Non-Coding RNA Remodeling in Altered Gravity and Spaceflight: Exposure Attribution, Causal Depth, and Translational Readiness

Spaceflight constitutes a complex physical and environmental exposome in which altered gravitational loading intersects with ionizing radiation and mission-associated stressors that reshape mitochondrial, redox, inflammatory, chromatin, and RNA-processing pathways. Non-coding RNAs (ncRNAs) may participate in these responses, but the evidential meaning of an RNA change depends on exposure, comparator, biological compartment, and experimental model. This review evaluates real spaceflight, onboard gravity controls, simulated microgravity, mechanical unloading, radiation, combined exposures, and recovery as distinct evidence streams. It separates direct RNA measurement and regulatory inference from candidate-specific perturbation, target engagement, and phenotypic rescue. Human and real-spaceflight studies provide the greatest exposure relevance but remain predominantly association-based. Functional evidence is concentrated in selected preclinical muscle, bone, cardiac, and vascular models; mammalian immune evidence remains largely expression- or network-based. Causal depth varies markedly across ncRNA classes and experimental systems. Progress requires exposure-resolved controls, longitudinal and cell- or carrier-resolved sampling, independent replication, and perturbation linked to defined phenotypes. We argue that ncRNAs are currently most informative as mechanistic probes and candidate monitoring readouts. Advancing them toward operational monitoring or countermeasures will require separate validation of analytical performance, biological source, delivery, safety, and efficacy.