Optimized retroviral transduction protocol for human progenitor cells utilizing fibronectin fragments.
BACKGROUND: Retroviral transduction in the presence of fibronectin (FN) fragments has proven an efficient and clinically-applicable procedure for gene transfer into hematopoietic cells. So far, FN-based transduction protocols have been optimized primarily for transduction of stem cells, whereas for several therapeutic applications transduction of clonogenic progenitors (CFU) may be sufficient. METHODS: Transduction protocols for CFU were optimized by evaluating the effect of growth factors, timing of retroviral transduction, CD34-selection and heparin, using a neomycin-phosphotransferase (neo(R))-expressing retroviral vector. RESULTS: The presence of multiple growth factors during prestimulation and transduction, including the differentiating cytokines G-CSF or GM-CSF, substantially enhanced transduction of CFU. Best results were achieved when 24 h of prestimulation were followed by a 24-48 h transduction period in the presence of the CH-296 FN-fragment and IL-3, IL-11, SCF, erythropoietin (EPO), and GM-CSF. With this proto-col we observed highly efficient transduction of BM-derived CFU (90.7 +/- 8.8 % G 418-resistant colonies), even with retrovirus preparations of moderate infectious titer (5 x 10(4) - 2 x 10(5) CFU/mL). The number of CFU increased on average 2.6-fold (range 1.5-3.8) during the transduction procedure. Selection of CD34(+) cells prior to transduction did not improve transduction efficiency. Heparin, even in concentrations as low as 2.0 microg/mL, significantly inhibited transduction of CFU on FN-fragments. DISCUSSION: An optimized protocol for retroviral gene transfer into human clonogenic progenitor cells that allows highly efficient transduction, even with moderate titer retroviral vectors, is presented.