PDGF-BB Enhances the Proliferation of Cells in Human Orbital Fibroblasts by Suppressing PDCD4 Expression Via Up-Regulation of microRNA-21.

Purpose: The aim of this study was to investigate the effect of platelet-derived growth factor (PDGF)-BB on the proliferation of cells and its possible mechanism in human orbital fibroblasts.

Methods: Human orbital fibroblasts were obtained from orbital fat from decompression surgery in patients with thyroid-associated ophthalmopathy (TAO). The cells were treated with PDGF-BB, and the number of cells was counted using an Advanced Detection and Accurate Measurement (ADAM) automatic cell counter. The expression of programmed cell death 4 (PDCD4) was determined by Western blotting. The effect of PDCD4 on cell proliferation was evaluated using PDCD4 small interfering RNA (siRNA)-transfected cells. The level of microRNA-21 (miRNA-21) was measured by quantitative real-time RT-PCR. In addition, the role of miRNA-21 in the proliferation of PDGF-BB-treated cells was assessed by means of anti-miRNA-21 siRNA and resveratrol (trans-3,4',5-trihydroxys-tilbene), an inhibitor of miRNA-21.

Results: PDGF-BB was found to enhance cell proliferation, whereas it inhibited PDCD4 expression in human orbital fibroblasts. Down-regulation of PDCD4 by PDCD4 siRNA transfection significantly increased the number of human orbital fibroblasts. In addition, PDGF-BB increased the level of miRNA-21 in human orbital fibroblasts. Transfection with anti-miRNA-21 and treatment with resveratrol partially restored the expression of PDCD4 and led to a reduction in cell number in PDGF-BB-treated orbital fibroblasts.

Conclusions: PDGF-BB enhances proliferation by suppressing PDCD4 expression by up-regulation of miRNA-21 in human orbital fibroblasts. These results suggest that PDGF-BB stimulates cell proliferation through microRNA-21-mediated PDCD4 down-regulation, leading to the development of TAO.