Overview
- The study, which published on Wednesday, Sept. 16, used genetically engineered mice that lack most of their cortex and hippocampus so lab-grown human cortical organoids could be engrafted into the vacant cavity.
- Transplants took hold in 25 of 29 surgeries and the human tissue expanded about fivefold to occupy more than 90 percent of the mouse cortical space within two to three months.
- Multiple tests showed the grafts produced diverse human cortical cell types, including rare von Economo neurons, formed anatomical and electrical connections into the mouse nervous system, and sent projections as far as the spinal cord.
- Behavioral assays found broadly preserved locomotion but selective differences in memory and limb coordination, and a proof-of-concept oxygen‑deprivation experiment produced human‑cell injury and gait abnormalities not seen in ordinary mice.
- The team and independent ethicists stress clear biological limits—the grafts lack full human cortical architecture and mature features—and they rule out primate experiments while planning disease-focused studies and continued ethical oversight.