A novel non-invasive approach to quantify microRNA expression in nasal fluid from COPD patients using a microfluidic platform

<b>Introduction:</b> COPD is a chronic inflammatory lung disease associated with accelerated lung aging and elevated levels of senescent cells in the airways. microRNA-21 (miR-21) is up-regulated in senescent cells and in COPD. However, miRNA levels are usually examined in cells or fluid that are obtained invasively therefore we examined whether we could detect miRNA-21 using a less invasive method. <b>Aim:</b> To quantify miR-21 in nasal fluid obtained non-invasively from non-smokers and COPD patients <b>Methods:</b> Microfluidic chip were designed with a main channel connected to 55 chambers which are microarrayed with complimentary miR-21 capture probe. To validate miR-21 assay, small airway epithelial cells (SAEC) were treated with miR-21 mimics and inhibitors. Single cells (50 cells/experiment) were optically manipulated and lysed in the chambers. Nasal fluid was absorbed using synthetic absorptive matrices and introduced into the chip. MiR-21 molecules were captured, bound to fluorescently tagged reporter and detected using microscopy. <b>Results:</b> A miR-21 antagomir (inhibitor) reduced miR-21 expression in SAEC from COPD patients by 47% to 64737±16635 molecules/cell and 32% with RT-qPCR (n=3). A miR-21 mimic increased miR-21 expression in SAEC from non-smokers by 13.7-fold to 234470±16328 molecules/cell and 6-fold with RT-qPCR (n=3). Single miR-21 molecules in nasal fluid were significantly (p&lt;0.05) increased in COPD patients 39381±5602 molecules by 4.3-fold compared to non-smokers 9100±1037 molecules (n=6). <b>Conclusion:</b> MiR-21 expression can be quantified in a small volume of nasal fluid using microfluidics and show expression differences between non-smokers and COPD patients.