Martin Lauer

The human striatum in schizophrenia. II. Increased number of striatal neurons in schizophrenics.

In neuropathological studies of schizophrenia, alterations of the basal ganglia are one main topic. Using the optical dissector, we performed an unbiased estimation of neurons and glia cells in the human striatum. To rule out an influence of age and gender, the brains of 9 male schizophrenic patients younger than 65 were closely matched in age with the brains of 9 male control persons. Absolute neuron numbers of the striatum and its subdivisions putamen and nucleus caudatus/nucleus accumbens of both hemispheres were compared between both groups, as were absolute glia cell numbers and the calculated glia index. We found a significant increase in absolute striatal neuron numbers in the schizophrenic group on the right side (P = 0.008**) and only a trend to higher absolute striatal neuron numbers on the left side. In a further analysis, the significant increase of absolute striatal neuron numbers in the right striatum of the schizophrenic group was only discernible for the nucleus caudatus/nucleus accumbens complex (P = 0.01*) and not for the putamen. Absolute striatal glia cell numbers did not differ significantly between both groups, neither on the right nor on the left side. There was only a trend towards a smaller glia index on both sides. Cortical development disturbances with a consecutive reduction of naturally occurring cell death during development could be responsible for this increase in absolute striatal neuron numbers in schizophrenics.

Increased volume of the nucleus accumbens in schizophrenia

Summary. The nucleus accumbens, an integral and important part of limbic and prefrontal cortico-striato-pallidal-thalamic circuits, is involved in several cognitive, emotional and psychomotor functions altered in schizophrenia. In animal models, developmental disturbances within the entorhinal cortex and the hippocampus induce a dysregulation of inputs to the nucleus accumbens resulting in behavioral abnormalities which point to psychotic psychopathology. Nonetheless, due to the complex neuroanatomy of the human ventral striatum hardly any morphometric data on the nucleus accumbens are available.A postmortem stereological investigation of the nucleus accumbens was performed in complete brains of 9 male schizophrenics and 9 male controls between the ages of 46 and 64. Complete serial coronal slices of both hemispheres were stained with a modified Nissl-technique. Tissue shrinkage after staining and embedding was corrected for both individual and regional shrinkage. Based on recent precise delimitations of the human ventral striatum, in vivo hemisphere-adjusted volumes of the nucleus accumbens (volume densities) and absolute accumbal volumes were calculated applying the Cavalieri-estimator.In schizophrenics, mean hemisphere-adjusted volumes of the nucleus accumbens were significantly increased on both sides (right accumbens: p = 0,005**; left accumbens: p = 0,016*). Hemispherical volumes and volumes of the nucleus accumbens were significantly correlated in both groups (p = 0,02*).Most likely, this increase in volume of the ventral striatum reflects a decrease in naturally occuring cell death following prenatal cortical neurodevelopmental disturbances.

Increased frequency of dentate granule cells with basal dendrites in the hippocampal formation of schizophrenics.

In the hippocampal formation of schizophrenics, the detailed morphology of Golgi-impregnated granule cells was examined. These granule cells of the dentate gyrus are interposed between the rostral entorhinal cortex and the hippocampus proper. In these limbic regions significant cytoarchitectural alterations in schizophrenics are reported, giving rise to the concept of a prenatal limbic maldevelopment in schizophrenia. Compared to controls, the frequency of dentate granule cells with basal dendrites was significantly increased in schizophrenics [43% (+/-3)] vs. [22% (+/-2) in the control group]. In epilepsy, dentate granule cells of epileptic patients also develop basal dendrites, which is explained as an adaptive process of plasticity. Similarly, the hippocampal alterations described in schizophrenics could be the sequela of primary entorhinal cytoarchitectural alterations. Since the increase in basal dendrites seems to reflect a process of continuous plasticity, suggesting an increased rate of postnatal granule cell generation, the synthesis of a prenatal limbic maldevelopment with an ongoing process of plasticity might, therefore, supersede the hypothesis of a neurodegeneration in schizophrenia.

The human striatum in schizophrenia. I. Increase in overall relative striatal volume in schizophrenics

Postmortem volumetry of the human striatum and its subdivisions (putamen, n.caudatus, n.accumbens) was performed on serial coronal sections of complete hemispheres. Both hemispheres of 9 male schizophrenic patients younger than 65 years were closely matched in age with the hemispheres of 9 male control individuals. All obtained values were corrected with individual and region-specific shrinkage factors; the intrarater reliability was 1% difference in volume. The absolute striatal volume was significantly correlated with the volume of the hemisphere (r = 0.931; P = 0.0003***). Reflecting differences in the hemispheric volumes of the schizophrenic and the control group, the absolute striatal volume consequently did not differ between both groups (P > 0.55). However, we found a clear increase in the volume density (i.e. the relative striatal portion of the hemisphere; the relative striatal volume) in the schizophrenic group, highly significant on both sides (P = 0.003** for the right striatum, P = 0.002** for the left striatum). The increase in volume density concerned both the putamen (P = 0.003** for the right side) and the n.caudatus/n.accumbens (P = 0.01* for the right side). Discrepant volumetric results of previous authors who compared only absolute volume values in samples not matched for identical hemispheric volume could thus be explained by this high positive correlation with the hemispheric volume. Since exact matching for identical hemispheric volume is not feasible and examined groups will never be large enough to rule out the influence of the hemispheric volume, the determination of relative volumes (i.e. volume densities) seems to be advantageous for future volumetric studies.

Morphological abnormalities in nitric-oxide-synthase-positive striatal interneurons of schizophrenic patients.

Schizophrenia has been suggested to be a neurodevelopmental disorder, and nitric-oxide-synthase (NOS)-positive neurons were shown to be involved in distorted cortical development in schizophrenia. Here we investigated whether nitrinergic neurons in the striatum of schizophrenic patients also display abnormalities regarding distribution or morphology. To do so, postmortem putaminal sections of schizophrenic subjects were examined by means of nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) staining and NOS immunohistochemistry. NOS-positive neurons were counted and analyzed morphologically. Abnormalities regarding morphology or number of NOS-containing neurons could be found in the putamen of schizophrenics (n = 3), but not controls (n = 5). Neurons were either of abnormal size and branching pattern, or they were markedly reduced (130 ± 44 vs. 54 ± 62 NADPHd-positive somata/mm3 putamen; p < 0.0001). Striatal nitrinergic interneurons might thus be involved in the pathogenesis of at least some forms of schizophrenia. Studies on larger samples are however needed to further corroborate this finding.

Inhibitory cartridge synapses in the anterior cingulate cortex of schizophrenics

Summary. Axon cartridges are the specific terminal structures of GABAergic inhibitory chandelier interneurons. Cartridges form axo-axonal synapses with local projection neurons, thus modulating the neuronal output of diverse brain areas. In order to examine the distribution of cartridges, the anterior cingulate cortices from the brains of schizophrenic patients and control persons were examined with an antibody against parvalbumin. Axon cartridges were mainly located in layers V and VI. In our study, schizophrenic patients showed a significantly higher density of axon cartridges than controls. These findings add new evidence for disturbances of the circuitry of the anterior cingulate cortex in schizophrenia implicating that there may be an elevated inhibitory influence on the cortical output of this brain region.

Neurofilament as a blood marker for diagnosis and monitoring of primary progressive aphasias

Objective: To assess the utility of serum neurofilament for diagnosis and monitoring of primary progressive aphasia (PPA) variants. Methods: We investigated neurofilament light chain (NF-L) levels in blood of 99 patients with PPA (40 with nonfluent variant PPA [nfvPPA], 38 with semantic variant PPA [svPPA], 21 with logopenic variant PPA [lvPPA]) and compared diagnostic performance with that reached by CSF NF-L, phosphorylated neurofilament heavy chain (pNF-H), β-amyloid (Aβ1-42), tau, and phosphorylated tau. The longitudinal change of blood NF-L levels was measured and analyzed for correlation with functional decline and brain atrophy. Results: Serum NF-L is increased in PPA compared to controls and discriminates between nfvPPA/svPPA and lvPPA with 81% sensitivity and 67% specificity (cutoff 31 pg/mL). CSF NF-L, pNF-H, tau, phosphorylated tau, and Aβ1-42 achieved similar performance, and pNF-H was the only marker for discrimination of nfvPPA from svPPA/lvPPA. In most patients with nfvPPA and svPPA, but not lvPPA, serum NF-L increased within follow-up. The increase correlated with functional decline and progression of atrophy of the left frontal lobe of all patients with PPAs and the right middle frontal gyrus of patients with nfvPPA and svPPA. Conclusions: Blood level of NF-L can aid the differential diagnosis of PPA variants, especially in combination with CSF pNF-H. Because serum NF-L correlates with functional decline and atrophy in the disease course, it qualifies as an objective disease status marker. Extended follow-up studies with cases of known neuropathology are imperative. Classification of evidence: This study provides Class I evidence that in patients with PPA, blood levels of NF-L can distinguish the logopenic variant from the nonfluent/agrammatic and semantic variants.

NADPH-diaphorase staining reveals new types of interneurons in human putamen

Neurons in the human striatum have been divided into five or seven different types, respectively. To further characterize these interneurons, we investigated the putamen of five brains by means of NADPH-diaphorase staining and compared our results to previous classifications in man. The NADPH-diaphorase method is selective for nitric oxide synthase (NOS); in the human striatum, predominantly interneurons were stained. NADPH-diaphorase positive neurons were then further examined. They showed clear morphological differences and could be classified into 12 different types, which only partially corresponded to previously described neuron types. Thus, we suggest at least three novel types of neostriatal interneurons. Furthermore, a special class of large neurons thought to be efferent in nature, stained NOS-positive.

Poly-GP in cerebrospinal fluid links C9orf72-associated dipeptide repeat expression to the asymptomatic phase of ALS/FTD.

The C9orf72 GGGGCC repeat expansion is a major cause of amyotrophic lateral sclerosis and frontotemporal dementia (c9ALS/FTD). Non‐conventional repeat translation results in five dipeptide repeat proteins (DPRs), but their clinical utility, overall significance, and temporal course in the pathogenesis of c9ALS/FTD are unclear, although animal models support a gain‐of‐function mechanism. Here, we established a poly‐GP immunoassay from cerebrospinal fluid (CSF) to identify and characterize C9orf72 patients. Significant poly‐GP levels were already detectable in asymptomatic C9orf72 mutation carriers compared to healthy controls and patients with other neurodegenerative diseases. The poly‐GP levels in asymptomatic carriers were similar to symptomatic c9ALS/FTD cases. Poly‐GP levels were not correlated with disease onset, clinical scores, and CSF levels of neurofilaments as a marker for axonal damage. Poly‐GP determination in CSF revealed a C9orf72 mutation carrier in our cohort and may thus be used as a diagnostic marker in addition to genetic testing to screen patients. Presymptomatic expression of poly‐GP and likely other DPR species may contribute to disease onset and thus represents an alluring therapeutic target.

Dendritic excrescences seem to characterize hippocampal CA3 pyramidal neurons in humans

Summary.Excrescences are unique dendritic postsynaptic structures of the hippocampal formation. Only CA3 pyramidal neurones and hilar mossy cells possess these complex dendritic structures. Dendritic excrescences have so far only been investigated in rabbit, rat and rhesus monkey. Applying a Golgi impregnation method optimized for human brain tissue, we describe the detailed morphology of excrescences of CA3 pyramidal neurons of man.Human thorny excrescences possess a thin and single spine neck and multiple spine heads (4 on average, sometimes more than 10). Human cluster excrescences sit upon the dendrite with a broad stem, and exhibit a “papilloma-like” surface. Some human CA3 pyramidal neurons seem to possess markedly longer spine necks and larger spine heads compared to human neocortical pyramid cells; they were named long-neck spines. Thorny excrescences, cluster excrescences and the newly described long-neck spines can also be found on the dendritic main stem of human CA3 pyramidal neurons.CA2 pyramidal neurons neither possess these long neck spines nor thorny or cluster excrescences. Thus, the unique excrescences of CA3 pyramidal neurones seem to be another criterion for a demarcation between the CA3- and CA2 region of the human hippocampus.