Liver-Directed Recombinant Adeno-Associated Viral Gene Delivery Rescues a Lethal Mouse Model of Methylmalonic Acidemia and Provides Long-Term Phenotypic Correction

Abstract

Methylmalonic acidemia is a severe metabolic disorder caused by a deficiency of the ubiquitously expressed mitochondrial enzyme, methylmalonyl-CoA mutase (MUT). Liver transplantation has been used to treat a small number of patients with variable success, and whether liver-directed gene therapy might be employed in such a pleiotropic metabolic disorder is uncertain. In this study, we examined the therapeutic effects of hepatocytedirected delivery of the Mut gene to mice with a severe form of methylmalonic acidemia. We show that a single intrahepatic injection of recombinant adeno-associated virus serotype 8 expressing the Mut gene under the control of the liver-specific thyroxine-binding globulin (TBG) promoter is sufficient to rescue Mut -/-mice from neonatal lethality and provide long-term phenotypic correction. Treated Mut -/-mice lived beyond 1 year of age, had improved growth, lower plasma methylmalonic acid levels, and an increased capacity to oxidize [1-13 C]propionate in vivo. The older treated mice showed increased Mut transcription, presumably mediated by upregulation of the TBG promoter during senescence. The results indicate that the stable transduction of a small number of hepatocytes with the Mut gene can be efficacious in the phenotypic correction of an inborn error of organic acid metabolism and support the rapid translation of liver-directed gene therapy vectors already optimized for human subjects to patients with methylmalonic acidemia.

Targeting proximal tubule mitochondrial dysfunction attenuates the renal disease of methylmalonic acidemia

“…Together, these findings suggest that cell and/or mitochondrial autonomous effects, rather than elevations in methylmalonic acid per se, are responsible for the hepatic mitochondrial changes and the GFR decrease associated with proximal tubular mitochondrial dysfunction. This challenges previous theories about methylmalonate as a toxic agent (21,22) and further supports observations from gene therapy studies showing that the long-term correction of Mut −/− mice is mediated by a small number of stably transduced cells (13,23). The concept that a kidney with normal Mut activity may be protected from MMA nephrotoxicity is reinforced by a recent study that proposed providing renal allografts as a form of "cellular" therapy for MMA, despite the implicit knowledge that the allograft will be exposed to very high metabolite concentrations in the recipient patient (24).…”

Improving lipoprotein profiles by liver-directed gene transfer of low density lipoprotein receptor gene in hypercholesterolaemia mice

“…Moreover, the activity is proved to be slightly less than CMV and EF1α, but far greater than other hepatocyte-specific promoters such as apoE and CYP2E1 promoters. The TBG promoter has been increasingly and successfully applied in correction of genetic diseases such as mucopolysaccharidosis, muscular dystrophy and methylmalonic acidaemia (Carrillo-Carrasco et al 2010;Bish et al 2011;Cotugno et al 2011) and demonstrated to be efficient in treating FH in this study.…”

Vector design influences hepatic genotoxicity after adeno-associated virus gene therapy

“…In contrast to the AAV-treated cohorts, a control group of untreated Mut +/-mice (n = 51) was followed in parallel for 18 to 25 months, with only 3 mice developing HCC (<10%) (Figure 1B and transgenes were highly effective at rescuing the neonatal lethal phenotype displayed by mice with MMA (25)(26)(27)(28). In the present studies, these large cohorts of treated and control mice were followed for 22 months to monitor the efficacy of neonatal AAV gene therapy and survey for long-term complications.…”