Meta-analysis of human and mouse ALS astrocytes reveals multi-omic signatures of inflammatory reactive states

Abstract

Astrocytes contribute to motor neuron death in amyotrophic lateral sclerosis (ALS), but whether they adopt deleterious features consistent with inflammatory reactive states remains incompletely resolved. To identify inflammatory reactive features in ALS human induced pluripotent stem cell (hiPSC)–derived astrocytes, we examined transcriptomics, proteomics, and glutamate uptake in VCP-mutant astrocytes. We complemented this by examining other ALS mutations and models using a systematic meta-analysis of all publicly-available ALS astrocyte sequencing data, which included hiPSC-derived astrocytes carrying SOD1, C9orf72, and FUS gene mutations as well as mouse ALS astrocyte models with SOD1G93A mutation, Tardbp deletion, and Tmem259 (also known as membralin) deletion. ALS astrocytes were characterized by up-regulation of genes involved in the extracellular matrix, endoplasmic reticulum stress, and the immune response and down-regulation of synaptic integrity, glutamate uptake, and other neuronal support processes. We identify activation of the TGFB, Wnt, and hypoxia signaling pathways in both hiPSC and mouse ALS astrocytes. ALS changes positively correlate with TNF, IL1A, and complement pathway component C1q-treated inflammatory reactive astrocytes, with significant overlap of differentially expressed genes. By contrasting ALS changes with models of protective reactive astrocytes, including middle cerebral artery occlusion and spinal cord injury, we uncover a cluster of genes changing in opposing directions, which may represent down-regulated homeostatic genes and up-regulated deleterious genes in ALS astrocytes. These observations indicate that ALS astrocytes augment inflammatory processes while concomitantly suppressing neuronal supporting mechanisms, thus resembling inflammatory reactive states and offering potential therapeutic targets.

Astrocytic Glutamatergic Transmission and Its Implications in Neurodegenerative Disorders

“…This could serve as a protective mechanism at first but becomes toxic over time due to impaired homeostasis. These ALS astrocytes up-regulate inflammatory signaling and are seen to reduce its supportive actions to neurons [ 90 ].…”

Proteomic Alterations and Novel Markers of Neurotoxic Reactive Astrocytes in Human Induced Pluripotent Stem Cell Models

“…Over the past years, multiple studies from independent laboratories have demonstrated that hiPSC modeling is a powerful tool for uncovering the role of astrocytes in CNS diseases, including AD ( Oksanen et al, 2017 ; Preman et al, 2021 ; de Leeuw et al, 2022 ), Parkinson’s disease ( di Domenico et al, 2019 ; de Rus Jacquet et al, 2021 ; Ramos-Gonzalez et al, 2021 ; Russ et al, 2021 ; Trudler et al, 2021 ) and amyotrophic lateral sclerosis ( Birger et al, 2019 ; Zhao et al, 2020 ; Szebényi et al, 2021 ; Ziff et al, 2021 ; Giacomelli et al, 2022 ). Developing human models is particularly critical since such diseases cannot be fully recapitulated in animal systems and thus require multiple integrated approaches (i.e., combination of human and animal studies) to understand their pathogenic mechanisms.…”

Neurotoxic Astrocytes Directly Converted from Sporadic and Familial ALS Patient Fibroblasts Reveal Signature Diversities and miR-146a Theragnostic Potential in Specific Subtypes

“…Because only a low number of samples were evaluated, this type of correlations should be further explored in studies analyzing a higher number of patients. However, most of the studies with patient cells also involved few cell lines and had a scientific impact [ 19 , 29 , 61 , 62 , 63 ]. The phenotypic variability observed in the present study between ALS iAstrocyte lines suggests that it may be useful in the stratification and subcategorization of patients.…”

“…Astrocytes were shown to release toxic factors and to have a key role in MN degeneration in both fALS and sALS patients [ 6 , 7 , 99 , 100 ]. Astrocyte-aberrant reactive features involving a decrease in GFAP and GLT-1 levels, an increased proliferative capacity, and an elevated expression of the Cx43 and S100B signature [ 20 , 21 ], together with inflammatory astrocytic markers [ 36 , 61 ], were identified in rodent and human ALS models. However, whether these markers are differently presented by fALS and sALS iAstrocytes was never investigated.…”

“…Since only a small number of patients were studied, further works should consider a larger sample, though the low yield of the direct conversion technology and its complex steps still bring important limitations [ 19 , 29 , 61 , 62 , 63 ]. Despite this, our present study, highlights the use of directly converted iAstrocytes from ALS patients as an important tool for precision medicine.…”