(632f) Controlled Micro- and Nano-Structure of Stem Cell Scaffolds for Photoreceptor Regeneration

The degeneration of photoreceptors, as manifested in both retinitis pigmentosa (RP) and age-related macular degeneration (AMD), is one of the leading causes of blindness in the western world. Although stem cell injection to the sub-retinal space has been shown to restore function to retinas with early-stage degeneration, this success does not translate to advanced disease states. Injected cells are not retained in the sub-retinal space, are less than 0.01% viable post-injection, do not integrate with the existing retinal tissue, and overall lack the support necessary for restoring retinal function. Stem cell scaffolds offer a solution to this lack of support, but the materials’ physical properties, namely structure, play a major role in their success in this regard. The goal of this project is to provide support to differentiating replacement cells using an injectable stem cell scaffold with controlled micro- and nano-structure.

Micro- and nano-porous cell scaffolds were synthesized by direct and lyotropic liquid crystalline (LLC) templating, respectively, of photopolymerizable pre-polymers. Micro-fabrication methods such as PDMS templating and spin-coating were used to control micron-scaled physical features such as pore size, while surfactant (LLC) choice and concentration were used to control nano-scaled physical features. These physical features were characterized using scanning electron microscopy (SEM), small-angle x-ray scattering (SAXS), and polarized light microscopy (PLM). To test the effects of the varying physical features, the scaffolds were seeded with murine induced pluripotent stem (MiPS) cells, which were allowed to differentiate for various amounts of time. Cell growth and differentiation were characterized using SEM and immunohistochemistry.

Pore size and spacing influenced stem cell growth and differentiation. The presence of nanostructure, introduced via lyotropic liquid crystalline templating, improved the diffusion properties of the material and thus influenced the growth and differentiation of cells as well. The optimized materials produced were shown to support the differentiation of induced pluripotent stem cells to mature retinal cell types.

The ability to control the structure of stem cell scaffolds on both the micron and sub-micron levels is crucial for their development as transplantable supports for photoreceptor regeneration. This work shows that physical properties of photopolymers can be successfully manipulated to meet the needs of photoreceptor regeneration applications. An optimized material of this kind; one that is biocompatible, implantable, and able to encourage growth and differentiation of mature retinal cell types, could lead to the successful transplantation of replacement cells and ultimately, restoration of retinal function in patients who suffer from retinal degeneration.