Background: Induced pluripotent stem cell (iPSC) based neuronal differentiation is valuable for studying neuropsychiatric disorders and pharmacological mechanisms at the cellular level. We aimed to examine the effects of typical and atypical antipsychotics on human iPSC-derived neural progenitor cells (NPCs). Methods: Proliferation and neurite outgrowth were measured by live cell imaging, and gene expression levels related to neuronal identity were analyzed by RT-QPCR and immunocytochemistry during differentiation into hippocampal dentate gyrus granule cells following treatment of low- and high-dose antipsychotics (haloperidol, olanzapine, and risperidone). Results: Antipsychotics did not modify the growth properties of NPCs after 3 days of treatment. However, the characteristics of neurite outgrowth changed significantly in response to haloperidol and olanzapine. After three weeks of differentiation, mRNA expression levels of the selected neuronal markers increased (except for MAP2), while antipsychotics caused only subtle changes. Additionally, we found no changes in MAP2 or GFAP protein expression levels as a result of antipsychotic treatment. Conclusions: Altogether, antipsychotic medications promoted neurogenesis in vitro by influencing neurite outgrowth rather than changing cell survival or gene expression. This study provides insights into the effects of antipsychotics on neuronal differentiation and highlights the importance of considering neurite outgrowth as a potential target of action.

Schizophrenia is a complex psychiatric disorder of complex etiology. Despite decades of antipsychotic drug development and treatment, the mechanisms underlying cellular drug effects remain incompletely understood. Induced pluripotent stem cell (iPSC)-based disease and pharmacological modelling offer new avenues for drug development. In this study, we explored the development of two- and three-dimensional neural progenitor cultures and the impact of different antipsychotics in a schizophrenia model. Four human iPSC lines, including two carrying a de novo ZMYND11 gene mutation associated with schizophrenia, were differentiated into hippocampal neural progenitor cells (NPCs), cultured either in monolayers or as 3D spheroids. While in monolayers the proliferation of the NPCs was similar, spheroids showed significant differences in scattered cell number and outgrowth size between schizophrenia mutant and wild-type NPCs. Since there is only limited information about the effects of antipsychotic agents on neural progenitor cell proliferation and differentiation, we investigated the effects of three molecules, representing three subgroups of antipsychotics, in the 2D and 3D NPC models. Our findings suggest that cell adhesion may play a crucial role in the molecular disease pathways of schizophrenia, highlighting the value of spheroid models for mechanistic and drug development studies. These studies may significantly help our understanding of the effects of schizophrenia on neural development and the response of progenitors to antipsychotic medications.