RPE and Stem Cell Therapy

Retinal pigment epithelium (RPE) is vitally important for supporting photoreceptor functions and welfare. RPE degeneration has a major role in pathogenesis of many retinal diseases including wet and dry forms of age-related macular degeneration (AMD). The loss of RPE cell functions leads to the degradation of photoreceptors and as a consequence to either partial or total loss of vision. Today, only cell replacement can restore RPE functionality, setting high demands for development of cell transplantation therapy. Transplantation of RPE cells derived from fetal, cadaveric, and stem cell sources have been extensively studied in different animal models and also in recent clinical trials. Based on current knowledge, human pluripotent stem cells (hPSC), including human embryonic stem cells (hESC) and human induced pluripotent stem cells (hiPSC), provide an exhaustless source of cells for cell-based therapies. Since 2004, numerous research groups have reported successful differentiation of functional RPE cells from hPSCs (hPSC-RPE) using a wide variety of methods. Two RPE cell transplantation strategies—each with their own pros and cons—are currently under development: injection of a single-cell suspension, and transplantation of intact RPE sheet with or without a biomaterial-based scaffold. So far, the ongoing clinical trials with hPSC-RPE have not raised any safety concerns, but additional proof of efficacy needs further trials. In light of the recent advances and the exponential activity in the field, this should be possible in the near future.