Elevated cyclic hydrostatic pressure enhances the transfection activity of lipoplexes by activating clathrin-mediated endocytosis.

Despite significant advancements in liposome-mediated transfection technology over the past decades, achieving optimal transfection efficiency with lipoplex remains challenging in certain primary cells, such as vascular smooth muscle cells, endothelial cells, and suspension cells. Here, we present an innovative approach to significantly enhance Lipofectamine-based transient transfection efficiency in hard-to-transfect cells by applying elevated cyclic hydrostatic pressure (CHP). The plasmids encoding the enhanced green fluorescent protein (EGFP) were transfected using Lipofectamine 3000 reagent, and the transfection efficiency was evaluated by Western blot or flow cytometry. Our results demonstrate that CHP (0.0083 Hz, 0-100 mmHg) significantly enhanced the transfection efficiency of lipoplex in primary human aortic smooth muscle cells (HASMCs) and other difficult-to-transfect cell types. Mechanistic studies revealed that the enhancement of liposome-mediated transfection by CHP was dependent on the activation of clathrin-dependent endocytic pathways. Importantly, this mechanical stimulation did not affect the proliferative or migratory capacities of HASMCs, despite the identification of significantly modulated proteins (5.8 % of the total proteome) by proteomic analysis. This study establishes a novel, safe strategy to enhance lipoplex-mediated nucleic acid delivery in challenging-to-transfect cell types.