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BACKGROUND The process of vascular calcification has been associated with the canonical Wnt/β-catenin signalling pathway in cell cultures and animal studies. The relationship between circulating Wnt/β-catenin inhibitors and vascular calcification in dialysis patients is unknown. The aim of this study was to investigate the associations between serum dickkopf-1 (Dkk-1) and sclerostin, two circulating inhibitors of the Wnt/β-catenin signalling pathway, and the severity of aortic calcification (AoC) and cardiovascular outcomes in dialysis patients. METHODS This was a prospective observational cohort study. One hundred and twenty-five patients on maintenance haemodialysis participated in the study. Serum levels of Dkk-1 and sclerostin were measured. AoC scores were calculated from plain films of both posterior-anterior and lateral views. The patients were followed up for 2 years or until death or withdrawal. RESULTS The circulating sclerostin level was inversely associated with the severity of AoC (P = 0.035) and indicators of the bone turnover rate including serum alkaline phosphatase (ALP) (r = -0.235, P = 0.008) and intact parathyroid hormone (r = -0.523, P < 0.001). Furthermore, Cox regression analysis indicated that the patients with high circulating sclerostin levels were less likely to experience future cardiovascular events [1 pmol/L sclerostin increase, hazard ratio 0.982 (95% CI, 0.967-0.996), P = 0.015] after adjusting for a propensity score. In contrast, serum Dkk-1 was not associated with AoC and clinical outcomes. CONCLUSIONS In long-term haemodialysis patients, circulating sclerostin but not Dkk-1 is inversely associated with AoCs and future cardiovascular events. Our findings suggest that sclerostin, as a bone-related protein, might act as a communicator between uraemic bone and vasculature.

A 64-year-old post-menopausal woman presented with dysuria, weakness and poor appetite that had lasted 3 months. A bilateral percutaneous nephrostomy (PCN) catheter was placed for bilateral hydroureteronephrosis at a local hospital, but malfunctioned due to blood clot formation. Physical examination revealed peritoneal signs. Laboratory test revealed leucocytosis, azotaemia with blood urea nitrogen (BUN) 93mg/dl, creatimine (Cr) 16.3mg/dl, and severe metabolic acidosis. Haemodialysis was initiated for uraemia. Computed tomography of the abdomen demonstrated the presence of ascites with peritoneal thickening in the lower peritoneal cavity, obstruction of the uterine outlet with intra-uterine fluid retention, tissue plane blurring between the uterine cervix and urinary bladder, and obstructive uropathy with the obstruction level at the bilateral uretero-vesical junction (Figures 1 and 2). Cervical cancer with pyometra was suspected and treated with dilation and curettage surgery, during which 150 c.c. of pus was drained out. Empiric antibiotics were given and sepsis resolved thereafter. A bilateral PCN catheter functioned well after repeated revisions. Haemodialysis was discontinued 3 weeks later (BUN 33mg/dl, Cr 2.8mg/dl). A biopsy of the cervix revealed squamous cell carcinoma with stromal invasion and the staging was IVA because of urinary bladder spreading. The patient recalled that she had suffered from intermittent vaginal spotting for the last 4 years, but had ignored it.