Hippocampal exosomes from stroke aggravate post-stroke depression by regulating the expression of proBDNF and p75NTR and altering spine density

Post-stroke depression (PSD) affects millions of patients who suffer cerebral stroke. However, the molecular mechanisms and pathophysiology are poorly understood. Previous studies have shown that exosomes have been proven to be involved in neuropsychiatric disorders such as stroke and post-stroke depression in neurotransmitter release, neuronal remodeling, and neuron angiogenesis. Here we extracted and purified hippocampal exosomes from stroke mouse model to investigate mechanisms of hippocampal exocytosis in PSD assessed by using behavioral tests and biochemical methods. Aiming at the effect of hippocampal exosomes from stroke on the development of PSD, behavioral test was compared including sugar water preference experiment, open fields, forced swimming test, to explore it in depth. Further, the expression of depression-related protein (proBDNF and p75NTR) and synapse-associated proteins (Synaptotagmin and PSD95) was evaluated by Western blotting, RT-qPCR or immunofluorescence staining. Density of dendritic protrusions of neurons was assessed by Golgi staining to measure changes in spine density after the treatment of hippocampal exosomes from stroke. Our results revealed that injection of exosomes from stroke models significantly aggravated depressive-like behaviors, increase of depression-related protein (proBDNF and p75NTR) expression and deficiency of synapse-associated proteins (Synaptotagmin and PSD95) expression, and the decreased number of spin density. Our findings together suggest that hippocampal exosomes from stroke cause exacerbation of depressive-like behavior in mice, possibly resulting from the regulation of neurogenesis by its depression-associated proteins (proBDNF and p75NTR). Therefore, hippocampal exosomes from stroke are promising targets for the diagnosis and treatment of PSD.