CD55 and atrial fibrillation: The MSC secretome treatment of human AF cells did not affect the gene expression of CD46 and CD59 but significantly upregulated CD55 (*p < 0.05), IL-6, and IL-8 (**p < 0.01) and increased the production of PGE2 (***p < 0.001) compared to unstimulated AF cells (Figure 4B, D–F).