[Secondary hyperuricemia in chronic renal failure promotes vascular calcification in rats].

The present study was aimed to explore the effects of hyperuricemia on vascular calcification in chronic renal failure (CRF) and the mechanisms. Adenine diet-induced CRF rat model was used. Twenty-three male 8-week-old Wistar rats were randomly divided into control group (Ctr, n = 5), CRF group (n = 8) and CRF plus allopurinol group (CRF + ALL, n = 10), and the rats were given standard diet plus standard drinking water, adenine diet plus standard drinking water and adenine diet plus allopurinol drinking for 6 weeks, respectively. Vascular calcification of abdominal aorta was identified by o-cresolphthalein complexone copper assay and Von Kossa staining. The mRNA expression levels of osteogenic/chondrogenic regulatory factors (Cbfα1, Msx2, Osx, and Sox9), vascular smooth muscle cell (VSMC) lineage markers (SM22a and Acta2) and calcification inhibitors (Mgp and Opn) were detected by real-time PCR. The results showed that the levels of serum phosphorus (Pi), urea nitrogen, creatinine and uric acid were significantly increased in the CRF rats, whereas allopurinol reversed the levels of serum urea nitrogen, creatinine and uric acid, except for serum Pi. The calcium content of rat abdominal aorta in the CRF group was significantly higher than that of the Ctr group (P < 0.05), but it was partially rescued in the CRF + ALL group (P < 0.05); Compared with the Ctr group, Cbfα1, Msx2, Osx and Sox9 mRNA levels of abdominal aorta in the CRF group were significantly up-regulated, while SM22a, Acta2, Mgp and Opn mRNA levels were down-regulated. In the CRF + ALL group, the changes of Msx2, Osx, SM22a and Opn mRNA levels were reversed (P < 0.05). Allopurinol had no effect on high Pi-induced VSMC calcification, and uric acid (6 and 7 mg/dL) significantly increased high Pi-induced VSMC calcification in vitro (P < 0.05). These results suggest that hyperuricemia in CRF may promote the osteoblast/chondrocyte-like cells differentiation of VSMC and further exacerbate vascular calcification.