21.6 Small interfering RNA (siRNA)

RNA interferences (RNAi) is a powerful tool to knockdown the expression of targeted gene. The mechanism of RNAi is mediated by dsRNA molecules having sequence identity with that of the targeted mRNA. The same phenomenon can be repeated in mammalian cells by using 21-25bp small interfering RNA (siRNA). The use of siRNA is to subvert the immune response that is otherwise mediated by dsRNA. The transfection of siRNA to the susceptible cells reduces the protein expression in the targeted tissue by 90%. Many targeted proteins are down regulated by use of siRNA technique including lung, heart, and liver. The delivery of siRNA is far complicated than the plasmid DNA because of its small size and possibility of its leakage while injection through intravenous route. The duration of siRNA in the tissue is still an issue. Its half life time and bioavailability in the tissue is responsible to modulate its activity.

 

21.7 Prospects in naked DNA based gene delivery

Non viral gene transfer will become more important as better delivery methods become available. Tail vein injections in rodents will become a widely used technique for rapidly testing expression vectors and gene therapy approaches. RNA interference will become a major element in the gene therapy field.