COL1A1 and atrial fibrillation: We first screened AF cells from different patients for metabolic activity and gene expression profiles regarding apoptosis (BAX), cellular complement regulators (CD46, CD55, CD59), inflammatory markers (IL-6, IL-8), matrix-degrading enzymes (MMP-1, MMP-3), and ECM proteins (COL1A1, elastin, fibrillin-1).