Direct Cutaneous Gene Delivery in a Human Genetic Skin Disease

The skin is an accessible somatic tissue for therapeutic gene transfer and, depending on therapeutic goals, a variety of cutaneous gene delivery approaches are currently available. Recent advances in direct injection of naked DNA into intact skin have shown promise and are less labor-intensive than approaches involving grafting of genetically modified cells. We have regenerated skin from transglutaminase 1 (TGase1)-deficient patients with the genetic skin disease lamellar ichthyosis (LI) on nude mice to examine the corrective impact of direct naked plasmid injection. Regenerated LI patient skin receiving repeated in vivo injections with a TGase1 expression plasmid displayed restoration of TGase1 expression in the correct tissue location in the suprabasal epidermis. Unlike LI skin regenerated from keratinocytes, first transduced in vitro with a retroviral expression vector for TGase1 prior to grafting, however, directly injected LI skin displayed a nonuniform TGase1 gene expression pattern. In further contrast, direct injection failed to correct the central histologic and functional abnormalities of the disease. These data demonstrate that partial restoration of gene expression can be achieved via direct injection of naked DNA in human genetic skin disease tissue but underscore the need for new advances to achieve efficient and sustained plasmid-based gene delivery to the skin. Genes may be delivered to skin either by direct administration to intact tissue or by transplantation of genetically modified cells. We examined the corrective impact of these 2 different approaches using TGase1-deficient human lamellar ichthyosis patient skin regenerated on nude mice. Successful restoration of spatially appropriate TGase1 gene expression could be achieved by both methods. Transplantation of genetically modified keratinocytes, however, was superior to direct injection with naked TGase1 expression plasmid in normalizing histologic and functional disease parameters. These findings highlight a need for development of new approaches to naked DNA-based gene delivery for treatment of genetic skin disorders.