Effect of Exosomes Derived from Bone Marrow Mesenchymal Stem Cells on Corpus Callosum of Cuprizone Model of Multiple Sclerosis of Mice: Histological Study

Abstract Introduction Multiple sclerosis (MS) is a frequent demyelinating disease of the central nervous system (CNS) affecting both white and gray matter. It is considered one of the leading causes of non-traumatic disability in young adults. Cuprizone is a copper-chelating agent that is used to induce toxic demyelination model in rodents. Currently, no remyelination therapy is available for MS and alternative strategies are being tested. Aim of the Work To study the effect of exosomes derived from bone marrow mesenchymal stem cells (MSCs) on corpus callosum of cuprizone model of multiple sclerosis of adult male mice. Materials and Methods Forty-seven adult male mice with an average weight of 20-50 grams were used in this study. Five mice were used for isolation and culture of bone marrow MSCS and then extraction of exosomes. Forty-two adult mice were randomly divided to 2 groups 21 mice each: Group I (Control group n = 21): equally subdivided into 3 subgroups and sacrificed after 2 and 3 months. Group II (Cuprizone-treated group n = 21): received 400 mg/kg/day of cuprizone suspended in 1ml of distilled water by oral gavage daily for two months. Then they were further subdivided into 3 equal subgroups. Subgroup IIA (Cuprizone subgroup n = 7): sacrificed 24 hours after the last dose of cuprizone suspension (2 months). Subgroup IIB (Cuprizone and MSC- derived exosomes treated subgroup n = 7): 24 hours after the last dose of cuprizone suspension, they received a single intravenous injection of exosomes extracted from the medium from 1 million cells for each mouse suspended in PBS via tail vein and sacrificed after a further one month. Subgroup IIC (Recovery subgroup n = 7): left without treatment for spontaneous recovery for one month after the last dose of cuprizone suspension, then sacrificed. After scarification, brain tissues were dissected and processed using different histological, immune-histochemical techniques and morphometric analysis was performed. Results Histological examination of coronal sections of brain of mice of subgroups IIA and IIC revealed pale stained corpus callosum by H&E with many vacuolated areas, eccentric pyknotic nuclei of oligodendrocyte, area of disrupted nerve fibers, congested blood capillaries, and mononuclear cellular infiltration. Multiple cells with large vesicular nuclei were detected in corpus callosum of subgroup IIB. By luxol fast blue (LFB) staining, dense blue stained corpus callosum was seen in subgroup IIB and control group. Otherwise, pale blue stained corpus callosum was seen in subgroups IIA and IIC. Significant increase in the mean number of caspase-3 positive cells, GFAB positive cells and Iba1 positive cells were observed in animals of subgroup IIA when compared to all the other subgroups. Conclusion Exosomes derived from BMSCs were shown to significantly ameliorate demyelination of corpus callosum of mice in cuprizone model of MS. Therefore, exosomes can be used as a new strategy for treatment of MS.