Epitheliomesenchymal Transdifferentiation of Cultured RPE Cells

Abstract

Retinal pigment epithelium (RPE) cells of the proliferative vitreoretinopathy (PVR) membrane take on the shape of fibroblasts and participate in fibrosis, thus deviating from the character of epithelial cells. This study was undertaken to evaluate RPE cell transdifferentiation in vitro. During the culture of porcine RPE cells, primary and 10th-passaged RPE cells were investigated for cell growth in response to transforming growth factor (TGF) β₂, change of phenotype and amount in collagen synthesis as well as expression of α-smooth-muscle actin (α-SMA). TGF-β₂ inhibited the proliferation of the primary cultures of RPE cells in a dose-dependent manner, while the spindle-shaped 10th-passaged RPE cells were not inhibited by TGF-β₂. The 10th-subcultured cells did not show much difference in the quality of collagen synthesis, other than type VIII collagen which was not produced. Collagen synthesis was dose-dependently stimulated by TGF-β₂. The stimulation by TGF-β₂ in the 10th-passaged RPE cells was much greater than in primary RPE cells. The 10th-subcultured RPE cells produced substantial α-SMA compared to α-SMA production by primary RPE cells. These results were also observed by confocal laser microscopy. These findings indicated that RPE metaplasia resulting in a change of biological cell behavior might be a necessary predisposing step in the development of PVR.

TGFβ pathobiology in the eye

“…As in the EMT-related fibrosis in the lens, TGFb can induce transformation of RPE cells to myofibroblast-like cells in vitro, [76][77][78] suggesting that TGFb is likely a key player in the development of PVR, although various other growth factors, including PDGF, HGF, and activin, are all reportedly involved in its pathogenesis. [79][80][81][82][83][84][85] The concentration of TGFb2 in the vitreous humor of the eye correlates with the severity of the PVR, underlying its importance.…”

Smad3 Regulates Rho Signaling via NET1 in the Transforming Growth Factor-β-induced Epithelial-Mesenchymal Transition of Human Retinal Pigment Epithelial Cells

“…In EMT-related retinal fibrosis, TGF-␤ can induce the transformation of retinal pigment epithelial (RPE) cells to myofibroblast-like cells in vitro (16,19,20), implicating TGF-␤ as a key player in the development of proliferative vitreoretinopathy (PVR). Various other growth factors, including platelet-derived growth factor, hepatocyte growth factor, and activin, are also reportedly involved in PVR pathogenesis (21)(22)(23)(24)(25).…”

Smad3 is required for dedifferentiation of retinal pigment epithelium following retinal detachment in mice

“…2,5 Although various growth factors, including platelet-derived growth factor (PDGF), hepatocyte growth factor (HGF), connective tissue growth factor (CTGF), transforming growth factor-b (TGF-b), and another member of the TGF-b superfamily, activin, are all reportedly involved in the pathogenesis of PVR, [6][7][8][9][10][11] we have focused on TGF-b, because of its correlation with disease severity 12 and its welldescribed effects on EMT of a variety of epithelial cell types. [13][14][15][16] TGF-b2 is expressed at much higher levels than the other TGF-b isoforms in the vitreous humor 12,17 and is a likely mediator of EMT in RPE cells in vivo, although the specific signaling pathways involved have not been identified.…”

“…[13][14][15][16] TGF-b2 is expressed at much higher levels than the other TGF-b isoforms in the vitreous humor 12,17 and is a likely mediator of EMT in RPE cells in vivo, although the specific signaling pathways involved have not been identified. 5,18,19 Moreover, PDGF, TGF-b1 and CTGF are each known to be targets of TGF-b2 signaling, [20][21][22][23] suggesting that TGFb2 could orchestrate the secondary effects of these other peptides on EMT and fibrosis in PVR.…”