Anti-Inflammatory Mesenchymal Stromal Cell-Derived Extracellular Vesicles Improve Pathology in Niemann-Pick Type C Disease

Niemann-Pick type C (NPC) disease is a rare neurovisceral lipid storage disease with progressive neurodegeneration, leading to premature death. The disease is caused by loss-of-function mutations either in the NPC1 or NPC2 gene which results in lipid accumulation in the late endosomes and lysosomes. The involved disease mechanisms are still incompletely understood, making the design of a rational treatment very difficult. Since the disease is characterized by peripheral inflammation and neuroinflammation and it is shown that extracellular vesicles (EVs) obtained from mesenchymal stromal cells (MSCs) provide immunomodulatory capacities, we tested the potential of MSC-EV preparations to alter NPC1 disease pathology. Here, we show that the administration of an MSC-EV preparation with in vitro and in vivo confirmed immune modulatory capabilities is able to reduce the inflammatory state of peripheral organs and different brain regions of NPC1-diseased mice almost to normal levels. Moreover, a reduction of foamy cells in different peripheral organs was observed upon MSC-EV treatment of NPC1-/- mice. Lastly, the treatment was able to decrease microgliosis and astrogliosis, typical features of NPC1 patients that lead to neurodegeneration. Altogether, our results reveal the therapeutic potential of MSC-EVs as treatment for the genetic neurovisceral lipid storage disease NPC, thereby counteracting both central and peripheral features.

Involvement of the Choroid Plexus in the Pathogenesis of Niemann-Pick Disease Type C

Niemann-Pick type C (NPC) disease, sometimes called childhood Alzheimer’s, is a rare neurovisceral lipid storage disease with progressive neurodegeneration leading to premature death. The disease is caused by loss-of-function mutations in the Npc1 or Npc2 gene which both result into lipid accumulation in the late endosomes and lysosomes. Since the disease presents with a broad heterogenous clinical spectrum, the involved disease mechanisms are still incompletely understood and this hampers finding an effective treatment. As NPC patients, who carry NPC1 mutations, have shown to share several pathological features with Alzheimer’s disease (AD) and we and others have previously shown that AD is associated with a dysfunctionality of the blood-cerebrospinal fluid (CSF) barrier located at choroid plexus, we investigated the functionality of this latter barrier in NPC1 pathology. Using NPC1^–/– mice, we show that despite an increase in inflammatory gene expression in choroid plexus epithelial (CPE) cells, the blood-CSF barrier integrity is not dramatically affected. Interestingly, we did observe a massive increase in autophagosomes in CPE cells and enlarged extracellular vesicles (EVs) in CSF upon NPC1 pathology. Additionally, we revealed that these EVs exert toxic effects on brain tissue, in vitro as well as in vivo. Moreover, we observed that EVs derived from the supernatant of NPC1^–/– choroid plexus explants are able to induce typical brain pathology characteristics of NPC1^–/–, more specifically microgliosis and astrogliosis. Taken together, our data reveal for the first time that the choroid plexus and CSF EVs might play a role in the brain-related pathogenesis of NPC1.

Low-grade peripheral inflammation affects brain pathology in the AppNL-G-Fmouse model of Alzheimer's disease

Alzheimer’s disease (AD) is a chronic neurodegenerative disease characterized by the accumulation of amyloid β (Aβ) and neurofibrillary tangles. The last decade, it became increasingly clear that neuroinflammation plays a key role in both the initiation and progression of AD. Moreover, also the presence of peripheral inflammation has been extensively documented. However, it is still ambiguous whether this observed inflammation is cause or consequence of AD pathogenesis. Recently, this has been studied using amyloid precursor protein (APP) overexpression mouse models of AD. However, the findings might be confounded by APP-overexpression artifacts. Here, we investigated the effect of low-grade peripheral inflammation in the APP knock-in (App^NL-G-F) mouse model. This revealed that low-grade peripheral inflammation affects (1) microglia characteristics, (2) blood-cerebrospinal fluid barrier integrity, (3) peripheral immune cell infiltration and (4) Aβ deposition in the brain. Next, we identified mechanisms that might cause this effect on AD pathology, more precisely Aβ efflux, persistent microglial activation and insufficient Aβ clearance, neuronal dysfunction and promotion of Aβ aggregation. Our results further strengthen the believe that even low-grade peripheral inflammation has detrimental effects on AD progression and may further reinforce the idea to modulate peripheral inflammation as a therapeutic strategy for AD.

Importance of extracellular vesicle secretion at the blood-cerebrospinal fluid interface in the pathogenesis of Alzheimer's disease

Increasing evidence indicates that extracellular vesicles (EVs) play an important role in the pathogenesis of Alzheimer’s disease (AD). We previously reported that the blood–cerebrospinal fluid (CSF) interface, formed by the choroid plexus epithelial (CPE) cells, releases an increased amount of EVs into the CSF in response to peripheral inflammation. Here, we studied the importance of CP-mediated EV release in AD pathogenesis. We observed increased EV levels in the CSF of young transgenic APP/PS1 mice which correlated with high amyloid beta (Aβ) CSF levels at this age. The intracerebroventricular (icv) injection of Aβ oligomers (AβO) in wild-type mice revealed a significant increase of EVs in the CSF, signifying that the presence of CSF-AβO is sufficient to induce increased EV secretion. Using in vivo, in vitro and ex vivo approaches, we identified the CP as a major source of the CSF-EVs. Interestingly, AβO-induced, CP-derived EVs induced pro-inflammatory effects in mixed cortical cultures. Proteome analysis of these EVs revealed the presence of several pro-inflammatory proteins, including the complement protein C3. Strikingly, inhibition of EV production using GW4869 resulted in protection against acute AβO-induced cognitive decline. Further research into the underlying mechanisms of this EV secretion might open up novel therapeutic strategies to impact the pathogenesis and progression of AD.

Extracellular Vesicles in Alzheimer's and Parkinson's Disease: Small Entities with Large Consequences

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are incurable, devastating neurodegenerative disorders characterized by the formation and spreading of protein aggregates throughout the brain. Although the exact spreading mechanism is not completely understood, extracellular vesicles (EVs) have been proposed as potential contributors. Indeed, EVs have emerged as potential carriers of disease-associated proteins and are therefore thought to play an important role in disease progression, although some beneficial functions have also been attributed to them. EVs can be isolated from a variety of sources, including biofluids, and the analysis of their content can provide a snapshot of ongoing pathological changes in the brain. This underlines their potential as biomarker candidates which is of specific relevance in AD and PD where symptoms only arise after considerable and irreversible neuronal damage has already occurred. In this review, we discuss the known beneficial and detrimental functions of EVs in AD and PD and we highlight their promising potential to be used as biomarkers in both diseases.

Counteracting the effects of TNF receptor-1 has therapeutic potential in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia, and neuroinflammation is an important hallmark of the pathogenesis. Tumor necrosis factor (TNF) might be detrimental in AD, though the results coming from clinical trials on anti‐TNF inhibitors are inconclusive. TNFR1, one of the TNF signaling receptors, contributes to the pathogenesis of AD by mediating neuronal cell death. The blood–cerebrospinal fluid (CSF) barrier consists of a monolayer of choroid plexus epithelial (CPE) cells, and AD is associated with changes in CPE cell morphology. Here, we report that TNF is the main inflammatory upstream mediator in choroid plexus tissue in AD patients. This was confirmed in two murine AD models: transgenic APP/PS1 mice and intracerebroventricular (icv) AβO injection. TNFR1 contributes to the morphological damage of CPE cells in AD, and TNFR1 abrogation reduces brain inflammation and prevents blood–CSF barrier impairment. In APP/PS1 transgenic mice, TNFR1 deficiency ameliorated amyloidosis. Ultimately, genetic and pharmacological blockage of TNFR1 rescued from the induced cognitive impairments. Our data indicate that TNFR1 is a promising therapeutic target for AD treatment.

Lymphoblast-derived integration-free iPSC lines from a female and male Alzheimer's disease patient expressing different copy numbers of a coding CNV in the Alzheimer risk gene CR1

Human lymphoblast cells from a female and male patient diagnosed with Alzheimer's disease (AD) with different genotypes of a functional copy number variation (CNV) in the AD risk gene CR1 were used to generate integration-free induced pluripotent stem cells (iPSCs) employing episomal plasmids expressing OCT4, SOX2, NANOG, LIN28, c-MYC and L-MYC. The iPSCs retained the CR1 CNV, and comparative transcriptome analyses with the human embryonic stem cell line H1 revealed a Pearson correlation of 0.956 for AD1-CR10 and 0.908 for AD1-CR14.

Phenotypic characteristics of Alzheimer patients carrying an ABCA7 mutation

Objective:

To generate a clinical and pathologic phenotype of patients carrying rare loss-of-function mutations in ABCA7, identified in a Belgian Alzheimer patient cohort and in an autosomal dominant family.

Methods:

We performed a retrospective review of available data records, medical records, results of CSF analyses and neuroimaging studies, and neuropathology data.

Results:

The mean onset age of the mutation carriers (n = 22) was 73.4 ± 8.4 years with a wide age range of 36 (54–90) years, which was independent of APOE genotype and cerebrovascular disease. The mean disease duration was 5.7 ± 3.0 years (range 2–12 years). A positive family history was recorded for 10 carriers (45.5%). All patient carriers except one presented with memory complaints. The 4 autopsied brains showed typical immunohistochemical changes of late-onset Alzheimer disease.

Conclusions:

All patients carrying a loss-of-function mutation in ABCA7 exhibited a classical Alzheimer disease phenotype, though with a striking wide onset age range, suggesting the influence of unknown modifying factors.

Reduced secreted clusterin as a mechanism for Alzheimer-associated CLU mutations

BACKGROUND

The clusterin (CLU) gene has been identified as an important risk locus for Alzheimer's disease (AD). Although the actual risk-increasing polymorphisms at this locus remain to be identified, we previously observed an increased frequency of rare non-synonymous mutations and small insertion-deletions of CLU in AD patients, which specifically clustered in the β-chain domain of CLU. Nonetheless the pathogenic nature of these variants remained unclear. Here we report a novel non-synonymous CLU mutation (p.I360N) in a Belgian Alzheimer patient and have explored the pathogenic nature of this and 10 additional CLU mutations on protein localization and secretion in vitro using immunocytochemistry, immunodetection and ELISAs.

RESULTS

Three patient-specific CLU mutations in the β-chain (p.I303NfsX13, p.R338W and p.I360N) caused an alteration of the subcellular CLU localization and diminished CLU transport through the secretory pathway, indicative of possible degradation mechanisms. For these mutations, significantly reduced CLU intensity was observed in the Golgi while almost all CLU protein was exclusively present in the endoplasmic reticulum. This was further confirmed by diminished CLU secretion in HEK293T and HEK293 FLp-In cell lines.

CONCLUSIONS

Our data lend further support to the contribution of rare coding CLU mutations in the pathogenesis of neurodegenerative diseases. Functional analyses suggest reduced secretion of the CLU protein as the mode of action for three of the examined CLU mutations. One of those is a frameshift mutation leading to a loss of secreted protein, and the other two mutations are amino acid substitutions in the disulfide bridge region, possibly interfering with heterodimerization of the α- and β-chain of CLU.

A 22-single nucleotide polymorphism Alzheimer's disease risk score correlates with family history, onset age, and cerebrospinal fluid Aβ42

INTRODUCTION

The ability to identify individuals at increased genetic risk for Alzheimer's disease (AD) may streamline biomarker and drug trials and aid clinical and personal decision making.

METHODS

We evaluated the discriminative ability of a genetic risk score (GRS) covering 22 published genetic risk loci for AD in 1162 Flanders-Belgian AD patients and 1019 controls and assessed correlations with family history, onset age, and cerebrospinal fluid (CSF) biomarkers (Aβ1-42, T-Tau, P-Tau181P).

RESULTS

A GRS including all single nucleotide polymorphisms (SNPs) and age-specific APOE ε4 weights reached area under the curve (AUC) 0.70, which increased to AUC 0.78 for patients with familial predisposition. Risk of AD increased with GRS (odds ratio, 2.32 (95% confidence interval 2.08-2.58 per unit; P < 1.0e(-15)). Onset age and CSF Aβ1-42 decreased with increasing GRS (Ponset_age = 9.0e(-11); PAβ = 8.9e(-7)).

DISCUSSION

The discriminative ability of this 22-SNP GRS is still limited, but these data illustrate that incorporation of age-specific weights improves discriminative ability. GRS-phenotype correlations highlight the feasibility of identifying individuals at highest susceptibility.

Decreased expression of ABAT and STC2 hallmarks ER-positive inflammatory breast cancer and endocrine therapy resistance in advanced disease

BACKGROUND

Patients with Estrogen Receptor α-positive (ER+) Inflammatory Breast Cancer (IBC) are less responsive to endocrine therapy compared with ER+ non-IBC (nIBC) patients. The study of ER+ IBC samples might reveal biomarkers for endocrine resistant breast cancer.

MATERIALS & METHODS

Gene expression profiles of ER+ samples from 201 patients were explored for genes that discriminated between IBC and nIBC. Classifier genes were applied onto clinically annotated expression data from 947 patients with ER+ breast cancer and validated with RT-qPCR for 231 patients treated with first-line tamoxifen. Relationships with metastasis-free survival (MFS) and progression-free survival (PFS) following adjuvant and first-line endocrine treatment, respectively, were investigated using Cox regression analysis.

RESULTS

A metagene of six genes including the genes encoding for 4-aminobutyrate aminotransferase (ABAT) and Stanniocalcin-2 (STC2) were identified to distinguish 22 ER+ IBC from 43 ER+ nIBC patients and remained discriminatory in an independent series of 136 patients. The metagene and two genes were not prognostic in 517 (neo)adjuvant untreated lymph node-negative ER+ nIBC breast cancer patients. Only ABAT was related to outcome in 250 patients treated with adjuvant tamoxifen. Three independent series of in total 411 patients with advanced disease showed increased metagene scores and decreased expression of ABAT and STC2 to be correlated with poor first-line endocrine therapy outcome. The biomarkers remained predictive for first-line tamoxifen treatment outcome in multivariate analysis including traditional factors or published signatures. In an exploratory analysis, ABAT and STC2 protein expression levels had no relation with PFS after first-line tamoxifen.

CONCLUSIONS

This study utilized ER+ IBC to identify a metagene including ABAT and STC2 as predictive biomarkers for endocrine therapy resistance.

C9orf72 G4C2 repeat expansions in Alzheimer's disease and mild cognitive impairment

C9orf72 G4C2 repeat expansion is a major cause of amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Its role in Alzheimer's disease (AD) is less clear. We assessed the prevalence of G4C2 pathogenic repeat expansions in Flanders-Belgian patients with clinical AD or mild cognitive impairment (MCI). In addition, we studied the effect of non-pathogenic G4C2 repeat length variability on susceptibility to AD, and on AD cerebrospinal fluid (CSF) biomarker levels. A pathogenic repeat expansion was identified in 5 of 1217 AD patients (frequency <1%). No pathogenic expansions were observed in patients with MCI (n = 200) or control individuals (n = 1119). Nonpathogenic repeat length variability was not associated with AD, risk of conversion to AD in MCI individuals, or CSF biomarker levels. We conclude that pathogenic C9orf72 G4C2 repeat expansions can be detected in clinical AD patients and could act as a contributor to AD pathogenesis. Non-pathogenic repeat length variability did not affect risk of AD or MCI, nor AD biomarker levels in CSF, indicating that C9orf72 is not a direct AD risk factor.

Fractal analysis of amyloid plaques in Alzheimer's disease patients and mouse models

The varied morphological and biochemical forms in which amyloid deposits in brain of Alzheimer's disease (AD) patients are complex and their mechanisms of formation are not completely understood. Here we investigated the ability of fractal dimension (FD) to differentiate between the textures of commonly observed amyloid plaques in sporadic and familial AD patients and aged-control individuals as well as in transgenic mouse models of amyloidosis. Studying more than 6000 amyloid plaques immunostained for total Aβ (Aβt), Aβ40 or Aβ42, we show here that Aβ40 FD could efficiently differentiate between (i) AD patients and aged-control individuals (P<0.001); (ii) sporadic and familial AD due to presenilin-1 or APP (A692G) mutations (P<0.001); and (iii) three transgenic mouse models of different genotypes (P<0.001). Furthermore, while diffuse and dense-core plaques present in humans and transgenic mice had comparable FDs, both Aβt and Aβ42 FD could also differentiate diffuse plaques from other plaque types in both species (P<0.001). Our data suggest that plaque FD could be a valuable tool for objective, computer-oriented AD diagnosis as well as for genotype-phenotype correlations of AD.