Tolofari et al., (2010) described increases in PGP9.5 (a nerve fibre marker) and CD31 mRNA expression which correlated with low sema3A mRNA expression in degenerate AF tissue, thus suggesting that sema3A is a natural inhibitor of nerve and blood vessel ingrowth in healthy AF [39], however increased expression was seen in the NP. This evidence concerns the gene PECAM1 and atrial fibrillation.