Abstract: Objective To study the relationship between the medial calcification of arteries and the expressions of matrix metallopeptidase 9 (MMP-9) and tissue inhibitor of metalloproteinase 1 (TIMP-1) in uremic patients. Methods Pieces of radial arteries were taken from 80 uremic patients at the time of arteriovenous fistula operation. The control radial arteries were taken from trauma patients with normal kidney function at the time of amputation operation. Vascular calcification was evaluated histomorphometrically on Von Kossa-stained sections, and the expressions of MMP-9, TIMP-1, osteopontin (OPN), collagen I, core binding factor a-1 (Cbfa-1) were determined immunohistochemically. Other related factors including serum calcium, phosphate, cholesterol, triglyceride (TG), low-density lipoproteins (LDL), albumin (ALB), hemoglobin, intact parathyroid hormone (iPTH) and C-reactive protein (CRP) were also detected. Results Vascular calcification was found in 36 uremic patients (45%), while no vascular calcification in the control group. Mild to moderate calcification was found in 25 uremic patients, and severe calcification in 11 cases. All of the radial arteries with calcification showed positive immunostaining of MMP-9, TIMP-1, OPN, collagen I and Cbfa1 (p<0.01). In some uremic radial arteries without morphologically obvious calcification, immunostaining of OPN and collagen I were also positive, but immunostaining of Cbfa1 was negative. Mean arterial blood pressure, serum phosphate, serum calcium-phosphate product, serum iPTH and CRP were significantly higher in uremic patients than in controls (p＜0.01), but body mass index, serum calcium, TG, total cholesterol, LDL and ALB had no differences between the two groups. Conclusion We have demonstrated, for the first time, that expressions of MMP-9 and TIMP-1 in arteries are correlated to vascular calcification in uremic patients. Our results suggest that the imbalance expression of MMP-9/TIMP-1 may cause, at least partially, vascular medial calcification in uremic patients.

Key words: Radial arteries, Vascular calcification, Matrix metallo-proteinase inhibitor-1