The role of mTOR inhibitors and HMG-CoA reductase inhibitors on young and old endothelial cell functions, critical for re-endothelialisation after percutaneous coronary intervention: an in vitro study.

ABSTRACT

Percutaneous coronary intervention (PCI) has become a standard treatment in patients with acute coronary syndrome. However, it is associated with endothelial cell denudation, which may predispose to in-stent thrombosis and restenosis. Pharmacological methods which prevent restenosis can delay post-PCI re-endothelialisation. We have therefore examined how atorvastatin (HMG-CoA reductase inhibitor), sirolimus and everolimus (mTOR inhibitors) affect young and old endothelial cell functions which are responsible for wound healing after PCI. Replicative senescence was induced by serial passages of human umbilical vein endothelial cells (HUVECs). The cells which were examined at their first passages and last passages were designated as 'young' and 'old' respectively. Young and old endothelium were grown to confluence and were wounded by scraping. Scratch healing in the presence or absence of atorvastatin (AT), rapamycin (SR) and everolimus (EV) was monitored by time-lapse microscopy. In addition cells were assessed for viability (MTT assay), migration (chemotaxis chamber), proliferation (3H-thymidine), and cytokine production (immunoassays). Senescent endothelial cells produce more proinflammatory cytokines, angiogenic VEGF and extracellular matrix proteins. They stop proliferating and have diminished migration. When compared to young endothelium, they have similar viability and can regenerate wounds in comparable time. The drugs that have been tested have anti-inflammatory properties but even after pretreatment old cells still produced significantly higher concentration of tested mediators in comparison with young ones. In the concentration obtained in serum after stent implantation, mTOR inhibitors in dose-dependent manner reduced cell proliferation, migration and wound healing. Reduced healing is more pronounced in young endothelium. Atorvastatin, at clinically relevant concentration, is safe for young and old cells. Atorvastatin, sirolimus and everolimus inhibited the secretion of pro-inflammatory mediators in young and old endothelium. In concentrations seen in serum during standard therapy, rapalogs impair endothelial cell regeneration after injuries mimicking those occurring during PCI, while atorvastatin does not affect the healing.