TGF-β-induced interleukin-6 participates in transdifferentiation of human Tenon’s fibroblasts to myofibroblasts

PURPOSE: To gain a better understanding of the roles of interleukins (ILs) in subconjunctival fibrosis, we investigated their expression in transforming growth factor-β1 (TGF-β1)-stimulated Tenon’s fibroblasts and examined their association with the transdifferentiation of fibroblasts to myofibroblasts. METHODS: After primary culture, fibroblasts derived from human Tenon’s capsule were exposed to TGF-β1. The expression of α-smooth muscle actin (α-SMA) protein was assessed by western immunoblots and immunofluorescence. The mRNA levels of various ILs were also evaluated by multiplex reverse transcription (RT)-PCR. Using the small interfering RNAs (siRNAs) specific for IL-6 and IL-11 and the promoter deletion assay, the contributions of IL-6 and IL-11 to TGF-β1-induced induction of α-SMA were determined. RESULTS: In human Tenon’s fibroblasts, TGF-β1 stimulated the expression of α-SMA protein determined by western blot analysis and also increased the mRNA levels of IL-6 and IL-11 determined by multiplex RT-PCR. On the western immunoblots and immunofluorescence, the increased expression of α-SMA was attenuated only by the siRNAs specific for IL-6 but not by the siRNAs specific for IL-11. When the activator protein-1 binding sites of the IL-6 promoter region were deleted, the stimulation effects of TGF-β1 decreased. CONCLUSIONS: Our data show that autocrine IL-6 may participate in the TGF-β1-induced transdifferentiation of human Tenon’s fibroblasts to myofibroblasts, which is known to be an essential step for subconjunctival fibrosis.