SIRNA-loaded PLGA microspheres for regulation of macrophage gene expression

Abstract

Macrophage polarization has been shown to be a key event in inflammatory processes. It follows that manipulation of macrophage states may offer a powerful tool to control innate immune responses. In this project, we studied the use of Poly (lactic-co-glycolic acid) PLGA microspheres to deliver small interfering RNA (siRNA) for post-transcriptional gene silencing for applications in engineering macrophage fates. Three human monocytic cell lines were selected to generate model macrophage populations; THP-1, U937 and HL60. Classical macrophage polarization protocols were applied to all three cell lines to generate M0, M1 and M2 phenotypes, and subsequently characterized by macrophage characteristics. In parallel, PLGA microspheres were engineered and characterized in their efficiency as drug delivery vehicles to macrophage lines. Finally, PLGA microspheres carrying siRNA against human TNF-α (siTNF) were incubated with polarized macrophage populations. This treatment was shown to be useful in attenuating TNF-α gene expression in all three cell lines, achieving 66.2%, 87.1% and 89% reduction in M1 polarized THP-1, U937 and HL60 cells respectively. Expression of selected markers was also evaluated as an indication of pro- and anti-inflammatory responses to siTNF treatment. In conclusion, the results suggest siRNA-loaded microspheres to be effective for the manipulation of macrophage states. Ongoing work includes studying the use of siRNA and therapeutic gene combinations to effect greater control of macrophage fate.