Expression, secretion, and age-related downregulation of pigment epithelium-derived factor, a serpin with neurotrophic activity

Mor²,

et al. 2004

Eye

Purpose To study the molecular characteristics of lens epithelial cells from patients with senile cataract by cDNA microarray technique. Methods Lens epithelial cells adhering to anterior capsules taken during cataract surgery collected from 108 patients, aged 56À92 years (senile cataract group), were pooled. Pooled epithelial cells of normal, noncataractous lenses from one patient with ocular trauma, one patient with lens subluxation, and 25 cadaveric eyes, all under the age of 55 years, served as a control. Total RNA was extracted by conventional methods from the two groups of cells, and a fluorescent probe was prepared for each group. The probes were hybridized on 9700 known human cDNA clones. Hybridized clones were analysed using a scanning laser and the results were processed by GEMTools (Incyte Genomics) software. Results A total of 1827 clones hybridized with the two probes. Of these, 400 showed differences of more than two-fold in gene expression between the two probes. Relative to controls, gene expression in the senile cataract lenses was upregulated in 318 clones and downregulated in 82. Three genesfilensin, inwardly rectifying potassium channel (IRPC), and pigment epitheliumderived factor (PEDF) were strongly downregulated (by 41.3-, 6.8-, and 5.9-fold, respectively) in senile cataract. Conclusions Cataractogenesis is associated with numerous changes in the genetic profile of the lens epithelial cells. Since filensin, IRPC, and PEDF genes are known to have important roles in the physiology and morphology of the transparent lens, substantial downregulation of their expression might contribute to the formation of senile cataract.

Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 2 more Smart Citations

Downregulation of gene expression in the ageing lens: a possible contributory factor in senile cataract

Mor²,

et al. 2004

Eye

Experimental Eye Research

“…These biological activities are of great importance for the development and maintenance of normal physiological functions in the eye. Biochemical and immunochemical studies have identified PEDF as a soluble extracellular protein localized in washes of the interphotoreceptor matrix (IPM), vitreous and aqueous of several mammalian species (Tombran-Tink et al, 1995;Wu et al, 1995;Ortego et al, 1996;Alberdi et al, 1998;Karakousis et al, 2001). PEDF, discovered as a product secreted by cultured RPE cells from fetal human eyes (Tombran Tink, 1991), can be released from a variety of cells, including stably transfected eukaryotic cells with full length PEDF cDNA under the control of recombinant transcriptional promoters (Stratikos et al, 1996;Perez-Mediavilla et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Pigment epithelium-derived factor in the monkey retinal pigment epithelium and interphotoreceptor matrix: apical secretion and distribution

Becerra

Fariss

et al. 2004

111

Pigment epithelium-derived factor (PEDF) is an extracellular protein derived from the retinal pigment epithelium (RPE), a tissue formed by polarized cells that release growth and trophic factors in a directional fashion. We have investigated the distribution and directional release of PEDF protein by the monkey RPE. We established primary cultures of monkey RPE cells that expressed the PEDF gene, and that synthesized and secreted the PEDF protein. Northern analysis of RPE cultures and monkey ocular tissues showed that PEDF transcripts were highly expressed in RPE as compared with several other monkey ocular tissues, being even more abundant in cultured cells than they were in the native RPE. The differentiated RPE cells in culture secreted protein that shared the immunological, biochemical and biological characteristics of PEDF. The overall PEDF levels in the RPE conditioned media reached 6·5 mg ml 2 after 8 days in culture (i.e. 1·1 pg of PEDF per RPE cell). RPE cells were cultivated on permeable supports as monolayers forming a barrier between apical and basal compartments. Apical and basal culture media were sampled at three or four-day intervals for 18 cycles, and the PEDF content was quantified. Most of the PEDF protein was significantly higher in the apical than in the basal medium (. 4 times) at the initial recovery intervals, to be detected only in the apical medium at the latter intervals. In the native monkey eye, the concentration of soluble PEDF in the interphotoreceptor matrix (144 nM) was 7-fold and 25-fold greater than in vitreous and aqueous, respectively. PEDF was abundant in the interphotoreceptor matrix surrounding rod and cone outer segments, and was detectable at lower levels in the RPE as visualized by confocal microscopy. We concluded that PEDF synthesized by the RPE is secreted preferentially from the apical surface and is distributed apically to the RPE bordering the outer segments of photoreceptors. PEDF can be a useful marker for RPE polarization and differentiation. The polarization of RPE may be an important mechanism to control PEDF secretion and our results offer interesting possibilities on regulation of PEDF. q

Interphotoreceptor retinoid-binding protein (IRBP): Expression in the adult and developingXenopus retina

et al. 1996

Apposition of the neural retina and pigment epithelium is critical to photoreceptor development and function. Interphotoreceptor retinoid-binding protein (IRBP) is a major component of the extracellular matrix separating these epithelia in the African clawed frog Xenopus laevis (Gonzalez-Fernandez et al., [1993], J. Cell Sci. 105:7-21). In the adult retina, IRBP appears to mediate the transport of hydrophobic molecules, particularly retinoids and fatty acids, within the hydrophilic extracellular domain. In this paper, we compare the distribution of IRBP and its mRNA in adult and embryonic Xenopus retina. Xenopus IRBP antisense RNA, labeled with tritium or digoxigenin, was used for in situ hybridizaton studies. For immunohistochemistry, we used an antiserum against Xenopus IRBP expressed in Escherichia coli. In the adult, we found that IRBP is synthesized at similar levels by both rods and cones. The protein is restricted to the interphotoreceptor matrix, with lesser amounts in the pigment epithelial cytoplasm. In the embryo, expression of the mRNA for IRBP is restricted to the central retina, where photoreceptor differentiation has taken place. By contrast, the protein is distributed throughout the embryonic subretinal space. Therefore, the presence of IRBP precedes photoreceptor differentiation. In summary, IRBP is synthesized by both rods and cones and may be internalized by the pigment epithelium. In the embryo, IRBP is synthesized by the central retina and diffuses through the matrix, reaching the undifferentiated peripheral retina. In view of its ligand-binding properties, diffusion of IRBP may provide the peripheral neural retina with a vehicle to transport retinoids and docosahexaenoic acid (molecules critical to normal retinal development) from the pigment epithelium.