Approaches to cell delivery: substrates and scaffolds for cell therapy.

Retinal degeneration, associated with loss of photoreceptors, is the primary cause of permanent vision impairment, impacting millions of people worldwide. Age-related macular degeneration and retinitis pigmentosa are two common retinal diseases resulting in photoreceptor loss and vision impairment or blindness. Presently, available treatments can only delay the progress of retinal degeneration, and there are no treatments that can restore permanent vision loss. Research is underway to develop methods of regenerating the impaired retina by delivering photoreceptor precursor cells and retinal pigment epithelium to the subretinal space. Challenges to cell transplantation include limited survival upon implantation and the formation of abnormal cell architectures in vivo. Retinal tissue engineering shows immense promise and potential in treatment of retinal degeneration by employing scaffold-based delivery systems of retinal progenitor cells to the subretinal space. Scaffold delivery strategy has been shown to enhance the cell survival and direct cell differentiation in a variety of retinal degenerative models. In this chapter, we summarize the research findings on different scaffold- or substrate-based transplantation techniques used to deliver retinal progenitor/photoreceptor precursors and retinal pigment epithelial cells to the subretinal space.