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E. Picard, J.-C. Jeanny, L. Jonet, I. Fontaine, M. Yefimova, F. Guillou, F. Behar-Cohen, Y. Courtois; Transferrin in Müller Cells and Neuroprotection in the Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):18.
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The retina is very dependent on iron, however this need for iron also makes it especially vulnerable to damaging free radicals. Iron accumulation is found in the retina of aged or in AMD patients, suggesting that iron may play a role in the pathogenesis of AMD. Transferrin (Tf) which binds and transports iron across cells, is crucial for maintenance of iron homeostasis.
To determine if Tf can protect the retina against oxidative stress, we have determined the Tf expression in retina from wild type (WT) and transgenic mice (Tg) with complete human Tf gene and in vitro in Müller cells.
We have detected mTf protein in the inner and outer segments of photoreceptors, in the retinal pigmented epithelial cells and in the ganglion cell layer in WT and Tg mice. In Tg mice retina, hTf has the same localization that in the human retina: RPE and MG cells. In vitro, we have cultured Müller glial (MG) cells from these mice in serum free medium. In primary culture, mTf is detected in the medium of MG cells from WT and Tg mice and hTf is detected in the medium of MG cells from Tg mice. In both cases, Tf secretion decreased with the number of sub-cultures. 100 µM of FeCl3-NTA was added in the culture medium of MG cells for 96h and cell survival was determined by LDH assay or direct cell counting. Application of FeCl3-NTA to MG cells from WT mice caused a decreased (40%) in the cell viability in serum free medium. There was no change in the MG cell number from Tg mice in the same conditions. In vivo, FeCl3-NTA was directly injected in the vitreous of both mice. We compared retinal degeneration by measurement of photoreceptors nuclear layer on histological sections.
Tf in the retina from transgenic mice is expressed not only in the RPE cells but also in MG cells in activated retina or in primary culture. Tf over-expressing in the Tg Müller cells give a protection in vitro against iron induced stress. Thus Tf seems to play an antioxidant role in the pathogenesis of iron induced retinal degeneration and its regulation should be a target for neuroprotection in ageing or AMD.
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