THE EXOGENOUS CONTROL OF TRANSFECTED C-FOS GENE-EXPRESSION AND ANGIOGENESIS IN CELLS IMPLANTED INTO THE RAT-BRAIN

Previously, we established a stable transfectant, Nf-1, from normal rat kidney (NRK) fibroblasts transfected with a human metallothionein II A (hMT-IIA) promoter/human genomic c-fos fusion gene to produce c-Fos protein. Since the hMT-IIA promoter can be activated by heavy metals, the level of human c-fos gene expression can be increased by addition of heavy metals to the culture medium of Nf-l cells and the anchorage-independent growth of Nf-l in soft agar is markedly enhanced in the presence of transforming growth factor-p (TGF-P) and epidermal growth factor (EGF). In this study, we found that the hMT-IIA promoter can be activated by zinc, resulting in the elevation of fused c-fos gene expression in Nf-1 cells. We transplanted NRK and Nf-l cells into the striatum of the rat brain and investigated whether expression of the human c-fos gene could be modified in the brain by exogenous zinc. After 8 weeks, we found that the Nf-l cells could survive in the rat brain without any immunosuppression and grafts of Nf-l induced angiogenesis when zinc was administered. Such implants enhanced the expression of c-fos mRNA by zinc. These results indicated that the transplanted cells continued expressing the c-fos transgene when the rats were given drinking water containing zinc, resulting in the promotion of cell growth and of neovascularization. This study will present a useful animal model of gene therapy by control of transgene expression in the brain.