PLGA Microspheres Encapsulating Nanosized Oligonucleotides-Polyethylenimine Complexes: Structural Analysis and Application to Anti-TGFβ2 Therapy in Ocular Cells

Abstract

Purpose: : To design a polyplex system for the sustained delivery and enhanced intracellular penetration of antisense oligonucleotides (ODN) in ocular cells.

Methods: : Nanosized complexes of antisense TGF-β2 phosphorothioate oligonucleotides (PS-ODN) with polyethylenimine (PEI), and naked PS-ODN were encapsulated into poly(lactide-co-glycolide) (PLGA) microspheres prepared by the double-emulsion solvent evaporation method. The effect of medium preparation was evaluated on PEI/ODN complexes size and morphology, and on PLGA microspheres porosity and encapsulation rates. Cultured rat RMG cells were transfected using FITC-ODN/PEI complexes. Efficacy of transfection was evaluated by confocal microscopy and regulation of TGF-β2 gene expression was assayed using quantitative real time PCR and Elisa assay. The distribution of FITC-ODN/PEI complexes was analyzed at various intervals after injection in the vitreous of Lewis rat eyes. PLGA microspheres encapsulating ODN/PEI nanosized complexes were used for the slow release of ODN directed at TGFβ-2 in a rabbit model of filtering surgery.

Results: : Complexes prepared in HBS presented a core-shell structure and a high cellular internalization efficacy, along with a significant and specific down regulation of TGFβ-2 expression and production in RMG cells. PEI induced the formation of large pores observed onto PLGA microsphere surface. Introduction of NaCl in the outer aqueous phase increased the encapsulation efficiency and reduced microsphere porosity. In vivo, 72 hours after intravitreous injection of FITC-ODD/PEI nanosized complexes, ODN seems to preferentially target RMG cells without inducing any detectable toxicity. Finally, microspheres containing antisense TGF-β2 nanosized complexes slowly released the ODNs in the subconjunctival space and significantly improved bleb survival in a rabbit model of filtering surgery.

Conclusions: : Specific and sustained down-regulation of TGFβ-2 expression using ODN/PEI nanosized complexes encapsulated in PLGA microspheres can be achieved in different ocular cells and models.

Keywords: gene transfer/gene therapy • injection • drug toxicity/drug effects