Amyotrophic lateral sclerosis patient iPSC-derived astrocytes impair autophagy via non-cell autonomous mechanisms

Abstract

Amyotrophic lateral sclerosis, a devastating neurodegenerative disease, is characterized by the progressive loss of motor neurons and the accumulation of misfolded protein aggregates. The latter suggests impaired proteostasis may be a key factor in disease pathogenesis, though the underlying mechanisms leading to the accumulation of aggregates is unclear. Further, recent studies have indicated that motor neuron cell death may be mediated by astrocytes. Herein we demonstrate that ALS patient iPSC-derived astrocytes modulate the autophagy pathway in a non-cell autonomous manner. We demonstrate cells treated with patient derived astrocyte conditioned medium demonstrate decreased expression of LC3-II, a key adapter protein required for the selective degradation of p62 and ubiquitinated proteins targeted for degradation. We observed an increased accumulation of p62 in cells treated with patient conditioned medium, with a concomitant increase in the expression of SOD1, a protein associated with the development of ALS. Activation of autophagic mechanisms with Rapamycin reduces the accumulation of p62 puncta in cells treated with patient conditioned medium. These data suggest that patient astrocytes may modulate motor neuron cell death by impairing autophagic mechanisms, and the autophagy pathway may be a useful target in the development of novel therapeutics.

Connexin 43 hemichannels mediate spatial and temporal disease spread in ALS

“…Using a fully humanized, spinal cord specific, co-culture platform to study ALS astrocyte/MN interactions, we were able to recapitulate previous studies 24,27,[63][64][65][66][67] showing that ALS hiPSC-A were toxic to hiPSC-MN in co-culture with several FALS and SALS lines. To identify specifically whether toxicity was mediated by the extracellular release of relevant toxic factors, we used a transwell system separating ALS hiPSC-A from hiPSC-M.…”

Astrocyte alterations in neurodegenerative pathologies and their modeling in human induced pluripotent stem cell platforms

“…It has been demonstrated that astrocytes also potentially regulate neuronal proteostasis by affecting autophagic degradation pathways. The ability of conditioned medium from ALS-patient iPSC-derived astrocytes to modulate the autophagy pathway neuronal cells has been linked to the decreased expression of LC3-II and concomitant increase in the expression of SOD1 [ 132 ].…”

Mutant C9orf72 human iPSC‐derived astrocytes cause non‐cell autonomous motor neuron pathophysiology

“…Astrocyte pathology is prominent, with an emerging consensus, particularly from SOD1 based studies, that astrocytes appear critical to disease progression (Papadeas, Kraig, O'Banion, Lepore, & Maragakis, 2011;Wang, Gutmann, & Roos, 2011;Yamanaka et al, 2008). It has also been shown that astrocytes derived from sporadic or familial cases can, upon co-culture or upon exposure to astrocyte conditioned media (ACM), be directly toxic to MNs leading to cell death (Cassina et al, 2008;Di Giorgio, Carrasco, Siao, Maniatis, & Eggan, 2007;Fritz et al, 2013;Haidet-Phillips et al, 2011;Kia, McAvoy, Krishnamurthy, Trotti, & Pasinelli, 2018;Madill et al, 2017;Marchetto et al, 2008;Nagai et al, 2007;Phatnani et al, 2013;Re et al, 2014;Rojas, Cortes, Abarzua, Dyrda, & van Zundert, 2014). In contrast, the influence of astrocytes on MN function is unclear and comparatively understudied.…”