MODELING THE HUMAN OXYTOCIN SYSTEM: FROM HIPSC-DERIVED NEURONS TO IN VIVO INTEGRATION

The oxytocin (OT) system, a key modulator of emotional and social behaviors, is disrupted in neurodevelopmental and psychiatric disorders such as autism, ADHD, anxiety, PTSD, depression, and schizophrenia. Despite its relevance, there are currently no models with sufficient translational value to enable the study of OT in a human-specific context. Human induced pluripotent stem cell (hiPSC)–based approaches provide a versatile framework for modeling OT-related disorders. Here, we present three key achievements establishing this approach: (1) We developed a protocol for differentiating hiPSCs into a paraventricular nucleus (PVN)–like identity by directing cell fate to the alar part of the peduncular hypothalamus, at the intersection of the ventral hypothalamic Rax domain and the dorsal telencephalic Foxg1 domain. Single-nucleus RNA sequencing across multiple developmental time points confirmed the bona fide OT identity of differentiated neurons and enabled a first comprehensive mapping of their developmental trajectory, resolving the earliest regional and developmental identity. (2) Stable long-term spheroid cultures enabled functional characterization of OT neurons, demonstrating electrophysiological activity and responsiveness, together with long-range axonal projections within assembloids toward cortical and midbrain regions, indicating native-like circuit affinity for oxytocin receptor–expressing targets. (3) To advance translational relevance, we transplanted early progenitors into athymic rat brains, where they demonstrate survival, integration, and axonal projections within the host brain. Together, these findings establish a versatile platform for studying human OT biology and modeling complex polygenic OT-related disorders across in vitro and in vivo systems, providing a foundation for future mechanistic studies linking development and circuit targeting.