Investigation of The Effects of TNF-α and L-Arginine on Ex Vivo Treated Left Internal Mammary Artery (LIMA) Grafts

Coronary artery bypass grafting (CABG) is a standard procedure performed for revascularization and left internal mammary artery (LIMA) is the most preferably used graft for CABG, thanks to its long-term patency, and increased survival from myocardial infarction. Although fibrosis and calcification of LIMA grafts are observed less compared to other grafts, which leads to a decrease of graft patency or result in graft fail depending on the excision location, IMA grafts can tend to calcify in the long term. L-Arginine is the precursor of nitric oxide (NO) synthesis which is a regulator of the vascular inflammation. In the study, LIMA grafts harvested from 18 male patients were treated ex vivo with either TNF-α or L-Arginine before cryosectioning. The cryosectioned tissue grafts stained with H&E and Masson’s Trichrome were imaged with a brightfield microscope to observe the effects of the treatments on the grafts’ morphology and collagen composition. LIMA grafts were also stained with Alizarin Red S and imaged with a fluorescence microscope for calcification detection. The effects of the treatments on tissue morphology, and elemental composition were examined with scanning electron microscopy (SEM), and Elemental Dispersive Spectroscopy (EDS), respectively, after tissues were critically dried. Results suggested the potential of L-Arginine for improving the LIMA graft patency in a preliminary manner, since L-Arginine improved graft morphology to be more organized, increased collagen deposition, decreased calcification regardless of the patient age.