Investigations of RPE Cells of Choriodal Neovascular Membranes from Patients with Age-Related Macula Degeneration

Defined Medium Conditions for the Induction and Expansion of Human Pluripotent Stem Cell-Derived Retinal Pigment Epithelium

We demonstrate that a combination of Noggin, Dickkopf-1, Insulin Growth Factor 1 and basic Fibroblast Growth Factor, promotes the differentiation of human pluripotent stem cells into retinal pigment epithelium (RPE) cells. We describe an efficient one-step approach that allows the generation of RPE cells from both human embryonic stem cells and human induced pluripotent stem cells within 40-60 days without the need for manual excision, floating aggregates or imbedded cysts. Compared to methods that rely on spontaneous differentiation, our protocol results in faster differentiation into RPE cells. This pro-retinal culture medium promotes the growth of functional RPE cells that exhibit key characteristics of the RPE including pigmentation, polygonal morphology, expression of mature RPE markers, electrophysiological membrane potential and the ability to phagocytose photoreceptor outer segments. This protocol can be adapted for feeder, feeder-free and serum-free conditions. This method thereby provides a rapid and simplified production of RPE cells for downstream applications such as disease modelling and drug screening.

Ion Channels in the Eye: Involvement in Ocular Pathologies

The eye is the sensory organ of vision. There, the retina transforms photons into electrical signals that are sent to higher brain areas to produce visual sensations. In the light path to the retina, different types of cells and tissues are involved in maintaining the transparency of avascular structures like the cornea or lens, while others, like the retinal pigment epithelium, have a critical role in the maintenance of photoreceptor function by regenerating the visual pigment. Here, we have reviewed the roles of different ion channels expressed in ocular tissues (cornea, conjunctiva and neurons innervating the ocular surface, lens, retina, retinal pigment epithelium, and the inflow and outflow systems of the aqueous humor) that are involved in ocular disease pathophysiologies and those whose deletion or pharmacological modulation leads to specific diseases of the eye. These include pathologies such as retinitis pigmentosa, macular degeneration, achromatopsia, glaucoma, cataracts, dry eye, or keratoconjunctivitis among others. Several disease-associated ion channels are potential targets for pharmacological intervention or other therapeutic approaches, thus highlighting the importance of these channels in ocular physiology and pathophysiology.

Combinatory inhibition of VEGF and FGF2 is superior to solitary VEGF inhibition in an in vitro model of RPE-induced angiogenesis

BACKGROUND

Choroidal neovascularisation (CNV) as a feature of exudative age-related macular degeneration (AMD) is partially regulated by retinal pigment epithelium (RPE). In this study, the effect of combinatory anti-angiogenic treatment was evaluated using a novel in vitro assay of RPE-induced angiogenesis.

METHODS

RPE isolated from surgically excised CNV-membranes (CNV-RPE) was used to stimulate sprouting of endothelial cell (EC) spheroids in a 3D collagen matrix. The anti-angiogenic effect of solitary anti-VEGF antibodies (bevacizumab) was compared to a combinatory treatment with anti-VEGF and anti-FGF2 antibodies.

RESULTS

Anti-VEGF treatment inactivated all RPE-derived VEGF but was unable to fully inhibit EC sprouting induced by CNV-RPE. Combined anti-VEGF/anti-FGF treatment inactivated both growth factors and reduced EC sprouting significantly.

CONCLUSIONS

RPE from CNV patients expresses angiogenic growth factors that act in part independently of VEGF. Targeted combinatory therapy can be superior to solitary anti-VEGF therapy. One possible candidate for combinatory therapy is FGF2.

Rapamycin reduces VEGF expression in retinal pigment epithelium (RPE) and inhibits RPE-induced sprouting angiogenesis in vitro

Anti-VEGF treatment has become accepted first-line treatment for choroidal neovascularisation (CNV) in age-related macular degeneration. However, VEGF-inhibition does not always lead to sustained CNV-reduction. In this study, the effect of rapamycin was superior to VEGF-inhibition in a co-culture assay of endothelial cells (ECs) and retinal pigment epithelium (RPE). Rapamycin reduced EC sprouting in groups that did not respond to anti-VEGF treatment. Rapamycin did not induce EC apoptosis, but reduced both VEGF-production in RPE and the responsiveness of ECs to stimulation. Rapamycin might therefore be a therapeutic option for CNV patients that do not respond sufficiently to the established anti-VEGF treatments.