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

Abstract

Background

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.

Methods

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.

Results

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.

Conclusion

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.