MR-IMAGING AND SCINTIGRAPHY OF GENE-EXPRESSION THROUGH MELANIN INDUCTION

PURPOSE: To determine whether an expression vector that encodes for hu man tyrosinase, the key enzyme in the melanin production pathway, can be used to image gene expression with magnetic resonance (MR) imaging and scintigraphy. MATERIALS AND METHODS: Mouse fibroblasts and human e mbryonal kidney cells were transfected with an expression vector that contained a complete complementary DNA sequence that encodes the human tyrosinase gene (pcDNA3tyr). Transfected cells were assayed for messe nger RNA presence, melanin staining, and indium-lll binding; scintigra phy and MR imaging were performed. RESULTS: Transfected cells containe d tyrosinase messenger RNA and stained positively for melanin. Transfe cted cells had a higher In-111 binding capacity than nontransfected ce lls, a difference readily detectable with scintigraphy. MR imaging sho wed transfected cells to have markedly higher signal intensity after g ene transfer than nontransfected cells. CONCLUSION Gene transfer and e xpression in cell culture can be detected with MR imaging and scintigr aphy. The proposed strategy of using an imaging marker gene may have a substantial effect on the noninvasive imaging of gene therapy.