OBJECTIVE: The saphenous vein (SV) used in coronary artery bypass grafting is submitted to elevated and continuous shear stress. Occlusion of the grafts can occur in response to the new hemodynamic conditions. The aim of this study is to compare the precocious structural and molecular (cDNA) changes in saphenous veins grafts submitted to low pressure hemodynamic conditions versus systemic hemodynamic conditions. METHOD: Forty sections of SV were cultivated "ex-vivo" under venous hemodynamic conditions (VHC) (without pressure, flow: 5 mL/min) and under arterial hemodynamic conditions (AHC) (pressure: 80 mmHg, flow: 50 mL/min). The following variables were analyzed: cellular viability (MTT assay) cellular density (hoeschst 33258 staining) and apoptosis (TUNEL assay), before and 1, 2 and 4 days after the procedure. "cDNA microarray" analysis of the SV sections was used to determine the precociously changed molecular targets in the veins cultivated under arterial conditions. The identification of these targets was achieved using a RNA homogenized pool of these vein sections, interacting on slides with 16,000 pre-determined human genes (Agilent Technologies slide). The genes with changed expressions were verified by real time PCR in the veins of 16 patients. RESULTS: There was a gradual reduction in the cellular density and in the tissue viability in the saphenous veins cultivated under AHC, whereas no alterations were observed in the saphenous veins cultivated under VHC of up to 4 days. In the AHC group there were signs of a cellular apoptotic process (positive - TUNEL) from the first day after cultivation. In the VHC group these alterations were not observed. Although the cellular density was the same in the veins submitted to arterial conditions, after 24 hours of cultivation, many cells already showed signs of the apoptotic process. The Oncogene 3 and the Interleucin 1ß were the most common sites with alterations identified in this research. The Oncogene 3 expression was elevated in 11 (68.7%) of the veins cultivated under AHC, and the Interleucin 1ß expression was elevated in 9 (56.2%) of these vein sections (p<0.05). CONCLUSION: The "ex vivo" study model was able to mimic events that occur "in vivo" by SVs utilized in the coronary artery bypass grafting. In the AHC group precocious loss of cellular viability (apoptosis) and significant elevation in the Oncogene 3 and Interleucin 1ß genic expressions were observed. The long-term follow up of these patients is important to determine the real effect of these immediate changes in the patency of the vein grafts.
Myocardial revascularization; Saphenous Vein; Gene Expression
