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B. Chang, K. Chalam, M. D. Hunt, R. C. Hunt; Role of TGFβ and IL1β in Vitreous Transformation of Human Retinal Pigment Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1668.
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© ARVO (1962-2015); The Authors (2016-present)
To elucidate the mechanism of the epithelial-mesenchymal transformation (EMT) of retinal pigment epithelial (RPE) cells in vitro in the presence of either vitreous or different cytokines.
Real-time PCR was used to measure mRNA expression. Protein levels were measured using immunoblotting and confocal microscopy.
RPE cells in culture undergo (EMT) when exposed to vitreous as shown by the loss of their cuboidal morphology and the formation of fibroblast-like cells, the formation of lamellipodia, an increase in motility and invasion, enhanced expression of EMT-associated transcription factors (Snail and Slug), and increased expression of α5 integrin. The inhibition of TGFβ signaling in vitreous using a specific inhibitor (SB431542) impedes motility and invasion of the extracellular matrix by RPE cells. SB431542 also decreases the production of Snail, Slug and α5 integrin in the presence of vitreous. RPE cells grown in the presence of TGFβ, a cytokine that is highly expressed in PVR patients, exhibit a different appearance. Although TGFβ increases Snail and α5 integrin expression, it promotes stress fiber formation and down regulates Slug transcription. It does not increase motility or invasion. TGFβ causes RPE cells to differentiate into myofibroblasts as indicated by the expression of two markers: CTGF and α-smooth muscle actin (SMA), while vitreous induces a different transformed phenotype. It was found that vitreous decreases TGFβ transcription, while it increases the expression of the mRNA encoding IL1β. Furthermore, IL1β down regulates CTGF and SMA. Addition of IL1β to TGFβ can also elevate Slug transcription mimicking the vitreous effect.
Our data indicate that vitreous or TGFβ cause RPE cells to undergo EMT. TGFβ causes the cells to become myofibroblasts while vitreous causes a different phenotype. TGFβ is required for some of the changes observed in vitreous-treated cells. Our data further suggest that the difference between TGFβ-treated and vitreous-treated cells may be the presence of extra factors in vitreous, one of which may be IL1β.
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