LAMB2 and atrial fibrillation: Whilst HBVSMCs expressed the highest amount of fibronectin, perlecan, and laminin, collagen IV was expressed at the greatest levels in pericytes, with more than four times more collagen IV in HPs (2892 mean AF) than HBVSMCs (590 mean AF) and ECs (664 mean AF) (Figure 2b,c).