Down-regulation of expression of rat pyruvate dehydrogenase E1alpha gene by self-complementary adeno-associated virus-mediated small interfering RNA delivery.

Mutations in the E1alpha subunit gene (PDHA1) of the pyruvate dehydrogenase complex (PDC) are common causes of congenital lactic acidosis. An animal model of E1alpha deficiency could provide insight into the pathological consequences of mutations and serve to test potential therapies. Small interfering RNAs (siRNAs) were designed to cleave the messenger RNA (mRNA) of the E1alpha subunit and were tested in vitro to assess the feasibility of producing a gene knockdown in rats. HEK 293 cells were co-transfected with a rat PDHA1 expression vector and eight naked siRNAs that specifically targeted rat E1alpha mRNA. Quantitative PCR (qPCR) analyses showed that four siRNAs reduced rat PDHA1 RNA levels up to 85% by 24h and up to 65% by 56h, compared to negative and positive controls. Since oligonucleotide-mediated siRNA delivery provided only transient suppression, we next selected two siRNA candidates and generated self-complementary, double-stranded adeno-associated virus (scAAV) vectors (serotypes 2 and 5) expressing a rat short hairpin siRNA expression cassette (scAAVsi-PDHA1). Rat lung fibroblast (RLF) cultures were infected with scAAVsi-PDHA1 vectors. The RLF PDHA1 mRNA level was reduced 53-80% 72h after infection and 54-70% 10 days after infection in RLF cultures. The expression of E1alpha and the specific activity of pyruvate dehydrogenase were also decreased at 10 days after infection in RLF cultures. Thus, scAAV siRNA-mediated knockdown of PDHA1 gene expression provides a strategy that may be applied to create a useful animal model of PDC deficiency.