BACKGROUND: Radiation therapy remains a cornerstone in the treatment of primary and metastatic tumors; however, its efficacy is limited by the spinal cord's high sensitivity to radiation-induced injury. To better understand the mechanisms underlying spinal cord radiosensitivity, we developed a three-dimensional human spinal cord organoid model derived from human-induced pluripotent stem cells using a neuroectodermal differentiation protocol that closely mimics embryonic spinal cord development. METHODS: Mature spinal cord organoids were exposed to a clinically relevant 2 Gy dose of ionizing radiation, and subsequent assessments included evaluation of DNA damage, astrocytic response, and neuronal functionality. RESULTS: The organoids successfully recapitulated key features of spinal cord development, including neural differentiation, spontaneous electrophysiological activity, and functional maturation. Radiation exposure led to pronounced DNA double-strand breaks, particularly in SOX2-expressing progenitor cells. Astrocyte hyperplasia was evident through increased GFAP expression, indicating a reactive gliosis response. Electrophysiological analysis revealed a marked reduction in spike frequency and burst activity, indicative of impaired neuronal function. Although partial recovery was observed over time, functional deficits persisted, suggesting sustained damage. CONCLUSION: This human spinal cord organoid model offers a physiologically relevant platform for studying radiation-induced spinal cord injury and provides valuable insights into the cellular and functional consequences of radiation exposure. It holds significant potential for advancing neuroprotective strategies and therapeutic interventions targeting radiation-induced damage in the central nervous system.

Understanding how chemical stress perturbs human lung physiology requires models that capture dynamic molecular responses in real time. Here, we established a CRISPR/Cas9-engineered human induced pluripotent stem cell (hiPSC)-derived lung organoid expressing endogenous G3BP1–mCherry, enabling live, non-destructive visualization of stress granule (SG) formation under toxicant exposure. The organoids recapitulated airway and alveolar epithelial diversity and displayed lamellar body-like ultrastructures, indicating advanced maturation. Time-lapse imaging revealed rapid and reversible SG dynamics across chemically distinct stressors, while cytotoxicity assays showed that these organoids are significantly more sensitive than conventional 2D or cancer-derived lung models. Importantly, SG dynamics were linked to exposure duration–dependent changes in epithelial barrier integrity, indicating that SG formation precedes overt epithelial injury and serves as an early indicator of toxicant-induced cellular stress. Integration with high-content screening enabled quantitative, image-based analysis of cellular stress phenotypes, greatly enhancing throughput and mechanistic insight, thereby provided next-generation New Approach Methodologies for lung toxicity assessment. Together, this hiPSC-derived lung organoid SG reporter platform links early molecular stress adaptation to tissue-level responses, offering a predictive and mechanistically informative framework for human-relevant lung toxicity evaluation.

Evolution has used cell-cell communication as a strategy to coordinate organ development, enabling the reproducible generation of intricate structures. Classically, these interactions have been studied one at a time in model organisms, limiting our understanding of how cellular interplay coordinates human development. We investigated human kidney development using single-cell RNA sequencing and spatial transcriptomics, analyzing over 700,000 cells. By mapping gene expression and differentiation trajectories in space, we define the spatial organization of kidney development. Our analysis revealed unrecognized plasticity, showing that cell fate established during early patterning can be later revised. This plasticity provides a potential mechanism for how cell fate is robustly established in complex patterned tissues. Additionally, through a genome-wide, spatially aware cell-cell interaction analysis, we link localized ligand signals to cell fate decisions. We also define biologically meaningful cellular neighborhoods based on aggregated extracellular cues, providing a blueprint to understand the coordination of human development at scale.