High phosphorus level leads to aortic calcification via ß-catenin in chronic kidney disease.

AIMS: Vascular calcification is a risk factor for causing cardiovascular events and has a high prevalence among chronic kidney disease (CKD) patients. However, the molecular mechanism underlying this pathogenic process is still obscure. METHODS: Vascular smooth muscle cells (VSMCs) were induced by a concentration of phosphorus (Pi) of 2.5 mM, and were subjected to cell calcification analyses. The effect of high Pi on the Wnt/ß-catenin pathway was measured using a TOP/FOP-Flash reporter assay. The transcriptional regulation of ß-catenin on PIT1 (a type III sodium-dependent phosphate cotransporter) was confirmed by promoter reporter and chromatin immunoprecipitation assays. The 5/6 nephrectomized rat was used as an in vivo model and was fed a high Pi diet to induce aortic calcification. Serum levels of phosphate, calcium, creatine, and blood urea nitrogen were measured, and abdominal aortic calcification was examined. RESULTS: High Pi induced VSMC calcification, downregulated expression levels of VSMC markers, and upregulated levels of osteogenic markers. High Pi activated the Wnt/ß-catenin pathway and ß-catenin activity. ß-Catenin was involved in the process of high Pi-induced VSMC calcification. Further investigation revealed that ß-catenin transcriptionally regulated Pit1, a necessary player in VSMC osteogenic phenotype change and calcification. The in vivo study showed that ß-catenin was involved in rat abdominal aortic calcification induced by high Pi. When knockdown expression of ß-catenin in the rat model was investigated, we found that aortic calcification was reduced. CONCLUSION: These results suggest that ß-catenin is an important player in high phosphorus level-induced aortic calcification in CKD.

[Study on homologous bone marrow mesenchymal stem cells in repairing peri-tubular capillary cluster].

OBJECTIVE: To investigate the potential effect of homologous bone marrow mesenchymal stem cells (MSCs) on repairing peri-tubular capillary cluster (PTCC), and on improving renal tubular and mesenchymal hypoxia condition. METHODS: Monocyte was purified from bone marrow, amplified and identified as MSCs in vitro. Thirty female Wistar rats were randomly divided into 3 groups, the normal control group (Group A), MSCs transplanted group (Group B) and un-transplanted group (Group C). Rats in Group A was administered with drinking water by gastrogavage for 12 weeks, while those in Group B and C were administered with Aristolochia Decoction for 12 weeks to establish chronic aristolochic acid nephropathy (CAAN) model. At the end of the 12th week, 1 ml of MSCs was injected through caudal vein to the rats in Group B, while to those in Group A and C normal saline was injected instead. Blood, urine and kidney tissue of rats were collected at the end of the 16th week for examination, and their kidney tissue were made into serial section for determining the distribution of Y chromosome and CD34 double positive cells, and the pathological, immunohistochemical changes were observed using Western blotting and RT-PCR, etc. RESULTS: Y chromosome and CD34 double positive cells could be seen in MSCs transplanted renal tissue in group B. At the end of the 16th week, the PTCC density in Group C and B was (26.47 +/- 1.56)/ 0.13 mm2 and (5.26 +/- 0.78)/0.13 mm2 respectively, and the IOD value of hypoxia inducible factor-1alpha (HIF-1alpha) in them was (6.74 +/- 0.67) x 10(3) and (25 27 +/- 1.46) x 10(3) respectively, all showing significant difference between the two groups (P < 0.01). The content of CD34 was higher in Group B than that in Group C (P < 0.01). CONCLUSION: Homologous MSCs can enhance the vascular endothelial cells differentiation to repair the PTCC, thus to improve the renal tubular and mesenchymal hypoxia status.