Reactive Astrocytes Promote ALS-like Degeneration and Intracellular Protein Aggregation in Human Motor Neurons by Disrupting Autophagy through TGF-β1

Stem Cell Reports. 2017 Aug 8;9(2):667-680. doi: 10.1016/j.stemcr.2017.06.008. Epub 2017 Jul 14.

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal and rapidly progressing motor neuron disease. Astrocytic factors are known to contribute to motor neuron degeneration and death in ALS. However, the role of astrocyte in promoting motor neuron protein aggregation, a disease hallmark of ALS, remains largely unclear. Here, using culture models of human motor neurons and primary astrocytes of different genotypes (wild-type or SOD1 mutant) and reactive states (non-reactive or reactive), we show that reactive astrocytes, regardless of their genotypes, reduce motor neuron health and lead to moderate neuronal loss. After prolonged co-cultures of up to 2 months, motor neurons show increased axonal and cytoplasmic protein inclusions characteristic of ALS. Reactive astrocytes induce protein aggregation in part by releasing transforming growth factor β1 (TGF-β1), which disrupts motor neuron autophagy through the mTOR pathway. These results reveal the important contribution of reactive astrocytes in promoting aspects of ALS pathology independent of genetic influences.

Keywords: ALS; TGF-b; autophagy; human motor neurons; mTOR; reactive astrocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyotrophic Lateral Sclerosis / etiology
  • Amyotrophic Lateral Sclerosis / metabolism
  • Amyotrophic Lateral Sclerosis / pathology
  • Animals
  • Astrocytes / metabolism*
  • Astrocytes / pathology
  • Autophagy*
  • Axons / metabolism
  • Cell Survival / genetics
  • Cells, Cultured
  • Cytoplasm / metabolism
  • Disease Models, Animal
  • Humans
  • Intermediate Filaments / metabolism
  • Mice
  • Motor Neurons / metabolism*
  • Mutation
  • Protein Aggregates / genetics
  • Protein Aggregation, Pathological*
  • Signal Transduction
  • Superoxide Dismutase-1 / genetics
  • Superoxide Dismutase-1 / metabolism
  • TOR Serine-Threonine Kinases / metabolism
  • Transforming Growth Factor beta1 / metabolism*

Substances

  • Protein Aggregates
  • Transforming Growth Factor beta1
  • Superoxide Dismutase-1
  • MTOR protein, human
  • TOR Serine-Threonine Kinases