Cerebral Organoids Yield Insights Into Ebola, Parkinson's, Alzheimer's and Neural Recording

Human cerebral organoids have revealed how Ebola virus persists in neural tissue, helped identify a possible treatment for a rare childhood Parkinson's disease, and been paired with soft bioelectronics that map activity across nearly the entire tissue. In one study, Ebola virus and related filoviruses replicated in cerebral organoids for up to 120 days. In another, a bioelectronic mesh was used to record from hundreds of locations across an organoid's surface.

In a study from the Icahn School of Medicine at Mount Sinai and the Bernhard Nocht Institute for Tropical Medicine, cerebral organoids designed to mimic aspects of the human brain revealed that Ebola virus and related filoviruses including Sudan, Reston and Marburg viruses were able to replicate for up to 120 days. The organoids were developed from human induced pluripotent stem cells guided to form three-dimensional structures containing multiple cell types found in the central nervous system. The virus infected neurons, astrocytes and microglia — the brain's immune cells — and spread both through direct cell-to-cell contact and by budding from infected cells. Although infected organoids produced pro-inflammatory cytokines, the immune response was not sufficient to eliminate the virus, and inflammation increased in late-stage cultures. The researchers also identified defective viral genomes, mutations and viral particles that appeared during prolonged infection, suggesting a form of "productive persistence" in which the virus remains active and infectious rather than dormant.

In a separate advance, a team led by Northwestern University and Shirley Ryan AbilityLab scientists developed a soft, three-dimensional electronic framework that wraps around an organoid like a breathable mesh, delivering near-complete coverage with hundreds of miniaturized electrodes. The technology, described in the journal Nature Biomedical Engineering on Feb. 18, allows scientists to map and manipulate neural activity across almost the entire organoid, moving from localized probing to true whole-network mapping. The researchers noted that human stem cell-derived organoids enable patient-specific studies of how tissues respond to drugs and emerging therapies, but existing instruments designed for flat layers of cells do not interface well with spherical organoids.

Cerebral organoids grown from patients' own cells have also helped identify an affordable treatment for an ultra-rare form of childhood Parkinson's disease caused by mutations in the DHDDS gene. Researchers at the Wilhelmina Children's Hospital in Utrecht observed significant signs of deterioration in the mini brains after four months, mirroring the disease progression in children. In healthy cells, DHDDS helps make dolichol, a small fat-like molecule that acts as a platform for attaching sugars to proteins; when DHDDS doesn't work properly, cells struggle to attach sugar chains, and cholesterol builds up in astrocytes, leading to mitochondrial dysfunction and reduced energy production. A yeast-based screen identified nicotinamide mononucleotide, a naturally occurring type of vitamin B3, as a potential modifier of DHDDS-driven cellular stress. The vitamin had positive effects on the mini brains, and when families of patients began using the over-the-counter supplement, walking improved, energy increased and tremors lessened within weeks. Funding has been received to start an international trial in which patients will take nicotinamide mononucleotide for a year and be evaluated every three months.

In another study, human iPSC-derived cerebral organoids maintained for more than 100 days were used to model neuroinflammation and Alzheimer's disease. When organoids were activated with a pro-inflammatory cytokine cocktail (TNF-α, IL-1α, IL-1β), they released more cytokines and showed increased inflammatory gene expression; treatment with dexamethasone, a glucocorticoid receptor agonist, reversed the inflammatory response. In the Alzheimer's model, incubation with Aftin-4 increased Aβ42 secretion and the Aβ42/Aβ40 ratio, and treatment with LY2886721, a BACE1 inhibitor, drastically reduced the ratio, indicating that amyloidogenic processing can be pharmacologically reversed. These findings demonstrate that the organoid system can be used to test and assess CNS-targeted therapies.

As a group, the studies illustrate the expanding role of cerebral organoids in disease modeling, drug safety testing and regenerative medicine. Because the organoids behave similarly to human infections in some cases, they underscore the suitability of the model for investigating persistent viral infections and for evaluating therapeutic interventions.