Purpose: Gene therapies via Noggin  small interfering (si)RNA (siNoggin ) and bone morphogenetic protein (BMP )-2  plasmid DNA (pBMP-2 ) may be promising strategies for bone repair/regeneration, but their ideal delivery vectors, efficacy difference, and underlying mechanisms have not been explored, so these issues were probed here.
Methods: This study used lipopolysaccharide-amine nanopolymersomes (LNPs), an efficient cytosolic delivery vector developed by the research team, to mediate siNoggin  and pBMP-2  to transfect MC3T3-E1 cells, respectively. The cytotoxicity, cell uptake, and gene knockdown efficiency of siNoggin -loaded LNPs (LNPs/siNoggin ) were studied, then the osteogenic-differentiation efficacy of MC3T3-E1 cells treated by LNPs/pBMP-2  and LNPs/siNoggin , respectively, were compared by measuring the expression of osteogenesis-related genes and proteins, alkaline phosphatase (ALP) activity, and mineralization of the extracellular matrix at all osteogenic stages. Finally, the possible signaling pathways of the two treatments were explored.
Results: LNPs delivered siNoggin  into cells efficiently to silence 50% of Noggin  expression without obvious cytotoxicity. LNPs/siNoggin  and LNPs/pBMP-2  enhanced the osteogenic differentiation of MC3T3 E1 cells, but LNPs/siNoggin  was better than LNPs/pBMP-2 . BMP/Mothers against decapentaplegic homolog (Smad) and glycogen synthase kinase (GSK)-3β/β-catenin signaling pathways appeared to be involved in osteogenic differentiation induced by LNPs/siNoggin , but GSK-3β/β-catenin was not stimulated upon LNPs/pBMP-2  treatment.
Conclusion: LNPs are safe and efficient delivery vectors for DNA and RNA, which may find wide applications in gene therapy. siNoggin  treatment may be a more efficient strategy to enhance osteogenic differentiation than pBMP-2  treatment. LNPs loaded with siNoggin  and/or pBMP-2  may provide new opportunities for the repair and regeneration of bone.
Keywords: gene delivery, nanopolymersomes, Noggin, small interfering RNA, bone morphogenetic proteins, osteogenesis