IDO1 and familial dilated cardiomyopathy: To determine the importance of IDO expression in the therapeutic effect of hUCMSCs in DCM rats, we treated hUCMSCs with IFN-γ and TNF-α to induce IDO over-expression (DO-OE) or transfected hUCMSCs with IDO-specific siRNA to knockdown IDO expression (IDO-KD) (Fig. 3A).