Retroviral-Mediated Gene Transfer of Human Ornithine Transcarbamylase into Primary Hepatocytes of spf and spf-ash Mice

The sparse fur (spf) and the sparse fur/abnormal skin and hair (spf-ash) mice are two murine models of the human X-linked disorder ornithine transcarbamylase (OTC) deficiency. A defective recombinant retrovirus, ΔN2OTC was used to transduce primary hepatocytes derived from these mutant animals. Transduction of the primary cultures was highly efficient, with an average proviral copy number of 0.5–2 per cell in the population of transduced hepatocytes. Northern analysis and slot blots of total RNA isolated from transduced cells showed levels of human OTC mRNA to be equivalent to that present in normal human liver. Enzymatic assays demonstrated that a partial biochemical correction of the defect was achieved. After retroviral transduction, the hepatocytes were trypsinized and replated for long-term culture. Viability after replating exceeded 90%, indicating that the transduced cells might be useful for transplantation. The successful in vitro correction of OTC deficiency by this vector suggests that it will also be useful in somatic gene therapy experiments.

Overview summary

Ornithine transcarbamylase (OTC) deficiency is the most common of the urea cycle disorders in humans. Two mouse models for OTC deficiency exist, and Grompe et al. document transfer and expression of human OTC in cultured primary hepatocytes from these mice. Since liver is the ideal target for gene replacement therapy in this disorder, due to the presence of other urea cycle enzymes, these experiments represent a first step in the development of gene therapy for OTC deficiency.