Small neuron-derived extracellular vesicles from individuals with down syndrome propagate tau pathology in the wildtype mouse brain

Altres ajuts: National Institutes of Health (R01AG070153/R21AG056974, RF1AG061566); Bright Focus foundation (CA2018010).Individuals with Down syndrome (DS) exhibit Alzheimer's disease (AD) pathology at a young age, including amyloid plaques and neurofibrillary tangles (NFTs). Tau pathology can spread via extracellular vesicles, such as exosomes. The cargo of neuron-derived small extracellular vesicles (NDEVs) from individuals with DS contains p-Tau at an early age. The goal of the study was to investigate whether NDEVs isolated from the blood of individuals with DS can spread Tau pathology in the brain of wildtype mice. We purified NDEVs from the plasma of patients with DS-AD and controls and injected small quantities using stereotaxic surgery into the dorsal hippocam-pus of adult wildtype mice. Seeding competent Tau conformers were amplified in vitro from DS-AD NDEVs but not NDEVs from controls. One month or 4 months post-injection, we examined Tau pathology in mouse brains. We found abundant p-Tau immunostaining in the hippocampus of the mice injected with DS-AD NDEVs compared to injections of age-matched control NDEVs. Double labeling with neuronal and glial markers showed that p-Tau staining was largely found in neurons and, to a lesser extent, in glial cells and that p-Tau immunostaining was spreading along the corpus callosum and the medio-lateral axis of the hippocampus. These studies demonstrate that NDEVs from DS-AD patients exhibit Tau seeding capacity and give rise to tangle-like intracellular inclusions

Is it possible to improve neurodevelopmental abnormalities in Down syndrome?

Down syndrome (DS) is a genetic pathology caused by the triplication of human chromosome 21. Although individuals with DS have various medical problems, intellectual disability is the most invalidating aspect of the pathology. Despite numerous efforts, the mechanisms whereby gene triplication leads to the DS phenotype have not been elucidated and there are, at present, no therapies to rescue brain developmental alterations and mental disability in individuals with DS. In this review, we focused on the major defects of the DS brain, comparing data regarding humans with DS and mouse models for DS, and therapeutic interventions attempted on animal DS models. Based on the promising results of pharmacotherapies in these models, we believe that it is possible to conclude that tools to improve brain development in DS are now almost at hand. We now know that it is possible to rescue and/or improve neurogenesis, neuron maturation, connectivity, neurodegeneration and behavior. We believe that the knowledge gained in DS mouse models provides a rational basis to start new clinical trials in infants, children and adults with DS, exploiting drugs that have proved able to rescue various facets of the DS neurologic phenotype. It is not unreasonable to consider that the results of these trials may provide a positive answer to the question: 'Is it possible to improve brain development in DS?'