Optimized tumour infiltrating lymphocyte assessment for triple negative breast cancer prognostics

The tumour microenvironment has been shown to be a valuable source of prognostic information for different cancer types. This holds in particular for triple negative breast cancer (TNBC), a breast cancer subtype for which currently no prognostic biomarkers are established. Although different methods to assess tumour infiltrating lymphocytes (TILs) have been published, it remains unclear which method (marker, region) yields the most optimal prognostic information. In addition, to date, no objective TILs assessment methods are available. For this proof of concept study, a subset of our previously described TNBC cohort (n = 94) was stained for CD3, CD8 and FOXP3 using multiplex immunohistochemistry and subsequently imaged by a multispectral imaging system. Advanced whole-slide image analysis algorithms, including convolutional neural networks (CNN) were used to register unmixed multispectral images and corresponding H&E sections, to segment the different tissue compartments (tumour, stroma) and to detect all individual positive lymphocytes. Densities of positive lymphocytes were analysed in different regions within the tumour and its neighbouring environment and correlated to relapse free survival (RFS) and overall survival (OS). We found that for all TILs markers the presence of a high density of positive cells correlated with an improved survival. None of the TILs markers was superior to the others. The results of TILs assessment in the various regions did not show marked differences between each other. The negative correlation between TILs and survival in our cohort are in line with previous studies. Our results provide directions for optimizing TILs assessment methodology.

Discrepancies in digital hematopathology diagnoses for consultation and expert panel analysis

Digital pathology with whole-slide imaging (WSI) has a large potential to make the process of expert consultation and expert panel diagnosis more rapid and more efficient. However, comparison with the current methods is necessary for validation of the technique. In this study, we determined if digital assessment of whole-slide images of hematopathology specimens with a focus on the assessment of lymphoma can be used for consultation and panel diagnostics. Ninety-three histological specimens with a suspicion for lymphoma were assessed both with conventional microscopy and digital microscopy with a wash out period between assessments. A consensus diagnosis was based on full concordance between the pathologists or, in case of discordances, was reached at a joint session at a multi-headed microscope. In 81% of the cases, there was a full concordance between digital and light microscopical assessment for all three pathologists. Discordances between conventional microscopy and digital pathology were present in 3% of assessments. In comparison with the consensus diagnosis, discordant diagnoses were made in 5 cases with digital microscopy and in 3 cases with light microscopy. The reported level of confidence and need for additional investigations were similar between assessment by conventional and by digital microscopy. In conclusion, the performance of assessment by digital pathology is in general comparable with that of conventional light microscopy and pathologists feel confident using digital pathology for this subspecialty.

HER2, chromosome 17 polysomy and DNA ploidy status in breast cancer; a translational study

Breast cancer treatment depends on human epidermal growth factor receptor-2 (HER2) status, which is often determined using dual probe fluorescence in situ hybridisation (FISH). Hereby, also loss and gain of the centromere of chromosome 17 (CEP17) can be observed (HER2 is located on chromosome 17). CEP17 gain can lead to difficulty in interpretation of HER2 status, since this might represent true polysomy. With this study we investigated whether isolated polysomy is present and how this effects HER2 status in six breast cancer cell lines and 97 breast cancer cases, using HER2 FISH and immunohistochemistry, DNA ploidy assessment and multiplex ligation dependent probe amplification. We observed no isolated polysomy of chromosome 17 in any cell line. However, FISH analysis did show CEP17 gain in five of six cell lines, which reflected gains of the whole chromosome in metaphase spreads and aneuploidy with gain of multiple chromosomes in all these cases. In patients' samples, gain of CEP17 indeed correlated with aneuploidy of the tumour (91.1%; p < 0.001). Our results indicate that CEP17 gain is not due to isolated polysomy, but rather due to widespread aneuploidy with gain of multiple chromosomes. As aneuploidy is associated with poor clinical outcome, irrespective of tumour grade, this could improve future therapeutic decision making.

Stain Specific Standardization of Whole-Slide Histopathological Images

Variations in the color and intensity of hematoxylin and eosin (H&E) stained histological slides can potentially hamper the effectiveness of quantitative image analysis. This paper presents a fully automated algorithm for standardization of whole-slide histopathological images to reduce the effect of these variations. The proposed algorithm, called whole-slide image color standardizer (WSICS), utilizes color and spatial information to classify the image pixels into different stain components. The chromatic and density distributions for each of the stain components in the hue-saturation-density color model are aligned to match the corresponding distributions from a template whole-slide image (WSI). The performance of the WSICS algorithm was evaluated on two datasets. The first originated from 125 H&E stained WSIs of lymph nodes, sampled from 3 patients, and stained in 5 different laboratories on different days of the week. The second comprised 30 H&E stained WSIs of rat liver sections. The result of qualitative and quantitative evaluations using the first dataset demonstrate that the WSICS algorithm outperforms competing methods in terms of achieving color constancy. The WSICS algorithm consistently yields the smallest standard deviation and coefficient of variation of the normalized median intensity measure. Using the second dataset, we evaluated the impact of our algorithm on the performance of an already published necrosis quantification system. The performance of this system was significantly improved by utilizing the WSICS algorithm. The results of the empirical evaluations collectively demonstrate the potential contribution of the proposed standardization algorithm to improved diagnostic accuracy and consistency in computer-aided diagnosis for histopathology data.

Dickkopf-related protein 3 is a potential Aβ-associated protein in Alzheimer's Disease

Amyloid-β (Aβ) is the most prominent protein in Alzheimer's disease (AD) senile plaques. In addition, Aβ interacts with a variety of Aβ-associated proteins (AAPs), some of which can form complexes with Aβ and influence its clearance, aggregation or toxicity. Identification of novel AAPs may shed new light on the pathophysiology of AD and the metabolic fate of Aβ. In this study, we aimed to identify new AAPs by searching for proteins that may form soluble complexes with Aβ in CSF, using a proteomics approach. We identified the secreted Wnt pathway protein Dickkopf-related protein 3 (Dkk-3) as a potential Aβ-associated protein. Using immunohistochemistry on human AD brain tissue, we observed that (i) Dkk-3 co-localizes with Aβ in the brain, both in diffuse and classic plaques. (ii) Dkk-3 is expressed in neurons and in blood vessel walls in the brain and (iii) is secreted by leptomeningeal smooth muscle cells in vitro. Finally, measurements using ELISA revealed that (iv) Dkk-3 protein is abundantly present in both cerebrospinal fluid and serum, but its levels are similar in non-demented controls and patients with AD, Lewy body dementia, and frontotemporal dementia. Our study demonstrates that Dkk-3 is a hitherto unidentified Aβ-associated protein which, given its relatively high cerebral concentrations and co-localization with Aβ, is potentially involved in AD pathology. In this study, we propose that Dickkopf-related protein-3 (Dkk-3) might be a novel Amyloid-β (Aβ) associated protein. We demonstrate that Dkk-3 is expressed in the brain, especially in vessel walls, and co-localizes with Aβ in senile plaques. Furthermore, Dkk-3 levels in cerebrospinal fluid strongly correlate with Aβ40 levels, but were not suitable to discriminate non-demented controls and patients with dementia.

High prevalence of atypical hyperplasia in the endometrium of patients with epithelial ovarian cancer

OBJECTIVES

The aim of the present study is to determine the prevalence of endometrial premalignancies in women diagnosed with epithelial ovarian cancer (EOC).

METHODS

Endometrial and ovarian specimens of 186 patients with EOC were retrospectively selected using the nationwide pathology network and registry, and sections were comprehensively reviewed: 136 (73%) serous, 19 (10%) endometrioid, 15 (8%) mucinous, seven (4%) clear cell, and nine (5%) undifferentiated. Immunohistochemical phenotypes were compared for patients with serous EOC with concurrent endometrial pathology.

RESULTS

In 31%, endometrial (pre)malignancy was found: carcinoma in 3%, endometrial intraepithelial carcinoma (EIC) in 4%, and atypical hyperplasia in 24%. Atypical hyperplasia was found in 47% of endometrioid EOCs but in 7% to 33% of other subtypes. Body mass index was higher concurrent to atypical hyperplasia (P=.001). Serous EOC and EIC immunophenotypes were comparable, whereas atypical hyperplasia was expressed differently.

CONCLUSIONS

Apart from synchronous endometrial carcinoma, endometrial premalignancies should be taken into account when determining optimal treatment for women diagnosed with EOC.

Lithium causes G2 arrest of renal principal cells

Vasopressin-regulated expression and insertion of aquaporin-2 channels in the luminal membrane of renal principal cells is essential for urine concentration. Lithium affects urine concentrating ability, and approximately 20% of patients treated with lithium develop nephrogenic diabetes insipidus (NDI), a disorder characterized by polyuria and polydipsia. Lithium-induced NDI is caused by aquaporin-2 downregulation and a reduced ratio of principal/intercalated cells, yet lithium induces principal cell proliferation. Here, we studied how lithium-induced principal cell proliferation can lead to a reduced ratio of principal/intercalated cells using two-dimensional and three-dimensional polarized cultures of mouse renal collecting duct cells and mice treated with clinically relevant lithium concentrations. DNA image cytometry and immunoblotting revealed that lithium initiated proliferation of mouse renal collecting duct cells but also increased the G2/S ratio, indicating G2/M phase arrest. In mice, treatment with lithium for 4, 7, 10, or 13 days led to features of NDI and an increase in the number of principal cells expressing PCNA in the papilla. Remarkably, 30%-40% of the PCNA-positive principal cells also expressed pHistone-H3, a late G2/M phase marker detected in approximately 20% of cells during undisturbed proliferation. Our data reveal that lithium treatment initiates proliferation of renal principal cells but that a significant percentage of these cells are arrested in the late G2 phase, which explains the reduced principal/intercalated cell ratio and may identify the molecular pathway underlying the development of lithium-induced renal fibrosis.

Chromosome instability predicts the progression of premalignant oral lesions

OBJECTIVES

One of the main problems in reducing the incidence of oral squamous cell carcinoma (OSCC) is the inability to appropriately deal with leukoplakia. Accurately identifying lesions which will progress to malignancy is currently not possible. The present study aims to establish the value of chromosome instability (CI) detection by DNA image cytometry and FISH analysis for prognosis and monitoring of oral leukoplakia.

MATERIALS AND METHODS

For this purpose, we included from our archives 102 oral leukoplakia cases, which had been diagnosed between 1991 and 2008. Patient follow-up data were collected and the histopathological diagnosis was revised. CI assessment was carried out on paraffin-embedded tissue sections using both DNA image cytometry (ICM) and dual target FISH for chromosomes 1 and 7.

RESULTS

16 of 102 Patients developed carcinoma in situ or OSCC. Both detection methods were found to yield prognostic information independent of the histopathological diagnosis. CI was a strong individual marker of progression, with hazard ratios (HRs) of 7.2 and 6.8 for ICM and FISH respectively. Moreover, this approach seems suitable for monitoring lesions over time (especially ICM). Combining histopathology and CI enables subdivision of patients into three risk groups, with different probabilities of malignant progression.

CONCLUSION

CI detection seems a reliable method for risk assessment of oral premalignancies and its application may contribute to a better risk-counselling and appropriate treatment regimen or watchfull-waiting approach of patients.

Simultaneous assessment of DNA ploidy and biomarker expression in paraffin-embedded tissue sections

AIMS

Simultaneous assessment of DNA ploidy and biomarker expression in paraffin-embedded tissue sections Aims: Aneuploidy is a potential biomarker for predicting progression of premalignancies. Ploidy assessment is mostly performed on nuclei isolated from tissue sections. Ploidy assessment in situ in tissue sections may be a large improvement, enabling selective sampling of nuclei, thus allowing the correlation between ploidy and histology. Existing ploidy analysis methods in sections suffer from limited sensitivity. The aim was to reliably assess ploidy in sections, combined with simultaneous assessment of other markers at the individual cell level.

METHODS AND RESULTS

Ploidy was measured in 22 paraffin-embedded oral premalignancies. The DNA stoichiometric Feulgen procedure was used on isolated nuclei, as well as fluoresence in situ hybridization analysis. In tissue sections, Feulgen was combined with immunohistochemistry for Ki67 proliferation marker, enabling distinction between cycling euploid and aneuploid cells. Aneuploidy was reliably detected in tissue sections (sensitivity 100%, specificity 92%). One section in which aneuploidy was detected was misclassified in isolated nuclei analysis. Sections were also successfully analysed using our model combined with DNA double strand break marker gamma-H2AX in fluorescence microscopy, underlining the power of biomarker evaluation on single cells in tissue sections.

CONCLUSIONS

The analysis model proposed in this study enables the combined analysis of histology, genotypic and phenotypic information.

Targeted therapy for Ewing's sarcoma: significance of heterogeneity

BACKGROUND

Survival in Ewing's sarcoma (ES) is limited. Experience with insulin-like growth factor targeting drugs, which require specific molecular tumour alterations, herald a major breakthrough. We screened for tumour heterogeneity within patients by DNA quantification.

MATERIALS AND METHODS

DNA image cytometry (IC) was performed on 41 samples from 21 patients, evaluating if ploidy state remained constant over time and between different lesions within patients and the prognostic value of ploidy was assessed.

RESULTS

DNA content varied over time and different ploidy states were found to coexist at a single timepoint. Non-diploid DNA content was associated with shorter overall survival (median, 19 vs. 84 months, p=0.047).

CONCLUSION

We encountered a change and heterogeneity of ploidy state. This implies that screening for targets on a single tumour sample is insufficient and may lead to under- or overtreatment. The fact that non-diploid DNA content was associated with an adverse outcome confirms that this technique discriminates biologically different tumour clones.

The prognostic value of blood and lymph vessel parameters in lichen sclerosus for vulvar squamous cell carcinoma development: an immunohistochemical and electron microscopy study

OBJECTIVE

The objective of the study was to quantify vessel type and density in lichen sclerosus (LS) to find a marker for its malignant potential.

STUDY DESIGN

Quantitative analysis was performed on paraffin-embedded tissue samples of 28 patients with LS (7 adjacent to vulvar squamous cell carcinoma, 21 solitary) and immunohistochemical staining for CD34 (vascular and lymphangiogenic lymph endothelial cells), D2-40 (lymphatic-specific marker), and alpha-SMA (pericyte marker). Electron microscopy was performed on fresh tissue.

RESULTS

No significant differences in vessel density or other vessel parameters could be demonstrated between the 2 groups. In hyalinized lesions, vessel diameter, and alpha-SMA positivity was reduced compared with nonhyalinized lesions. Electron microscopy revealed detachment of pericytes from vascular endothelial cells and increased thickening of basement membrane, whereas endothelial cell function did not appear strongly impaired.

CONCLUSION

Malignant potential of LS cannot be predicted by vessel characteristics. Hyalinization in LS is associated with pericyte detachment from the basal lamina of vascular endothelial cells.

High levels of p53 expression correlate with DNA aneuploidy in (pre)malignancies of the vulva

The molecular pathogenesis of human papilloma virus-unrelated vulvar squamous cell carcinoma is not well known. Whether malignant progression of lichen sclerosus and differentiated vulvar intraepithelial neoplasia to vulvar squamous cell carcinoma could be accompanied by altered DNA content has not been studied extensively. DNA content in isolated nuclei of microdissected normal vulvar epithelium (n = 2), lichen sclerosus (n = 9), differentiated vulvar intraepithelial neoplasia (n = 13), and squamous cell carcinoma (n = 17) from 22 patients was measured via DNA image cytometry. For additional analysis, 6 differentiated vulvar intraepithelial neoplasia lesions were selected, bringing the number of patients to 28. p53 expression was determined by immunohistochemistry on consecutive tissue sections. Thirty-eight percent (5/13) of differentiated vulvar intraepithelial neoplasia lesions and 65% (11/17) of squamous cell carcinomas were DNA aneuploid or tetraploid. In lesions that contained differentiated vulvar intraepithelial neoplasia and adjacent squamous cell carcinoma, the ploidy status of differentiated vulvar intraepithelial neoplasia did not exceed that of squamous cell carcinoma. We observed a strong correlation between high p53 expression and DNA aneuploidy. This relation was also present at the level of a single nucleus, measured by sequential image cytometry of p53 immunohistochemistry followed by DNA image cytometry on formalin-fixed tissue sections. Similarly, we found p53-positive nonproliferating cells with increased DNA content in the superficial compartment of 6 additional solitary differentiated vulvar intraepithelial neoplasia lesions that were not associated with squamous cell carcinoma, indicating ascending aneuploid cells from the basal compartment. DNA ploidy measurements suggest that differentiated vulvar intraepithelial neoplasia has a higher malignant potential than lichen sclerosus and thus is a more likely precursor of squamous cell carcinoma. Furthermore, high p53 expression correlates with increased DNA content and aneuploidy; but it requires further research to unveil a possible causal relation.

Aggregation and cytotoxic properties towards cultured cerebrovascular cells of Dutch-mutated Abeta40 (DAbeta(1-40)) are modulated by sulfate moieties of heparin

Glycosaminoglycans (GAGs), in particular as part of heparan sulfate proteoglycans, are associated with cerebral amyloid angiopathy (CAA). Similarly, GAGs are also associated with the severe CAA found in patients suffering from hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), where the amyloid beta (Abeta) peptide contains the Dutch mutation (DAbeta(1-40)). This suggests a role for GAGs in vascular Abeta aggregation. It was the aim of this study to investigate the effect of different GAGs (heparin, chondroitin sulfate, heparan sulfate), the macromolecule dextran sulfate and, using desulfated heparins, the role of GAG sulfate moieties on the in vitro aggregation of CAA-associated DAbeta(1-40) and on DAbeta(1-40)-induced toxicity of cultured cerebrovascular cells. We also aimed to study the in vivo distribution of various sulfated heparan sulfate GAG epitopes in CAA. Of all GAGs tested, heparin was the strongest inducer of aggregation of DAbeta(1-40) in the different aggregation assays, with both heparin and heparan sulfate reducing Abeta-induced cellular toxicity. Furthermore, (partial) removal of the sulfate moieties of heparin partially abolished the effects of heparin on aggregation and cellular toxicity, suggesting an essential role for the sulfate moieties in heparin. Finally, we demonstrated the in vivo association of sulfated heparan sulfate (HS) GAGs with CAA. We conclude that sulfate moieties within GAGs, like heparin and HS, have an important role in Abeta aggregation in CAA and in Abeta-mediated toxicity of cerebrovascular cells.

The prediction of mandibular invasion by squamous cell carcinomas with the expression of osteoclast-related cytokines in biopsy specimens

Destruction of bone by tumour is caused by osteoclasts rather than by tumour cells directly. Tumour cells of invasive oral squamous cell carcinomas (SCC) release osteoclast-related cytokines and cytokines activate osteoclasts. The purpose of this study was to investigate the possibility of predicting mandibular invasion by SCC by analysis of the expression of osteoclast-related cytokines in biopsy specimens of SCC, adjacent or fixed to the mandible. Thirty-five biopsy specimens from the pathology archives were examined from patients who had been treated for SCC, adjacent or fixed to the mandible. The patients were divided into those with and without medullary invasion. The expression of tumour necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-11 was studied by immunohistochemical analysis. No significant differences were found in expression of TNF-alpha, IL-6 and IL-11 between biopsy specimens with or without medullary invasion. Quantification of the density of tumour-infiltrating lymphocytes was not reproducible. In conclusion, the expression of TNF-alpha, IL-6 and IL-11 in biopsy specimens of SCC, adjacent or fixed to the mandible, is not an appropriate method for predicting the presence of medullary invasion of the mandible.

Lipoprotein receptor-related protein-1 mediates amyloid-beta-mediated cell death of cerebrovascular cells

Inefficient clearance of A beta, caused by impaired blood-brain barrier crossing into the circulation, seems to be a major cause of A beta accumulation in the brain of late-onset Alzheimer's disease patients and hereditary cerebral hemorrhage with amyloidosis Dutch type. We observed association of receptor for advanced glycation end products, CD36, and low-density lipoprotein receptor (LDLR) with cerebral amyloid angiopathy in both Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis Dutch type brains and increased low-density lipoprotein receptor-related protein-1 (LRP-1) expression by perivascular cells in cerebral amyloid angiopathy. We investigated if these A beta receptors are involved in A beta internalization and in A beta-mediated cell death of human cerebrovascular cells and astrocytes. Expression of both the LRP-1 and LDLR by human brain pericytes and leptomeningeal smooth muscle cells, but not by astrocytes, increased on incubation with A beta. Receptor-associated protein specifically inhibited A beta-mediated up-regulation of LRP-1, but not of LDLR, and receptor-associated protein also decreased A beta internalization and A beta-mediated cell death. We conclude that especially LRP-1 and, to a minor extent, LDLR are involved in A beta internalization by and A beta-mediated cell death of cerebral perivascular cells. Although perivascular cells may adapt their A beta internalization capacity to the levels of A beta present, saturated LRP-1/LDLR-mediated uptake of A beta results in degeneration of perivascular cells.

Small heat shock proteins inhibit amyloid-beta protein aggregation and cerebrovascular amyloid-beta protein toxicity

Small heat shock proteins Hsp20 and HspB2/B3 co-localize with Abeta deposition in senile plaques and cerebral amyloid angiopathy in Alzheimer's disease brains, respectively. It was the aim of our study to investigate if these and other sHsps bind to wild-type Abeta1-42 or the more toxic Abeta1-40 carrying the 'Dutch' mutation (22Glu-->Gln) (D-Abeta1-40), affect Abeta aggregation and thereby influence Abeta cytotoxicity. Binding affinity between sHsps and Abeta was investigated by surface plasmon resonance. Abeta aggregation was studied by using circular dichroism spectroscopy and electron microscopy. Furthermore, we used cultured cerebrovascular cells to investigate the effects of sHsps on Abeta-mediated cytotoxicity. Hsp20, Hsp27 and alphaB-crystallin, but not HspB2/B3, bound to Abeta (both D-Abeta1-40 and Abeta1-42) and reduced or completely inhibited aggregation of D-Abeta1-40 into mature fibrils but did not affect Abeta1-42 aggregation. Furthermore, these sHsps were effective inhibitors of the cerebrovascular toxicity of Abeta (both D-Abeta1-40 and Abeta1-42) in vitro. Binding affinity of the sHsps to D-Abeta1-40 correlated to the degree of inhibition of Abeta-mediated cytotoxicity and the potential to reduce Abeta beta-sheet and fibril formation. With Abeta1-42, a similar correlation between binding affinity and cytotoxicity was observed, but not with its aggregation state. In conclusion, sHsps may regulate Abeta aggregation and serve as antagonists of the biological action of Abeta, but the extent of their interaction depends on the type of sHsp and Abeta peptide.

Specific association of small heat shock proteins with the pathological hallmarks of Alzheimer's disease brains

The small heat shock protein family (sHsp) comprises molecular chaperones able to interact with incorrectly folded proteins. Alzheimer's disease (AD) is characterized by pathological lesions such as senile plaques (SPs), cerebral amyloid angiopathy (CAA) and neurofibrillary tangles (NFTs), predominantly consisting of the incorrectly folded proteins amyloid-beta (Abeta) and tau respectively. The aim of this study was to investigate the association of the chaperones Hsp20, HspB2, alphaB-crystallin and Hsp27 with the pathological lesions of AD brains. For this purpose, a panel of well-characterized antibodies directed against these sHsps was used in immunohistochemistry and immunoblotting. We observed extracellular expression of Hsp20, Hsp27 and HspB2 in classic SPs, and Hsp20 expression in diffuse SPs. In addition, extracellular expression of HspB2 was observed in CAA. Both Hsp27 and alphaB-crystallin were also observed in astrocytes associated with both SPs and CAA. Furthermore, none of the sHsps were observed in NFTs in AD brains. We conclude that specific sHsp species may be involved in the pathogenesis of either SPs or CAA in AD.

Apolipoprotein E genotype regulates amyloid-beta cytotoxicity

The epsilon4 allele of apolipoprotein E (ApoE) is a risk factor for Alzheimer's disease (AD), whereas the epsilon2 allele may be relatively protective. Both alleles are risk factors for cerebral amyloid angiopathy (CAA)-related hemorrhages. CAA is associated with degeneration of smooth muscle cells and pericytes. Previously, we described that synthetic amyloid-beta1-40 peptide (Abeta1-40) with the 22Glu--> Gln "Dutch" mutation caused pericyte death in vitro by a mechanism that involves Abeta fibril-like assembly at the cell surface. It is known that ApoE binds to Abeta and may modify its biological activities. In the present study, we evaluated the effect of ApoE on Abeta-mediated toxicity of cerebrovascular cells. We observed that cultured cells with an epsilon4/epsilon4 genotype were more vulnerable to Abeta than cultures with an epsilon3/epsilon3 or epsilon3/epsilon4 genotype. The one cell culture with the epsilon2/epsilon3 genotype was relatively resistant to Abeta compared with other cultures. Furthermore, we observed a dose-dependent protective effect of native ApoE against Abeta-mediated toxicity of cerebrovascular cells and, in addition, ApoE epsilon2/epsilon3 cells secreted more ApoE protein compared with cells with other ApoE genotypes, in particular, compared with epsilon4/epsilon4 cells. Thus, the disparity between ApoE genotype and Abeta-mediated toxicity might be related to differences in the cellular capacity to secrete ApoE. The present data suggest that one mechanism by which ApoE may alter the risk for AD is a genotype-dependent regulation of Abeta cytotoxicity, possibly via variations in its secretion levels, whereby extracellular ApoE may bind to Abeta and thereby modify Abeta-mediated cell death.

Small heat shock protein HspB8: its distribution in Alzheimer's disease brains and its inhibition of amyloid-beta protein aggregation and cerebrovascular amyloid-beta toxicity

Alzheimer's disease (AD) is characterized by pathological lesions, such as senile plaques (SPs) and cerebral amyloid angiopathy (CAA), both predominantly consisting of a proteolytic cleavage product of the amyloid-beta precursor protein (APP), the amyloid-beta peptide (Abeta). CAA is also the major pathological lesion in hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), caused by a mutation in the gene coding for the Abeta peptide. Several members of the small heat shock protein (sHsp) family, such as alphaB-crystallin, Hsp27, Hsp20 and HspB2, are associated with the pathological lesions of AD, and the direct interaction between sHsps and Abeta has been demonstrated in vitro. HspB8, also named Hsp22 of H11, is a recently discovered member of the sHsp family, which has chaperone activity and is observed in neuronal tissue. Furthermore, HspB8 affects protein aggregation, which has been shown by its ability to prevent formation of mutant huntingtin aggregates. The aim of this study was to investigate whether HspB8 is associated with the pathological lesions of AD and HCHWA-D and whether there are effects of HspB8 on Abeta aggregation and Abeta-mediated cytotoxicity. We observed the expression of HspB8 in classic SPs in AD brains. In addition, HspB8 was found in CAA in HCHWA-D brains, but not in AD brains. Direct interaction of HspB8 with Abeta(1-42), Abeta(1-40) and Abeta(1-40) with the Dutch mutation was demonstrated by surface plasmon resonance. Furthermore, co-incubation of HspB8 with D-Abeta(1-40) resulted in the complete inhibition of D-Abeta(1-40)-mediated death of cerebrovascular cells, likely mediated by a reduction in both the beta-sheet formation of D-Abeta(1-40) and its accumulation at the cell surface. In contrast, however, with Abeta(1-42), HspB8 neither affected beta-sheet formation nor Abeta-mediated cell death. We conclude that HspB8 might play an important role in regulating Abeta aggregation and, therefore, the development of classic SPs in AD and CAA in HCHWA-D.

Cerebral microvascular amyloid beta protein deposition induces vascular degeneration and neuroinflammation in transgenic mice expressing human vasculotropic mutant amyloid beta precursor protein

Cerebral vascular amyloid beta-protein (Abeta) deposition, also known as cerebral amyloid angiopathy, is a common pathological feature of Alzheimer's disease. Additionally, several familial forms of cerebral amyloid angiopathy exist including the Dutch (E22Q) and Iowa (D23N) mutations of Abeta. Increasing evidence has associated cerebral microvascular amyloid deposition with neuroinflammation and dementia in these disorders. We recently established a transgenic mouse model (Tg-SwDI) that expresses human vasculotropic Dutch/Iowa mutant amyloid beta-protein precursor in brain. Tg-SwDI mice were shown to develop early-onset deposition of Abeta exhibiting high association with cerebral microvessels. Here we present quantitative temporal analysis showing robust and progressive accumulation of cerebral microvascular fibrillar Abeta accompanied by decreased cerebral vascular densities, the presence of apoptotic cerebral vascular cells, and cerebral vascular cell loss in Tg-SwDI mice. Abundant neuroinflammatory reactive astrocytes and activated microglia strongly associated with the cerebral microvascular fibrillar Abeta deposits. In addition, Tg-SwDI mouse brain exhibited elevated levels of the inflammatory cytokines interleukin-1beta and -6. Together, these studies identify the Tg-SwDI mouse as a unique model to investigate selective accumulation of cerebral microvascular amyloid and the associated neuroinflammation.

Differential gene expression in human brain pericytes induced by amyloid-beta protein

Cerebral amyloid angiopathy is one of the characteristics of Alzheimer's disease (AD) and this accumulation of fibrillar amyloid-beta (Alphabeta) in the vascular wall is accompanied by marked vascular damage. In vitro, Abeta1-40 carrying the 'Dutch' mutation (DAbeta1-40) induces degeneration of cultured human brain pericytes (HBP). To identify possible intracellular mediators of Abeta-induced cell death, a comparative cDNA expression array was performed to detect differential gene expression of Abeta-treated vs. untreated HBP. Messenger RNA expression of cyclin D1, integrin beta4, defender against cell death-1, neuroleukin, thymosin beta10, and integrin alpha5 were increased in DAbeta1-40-treated HBP, whereas insulin-like growth factor binding protein-2 mRNA expression was decreased. Corresponding protein expression was investigated in AD and control brains to explore a potential role for these proteins in pathological lesions of the AD brain. Cyclin D1 expression was increased in cerebral amyloid angiopathy and cells in a perivascular position, suggesting that the cell cycle may be disturbed during Abeta-mediated degeneration of cerebrovascular cells. Moreover, cyclin D1 expression, but also that of integrin beta4, defender against cell death-1, neuroleukin and thymosin beta10 was found in a subset of senile plaques, suggesting a role for these proteins in the pathogenesis of senile plaques.

Insulin inhibits amyloid beta-induced cell death in cultured human brain pericytes

Amyloid-beta (Abeta) deposition in the cerebral arterial and capillary walls is one of the characteristics of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type. In vitro, Abeta1-40, carrying the "Dutch" mutation (DAbeta1-40), induced reproducible degeneration of cultured human brain pericytes (HBP), by forming fibrils at the cell surface. Thus, this culture system provides an useful model to study the vascular pathology seen in Alzheimer's disease. In this study, we used this model to investigate the effects of insulin on Abeta-induced degeneration of HBP, as it has been mentioned previously that insulin is able to protect neurons against Abeta-induced cell-death. The toxic effect of DAbeta1-40 on HBP was inhibited by insulin in a dose-dependent matter. Insulin interacted with Abeta and inhibited fibril formation of Abeta in a cell-free assay, as well as at the cell surface of HBP. Our data indicate that the formation of a fibril network is essential for Abeta-induced cell death in HBP. Additionally, insulin may be involved in the regulation of Abeta fibrillization in AD.

Expression of the cytokine leukemia inhibitory factor and pro-apoptotic insulin-like growth factor binding protein-3 in Alzheimer's disease

Amyloid-beta (Abeta) deposition in cerebral blood vessel walls is one of the key features of Alzheimer's disease (AD). Abeta(1-40) carrying the "Dutch" mutation (DAbeta(1-40)) induces rapid degeneration of cultured human brain pericytes (HBP). To study the mechanisms of this Abeta-induced toxicity, a comparative cDNA expression array was performed to detect differential gene expression of Abeta-treated versus untreated HBP. Messenger RNA expression of leukemia inhibitory factor (LIF) and insulin-like growth factor binding protein 3 (IGFBP-3) was increased in DAbeta(1-40)-treated HBP, whereas early growth response factor-1 (Egr-1) expression was decreased. Corresponding protein expression was investigated in AD and control brains. In all AD cases examined, LIF expression was observed in senile plaques and cerebral amyloid angiopathy, whereas IGFBP-3 expression in these lesions was only observed in a subset of cases. LIF and IGFBP-3 were also expressed in neurofibrillary tangles, as well as in neurons in AD and control brains. Egr-1 was predominantly expressed in astrocytes. Given its known involvement in both neuronal and immune responses to injury, the cytokine LIF may be a mediator of the inflammatory reaction seen in AD. IGFBP-3 is known to inhibit cell proliferation and induce apoptosis and may therefore contribute to neuronal degeneration in AD.

Inhibition of amyloid-beta-induced cell death in human brain pericytes in vitro

Amyloid-beta protein (A beta) deposition in the cerebral vascular walls is one of the key features of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). A beta(1-40) carrying the 'Dutch' mutation (HCHWA-D A beta(1-40)) induces pronounced degeneration of cultured human brain pericytes. In this study, we aimed to identify inhibitors of A beta-induced toxicity in human brain pericytes. The toxic effect of HCHWA-D A beta(1-40) on human brain pericytes was inhibited by co-incubation with catalase, but not with superoxide dismutase, glutathione or vitamin E analogue Trolox. Catalase interacts with A beta, both in cell cultures and in cell-free assays, and has a prominent effect on the amount and conformational state of A beta binding to the cell surface of human brain pericytes. This activity of catalase is likely based on its ability to bind and slowly degrade A beta and not by its usual capacity to convert hydrogen peroxide. Our data confirm that assembly of A beta at the cell surface of human brain pericytes is a crucial step in A beta-induced cellular degeneration of human brain pericytes. Inhibition of fibril formation at the cell surface could be an important factor in therapy aimed at reducing cerebral amyloid angiopathy.

Accumulation of heparan sulfate proteoglycans in cerebellar senile plaques

Alzheimer's disease (AD) brains are characterized by the presence of senile plaques (SPs), which primarily consist of amyloid beta protein (Abeta). Besides Abeta, several other proteins with the ability to modulate amyloid fibril formation accumulate in SPs, e.g. heparan sulfate proteoglycans (HSPGs). Cerebellar SPs are predominantly of the diffuse type, whereas fibrillar SPs are rarely observed. Furthermore, because of the spatial separation of non-fibrillar and fibrillar SPs in the cerebellum, this brain region provides a model for the study of the association of Abeta-associated factors with various stages of SP formation. In the present study, we performed an immunohistochemical analysis to investigate the expression of the HSPG species agrin, perlecan, glypican-1 and the syndecans 1-3 as well as glycosaminoglycan side-chains in cerebellar SPs. We demonstrated that agrin and glypican-1 were expressed in both non-fibrillar and fibrillar cerebellar SPs, whereas the syndecans were only associated with fibrillar cerebellar SPs. Perlecan expression was absent in all cerebellar SPs. Since fibrillar and non-fibrillar SPs may develop independently in the cerebellum, it is likely that agrin, glypican-1 as well as heparan sulfate glycosaminoglycans may contribute to the formation of both cerebellar plaque types, whereas syndecan only seems to play a role in the generation of cerebellar fibrillar plaques.

Accumulation of the amyloid-beta precursor protein in multivesicular body-like organelles

It has been suggested that the successive proteolytic events leading to the production of the amyloid-beta protein from its precursor may take place at different intracellular locations. Using cultured human leptomeningeal smooth muscle cells and brain pericytes, we modulated the intracellular localization of the amyloid-beta precursor protein (APP) to study possible effects on its processing. By using immunofluorescence and immunoelectron microscopy we demonstrated that, under normal conditions, the APP is found in small intracellular vesicles, some of which were characterized as lysosomes. Both the cytokine interferon-gamma and the lysosomotropic drug chloroquine, but not the cytokines interleukin (IL)-1, IL-6, or tumor necrosis factor-alpha (TNF-alpha), induced an accumulation of APP in newly formed multivesicular body-like organelles. The secretion of the amyloid-beta precursor protein was slightly reduced by interferon-gamma or chloroquine. Double-labeling and tracer molecule uptake experiments showed that the multivesicular body-like organelles were part of the endocytic pathway. Our findings suggest that the multivesicular body-like organelles function as an intermediate organelle in the intracellular trafficking of the APP. Accumulation of the APP in this organelle is reflected by its reduced secretion from the cell.

Presence of a fluid-conducting meshwork in xenografted cutaneous and primary human uveal melanoma

PURPOSE

Recently, it was reported that tumor cells themselves generate channels and networks in three-dimensional culture and can be found lining channels (some containing red blood cells [RBCs]) in vivo, and they express endothelial or vascular genes in aggressive uveal melanoma. The implications of these data for current insights in the involvement of angiogenesis in tumor growth, metastasis and therapeutic intervention are considerable. Therefore, this possibility was investigated in the current study.

METHODS

Thirty human uveal melanomas and 20 xenografts of human cutaneous melanoma were analyzed by Azan histochemistry and immunostaining of endothelial markers. Additionally, in xenografted tumors a tracer study was performed with confocal microscopy and immunoelectron microscopy.

RESULTS

Lumina or spaces without endothelial lining containing RBCs were not detected in any lesion. Functional evaluation of the vasculature in xenografts demonstrated rapid tracer appearance both inside and outside blood vessels. Outside blood vessels it spread along matrix networks of arcs and back-to-back loops. Confocal microscopy showed that this extracellular matrix was deposited as stromal sheets around nests of tumor cells. Laminin immunostaining revealed that between sheets surrounding adjacent nests, spaces were present. These spaces were filled, however, with collagen and different types of cells, including cells stained for macrophage markers.

CONCLUSIONS

Although no evident endothelium-free and RBC-containing channels were present in the tissues examined, there are fluid-conducting spaces in the form of stromal sheets between nests of tumor cells. In this stromal network, blood vessels are embedded. The authors postulate that this extracellular matrix tissue represents a fluid-conducting meshwork.

The angiopoietin-like factor cornea-derived transcript 6 is a putative morphogen for human cornea

The human cornea-specific protein cornea-derived transcript 6 (CDT6) is a member of the angiopoietin gene family. We report the structural and functional characterization of CDT6. We demonstrate that CDT6 is a secreted protein that folds into disulfide-linked homotetramers by coiled-coil interactions. The finding that CDT6 is expressed at high levels in the avascular corneal stromal layer suggested that the protein, similar to certain angiopoietins, acts as a negative regulator of angiogenesis. To test this hypothesis and to assay the effect of the protein on a growing tissue with high vascular density, CDT6 was expressed in a mouse xenograft model. Expression of CDT6 led to a reduction in tumor growth and aberrant blood vessel formation by inducing massive fibrosis. Interestingly, expression of CDT6 also resulted in the deposition of extracellular matrix components typical for the mature corneal stromal layer. These observations strongly suggest a role as morphogen for CDT6 in inducing a corneal phenotype in vivo.

Heparan sulfate proteoglycan expression in cerebrovascular amyloid beta deposits in Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis (Dutch) brains

Cerebrovascular deposition of amyloid beta protein (A beta) is a characteristic lesion of Alzheimer's disease (AD) and hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D). Besides A beta, several other proteins and proteoglycans accumulate in cerebral amyloid angiopathy (CAA). We have now analyzed the expression of the heparan sulfate proteoglycan (HSPG) subtypes agrin, perlecan, glypican-1, syndecans 1-3 and HS glycosaminoglycan (GAG) side chains in CAA in brains of patients with AD and HCHWA-D. Hereto, specific well-characterized antibodies directed against the core protein of these HSPGs and against the GAG side chains were used for immunostaining. Glypican-1 was abundantly expressed in CAA both in AD and HCHWA-D brains, whereas perlecan and syndecans-1 and -3 were absent in both. Colocalization of agrin with vascular A beta was clearly observed in CAA in HCHWA-D brains, but only in a minority of the AD cases. Conversely, syndecan-2 was frequently associated with vascular A beta in AD, but did not colocalize with vascular A beta deposits in HCHWA-D. The three different syndecans, agrin, glypican-1 and HS GAG, but not perlecan, were associated with the majority of senile plaques (SPs) in all brains. Our results suggest a role for agrin in the formation of SPs and of CAA in HCHWA-D, but not in the pathogenesis of CAA in AD. Both syndecan-2 and glypican, but not perlecan, may be involved in the formation of CAA. We conclude that specific HSPG species may be involved in the pathogenesis of CAA in both AD and HCHWA-D, and that the pathogenesis of CAA and SPs may differ with regard to the involvement of HSPG species.

Amyloid-beta-induced degeneration of human brain pericytes is dependent on the apolipoprotein E genotype

Amyloid-beta (A beta) deposition in cerebral vessels (cerebral amyloid angiopathy, CAA) is accompanied by degeneration of vascular cells, including pericytes and smooth muscle cells. Previous studies indicated that specific A beta protein isoforms are toxic for cultured human brain pericytes and smooth muscle cells. In particular, A beta 1-40 carrying the E22Q mutation, as in hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), is toxic. We investigated the effects of the A beta-binding protein apolipoprotein E (ApoE) on the toxicity of A beta for cultured human brain pericytes. We compared the toxicity of HCHWA-D A beta 1-40 for pericyte cultures with different ApoE genotypes, studied the accumulation of A beta and ApoE in these different cell cultures, and investigated the effects of exogenous ApoE. Pericyte cultures with an ApoE epsilon 2/epsilon 3 genotype were more resistant to HCHWA-D A beta 1-40 treatment than cultures with a epsilon 3/epsilon 3 or epsilon 3/epsilon 4 genotype. Cell death was highest in cultures homozygous for ApoE epsilon 4. The extent to which both A beta ApoE accumulated at the cell surface was parallel to the degree of toxicity. The addition of purified ApoE resulted in a decrease in cell death. These data suggest that ApoE4 may direct A beta more efficiently than other ApoE isoforms into a pathological interaction with the HBP cell surface. The results of this study are in line with the observations that inheritance of the ApoE epsilon 4 allele increases the risk of developing Alzheimer's disease, and that the ApoE epsilon 2 allele has a relatively protective effect.

Agrin is a major heparan sulfate proteoglycan accumulating in Alzheimer's disease brain

Heparan sulfate proteoglycans (HSPGs) have been suggested to play an important role in the formation and persistence of senile plaques and neurofibrillary tangles in dementia of the Alzheimer's type (DAT). We performed a comparative immunohistochemical analysis of the expression of the HSPGs agrin, perlecan, glypican-1, and syndecans 1-3 in the lesions of DAT brain neocortex and hippocampus. Using a panel of specific antibodies directed against the protein backbone of the various HSPG species and against the glycosaminoglycan (GAG) side-chains, we demonstrated the following. The basement membrane-associated HSPG, agrin, is widely expressed in senile plaques, neurofibrillary tangles and cerebral blood vessels, whereas the expression of the other basement membrane-associated HSPG, perlecan, is lacking in senile plaques and neurofibrillary tangles and is restricted to the cerebral vasculature. Glypican and three different syndecans, all cell membrane-associated HSPG species, are also expressed in senile plaques and neurofibrillary tangles, albeit at a lower frequency than agrin. Heparan sulfate GAG side chains are also associated with both senile plaques and neurofibrillary tangles. Our results suggest that glycosaminoglycan side chains of the HSPGs agrin, syndecan, and glypican, but not perlecan, may play an important role in the formation of both senile plaques and neurofibrillary tangles. In addition, we speculate that agrin, because it contains nine protease-inhibiting domains, may protect the protein aggregates in senile plaques and neurofibrillary tangles against extracellular proteolytic degradation, leading to the persistence of these deposits.

Human brain pericytes as a model system to study the pathogenesis of cerebrovascular amyloidosis in Alzheimer's disease

Cerebrovascular amyloidosis belongs to the pathological hallmarks of Alzheimer's disease brains. Although definite proof is still lacking, it is very well possible that the amyloid and its associated proteins are produced locally in the brain. In this paper we describe the development of a model system of cultured human brain pericytes to study the mechanisms of microvascular amyloid formation in vitro. These cultured cells may serve to study several aspects of cerebrovascular amyloidosis, which include the production of the amyloid precursor protein and of amyloid beta-protein-associated proteins as well as cytotoxic effects of amyloid beta-protein on perivascular cells. We demonstrated that pericytes produce and metabolize the amyloid precursor protein, and that they produce amyloid beta-protein-associated proteins, such as heparan sulfate proteoglycans, apolipoprotein E, and complement factor C1q. They are also prone to cellular degeneration after treatment with amyloid beta-protein, which is accompanied by increased expression of a number of amyloid beta-protein-associated proteins. This may be an important mechanism to explain the cell death observed in vivo. Our data indicate that this cell culture model of human brain pericytes provides a useful and pathophysiologically relevant tool to study cerebrovascular amyloidosis.

Distribution of A beta-associated proteins in cerebrovascular amyloid of Alzheimer's disease

Senile plaques and cerebrovascular amyloidosis (CA) are two of the major neuropathological lesions in brains of patients with dementia of the Alzheimer type. We studied the expression of a number of amyloid beta (A beta)-associated proteins in CA, which have previously been identified in senile plaques and which were suggested to play an important role in the pathogenesis of these lesions. Our findings show that involvement of inflammatory components in CA is restricted to activation of the complement system, resulting in deposition of the complement factors C1q, C3c, C4d and the membrane attack complex C5b-9 as well as of the complement inhibitor clusterin. Furthermore, we observed expression of apolipoprotein E, amyloid P component and heparan sulfate proteoglycans in CA, whereas expression of lactoferrin was almost absent. Other inflammatory proteins, known to be present in senile plaques, such as alpha1-antichymotrypsin, alpha2-macroglobulin and intercellular adhesion molecule-1, were absent or detectable only in small amounts. These data suggest that an incomplete inflammatory response occurs in CA as compared to senile plaques. This was confirmed by the finding that the number of cells of the monocyte/macrophage lineage around CA was not increased compared to unaffected vessels. Based on their expression patterns, complement factors, apolipoprotein E and heparan sulfate proteoglycans may be produced early in the process of CA formation and may play an important role in the formation of A beta fibrils in CA. The absence of a number of A beta-associated proteins in CA in comparison to senile plaques is in support of a different pathogenesis for these two lesions.

[Inflammatory mechanisms in the pathogenesis of Alzheimer's disease]

Senile plaques belong to the pathological hallmarks of the brains of patients with Alzheimer's disease. There is an increasing amount of evidence that the formation of senile plaques is accompanied by an acute phase reaction, involving the production of several inflammation-associated proteins and the activation of microglial cells. The products of these inflammatory reactions may contribute to the fibrillogenesis of the amyloid beta protein, the major constituent of senile plaques. Both fibrils of the amyloid beta protein and products of activated microglial cells may be neurotoxic, leading to neuronal degeneration and to clinical symptoms of dementia. Recent epidemiological findings have drawn attention to the possibility of therapy with anti-inflammatory agents. Although the results of these studies suggest a beneficial effect of such therapy, further study is warranted to gain more insight into the fundamental aspects of such treatment as well as to develop specific drugs that have little side-effects.

Differential expression of intercellular adhesion molecule-1 (ICAM-1) in the A beta-containing lesions in brains of patients with dementia of the Alzheimer type

Inflammatory processes have been implicated in the formation of senile plaques in the cerebral cortex of patients with dementia of the Alzheimer type (DAT), since several inflammation-induced proteins are present within these plaques. The relation between inflammatory components and other amyloid beta protein (A beta)-containing lesions of the DAT brain [cerebrovascular amyloidosis (CA) and cerebellar senile plaques] is unclear. We studied the distribution of the inflammation-inducible protein intercellular adhesion molecule-1 (ICAM-1) in CA and in senile plaques of the cerebellum, using an immunohistochemical approach. We observed striking differences in ICAM-1 reactivity between the different types of A beta-containing lesions. ICAM-1 was only expressed in classic senile plaques in the granular and Purkinje cell layer of the cerebellum, and not in diffuse senile plaques of the molecular layer. Also, ICAM-1 was not associated with CA; only when the vascular amyloid extended into the neuropil (dyshoric angiopathy) was perivascular ICAM-1 reactivity observed. This is in contrast to the putative primary involvement of inflammation in the formation of cerebrocortical classic and diffuse senile plaques. Our findings indicate that ICAM-1 expression, which may be an indicator of an inflammatory reaction, is induced in the neuropil depending on the specific site of A beta production.

A lysosomal marker for activated microglial cells involved in Alzheimer classic senile plaques

One of the major histopathological lesions in brains of patients with dementia of the Alzheimer type (DAT) is the senile plaque. Although previous studies have shown that senile plaques are often accompanied by microglial cells, the role of these cells in DAT pathology is still unclear. In an immunohistochemical and immunoelectron microscopical analysis of DAT and control brain tissues we addressed this issue using two monoclonal antibodies (mAbs KP1 and 25F9) directed against lysosomal antigens in monocytes and macrophages. Whereas KP1 stained lysosomes in both resting and activated microglial cells, 25F9-staining was predominantly found in lysosomes of activated microglial cells in classic senile plaques. The number and size of 25F9-positive lysosomes in activated microglial cells was increased compared to 25F9-staining in unaffected areas in DAT and control sections. We conclude that mAb 25F9 is a unique and useful lysosomal marker, with a higher specificity than other known markers, for activated microglial cells associated with classic, but not with diffuse, senile plaques.

Induction of alpha-smooth muscle actin expression in cultured human brain pericytes by transforming growth factor-beta 1

Pericytes are cells localized at the abluminal side of the microvascular endothelium and completely enveloped by a basement membrane. Pericytes have close contact with endothelial cells and are probably involved in the regulation of endothelial cell functions. Previous studies suggested a role for pericytes in microvascular proliferation in tumors. To study this cell type, we isolated human brain pericytes from microvessel segments derived from autopsy brain tissue. These cells were characterized in vitro using a panel of monoclonal antibodies. Human brain pericytes were reactive with monoclonal antibodies directed against the high molecular weight-melanoma associated antigen and intercellular adhesion molecule-1, but only a minority of the cells expressed alpha-smooth muscle actin (alpha-SMA, 0 to 10%) or vascular cell adhesion molecule-1 (10 to 50%). In histologically normal human brain microvessels in situ, pericytes consistently lacked staining for these four markers. Tissue with microvascular proliferation, however, showed a marked pericyte staining for both alpha-SMA and high molecular weight-melanoma associated antigen. The expression of alpha-SMA in vitro could be slightly up-regulated by incubation with serum-containing medium. An increase in alpha-SMA expression up to 40% of the total cell population was seen when pericytes were treated with transforming growth factor-beta 1, whereas basic fibroblast growth factor slightly inhibited alpha-SMA expression. Incubation with other factors (platelet-derived growth factor-AA, heparin, interferon-gamma, tumor necrosis factor-alpha) had no effect on the alpha-SMA expression at all. Transforming growth factor-beta 1 thus induces smooth muscle-like differentiation in pericytes in vitro and might play a role in the activation of pericytes during angiogenesis in vivo.

Accumulation of intercellular adhesion molecule-1 in senile plaques in brain tissue of patients with Alzheimer's disease

The still unsolved pathogenesis of Alzheimer's disease (AD) has been the subject of extensive speculation. Some years ago, a local acute phase reaction involving production of interleukin-1 (IL-1) and IL-6 was proposed as the triggering event in AD. Since it has been reported that these cytokines induce expression of intercellular adhesion molecule-1 (ICAM-1), we analyzed AD brain tissue cryosections for the presence of ICAM-1 by immunostaining and for ICAM-2 expression as a control. In senile plaques a marked diffuse or granular staining for the ICAM-1 domains 1, 4, and 5 was observed, whereas ICAM-2 expression was observed in microglial cells. Immunoprecipitation analysis demonstrated the presence of a 85 kd ICAM-1 molecule in AD frontal cortex. Our findings indicate that ICAM-1 accumulates in senile plaques as a complete 5-domain molecule at a relatively early stage of senile plaque formation. Our results are in support of a cytokine-mediated pathogenesis of senile plaque formation.

Exogenous aluminum accumulates in the lysosomes of cultured rat cortical neurons

In order to study the intracellular localization of aluminum, 0.01% AlCl3 was added to rat cerebral organotypic cultures following 14 days incubation in a standard medium. The cultures were maintained in the aluminum (Al)-containing medium for 1 or 3 days. Subsequently, electron probe X-ray micro-analysis (EPXMA), was used to localize aluminum in the neurons. The Al was found in the cells as early as after 1 day of AlCl3 exposure. The Al was detected exclusively in the neuronal lysosomes, in 66% (1 day exposure) and 97% (3 days) of the measured lysosomes. This localization was confirmed by laser microprobe mass analysis (LAMMA) measurements. Our results demonstrate an Al localization in the neurons, exposed to exogenous Al, different from that in the brains of patients with Alzheimer's disease.