Observations on arterial grafts

Abstract

Allografts and autografts of central ear arteries 0.5 mm in diameter and 10 mm in length were transplanted in rabbit ears and enclosed with transparent plastic discs in place of the reflected skin on either surface of the ear. This experimental model allowed continuous monitoring of grafted vessels by naked eye examination and by in vivo photomicroscopy. Successfully autografted arteries retained spontaneous vasomotor activity and responses to vasoactive drugs in vivo. No autografts thrombosed after the initial 2 hour critical period for surgical trauma. They were found to function for as long as 493 days that they were followed. Morphologically they showed variable degrees of intimal thickening containing numerous myointimal cells from early stages. Medial smooth muscle cells were viable in all the autografts. Many of the successfully allografted arteries thrombosed at 7 to 8 weeks following grafting due to immune reaction. Grafts that survived the immune crisis continued to function as blood conduits for as long as 484 days that they were followed. In general allografts showed progressive loss of spontaneous vasoactivity by about 3 to 4 weeks after grafting. They also showed marked reduction in their response to vasoactive drugs. Morphologically they showed endothelial shedding, severe intimal thickening, medial smooth muscle cell destruction and immune cell infiltration. In the early stages myointimal cells were few in number in the thickened intimae where infiltrating immune cells accounted for the majority of the cells present. By about 150 days after grafting myointimal cells became prominent in the thickened fibrotic intima. Antigenicity of allografted arteries was substantiated by the observation that in the skin grafts exchanged between artery recipient and artery donor rabbits accelerated signs of rejection were observed in the artery recipient rabbits. Evidence was obtained to indicate that myointimal cells were poorly contractile as judged by the response of allografts to vasoactive drugs. Some of the myointimal cells had close morphological similarities to endothelial cells suggesting the possible origin of myointimal cells from endothelial cells. Show more