Curing Autism, Epilepsy & Schizophrenia with Stem Cells
Summary
Dr. Sergiu Pașca, professor of psychiatry and behavioral sciences at Stanford and director of the Stanford Brain Organogenesis Program, discusses the biology and genetics of autism spectrum disorder, why its prevalence is rising, and the groundbreaking stem cell technologies his lab is developing. He explains how organoids and assembloids—three-dimensional human brain circuits grown from stem cells—are enabling researchers to study psychiatric diseases like profound autism and schizophrenia at the cellular level, and how these models are being used to develop the first targeted clinical therapies.
Key Takeaways
- Autism is not one disease. It is behaviorally defined, lacks biomarkers, and likely represents hundreds of distinct genetic conditions grouped under a single umbrella term—much like “fever” once was in 19th-century medicine.
- Prevalence is near 3% of the general population, up significantly from when it was considered rare; increases are seen globally, not just in the United States, making US-specific environmental explanations insufficient.
- Strong genetic heritability is the most robustly supported finding in autism research. Hundreds of genes—affecting synaptic proteins, ion channels, and chromatin packaging—are associated with specific forms of autism.
- Only ~20% of profound autism patients receive a specific genetic diagnosis today; the rest remain in an “idiopathic” category where the precise cause is unknown.
- The Yamanaka factors (induced pluripotent stem cells / iPS cells) revolutionized neuroscience research by allowing any patient’s skin cells to be reprogrammed into neurons—eliminating the need for human embryonic tissue.
- Organoids recapitulate real developmental timing, including canonical molecular switches like the NMDA receptor 2B-to-2A subunit shift that occurs around the equivalent of birth—without any external hormonal cues.
- Unregulated stem cell injections offered in clinics abroad are scientifically unsupported for autism and carry serious risks, including infection, tumor growth, and permanent neurological damage.
- Gene therapy using CRISPR holds promise but faces major hurdles for brain disorders: delivery to the right cells, limited viral cargo size, irreversibility, and the timing problem of how early intervention must occur.
- Human brain myelination continues through the third decade of life, underscoring how prolonged and vulnerable neurodevelopment is compared to other organs.
Detailed Notes
What Is Autism?
- Autism is a behaviorally defined spectrum disorder—diagnosed by the presence and absence of specific behaviors at certain developmental ages, with no biological biomarker.
- Diagnosed in approximately 1 in 30–40 individuals (close to 3%), up from rare-disease status decades ago.
- Male-to-female ratio is roughly 4:1, though diagnostic under-detection in females (“masking”) and differences in nervous system resilience and maturation pace are likely contributing factors.
- Profound autism—the most severe end of the spectrum—is commonly co-occurring with intellectual disability and epilepsy, and is often linked to identifiable genetic mutations.
- The condition is better understood as analogous to historical “fever”: a behavioral signal with many distinct biological causes requiring different treatments.
Why Is Prevalence Rising?
- Broadened diagnostic criteria and diagnostic migration (e.g., children previously diagnosed with intellectual disability now meeting autism criteria) account for some increase.
- Highly heritable component—among the highest heritability of any psychiatric disorder—but many causative variants are individually rare.
- Environmental factors (e.g., thalidomide during pregnancy increases autism risk) contribute, but no single environmental cause has been established.
- No solid evidence supports vaccines as a cause; the foundational paper supporting that claim has been retracted and the association has not been replicated epidemiologically.
- Rising prevalence is global, observed in South Korea, Scandinavia, and elsewhere—undermining arguments tied to US-specific exposures.
Genetics of Autism
- Hundreds of genes are implicated, falling into major categories:
- Synaptopathies: mutations in synaptic proteins
- Channelopathies: mutations in ion channels (e.g., calcium channels)
- Chromatinopathies: mutations in DNA-packaging proteins
- Timothy Syndrome is a well-characterized monogenic form: a single nucleotide change in a calcium channel gene (CACNA1C) causes the channel to stay open longer, resulting in autism, epilepsy, and cardiac abnormalities.
- Many autism-associated genes are also expressed in peripheral tissues (skin, sensory neurons), raising the possibility that peripheral disruptions during development can perturb central nervous system wiring—supported by elegant animal experiments from David Ginty’s lab at Harvard.
- Mutations can be inherited or arise de novo (not present in either parent); humans naturally acquire ~80 new mutations, ~30 of which are protein-truncating.
Gene Therapy and CRISPR
- Gene therapy broadly encompasses: delivering a missing gene (via viral vector), delivering a functional protein directly, or correcting a mutation at the DNA level using CRISPR.
- Sickle cell anemia has been successfully treated using CRISPR because the target cells (blood cells) are easily accessible.
- Brain delivery is far more challenging:
- Intrathecal (spinal canal) or direct surgical injection are options but have low efficiency.
- Adenoviruses / AAVs are commonly used vectors; they are modified to be non-pathogenic but cannot carry very large genes (e.g., calcium channel genes are too large).
- Immune responses limit repeated dosing—typically one shot only.
- Gene edits are irreversible once integrated.
- A downstream RNA-level strategy (rather than direct DNA correction) is currently more practical and is the approach Pașca’s lab is pursuing.
- Timing is critical: the window in which correction is therapeutically meaningful for neurodevelopmental disorders is not yet well defined.
Induced Pluripotent Stem Cells (iPS Cells) and the Yamanaka Discovery
- In 2006–2007, Shinya Yamanaka demonstrated that adult skin cells could be reprogrammed back into pluripotent stem cells by introducing four transcription factors (the “Yamanaka factors”)—reversing what was thought to be a one-way developmental street.
- This discovery eliminated the need for embryonic stem cells and the associated ethical controversies.
- iPS cells can be:
- Maintained indefinitely (frozen and revived without change)
- Differentiated into virtually any cell type, including neurons
- Derived from any patient via a simple skin biopsy
Organoids: Brain-in-a-Dish
- Organoids are three-dimensional, self-organizing clusters of human neurons grown from iPS cells—not flat, two-dimensional cultures.
- Key advantages:
- Neurons develop in 3D, surviving far longer (months to years) than in flat dishes
- Development tracks real human developmental timing, including molecular switches like the NMDA receptor 2B→2A subunit transition at approximately nine months—occurring without any birth-related hormonal cues
- Can be derived from patients with specific diseases, allowing direct comparison of patient vs. healthy donor neurons
- Pașca’s lab maintains the longest-running organoid cultures ever reported—some kept for over 800 days.
- Key finding in Timothy Syndrome organoids: calcium influx in patient-derived neurons was prolonged compared to controls, directly demonstrating the channel defect in human neurons for the first time.
Stem Cell Injections: What the Evidence Says
- Umbilical cord stem cells are already restricted in potency—applicable mainly to blood disorders, not universally useful for future stem cell therapies despite commercial marketing.
- Unregulated commercial stem cell injections (offered in Mexico, Colombia, and some European clinics) for autism and other conditions:
- Lack scientific rationale (no specific cell type is known to be “missing” in autism)
- Often involve cells of unknown origin or type
- Carry risks of infection, tumor formation, and neurological damage
- Any reported improvements are likely due to strong placebo effects by proxy (in parents), natural developmental milestones, or non-specific inflammatory effects resembling the “fever effect”