| Stem cell transplantation | Potential for cell replacement and structural repair Secretion of trophic and immunomodulatory factors Long-term engraftment in some models
| Risk of tumorigenesis and ectopic differentiation Immune rejection and donor variability Low survival after transplantation Invasive delivery required
| Useful where cell replacement is needed (Parkinson’s, spinal cord injury) High regulatory and ethical burden Currently limited by safety concerns
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| Stem cell-derived exosomes | Acellular, lower tumorigenic and immune risk compared to cell grafts Naturally carry miRNAs/proteins that promote neuroprotection and immunomodulation Capable of crossing the BBB (intranasal or engineered IV delivery) Can be engineered for targeted cargo delivery
| Heterogeneous cargo and batch variability Lack of standardized isolation and potency assays Potential off-target effects of miRNA cargo Short in vivo half-life without engineering
| Highly promising for neuroprotection, inflammation control, and synaptic repair Attractive for chronic neurodegenerative diseases and stroke adjunct therapy
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| Gene editing (CRISPR, base editors, prime editing) | | Delivery challenges for CNS (viral vectors, nanoparticles), off-target or unintended genomic alterations Irreversible changes raise major ethical/regulatory challenges Immunogenicity of Cas proteins
| Best suited for monogenic CNS disorders (Huntington’s, SMA) Early-stage, high regulatory scrutiny Not ideal for complex, multifactorial diseases
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| Small molecule drugs | Well-characterized PK/PD profiles Oral or systemic administration possible Scalable manufacturing and low cost Rapid clinical development pathway
| Often symptomatic rather than regenerative Limited ability to cross the BBB Off-target toxicities and drug-drug interactions Short half-life requiring repeated dosing
| Widely used for symptomatic management (spasticity, mood, cognition) Less effective for neuro-regeneration or disease modification
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