153 Relationship between micro RNA-145 and vascular smooth muscle cell senescence in diabetes

Introduction Saphenous vein (SV) graft failure after coronary bypass surgery is a significant problem in Type 2 diabetic (T2DM) patients, characterised by aberrant smooth muscle cell (SMC) remodelling. SV-SMC cultured from diabetic patients express elevated levels of microRNA-145, exhibit distinct morphology, impaired proliferation and DNA damage. This study explored a potential relationship between miR-145, DNA damage response signalling (DDR) and SV-SMC senescence. Methods Using native human non-diabetic (ND) and T2DM-SMC, DDR signalling proteins (ATM, ATR, p21) were measured (real-time PCR) and subsequently quantified in ND cells overexpressing miR-145 (premiR-145 transfection). Conditioned medium (CM) from miR-145 overexpressing cells was analysed by ELISA for indicators of a senescence associated secretory phenotype (SASP) and to explore intracellular signalling (immunoblotting) in naive ND-SMC. The effect of siRNA knockdown or pharmacological inhibition of ATM/ATR on cell proliferation was also explored (cell counting). Results Increased expression of ATM, ATR and p21 was observed in T2DM-SMC relative to ND-SMC (n=8, p Conclusion Aberrant expression of DDR proteins in T2DM-SMC can be mimicked, at least partially by miR-145 overexpression. MiR-145 drives a SASP, resulting in chronic p-38 phosphorylation. MiR-145 holds potential as a therapeutic target to ameliorate SMC senescence.