Apoptosis related Cleaved-caspase 3 and Bax expression 12 h post infection were also detected and were found decreased in the miRNA-21 treated group, we further assayed apoptosis rate by Annexin V-FITC/PI staining assay and found miRNA-21 could inhibit apoptosis rate compared with control-group, Fig. 4d, e. This evidence concerns the gene BAX and infection.