Small‐Pore Chitosan Microcarriers Support Surface‐Adherent Growth of Induced Pluripotent Stem Cell–Derived Neural Stem Cells and Improve Intranasal Therapy of Murine Anosmia

Intranasal delivery of neural stem cells offers a non-invasive strategy for central nervous system repair, yet its efficacy is limited by rapid mucociliary clearance and poor cellular retention. Although chitosan-based carriers have been explored, the architectural principles governing neural stem cell behavior in the intranasal microenvironment remain poorly defined. We compared chitosan microcarriers (CSMs) with three pore architectures (mean surface pore sizes 4.7 ± 1.7, 15.9 ± 3.2, and 20.5 ± 0.7 µm), fabricated via freezing-controlled phase separation, using induced pluripotent stem cell-derived neural stem cells (iPSC-NSCs). Cellular responses did not vary linearly with pore size: the smallest-pore formulation, CSM-196, supported surface-adhesion-dominant growth, whereas both larger-pore formulations supported infiltration-dominant growth. CSM-196 was also associated with increased proliferative activity, spontaneous neuronal differentiation, and elevated neurotrophic factor secretion without exogenous induction factors. In a methimazole-induced anosmia model, the CSM-196-iPSC-NSC formulation produced greater improvements in olfactory behavioral recovery, olfactory epithelial thickness, neuronal marker expression, and epithelial proliferation than cell-only delivery administered by the same route and schedule. This chitosan-based platform provides a surface-adhesion-oriented cell-delivery strategy that warrants further evaluation for intranasal neural regenerative therapy.