Effectiveness of Exosomes from Different Mesenchymal Stem Cells in the Treatment of Psoriasis: A Murine Study and Meta-Analysis of Experimental Studies

<b>Background/Objectives</b>: Psoriasis is a chronic systemic inflammatory disease. Evidence on the efficacy of different mesenchymal stem cell (MSC) exosomes for psoriasis remains limited. This study aimed to evaluate the therapeutic effects of different MSC exosomes in mitigating psoriasis. <b>Methods:</b> The efficacy of human placenta MSC (hPMSC) and human umbilical cord MSC (hUCMSC) exosomes was compared in an imiquimod (IMQ)-induced psoriasis murine model. A meta-analysis was performed to incorporate the results of studies using IMQ-induced psoriasis murine models to compare MSC exosome treatments (exosome group) with vehicle or no-treatment controls (control group). <b>Results:</b> In this murine study, both the hPMSC and hUCMSC exosomes showed better effectiveness in reducing epidermal thickness and skin tissue cytokines than controls, but no significant difference was observed between the two MSC exosomes. Seven studies were included in the meta-analysis. Clinical severity scores were significantly lower in the exosome group than in the controls (standardized mean difference [SMD]: -1.886; 95% confidence interval [CI]: -3.047 to -0.724). Epidermal thickness was significantly reduced (SMD: -3.258; 95% CI: -4.987 to -1.529). No significant differences were found in most skin cytokines between the groups, although tumor necrosis factor-α mRNA (SMD: -0.880; 95% CI: -1.623 to -0.136) and interleukin-17A protein levels (SMD: -2.390; 95% CI: -4.522 to -0.258) were both lower in the exosome group. Meta-regression revealed a greater improvement in clinical scores in studies using hUCMSC exosomes compared to other MSC sources (<i>p</i> = 0.030). <b>Conclusions:</b> hUCMSC exosomes have been studied more extensively than other MSC exosomes. MSC exosomes reduce clinical severity and epidermal hyperplasia.