KERATINOCYTE GENE-THERAPY FOR ADENOSINE-DEAMINASE DEFICIENCY - A MODEL APPROACH FOR INHERITED METABOLIC DISORDERS

Disorders in which there is toxic buildup of circulating substrate may be treated by furnishing an enzyme reservoir capable of metabolically processing the excess substrate. The epidermal keratinocyte is a pote ntial site for such a reservoir, In this study, we explore the capacit y of genetically modified keratinocytes to metabolize extracellular su bstrate in a culture model that resembles in vivo epidermal architectu re, Keratinocytes from adenosine deaminase (ADA)-deficient patients we re transduced with a retroviral vector encoding the human ADA gene and the capacity of this tissue to deaminate deoxyadenosine (dAdo) in vit ro was measured. The results show that at a substrate concentration of 10 mu M, ADA-corrected keratinocytes deaminate dAdo at a rate of 0.38 nmol/min.10(6) cells. These results indicate that keratinocytes proce ss extracellular substrate at rates that suggest complete substrate co nversion in a single pass, This study provides a strong indication tha t the epidermis, the largest and most accessible tissue of the body, i s a valuable site for designing clinically relevant gene therapies.