Publication
Astrocytes play a crucial role in the onset and progression of amyotrophic lateral sclerosis (ALS), a fatal disorder marked by the degeneration of motor neurons (MNs) in the central nervous system. Although astrocytes in ALS are known to be toxic to MNs, the pathological changes leading to their neurotoxic phenotype remain poorly understood. In this study, we generated human astrocytes from induced pluripotent stem cells (iPSCs) carrying the ALS-associated A4V mutation in superoxide dismutase 1 (SOD1) to examine early cellular pathways and network changes. Proteomic analysis revealed that ALS astrocytes are both dysfunctional and reactive compared to control astrocytes. We identified significant alterations in the levels of proteins linked to ALS pathology and the innate immune cGAS-STING pathway. Furthermore, we found that ALS astrocyte reactivity differs from that of control astrocytes treated with tumor necrosis factor alpha (TNFα), a key cytokine in inflammatory reactions. We then evaluated the potential of fibroblast growth factor (FGF) 2, 4, 16, and 18 to reverse ALS astrocyte phenotype. Among these, FGF4 successfully reversed ALS astrocyte dysfunction and reactivity in vitro. When delivered to the spinal cord of the SOD1 G93A mouse model of ALS, FGF4 lowered astrocyte reactivity. However, this was not sufficient to protect MNs from cell death. Further analysis indicated that TNFα abrogated the reactivity reduction achieved by FGF4, suggesting that complete rescue of the ALS phenotype by FGF4 is hindered by ongoing complex neuroinflammatory processes in vivo. In summary, our data demonstrate that Abbreviations: α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, (AMPA); Adeno-associated virus, (AAV); Amyotrophic lateral sclerosis, (ALS); Cyclic GMP-AMP synthase-Stimulator of interferon genes, (cGAS-STING); Extracellular matrix, (ECM); Familial ALS, (fALS); Fibroblast growth factor, (FGF); Glial fibrillary acidic protein, (GFAP); Glutamate transporter-1, (GLT1); Glutamine synthetase, (GS); Green fluorescent protein, (GFP); Induced pluripotent stem cells, (iPSCs); Inhibitor of DNA binding 3, (ID3); Mitochondrial DNA, (mtDNA); Mitochondrial permeability transition pore, (mPTP); Motor neuron, (MN); Reactive oxygen species, (ROS); Spinal cord, (SC); Sporadic ALS, (sALS); Superoxide dismutase 1, (SOD1); S100 calcium binding protein beta, (S100b),; Tricarboxylic acid cycle/Electron transport chain, (TCA/ETC); Tumor necrosis factor-alpha, (TNFα); Voltage-dependent anion-selective channel 1, (VDAC1); Wildtype, (WT).