Dual SMAD inhibition as a versatile platform in human pluripotent stem cell-based regenerative medicine and disease modeling.

Dual SMAD inhibition is a robust and widely adopted protocol for directing human pluripotent stem cells (hPSCs) toward neuronal lineages by blocking transforming growth factor-beta and bone morphogenetic protein pathways. Suppressing transforming growth factor-beta and bone morphogenetic protein signaling enables efficient and reproducible induction of neuroectoderm, serving as the foundation for generating diverse brain region-specific neuronal subtypes. This review outlines the mechanistic basis and major achievements of the dual SMAD inhibition strategy, including its application in 2 recent clinical trials for Parkinson's disease, and its role in preclinical studies targeting conditions, such as spinal cord injury (SCI), retinal degeneration, and amyotrophic lateral sclerosis (ALS). In addition to its significant contribution to the generation of transplantation-ready grafts from hPSCs, the protocol serves as a valuable platform for disease modeling across various neurological and metabolic disorders. The key strengths include high efficiency, technical simplicity that enables precise control of cell fate using small molecules, versatility in both 2- and 3-dimensional culture systems, and reproducibility across various hPSC lines. This review also addresses key limitations, such as restricted gliogenic capacity and limited neural progenitor cell expansion. Future research should focus on incorporating emerging technologies to advance stem cell-based applications. Overall, dual SMAD inhibition represents a powerful and versatile platform for stem cell-based neuroscience and regenerative medicine.