Sonoporation of human renal proximal tubular epithelial cells in vitro to enhance the liberation of intracellular miRNA biomarkers.

Ultrasound has previously been demonstrated to non-invasively cause tissue disruption. Small animal studies have demonstrated this effect can be enhanced by contrast microbubbles and has potential to be clinically beneficial in techniques such as targeted drug delivery or enhancing liquid biopsies when a physical biopsy may be inappropriate. Cavitating microbubbles in close proximity to cells increases membrane permeability, allowing small intracellular molecules to leak into the extracellular space. This study sought to establish if cavitating microbubbles could liberate cell-specific miRNAs, augmenting biomarker detection for non-invasive liquid biopsies. Insonating human polarised renal proximal tubular epithelial cells (RPTECs), in the presence of Sonovue microbubbles, revealed that cellular health could be maintained while achieving the release of miRNAs miR-21, miR-30e, miR-192 and miR-194 (10.9 fold, 7.17 fold, 5.95 fold, and 5.36 fold respectively). To examine the mechanism of release, enhanced green fluorescent protein (EGFP) expressing RPTECs were generated and EGFP successfully liberated. Cell polarisation, cellular phenotype and cell viability after sonoporation were measured by a number of techniques. Ultrastructural studies using electron microscopy showed gap-junction disruption and pore formation on cellular surfaces. These studies revealed that cell specific miRNAs can be non-specifically liberated from RPTECs by sonoporation without a significant drop in cell viability.