In order to investigate the neuroprotective effects of cyclin-dependent kinase-5 （cdk-5） inhibition in mice with Niemarm-Pick disease type C （NPC） （npc^-/-）, recombinant adeno-associated virus （rAAV） carrying the small interfering RNA （siRNA） specific for cdk-5 gene was injected into 3-day-old npc^-/- mice intracerebroventricularly. The rAAV-GFP-injected age-matched npc^-/- mice and non-surgery age-matched npc^-/- mice were employed as controls （n=6-10/group）. From the 4th to 8th week after the treatment, mice were weighed, and evaluated for limb motor activity by using the coat hanger test once a week. Eight-week-old npc^-/- mice were sacrificed by decapitation, and brains were quickly dissected and halved sagittally. Immunohistochemistry, Western blotting, and HE staining were used to evaluate the neuropathology in npc^-/- mice. The results showed that rAAV-cdk-5-siRNA-GFP significantly reduced the number of axonal spheroids, delayed the death of Purkinje neurons, ameliorated motor defects in npc^-/- mice, and significantly attenuated the hyperphosphorylation oftau proteins. These data suggested that inhibition of cdk-5 activity has neuroprotective effect on neurons in NPC mice.
Cyclin dependent kinases （cdks） play an important role in the pathogenesis of multiple neurodegenerative diseases. To explore the possibility of cdks-related gene therapy for neurodegen-erative diseases, we packed recombinant adeno-associated virus （rAAV） encoding cdc2-siRNA. The expressing plasmid pAAV-MCS-EGFP-U6-cdc2-siRNA was constructed by using molecular biological techniques. The rAAV encoding cdc2-siRNA （rAAV-EGFP-U6-cdc2-siRNA） was packed by calcium phosphate mediated co-transfection of the plasmid pAAV-MCS-EGFP-U6-cdc2-siRNA, p-RC and p-Helper into AAV-293 cells. DNA sequencing proved the successful construction of U6-cdc2-siRNA in pAAV-MCS-EGFP. Seventy-two h after packaging, the expression of EGFP could be detected in AAV-293 cells. Western blotting revealed that cdc2 gene expression in AAV-293 cells was down-regulated markedly after transfection with rAAV-EGFP-U6-cdc2-siRNA, which evidenced the satisfactory silencing effect of this virus. It was concluded that the packaging of rAAV encoding cdc2-siRNA was successful. rAAV encoding cdc2-siRNA could silence cdc2 gene effectively, which might offer a novel means for the treatment of neurodegenerative diseases.
In order to explore the role of TNF-α in Niemann-Pick type C （NPC） disease, lentiviral-delivered RNA interference （RNAi） was used to silence the expression of murine TNF-α gene in vitro and in npc mice. Interference efficiency of the lentivirus expressing TNF-α-siRNA, previously constructed with the concentration of 2 x 108 ifu/mL, was determined by RT-PCR and ELISA in BV-2 cells and astrocytes. At the same time, the constructed Lenti-TNF-α-siRNA was intracerebroventricularly infused into 4-week old npc mice for a 4-week period, and the mice were divided into 3 groups： Lenti-TNF-α-siRNA （n=6）, control lentivirus （n=6）, and NPC mice without any intervention （n=4）. By using immunohistochemistry and real-time PCR, the down-regulation of the target genes was detected. The Lenti-TNF-α-siRNA downregulated the expression of murine TNF-α gene efficiently in vitro and the interference efficiency was 66.7%. Lentivirus could be expressed stably for long-term in the npc mice brain. Immunohistochemistry and real-time PCR revealed that, as compared with non-intervention group and Lenti-control group, Lenti-TNF-α-siRNA efficiently down-regulated the expression of murine TNF-α gene with the interference efficiency being 66.9%. TNF-α-siRNA downregulated the expression of TNF-α gene in vitro and in vivo, which provided a potential tool for studying and treating neurodegenerative diseases and TNF-α-related diseases.
