<prompt> Neointimal hyperplasia causes vascular graft failure as a result of hypertrophy of -Enodthelial cellsCollagen fibersSmooth muscle cellsElastic fibers  <response>: Neointimal hyperplasia or also known as intimal hyperplasia is a response to vascular injury and is seen as a complication of all forms of arterial reconstruction.Intimal hyperplasia followed by stenosis or restenosis is the principle cause of failure in vascular grafts.Intimal hyperplasia occurs because of smooth muscle cells. These SMCsare activated by vascular injurymigrate from media to the intimamultiply as intimal SMCssynthesize deposit extracellular matrix. 