MMP2 and osteoarthritis: An acetylated PLGA-PEI (Ac-PLGA-PEI) nanocomplexgel was designed to deliver Matrix metalloproteinase 2 (MMP-2) siRNA to the PC3 cell line of a human prostate tumor for gene silencing and to the collagen matrix embedded in the human chondrocyte cell line C20A4 for chondrocyte dedifferentiation (a hallmark process of osteoarthritis) in vitro to develop a siRNA therapy for osteoarthritis.