Correction of ureagenesis after gene transfer in an animal model and after liver transplantation in humans with ornithine transcarbamylase deficiency

We report effects of gene transfer and liver transplantation on urea synthesis in ornithine transcarbamylase deficiency (OTCD). We measured the formation of [¹⁵N] urea after oral administration of ¹⁵NH₄Cl in two girls with partial OTCD before and after liver transplantation. Ureagenesis was less than 20% of that observed in controls before transplantation, and was normalized afterward. Studies performed on the OTCD sparse fur (spf/Y) mouse showed discordance between OTC enzyme activity and ureagenesis with modest increases in OTC enzyme activity after gene transfer resulting in significant improvement in ureagenesis. This study suggests that both liver transplantation and gene therapy may be effective in improving ureagenesis in OTCD.