Publications by authors named "Guojun Bu"

251 Publications

Comparison of Plasma Phosphorylated Tau Species With Amyloid and Tau Positron Emission Tomography, Neurodegeneration, Vascular Pathology, and Cognitive Outcomes.

JAMA Neurol 2021 Jul 26. Epub 2021 Jul 26.

Department of Quantitative Health Sciences, Mayo Clinic, Rochester, Minnesota.

Importance: Cerebrospinal fluid phosphorylated tau (p-tau) 181, p-tau217, and p-tau231 are associated with neuropathological outcomes, but a comparison of these p-tau isoforms in blood samples is needed.

Objective: To conduct a head-to-head comparison of plasma p-tau181 and p-tau231 measured on the single-molecule array (Simoa) platform and p-tau181 and p-tau217 measured on the Meso Scale Discovery (MSD) platform on amyloid and tau positron emission tomography (PET) measures, neurodegeneration, vascular pathology, and cognitive outcomes.

Design, Setting, And Participants: This study included data from the Mayo Clinic Study on Aging collected from March 1, 2015, to September 30, 2017, and analyzed between December 15, 2020, and May 17, 2021. Associations between the 4 plasma p-tau measures and dichotomous amyloid PET, metaregion of interest tau PET, and entorhinal cortex tau PET were analyzed using logistic regression models; the predictive accuracy was summarized using area under the receiver operating characteristic curve (AUROC) statistic. Of 1329 participants without dementia and with p-tau181 and p-tau217 on MSD, 200 participants with plasma p-tau181 and p-tau231 on Simoa and magnetic resonance imaging and amyloid and tau PET data at the same study visit were eligible.

Main Outcomes And Measures: Primary outcomes included amyloid (greater than 1.48 standardized uptake value ratio) and tau PET, white matter hyperintensities, white matter microstructural integrity (fractional anisotropy genu of corpus callosum and hippocampal cingulum bundle), and cognition.

Results: Of 200 included participants, 101 (50.5%) were male, and the median (interquartile range [IQR]) age was 79.5 (71.1-84.1) years. A total of 177 were cognitively unimpaired (CU) and 23 had mild cognitive impairment. Compared with amyloid-negative CU participants, among amyloid-positive CU participants, the median (IQR) Simoa p-tau181 measure was 49% higher (2.58 [2.00-3.72] vs 1.73 [1.45-2.13] pg/mL), MSD p-tau181 measure was 53% higher (1.22 [0.91-1.56] vs 0.80 [0.66-0.97] pg/mL), MSD p-tau217 measure was 77% higher (0.23 [0.17-0.34] vs 0.13 [0.09-0.18] pg/mL), and Simoa p-tau231 measure was 49% higher (20.21 [15.60-25.41] vs 14.27 [11.27-18.10] pg/mL). There were no differences between the p-tau species for amyloid PET and tau PET metaregions of interest. However, among CU participants, both MSD p-tau181 and MSD p-tau217 more accurately predicted abnormal entorhinal cortex tau PET than Simoa p-tau181 (MSD p-tau181: AUROC, 0.80 vs 0.70; P = .046; MSD p-tau217: AUROC, 0.81 vs 0.70; P = .04). MSD p-tau181 and p-tau217 and Simoa p-tau181, but not p-tau231, were associated with greater white matter hyperintensity volume and lower white matter microstructural integrity.

Conclusions And Relevance: In this largely presymptomatic population, these results suggest subtle differences across plasma p-tau species and platforms for the prediction of amyloid and tau PET and magnetic resonance imaging measures of cerebrovascular and Alzheimer-related pathology.
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http://dx.doi.org/10.1001/jamaneurol.2021.2293DOI Listing
July 2021

Generation and validation of knockout human iPSC-derived cerebral organoids.

STAR Protoc 2021 Jun 5;2(2):100571. Epub 2021 Jun 5.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.

Apolipoprotein E (apoE) is a major lipid carrier in the brain and closely associated with the pathogenesis of Alzheimer's disease (AD). Here, we describe a protocol for efficient knockout of in human induced pluripotent stem cells (iPSCs) using the CRISPR-Cas9 system. We obtain homozygous knockout ( ) iPSCs and further validate the deficiency of apoE in iPSC-derived cerebral organoids. cerebral organoids can serve as a useful tool to study apoE functions and apoE-related pathogenic mechanisms in AD. For complete details on the use and execution of this protocol, please refer to Zhao et al. (2020).
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http://dx.doi.org/10.1016/j.xpro.2021.100571DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8190508PMC
June 2021

Effect of Osteoporosis on Adjacent Segmental Degeneration After Posterior Lumbar Interbody Fusion Under Whole Body Vibration.

World Neurosurg 2021 Jun 12. Epub 2021 Jun 12.

School of Chinese Medicine, Jinan University, Guangzhou, China. Electronic address:

Background: Adjacent segmental degeneration (ASD) is one of the common complications after posterior lumbar interbody fusion (PLIF). Both whole body vibration (WBV) and osteoporosis are important factors associated with the biomechanics of the lumbar spine. However, to the best of our knowledge, no studies have investigated the effects of osteoporosis on ASD after PLIF under WBV.

Methods: In the present study, using one normal model, one PLIF model and one PLIF with osteoporosis model of the L1-S1 segment were developed. A 5-Hz, 40-N sinusoidal vertical load was imposed on the superior surface of L1 of each model to simulate WBV, and the dynamic responses and maximal values of intradiscal pressure, shear stress on annulus fibrosus, total deformation, and disc bulge were evaluated in the L1-L2, L2-L3, L3-L4, and L5-S1 segments.

Results: At the L1-L2, L2-L3, and L3-L4 levels, the differences in the dynamic responses and maximal values in intradiscal pressure, shear stress, total deformation, and disc bulge between the PLIF and PLIF with osteoporosis models were slight. However, at the L5-S1 level, the dynamic response curves and maximal intradiscal pressure, shear stress, and disc bulge values in the PLIF with osteoporosis model were significantly lower than those in the PLIF model.

Conclusions: Osteoporosis can mitigate the development of ASD in the lower adjacent segment but has no obvious influence on the upper adjacent segments during WBV.
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http://dx.doi.org/10.1016/j.wneu.2021.06.031DOI Listing
June 2021

Interaction Between APOE Genotype and Diabetes in Longevity.

J Alzheimers Dis 2021 ;82(2):719-726

Department of Aging Neurobiology, Center for Development of Advanced Medicine for Dementia, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan.

Background: While both apolipoprotein E (APOE) genotype and diabetes affect longevity as well as Alzheimer's disease, their relationship remains to be elucidated.

Objective: The current study investigated the potential interaction between diabetes and APOE for lifespan and their relationship with cognitive status.

Methods: We reviewed the National Alzheimer's Coordinating Center (NACC) dataset, which documents longitudinally clinical records of 24,967 individuals with APOE genotype and diabetic status.

Results: Diabetes was associated with shorter lifespan in APOE3 carriers (n = 12,415, HR = 1.29, 95%CI = 1.17-1.42, p < 0.001) and APOE2 carriers (n = 2,390, HR = 1.37, 95%CI = 1.10-1.69, p = 0.016), while such associations were weaker and not significant in APOE4 carriers (n = 9,490, HR = 1.11, 95%CI = 0.99-1.24, p = 0.162). As there is a significant interactive effect of cognitive status and diabetes on lifespan (p < 0.001), we stratified subjects by cognitive status and observed persistent APOE-dependent harmful effects of diabetes in nondemented individuals but not demented individuals. Notably, questionnaire-based activity status, with which we previously observed an association between APOE genotype and longevity, was also significantly affected by diabetes only in non-APOE4 carriers.

Conclusion: The effects of diabetes on longevity vary among APOE genotype. These effects are observed in nondemented individuals and are potentially associated with activity status during their lifespan.
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http://dx.doi.org/10.3233/JAD-210125DOI Listing
January 2021

Genome-wide analysis identifies a novel LINC-PINT splice variant associated with vascular amyloid pathology in Alzheimer's disease.

Acta Neuropathol Commun 2021 05 21;9(1):93. Epub 2021 May 21.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA.

Cerebral amyloid angiopathy (CAA) contributes to accelerated cognitive decline in Alzheimer's disease (AD) dementia and is a common finding at autopsy. The APOEε4 allele and male sex have previously been reported to associate with increased CAA in AD. To inform biomarker and therapeutic target discovery, we aimed to identify additional genetic risk factors and biological pathways involved in this vascular component of AD etiology. We present a genome-wide association study of CAA pathology in AD cases and report sex- and APOE-stratified assessment of this phenotype. Genome-wide genotypes were collected from 853 neuropathology-confirmed AD cases scored for CAA across five brain regions, and imputed to the Haplotype Reference Consortium panel. Key variables and genome-wide genotypes were tested for association with CAA in all individuals and in sex and APOEε4 stratified subsets. Pathway enrichment was run for each of the genetic analyses. Implicated loci were further investigated for functional consequences using brain transcriptome data from 1,186 samples representing seven brain regions profiled as part of the AMP-AD consortium. We confirmed association of male sex, AD neuropathology and APOEε4 with increased CAA, and identified a novel locus, LINC-PINT, associated with lower CAA amongst APOEε4-negative individuals (rs10234094-C, beta = -3.70 [95% CI -0.49--0.24]; p = 1.63E-08). Transcriptome profiling revealed higher LINC-PINT expression levels in AD cases, and association of rs10234094-C with altered LINC-PINT splicing. Pathway analysis indicates variation in genes involved in neuronal health and function are linked to CAA in AD patients. Further studies in additional and diverse cohorts are needed to assess broader translation of our findings.
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http://dx.doi.org/10.1186/s40478-021-01199-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8147512PMC
May 2021

ABCA7 Regulates Brain Fatty Acid Metabolism During LPS-Induced Acute Inflammation.

Front Neurosci 2021 7;15:647974. Epub 2021 Apr 7.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, United States.

The ATP binding cassette subfamily A member 7 () gene is one of the significant susceptibility loci for Alzheimer's disease (AD). Furthermore, ABCA7 loss of function variants resulting from premature termination codon in the gene are associated with increased risk for AD. ABCA7 belongs to the ABC transporter family, which mediates the transport of diverse metabolites across the cell membrane. ABCA7 is also involved in modulating immune responses. Because the immune system and lipid metabolism causatively engage in the pathogenesis of AD, we investigated how ABCA7 haplodeficiency modulates the metabolic profile in mouse brains during acute immune response using a metabolomics approach through LC/Q-TOF-MS. Peripheral lipopolysaccharide (LPS) stimulation substantially influenced the metabolite content in the cortex, however, the effect on metabolic profiles in heterozygous knockout mice ( ) was modest compared to that in the control wild-type mice. Weighted gene co-expression network analysis (WGCNA) of the metabolomics dataset identified two modules influenced by LPS administration and ABCA7 haplodeficiency, in which glycerophospholipid metabolism, linoleic acid metabolism, and α-linolenic acid metabolism were identified as major pathways. Consistent with these findings, we also found that LPS stimulation increased the brain levels of eicosapentaenoic acid, oleic acid, and palmitic acid in mice, but not control mice. Together, our results indicate that ABCA7 is involved in the crosstalk between fatty acid metabolism and inflammation in the brain, and disturbances in these pathways may contribute to the risk for AD.
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http://dx.doi.org/10.3389/fnins.2021.647974DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8059705PMC
April 2021

Loss of Tmem106b leads to cerebellum Purkinje cell death and motor deficits.

Brain Pathol 2021 May 11;31(3):e12945. Epub 2021 Mar 11.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

TMEM106B has been recently implicated in multiple neurodegenerative diseases. Here, Rademakers et al. report a late-onset cerebellar Purkinje cell loss and progressive decline in motor function and gait deficits in a conventional Tmem106b-/- mouse model. By using high-power microscopy and bulk RNA sequencing, the authors further identify lysosomal and immune dysfunction as potential underlying mechanisms of the Purkinje cell loss.
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http://dx.doi.org/10.1111/bpa.12945DOI Listing
May 2021

Vascular ApoE4 Impairs Behavior by Modulating Gliovascular Function.

Neuron 2021 02 14;109(3):438-447.e6. Epub 2020 Dec 14.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA; Neuroscience Graduate Program, Mayo Clinic, Jacksonville, FL 32224, USA. Electronic address:

The ε4 allele of the apolipoprotein E gene (APOE4) is a strong genetic risk factor for Alzheimer's disease (AD) and multiple vascular conditions. ApoE is abundantly expressed in multiple brain cell types, including astrocytes, microglia, and vascular mural cells (VMCs). Here, we show that VMC-specific expression of apoE4 in mice impairs behavior and cerebrovascular function. Expression of either apoE3 or apoE4 in VMCs was sufficient to rescue the hypercholesterolemia and atherosclerosis phenotypes seen in Apoe knockout mice. Intriguingly, vascular expression of apoE4, but not apoE3, reduced arteriole blood flow, impaired spatial learning, and increased anxiety-like phenotypes. Single-cell RNA sequencing of vascular and glial cells revealed that apoE4 in VMCs was associated with astrocyte activation, while apoE3 was linked to angiogenic signature in pericytes. Together, our data support cell-autonomous effects of vascular apoE on brain homeostasis in an isoform-dependent manner, suggesting a critical contribution of vascular apoE to AD pathogenesis.
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http://dx.doi.org/10.1016/j.neuron.2020.11.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7864888PMC
February 2021

Astrocyte-derived clusterin suppresses amyloid formation in vivo.

Mol Neurodegener 2020 11 27;15(1):71. Epub 2020 Nov 27.

Department of Neuroscience, Mayo Clinic, Collaborative Research Building CR03-010, 13400 E. Shea Blvd, Scottsdale, AZ, 85259, USA.

Background: Accumulation of amyloid-β (Aβ) peptide in the brain is a pathological hallmark of Alzheimer's disease (AD). The clusterin (CLU) gene confers a risk for AD and CLU is highly upregulated in AD patients, with the common non-coding, protective CLU variants associated with increased expression. Although there is strong evidence implicating CLU in amyloid metabolism, the exact mechanism underlying the CLU involvement in AD is not fully understood or whether physiologic alterations of CLU levels in the brain would be protective.

Results: We used a gene delivery approach to overexpress CLU in astrocytes, the major source of CLU expression in the brain. We found that CLU overexpression resulted in a significant reduction of total and fibrillar amyloid in both cortex and hippocampus in the APP/PS1 mouse model of AD amyloidosis. CLU overexpression also ameliorated amyloid-associated neurotoxicity and gliosis. To complement these overexpression studies, we also analyzed the effects of haploinsufficiency of Clu using heterozygous (Clu) mice and control littermates in the APP/PS1 model. CLU reduction led to a substantial increase in the amyloid plaque load in both cortex and hippocampus in APP/PS1; Clu mice compared to wild-type (APP/PS1; Clu) littermate controls, with a concomitant increase in neuritic dystrophy and gliosis.

Conclusions: Thus, both physiologic ~ 30% overexpression or ~ 50% reduction in CLU have substantial impacts on amyloid load and associated pathologies. Our results demonstrate that CLU plays a major role in Aβ accumulation in the brain and suggest that efforts aimed at CLU upregulation via pharmacological or gene delivery approaches offer a promising therapeutic strategy to regulate amyloid pathology.
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http://dx.doi.org/10.1186/s13024-020-00416-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694353PMC
November 2020

APOE2: protective mechanism and therapeutic implications for Alzheimer's disease.

Mol Neurodegener 2020 11 4;15(1):63. Epub 2020 Nov 4.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

Investigations of apolipoprotein E (APOE) gene, the major genetic risk modifier for Alzheimer's disease (AD), have yielded significant insights into the pathogenic mechanism. Among the three common coding variants, APOE*ε4 increases, whereas APOE*ε2 decreases the risk of late-onset AD compared with APOE*ε3. Despite increased understanding of the detrimental effect of APOE*ε4, it remains unclear how APOE*ε2 confers protection against AD. Accumulating evidence suggests that APOE*ε2 protects against AD through both amyloid-β (Aβ)-dependent and independent mechanisms. In addition, APOE*ε2 has been identified as a longevity gene, suggesting a systemic effect of APOE*ε2 on the aging process. However, APOE*ε2 is not entirely benign; APOE*ε2 carriers exhibit increased risk of certain cerebrovascular diseases and neurological disorders. Here, we review evidence from both human and animal studies demonstrating the protective effect of APOE*ε2 against AD and propose a working model depicting potential underlying mechanisms. Finally, we discuss potential therapeutic strategies designed to leverage the protective effect of APOE2 to treat AD.
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http://dx.doi.org/10.1186/s13024-020-00413-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7640652PMC
November 2020

APOE4 exacerbates synapse loss and neurodegeneration in Alzheimer's disease patient iPSC-derived cerebral organoids.

Nat Commun 2020 11 2;11(1):5540. Epub 2020 Nov 2.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA.

APOE4 is the strongest genetic risk factor associated with late-onset Alzheimer's disease (AD). To address the underlying mechanism, we develop cerebral organoid models using induced pluripotent stem cells (iPSCs) with APOE ε3/ε3 or ε4/ε4 genotype from individuals with either normal cognition or AD dementia. Cerebral organoids from AD patients carrying APOE ε4/ε4 show greater apoptosis and decreased synaptic integrity. While AD patient-derived cerebral organoids have increased levels of Aβ and phosphorylated tau compared to healthy subject-derived cerebral organoids, APOE4 exacerbates tau pathology in both healthy subject-derived and AD patient-derived organoids. Transcriptomics analysis by RNA-sequencing reveals that cerebral organoids from AD patients are associated with an enhancement of stress granules and disrupted RNA metabolism. Importantly, isogenic conversion of APOE4 to APOE3 attenuates the APOE4-related phenotypes in cerebral organoids from AD patients. Together, our study using human iPSC-organoids recapitulates APOE4-related phenotypes and suggests APOE4-related degenerative pathways contributing to AD pathogenesis.
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http://dx.doi.org/10.1038/s41467-020-19264-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608683PMC
November 2020

Sensitive ELISA-based detection method for the mitophagy marker p-S65-Ub in human cells, autopsy brain, and blood samples.

Autophagy 2020 Oct 28:1-16. Epub 2020 Oct 28.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

Mitochondrial dysfunction is an early, imminent event in neurodegenerative disorders including Parkinson disease (PD) and Alzheimer disease (AD). The enzymatic pair PINK1 and PRKN/Parkin recognize and transiently label damaged mitochondria with ubiquitin (Ub) phosphorylated at Ser65 (p-S65-Ub) as a signal for degradation via the autophagy-lysosome system (mitophagy). Despite its discovery in cell culture several years ago, robust and quantitative detection of altered mitophagy has remained challenging. Here we developed a sandwich ELISA targeting p-S65-Ub with the goal to assess mitophagy levels in mouse brain and in human clinical and pathological samples. We characterized five total Ub and four p-S65-Ub antibodies by several techniques and found significant differences in their ability to recognize phosphorylated Ub. The most sensitive antibody pair detected recombinant p-S65-Ub chains in the femtomolar to low picomolar range depending on the poly-Ub chain linkage. Importantly, this ELISA was able to assess very low baseline mitophagy levels in unstressed human cells and in brains from wild-type and knockout mice as well as elevated p-S65-Ub levels in autopsied frontal cortex from AD patients vs. control cases. Moreover, the assay allowed detection of p-S65-Ub in blood plasma and was able to discriminate between mutation carriers and controls. In summary, we developed a robust and sensitive tool to measure mitophagy levels in cells, tissue, and body fluids. Our data strongly support the idea that the stress-activated PINK1-PRKN mitophagy pathway is constitutively active in mice and humans under unstimulated, physiological and elevated in diseased, pathological conditions.: Ab: antibody; AD: Alzheimer disease; AP: alkaline phosphatase; CV: coefficient of variation; ECL: electrochemiluminescence; KO: knockout; LoB: Limit of Blank; LoD: Limit of Detection; LoQ: Limit of Quantification; MSD: meso scale discovery; PD: Parkinson disease; p-S65-PRKN: phosphorylated PRKN at serine 65; p-S65-Ub: phosphorylated ubiquitin at serine 65; Std.Dev.: standard deviation; Ub: ubiquitin; WT: wild type.
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http://dx.doi.org/10.1080/15548627.2020.1834712DOI Listing
October 2020

Mitophagy alterations in Alzheimer's disease are associated with granulovacuolar degeneration and early tau pathology.

Alzheimers Dement 2020 Oct 8. Epub 2020 Oct 8.

Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, USA.

Introduction: The cytoprotective PTEN-induced kinase 1 (PINK1)-parkin RBR E3 ubiquitin protein ligase (PRKN) pathway selectively labels damaged mitochondria with phosphorylated ubiquitin (pS65-Ub) for their autophagic removal (mitophagy). Because dysfunctions of mitochondria and degradation pathways are early features of Alzheimer's disease (AD), mitophagy impairments may contribute to the pathogenesis.

Methods: Morphology, levels, and distribution of the mitophagy tag pS65-Ub were evaluated by biochemical analyses combined with tissue and single cell imaging in AD autopsy brain and in transgenic mouse models.

Results: Analyses revealed significant increases of pS65-Ub levels in AD brain, which strongly correlated with granulovacuolar degeneration (GVD) and early phospho-tau deposits, but were independent of amyloid beta pathology. Single cell analyses revealed predominant co-localization of pS65-Ub with mitochondria, GVD bodies, and/or lysosomes depending on the brain region analyzed.

Discussion: Our study highlights mitophagy alterations in AD that are associated with early tau pathology, and suggests that distinct mitochondrial, autophagic, and/or lysosomal failure may contribute to the selective vulnerability in disease.
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http://dx.doi.org/10.1002/alz.12198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048674PMC
October 2020

Toward allele-specific targeting therapy and pharmacodynamic marker for spinocerebellar ataxia type 3.

Sci Transl Med 2020 10;12(566)

Department of Pathology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan.

Spinocerebellar ataxia type 3 (SCA3), caused by a CAG repeat expansion in the ataxin-3 gene (), is characterized by neuronal polyglutamine (polyQ) ATXN3 protein aggregates. Although there is no cure for SCA3, gene-silencing approaches to reduce toxic polyQ ATXN3 showed promise in preclinical models. However, a major limitation in translating putative treatments for this rare disease to the clinic is the lack of pharmacodynamic markers for use in clinical trials. Here, we developed an immunoassay that readily detects polyQ ATXN3 proteins in human biological fluids and discriminates patients with SCA3 from healthy controls and individuals with other ataxias. We show that polyQ ATXN3 serves as a marker of target engagement in human fibroblasts, which may bode well for its use in clinical trials. Last, we identified a single-nucleotide polymorphism that strongly associates with the expanded allele, thus providing an exciting drug target to abrogate detrimental events initiated by mutant ATXN3. Gene-silencing strategies for several repeat diseases are well under way, and our results are expected to improve clinical trial preparedness for SCA3 therapies.
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http://dx.doi.org/10.1126/scitranslmed.abb7086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7927160PMC
October 2020

is associated with longevity independent of Alzheimer's disease.

Elife 2020 10 19;9. Epub 2020 Oct 19.

Department of Neuroscience, Mayo Clinic, Jacksonville, United States.

Although the ε2 allele of apolipoprotein E () benefits longevity, its mechanism is not understood. The protective effects of the 2 on Alzheimer's disease (AD) risk, particularly through their effects on amyloid or tau accumulation, may confound effects on longevity. Herein, we showed that the association between and longer lifespan persisted irrespective of AD status, including its neuropathology, by analyzing clinical datasets as well as animal models. Notably, was associated with preserved activity during aging, which also associated with lifespan. In animal models, distinct apoE isoform levels, where has the highest, were correlated with activity levels, while some forms of cholesterol and triglycerides were associated with apoE and activity levels. These results indicate that can contribute to longevity independent of AD. Preserved activity would be an early-observable feature of -mediated longevity, where higher levels of apoE2 and its-associated lipid metabolism might be involved.
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http://dx.doi.org/10.7554/eLife.62199DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7588231PMC
October 2020

Tau and apolipoprotein E modulate cerebrovascular tight junction integrity independent of cerebral amyloid angiopathy in Alzheimer's disease.

Alzheimers Dement 2020 10 22;16(10):1372-1383. Epub 2020 Aug 22.

Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, USA.

Introduction: Cerebrovascular pathologies including cerebral amyloid angiopathy (CAA) and blood-brain barrier (BBB) dysregulation are prominent features in the majority of Alzheimer's disease (AD) cases.

Methods: We performed neuropathologic and biochemical studies on a large, neuropathologically confirmed human AD cohort (N = 469). Amounts of endothelial tight junction proteins claudin-5 (CLDN5) and occludin (OCLN), and major AD-related molecules (amyloid beta [Aβ40], Aβ42, tau, p-tau, and apolipoprotein E) in the temporal cortex were assessed by ELISA.

Results: Higher levels of soluble tau, insoluble p-tau, and apolipoprotein E (apoE) were independently correlated with lower levels of endothelial tight junction proteins CLDN5 and OCLN in AD brains. Although high Aβ40 levels, APOE ε4, and male sex were predominantly associated with exacerbated CAA severity, those factors did not influence tight junction protein levels.

Discussion: Refining the molecular mechanisms connecting tau, Aβ, and apoE with cerebrovascular pathologies is critical for greater understanding of AD pathogenesis and establishing effective therapeutic interventions for the disease.
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http://dx.doi.org/10.1002/alz.12104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8103951PMC
October 2020

Clearance of interstitial fluid (ISF) and CSF (CLIC) group-part of Vascular Professional Interest Area (PIA): Cerebrovascular disease and the failure of elimination of Amyloid-β from the brain and retina with age and Alzheimer's disease-Opportunities for Therapy.

Alzheimers Dement (Amst) 2020 3;12(1):e12053. Epub 2020 Aug 3.

University of Milano - Bicocca Monza Italy.

Two of the key functions of arteries in the brain are (1) the well-recognized supply of blood via the vascular lumen and (2) the emerging role for the arterial walls as routes for the elimination of interstitial fluid (ISF) and soluble metabolites, such as amyloid beta (Aβ), from the brain and retina. As the brain and retina possess no conventional lymphatic vessels, fluid drainage toward peripheral lymph nodes is mediated via transport along basement membranes in the walls of capillaries and arteries that form the intramural peri-arterial drainage (IPAD) system. IPAD tends to fail as arteries age but the mechanisms underlying the failure are unclear. In some people this is reflected in the accumulation of Aβ plaques in the brain in Alzheimer's disease (AD) and deposition of Aβ within artery walls as cerebral amyloid angiopathy (CAA). Knowledge of the dynamics of IPAD and why it fails with age is essential for establishing diagnostic tests for the early stages of the disease and for devising therapies that promote the clearance of Aβ in the prevention and treatment of AD and CAA. This editorial is intended to introduce the rationale that has led to the establishment of the Clearance of Interstitial Fluid (ISF) and CSF (CLIC) group, within the Vascular Professional Interest Area of the Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment.
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http://dx.doi.org/10.1002/dad2.12053DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7396859PMC
August 2020

Loss of Tmem106b exacerbates FTLD pathologies and causes motor deficits in progranulin-deficient mice.

EMBO Rep 2020 10 5;21(10):e50197. Epub 2020 Aug 5.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

Progranulin (PGRN) and transmembrane protein 106B (TMEM106B) are important lysosomal proteins implicated in frontotemporal lobar degeneration (FTLD) and other neurodegenerative disorders. Loss-of-function mutations in progranulin (GRN) are a common cause of FTLD, while TMEM106B variants have been shown to act as disease modifiers in FTLD. Overexpression of TMEM106B leads to lysosomal dysfunction, while loss of Tmem106b ameliorates lysosomal and FTLD-related pathologies in young Grn mice, suggesting that lowering TMEM106B might be an attractive strategy for therapeutic treatment of FTLD-GRN. Here, we generate and characterize older Tmem106b Grn double knockout mice, which unexpectedly show severe motor deficits and spinal cord motor neuron and myelin loss, leading to paralysis and premature death at 11-12 months. Compared to Grn , Tmem106b Grn mice have exacerbated FTLD-related pathologies, including microgliosis, astrogliosis, ubiquitin, and phospho-Tdp43 inclusions, as well as worsening of lysosomal and autophagic deficits. Our findings confirm a functional interaction between Tmem106b and Pgrn and underscore the need to rethink whether modulating TMEM106B levels is a viable therapeutic strategy.
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http://dx.doi.org/10.15252/embr.202050197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7534638PMC
October 2020

An agnostic reevaluation of the amyloid cascade hypothesis of Alzheimer's disease pathogenesis: The role of APP homeostasis.

Alzheimers Dement 2020 11 26;16(11):1582-1590. Epub 2020 Jun 26.

Department of Neuroscience, Mayo Clinic Florida, Jacksonville, Florida, USA.

Objective: To reassess the role of amyloid beta (Aβ) and the amyloid precursor protein (APP) system in the pathogenesis of Alzheimer's disease (AD).

Background: APP is a cell adhesion molecule that has been highly conserved over the course of phylogeny that has critical roles in brain development, synaptic plasticity, and the brain's intrinsic immune system. The amyloid cascade hypothesis describes a relatively linear, deterministic sequence of events triggered by a gain of Aβ peptide fragment toxicity that results in neurodegeneration and cognitive loss, yet well designed immunotherapy and beta secretase inhibitor trials that have successfully targeted Aβ have failed to have any consistent effects on the steady decline of cognition.

New/updated Hypothesis: Mutations of the APP and presenilin genes not only alter the ratio of longer to shorter Aβ fragments (resulting in a gain of Aβ toxicity), but also disrupt the normal homeostatic roles of their respective proteins. The evolutionary history, physiological importance, and complexity of the APP and presenilin systems, as well as other critical components including tau and apolipoprotein E (APOE) imply that altered function of such systems could have severe consequences that include but need not be limited to a gain of Aβ toxicity and would more generally result in altered homeostasis of APP-related functions.

Major Challenges Addressed By Our Hypothesis: Challenges that a loss of APP homeostasis addresses better than the more limited gain of Aβ toxicity model include the topographic mismatches between Aβ and tau pathology, the profile and chronology of cognitive and biomarker changes that precede the clinical expression of mild cognitive impairment and dementia, and the disappointments of Aβ targeted therapeutics among others.

Linkage To Other Major Theories: The importance of APP, α- and β-secretases, the presenilins and γ-secretase, as well as tau was recognized by the authors of the amyloid cascade hypothesis, and has since led multiple investigators to propose alternative, more balanced hypotheses including reduced homeostasis and frank loss-of-function of key components that include but go beyond the currently envisioned linear model of Aβ toxicity.
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http://dx.doi.org/10.1002/alz.12124DOI Listing
November 2020

Loss of TMEM106B leads to myelination deficits: implications for frontotemporal dementia treatment strategies.

Brain 2020 06;143(6):1905-1919

Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224, USA.

Genetic variants that define two distinct haplotypes at the TMEM106B locus have been implicated in multiple neurodegenerative diseases and in healthy brain ageing. In frontotemporal dementia (FTD), the high expressing TMEM106B risk haplotype was shown to increase susceptibility for FTD with TDP-43 inclusions (FTD-TDP) and to modify disease penetrance in progranulin mutation carriers (FTD-GRN). To elucidate the biological function of TMEM106B and determine whether lowering TMEM106B may be a viable therapeutic strategy, we performed brain transcriptomic analyses in 8-month-old animals from our recently developed Tmem106b-/- mouse model. We included 10 Tmem106b+/+ (wild-type), 10 Tmem106b+/- and 10 Tmem106-/- mice. The most differentially expressed genes (153 downregulated and 60 upregulated) were identified between Tmem106b-/- and wild-type animals, with an enrichment for genes implicated in myelination-related cellular processes including axon ensheathment and oligodendrocyte differentiation. Co-expression analysis also revealed that the most downregulated group of correlated genes was enriched for myelination-related processes. We further detected a significant loss of OLIG2-positive cells in the corpus callosum of Tmem106b-/- mice, which was present already in young animals (21 days) and persisted until old age (23 months), without worsening. Quantitative polymerase chain reaction revealed a reduction of differentiated but not undifferentiated oligodendrocytes cellular markers. While no obvious changes in myelin were observed at the ultrastructure levels in unchallenged animals, treatment with cuprizone revealed that Tmem106b-/- mice are more susceptible to cuprizone-induced demyelination and have a reduced capacity to remyelinate, a finding which we were able to replicate in a newly generated Tmem106b CRISPR/cas9 knock-out mouse model. Finally, using a TMEM106B HeLa knock-out cell line and primary cultured oligodendrocytes, we determined that loss of TMEM106B leads to abnormalities in the distribution of lysosomes and PLP1. Together these findings reveal an important function for TMEM106B in myelination with possible consequences for therapeutic strategies aimed at lowering TMEM106B levels.
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http://dx.doi.org/10.1093/brain/awaa141DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7296855PMC
June 2020

Cell-based therapy to reduce mortality from COVID-19: Systematic review and meta-analysis of human studies on acute respiratory distress syndrome.

Stem Cells Transl Med 2020 09 29;9(9):1007-1022. Epub 2020 May 29.

Department of Pathology and Laboratory Medicine, Department of Health Policy and Management, Rollins School of Public Health, Emory University, The Marcus Foundation, Atlanta, Georgia, USA.

Severe cases of COVID-19 infection, often leading to death, have been associated with variants of acute respiratory distress syndrome (ARDS). Cell therapy with mesenchymal stromal cells (MSCs) is a potential treatment for COVID-19 ARDS based on preclinical and clinical studies supporting the concept that MSCs modulate the inflammatory and remodeling processes and restore alveolo-capillary barriers. The authors performed a systematic literature review and random-effects meta-analysis to determine the potential value of MSC therapy for treating COVID-19-infected patients with ARDS. Publications in all languages from 1990 to March 31, 2020 were reviewed, yielding 2691 studies, of which nine were included. MSCs were intravenously or intratracheally administered in 117 participants, who were followed for 14 days to 5 years. All MSCs were allogeneic from bone marrow, umbilical cord, menstrual blood, adipose tissue, or unreported sources. Combined mortality showed a favorable trend but did not reach statistical significance. No related serious adverse events were reported and mild adverse events resolved spontaneously. A trend was found of improved radiographic findings, pulmonary function (lung compliance, tidal volumes, PaO /FiO ratio, alveolo-capillary injury), and inflammatory biomarker levels. No comparisons were made between MSCs of different sources.
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http://dx.doi.org/10.1002/sctm.20-0146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7300743PMC
September 2020

Interaction between genotype and diabetes in cognitive decline.

Alzheimers Dement (Amst) 2020 6;12(1):e12006. Epub 2020 Feb 6.

Department of Aging Neurobiology Center for Development of Advanced Medicine for Dementia National Center for Geriatrics and Gerontology Obu Aichi Japan.

Introduction: Although diabetes and apolipoprotein E (apoE) are both significant risk factors for dementia, including Alzheimer's disease, it remains to be clarified how they are related to each other in contributing to the risk of dementia.

Methods: By reviewing the National Alzheimer's Coordinating Center (NACC) clinical records, we investigated whether diabetes affects cognitive decline depending on genotype and their potential relationships with neuropathology.

Results: A significant interaction between diabetes and genotype exists, where diabetes affected cognitive decline in carriers and carriers, but not carriers. Moreover, the presence of vascular pathology was increased by diabetes in carriers, while carriers nearly reached plateau levels irrespective of diabetes.

Discussion: Diabetes accelerates cognitive decline, in part, through accelerating vascular impairment in non- ε4 carriers, but such effects are negligible in carriers, who themselves are already vulnerable to vascular impairment.
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http://dx.doi.org/10.1002/dad2.12006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7085280PMC
February 2020

Alzheimer's Risk Factors Age, APOE Genotype, and Sex Drive Distinct Molecular Pathways.

Neuron 2020 06 20;106(5):727-742.e6. Epub 2020 Mar 20.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.

Evidence suggests interplay among the three major risk factors for Alzheimer's disease (AD): age, APOE genotype, and sex. Here, we present comprehensive datasets and analyses of brain transcriptomes and blood metabolomes from human apoE2-, apoE3-, and apoE4-targeted replacement mice across young, middle, and old ages with both sexes. We found that age had the greatest impact on brain transcriptomes highlighted by an immune module led by Trem2 and Tyrobp, whereas APOE4 was associated with upregulation of multiple Serpina3 genes. Importantly, these networks and gene expression changes were mostly conserved in human brains. Finally, we observed a significant interaction between age, APOE genotype, and sex on unfolded protein response pathway. In the periphery, APOE2 drove distinct blood metabolome profile highlighted by the upregulation of lipid metabolites. Our work identifies unique and interactive molecular pathways underlying AD risk factors providing valuable resources for discovery and validation research in model systems and humans.
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http://dx.doi.org/10.1016/j.neuron.2020.02.034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7388065PMC
June 2020

APOE4 exacerbates α-synuclein pathology and related toxicity independent of amyloid.

Sci Transl Med 2020 02;12(529)

Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.

The apolipoprotein E () ε4 allele is the strongest genetic risk factor for late-onset Alzheimer's disease mainly by driving amyloid-β pathology. Recently, has also been found to be a genetic risk factor for Lewy body dementia (LBD), which includes dementia with Lewy bodies and Parkinson's disease dementia. How drives risk of LBD and whether it has a direct effect on α-synuclein pathology are not clear. Here, we generated a mouse model of synucleinopathy using an adeno-associated virus gene delivery of α-synuclein in human APOE-targeted replacement mice expressing APOE2, APOE3, or APOE4. We found that APOE4, but not APOE2 or APOE3, increased α-synuclein pathology, impaired behavioral performances, worsened neuronal and synaptic loss, and increased astrogliosis at 9 months of age. Transcriptomic profiling in APOE4-expressing α-synuclein mice highlighted altered lipid and energy metabolism and synapse-related pathways. We also observed an effect of on α-synuclein pathology in human postmortem brains with LBD and minimal amyloid pathology. Our data demonstrate a pathogenic role of APOE4 in exacerbating α-synuclein pathology independent of amyloid, providing mechanistic insights into how increases the risk of LBD.
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http://dx.doi.org/10.1126/scitranslmed.aay1809DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8309690PMC
February 2020

Cyclin-Dependent Kinase 5-Dependent BAG3 Degradation Modulates Synaptic Protein Turnover.

Biol Psychiatry 2020 04 21;87(8):756-769. Epub 2019 Nov 21.

Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, Fujian, China. Electronic address:

Background: Synaptic protein dyshomeostasis and functional loss is an early invariant feature of Alzheimer's disease (AD), yet the unifying etiological pathway remains largely unknown. Knowing that cyclin-dependent kinase 5 (CDK5) plays critical roles in synaptic formation and degeneration, its phosphorylation targets were reexamined in search of candidates with direct global impacts on synaptic protein dynamics, and the associated regulatory network was also analyzed.

Methods: Quantitative phosphoproteomics and bioinformatics analyses were performed to identify top-ranked candidates. A series of biochemical assays was used to investigate the associated regulatory signaling networks. Histological, electrochemical, and behavioral assays were performed in conditional knockout, small hairpin RNA-mediated knockdown, and AD-related mice models to evaluate the relevance of CDK5 to synaptic homeostasis and functions.

Results: Among candidates with known implications in synaptic modulations, BAG3 ranked the highest. CDK5-mediated phosphorylation on S297/S291 (mouse/human) destabilized BAG3. Loss of BAG3 unleashed the selective protein degradative function of the HSP70 machinery. In neurons, this resulted in enhanced degradation of a number of glutamatergic synaptic proteins. Conditional neuronal knockout of Bag3 in vivo led to impairment of learning and memory functions. In human AD and related mouse models, aberrant CDK5-mediated loss of BAG3 yielded similar effects on synaptic homeostasis. Detrimental effects of BAG3 loss on learning and memory functions were confirmed in these mice, and such effects were reversed by ectopic BAG3 reexpression.

Conclusions: Our results highlight that the neuronal CDK5-BAG3-HSP70 signaling axis plays a critical role in modulating synaptic homeostasis. Dysregulation of the signaling pathway directly contributes to synaptic dysfunction and AD pathogenesis.
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http://dx.doi.org/10.1016/j.biopsych.2019.11.013DOI Listing
April 2020

ABCA7 haplodeficiency disturbs microglial immune responses in the mouse brain.

Proc Natl Acad Sci U S A 2019 11 5;116(47):23790-23796. Epub 2019 Nov 5.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224;

Carrying premature termination codons in 1 allele of the gene is associated with an increased risk for Alzheimer's disease (AD). While the primary function of ABCA7 is to regulate the transport of phospholipids and cholesterol, ABCA7 is also involved in maintaining homeostasis of the immune system. Since inflammatory pathways causatively or consequently participate in AD pathogenesis, we studied the effects of haplodeficiency in mice on brain immune responses under acute and chronic conditions. When acute inflammation was induced through peripheral lipopolysaccharide injection in control or heterozygous knockout mice, partial ABCA7 deficiency diminished proinflammatory responses by impairing CD14 expression in the brain. On breeding to knockin mice, we observed increased amyloid-β (Aβ) accumulation and abnormal endosomal morphology in microglia. Taken together, our results demonstrate that ABCA7 loss of function may contribute to AD pathogenesis by altering proper microglial responses to acute inflammatory challenges and during the development of amyloid pathology, providing insight into disease mechanisms and possible treatment strategies.
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http://dx.doi.org/10.1073/pnas.1908529116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6876254PMC
November 2019

ApoE (Apolipoprotein E) in Brain Pericytes Regulates Endothelial Function in an Isoform-Dependent Manner by Modulating Basement Membrane Components.

Arterioscler Thromb Vasc Biol 2020 01 31;40(1):128-144. Epub 2019 Oct 31.

From the Department of Neuroscience (Y.Y., M.S., A.Y., T.K.), Mayo Clinic, Jacksonville, FL.

Objective: The ε4 allele of the gene () is the strongest genetic risk factor for Alzheimer disease when compared with the common ε3 allele. Although there has been significant progress in understanding how apoE4 (apolipoprotein E4) drives amyloid pathology, its effects on amyloid-independent pathways, in particular cerebrovascular integrity and function, are less clear. Approach and Results: Here, we show that brain pericytes, the mural cells of the capillary walls, differentially modulate endothelial cell phenotype in an apoE isoform-dependent manner. Extracellular matrix protein induction, tube-like structure formation, and barrier formation were lower with endothelial cells cocultured with pericytes isolated from apoE4-targeted replacement (TR) mice compared with those from apoE3-TR mice. Importantly, aged apoE4-targeted replacement mice had decreased extracellular matrix protein expression and increased plasma protein leakages compared with apoE3-TR mice.

Conclusions: ApoE4 impairs pericyte-mediated basement membrane formation, potentially contributing to the cerebrovascular effects of apoE4.
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http://dx.doi.org/10.1161/ATVBAHA.119.313169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007705PMC
January 2020

Miro1 Marks Parkinson's Disease Subset and Miro1 Reducer Rescues Neuron Loss in Parkinson's Models.

Cell Metab 2019 12 26;30(6):1131-1140.e7. Epub 2019 Sep 26.

Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address:

The identification of molecular targets and pharmacodynamic markers for Parkinson's disease (PD) will empower more effective clinical management and experimental therapies. Miro1 is localized on the mitochondrial surface and mediates mitochondrial motility. Miro1 is removed from depolarized mitochondria to facilitate their clearance via mitophagy. Here, we explore the clinical utility of Miro1 for detecting PD and for gauging potential treatments. We measure the Miro1 response to mitochondrial depolarization using biochemical assays in skin fibroblasts from a broad spectrum of PD patients and discover that more than 94% of the patients' fibroblast cell lines fail to remove Miro1 following depolarization. We identify a small molecule that can repair this defect of Miro1 in PD fibroblasts. Treating patient-derived neurons and fly models with this compound rescues the locomotor deficits and dopaminergic neurodegeneration. Our results indicate that tracking this Miro1 marker and engaging in Miro1-based therapies could open new avenues to personalized medicine.
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http://dx.doi.org/10.1016/j.cmet.2019.08.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6893131PMC
December 2019

Differential Effects of Extracellular Vesicles of Lineage-Specific Human Pluripotent Stem Cells on the Cellular Behaviors of Isogenic Cortical Spheroids.

Cells 2019 08 28;8(9). Epub 2019 Aug 28.

Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, FL 32310, USA.

Extracellular vesicles (EVs) contribute to a variety of signaling processes and the overall physiological and pathological states of stem cells and tissues. Human induced pluripotent stem cells (hiPSCs) have unique characteristics that can mimic embryonic tissue development. There is growing interest in the use of EVs derived from hiPSCs as therapeutics, biomarkers, and drug delivery vehicles. However, little is known about the characteristics of EVs secreted by hiPSCs and paracrine signaling during tissue morphogenesis and lineage specification. Methods: In this study, the physical and biological properties of EVs isolated from hiPSC-derived neural progenitors (ectoderm), hiPSC-derived cardiac cells (mesoderm), and the undifferentiated hiPSCs (healthy iPSK3 and Alzheimer's-associated SY-UBH lines) were analyzed. Results: Nanoparticle tracking analysis and electron microscopy results indicate that hiPSC-derived EVs have an average size of 100-250 nm. Immunoblot analyses confirmed the enrichment of exosomal markers Alix, CD63, TSG101, and Hsc70 in the purified EV preparations. MicroRNAs including miR-133, miR-155, miR-221, and miR-34a were differently expressed in the EVs isolated from distinct hiPSC lineages. Treatment of cortical spheroids with hiPSC-EVs in vitro resulted in enhanced cell proliferation (indicated by BrdU+ cells) and axonal growth (indicated by β-tubulin III staining). Furthermore, hiPSC-derived EVs exhibited neural protective abilities in Aβ42 oligomer-treated cultures, enhancing cell viability and reducing oxidative stress. Our results demonstrate that the paracrine signaling provided by tissue context-dependent EVs derived from hiPSCs elicit distinct responses to impact the physiological state of cortical spheroids. Overall, this study advances our understanding of cell‒cell communication in the stem cell microenvironment and provides possible therapeutic options for treating neural degeneration.
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http://dx.doi.org/10.3390/cells8090993DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770916PMC
August 2019
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