Engineered Exosome-Mediated CNS mRNA Delivery: Preclinical Validation for ME/CFS
1 Background and Rationale
Kang et al.(Kang et al. 2026) demonstrated that RVG-targeted exosomes carrying HSP70 mRNA can cross the BBB and reverse cognitive deficits and hippocampal neuroinflammation in sleep-deprived mice. While the study establishes proof-of-principle for engineered exosome-mediated CNS mRNA delivery, several gaps separate this finding from any ME/CFS application: (1) the cargo (HSP70) was selected for acute sleep-deprivation neuroinflammation, not chronic neuroinflammation; (2) BBB trafficking kinetics in the setting of chronic inflammation are unknown; (3) repeated-dosing safety and immunogenicity are uncharacterised; (4) ME/CFS-specific cargo candidates have not been evaluated. This preclinical study programme addresses these gaps in a staged sequence.
2 Study E-1: ME/CFS-Relevant Cargo Screening in iPSC Models
Design. Derive induced pluripotent stem cell (iPSC) neurons, astrocytes, and microglia from ME/CFS patients (n=15) and matched healthy controls (n=15). Treat with engineered exosomes carrying candidate therapeutic mRNAs (HSP70, BDNF, IL-10, GDNF, NRF2, and TRPM3 normaliser sequences). Measure: (a) cytokine production (IL-6, TNF-Ξ±, IL-1Ξ², IL-10 multiplex), (b) mitochondrial respiration (Seahorse), (c) neurite outgrowth and synaptic protein expression, (d) microglial activation markers (TSPO, CD68). Hypothesis. ME/CFS-derived cells will show greater responsiveness to exosome-delivered cargo than healthy control cells (higher baseline neuroinflammation creating larger therapeutic window), and the optimal cargo will differ for neuroinflammatory-dominant vs metabolic-dominant patient subgroups.
3 Study E-2: BBB Trafficking in Chronic Neuroinflammation
Design. Utilise a mouse model of chronic low-grade neuroinflammation (low-dose LPS or poly(I:C) over 8 weeks). Administer fluorescently labelled RVG-exosomes (with and without cargo) at weeks 2, 4, and 8. Quantify exosome biodistribution by IVIS imaging and brain region dissection. Compare BBB permeability (Evans blue, CSF/serum albumin ratio) with exosome CNS accumulation. Hypothesis. Chronic neuroinflammation will increase exosome BBB crossing at early timepoints (weeks 2β4, via inflammation-enhanced permeability) but may reduce crossing at later timepoints (week 8, via fibrosis, astrogliosis, or receptor downregulation) β predicting a therapeutic window that narrows with disease chronicity.
4 Study E-3: Repeated-Dosing Safety and Immunogenicity
Design. Administer RVG-HSP70 exosomes to immunocompetent mice thrice weekly for 12 weeks. Monitor: (a) anti-exosome antibody development (ELISA against exosome surface proteins), (b) liver and kidney function, (c) cytokine panels, (d) behavioural and cognitive assessments. Compare exosomes from HEK293T (xenogeneic), MSC (allogeneic), and autologous (syngeneic) sources. Hypothesis. Autologous exosomes will produce the lowest immunogenicity; xenogeneic (HEK293T) exosomes will provoke neutralising antibody responses by week 4β6, reducing therapeutic efficacy; MSC-derived exosomes will show intermediate immunogenicity.
5 Study E-4: Circadian Timing of Exosome Administration
Design. Administer identical doses of fluorescently labelled RVG-exosomes to mice at 4 timepoints across the circadian cycle (ZT0, ZT6, ZT12, ZT18, where ZT0 = lights on). Quantify CNS accumulation at 2, 6, and 24 hours post-administration. Correlate with circadian expression of BBB transporters, endocytic machinery, and nicotinic acetylcholine receptors (the RVG target). Hypothesis. Exosome CNS accumulation will show circadian variation, with peak uptake during the dark (active) phase when BBB transporter expression and endocytic activity are highest. This would identify an optimal dosing window that could improve therapeutic index without changing the exosome dose.