Current design and advances of hydrogel for retinal tissue engineering and regenerative medicine

The field of tissue engineering and regenerative medicine (TERM) possesses the possibility for the treatment of degenerative retinal disease such as age-related macular degeneration. Previously, the damaged or diseased retina was treated by delivering cells, genes, drugs, and biological substances in the anterior segment or the posterior ocular. However, these methods fail to fully regenerate the degenerative retinal tissue to mature functional retinal tissue. To overcome these limitations, the application of hydrogel for retinal TERM was studied for over 10 years and showed the potential for successful retinal regeneration. Hydrogels have shown attractive properties as retinal tissue engineering (RTE) scaffolds. Their ability to maintain a fully hydrated three-dimensional structure provides a similar environment to the native extracellular matrix (ECM). The viscoelastic property of the hydrogel allows the noninvasive injection to the target tissue. Also, the mechanical support allows the encapsulation of cells and drugs. Taking these advantages, efforts are continuously being performed to discover the most suitable biomaterial for RTE. This review outlines a brief description of retina structure, retinal disease, and the application of hydrogels for RTE. Furthermore, challenges and outlooks of hydrogel-based RTE are discussed.