Cerebral spinal fluid (CSF) is a promising biospecimen for the detection of central nervous system
biomarkers to monitor therapeutic efficacy at the cellular level in neurological diseases.
Spinal muscular atrophy (SMA) patients receiving intrathecal
antisense oligonucleotide (
nusinersen)
therapy tend to show improved motor function, but the treatment effect on cellular health remains unknown. The objective of this study was to assess the potential of extracellular RNAs and
microRNAs in SMA patient CSF as indicators of neuron and glial health following
nusinersen treatment. Extracellular
RNA analysis of CSF samples revealed ongoing cellular stress related to
inflammation and glial differentiation, even
after treatment administration. Downregulated
microRNA expression associated with SMA-specific or general motor neuron dysfunction in animal and cellular models, tended to increase in
nusinersen-treated patient CSF samples and correlated with SMA Type 1 and 2 motor functioning improvements. However, miR-146a, known to be upregulated in SMA-induced pluripotent stem cell (iPSC)-derived astrocytes, showed increased expression in
nusinersen-treated CSF samples. We then used
mRNA sequencing and multi-
electrode arrays to assess the transcriptional and functional effects of miR-146a on healthy and SMA iPSC-derived motor neurons. miR-146a treatment on iPSC-derived motor neurons led to a downregulation of extracellular matrix genes associated with synaptic perineuronal net and alterations in spontaneous electrophysiological activity. Altogether, this study suggests that extracellular RNAs and
microRNAs may serve as useful
biomarkers to monitor cellular health during
nusinersen treatment. Moreover, these data highlight the importance of addressing astrocyte health and response to
nusinersen in SMA pathogenesis and treatment strategies.