The effect of bone marrow mesenchymal stem cell exosomes on cognitive function and hippocampal neurogenesis of methamphetamine treated male mice

Abstract

Methamphetamine (METH) is a psychostimulant drug that has very destructive effects on the central nervous system. Despite numerous treatment guidelines, there is no ideal treatment or drug option for ameliorating methamphetamine-induced cognitive impairment and its neurodegenerative manifestations. Recently, exosomes extracted from MSCs have shown great promise for the treatment of neurodegenerative sequelae of brain disorders. This study aims to investigate the effects of exosomes extracted from bone marrow mesenchymal cells (BMSCs) as a neuroprotective agent on cognitive deficits and the neurogenesis pathway and inflammation pathway in the hippocampus of male mice that had chronically received methamphetamine. Materials and methods: Forty adult male mice (20-25 g) were randomly divided into 4 groups of 10: Saline group, Meth-Saline group, Saline/exosome group. (Saline-Exo), methamphetamine group/exosome (Meth-Exo). Animals in the second and fourth groups received methamphetamine at a dose of 5 mg/kg intraperitoneally (IP) for 30 days in order to induce the methamphetamine addiction model. Mesenchymal cells were isolated from femur bone marrow of healthy young male mice and cultured after confirmation by flow cytometry. Exosome was extracted from these cells, after confirmation by dynamic light scattering (DLS) method and also by observation through scanning electron microscope (SEM), finally the amount of extracted exosome was determined using Bradford method. In the Saline-Exo and Meth-Exo groups, the exosome was injected at a dose of 30 μg in three times, once a day through the tail vein (IV). One weeks after exosome injection, Barnes' behavioral test was performed to evaluate reference spatial memory and new object recognition test was performed to evaluate recognition memory. In the end, whole brain and hippocampal tissue were separated from the study groups for molecular and histological studies. The expression level of TNF-α and NFᴋβ proteins was measured by western blot method. Also, by means of immunofluorescence staining, the expression level of neurogenesis factors DCX and NeuN as well as microglial inflammatory factor Iba1 was evaluated. Results: Methamphetamine addiction caused defects in spatial memory and recognition memory in animals, and exosomes extracted from bone marrow mesenchymal cells improved these memories. In addition, exosomes increased the expression of neurogenesis-related factors such as NeuN and DCX in the dentate gyrus and CA1 region of the hippocampus, while decreasing the expression of inflammatory cytokines including TNF-α and NF-κB. In addition, BMSC exosomes also decreased the expression of Iba-1, a marker of microglial activation.