Abstract
Inflammation is involved in the pathogenesis of several age-related ocular diseases, such as macular degeneration (AMD), diabetic retinopathy, and glaucoma. The delivery of anti-inflammatory siRNA to the retinal pigment epithelium (RPE) may become a promising therapeutic option for the treatment of inflammation, if the efficient delivery of siRNA to target cells is accomplished. Unfortunately, so far, the siRNA delivery system selection performed in dividing RPE cells in vitro has been a poor predictor of the in vivo efficacy. Our study evaluates the silencing efficiency of polyplexes, lipoplexes, and lipidoid-siRNA complexes in dividing RPE cells as well as in physiologically relevant RPE cell models. We find that RPE cell differentiation alters their endocytic activity and causes a decrease in the uptake of siRNA complexes. In addition, we determine that melanosomal sequestration is another significant and previously unexplored barrier to gene silencing in pigmented cells. In summary, this study highlights the importance of choosing a physiologically relevant RPE cell model for the selection of siRNA delivery systems. Such cell models are expected to enable the identification of carriers with a high probability of success in vivo, and thus propel the development of siRNA therapeutics for ocular disease.
Highlights
Age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma are common age-related eye conditions and major causes of visual impairment and blindness
This study examines the suitability of a polymer carrier (poly(benzyl-l-glutamate) and poly-llysine), a lipid carrier (1,2-Dioleoyl-3-trimethylammoniumpropane (DOTAP), 1,2-dioleoyl-sn-glycero-3phosphoethanolamine (DOPE), and protamine sulfate (PS) liposomes), a lipidoid carrier (1,2-distearoylsn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-2000] (DSPE-PEG), cholesterol, lipidoid), and a few commercial carriers as small interfering RNA (siRNA) delivery vehicles
Gene silencing in the retinal pigment epithelium (RPE) requires a carrier that can successfully deliver the siRNA to a quiescent, terminally differentiated cell monolayer. siRNA therapeutics must first of all gain access into cells, a process which occurs via endocytosis and whose mechanisms have been widely studied
Summary
Age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma are common age-related eye conditions and major causes of visual impairment and blindness. AMD is triggered by the degeneration of the retinal pigment epithelium (RPE), a highly specialized monolayer of pigmented, terminally differentiated, post-mitotic cells joined apically with tight junctions that form the outer blood-retina barrier (BRB) [13]. This barrier regulates the traffic of cells and molecules between the blood and the neural retina, and it plays a crucial role in maintaining the viability of the retina. A therapeutic strategy that silences the proinflammatory genes in the RPE may alleviate the inflammation and restore retinal homeostasis
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