TRANSGENIC STUDIES WITH A KERATIN PROMOTER-DRIVEN GROWTH-HORMONE TRANSGENE - PROSPECTS FOR GENE-THERAPY

Keratinocytes are potentially appealing vehicles for the delivery of s ecreted gene products because they can be transferred to human skin by the relatively simple procedure of grafting. Adult human keratinocyte s can be efficiently propagated in culture with sufficient proliferati ve capacity to produce enough epidermis to cover the body surface of a n average adult, However, the feasibility of delivering secreted prote ins through skin grafting rests upon (i) the strength of the promoter in keratinocytes and (ii) the efficiency of protein transport through the basement membrane of the stratified epithelium and into the bloods tream, In this paper, we use transgenic technology to demonstrate that the activity of the human keratin 14 promoter remains high in adult s kin and that keratinocyte-derived human growth hormone (hGH) can be pr oduced, secreted, and transported to the bloodstream of mice with effi ciency that is sufficient to exceed by an order of magnitude the circu lating hGH concentration in growing children. Transgenic skin grafts f rom these adults continue to produce and secrete hGH stably, at approx imate to 1/10 physiological levels in the bloodstream of nontransgenic recipient mice. These studies underscore the utility of the keratin 1 4 promoter for expressing foreign transgenes in keratinocytes and demo nstrate that keratinocytes can be used as effective vehicles for trans porting factors to the bloodstream and for eliciting metabolic changes , These findings have important implications for considering the kerat inocyte as a possible vehicle for gene therapy.