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H.L. Deissler, G.K. Lang, G.E. Lang; TGFbeta Induces Transdifferentiation of iBREC Into AlphaSMA–Expressing Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):139.
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© ARVO (1962-2015); The Authors (2016-present)
Transforming growth factor (TGF)ß1 not only inhibits proliferation of endothelial cells but also promotes transdifferentiation of macrovascular endothelial cells (EC) to α–smooth muscle actin (αSMA)–expressing mesenchymal cells in vitro. Recently, we could confirm that proliferation of immortalized bovine retinal microvascular endothelial cells (iBREC) is strongly inhibited by TGFß1/2. In order to investigate whether microvascular EC can also transdifferentiate into αSMA–expressing cells, iBREC were treated with TGFß1/2 for several days and changes of morphology as well as αSMA–expression were studied.
iBREC, recently established by ectopic expression of hTERT, were treated with 10 ng/ml TGFß1 or TGFß2 in different low–serum media for up to 10 days and immunostained for the expression of the EC–markers von Willebrand factor (vWF) and VE–Cadherin (CD144) or αSMA, respectively. In addition, cells were treated with TGFß2 in the presence of either 10 ng/ml bFGF, VEGF or IGF–1 for several days and their influence on αSMA–expression was measured.
iBREC completely lost their cobble–stone morphology and adopted a ragged morpholgy after incubation for 4 to 7 days with TGFß2 which is the predominant isoform expressed in the eye. Depending on the type of culture medium, 1 to 30% of these cells strongly expressed αSMA whereas expression of vWF and CD144 declined. Results obtained with parental iBREC cells were confirmed with single cell–derived subclones. Similar results were obtained with TGFß1. αSMA–expression, associated with the formation of stress fibers, was first detected in single isolated cells and then spread to adjacent cells. Induction of αSMA was strongly inhibited by bFGF but not by VEGF or IGF–1. Re–induction of vWF–expression was never observed. Loss of cobble–stone morphology and αSMA–expression was not observed after treatment of iBREC with VEGF, IGF–1 and bFGF.
We showed that microvascular endothelial cells represented by iBREC can transdifferentiate into αSMA–expressing cells in vitro. These findings have an impact on the understanding of development of microvascular complications of diabetes like diabetic retinopathy, in which loss of pericytes might be a crucial event.
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