Why is the miRNA expression increasing?

[TytoAlba95]

As presented in Fig. 3A, the expression of miR-141 was increased in the miR-141 mimic transfection group and the increase in miR-141 led to a significantly impaired insulin secretion at 16.7 mM glucose (P<0.05; Fig. 3B)

Source: paper

When the cells were transfected with miRNA-mimic it increased the miRNA expression. Is this increase due to the activity of RNA-dependent RNA polymerase, which generates secondary miRNAs?

 

[Ygggdrasil]

AFAIK, mouse or humans don't have RDRPs to amplify small RNAs. It's likely that the RT-qPCR is detecting the miRNA mimics in addition to the endogenous miRNA.