Single-cell-pore-sized 3D printed scaffolds for retinal pigment epithelial cell therapy

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.