Decreased concentration levels of aggrecan and collagen II were confirmed in NP and AF tissues of APOE-knockout rabbits (KO-NP and KO-AF), but increased level of collagen I was determined in KO-AF as compared with the respective values in NP and AF tissues of wild-type rabbits (WT-NP and WT-AF) (p < 0.0001). This evidence concerns the gene ACAN and atrial fibrillation.