ACAN and atrial fibrillation: The most significant dysregulation of biochemical content due to ECM degradation is the loss of proteoglycan that initiates the degradation of aggrecan, shifting the glycosaminoglycan (GAG) proportion from chondroitin sulfate to keratan sulfate, and increasing other ECM compositions such as fibronectin, versican, biglycan, and decorin.[10] The lamellae of the AF become disorganized as degeneration progresses, with type I collagen generating stronger collagen fibrils predominately found in the NP and inner AF.