Asynchronous co-culture enhances neuronal differentiation in CRISPR/Cas9-engineered NURR1 reporter induced neural stem cells

Parkinson's disease (PD) is caused by the gradual degeneration of dopaminergic neurons in the midbrain, resulting in severe motor impairments. Stem cell-based neurorestorative therapies present considerable therapeutic promise; however, major challenges remain, such as variability in lineage specification, limited long-term graft survival, and the absence of effective real-time techniques to monitor differentiation processes. Overcoming these obstacles necessitates innovative strategies to address cellular heterogeneity and enhance the efficacy of neurorestorative interventions.

We engineered a NURR1-driven dopaminergic reporter in induced neural stem cells (iNSCs) through CRISPR/Cas9-mediated knock-in of ZsGreen. The differentiation capacity of reporter iNSCs was validated via in vitro spontaneous differentiation. Transcriptomic profiling was performed to compare fluorescence-sorted differentiation-committed (ZsGreen⁺) and non-committed (ZsGreen^–) subpopulations with biological triplicates. To enhance neuronal differentiation efficiency, we developed a stage-specific asynchronous co-culture system that combined early-stage (day 5) and mid-stage (day 8) differentiating iNSC populations. Optimized iNSC-derived dopaminergic precursors were transplanted into striatum of sixteen male SCID-Beige mice (6–8 weeks old), which were randomly assigned to two groups: one receiving co-cultured cells (n ​= ​8) and the other receiving non-co-cultured cells (n ​= ​8). Graft survival and differentiation were subsequently assessed.

The reporter system allowed real-time tracking of dopaminergic differentiation from iNSCs without affecting their differentiation potential. Transcriptome analysis showed specific activation of neurorestorative pathways in ZsGreen⁺ ​cells, including processes such as neurogenesis, neuronal maturation, axonal guidance, and cell projection organization. Asynchronous co-culture markedly enhanced the neuronal yield from iNSC-derived dopaminergic precursors compared with standard approaches. Transplantation in vivo confirmed stable engraftment and differentiation into TH-positive cells within the host striatal tissue.

The NURR1-ZsGreen reporter system provides a functional platform to resolve lineage specification heterogeneity and optimize differentiation protocols. The identified neurorestorative pathways, together with the asynchronous co-culture strategy, collectively address critical barriers in cell replacement-based neurorestorative therapy.