Related to the mean concentration level of collagen I in AF tissues of wild-type rabbits (543 ± 9.79 ng/μg), its mean concentration level in AF tissues of APOE-knockout rabbits (647 ± 14.9 ng/μg) was increased by 19.1% (p < 0.0001) (Fig 5C). The gene discussed is APOE; the disease is atrial fibrillation.