(T1102) Three-dimensional organoid model derived from stem cells to study and develop treatments for neuromuscular disorders, focusing on spinal cord and muscle integration.
Abstract: Spinal Muscular Atrophy (SMA) is a severe neurodegenerative disorder caused by autosomal recessive mutations in the SMN1 gene, leading to reduced SMN protein levels. This deficiency results in progressive motor neuron loss, denervation, muscle atrophy, and profound weakness. The most severe form, SMA type I, typically leads to early mortality or requires mechanical ventilation within the first two years of life if untreated. Developing human-derived models is essential for advancing our understanding of SMA and identifying effective therapeutic interventions. In this study, we generated human spinal cord organoids from induced pluripotent stem cells (iPSCs) obtained from three SMA type I patients and three healthy controls. These organoids were used to explore disease-related molecular mechanisms in a 3D model and to test a Risdiplam-like compound (RIS-L), designed to enhance SMN protein expression. We implemented an acute and repeated treatment regimen over a 75–90-day differentiation period, reflecting early human fetal development. Our analyses revealed widespread cellular and molecular defects in SMA organoids, affecting multiple cell types beyond motor neurons. These findings were supported by bulk transcriptomics, single-cell RNA sequencing, immunophenotyping, and multi-electrode array (MEA) electrophysiology. Notably, RIS-L treatment modulated over 15% of disease-altered genes, restored the full-length SMN2/Δ7 ratio, and reversed hallmark pathological features, underscoring its therapeutic potential. Additionally, molecular profiling revealed altered cilia-associated gene expression, suggesting a broader impact of RIS-L on neurodevelopmental pathways. Using high-density MEAs, we assessed baseline and chemically modulated electrophysiological activity, revealing disease-specific spiking and bursting abnormalities, alongside treatment-driven functional improvements. Our study emphasizes the early developmental origins of SMA and demonstrates the relevance of organoid-based models for evaluating novel treatments and refining therapeutic strategies.
