Targeted editing of the 21-hydroxylase locus confers durable therapeutic effect in a murine model of congenital adrenal hyperplasia.

Abstract

Contemporary treatment for congenital adrenal hyperplasia is lifesaving; however, long-term deleterious effects from the disease and complications from the inadequacy of available treatment remain problematic. Locus-specific correction of the defective 21-hydroxylase gene through genomic editing has the potential to address this unmet need by simultaneously restoring gene function and physiological control. Editing is necessitated by the constant cellular turnover in the adrenal cortex which limits the durability of conventional gene addition strategies using recombinant adeno-associated virus. We have developed a homology-independent targeted integration genomic editing strategy that conferred phenotypic benefit in a mouse model using a dual recombinant adeno-associated virus approach. Reconstitution of 21-hydroxylase expression in the adrenal gland increased corticosteroid production, reduced adrenal gland hyperplasia, and reduced expression of renin and aldosterone synthase with these effects maintained to 15 weeks without diminution. This is beyond the adrenocortical cellular turnover time, providing initial evidence of adrenocortical progenitor cell targeting. Importantly, the editing strategy used is potentially applicable to the majority of causative mutations in classical congenital adrenal hyperplasia. Collectively these data provide strong impetus for addressing the challenges of clinical translation, with development and evaluation of strategies for efficient targeting of human adrenocortical progenitor cells being the most formidable.