A similar number of collagen transcripts was higher (n = 9) and lower (n = 7) in FAT over AF cells, with 7 of the higher transcripts identical for both IVD cell types, including two isoforms each for collagen IV and collagen V and Col4a1 and Col4a2 transcripts being the highest ECM related transcripts in FAT cells. The gene discussed is COL4A1; the disease is atrial fibrillation.