Abstract: Objective To investigate the expression and function of miR-21 (microRNA-21) in the formation of the keloid, and provide a new direction for the prevention and treatment of the scar. Methods Normal skin tissue and keloid were harvested for histological detection and cell culture in vitro. Real-time PCR was used to detect the expression of mir21, Smad7, Col 1 A1 and Col 3 A1 in normal and keloid fibroblasts. The expression of Smad7, Col 1 A1 and Col 3 A1 with miR-21 mimics and anti-miR-21 oligonucleotides were also detected by Western-Blot and Real-time PCR. The cell proliferation was also detected by crystal violet assay. Results The content of collagen was significantly higher in keloid tissue than that of normal skin. The expression of miR-21, Col 1 A1 and Col 3 A1 were higher in keloid fibroblasts than that of normal fibroblasts, while the expression of Smad7 was lower. After transfection, the expression of Smad7 was decreased, the expression of scar related genes and cell proliferation were increased in normal fibroblasts. And the contrast results were observed in keloid fibroblasts after transfection. Conclusion The high expression of miR-21 can increase the expression of scar related genes and promote the proliferation of fibroblasts in vitro, which may be an important cause of the formation of the scar.

Key words: microRNA, Keloid, Extracellular matrix, Cell proliferation, Fibrosis