Extracellular vesicles propagate cellular senescence by transferring miR34a in airway epithelial cells

Background: COPD is a disease of accelerated ageing, that may result from cellular senescence. MicroRNA-34a induces cellular senescence in small airway epithelial cells (SAEC) by inhibiting sirtuin-1 (SIRT1), an anti-ageing molecule. Extracellular vesicles (EVs) may contain microRNAs that can be modified in senescent cells. Senescent cells influence their environment and induce cellular senescence in neighbouring cells, thereby spreading senescence. The role of EVs in spreading senescence is currently unknown. Aim: To compare the effect of EVs produced by SAEC from COPD patients and non-smoker (NS) donors on cellular senescence of healthy SAEC Methods: Primary SAEC were cultured in submerged culture. EVs were isolated by ultracentrifugation. Recipient cells were treated with EVs, and senescence markers were measured by RT-qPCR and Western blot Results: Healthy cells treated with COPD EVs showed increased expression of miR-34a within 3h (1.3-fold increase in treated cells compared to non-treated, n=5, p<0.05). Consequently, decreased expression of the protein SIRT1 (3.3-fold, n=5, p=0.01) and increased expression of p21CIP1 (3.6-fold, n=6, p<0.05) was detected 48h after treatment with COPD EVs compared to NS EVs. This effect was specific to miR-34a, as pre-treatment of EVs with a detergent or pre-treatment of recipient cells with antagomir against miR-34a blocked this effect Conclusion: These data suggest that vesicular miR-34a is involved in cellular senescence and may contribute to senescence propagation and ageing acceleration observed in COPD lungs. Further exploration of EVs in senescence may provide useful biomarkers and targets for future COPD therapy