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

Abstract

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

Plasma membrane protein polarity and trafficking in RPE cells: Past, present and future

“…PEDF in the apical direction, necessary for the maintenance of differentiated PR (Becerra et al, 2004) and VEGF in the basolateral direction, necessary for the maintenance of functional choroid capillaries (Blaauwgeers et al, 1999; Kurihara et al, 2012; Sonoda et al, 2010). …”

Comparison of the Effects between Intravitreal and Periocular Injections of Adenoviral Vectored Pigment Epithelium-Derived Factor on Suppressing Choroidal Neovascularization in Rats

“…The imbalance of expression of vascular endothelial growth factor and PEDF induced by the decrease in PEDF is one of the key factors in neovascularization formation [15]. In this paper, we study the effects of AdPEDF on inhibiting the development of CNV, and compare the effects between intravitreal and periocular injections of AdPEDF on suppressing an established CNV model in rats.…”

Regulation of MT1-MMP and MMP-2 by the Serpin PEDF: a Promising New Target for Metastatic Cancer

“…Essentially, PEDF has been determined to be the most potent endogenous angiogenic inhibitor in the body with the ability to prohibit neovascularization in the cornea, as well as endothelial cell growth, tumour proliferation and cancer metastasis [17,20]. Furthermore, PEDF has also been found to promote neuronal survival and cellular differentiation [21,22].…”

“…PEDF is a 50 kDa secreted glycoprotein which was initially localized to the human foetal retinal pigment epithelium (RPE), where it was found to be secreted and to inhibit vascular growth in that tissue [17,18,19]. Essentially, PEDF has been determined to be the most potent endogenous angiogenic inhibitor in the body with the ability to prohibit neovascularization in the cornea, as well as endothelial cell growth, tumour proliferation and cancer metastasis [17,20].…”