Ultrathin micromolded 3D scaffolds for high-density photoreceptor layer reconstruction

Abstract

Polymeric scaffolds are revolutionizing therapeutics for blinding disorders affecting the outer retina, a region anatomically and functionally defined by light-sensitive photoreceptors. Recent engineering advances have produced planar scaffolds optimized for retinal pigment epithelium monolayer delivery, which are being tested in early-stage clinical trials. We previously described a three-dimensional scaffold supporting a polarized photoreceptor monolayer, but photoreceptor somata typically occupy multiple densely packed strata to maximize light detection. Thus, patients with severe photoreceptor degeneration are expected to extract greater benefits from higher-density photoreceptor delivery. Here, we describe the microfabrication of a biodegradable scaffold patterned for high-density photoreceptor replacement. The “ice cube tray” structure optimizes mechanical properties and cell-to-biomaterial load, enabling production of a multicellular photoreceptor layer designed for outer retinal reconstruction. Our approach may also be useful in the production of a multitude of micro- and nanoscale structures for multilayered cell delivery in other tissues.

Retinal Cell Transplantation, Biomaterials, and In Vitro Models for Developing Next-generation Therapies of Age-related Macular Degeneration

“…A recent study described a flexible, ultrathin scaffold that shows great promise. 16 Biodegradable poly(glycerol-sebacate) was engineered to form a thin sheet with an array of pores to orient inner and outer segments. A chamber was added above the array for seeding photoreceptor precursors isolated from stage-2 retinal organoids ( Fig.…”

“…Scaffolds can organize the orientation of photoreceptor cells and ensure close juxtaposition of RPE and with photoreceptors. 15 , 16 Ideal scaffolds should provide a microenvironment that promotes (1) attachment, (2) survival, and (3) directed differentiation of RPE and/or retinal progenitor cells (RPC). For subretinal implantation, scaffolds must be nontoxic.…”

Outer Retinal Cell Replacement: Putting the Pieces Together

“…Current hPSC approaches include two-photon polymerized PCL scaffolds seeded with clinical-grade RPCs 191 , 196 and micromolded PGS scaffolds seeded with hPSC-PRPs. 192 , 193 Both scaffolds are sterilizable, biodegradable, and have a desirable elastic and/or compressive modulus, which play a critical role in ease of surgical handling. 193 , 196 , 197 Extensive in vivo safety testing has been performed for the former, although the use of RPCs rather than PRPs was a limiting factor in determining capacity for PR delivery.…”

“… 192 , 193 Both scaffolds are sterilizable, biodegradable, and have a desirable elastic and/or compressive modulus, which play a critical role in ease of surgical handling. 193 , 196 , 197 Extensive in vivo safety testing has been performed for the former, although the use of RPCs rather than PRPs was a limiting factor in determining capacity for PR delivery. Micromolded scaffolds are capable of pre-organizing polarized PRPs even at high cell densities, although it remains to be seen whether such organization can be retained in vivo.…”

Inducible Pluripotent Stem Cells to Model and Treat Inherited Degenerative Diseases of the Outer Retina: 3D-Organoids Limitations and Bioengineering Solutions

“…This “wine glass” model was originally designed as a reproducible in vitro platform for scalable monolayer model of photoreceptor diseases. This 3D microstructured scaffold design has been recently upgraded by improving the microfabrication technology to reduce wall thickness and increase the number of cells loaded for each well and better mimic the multilayer ONL structure with densely packed cells [ 297 ]. This “ice cube” model may better approximate the 3D ONL structure with higher cell numbers for unit volume than the “wine glass” model design and may represent a model for cell replacement approaches meeting the constrain of high seeding density, minimal saline volume, and improved control over cell positioning in the SRS outlined above.…”