Efficient gene silencing in mesenchymal stem cells by substrate-mediated RNA interference

We described a novel substrate-mediated RNA interference (RNAi) technology to investigate the effect of neural crest marker expression on the multipotency of human gingival fibroblasts (HGFs). HGFs showed significantly higher neural and chondrogenic differentiation potentials compared with adult bone-marrow-derived mesenchymal stem cells and stem cells from human exfoliated deciduous teeth. By sending target-specific RNAi agents with the conventional vehicle (PolyFect), we observed that the multipotency of HGFs was closely associated with the expression of neural crest marker gene Forkhead box D3 (FoxD3). Using the novel chitosan substrate-mediated method, we successfully delivered short-hairpin RNA constructs to HGFs grown on chitosan without the use of conventional vehicles. The delivery efficiency measured by flow cytometry showed a 10-fold increase for HGFs on chitosan versus those on culture dish, and the cell viability was >95%. Moreover, HGFs with FoxD3 gene knockdown did not form spheroids on chitosan. Based on this working principle, we further selected the gene-silenced population from HGFs. The nonsilenced HGFs showed much higher neural differentiation ability with the nestin expression 40-fold greater than FoxD3-silenced population after induction, suggesting the feasibility of the method to silence genes. The new substrate-mediated gene silencing platform that combines the use of substrate and RNAi can be used to clarify the functions of important genes without suffering the toxicity.