**2.2 Molecular mechanisms underlying intimal thickening**

Intimal thickening is associated with many characteristic phenomena such as the proliferation and migration of SMCs, the accumulation of extracellular matrix in the subendothelial region, and the fragmention of the inner elastic lamina. Analysis of the causal genes of this complex process in patients with PDA and animal models of PDA is resulting in significant progress toward understanding the molecular mechanism underlying it.
