Prolonged fixation and post-mortem delay impede the study of adult neurogenesis in mice.

Adult hippocampal neurogenesis (AHN) gives rise to new neurons throughout life. This phenomenon takes place in more than 120 mammalian species, including humans, yet its occurrence in the latter was questioned after one study proposed the putative absence of neurogenesis markers in the adult human hippocampus. In this regard, we showed that prolonged fixation impedes the visualization of Doublecortin+ immature neurons in this structure, whereas other authors have suggested that a dilated post-mortem delay (PMD) underlies these discrepancies. Nevertheless, the individual and/or additive contribution of fixation and the PMD to the detection (or lack thereof) of other AHN markers has not been studied to date. To address this pivotal question, we used a tightly controlled experimental design in mice, which allowed the dissection of the relative contribution of the aforementioned factors to the visualization of markers of individual AHN stages. Fixation time emerged as the most prominent factor globally impeding the study of this process in mice. Moreover, the visualization of other particularly sensitive epitopes was further prevented by prolonged PMD. These results are crucial to disambiguate current controversies related to the occurrence of AHN not only in humans but also in other mammalian species.

Progression of Alzheimer's disease parallels unusual structural plasticity of human dentate granule cells.

Alzheimer´s disease (AD), the most common form of dementia in industrialized countries, severely targets the hippocampal formation in humans and mouse models of this condition. The adult hippocampus hosts the continuous addition of new dentate granule cells (DGCs) in numerous mammalian species, including humans. Although the morphology and positioning of DGCs within the granule cell layer (GCL) match their developmental origin in rodents, a similar correlation has not been reported in humans to date. Our data reveal that DGCs located in inner portions of the human GCL show shorter and less complex dendrites than those found in outer portions of this layer, which are presumably generated developmentally. Moreover, in AD patients, DGCs show early morphological alterations that are further aggravated as the disease progresses. An aberrantly increased number of DGCs with several primary apical dendrites is the first morphological change detected in patients at Braak-Tau I/II stages. This alteration persists throughout AD progression and leads to generalized dendritic atrophy at late stages of the disease. Our data reveal the distinct vulnerability of several morphological characteristics of DGCs located in the inner and outer portions of the GCL to AD and support the notion that the malfunction of the hippocampus is related to cognitive impairments in patients with AD.

Response to Comment on "Impact of neurodegenerative diseases on human adult hippocampal neurogenesis".

Rakic and colleagues challenge the use of extensively validated adult hippocampal neurogenesis (AHN) markers and postulate an alternative interpretation of some of the data included in our study. In Terreros-Roncal et al., reconstruction of the main stages encompassed by human AHN revealed enhanced vulnerability of this phenomenon to neurodegenerative diseases. Here, we clarify points and ambiguities raised by these authors.

Response to Comment on "Impact of neurodegenerative diseases on human adult hippocampal neurogenesis".

Alvarez-Buylla and colleagues provide an alternative interpretation of some of the data included in our manuscript and question whether well-validated markers of adult hippocampal neurogenesis (AHN) are related to this phenomenon in our study. In Terreros-Roncal et al., reconstruction of the main stages of human AHN revealed its enhanced vulnerability to neurodegeneration. Here, we clarify ambiguities raised by these authors.

Impact of neurodegenerative diseases on human adult hippocampal neurogenesis.

Disrupted hippocampal performance underlies psychiatric comorbidities and cognitive impairments in patients with neurodegenerative disorders. To understand the contribution of adult hippocampal neurogenesis (AHN) to amyotrophic lateral sclerosis, Huntington's disease, Parkinson's disease, dementia with Lewy bodies, and frontotemporal dementia, we studied postmortem human samples. We found that adult-born dentate granule cells showed abnormal morphological development and changes in the expression of differentiation markers. The ratio of quiescent to proliferating hippocampal neural stem cells shifted, and the homeostasis of the neurogenic niche was altered. Aging and neurodegenerative diseases reduced the phagocytic capacity of microglia, triggered astrogliosis, and altered the microvasculature of the dentate gyrus. Thus, enhanced vulnerability of AHN to neurodegeneration might underlie hippocampal dysfunction during physiological and pathological aging in humans.

Cannabinoid receptor CB2 ablation protects against TAU induced neurodegeneration.

Tauopathies are a group of neurodegenerative diseases characterized by the alteration/aggregation of TAU protein, for which there is still no effective treatment. Therefore, new pharmacological targets are being sought, such as elements of the endocannabinoid system (ECS). We analysed the occurrence of changes in the ECS in tauopathies and their implication in the pathogenesis. By integrating gene expression analysis, immunofluorescence, genetic and adeno-associated virus expressing TAU mouse models, we found a TAU-dependent increase in CB2 receptor expression in hippocampal neurons, that occurs as an early event in the pathology and was maintained until late stages. These changes were accompanied by alterations in the endocannabinoid metabolism. Remarkably, CB2 ablation in mice protects from neurodegeneration induced by hTAUP301L overexpression, corroborated at the level of cognitive behaviour, synaptic plasticity, and aggregates of insoluble TAU. At the level of neuroinflammation, the absence of CB2 did not produce significant changes in concordance with a possible neuronal location rather than its classic glial expression in these models. These findings were corroborated in post-mortem samples of patients with Alzheimer's disease, the most common tauopathy. Our results show that neurons with accumulated TAU induce the expression of the CB2 receptor, which enhances neurodegeneration. These results are important for our understanding of disease mechanisms, providing a novel therapeutic strategy to be investigated in tauopathies.

Sphingomyelin-induced inhibition of the plasma membrane calcium ATPase causes neurodegeneration in type A Niemann-Pick disease.

Niemann-Pick disease type A (NPA) is a rare lysosomal storage disorder characterized by severe neurological alterations that leads to death in childhood. Loss-of-function mutations in the acid sphingomyelinase (ASM) gene cause NPA, and result in the accumulation of sphingomyelin (SM) in lysosomes and plasma membrane of neurons. Using ASM knockout (ASMko) mice as a NPA disease model, we investigated how high SM levels contribute to neural pathology in NPA. We found high levels of oxidative stress both in neurons from these mice and a NPA patient. Impaired activity of the plasma membrane calcium ATPase (PMCA) increases intracellular calcium. SM induces PMCA decreased activity, which causes oxidative stress. Incubating ASMko-cultured neurons in the histone deacetylase inhibitor, SAHA, restores PMCA activity and calcium homeostasis and, consequently, reduces the increased levels of oxidative stress. No recovery occurs when PMCA activity is pharmacologically impaired or genetically inhibited in vitro. Oral administration of SAHA prevents oxidative stress and neurodegeneration, and improves behavioral performance in ASMko mice. These results demonstrate a critical role for plasma membrane SM in neuronal calcium regulation. Thus, we identify changes in PMCA-triggered calcium homeostasis as an upstream mediator for NPA pathology. These findings can stimulate new approaches for pharmacological remediation in a disease with no current clinical treatments.

Human DNA methylomes of neurodegenerative diseases show common epigenomic patterns.

Different neurodegenerative disorders often show similar lesions, such as the presence of amyloid plaques, TAU-neurotangles and synuclein inclusions. The genetically inherited forms are rare, so we wondered whether shared epigenetic aberrations, such as those affecting DNA methylation, might also exist. The studied samples were gray matter samples from the prefrontal cortex of control and neurodegenerative disease-associated cases. We performed the DNA methylation analyses of Alzheimer's disease, dementia with Lewy bodies, Parkinson's disease and Alzheimer-like neurodegenerative profile associated with Down's syndrome samples. The DNA methylation landscapes obtained show that neurodegenerative diseases share similar aberrant CpG methylation shifts targeting a defined gene set. Our findings suggest that neurodegenerative disorders might have similar pathogenetic mechanisms that subsequently evolve into different clinical entities. The identified aberrant DNA methylation changes can be used as biomarkers of the disorders and as potential new targets for the development of new therapies.

Peripherally triggered and GSK-3ß-driven brain inflammation differentially skew adult hippocampal neurogenesis, behavioral pattern separation and microglial activation in response to ibuprofen.

Both familial and sporadic forms of Alzheimer disease (AD) present memory impairments. It has been proposed that these impairments are related to inflammation in relevant brain areas such as the hippocampus. Whether peripherally triggered and neuron-driven brain inflammation produce similar and equally reversible alterations is a matter of discussion. Here we studied the effects of ibuprofen administration on a familial AD mouse model overexpressing GSK-3ß that presents severe brain inflammation. We compared these effects with those observed in a peripherally triggered brain inflammation model based on chronic lipopolysaccharide (LPS) administration. Both proinflammatory stimuli produced equivalent reversible morphological alterations in granule neurons; however, GSK-3ß had a much more prominent role in newborn neuron connectivity, causing alterations that were not reversed by ibuprofen. Although both insults triggered similar behavioral impairments, ibuprofen rescued this defect in LPS-treated mice but did not produce any improvement in GSK-3ß-overexpressing animals. This observation could be attributable to the different microglial phenotype induced by ibuprofen treatment. These data may be clinically relevant for AD therapies, as GSK-3ß appears to determine the efficacy of ibuprofen treatment.

Alzheimer's disease and disseminated mycoses.

Alzheimer's disease (AD) is characterized by the presence in the brain of amyloid plaques and neurofibrillary tangles that provoke neuronal cell death, vascular dysfunction and inflammatory processes. In the present work, we have analyzed the existence of fungal infection in AD patients. A number of tests have been carried out in blood serum, including the detection of antibodies against several yeast species and fungal proteins, and also the presence of fungal (1,3)-ß-glucan. Results from this analysis indicate that there is disseminated fungal infection in the majority of AD patients tested. Of interest, several AD patients contain high levels of fungal polysaccharides in peripheral blood, reflecting that disseminated fungal infection occurs in these patients. Together, these results suggest the presence of disseminated mycoses in blood serum from AD patients. To our knowledge these findings represent the first evidence that fungal infection is detectable in blood samples in AD patients. The possibility that this may represent a risk factor or may contribute to the etiological cause of AD is discussed.

Brain Donation by Proxy: Are There Predictors in Neurodegenerative Dementia?

OBJECTIVES: To describe the frequency and predictors of brain donation by relatives in patients with neurodegenerative dementia. DESIGN: Database review and quantitative analysis. SETTING: The Alzheimer Center Reina Sofia Foundation (ACRSF), a center devoted to the care and research of patients with neurodegenerative dementia. PARTICIPANTS: Patients with signed consent for participation in the ACRSF research program. MEASUREMENTS: A set of 38 demographic, clinical, and social variables related to patient and closest relative, which were collected by the ACRSF multidisciplinary team upon patient admission. RESULTS: Admission data were available for 198 patients who entered the ACRSF research program; 85 of them (42.9%) died during follow-up. Mean age (SD) at admission was 82.3 (6.8) years and 80.8% of the patients were female. Family link between patient and closest relative was spouse or partner (12.0%), son or daughter (74.9%), or other link (13.1%). Brain was obtained from 56 patients (65.9%). Consent by legal representative and patient's depressive symptoms were more frequent in the donors (p<0.05, corrected) and trend was observed for more aberrant motor symptoms in the donors (p<0.05, uncorrected). CONCLUSION: A high rate of brain donation was achieved, probably due to the unique characteristics of the ACRSF and consent for research policy. Wish of alleviating suffering, as well as general interest in dementia research, possibly exerted an influence in brain donation. More research is needed to ascertain the values, motivations, and circumstances that may lead to brain donation by proxy in neurodegenerative dementia.

GSK-3ß overexpression causes reversible alterations on postsynaptic densities and dendritic morphology of hippocampal granule neurons in vivo.

Adult hippocampal neurogenesis (AHN) is crucial for the maintenance of hippocampal function. Several neurodegenerative diseases such as Alzheimer's disease (AD) are accompanied by memory deficits that could be related to alterations in AHN. Here, we took advantage of a conditional mouse model to study the involvement of glycogen synthase kinase-3ß (GSK-3ß) overexpression (OE) in AHN. By injecting GFP- and PSD95-GFP-expressing retroviruses, we have determined that hippocampal GSK-3ß-OE causes dramatic alterations in both dendritic tree morphology and post-synaptic densities in newborn neurons. Alterations in previously damaged neurons were reverted by switching off the transgenic system and also by using a physiological approach (environmental enrichment) to increase hippocampal plasticity. Furthermore, comparative morphometric analysis of granule neurons from patients with AD and from GSK-3ß overexpressing mice revealed shared morphological alterations. Taken together, these data indicate that GSK-3ß is crucial for hippocampal function, thereby supporting this kinase as a relevant target for the treatment of AD.

[Usefulness of the 14-3-3 test for the diagnosis of sCJD evaluated by a Spanish reference center]. / Utilidad del inmunoensayo de la proteína 14-3-3 en el diagnóstico de la enfermedad de Creutzfeldt-Jakob examinada desde un centro de referencia nacional.

INTRODUCTION: The performance of the 14-3-3 protein test has been shown to be adequate for sporadic Creutzfeldt-Jakob disease (sCJD) diagnosis in selected populations, but its routine validity has been questioned. METHODS: One thousand and sixty-eight patients with clinically suspected sCJD were analyzed in a Spanish reference center. In order to explore the influence of the clinical context on the performance of the immunoassay, the patients were classified at sample reception according to the World Health Organization (WHO) diagnostic criteria excluding the 14-3-3 test results. The yield of the immunoassay was evaluated in each subgroup with criteria of probable, possible sCJD or non-sCJD. RESULTS: In the set of patients with suspicion of sCJD the inclusion of the 14-3-3 test produces a significant increase in the diagnosis certainty (positive likelihood ratio: 10.1) compared to the WHO's criteria, excluding the 14-3-3 test. For patients classified at sample reception as probable sCJD (n=166), possible sCJD (n=129) and non-sCJD (n=773), the positive predictive values for the test were 98.4%, 97.5% and 31%, and the negative predictive values were 22.2%, 73.4% and 100%, respectively. CONCLUSIONS: The predictive values of the assay vary according to the previous diagnostic certainty. Therefore, in order to interpret correctly the test, it is necessary to evaluate the degree of initial clinical suspicion of the patient at the moment of the cerebrospinal fluid (CSF) extraction. This study offers up-to-date information, referenced to the Spanish population, and in useful format, and it is intended to serve as a guideline for 14-3-3 test results interpretation to the clinicians in our community.

Utilidad del inmunoensayo de la proteína 14-3-3 en el diagnóstico de la enfermedad de Creutzfeldt-Jakob examinada desde un centro de referencia nacional / Usefulness of the 14-3-3 test for the diagnosis of sCJD evaluated by a Spanish reference center

Introducción. El inmunoensayo de la proteína 14-3-3 en líquido cefalorraquídeo (LCR) muestra un rendimiento óptimo para el diagnóstico de la enfermedad de Creutzfeldt- Jakob esporádica (ECJe) en poblaciones seleccionadas, pero su validez en la práctica rutinaria ha sido cuestionada. Método. Se estudiaron 1.068 pacientes con sospecha de ECJe procedentes de distintas instituciones españolas. Para explorar la influencia del contexto clínico sobre la validez del inmunoensayo los pacientes fueron clasificados en el momento de la recepción de la muestra de acuerdo con los criterios de certeza diagnóstica establecidos por la Organización Mundial de la Salud (OMS), excluyendo la prueba de la proteína 14-3-3. El rendimiento del immunoensayo se evaluó en cada subgrupo con criterios de ECJe probable, posible o no ECJe. Resultados. En el conjunto de pacientes con sospecha de ECJe la inclusión del inmunoensayo supone un aumento significativo en la certeza diagnóstica (razón de verosimilitud positiva: 10,1) sobre los criterios de la OMS sin incluir dicha prueba. En los subgrupos de pacientes clasificados a la recepción de la muestra como ECJe probable (n=166), ECJe posible (n=129) y no ECJe (n=773) los valores predictivos positivos de la prueba de la proteína 14-3-3 fueron 98,4, 97,5 y 31% y los valores predictivos negativos fueron 22,2, 73,4 y 100%, respectivamente. Conclusiones. Los valores predictivos de la prueba varían según el grado de certeza diagnóstica previa de cada paciente. Por ello, para interpretar correctamente el ensayo es necesario valorar el grado de sospecha clínica del paciente en el momento de la extracción del LCR. Este estudio pretende facilitar la interpretación de los resultados de la prueba de la proteína 14-3-3 a los especialistas clínicos, ofreciendo una información actualizada, referenciada a la población española y en formato de utilidad práctica (AU)

Introduction: The performance of the 14-3-3 protein test has been shown to be adequate for sporadic Creutzfeldt-Jakob disease (sCJD) diagnosis in selected populations, but its routine validity has been questioned. Methods: One thousand and sixty-eight patients with clinically suspected sCJD were analyzed in a Spanish reference center. In order to explore the influence of the clinical context on the performance of the immunoassay, the patients were classified at sample reception according to the World Health Organization (WHO) diagnostic criteria excluding the 14-3-3 test results. The yield of the immunoassay was evaluated in each subgroup with criteria of probable, possible sCJD or non-sCJD. Results: In the set of patients with suspicion of sCJD the inclusion of the 14-3-3 test produces a significant increase in the diagnosis certainty (positive likelihood ratio: 10.1) compared to the WHO's criteria, excluding the 14-3-3 test. For patients classified at sample reception as probable sCJD (n=166), possible sCJD (n=129) and non-sCJD (n=773), the positive predictive values for the test were 98.4%, 97.5% and 31%, and the negative predictive values were 22.2%, 73.4% and 100%, respectively. Conclusions: The predictive values of the assay vary according to the previous diagnostic certainty. Therefore, in order to interpret correctly the test, it is necessary to evaluate the degree of initial clinical suspicion of the patient at the moment of the cerebrospinal fluid (CSF) extraction. This study offers up-to-date information, referenced to the Spanish population, and in useful format, and it is intended to serve as a guideline for 14-3-3 test results interpretation to the clinicians in our community (AU)

Classification of surgical procedures for epidemiologic assessment of sporadic Creutzfeldt-Jakob disease transmission by surgery.

BACKGROUND: In this preparatory phase of a case-control study, we propose and evaluate a new tool for classifying surgical procedures (SPs) in categories useful for epidemiologic research on surgical transmission of sporadic Creutzfeldt-Jakob disease (sCJD). METHODS: All SPs reported to the Swedish National Hospital Discharge Registry in the period 1974-2002, and undergone by 212 Swedish patients with registered diagnosis of CJD at death, hospital discharge or notification, in the period 1987-2002, 1060 age-, sex- and residence-matched controls and 1340 randomly chosen population controls, were reclassified into one of six categories of hypothetical transmission risk level. For that purpose the following two attributes were used: non-disposable instruments involved; and highest assigned ad-hoc risk level for four tissues or anatomical structures contacting such instruments. RESULTS: A total of 1170 different SP codes were reclassified as follows: 3.1% in the high-risk, 59.1% in the lower-risk, 24.4% in the lowest-risk, and 2.1% in the no-risk groups, with 11.3% procedures negatively defined by rubric as "other than..." being assigned to two spurious diluted-high and diluted-lower risk categories. The high-risk group mainly comprised neurosurgical (53%) and ophthalmic (39%) procedures. Sensitivity of neurosurgery and of ophthalmic surgery excluding neurosurgery, for the high- and diluted-high risk vs. other categories was 46% and 84%, while specificity was 98% and 95%, respectively. Sensitivity analysis based on these indices revealed that non-significant odds ratio effects of 1.4 and 1.3 for neurosurgery and ophthalmic surgery corresponded to statistically significant values of 5.1 after reclassification. CONCLUSIONS: This classification might contribute to quantify effects masked by use of body-system SP-categories in case-control studies on sCJD transmission by surgery.

Transgenic mice expressing bovine PrP with a four extra repeat octapeptide insert mutation show a spontaneous, non-transmissible, neurodegenerative disease and an expedited course of BSE infection.

Transgenic (Tg) mice carrying four extra octapeptide repeats (OR) in the bovine PrP gene (10OR instead of 6) have been generated. In these mice, neuropathological changes were observed depending upon the level of transgene expression. These changes primarily involved a slowly advancing neurological disorder, characterized clinically by ataxia, and neuropathologically, by vacuolization in different brain areas, gliosis, and loss of cerebellar granule cells. Accumulation of insoluble bovine 10OR-PrP (bo10OR-PrP) was observed depending on the level of expression but no infectivity was found associated with this insoluble form. We also compared the behavior of bo6OR-PrP and bo10OR-PrP Tg mouse lines in response to BSE infection. BSE-inoculated bo10ORTg mice showed an altered course of BSE infection, reflected by reduced incubation times when compared to bo6ORTg mice expressing similar levels of the wild type 6OR-PrP. In BSE-inoculated mice, it was possible to detect PrP(res) in 100% of the animals. While insoluble bo10OR-PrP from non-inoculated bo10ORTg mice was non-infectious, brain homogenates from BSE-inoculated bo10ORTg mice were highly infectious in all the Tg mouse lines tested. This Tg mouse model constitutes a new way of understanding the pathobiology of bovine transmissible spongiform encephalopathy. Its potential applications include the assessment of new therapies against prion diseases.

New V272A presenilin 1 mutation with very early onset subcortical dementia and parkinsonism.

In this report, we present the clinical and pathological details of a kindred of four individuals with a novel missense mutation (V272A) of the presenilin 1 gene (PSEN1) that experienced a subcortical dementia. The age of onset of symptoms ranged 26-36-year old, with an age at death of 36-46 years. Initial symptom was a marked mood disorder, with prominent parkinsonism in one case. The neuropsychological study, as well as the neuroimaging and PET in the proband were concordant with a subcortical dementia. The cerebral pathology showed in this patient, aside from the classical lesions of Alzheimer disease, Lewy bodies in cortex and substantia nigra, and widespread subcortical neuritic lesions. This clinical pattern and pathology expands the clinical spectrum of familial Alzheimer's disease and compel to include mutations of PSEN1 gene in the genetic study of subcortical dementia.

Different behavior toward bovine spongiform encephalopathy infection of bovine prion protein transgenic mice with one extra repeat octapeptide insert mutation.

In humans, insert mutations within the repetitive octapeptide region of the prion protein gene (Prnp) are often associated with familial spongiform encephalopathies. In this study, transgenic mice expressing bovine PrP (boTg mice) bearing an additional octapeptide insertion to the wild type (seven octapeptide repeats instead of six) showed an altered course of bovine spongiform encephalopathy (BSE) infection, reflected as reduced incubation times when compared with boTg mice expressing similar levels of the wild-type six-octapeptide protein. In both boTg mouse lines (bo6ORTg and bo7ORTg), incubation times were affected drastically depending on transgene expression levels and the inoculum used. In accordance with the lack of an interspecies barrier to BSE infection, we detected the typical signs of CNS spongiform degeneration by histopathological analysis and the presence of the bovine prion PrP(res) by Western blot or immunohistochemical analyses. When 7OR-PrP(res) was propagated in bo7ORTg mice, a similar earlier onset of clinical signs was observed compared with bo6ORTg mice. Proteins PrP(C) and PrP(res) containing seven octapeptides (7OR-PrP(C) and 7OR-PrP(res)) showed similar protease sensitivity and insolubility in nondenaturing detergents to homologous 6OR-PrP(C) and 6OR-PrP(res). In addition, bo7ORTg mice showed a higher sensitivity than bo6ORTg mice for detecting prion infection in specimens previously diagnosed as negative by conventional biochemical techniques. In the absence of clinical signs of disease, 7OR-PrP(res) could be detected as early as 120 d after inoculation by immunohistochemical and Western blot analyses. These findings may help us improve the current mouse bioassays and understand the role of the octapeptide repeat region in susceptibility to disease.