AN SGZ-SVZ NEURAL SPHEROID FUSION MODEL TO STUDY NICHE-NICHE INTERACTIONS

In the mammalian brain, neural stem cells (NSCs) reside in specialized microenvironments in the subgranular zone (SGZ) and subventricular zone (SVZ). These niche components communicate both within and across regions to influence neurogenic output and repair responses in normal and pathological contexts, highlighting the translational relevance of studying niche–niche interactions. Three-dimensional neural spheroid and organoid models differ primarily in their degree of tissue self-organization, with organoids exhibiting complex regional architecture and spheroids providing uniform and reproducible cellular assemblies that are particularly useful for controlled intervention studies, making them well-suited to dissect specific inter‑niche signalling mechanisms. Here, we developed a 3D neural spheroid-based fusion model from primary postnatal SGZ- and SVZ-derived NSCs undergoing multilineage differentiation, resulting in functional neuronal networks and myelination. SGZ and SVZ spheroids were generated independently and allowed to undergo spontaneous fusion. Phenotypic analysis of fused spheroids confirmed the maintenance of niche-dependent lineage marker expression in each domain. Functional connectivity was assessed using calcium imaging in response to glutamate and histamine, revealing activity patterns across spheroids, indicating inter-spheroid network formation. Immunocytochemical analysis demonstrated the presence of oligodendrocytes and the colocalization of myelin sheets with an axonal marker. By enabling controlled interaction between two major neurogenic niches, this platform allows dissection of niche–niche communication mechanisms inaccessible in vivo or oversimplified in single-niche in vitro systems, providing a simple but reproducible tool for therapeutic discovery.
Funding: National Science Centre, Poland 2025/57/N/NZ5/03530; National Science Centre, Poland 2021/43/B/NZ7/01162.