Stem Cell-Derived Spinal Cord Organoid Model: Temporal and Cell-Specific Analysis of Molecular Effects of a Risdiplam Analogue
Stefania Corti1, Andrea D'Angelo2, Francesca Beatrice2, Chiara Cordiglieri3, Matteo Miotto4, Simona Lodato5, Megi Meneri6, Delia Gagliardi6, Federica Rizzo2, Giacomo Comi2, Linda Ottoboni2
1Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, 2University of Milan, 3INGM, 4Humanitas University, 5Department of Biomedical Sciences, Humanitas University, 6Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico
Objective:
To investigate the molecular and functional effects of a risdiplam-like compound (RIS-L) using a 3D human spinal cord organoid model derived from iPSCs of spinal muscular atrophy (SMA) type 1 patients and healthy controls, aiming to optimize treatment parameters and identify potential complementary targets.
Background:
SMA is a severe neurological disorder caused by SMN1 gene mutations, leading to motor neuron degeneration. Risdiplam, an approved therapy, increases SMN protein levels by modifying splicing. RIS-L, with improved pharmacological properties, mimics risdiplam's action, but its precise molecular effects remain unclear.
Design/Methods:
We generated and characterized spinal cord organoids (SCOs) from iPSCs of SMA type 1 patients and healthy controls. We optimized RIS-L dosage and treatment timing, studied its molecular and functional consequences, and explored potential complementary pharmacological targets. Analyses included bulk gene expression profiling and single-cell transcriptomics.
Results:
SCOs derived from SMA type 1 patients successfully modeled disease characteristics. Repeated treatment with 150 nM RIS-L every 2 days up to day 300 was well-tolerated, providing the best molecular risk/benefit ratio and promoting motor neuron differentiation. Treatment initiation at day 45 of organoid development, compared to day 30, resulted in broader gene modulation and enhanced motor neuron differentiation. Both time points increased full-length SMN isoform levels. Bulk analysis revealed modulation of specific gene sets towards control levels. Single-cell analysis uncovered early differentiation defects associated with basal activity and hyperexcitability in SMA organoids. Notably, our findings indicate that RIS-L treatment should not be initiated too early in spinal cord development for optimal effects.
Conclusions:
Stem cell-derived spinal cord organoids prove to be a valuable tool for studying SMA treatments in a human proxy model. This model offers a robust platform for identifying complementary pharmacological targets within an extended therapeutic window, potentially improving future treatment strategies for SMA.
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