Sustained gene expression in transplanted skin fibroblasts in rats

Retrovirus-mediated gene transfer into adult skin fibroblasts has provided measurable amounts of therapeutic proteins in animal models. However, the m ajor problem emerging from these experiments was a limited time of vector e ncoded gene expression once transduced cells were engrafted We hypothesized that sustained transduced gene expression in quiescent fibroblasts in vivo might be obtained by using a fibronectin (Fn) promoter. Fibronectin plays a key role in cell adhesion, migration and wound healing and is up-regulate d in quiescent fibroblasts. Retroviral vectors containing human adenosine d eaminase (ADA) cDNA linked to rat fibronectin promoter (LNFnA) or viral LTR promoter (LASN) were compared for their ability to express ADA from transd uced primary rat skin fibroblasts in vivo. Skin grafts formed from fibrobla sts transduced with LNFnA showed strong human ADA enzyme activity from 1 we ek to 3 months. In contrast, skin grafts containing LASN-transduced fibrobl asts tested positive for human ADA for weeks 1 and 2, were faintly positive at week 3 and showed no human ADA expression at 1, 2 and 3 months. Thus, a fibronectin promoter provided sustained transduced gene expression at high levels for at least 3 months in transplanted rat skin fibroblasts, perhaps permitting the targeting of this tissue for human gene therapy.