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.

Roles of mycobacterium tuberculosis ESAT-6 in the development of renal injury.

OBJECTIVE: The present study was designed to evaluate the role of mycobacterium tuberculosis early secretory antigen target-6 (MtbESAT-6) in the development of renal injury. METHODS: PET42a (+) ESAT6 prokaryotic expression plasmid was constructed and the purified ESAT6 protein without endotoxin was obtained. Sixty healthy, clean, male Kunming mice were randomly divided into two groups: the experimental group (n = 30) and the control group (n = 30). Each mouse in the experimental group were injected with 0.5 ml ESAT-6 protein, and each mouse in the control group were injected with 0.5 ml sterile saline on the tail vein. Blood, urine and kidney tissues were collected. Serum creatinine (Scr), blood urea nitrogen (BUN), and urinary creatinine (Cr) were determined by HITACHI 7150 automatic biochemical analyzer and creatinine clearance rate (Ccr) was calculated. Renal tissues were conducted for hematoxylin-eosin (HE) staining and pathological scores of renal injury were recorded under the light microscope. RESULTS: Using MTB H37Ra strains genome DNA as template, the ESAT6 gene amplified by Hieff Pfu DNA Polymerase using polymerase chain reaction (PCR) technique was consistent with the expected size. PET42a (+) ESAT6 vector plasmid was successfully obtained and ESAT6 recombinant protein was successfully expressed with the protein concentration of 1.69 mg/ml. BUN and Scr in the experimental group were gradually increased, Ccr was gradually decreased, and the pathological score of renal injury increased gradually, and all of which were significantly higher than that in the control group after the experiment of 12 h, 24 h and 48 h (all P < 0.05). CONCLUSION: MtbESAT-6 might contribute to the development of renal injury.

VEGF genetic polymorphisms may contribute to the risk of diabetic nephropathy in patients with diabetes mellitus: a meta-analysis.

OBJECTIVE: This meta-analysis aimed to investigate a comprehensive and reliable conclusion on the correlations of single nucleotide polymorphisms (SNPs) in the vascular endothelial growth factor (VEGF) gene with the risk of diabetic nephropathy (DN) in patients with diabetes mellitus (DM). METHODS: We screened PubMed, Embase, Web of Science, Cochrane Library, CISCOM, CINAHL, Google Scholar, CBM, and CNKI databases for those relevant studies that investigated the association of 14,945 subjects with clinicopathological parameters in gastric cancer. RESULTS: Eleven case-control studies that met all inclusion criteria were included in this meta-analysis. A total of 14,945 subjects were involved, including 3,049 DN patients and 11,896 DM patients. Our meta-analysis results revealed that VEGF rs2010963 and rs3025039 polymorphisms might contribute to the risk of DN in DM patients. Ethnicity-stratified analysis suggested that VEGF genetic polymorphisms were associated with an increased risk of DN among Asians. However, we found no correlations of VEGF genetic polymorphisms with susceptibility to DN among Caucasians. CONCLUSION: Our findings suggest that VEGF rs2010963 and rs3025039 polymorphisms may contribute to the risk of DN in DM patients, especially among Asians. Thus, VEGF genetic polymorphisms could be useful biomarkers for early diagnosis of DN in DM patients.

Transplantation of endothelial progenitor cells in treating rats with IgA nephropathy.

BACKGROUND: Therapeutic options in IgAN are still limited. The aim of this study is to explore the feasibility of using endothelial progenitor cell to treat IgAN in rat model. METHODS: Rat bone marrow mononuclear cells (BM-MNCs) obtained with density gradient centrifugation were cultured in vitro, and induced into endothelial progenitor cells (EPCs). EPCs were identified by surface marker CD34, CD133 and VEGFR2 (FLK-1) and by Dil-Ac-LDL/FITC-UEA-1 double staining. EPCs were labeled with PKH26 prior to transplantation. Rat model of IgAN was established by oral administration of bovine serum albumin together with lipopolysaccharide via the caudal vein and subcutaneous injection of CCL4. Kidney paraffin sections were stained by H&E and PAS. Immunofluorescence was used to assess IgA deposition in the glomeruli. Peritubular capillary (PTC) density was determined by CD31 staining. Monocyte chemoattrant protein-1 (MCP-1), hypoxia-inducible factor-1α (HIF-1α) and CD105 were also measured by immunohistochemistry, western blotting and real-time fluorescent quantitative PCR. RESULTS: The transplanted BM-EPCs were successfully located in IgAN rat kidney. After transplantation, Urinary red blood cell, urine protein, BUN, Scr and IgA serum level were significantly decreased, so were the areas of glomerular extracellular matrix and the IgA deposition in the glomeruli. In addition, PTC density was elevated. And the expression levels of HIF-1α and MCP-1 were significantly down-regulated, while the expression of CD105 was up-regulated. All these changes were not observed in control groups. CONCLUSION: The BM-EPCs transplantation significantly decreases the expansion of glomerular extracellular matrix and the deposition of IgA in the glomeruli; lowers the expression of inflammatory factors; increases PTC density; improves ischemic-induced renal tissue hypoxia, all of which improves the renal function and slows the progress of IgA nephropathy.

The role of CD44-hyaluronic acid interaction in exogenous mesenchymal stem cells homing to rat remnant kidney.

BACKGROUND/AIMS: The aim of our study was to reveal the role of CD44-Hyaluronic acid (HA) in the homing and improving renal function of systemically transplanted MSCs in chronic renal failure. METHODS: First, a remnant kidney model was established in rats and the expression of HA was determined using immunohistochemistry (IHC) and western blotting. Next, chemotaxis assay using flow cytometry, and cell migration assay of MSCs were performed in vitro. Then, MSCs were transplanted into rats, thus, sprague-Dawley (SD) rats were randomly divided into sham group, 5/6 nephrectomy (5/6 Nx) group, MSC group and MSC/Anti-CD44 group (n = 8 for all groups). Migration of MSCs to the kidney in these rats was assessed by using cell tracking experiments, and tissue damage was evaluated by morphological analysis using Masson's trichrome staining and periodic acid Schiff staining. RESULTS: HA was significantly observed in 5/6 Nx group, but not in sham group. Meanwhile, HA was discovered induced MSCs migration remarkably (p < 0.05) and anti-CD44 antibody inhibited the migration significantly (p < 0.05) in vitro. In vivo, the GFP-MSCs were observed in MSC group and the cells reduced in MSC/Anti-CD44 groups, especially, in the tubulointerstitium. CONCLUSION: Our findings reveal that CD44-HA has the potential to induce MSCs homing to injured tissue, while its effect on the ability of MSCs, improving tissue function, is not significant.

Effect of losartan on the glomerular protein expression profile of type 2 diabetic KKAy mice.

BACKGROUND: To investigate the pathogenesis of diabetic nephropathy (DN) and to search for novel therapeutic targets, the glomerular protein expression profile of KKAy mice treated by losartan was analyzed by two-dimensional differential gel electrophoresis (2D-DIGE). METHODS: The eight-week-old KKAy mice were divided into the losartan treatment group and the non-treatment group, and C57BL/6 mice were used as the control group. After 12 weeks treatment, glomeruli were isolated by abdominal perfusion with magnetic beads, and the glomerular proteins were extracted. The glomerular protein expression profiles were investigated using 2D-DIGE and MALDI-TOF mass spectrometry. Western blot analysis was used to confirm the results of proteomics. RESULTS: Losartan treatment improved albuminuria and renal pathologic lesion of KKAy mice. A total of 62 glomerular proteins were differentially expressed between the KKAy losartan treatment mice and KKAy non-treatment mice. Among them, the expression of 28 proteins were up-regulated, including glycerokinase, sulfite oxidase, glycine amidinotransferase, and adenosylhomocysteinase. The expression of 13 proteins were down-regulated, including 3-mercaptopyruvate sulfurtransferase, ATP synthase subunit d, 60 kDa heat shock protein, and 75 kDa glucose-regulated protein(GRP75). A total of six proteins were found to be differentially expressed between the KKAy non-treatment mice and C57BL/6 mice glomeruli, and their differential expression was suppressed by losartan treatment, including mitochondrial ATP synthase subunit d, GRP75, and selenium-binding protein 1 et al. CONCLUSIONS: Treatment with losartan suppresses the differential expression of mitochondrial ATP synthase subunit d, GRP75, selenium-binding protein 1 etc. In diabetic KKAy mice glomeruli, may play a renoprotective role by reducing glomerular mitochondrial ROS genesis and inhibiting oxidative stress.

Isogenic mesenchymal stem cells transplantation improves a rat model of chronic aristolochic acid nephropathy via upregulation of hepatic growth factor and downregulation of transforming growth factor ß1.

Chronic aristolochic acid (AA) nephropathy (CAAN) caused by intake of AA-containing herbs is difficult to treat. We evaluated the therapeutic effect of bone marrow (BM) mesenchymal stem cells (MSCs) on a rat model of CAAN. Female Wistar rats were fed with decoction of Caulis Aristolochia manshuriensis by intragastric administration. MSCs were prepared from BM of male Wistar rats and injected into female CAAN rats through tail vein. Body weight, renal function, and urinary excretion of these CAAN rats were monitored before killing at the end of the 20th week. Blood, urine, and tissue samples were collected from experimental (MSC and non-MSC) and normal control groups. All animals developed renal fibrosis after 12 weeks of intake of AA-containing decoction. Fibrosis in the MSC groups was significantly reduced as examined with light and electron microscopy. Blood urea nitrogen, serum creatinine, and urine protein levels were significantly reduced and hemoglobin levels were improved in the MSC group as compared with the non-MSC group (p < 0.01). The expression of TGF-ß1 mRNA and protein was reduced but hepatic growth factor (HGF) was increased in the MSC group compared with the non-MSC group, but still higher than the normal control level as measured by immunochemical, RT-PCR, and western blotting assays (p < 0.01). The renal fibrosis of CAAN could be protected by isogenic MSC transplantation, probably via upregulation of HGF and downregulation of TGF-ß1.

Aristolochic acid induces apoptosis of human umbilical vein endothelial cells in vitro by suppressing PI3K/Akt signaling pathway.

AIM: To investigate whether aristolochic acid (AA) induced the apoptosis of human umbilical vein endothelial cells (HUVECs) in vitro and the underlying mechanism. METHODS: HUVECs were treated with AA (5, 10 or 20 µg/mL) for 12, 24 and 48 h. Cell viabilities were determined with MTT assay. Hoechst 33258 staining and flow cytometry were used to examine the apoptosis of HUVECs. Western blotting was used to evaluate Akt phosphorylation. Bcl-2 and Bax levels were measured using Western blotting and RT-PCR assays. RESULTS: Treatment of HUVECs with AA significantly decreased the cell viabilities in dose- and time-dependent manners. Morphological changes of apoptosis were observed in AA-treated cells. AA inhibited Akt activation, which was attenuated by pretreatment of the cells with LY294002 (20 µmol/L) or wortmannin (50 nmol/L). Furthermore, AA reduced Bcl-2 levels and increased Bax levels. CONCLUSION: AA induces apoptosis of HUVECs in vitro via the PI3K/Akt signaling pathway and by modulating the ratio Bcl-2 and Bax.

[Differentiation of mesenchymal stem cells into vascular endothelial cells in treatment of chronic aristolochic acid nephropathy: experiment with rats].

OBJECTIVE: To investigate the potentiality of mesenchymal stem cells (MSCs) to differentiate into vascular endothelia cells (ECs) in peritubular capillary (PTC) in chronic aristolochic acid nephropathy (CAAN). METHODS: MSCs were isolated from a male Wistar rat. The surface markers were identified with flow cytometry. Thirty female Wistar rats were randomly divided into 3 equal groups: Group A, perfused intragastrically with decoction of Caulis Aristolochiae manshuriensis for 12 weeks to establish CAAN models, Group B, perfused intragastrically with decoction of Caulis Aristolochiae manshuriensis for 12 weeks to establish CAAN models and injected with the MSCs by caudal vein in the 12th week, and Group C, perfused intragastrically with drinking water for 12 weeks and then injected with normal saline by caudal vein to be used as normal controls. At week 16, specimens of blood and urine were collected to detect the blood urea nitrogen (BUN), serum creatinine (Scr) and urine protein, and then the rats were killed with their kidneys taken out. Sex-determining region of the Y chromosome-fluorescence in situ hybridization (SRY-FISH) test with carboxyfluorescein (FAM)- was used to detect the cells originated from the source of the male donors. Immunohistochemistry was used to detect CD34, marker antigen pf EC. HE and Masson staining and electron microscope were used to observe the pathology of the kidney. Immunohistochemistry and RT-PCR were used to detect the expression of vascular endothelial growth factor (VEGF). Correlation analysis was conducted to study the relationships among these indices. RESULTS: Y chromosome and CD34 double positive cells could be seen in the renal tissue of Group B. At week 16, the density of PTC and integrated optical density of VEGF of Group A were (5.3 +/- 0.8)/0.13 mm2 and (2.8 +/- 0.4) x 10(3) respectively, both significantly lower than those of Group B [(26.5 +/- 1.6)/0.13 mm2 and (14.7 +/- 1.7) x 10(3) respectively, both P < 0.011]. The Scr and urine protein of Group A were significantly higher than those of Group B. The expression of VEGF mRNA of Group A was significantly lower than that of Group B. CONCLUSION: MSCs can differentiate into ECs. MSCs transplantation has beneficial effects on CAAN, which is possibly related with the reduction of PTC.

[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.

[Influence of hypoxia caused by impairment of peritubular capillary on the progression of chronic aristolochic acid nephropathy].

OBJECTIVE: To investigate the manifestation of impairment of peritubular capillary (PTC) in chronic aristolochic acid nephropathy (CAAN) and the influence of hypoxia caused by PTC impairment on the progression of CAAN. METHODS: Fifty-four Wistar rats were randomly divided into 2 groups: Group A (n = 30, perfused intragastrically with decoction of Caulis aristolochia manchuriensis for 8 weeks) and Group B (n = 24, perfused intragastrically with drinking water for 8 weeks). At weeks 8, 12, and 16 ten rats in Group A and 8 rats in Group B were killed. Specimens of blood and urine were collected before the killing of the rats to detect the blood urea nitrogen (BUN), serum creatinine (Scr), and urine protein. HE and Masson staining and microscopy were used to observe the pathology of the kidney. Immunohistochemistry and Western blotting were used to detect the expression of hypoxia-inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), and CD34. Correlation analysis was conducted to study the relationships among these indices. RESULTS: Since week 8 BUN, Scr, and urine protein of Group A began to increase in comparison with Group B (all P < 0.05). Pathological changes of the kidney began to appear in Group A since week 8 with the decrease of PTC density. HIF-1alpha was not expressed in Group B, and in Group A HIF-1alpha expression began to increase since week 8 and became significantly higher than that of Group B since week 12. At week 16, the PTC density and VEGF-IOD of Group A were 8.10 +/- 2.28/0.13 mm(2) and (2.78 +/- 0.78) x 10(3) respectively, both significantly lower than those of Group B [(42.80 +/- 4.49)/0.13 mm(2) and (26.49 +/- 9.34) x 10(3) respectively, both P < 0.01], and the HIF-1alpha-IOD of Group A was (7.11 +/- 1.20) x 10(3), significantly higher than that of Group B [(0.44 +/- 0.10) x 10(3), P < 0.01]. CD34 was highly expressed in Group B, and the CD34 expression of Group A began to decrease since week 16. HIF-1alpha expression was positively correlated with Scr (r = -0.945, P < 0/01), and PTC density and VEGF expression were negatively correlated with Scr (r = -0.907, P < 0.01 and r = -0.690, P < 0.01). PTC density was negatively correlated with HIF-1alpha expression (r = -0.880, P < 0.01). CONCLUSION: Severe hypoxia exists following PTC injury in CAAN. Hypoxia is correlated with the progression of CAAN.

Effects of prostaglandin E1 on the progression of aristolochic acid nephropathy.

OBJECTIVE: To investigate the effects of prostaglandin E1 (PGE1) on the progression of aristolochic acid nephropathy (AAN). METHODS: Twenty-four patients diagnosed as AAN with serum creatinine (Scr) between 1.5 mg/dL and 4 mg/dL during September 2001 to August 2003 were randomly divided into 2 groups. All patients had ingested long dan xie gan wan containing aristolochic acid (0.219 mg/g) for at least 3 months. Twelve patients were injected with Alprostadil (10 microg/d for 10 days in one month, summing up to 6 months). Except for PGE1, the other therapy was same in both groups. Renal function was assessed using reciprocal serum creatinine levels (1/Scr). RESULTS: The level of Scr an d serum hemoglobin (Hgb) was similar in both groups prior to therapy. During follow-up, 1/Scr levels in PGE1 group were significantly higher than control group (P < 0.01), and Hgb levels in PGE1 group were significantly increased compared with control (P < 0.05). CONCLUSION: PGE1 can slow the progression of renal failure and increase Hgb level of AAN patient.