OBJECTIVETo investigate the dynamic changes of type I collagen, and the activity of metalloproteinases-1 (MMP-1) and tissue inhibitor of metalloproteinases-1 (TIMP-1) after angioplasty.

METHODSThe restenotic model of iliac arteries of domestic microswine was established with hypercholesterol feed plus two angioplasties. Angioplastied vessels were harvested at the end of 1, 2, 3 and 6 months after the second angioplasty. Immunohistochemistry, transmission electronic microscopy and image quantitative analysis techniques were employed to study neointimal proliferation, the phenotype of vascular smooth muscle cells (VSMC) and the expression of type I collagen, MMP-1 and TIMP-1.

RESULTSThe peak of vascular neointimal proliferation was at 3 months after angioplasty. The expression of type I collagen gradually increased from 1 to 6 months after angioplasty. For MMP-1, expression was lower in the early stage after angioplasty but increase to normal levels of control vessels at 6 months after angioplasty. Expression of TIMP-1 rapidly increased in the early phase after angioplasty, reached peak at 3 months and maintained the high level till 6 months after angioplasty. Meanwhile, the VSMC was predominantly the synthetic phenotype at the early stage and was transformed to the contractive phenotype at the late stage after angioplasty. The ratio of TIMP-1 and MMP-1 was positively related to the area of the neointima and the expression of type I collagen respectively (P < 0.01).

CONCLUSIONType I collagen increased gradually after angioplasty, which might be determined by the ratio of TIMP-1/MMP-1 and also related to the phenotype of VSMC.