Evaluation of methods for transient transfection of a murine macrophage cell line, RAW 264.7.

Monocyte/macrophage cell lines are fastidious cells commonly used in transient transfection experiments. In the course of a study of gene regulation by lipopolysaccharide (LPS), we have compared several methods for DNA-mediated cell transfection to determine which would be optimally applicable to the macrophage line, RAW 264.7. Both the response level (LPS inducibility) and the degree of inter-assay variation were evaluated for each transfection technique. The following methods were compared: Lipofectin, LipofectAMINE, LipofectAMINE PLUS, SuperFect, Ca3(PO4)2 DNA co-precipitation, DEAE dextran-mediated transfection and electroporation. The transfected plasmid DNA included a luciferase reporter construct containing the junB minimal promoter under the control of an LPS-inducible 1300-bp regulatory fragment downstream of junB 5'-flanking sequence, as well as a beta-galactosidase reporter construct under the adenovirus promoter and enhancer used as an internal control. Electroporation, followed by a resting period of 16-24 h before stimulation with LPS, had the highest inducibility of all methods. DEAE dextran and Ca3(PO4)2 precipitation showed the least and the greatest inter-assay variation, respectively. For all other methods, inter-assay variability fell within this range. The results presented may serve as both a general reference and a guide for reporter gene studies in this or other macrophage cell lines.