Cyclic stretching of AF cells at high strain of 8–20% induces downregulation of anabolic factors (ACAN, COL2) [33] and upregulation of catabolic and inflammatory factors (MMP1, MMP3, MMP9, MMP13, IL-1β, IL-6, IL-8, TLR-2, TNF, NGF) [33–35]. The gene discussed is MMP9; the disease is atrial fibrillation.