 4R-tau. Thus, Pick bodies demonstrated heterogeneity. 3R-tau PiD contained 3R-tau glial inclusions, and 4R-tau PiD contained mainly 4R-tau glial inclusions. Glial inclusions were more abundant in 4R-tau PiD cases. In progressive supranuclear palsy and CBD, both neuronal and glial tau accumulation forming NFF, pretangles, tuft-shaped astrocytes, astrocytic plaques, coiled bodies and threads demonstrated 4R-tau in the cerebral cortices, although in the basal ganglia and brainstem neuronal and glial inclusions were occasionally immunopositive for 3R-tau in addition to 4R-tau. Argyrophilic grains (AG) were immunopositive for 4R-tau, although pretangles were weakly stained for 4R-tau. Thus the immunoreactivity for 4R-tau was different between AG and pretangles. Therefore, the isoform composition on immunohistochemical study showed heterogeneity in PiD, and was not uniform in the basal ganglia and brain stem in PSP and CBD. It is suggested that the isoform composition of sporadic tauopathies may have a spectrum in individual cases, and cellular isoform composition may differ in various brain regions.

Tau-positive glial inclusions in progressive supranuclear palsy, corticobasal degeneration and Pick's disease

The presence of tau-positive glial inclusions has been recently found a consistent feature in the brains of patients with progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and Pick's disease (PiD). These inclusions are classified based on cellular origin as tau-positive astrocytes, presumably either fibrillary or protoplasmic, coiled bodies and glial threads. Immunohistochemically, their major structural component is abnormal tau proteins, similar to those found in Alzheimer's disease. Nevertheless, their morphology, including ultrastructural profile, has been suggested to be distinctive for each disease. The profile and extent of particular glial inclusions correlate well with disease phenotype. Highly characteristic correlations include tufts of abnormal fibers in PSP, astrocytic plaques and dense glial threads in CBD and ramified astrocytes and small Pick body-like inclusions in PiD. The significance of the inclusions in disease pathogenesis and their biochemical characteristics remain to be clarified. Nevertheless, these distinctive glial lesions most likely reflect fundamental alterations in isoform composition of tau as well as its specific cellular and regional expression in sporadic tauopathies.

Tuft-shaped astrocytes in Lewy body disease

We investigated the occurrence and distribution of tuft-shaped astrocytes (TuSAs) in 60 brains from patients with Lewy body disease (LBD), which were clinically diagnosed as Parkinson's disease (PD) or dementia with Lewy bodies (DLB), and 85 brains from control subjects. TuSAs have been documented as a neuropathological hallmark of progressive supranuclear palsy (PSP). We found phosphorylated tau (p-tau)-positive and alpha-synuclein-negative TuSAs in 10 of 60 patients with LBD and 3 of 85 control cases. TuSAs were mainly located within the precentral and premotor gyri of the frontal lobe cortex. There were only few TuSAs, but the distribution pattern and morphological and immunohistological features were similar to that in PSP. Furthermore, other p-tau positive structures, including aggregates in neurons, coiled-like glial cells and threads showed a similar distribution to those in PSP; mainly in the hippocampus, striatum, subthalamic nucleus, precentral and premotor gyri, brainstem nucleus, and dentate nucleus. In these cases, however, neuronal loss and gliosis were not seen in the regions involved in PSP, such as the subthalamic nucleus, pallidum, inferior olivary, cerebellar dentate nuclei, and periaqueductal gray matter. Clinical features were indistinguishable between the LBD with and without TuSAs. The appearance of TuSAs was not related to the frequency of Lewy bodies, neurofibrillary tangles, and senile plaques, but was significantly more pronounced with advancing age in both LBD and controls. These findings suggest that in a subgroup of elderly individual cases, especially associated with LB pathology, the glial and neuronal p-tau accumulation is increased and has a distributional pattern similar to PSP.

Degeneration of Pick bodies visualized by methenamine-silver staining and immunohistochemistry

The degeneration process of Pick's bodies (PB) was investigated using methenamine-silver (MS) staining and immunohistochemistry. Methenamine-silver staining sensitively detected extracellular PB as well as intracellular PB in the granular cell layer of the dentate gyrus. Extracellular PB appeared as granular masses with ill-defined boundaries in the neuropil. For MS electron microscopy, the extracellular PB were composed of randomly oriented fibrillary components measuring 9-12 nm in diameter with astroglial processes and degenerated organelles. Tau immunoreactivity of extracellular PB was reduced or abolished. These findings indicate that MS staining is a convenient method for detecting extracellular PB. In addition, it was shown that microglial involvement was associated with PB-bearing neurons at the late stage of the degeneration process and that extracellular PB remained in the neuropil with astroglial reaction.

An autopsy case of postencephalitic parkinsonism of von Economo type: some new observations concerning neurofibrillary tangles and astrocytic tangles

An autopsied case of postencephalitic parkinsonism of von Economo type with a 71-year duration is reported. Several cases of postencephalitic parkinsonism of von Economo type have been reported in Japan but this is the first reported case from western Japan. The patient was a Japanese man who was 74 years of age at the time of death. He developed encephalitis of unknown etiology at the age of 3 years. The first symptom was antisocial behavior, which developed at 30 years of age. At the age of 40 years, the patient showed progressive parkinsonism. Neuropathological findings disclosed marked neuronal loss with gliosis in the substantia nigra, locus ceruleus, and raphe nuclei, as well as the appearance of neurofibrillary tangles in the aforementioned areas. There were also widespread tuft-shaped astrocytes (Tu-SA) in the central nervous system, including the thalamus. Tuft-shaped astrocytes are considered to represent non-reactive astrocytes because the distributions of neurofibrillary tangles (NFT) and Tu-SA are clearly different. Therefore, the primary astrocytic lesions in postencephalitic parkinsonism of von Economo type may be more widespread. Ultrastructurally, the Tu-SA consisted of straight filaments, 15 nm in width, which formed tight bundles. Ultrastructurally, NFF in this case revealed paired helical filaments but straight filaments, 15 nm in width, which were also found in the neurons of the substantia nigra.

Recent advances in dementia research in Japan: non-Alzheimer-type degenerative dementias

In this article, we review recent reports by Japanese researchers on non-Alzheimer-type degenerative dementias. These dementias can be classified into the following subtypes: dementias with Lewy bodies, including diffuse Lewy body disease, dementias with neurofibrillary tangles, dementias with glial tangles, including progressive supranuclear palsy and corticobasal degeneration, argyrophilic grain dementia, frontotemporal dementias including Pick's disease; dementias with degeneration of subcortical nuclei, including Huntington's disease and, last, unclassified dementias. Recently, these various forms of dementia have received much attention in Japan, as elsewhere.