TGFB1 and atrial fibrillation: First, when Smurf2 was overexpressed in the inner AF cells that express type II collagen during disc development, the cells started a senescence transition, reducing the ability to proliferate and synthesize matrix and leading to a decrease in cartilage matrix content at 2 months of age.23 Because matrix architecture in the inner AF was altered, moderate/severe clefts and tears occurred at 6 months of age.23 Second, the cells adjacent to the disrupted structure produced and released TGF‐β, which promoted CTGF production and secretion by local cells.