Hybrid vitronectin-mimicking polycaprolactone scaffolds for human retinal progenitor cell differentiation and transplantation.

Many advances have been made in an attempt to treat retinal degenerative diseases, such as age-related macular degeneration and retinitis pigmentosa. The irreversible loss of photoreceptors is common to both, and currently no restorative clinical treatment exists. It has been shown that retinal progenitor and photoreceptor precursor cell transplantation can rescue the retinal structure and function. Importantly, retinal progenitor cells can be collected from the developing neural retina with further expansion and additional modification in vitro, and the delivery into the degenerative host can be performed as a single-cell suspension injection or as a complex graft transplantation. Previously, we have described several polymer scaffolds for culture and transplantation of retinal progenitor cells of both mouse and human origin. This tissue engineering strategy increases donor cell survival and integration. We have also shown that biodegradable poly(ɛ-caprolactone) induces mature photoreceptor differentiation from human retinal progenitor cells. However, poor adhesive properties limit its use, and therefore it requires additional surface modification. The aim of this work was to study vitronectin-mimicking oligopeptides (Synthemax II-SC) poly(ɛ-caprolactone) films and their effects on human retinal progenitor cell adhesion, proliferation, and differentiation. Here, we show that the incorporation of vitronectin-mimicking oligopeptide into poly(ɛ-caprolactone) leads to dose-dependent increases in cell adhesion; the optimum dose identified as 30 µg/ml. Inhibition of human retinal progenitor cells proliferation was seen on poly(ɛ-caprolactone) and was maintained with the hybrid scaffold. This has been shown to be beneficial for driving cell differentiation. Additionally, we observed equal expression of Nrl, rhodopsin, recoverin, and rod outer membrane 1 after differentiation on the hybrid scaffold as compared to the standard fibronectin coating of poly(ɛ-caprolactone). After transplantation into rd1 retina degenerative mice, human retinal progenitor cells were able to migrate to the outer nuclear layer and survive for three weeks. We conclude that Synthemax II-SC can be incorporated into poly(ɛ-caprolactone) to create a hybrid chemically defined scaffold for clinical application.