Autologous bone marrow stromal cells engineered to produce 3,4,-dihydroxyphenylalanine (L-DOPA) can potentially be used as donor cells for neural transplantation in Parkinson's disease. Here, we examined the possibility of using several different promoters and either a self-inactivating retrovirus (pSIR) or standard retroviruses to introduce into marrow stromal cells (MSCs), the two genes necessary for the cells to synthesize L-DOPA. pSIR vectors were constructed using the mouse phosphoglycerate kinase-1 (PGK) promoter or the cytomegalovirus (CMV) promoter to drive expression of either a GFP reporter gene or a bicistronic sequence containing the genes for human tyrosine hydroxylase type I (TH) and rat GTP cyclohydrolase I (GC) separated by an internal ribosome entry site (IRES). rMSCs were successfully transduced with both standard retroviral vectors and pSIR containing the PGK promoter. Transduced rMSCs expressed GFP (90.4--94.4% of cells) or were able to synthesize and secrete L-DOPA (89.0--283 pmols/10(6) cells/h). After transduced rMSCs were plated at low density (3--6 cells/cm(2)), the cells expanded over 1000-fold in 3--4 weeks, and the rMSCs continued to either express GFP or produce L-DOPA. Furthermore, two high-expressing clones were isolated and expanded at low-density from rMSCs transduced with pSIR driven by the PGK promoter (97.0% GFP+ or 1096.0 pmols L-DOPA/10(6) cells/h).