PLGA NPs in bovine and human RPE cells, and the efficacy of PLGA NPs to mediate gene transfer in RPE cells in vitro and in vivo in the rat

Retinal pigment epithelium (RPE) integrity and function are essential for neural retina homeostasis and play a major role in ocular diseases associated with senescence (as in age related macular degeneration) and in diseases associated with dystrophies of the photoreceptors. RPE cells therefore may serve as a potential targets for drug delivery and gene transfer aiming at arresting or reversing the processes leading to these diseases. In spite of relatively reduced transfer efficiency, nonviral gene delivery systems bypass the hazards and immune reactions associated with viral vectors [1-3]. Poly(lactic) acid (PLA), poly(glycolic) acid (PGA), and their co-polymers (PLGA) are widely used by the biomedical industry. These polymers and their derivates are evolving as interesting matrix materials to be used in drug delivery systems. They are hydrolyzed and metabolized without direct toxic reactions to living tissues [4]. Furthermore, their degradation rate can be regulated by changing their molecular weight and chemical composition, enabling modulation of the rate of delivery of encapsulated molecules within the polymeric systems [4]. DNA fragments encapsulated in PLGA microspheres can be protected from endonuclease activity [5,6]. Biodegradation and ocular tissue reaction to microparticles of PLA or PLGA have been previously studied in vitro [7,8] and in vivo [9-11]. Intravitreous injection of PLGA microspheres induced their confinement in the vitreous without the induction of any observable significant clinical inflammatory signs [11]. When injected in the subretinal space, PLA microspheres are phagocytosed by RPE cells and degraded within their cytoplasm [10]. Due to their submicron size, PLGA NPs are of greater potential therapeutic use. In addition to “protection” of the carried genetic material, they may offer an increased facility of tissue penetration and intracellular uptake. Moreover, their potential for modulated hydrolysis may allow for a slow and extended intracellular release of the encapsulated genetic material or drug [1,6]. It has been reported that PLGA NPs produce efficient transfer and sustained expression of an alkaline phosphatase gene [12,13]. In the present study, we assessed the in vitro kinetics of rhodamine loaded PLA NP uptake, the toxicity of PLA and PLGA NPs in bovine and human RPE cells, and the efficacy of PLGA NPs to mediate gene transfer in RPE cells in vitro and in vivo in the rat. ©2005 Molecular Vision