Abstract
Purpose :
Myofibroblasts play a critical role in various ocular fibrotic complications. Retinal pigment epithelial (RPE) cells have been identified as a potential source of myofibroblasts involved in fibrosis of the retina such as proliferative vitreoretinopathy (PVR) and fibrosis associated with exudative AMD. Myocardin-related transcription factor (MRTF) pathway has been implicated to play essential roles in several fibrotic diseases. However, the role of MRTF signaling in myofibroblast transdifferentiation of RPE cells is yet to be determined, and thus, the purpose of this study was to examine its role in this process.
Methods :
Primary cultured porcine RPE cells were used at 2nd passage for the experiments. Immunocytochemical staining was utilized to localize MRTF-A. Expression of myofibroblast markers alpha smooth muscle actin (aSMA) and tropomyosin1 (TPM1) was examined by western blot analyses. Collagen matrix contraction assay, with cells cultured atop of type I collagen hydrogels, were used to assess myofibroblast function. MRTF signaling inhibitors CCG-1423 and CCG-203971 were used examine the role of MRTF signaling in TGF-β induce myofibroblast transdifferentiation, while a MRTF signaling agonist ISX-9 was used to examine the role of MRTF in the absence of TGF-β.
Results :
TGF-β induced nuclear localization of MRTF in cultured RPE cells, and induced myofibroblast transdifferentiation based on both expression of marker proteins as well as increased contractility. TGF-β induced MRTF nuclear accumulation and subsequent myofibroblast transdifferentiation were blocked by MRTF signaling inhibitors CCG-1423 and CCG-203971. In contrast, MRTF signaling agonist ISX-9 enhanced expression of myofibroblast marker proteins and collagen gel contractility in the absence of exogenous TGF-β.
Conclusions :
Our data using both inhibitors as well as an agonist of MRTF signaling demonstrate that this pathway plays a key role in myofibroblast transdifferentiation of RPE cells. Therefore, MRTF could potentially be targeted to prevent retinal fibrotic complications in which RPE-derived myofibroblasts are considered to play key roles, such as PVR and fibrosis associated with wet AMD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.