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Placental extract (PE) and exosomes from pregnant mice appear to have immunomodulatory and neuroprotective effects. In this study, we assessed the potential therapeutic effects of PE and exosomes obtained from pregnant mice in experimental autoimmune encephalomyelitis (EAE) mouse models. C57BL/6 mice, 8 to 12 weeks of age, were prepared and administered PE, exosomes, and glatiramer acetate (GA), as an FDA-approved treatment for multiple sclerosis (MS), after EAE induction. Thereafter, the therapeutic effects of treatment were evaluated by measuring the clinical courses of the mice as well as determining the number of regulatory T (Treg) cells using flow cytometry, cytokine levels, and microRNA-326 expression via real-time PCR. GA, PE, and exosomes reduced clinical severity, the extent of spinal cord demyelination, and the infiltration of inflammatory cells into the spinal cord. The frequency of CD4+CD25+FoxP3+ Treg cells increased after treatment of EAE mice with GA, PE, and exosomes. The mRNA expression of the inflammatory cytokines (interleukin-17  and interferon-gamma), as well as miR-326 expression, decreased significantly in the EAE mice after treatment with GA and exosomes. PE and exosomes from pregnant mice are involved in the modulation of Treg/Th17 balance and provide a therapeutic approach for MS. Further clinical studies will hopefully confirm the safety and efficacy of such treatments in MS patients.

An imbalance between regulatory T (Treg) and T-helper (Th)-17 cells has been implicated in the pathogenesis of coronavirus disease 2019 (COVID-19). Mesenchymal stem cells (MSCs) exert immunomodulatory properties through secreting exosomes. This study aimed to assess the effect of MSC-derived exosomes (MSC-Exo) on the differentiation of peripheral blood mononuclear cells (PBMCs) into  Tregs from patients with COVID-19. Exosomes were isolated from adipose tissue–derived MSCs. PBMCs were separated from the whole blood of COVID-19 patients (n=20). Treg frequency was assessed before and 48 hours after treatment of PBMCs with MSC-Exo using flow cytometry. Expression of FOXP3 and cytokine genes, and the concentration of cytokines associated with Tregs, were assessed before and after treatment with MSC-Exo. The frequency of CD4+CD25+CD127-  Tregs was significantly higher after treating PBMCs with MSC-Exo (6.695±2.528) compared to before treatment (4.981±2.068). The expressions of transforming growth factor (TGF)-β1, interleukin (IL)-10, and FOXP3 were significantly upregulated in MSC-Exo–treated PBMCs. The concentration of IL‐10 increased significantly after treatment (994.7±543.9 pg/mL) of PBMCs with MSC-Exo compared with before treatment (563.5±408.6 pg/mL). The concentration of TGF-β was significantly higher in the supernatant of PBMCs after treatment with MSC-Exo (477.0±391.1 pg/mL) than PBMCs before treatment (257.7±226.3 pg/mL). MSC-Exo has the potential to raise anti-inflammatory responses by induction of  Tregs, potentiating its therapeutic effects in COVID-19.