The effects of ubiquitin-specific protease 4 (USP4) on cell proliferation, apoptosis, and migration of hypertrophic scar fibroblasts cultured in vitro. (A) The transfection rate of USP4 in hypertrophic scar fibroblasts measured by quantitative real-time polymerase chain reaction (qRT-PCR). After transfection with siUSP4, the mRNA level of USP4 was significantly inhibited. (B) The Cell Counting Kit-8 (CCK-8) assay was performed to detect the activity of hypertrophic scar fibroblasts in vitro. The results show that the viability of cells transfected with siUSP4 is significantly reduced. (C) Flow cytometry for cell apoptosis shows that after transfection with siUSP4, the cell apoptosis rate is significantly increased. (D) The wound-healing assay detected cell migration. The results show that 24 h after the test, the width of the cell defect in the cells transfected with siUSP4 was significantly greater than that of cells in siNC group. ** p<0.01, *** p<0.001 vs. siNC.