Expression of pigment epithelium-derived factor and thrombospondin-1 regulate proliferation and migration of retinal pigment epithelial cells

Abstract

Age‐related macular degeneration (AMD) is the leading cause of vision loss among elderly. Although the pathogenesis of AMD is associated with retinal pigmented epithelium (RPE) dysfunction and abnormal neovascularization the detailed mechanisms remain unresolved. RPE is a specialized monolayer of epithelial cells with important functions in ocular homeostasis. Pathological RPE damage contributes to major ocular conditions including retinal degeneration and irreversible loss of vision in AMD. RPE cells also assist in the maintenance of the ocular angiogenic balance by production of positive and negative regulatory factors including vascular endothelial growth factor (VEGF), thrombospondin‐1 (TSP1), and pigment epithelium‐derived factor (PEDF). The altered production of PEDF and TSP1, as endogenous inhibitors of angiogenesis and inflammation, by RPE cells have been linked to pathogenesis of AMD and choroidal and retinal neovascularization. However, lack of simple methods for isolation and culture of mouse RPE cells has resulted in limited knowledge regarding the cell autonomous role of TSP1 and PEDF in RPE cell function. Here, we describe a method for routine isolation and propagation of RPE cells from wild‐type, TSP1, and PEDF‐deficient mice, and have investigated their impact on RPE cell function. We showed that expression of TSP1 and PEDF significantly impacted RPE cell proliferation, migration, adhesion, oxidative state, and phagocytic activity with minimal effect on their basal rate of apoptosis. Together, our results indicated that the expression of PEDF and TSP1 by RPE cells play crucial roles not only in regulation of ocular vascular homeostasis but also have significant impact on their cellular function.

Alteration in cellular turnover and progenitor cell population in lacrimal glands from thrombospondin 1 −/− mice, a model of dry eye

“…These results are in contrast to results obtained in lung endothelial cells and retinal pigment epithelial cells in which cell proliferation was increased in TSP1 −/− and CD47 −/− mice (Farnoodian et al, 2015; Kaur et al, 2013). Thus the effects of TSP1 appear to be tissue specific.…”

Negative regulators of angiogenesis: important targets for treatment of exudative AMD

“…PEDF inhibits apoptosis induced by oxidative stress in retinal pericytes preventing their dysfunction [102]. We showed elevated oxidative stress levels in the Serpinf1 −/− RPE cells [73] and choroidal and retinal EC (Our unpublished data). Cao and associates showed that pretreatment of retinal cultures with PEDF inhibited mitochondrial signal transduction and induced apoptosis when challenged with H 2 O 2 [82].…”

“…Furthermore, the expression of TSP2 was increased in Thbs1 -deficient ChEC [50]. RPE cells also expressed a low amount of TSP2, which was increased in Thbs1 -deficient RPE cells [73]. However, the cell autonomous impact of TSP2 expression on choroidal EC and RPE cell functions remain a subject of future investigation.…”

“…PEDF also participates in the RPE cell differentiation and maturation [97]. We recently showed that PEDF deficiency greatly affected RPE cell proliferation, migration, adhesion, oxidative state, and phagocytic activity with minimal effect on their basal rate of apoptosis [73]. Altered migration of RPE cells in the absence of PEDF supports its significant contribution in RPE cell degeneration and the pathogenesis of AMD.…”

“…We reported that PEDF deficiency results in enhanced accumulation of phagocytized materials inside RPE cells. This was associated with impaired proteasome activity of Serpinf1 −/− RPE cells, including decreased caspase-like and trypsin-like activity [73]. Oxidative stress is identified as a crucial factor in the progression of AMD pathogenesis.…”