Abstract A018: Clinical and Experimental Study of Microbiome-Based Gut-Thymus-Brain Axis Modulation in Preserving Thymic Function and Enhancing Cognitive Recovery After Stroke

Background: Poststroke cognitive impairment (PSCI) is a leading cause of long-term disability. Immunosenescence, marked by thymic involution and T-cell aging, drives chronic neuroinflammation. The gut microbiota regulates thymic T-cell differentiation and peripheral expansion, while dysbiosis accelerates thymic atrophy and T-cell aging, forming a “gut–thymus–T-cell aging” axis. Whether this axis affects brain injury and cognition after stroke is unknown. We hypothesize that targeted microbiome modulation can restore gut–thymus–brain homeostasis, preserve thymic function, and delay immunosenescence, thereby reducing brain injury and improving cognition. Methods: Clinical study: 151 stroke patients (>3 months) were assessed with MMSE and MoCA. Flow cytometry, ELISA, and 16S rDNA sequencing evaluated T-cell aging, thymic function, intestinal permeability, and microbiota composition. Animal study: Male 6–8-month-old mice underwent photothrombotic MCAO and received intragastric Faecalibacterium prausnitzii (Fp) or vehicle. Neurological and cognitive functions were tested. Fecal 16S rDNA sequencing and plasma metabolomics were performed. RT-qPCR, immunofluorescence, histology, and RNA-seq analyzed thymus and brain. Results: Clinically, PSCI patients showed greater T-cell aging, thymic involution, and intestinal permeability versus non-PSCI, with Fp abundance positively correlating with thymic and cognitive function. In mice, Fp improved neurological and cognitive performance, preserved intestinal architecture, reduced inflammation, restored thymocyte counts and output, improved cortex–medulla ratio, and increased naïve T cells. In the brain, Fp reduced neuroinflammation and alleviated synaptic loss. Microbiota analysis revealed increased beneficial species and improved GMHI. Metabolomics showed reduced proinflammatory metabolites (prostaglandin 2, tremetone, ibotenic acid) and increased neuroprotective tryptophan derivatives. Thymic RNA-seq indicated regulation of MAPK, IL-17, T-cell receptor, and senescence pathways; brain RNA-seq revealed suppression of innate immunity and glial activation with enhanced synaptic maturation. Conclusion: This integrated clinical–preclinical study demonstrates that microbiome-based restoration of the gut–thymus–brain axis via Fp preserves thymic function, counteracts immunosenescence, and promotes cognitive recovery after stroke. These findings position targeted microbiota interventions as a promising therapeutic avenue for PSCI.