A Co-culture Model for Determining the Target Specificity of the de novo Generated Retinal Ganglion Cells

Reproducible generation of human retinal ganglion cells from banked retinal progenitor cells: analysis of target recognition and IGF-1-mediated axon regeneration

The selective degeneration of retinal ganglion cells (RGCs) is a common feature in glaucoma, a complex group of diseases, leading to irreversible vision loss. Stem cell-based glaucoma disease modeling, cell replacement, and axon regeneration are viable approaches to understand mechanisms underlying glaucomatous degeneration for neuroprotection, ex vivo stem cell therapy, and therapeutic regeneration. These approaches require direct and facile generation of human RGCs (hRGCs) from pluripotent stem cells. Here, we demonstrate a method for rapid generation of hRGCs from banked human pluripotent stem cell-derived retinal progenitor cells (hRPCs) by recapitulating the developmental mechanism. The resulting hRGCs are stable, functional, and transplantable and have the potential for target recognition, demonstrating their suitability for both ex vivo stem cell approaches to glaucomatous degeneration and disease modeling. Additionally, we demonstrate that hRGCs derived from banked hRPCs are capable of regenerating their axons through an evolutionarily conserved mechanism involving insulin-like growth factor 1 and the mTOR axis, demonstrating their potential to identify and characterize the underlying mechanism(s) that can be targeted for therapeutic regeneration.

Multi-lineage Human iPSC-Derived Platforms for Disease Modeling and Drug Discovery

Human induced pluripotent stem cells (hiPSCs) provide a powerful platform for disease modeling and have unlocked new possibilities for understanding the mechanisms governing human biology, physiology, and genetics. However, hiPSC-derivatives have traditionally been utilized in two-dimensional monocultures, in contrast to the multi-systemic interactions that influence cells in the body. We will discuss recent advances in generating more complex hiPSC-based systems using three-dimensional organoids, tissue-engineering, microfluidic organ-chips, and humanized animal systems. While hiPSC differentiation still requires optimization, these next-generation multi-lineage technologies can augment the biomedical researcher's toolkit and enable more realistic models of human tissue function.

Advances in the Differentiation of Retinal Ganglion Cells from Human Pluripotent Stem Cells

Human pluripotent stem cell (hPSC) technology has revolutionized the field of biology through the unprecedented ability to study the differentiation of human cells in vitro. In the past decade, hPSCs have been applied to study development, model disease, develop drugs, and devise cell replacement therapies for numerous biological systems. Of particular interest is the application of this technology to study and treat optic neuropathies such as glaucoma. Retinal ganglion cells (RGCs) are the primary cell type affected in these diseases, and once lost, they are unable to regenerate in adulthood. This necessitates the development of strategies to study the mechanisms of degeneration as well as develop translational therapeutic approaches to treat early- and late-stage disease progression. Numerous protocols have been established to derive RGCs from hPSCs, with the ability to generate large populations of human RGCs for translational applications. In this review, the key applications of hPSCs within the retinal field are described, including the use of these cells as developmental models, disease models, drug development, and finally, cell replacement therapies. In greater detail, the current report focuses on the differentiation of hPSC-derived RGCs and the many unique characteristics associated with these cells in vitro including their genetic identifiers, their electrophysiological activity, and their morphological maturation. Also described is the current progress in the use of patient-specific hPSCs to study optic neuropathies affecting RGCs, with emphasis on the use of these RGCs for studying disease mechanisms and pathogenesis, drug screening, and cell replacement therapies in future studies.

Astrocytes Regulate the Development and Maturation of Retinal Ganglion Cells Derived from Human Pluripotent Stem Cells

Retinal ganglion cells (RGCs) form the connection between the eye and the brain, with this connectivity disrupted in numerous blinding disorders. Previous studies have demonstrated the ability to derive RGCs from human pluripotent stem cells (hPSCs); however, these cells exhibited some characteristics that indicated a limited state of maturation. Among the many factors known to influence RGC development in the retina, astrocytes are known to play a significant role in their functional maturation. Thus, efforts of the current study examined the functional maturation of hPSC-derived RGCs, including the ability of astrocytes to modulate this developmental timeline. Morphological and functional properties of RGCs were found to increase over time, with astrocytes significantly accelerating the functional maturation of hPSC-derived RGCs. The results of this study clearly demonstrate the functional and morphological maturation of RGCs in vitro, including the effects of astrocytes on the maturation of hPSC-derived RGCs.

iDrugs and iDevices Discovery Research: Preclinical Assays, Techniques, and Animal Model Studies for Ocular Hypotensives and Neuroprotectants

Discovery ophthalmic research is centered around delineating the molecular and cellular basis of ocular diseases and finding and exploiting molecular and genetic pathways associated with them. From such studies it is possible to determine suitable intervention points to address the disease process and hopefully to discover therapeutics to treat them. An investigational new drug (IND) filing for a new small-molecule drug, peptide, antibody, genetic treatment, or a device with global health authorities requires a number of preclinical studies to provide necessary safety and efficacy data. Specific regulatory elements needed for such IND-enabling studies are beyond the scope of this article. However, to enhance the overall data packages for such entities and permit high-quality foundation-building publications for medical affairs, additional research and development studies are always desirable. This review aims to provide examples of some target localization/verification, ocular drug discovery processes, and mechanistic and portfolio-enhancing exploratory investigations for candidate drugs and devices for the treatment of ocular hypertension and glaucomatous optic neuropathy (neurodegeneration of retinal ganglion cells and their axons). Examples of compound screening assays, use of various technologies and techniques, deployment of animal models, and data obtained from such studies are also presented.