To further confirm the regulation of class II HDACs (HDAC5 and HDAC6) on the expression of COX2 and Ang II‐induced cardiac hypertrophy, we performed expression knockdown of HDAC5 and HDAC6 genes in H9C2 cells via CRISPR/Cas9 gene‐editing plasmids. The gene discussed is HDAC5; the disease is cardiac hypertrophy.