Human Spinal Motor Neurons Are Particularly Vulnerable to Cerebrospinal Fluid of Amyotrophic Lateral Sclerosis Patients

Abstract

Amyotrophic lateral sclerosis (ALS) is the most common and devastating motor neuron (MN) disease. Its pathophysiological cascade is still enigmatic. More than 90% of ALS patients suffer from sporadic ALS, which makes it specifically demanding to generate appropriate model systems. One interesting aspect considering the seeding, spreading and further disease development of ALS is the cerebrospinal fluid (CSF). We therefore asked whether CSF from sporadic ALS patients is capable of causing disease typical changes in human patient-derived spinal MN cultures and thus could represent a novel model system for sporadic ALS. By using induced pluripotent stem cell (iPSC)-derived MNs from healthy controls and monogenetic forms of ALS we could demonstrate a harmful effect of ALS-CSF on healthy donor-derived human MNs. Golgi fragmentation—a typical finding in lower organism models and human postmortem tissue—was induced solely by addition of ALS-CSF, but not control-CSF. No other neurodegenerative hallmarks—including pathological protein aggregation—were found, underpinning Golgi fragmentation as early event in the neurodegenerative cascade. Of note, these changes occurred predominantly in MNs, the cell type primarily affected in ALS. We thus present a novel way to model early features of sporadic ALS.

Cerebrospinal fluid cytotoxicity in amyotrophic lateral sclerosis: a systematic review of in vitro studies

“…The variety of cell lines employed, some of which could differ considerably from human motor neurons in their response to CSF exposure, is also a major limitation of our study. Notwithstanding this, one recent study that post-dates our literature search, in which human iPSC-derived spinal motor neurons were exposed to ALS–CSF, supports the cytotoxicity of ALS–CSF towards motor neurons ( Brauer et al , 2020 ).…”

40 Years of CSF Toxicity Studies in ALS: What Have We Learnt About ALS Pathophysiology?

“…Despite being repeatedly linked to ALS-CSF exposure, the cause of neurofilament phosphorylation, as well as its contribution to CSF-mediated neurodegeneration, is still poorly understood (Vijayalakshmi et al, 2009). Ultrastructural changes following exposure to ALS-CSF also include Golgi fragmentation and endoplasmic reticulum stress, the latter being supported by free polyribosomes and fragmented ER cisternae being observed microscopically (Ramamohan et al, 2007;Vijayalakshmi et al, 2011;Brauer et al, 2020). Mitochondrial and lysosomal dysregulation have also been described, hinting at possible oxidative stress (Sharma et al, 2016).…”

“…Notable was the finding that CSF from patients with both sporadic and familial forms of ALS caused cytotoxicity when incubated with neurons in culture. Although these results were predominantly based on rat neuron cultures, as well as the NSC-34 cell line (a mouse spinal cord-neuroblastoma hybrid cell line), recent evidence involving motor neurons derived from human induced pluripotent stem cells (iPSCs) and human embryonic stem cells (hESCs), indicates that CSF-mediated toxicity may also be common to human neurons ( Sumitha et al, 2019 ; Brauer et al, 2020 ). Complementing in vitro evidence, several in vivo studies have also been performed, demonstrating a range of pathological changes upon CSF injection.…”

“…A more recent study employing human iPSC-derived motor neurons, however, failed to observe such changes following ALS-CSF exposure ( Brauer et al, 2020 ). Additionally, although CSF exposure produced significant neuronal loss, this effect did not appear to be specific to cells treated with ALS-CSF.…”

Defining novel functions for cerebrospinal fluid in ALS pathophysiology

“…Although CSF from ALS patients is now known to be constitutionally abnormal [ 18 , 27 ], with raised levels of proteins, including TDP-43 and neurofilaments [ 115 , 210 ], its toxicity started being recognised early on, when it was shown to significantly reduce the survival of rat primary neuronal cultures [ 45 ]. Since then, numerous studies have been performed on various cell types, including NSC-34 cell lines, and, more recently, hESC-derived and iPSC-derived motor neurons, showing greater degeneration when the cells were exposed to CSF from ALS patients than to CSF from control patients [ 33 , 136 , 189 , 197 ]. Interestingly, ALS-CSF was also shown in NSC-34 cells to result in TDP-43 mislocalisation to the cytoplasm, a feature that could be reversed by VEGF [ 174 ].…”