A microfabricated scaffold for retinal progenitor cell grafting

Abstract

Diseases that cause photoreceptor cell degeneration afflict millions of people, yet no restorative treatment exists for these blinding disorders. Replacement of photoreceptors using retinal progenitor cells (RPCs) represents a promising therapy for the treatment of retinal degeneration. Previous studies have demonstrated the ability of polymer scaffolds to increase significantly both the survival and differentiation of RPCs. We report the microfabrication of a poly(glycerol-sebacate) scaffold with superior mechanical properties for the delivery of RPCs to the subretinal space. Using a replica molding technique, a porous poly(glycerol-sebacate) scaffold with a thickness of 45 microm was fabricated. Evaluation of the mechanical properties of this scaffold showed that the Young's modulus is about 5-fold lower and the maximum elongation at failure is about 10-fold higher than the previously reported RPC scaffolds. RPCs strongly adhered to the poly(glycerol-sebacate) scaffold, and endogenous fluorescence nearly doubled over a 2-day period before leveling off after 3 days. Immunohistochemistry revealed that cells grown on the scaffold for 7 days expressed a mixture of immature and mature markers, suggesting a tendency towards differentiation. We conclude that microfabricated poly(glycerol-sebacate) exhibits a number of novel properties for use as a scaffold for RPC delivery.

Selective Removal of Photoreceptor CellsIn VivoUsing the Biodegradable Elastomer Poly(Glycerol Sebacate)

“…Since we previously developed a method for microfabricating a porous PGS membrane for subretinal implantation, 10 future studies will seek to determine if the addition of low amounts of porosity to the PGS membrane can control the rate of photoreceptor degeneration and if changing the rate of degeneration provides any benefits for this procedure. As described above, subretinal gliosis is not desirable, and we also noted one instance of mechanical noncompliance during this study resulting in RPE and choroidal damage.…”

“…The sucrose-coated PDMS was immediately baked at 1308C in an oven for 10 min and then transferred to a 1208C hotplate. Approximately 6.5 g of molten PGS (1508C) (prepared as previously described 6,10 ) was spin coated at 3000 rpm for 30 s on the sucrose-coated PDMS slab. The PGS on the PDMS slab was cured at 1208C under a vacuum of 15 millitorr for 48 h. Subsequently, the mold was submerged in ddH 2 O for 16 days to loosen the PGS from the PDMS slab.…”

“…7 Recent studies demonstrate the in vitro biocompatibility of PGS with 3T3 human fibroblasts, baboon primary endothelial progenitor cells and smooth muscle cells, rat Schwann cells, and mouse retinal progenitor cells. 6,[8][9][10] Additionally, in vivo studies have shown that PGS causes less inflammation and fibrosis than poly(lactide-co-glycolide), a well-studied and widely used biomaterial, and in contrast to poly(lactide-co-glycolide), PGS does not induce a foreign body giant cell response. 6,9 Several studies report the fabrication of PGS into structures for supporting tissue growth using methods such as salt leaching 11 and microfabrication.…”

“…6,9 Several studies report the fabrication of PGS into structures for supporting tissue growth using methods such as salt leaching 11 and microfabrication. 10,12,13 We recently reported the microfabrication of a thin porous PGS membrane for use as a scaffold in retinal tissue engineering, specifically for photoreceptor replacement using retinal progenitor cells. 10 The microfabrication method allows precise customization of the size, shape, and density of the pores in the scaffold, and the pores were included in the design of the scaffold specifically to allow nutrients to flow from the RPE to the photoreceptor layer.…”

“…10,12,13 We recently reported the microfabrication of a thin porous PGS membrane for use as a scaffold in retinal tissue engineering, specifically for photoreceptor replacement using retinal progenitor cells. 10 The microfabrication method allows precise customization of the size, shape, and density of the pores in the scaffold, and the pores were included in the design of the scaffold specifically to allow nutrients to flow from the RPE to the photoreceptor layer. For the present study, we reasoned that a similarly fabricated PGS membrane lacking pores would serve to block the flow of nutrients to the photoreceptor layer and thus cause selective removal of the photoreceptor layer.…”