Retinal pigment epithelial (RPE) cell dysfunction is a key driving force of AMD. RPE cells form a metabolic interface between photoreceptors and choriocapillaris, performing essential functions for retinal homeostasis. Through their multiple functions, RPE cells are constantly exposed to oxidative stress, which leads to the accumulation of damaged proteins, lipids, nucleic acids, and cellular organelles, including mitochondria. As miniature chemical engines of the cell, self-replicating mitochondria are heavily implicated in the aging process through a variety of mechanisms. In the eye, mitochondrial dysfunction is strongly associated with several diseases, including age-related macular degeneration (AMD), which is a leading cause of irreversible vision loss in millions of people globally. Aged mitochondria exhibit decreased rates of oxidative phosphorylation, increased reactive oxygen species (ROS) generation, and increased numbers of mitochondrial DNA mutations. Mitochondrial bioenergetics and autophagy decline during aging because of insufficient free radical scavenger systems, the impairment of DNA repair mechanisms, and reductions in mitochondrial turnover. Recent research has uncovered a much more complex role of mitochondrial function and cytosolic protein translation and proteostasis in AMD pathogenesis. The coupling of autophagy and mitochondrial apoptosis modulates the proteostasis and aging processes. This review aims to summarise and provide a perspective on (i) the current evidence of autophagy, proteostasis, and mitochondrial dysfunction in dry AMD; (ii) current in vitro and in vivo disease models relevant to assessing mitochondrial dysfunction in AMD, and their utility in drug screening; and (iii) ongoing clinical trials targeting mitochondrial dysfunction for AMD therapeutics.

Transplantation of stem cell–derived retinal pigment epithelial (RPE) cells is considered a viable therapeutic option for age-related macular degeneration (AMD). Several landmark Phase I/II clinical trials have demonstrated safety and tolerability of RPE transplants in AMD patients, albeit with limited efficacy. Currently, there is limited understanding of how the recipient retina regulates the survival, maturation, and fate specification of transplanted RPE cells. To address this, we transplanted stem cell–derived RPE into the subretinal space of immunocompetent rabbits for 1 mo and conducted single-cell RNA sequencing analyses on the explanted RPE monolayers, compared to their age-matched in vitro counterparts. We observed an unequivocal retention of RPE identity, and a trajectory-inferred survival of all in vitro RPE populations after transplantation. Furthermore, there was a unidirectional maturation toward the native adult human RPE state in all transplanted RPE, regardless of stem cell resource. Gene regulatory network analysis suggests that tripartite transcription factors ( FOS , JUND , and MAFF ) may be specifically activated in posttransplanted RPE cells, to regulate canonical RPE signature gene expression crucial for supporting host photoreceptor function, and to regulate prosurvival genes required for transplanted RPE’s adaptation to the host subretinal microenvironment. These findings shed insights into the transcriptional landscape of RPE cells after subretinal transplantation, with important implications for cell-based therapy for AMD.

Cell therapy is one of the most promising methods to treat retinal degenerative diseases, and crucial to its success is optimizing biomaterials to facilitate the delivery of retinal pigment epithelial (RPE) cells. This study explores the application of single-cell-pore-sized 3D printed polycaprolactone (PCL) scaffolds for cultivating human embryonic stem cell-derived RPE cell sheets. It compares them with track-etched polyethylene terephthalate (PET) membranes, the commercial products used in clinical trials for RPE cell delivery. We engineered two types of scaffolds at the microscale to optimize cell culture conditions, specifically focusing on pore size and fiber spacing. Protein expression analysis demonstrated that one scaffold with a pore size of ∼10 µm facilitated superior cellular integrity and function. Functional assessments, including barrier integrity, permeability, and phagocytosis assays, indicated that this scaffold enhanced nutrient exchange and maintained effective RPE functions akin to PET membranes. In an in vivo study, color fundus, optical coherence tomography, immunohistochemistry, and electroretinography revealed that 3D printed scaffolds exhibited biocompatibility, stability, and minimal inflammatory responses in the subretinal space of porcine models for 2 months and rabbit models for 14 months, with no adverse impact on retinal structure or function over either period. The findings suggest that 3D-printed biodegradable scaffolds present a viable alternative for RPE cell delivery, potentially advancing therapies for retinal degenerative conditions. STATEMENT OF SIGNIFICANCE: Cell therapy shows great promise for treating eye diseases that lead to vision loss. A crucial aspect of this therapy is delivering specialized retinal pigment epithelial (RPE) cells effectively. Our research presents a 3D-printed scaffold made from polycaprolactone (PCL), designed to carry RPE cells derived from human stem cells and dissolve after placement in the eye. We tested this scaffold in rabbits and pigs to evaluate its surgical handling, cell delivery effectiveness, and safety for human application. Our results refine implant design, paving the way for safer and more effective treatments for retinal diseases. Overall, this research enhances the application of cell therapy with scaffolds and offers valuable insights for future medical practices.

The retinal pigment epithelium (RPE) is essential for the health and function of the retina and, more specifically, the photoreceptors. Hence, the dysfunction of RPE leads to various retinal degeneration diseases. The rising prevalence of these disorders highlights the need for effective, large-scale cell-based therapies, particularly those utilizing stem cell-derived RPE cells. This study presents the development of a biodegradable, smooth surface microcarrier designed to facilitate the expansion and maturation of RPE cells derived from induced pluripotent stem cells (iPSCs). Using a three-dimensional (3D) culture system with polycaprolactone (PCL) porous microcarriers, we demonstrate that RPE cells exhibit comparable adhesion and growth on microcarriers as they do on traditional two-dimensional (2D) culture plates. The microcarrier system facilitates efficient maturation and yields higher quantities of functional RPE cells, highlighting its potential for large-scale production to meet both clinical demands and in vitro large-scale screening studies. Moreover, RPE cells cultured on this microcarrier can be directly frozen and recovered, maintaining their phenotypic and functional integrity upon thawing. This research showcases the scalability and practicality of RPE cell production, providing a robust solution for the storage and delivery of RPE cells. While our results establish the feasibility of direct cryopreservation and recovery of monolayer RPE cells on microcarriers, the designation of a 'ready-to-use' product format is preliminary and will require expanded assessment of long-term functionality, safety, and direct translational outcomes in future studies.