SYSTEMIC DELIVERY OF SECRETED PROTEIN BY GRAFTS OF EPIDERMAL-KERATINOCYTES - PROSPECTS FOR KERATINOCYTE GENE-THERAPY

Grafts of autologous keratinocytes genetically altered to secrete a ne w gene product are a potential vehicle for gene therapy. To consider t he feasibility of such an approach, we have examined the ability of ke ratinocytes to secrete and deliver apolipoprotein E (apoE) to the circ ulation of mice bearing grafts of human keratinocytes. The grafted ker atinocytes secreted two forms of apoE, an endogenous apoE encoded in t he genome and a recombinant apoE encoded in a transfected gene constru ct. In vitro studies showed that endogenous apoE was secreted from bas al keratinocytes whereas recombinant apoE was secreted from basal as w ell as suprabasal cells. On the basis of amounts of recombinant apoE p resent in the serum of grafted mice, we estimate that a graft occupyin g 2% of the surface area of an adult human would deliver 6.5-8.3 mg of recombinant apoE protein per day.