Comparative proteomic analysis of human embryonic stem cell-derived and primary human retinal pigment epithelium (original) (raw)

Human embryonic stem cell-derived retinal pigment epithelial cells (hESC-RPE) provide an unlimited cell source for retinal cell replacement therapies. Clinical trials using hESC-RPE to treat diseases such as age-related macular degeneration (AMD) are currently underway. Human ESC-RPE cells have been thoroughly characterized at the gene level but their protein expression profile has not been studied at larger scale. In this study, proteomic analysis was used to compare hESC-RPE cells differentiated from two independent hESC lines, to primary human RPE (hRPE) using Isobaric tags for relative quantitation (iTRAQ). 1041 common proteins were present in both hESC-RPE cells and native hRPE with majority of the proteins similarly regulated. The hESC-RPE proteome reflected that of normal hRPE with a large number of metabolic, mitochondrial, cytoskeletal, and transport proteins expressed. No signs of increased stress, apoptosis, immune response, proliferation, or retinal degeneration related changes were noted in hESC-RPE, while important RPE specific proteins involved in key RPE functions such as visual cycle and phagocytosis, could be detected in the hESC-RPE. Overall, the results indicated that the proteome of the hESC-RPE cells closely resembled that of their native counterparts. The retinal pigment epithelium (RPE) is a multifunctional, polarized epithelial cell layer between the neurosensory retina and the choroid, which plays key roles in photoreceptor function and vision. The RPE cells transport nutrients, waste products, ions and fluid between the choroidal blood supply and the subretinal space. RPE also phagocytizes shed photoreceptor outer segments (POS), absorbs scattered light, secretes many important signalling molecules and functions in the retinoid visual cycle 1. This highly metabolically active cell type is exposed to constant light stimuli and high oxidative stress making it vulnerable to oxidative damage. Thus, abnormalities in RPE cell function may lead to retinal degeneration and photoreceptor cell death. The RPE is the focal point of many retinal degenerative diseases such as age-related macular degeneration (AMD), the most common cause of blindness in the elderly in western countries. AMD is a multifactorial, age-associated disease characterized by accumulation of insoluble drusen in the retina, degeneration of RPE and photoreceptors in the dry form, and choroidal neovascularization in the exudative, wet form of the disease 2. Treatment options for the retinal degenerative diseases such as AMD are currently very limited and mostly only delay disease progression. Cellular transplantation to replace the affected RPE is considered as a promising therapeutic strategy to treat these diseases. Macular translocation and autologous RPE transplantation with peripheral RPE have demonstrated the feasibility and effectiveness of autologous RPE cell replacement therapy in AMD patients, but these surgical procedures carry significant complications 3. Many cell types have been tested as a source for RPE transplantation tissue including foetal RPE 4 and RPE cell lines 5, 6. Issues related to scarce tissue