Examinando por Autor "Abarzúa, Sebastián"

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    Excessive release of inorganic polyphosphate by ALS/FTD astrocytes causes non-cell-autonomous toxicity to motoneurons
    (Cell Press, 2022-05-18) Arredondo, Cristian; Cefaliello, Carolina; Dyrda, Agnieszka; Jury, Nur; Martinez, Pablo; Díaz, Iván; Amaro, Armando; Tran, Helene; Morales, Danna; Pertusa, Maria; Stoica, Lorelei; Fritz, Elsa; Corvalán, Daniela; Abarzúa, Sebastián; Méndez-Ruette, Maxs; Fernández, Paola; Rojas, Fabiola; Kumar, Meenakshi Sundaram; Aguilar, Rodrigo; Almeida, Sandra; Weiss, Alexandra; Bustos, Fernando J.; González-Nilo, Fernando; Otero, Carolina; Tevy, Maria Florencia; Bosco, Daryl A.; Sáez, Juan C.; Kähne, Thilo; Gao, Fen-Biao; Berry, James D.; Nicholson, Katharine; Sena-Esteves, Miguel; Madrid, Rodolfo; Varela, Diego; Montecino, Martin; Brown, Robert H.; van Zundert, Brigitte
    Non-cell-autonomous mechanisms contribute to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), in which astrocytes release unidentified factors that are toxic to motoneurons (MNs). We report here that mouse and patient iPSC-derived astrocytes with diverse ALS/FTD-linked mutations (SOD1, TARDBP, and C9ORF72) display elevated levels of intracellular inorganic polyphosphate (polyP), a ubiquitous, negatively charged biopolymer. PolyP levels are also increased in astrocyte-conditioned media (ACM) from ALS/FTD astrocytes. ACM-mediated MN death is prevented by degrading or neutralizing polyP in ALS/FTD astrocytes or ACM. Studies further reveal that postmortem familial and sporadic ALS spinal cord sections display enriched polyP staining signals and that ALS cerebrospinal fluid (CSF) exhibits increased polyP concentrations. Our in vitro results establish excessive astrocyte-derived polyP as a critical factor in non-cell-autonomous MN degeneration and a potential therapeutic target for ALS/FTD. The CSF data indicate that polyP might serve as a new biomarker for ALS/FTD. © 2022 Elsevier Inc.
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    Mature iPSC-derived astrocytes of an ALS/FTD patient carrying the TDP43 A90V mutation display a mild reactive state and release polyP toxic to motoneurons
    (Frontiers Media SA, 2023) Rojas, Fabiola; Aguilar, Rodrigo; Almeida, Sandra; Fritz, Elsa; Corvalán, Daniela; Ampuero, Estibaliz; Abarzúa, Sebastián; Garcés, Polett; Amaro, Armando; Diaz, Iván; Arredondo, Cristian; Cortes, Nicole
    Astrocytes play a critical role in the maintenance of a healthy central nervous system and astrocyte dysfunction has been implicated in various neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). There is compelling evidence that mouse and human ALS and ALS/FTD astrocytes can reduce the number of healthy wild-type motoneurons (MNs) in co-cultures or after treatment with astrocyte conditioned media (ACM), independently of their genotype. A growing number of studies have shown that soluble toxic factor(s) in the ACM cause non-cell autonomous MN death, including our recent identification of inorganic polyphosphate (polyP) that is excessively released from mouse primary astrocytes (SOD1, TARDBP, and C9ORF72) and human induced pluripotent stem cells (iPSC)-derived astrocytes (TARDBP) to kill MNs. However, others have reported that astrocytes carrying mutant TDP43 do not produce detectable MN toxicity. This controversy is likely to arise from the findings that human iPSC-derived astrocytes exhibit a rather immature and/or reactive phenotype in a number of studies. Here, we have succeeded in generating a highly homogenous population of functional quiescent mature astrocytes from control subject iPSCs. Using identical conditions, we also generated mature astrocytes from an ALS/FTD patient carrying the TDP43A90V mutation. These mutant TDP43 patient-derived astrocytes exhibit key pathological hallmarks, including enhanced cytoplasmic TDP-43 and polyP levels. Additionally, mutant TDP43 astrocytes displayed a mild reactive signature and an aberrant function as they were unable to promote synaptogenesis of hippocampal neurons. The polyP-dependent neurotoxic nature of the TDP43A90V mutation was further confirmed as neutralization of polyP in ACM derived from mutant TDP43 astrocytes prevented MN death. Our results establish that human astrocytes carrying the TDP43A90V mutation exhibit a cell-autonomous pathological signature, hence providing an experimental model to decipher the molecular mechanisms underlying the generation of the neurotoxic phenotype. Copyright © 2023 Rojas, Aguilar, Almeida, Fritz, Corvalán, Ampuero, Abarzúa, Garcés, Amaro, Diaz, Arredondo, Cortes, Sanchez, Mercado, Varela-Nallar, Gao, Montecino and van Zundert.
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    Skeletal myotubes expressing ALS mutant SOD1 induce pathogenic changes, impair mitochondrial axonal transport, and trigger motoneuron death
    (BioMed Central Ltd, 2024-12) Martínez, Pablo; Silva, Mónica; Abarzúa, Sebastián; Tevy, María Florencia; Jaimovich, Enrique; Constantine-Paton, Martha; Bustos, Fernando J.; van Zundert, Brigitte
    Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of motoneurons (MNs), and despite progress, there is no effective treatment. A large body of evidence shows that astrocytes expressing ALS-linked mutant proteins cause non-cell autonomous toxicity of MNs. Although MNs innervate muscle fibers and ALS is characterized by the early disruption of the neuromuscular junction (NMJ) and axon degeneration, there are controversies about whether muscle contributes to non-cell-autonomous toxicity to MNs. In this study, we generated primary skeletal myotubes from myoblasts derived from ALS mice expressing human mutant SOD1G93A (termed hereafter mutSOD1). Characterization revealed that mutSOD1 skeletal myotubes display intrinsic phenotypic and functional differences compared to control myotubes generated from non-transgenic (NTg) littermates. Next, we analyzed whether ALS myotubes exert non-cell-autonomous toxicity to MNs. We report that conditioned media from mutSOD1 myotubes (mutSOD1-MCM), but not from control myotubes (NTg-MCM), induced robust death of primary MNs in mixed spinal cord cultures and compartmentalized microfluidic chambers. Our study further revealed that applying mutSOD1-MCM to the MN axonal side in microfluidic devices rapidly reduces mitochondrial axonal transport while increasing Ca2 + transients and reactive oxygen species (i.e., H2O2). These results indicate that soluble factor(s) released by mutSOD1 myotubes cause MN axonopathy that leads to lethal pathogenic changes.