Heterogeneity of Retinal Pigment Epithelial Cells from Adult Human Eye in Different Culturing Systems

The predictive capacity of in vitro preclinical models to evaluate drugs for the treatment of retinoblastoma

Retinoblastoma is a rare childhood cancer of the eye. Of the small number of drugs are used to treat retinoblastoma, all have been repurposed from drugs developed for other conditions. In order to find drugs or drug combinations better suited to the improved treatment of retinoblastoma, reliable predictive models are required, which facilitate the challenging transition from in vitro studies to clinical trials. In this review, the research performed to date on the development of 2D and 3D in vitro models for retinoblastoma is presented. Most of this research was undertaken with a view to better biological understanding of retinoblastoma, and we discuss the potential for these models to be applied to drug screening. Future research directions for streamlined drug discovery are considered and evaluated, and many promising avenues identified.

Reprogramming of Differentiated Mammalian and Human Retinal Pigment Epithelium: Current Achievements and Prospects

Abstract

Impairment of the homeostatic and functional integrity of the retina and retinal pigment epithelium (RPE) is the main cause of some degenerative diseases of the human eye, which are accompanied by loss of eyesight. Despite the significant progress made over the past decades in the development of new methods for treatment for this pathology, there are still several complications when using surgical methods for correction of eyesight and so far insurmountable limitations in the applications of modern approaches, such as gene therapy and genetic engineering. One of the promising approaches to the treatment of degenerative diseases of the retina may be an approach based on the application of regenerative capacities of its endogenous cells with high plasticity, in particular, of RPE cells and Müller glia. Currently, vertebrate RPE cells are of great interest as a source of new photoreceptors and other neurons in the degrading retina in vivo. In this regard, the possibilities of their direct reprogramming by genetic, epigenetic, and chemical methods and their combination are being investigated. This review focuses on research in gene-directed reprogramming of vertebrate RPE cells into retinal neurons, with detailed analysis of the genes used as the main reprogramming factors, comparative analysis, and extrapolation of experimental data from animals to humans. Also, this review covers studies on the application of alternative approaches to gene-directed reprogramming, such as chemical-mediated reprogramming with the use of cocktails of therapeutic low-molecular-weight compounds and microRNAs. In general, the research results indicate the complexity of the process for direct reprogramming of human RPE cells into retinal neurons. However, taking into account the results of direct reprogramming of vertebrate cells and the accessibility of human RPE cells for various vectors that deliver a variety of molecules to cells, such as transcription factors, chimeric endonucleases, recombinant proteins, and low-weight molecular compounds, the most optimal combination of factors for the successful conversion of human RPE cells to retinal neurons can be suggested.

Reprogramming of Human Retinal Pigment Epithelial Cells under the Effect of bFGF In Vitro

We studied the effect of bFGF on human retinal pigment epithelial cells in vitro In ARPE-19 cells, enhanced expression of KLF4 mRNA and reduced expression of PAX6, MITF, and OTX2 mRNA specific for retinal pigment epithelium were observed after bFGF application. The expression of KLF4 mRNA peaked in 72 h after bFGF application and then sharply decreased, which was accompanied by a 3-fold increase in TUBB3 mRNA expression (neuronal marker). Immunocytochemical analysis showed that in the presence of bFGF, some cells retained epithelial properties and showed positive staining for connexin-43, while others had long axon-like processes and demonstrated positive staining for βIII-tubulin, which attests to their neuronal transdifferentiation. Despite the prevalence of the epithelial properties, ARPE-19 cells under the influence of bFGF can show proneuronal properties.