Lentiviral based gene transduction and promoter studies in human hematopoietic stem cells (hHSCs)

Human hematopoietic stem cells (hHSCs) have enormous potential for clinical use in cell-based therapies, especially as a gene delivery system. Moreover, lentiviral transduction in stem cells is very often associated with low transduction efficiency and low levels of foreign gene expression. Therefore, it is important to analyze vector and promoter systems that can generate robust foreign gene expression in these cells. In this study, we evaluated and compared the ability of different commercially available promoters to drive the expression of exogenous reporter genes in hHSCs and evaluated the effect of different doses of stem cell growth factors on the expression of transgenes. We used lentivirus based vector system carrying the following promoters: 1) Human cytomegalovirus (CMV) promoter, 2) Simian virus 40 (SV40) promoter, 3) mammalian Ubiquitin C (UBC) promoter and 4) cellular polypeptide chain elongation factor 1 alpha (EF1) promoter. EF1 and CMV promoters robustly drove the expression of green fluorescence protein (GFP) reporter gene, while SV40 and UBC promoters induced very low level of GFP expression. Lentivectors containing EF1 and CMV promoters showed high-level stable GFP expression in human cord blood stem cells for 6 weeks period after post transduction. CD133+ hHSCs stimulated with higher concentration of growth factors exhibited enhancement of transduction rate. Cord blood derived CD133+ hHSCs could be effectively transduced with lentivectors under CMV or EF-1 promoters for the expression of foreign gene.