Abstract
In utero hematopoietic cell transplantation (IUHCT) utilizes fetal immune tolerance to achieve durable chimerism without conditioning or immunosuppression during a unique window in fetal development. Though donor cells have been observed within the nervous system following in utero injection, the timeline and distribution of cellular trafficking across the blood-brain barrier following IUHCT is not well understood. We injected 20 × 106 adult bone marrow mononuclear cells intravenously at gestational age (GA) 12-17 days and found that donor cells were maximally concentrated in the brain with treatment between GA 13-14. Donor cell engraftment persisted within the brain at every timepoint analyzed and concentrated within the hindbrain with significantly more grafted cells than in the forebrain. Additionally, transplanted cells terminally differentiated into various nervous system cellular morphologies and also populated the enteric nervous system. This study is the first to document the timeline and distribution of donor cell trafficking into the immune-protected nervous system and serves as a foundation for the application of IUHCT to treat neurogenetic diseases.