Impact of MiR-21 on the Expression of FasL in the Presence of TGF-β1

Background: Micro-ribonucleic acids (miR) are small, noncoding RNA molecules 19 to 25 nucleotides in length that typically function as negative regulators of expression for many target genes involved in cell proliferation, differentiation, and apoptosis. However, the effects of miR-21 on keloid fibroblasts are currently unknown. Objectives: The authors investigate whether miR-21, a specific miR implicated in multiple aspects of keloid fibroblasts, affects the expression of Fas ligand (FasL) in the presence of transforming growth factor (TGF)-beta(1). Methods: The relationship between TGF-(1) and miR-21 expression was investigated by TaqMan quantitative real-time polymerase chain reaction (Life Technologies, Grand Island, New York). FasL protein was determined by Western blotting, and regulation of cell proliferation/migration/apoptosis ability by TGF-beta(1) inhibitor or plasmid was evaluated respectively by EdU incorporation, Transwell assay, and flow cytometry analysis. Results: Fibroblasts from keloid tissue were confirmed to express high levels of TGF-beta(1) and miR-21 compared with normal skin fibroblasts. Expression of TGF-beta(1) and miR-21 was positively correlated in fibroblasts. In addition, cells transfected with TGF-beta(1) inhibitor or miR-21 inhibitor showed significant increases in FasL protein levels and number of apoptotic cells compared with control cells, whereas cell growth and migration significantly decreased. The opposite results could also be confirmed when TGF-beta(1) was upregulated in normal skin fibroblasts. Conclusions: TGF-(1) could effectively influence cell proliferation, apoptosis, and migration via its control of miR-21. These findings also identify a novel mechanism of interaction between TGF-(1) and miR-21 in the regulation of FasL protein, which is involved in keloid formation.