The clinical relevance of plasma CD147/basigin in biopsy-proven kidney diseases

Background

Precise understanding of kidney disease activity is needed to design therapeutic strategies. CD147/basigin is involved in the pathogenesis of acute kidney injury and renal fibrosis through inflammatory cell infiltration. The present study examined the clinical relevance of CD147 in biopsy-proven kidney diseases that lead to the progression of chronic kidney disease.

Methods

Kidney biopsy specimens and plasma and urine samples were obtained from patients with kidney diseases, including IgA nephropathy (IgAN), Henoch–Schönlein purpura nephritis (HSPN), diabetic kidney disease (DKD), focal segmental glomerulosclerosis (FSGS), and membranous nephropathy (MN), who underwent renal biopsy between 2011 and 2014. Plasma and urinary CD147 levels were measured and evaluated for their ability to reflect histological features. Disease activity of IgAN tissues was evaluated according to the Oxford classification and the Japanese histological grading system.

Results

In biopsy tissues, CD147 induction was detected in injured lesions representing renal inflammation. Plasma CD147 values correlated with eGFR in patients with inflammation-related kidney diseases such as IgAN, HSPN, and DKD. Particularly in IgAN patients, plasma CD147 levels were correlated with injured regions comprising more than 50% of glomeruli or with tubular atrophy/interstitial injury in biopsy tissues. Proteinuria showed a closer correlation with urinary values of CD147 and L-FABP. Of note, plasma and urinary CD147 levels showed a strong correlation with eGFR or proteinuria, respectively, only in DKD patients.

Conclusion

Evaluation of plasma and urinary CD147 levels might provide key insights for the understanding of the activity of various kidney diseases.

     

Increased Urinary Excretion of Monocyte Chemoattractant Protein-1 in Proteinuric Renal Diseases

Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that is produced mainly by tubular epithelial cells in kidney and contributes to renal interstitial inflammation and fibrosis. More recently, we have demonstrated that urinary MCP-1 excretion is increased in proportion to the degree of albuminuria (proteinuria) and positively correlated with urinary N-acetylglucosaminidase (NAG) levels in type 2 diabetic patients. Based on these findings, we have suggested that heavy proteinuria, itself, probably aggravates renal tubular damage and accelerates the disease progression in diabetic nephropathy by increasing the MCP-1 expression in renal tubuli. In the present study, to evaluate whether urinary MCP-1 excretion is increased in the proteinuric states not only in diabetic nephropathy but also in other renal diseases, we examined urinary MCP-1 levels in IgA nephropathy patients with macroalbuminuria (IgAN group; n = 6), and compared the results with the data obtained from type 2 diabetic patients with overt diabetic nephropathy (DN group; n = 23) and those without diabetic nephropathy (non-DN group; n = 27). Urinary MCP-1 excretion levels in non-DN, DN, IgAN groups were 157.2 (52.8–378.5), 346.1 (147.0–1276.7), and 274.4 (162.2–994.5) ng/g creatinine, median (range), respectively. Expectedly, urinary MCP-1 and NAG excretion levels in DN and IgAN groups were significantly elevated as compared with non-DN group. Therefore, we suggest that MCP-1 expression in renal tubuli is enhanced in proteinuric states, irrespective of the types of renal disease, and that increased MCP-1 expression probably contributes to renal tubular damage in proteinuric states.     

KIM-1 expression predicts renal outcomes in IgA nephropathy

Background

Kidney injury molecule-1 (KIM-1) is a sensitive biomarker for proximal tubular injury. Recently, a few studies have shown that urinary KIM-1 has clinical implications in IgA nephropathy (IgAN). We performed this study to determine whether tissue KIM-1 has clinical implications for predicting long-term outcome and whether urinary KIM-1 is correlated with tissue KIM-1 and kidney injury in IgAN patients.

Methods

We assessed the prognostic prediction capability of tissue KIM-1 expression in 69 adult patients with IgAN retrospectively. Renal biopsies from all patients were scored by a pathologist who was blinded to the clinical data for the pathologic variables. The primary outcome was the composite of a 50 % reduction in eGFR or end-stage renal disease. Tissue KIM-1 expression was assessed semiquantitatively by counting the stained tubules per 100× power field; 0 tubule indicates grade 0; 1–5 tubules, grade 1; 6–10 tubules, grade 2; and more than 10 tubules, grade 3. Comparing urinary KIM-1 and tissue KIM-1 expression, 50 consecutive IgAN patients were prospectively enrolled to measure urinary KIM-1 levels and examine their biopsy specimens by KIM-1 immunohistochemistry.

Results

Univariate analysis showed that tissue KIM-1 expression was associated with the renal outcome in IgAN. Multivariate regression analysis, as the relationship of tissue KIM-1 with prognosis, was consistent. Proteinuria at biopsy and tissue KIM-1 grade 3 were shown to have a prognostic value. The concentration of urinary KIM-1/Cr in patients with IgAN was significantly higher than that in the normal controls.

Conclusion

Tissue KIM-1 expression is an independent predictor of adverse renal outcomes in IgA nephropathy patients.     

Increased urinary excretion of monocyte chemoattractant protein-1 in proteinuric renal diseases

Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that is produced mainly by tubular epithelial cells in kidney and contributes to renal interstitial inflammation and fibrosis. More recently, we have demonstrated that urinary MCP-1 excretion is increased in proportion to the degree of albuminuria (proteinuria) and positively correlated with urinary N-acetylglucosaminidase (NAG) levels in type 2 diabetic patients. Based on these findings, we have suggested that heavy proteinuria, itself, probably aggravates renal tubular damage and accelerates the disease progression in diabetic nephropathy by increasing the MCP-1 expression in renal tubuli. In the present study, to evaluate whether urinary MCP-1 excretion is increased in the proteinuric states not only in diabetic nephropathy but also in other renal diseases, we examined urinary MCP-1 levels in IgA nephropathy patients with macroalbuminuria (IgAN group; n = 6), and compared the results with the data obtained from type 2 diabetic patients with overt diabetic nephropathy (DN group; n = 23) and those without diabetic nephropathy (non-DN group; n = 27). Urinary MCP-1 excretion levels in non-DN, DN, IgAN groups were 157.2 (52.8-378.5), 346.1 (147.0-1276.7), and 274.4 (162.2-994.5) ng/g creatinine, median (range), respectively. Expectedly, urinary MCP-1 and NAG excretion levels in DN and IgAN groups were significantly elevated as compared with non-DN group. Therefore, we suggest that MCP-1 expression in renal tubuli is enhanced in proteinuric states,irrespective of the types of renal disease, and that increased MCP-1 expression probably contributes to renal tubular damage in proteinuric states.     

Decreased urinary calbindin 1 levels in proteinuric rats and humans with distal nephron segment injuries

Background

Several proteins have been proposed as new urinary biomarkers of kidney injuries, but they are not always capable of identifying the kidney nephron segment that has been injured. Since calbindin 1 protein is exclusively localized in the kidney distal nephron segment, it is presumed that its expression is altered during distal nephron segment injuries, resulting in changes in its urinary excretion.

Methods

Calbindin 1 expression in normal rat kidneys was compared with that in the kidneys of rats that had suffered distal nephron segment injuries (unilateral ureteral obstruction [UUO] or anti-glomerular basement membrane glomerulonephritis [anti-GBM GN]) using immunohistochemical examinations and real-time polymerase chain reaction. The urinary calbindin 1 protein concentration of normal rats was also compared with that of anti-GBM GN rats and of cisplatin nephropathy rats using Western blotting. We also compared the kidney and urinary calbindin 1 protein concentrations of normal human subjects with those of proteinuric patients [immunoglobulin (Ig)A nephropathy; IgAN] with distal nephron segment injuries.

Results

Calbindin 1 mRNA expression in the renal cortices and calbindin 1 protein expression in the kidney distal nephron segments were decreased in the UUO and anti-GBM GN rat kidneys. The urinary calbindin 1 protein levels of the anti-GBM GN rats were also markedly decreased, whereas those of the cisplatin nephropathy rats were slightly decreased. The human IgAN patients displayed decreased renal calbindin 1 protein expression in their dilated distal tubules, and some patients displayed decreased urinary calbindin 1 levels.

Conclusion

Since it has been demonstrated that decreased urinary calbindin 1 levels are indicative of decreased calbindin 1 kidney expression due to distal nephron segment injuries, calbindin 1 might be a useful urinary biomarker for identifying distal nephron segment injuries.     

Fibrosis and evidence for epithelial-mesenchymal transition in the kidneys of patients with staghorn calculi

Study Type – Therapy (case control) Level of Evidence 2b What’s known on the subject? and What does the study add? It has been shown that patients with nephrolithiasis did not have normal kidney function (retrospective study). Renal inflammation and fibrosis have been shown in kidney biopsies of nephrolithiasis patients, particularly those with brushite and cystine stones. No pathological change in kidney biopsies of patients with idiopathical calcium oxalate stone is noted. Our cross‐sectional study of patients with large kidney stone formation (mostly staghorn stones) shows that the patients have reduced overall kidney function regardless of stone type, and robust signs of inflammation and fibrosis are observed in stone‐containing renal tissues. Reduced kidney function is closely associated with the degree of renal fibrosis. This is the first study demonstrating that renal tubular cells in stone‐baring kidneys are undergoing epithelial‐mesenchymal transition, and TGF‐β₁ is overproduced in these mesenchymalized cells.

OBJECTIVES

? To quantify fibrotic lesions in renal tissues obtained from patients with large calculi and to evaluate association with renal function. ? Presence of epithelial‐mesenchymal transition (EMT) in stone‐containing renal tissues was investigated.

PATIENTS, SUBJECTS AND METHODS

? In all, 50 patients with nephrolithiasis with large calculi and matched healthy controls (37) were recruited. ? Plasma creatinine (Cr) and corrected Cr clearance (CCr) were determined in all subjects. ? Of the 50 patients, 38 had renal tissue available for histological analysis. Fibrosis was assessed by Masson’s trichrome staining. Co‐expression of epithelial cytokeratins and mesenchymal markers [α‐smooth muscle actin (αSMA) and vimentin] in renal tubular cells was detected by dual immunofluorescence staining. ? Expression of fibronectin, transforming growth factor β₁ (TGF‐β₁) and CD68 were investigated.

RESULTS

? Overall, the kidney function of the patients was significantly reduced, indicated by increased plasma Cr and decreased corrected CCr compared with healthy controls. ? Inflammation grading in renal tissues of the patients was correlated with the percentage of the fibrotic area. Renal fibrosis was inversely correlated with renal function. ? Cytokeratins co‐expressed with αSMA and vimentin were found in nephrolithiatic renal tubular cells, and these cells strongly expressed fibronectin and TGF‐β₁. ? Infiltration of CD68‐positive cells was a common finding in the inflamed renal sections.

CONCLUSIONS

? Kidneys of large stone‐forming patients had robust signs of inflammation and fibrosis, and there was a close correlation of renal fibrosis with renal dysfunction. ? This is the first study to show evidence for renal tubular cells showing signs of EMT in large stone‐containing kidneys. Plausibly, TGF‐β₁ triggers EMT, which at least in part contributes to large stone‐induced renal fibrosis.     

Increased E-cadherin expression in the ligated kidney following unilateral ureteric obstruction

E-cadherin expression in the kidney is used as a surrogate marker of epithelial mesenchymal transition for the testing of various antifibrotic strategies. Here we reexamined E-cadherin expression in the kidneys of rats with unilateral ureteric obstruction, which was previously reported to decrease in parallel with the development of tubulointerstitial disease in this widely used experimental model of renal fibrosis and epithelial mesenchymal transition. E-cadherin mRNA expression was consistently increased both acutely (hours) and chronically (days) in the ligated kidney compared to the cognate non-ligated kidney. Increased E-cadherin protein levels were also found in the ligated kidney particularly in dilated tubular segments. Simulation of early pressure changes in the ligated kidney by mechanical stretch of human renal epithelial cells in culture did not alter E-cadherin expression. Porcine LLCPK-1 cells subjected to hypotonic stretch, however, did have increased E-cadherin mRNA and protein levels, responses that were not prevented by transforming growth factor-beta, a cytokine that promotes epithelial mesenchymal transition. Our findings question the utility of E-cadherin as a marker of epithelial mesenchymal transition in this model of renal fibrosis.     

伴足细胞尿的IgA肾病的临床病理特征

目的 探讨伴足细胞尿的IgA肾病（IgAN）患者的临床病理特点。方法 入选IgAN患者36例,其中男性20例,女性16例,平均年龄（34．1±12．2）岁。10例健康志愿者为健康对照。足细胞排泄的定量检测采用尿沉渣涂片免疫组化染色直接计数。进行尿液足细胞排泄与肾脏病理的相关分析。结果 （1）IgAN患者尿细胞podocalyxin阳性率为61%,健康对照组为0（P＜0．05）。（2）与非大量蛋白尿（＜3．0 g/24 h）IgAN患者比较,大量蛋白尿（≥3．0 g/24 h）IgAN患者的尿液足细胞检测阳性率、尿液足细胞排泄数、足细胞与尿肌酐的比值以及足细胞占尿液小管上皮细胞的百分数均显著增高（P＜0．05）。IgAN患者足细胞排泄水平与蛋白尿水平呈正相关（r=0．446,P=0．007）。（3）与无足细胞尿的患者比较,伴足细胞尿的IgAN患者的蛋白尿水平显著增高,血浆白蛋白水平显著降低,肾小管上皮细胞与尿肌酐的比值亦显著增高（P＜0．05）。但伴与不伴足细胞尿的2组IgAN患者在年龄、性别、血压、Scr、血红蛋白水平以及血浆脂质代谢等方面差异均无统计学意义（P＞0．05）。（4）尿足细胞的排泄与细胞新月体或细胞纤维性新月体、小球血管襻腔狭窄和足突广泛融合病变有关,而与系膜、内皮细胞病变及局灶基底膜增厚无关。伴足细胞尿的患者肾小球和肾小管间质纤维化更明显（P＜0．05）。伴有新月体的患者其尿液足细胞排泄水平、尿液上皮细胞和管型的排泄均增加（P＜0．05）。结论 足细胞尿不仅是IgAN患者肾小球损伤的结果,也是IgAN患者活动性损伤的指标。足细胞尿排泄的水平与蛋门尿水平呈正相关,与肾脏病理类型也有一定的关系。     

骨形成蛋白7和转化生长因子β1在不同病理类型IgA肾病的变化

目的 观察转化生长因子β1（TGF-β1）和骨形成蛋白7（BMP-7）在不同病理类型IgA肾病的变化,并探讨其意义。方法 89例IgA肾病患者分成3组：A组为47例轻度系膜增生性IgA肾病;B组为29例中重度系膜增生性IgA肾病;C组为13例增生硬化或硬化性IgA肾病。检测患者的血压、尿蛋白量（24 h）、Scr和Ccr。免疫组化和ELISA方法测定患者肾组织冰冻切片及其血、尿中TGF-β1和BMP-7水平。计算患者病理切片硬化肾小球数、新月体数和间质纤维化面积百分比。结果 随着IgA肾病患者肾小球病变的加重,肾小管萎缩和肾间质纤维化增多,其血压、尿蛋白量（24 h）、Scr逐渐增加,除B、C两组间尿蛋白量（24 h）无显著差异外,其余各组间差异均有统计学意义（P＜0．05）。与A组比较,B组肾组织及血、尿TGF-β1明显增多,C组显著降低（P＜0．01）。肾组织冰冻切片及血、尿BMP-7随着肾脏病变的加重,水平逐渐下降（P＜0．01）;而且与Ccr呈正相关;与血压、Scr、尿蛋白量（24 h）、硬化肾小球数、新月体数、肾间质纤维化面积呈负相关。结论 TGF-β1在IgA肾病系膜增生严重时明显增加,肾脏广泛纤维化时明显降低,可能参与了IgA肾病肾间质纤维化的发生。BMP-7随肾脏病变的加重而明显降低,可能导致其抗肾纤维化作用减弱。     

Clinical and pathological significance of circadian blood pressure rhythm change in IgA nephropathy patients with hypertension

Objective To investigate whether the clinical and pathological injury of kidney in IgA nephropathy (IgAN) patients with hypertension is associated with circadian blood pressure rhythm change, particularly with elevated nocturnal blood pressure (BP). Methods This study was a retrospective cross-sectional study. Clinic and renal histopathological injury data were obtained from 83 IgAN patients with hypertension. First, 24 h ambulatory BP monitoring (ABPM) data were analyzed. Second, all these IgAN patients were divided into two groups, elevated nocturnal BP group and nocturnal normotensive BP group, and the clinical and pathological differences between this two groups were analyzed. Third, logistic regression analysis was used to analyze the influencing factors of renal tubulointerstitial injury in IgAN patients with hypertension. At last, all these IgAN patients were divided into two groups according to the level of estimated glomerular filtration rate (eGFR), group of patients with eGFR≥60 ml?min-1?(1.73 m2)-1 and the other group with eGFR＜60 ml?min-1?(1.73 m2)-1, and the 24 h ABPM data were compared. Results (1) The proportion of non-dipper circadian rhythm of BP in IgAN patients with hypertension was 79.5%. (2) Compared with nocturnal normotensive BP group, patients in elevated nocturnal BP group had significantly higher levels of 24-hour urinary protein quantity and blood uric acid (both P＜0.05), and lower eGFR and urine osmotic pressure clinically (both P＜0.05). Index of interstitial fibrosis and tubular atrophy was significantly higher in nocturnal normotensive BP group (P＜0.05), while the proportion of glomerular ischemia lesion was not significantly different between two groups. (3) Multivariate logistic regression analysis showed that elevated nocturnal BP was an independent risk factor for severe tubulointerstitial injury of IgAN (OR=1.113, 95%CI 1.038-1.192, P=0.002). (4) Compared with the group of eGFR≥60 ml?min-1?(1.73 m2)-1, 24-hour systolic blood pressure (SBP) and diastolic blood pressure (DBP), daytime SBP and DBP, nocturnal SBP and DBP were significantly higher in group of eGFR＜60 ml?min-1?(1.73 m2)-1 (all P＜0.05). Conclusion The proportion of non-dipper circadian rhythm of BP in IgAN patients with hypertension is as high as 79.5%. Elevated nocturnal BP is associated with the severity of renal damage, and elevated nocturnal BP is an independent risk factor for severe tubulointerstitial injury in IgAN patients with hypertension. Therefore, 24 h ABPM should be emphasized, and elevated nocturnal BP should be well controlled to slow the progression of IgAN.     

In situ hybridization of connective tissue growth factor mRNA in IgA nephropathy

Connective tissue growth factor (CTGF) is a member of the new family of growth regulators. It plays an important role of the pathogenesis of mesangial matrix accumulation and progressive glomerulosclerosis in IgA nephropathy (IgAN).
We investigated the expression and localization of CTGF mRNA in renal tissues of patients with IgAN and normal human kidneys (NHK), using in situ hybridization with digoxigenin-labelled oligonucleotide. Open renal biopsy tissues were obtained from 16 patients with IgAN. The renal pathology was categorized into four grades by light microscopic findings. The expression level of CTGF mRNA was quantified by counting all nuclei, as well as nuclei surrounded by CTGF mRNA-positive cytoplasm in randomly selected non-sclerotic glomeruli and expressing the results as the percentage of total cells.
Connective tissue growth factor mRNA was mainly expressed in glomerular mesangial and epithelial cells in both IgAN and NHK, and cells of Bowman's capsule. In IgAN, CTGF mRNA-positive cells were increased in tubulointerstitial fibrotic areas. The percentage of positive cells for CTGF mRNA was significantly higher in IgAN than in NHK. The percentage of positive cells for CTGF mRNA in each IgAN grade was significantly higher than that in NHK. Furthermore, the percentage of positive cells for CTGF mRNA was significantly greater in IgAN with moderate mesangial proliferative lesions (grade 2, grade 3) than in IgAN with mild mesangial proliferative lesions.
Our study suggests that CTGF may play an important role in the development and progression of glomerulosclerosis and tubulointerstitial fibrosis in IgAN.     

Severity of nephrotic IgA nephropathy according to the Oxford classification

Background

IgA nephropathy with nephrotic syndrome (nephrotic IgAN) is a rare form of IgAN. Its prognosis and response to steroid therapy are still controversial because the differential diagnosis between nephrotic IgAN and minimal change nephrotic syndrome with IgA depositions is sometimes confused.

Methods

In this retrospective cohort analysis, we accurately diagnosed 42 cases of nephrotic IgAN (4.4%) from 954 IgAN patients, according to the Oxford classification. We analyzed the clinical and histological data, prognosis, and response to steroid therapy.

Results

In nephrotic IgAN, mean estimated glomerular filtration rate (eGFR) was 51.1?±?24.6?ml/min, proteinuria was 5.71?±?2.56?g/day, and urinary red blood cells were 51.0?±?37.8 high power field. Both active and chronic histological lesions were observed. Cumulative renal survival rate was significantly lower in nephrotic IgAN than in non-nephrotic IgAN (the control group consisted of 47 non-nephrotic IgAN patients diagnosed between 1995 and 1996) (log-rank test: P?Conclusion Nephrotic IgAN is a very severe form of IgAN, with renal dysfunction, massive hematuria, and active and chronic histopathological lesions. Renal outcome is severe; however, steroid therapy can improve prognosis in cases with higher eGFR and lower T-grade, according to the Oxford classification.     

Mechanisms of tubulointerstitial injury in IgA nephropathy

BACKGROUND: IgA nephropathy (IgAN) runs a highly variable clinical course, with frequent involvement of tubulointerstitial damage. A subgroup of IgAN with severe tubulointerstitial damage is often associated with the most rapid progression to end-stage renal failure. In IgAN, mesangial sclerosis and tubulointerstitial damage were found to be correlated with the increase in pore size of the glomerular barrier. METHODS: The direct toxicity of proximal tubular epithelial cells (PTEC) by IgA in IgAN is still unresolved. Activation of PTEC by mediators released from infiltrating cells or resident kidney cells that induce tubular inflammation is the common final pathway in most chronic renal diseases. We hypothesize that mediators released from human mesangial cells (HMC) triggered by IgA deposition may lead to PTEC activation. RESULTS: We found that IgA binding to PTEC was less than one tenth that of HMC. The binding was nonspecific and exhibited no increased cell proliferation or enhanced synthesis of cytokines or adhesion molecules. However, when PTEC were cultured with IgA-HMC spent medium prepared from IgAN patients, there was enhanced proliferation of PTEC and increased synthesis of cytokines and adhesion molecules. CONCLUSION: These findings implicate a glomerulotubular cross-talk with mediators released from the mesangium, contributing to the pathogenesis of tubulointerstitial damage in IgAN. There are preliminary data to suggest that the expression of angiotensin II subtype-1 receptor and angiotensin II subtype-2 receptor in PTEC differs from that of HMC. These novel findings may provide clinicians new therapeutic approach for selective blockade of the tubulointerstitial injury in IgAN.     

Severity of tubulointerstitial inflammation and prognosis in immunoglobulin A nephropathy

Many risk factors for progression in immunoglobulin A nephropathy (IgAN) have been found. We focused on renal leukocyte infiltrations and cytokines in IgAN. The subjects were 204 IgAN patients. Renal histopathological changes were semiquantitatively graded. Expression of tubulointerstitial Leukocyte common antigen (LCA), CD3, CD68, interleukin (IL)-1beta, and IL-10 was evaluated by immunohistochemistry. These parameters were correlated with progression of IgAN. The significance of these correlations was tested by a multivariate analysis. Glomerulosclerosis, tubular atrophy, interstitial inflammation, and hyaline arteriolosclerosis correlated with progression in all patients and also in patients with initially normal serum creatinine. Tubulointerstitial LCA, CD3, CD68, and IL-1beta expression correlated with progression. CD3 had the strongest correlation. In the multivariate analysis, tubulointerstitial CD3, hypertriglyceridemia, elevated serum creatinine concentration, and interstitial fibrosis were independently associated with progressive disease in all patients, and tubulointerstitial CD3 expression and hyaline arteriolosclerosis in patients with initially normal serum creatinine. We found parameters reflecting tubulointerstitial inflammation to predict deterioration of renal function in IgAN. This was also seen in patients whose serum creatinine was normal at the time of renal biopsy. Our findings show that, an immunohistochemical evaluation of tubulointerstitial inflammation seems to be a useful tool in determining the prognosis in IgAN.     

Tissue-specific expression of renin-angiotensin system components in IgA nephropathy

BACKGROUND: The renin-angiotensin II system (RAS) has been implicated in the development of glomerulonephritis. The aims of this study were to determine (1) the expression of RAS components, angiotensin (Ang II)-forming enzymes [angiotensin-I-converting enzyme (ACE) and chymase], and Ang II receptors, and (2) the correlation between RAS expression and severity of tissue injury in IgA nephropathy (IgAN). METHODS: The expression levels of ACE, chymase, and Ang II type 1 and type 2 receptor (AT1R and AT2R) mRNAs were determined by in situ hybridization in renal specimens from 18 patients with IgAN, 5 patients with non-IgA mesangial proliferative glomerulonephritis (non-IgAN) and 10 patients with nonmesangial proliferative glomerulonephritis (minimal change nephrotic syndrome, n = 5, and membranous nephropathy, n = 5). Normal portions of surgically resected kidney served as control. RESULTS: In normal kidney, a few mesangial cells and glomerular and tubular epithelial cells weakly expressed ACE, chymase and AT1R mRNAs. In IgAN and non-IgAN samples, ACE, chymase, AT1R and AT2R mRNAs were expressed in resident glomerular cells, including mesangial cells, glomerular epithelial cells and cells of Bowman's capsule. The glomerular expressions in IgAN were stronger than in minimal change nephrotic syndrome and membranous nephropathy. In IgAN, the expressions in glomeruli correlated with the degree of mesangial hypercellularity, whereas the expression levels were weaker at the area of mesangial expansion. IgAN with severe tubulointerstitial injury showed expression of ACE, chymase, AT1R and AT2R mRNAs in atrophic tubules and infiltrating cells and such expression correlated with the degree of tubulointerstitial damage. CONCLUSION: Our results suggest that renal cells can produce RAS components and that locally synthesized Ang II may be involved in tissue injury in IgAN through Ang II receptors in the kidney.     

Novel mechanisms of tubulointerstitial injury in IgA nephropathy: a new therapeutic paradigm in the prevention of progressive renal failure

IgA nephropathy (IgAN) runs a highly variable clinical course with frequent involvement of tubulointerstitial damage. Notably, renal progression correlates more closely with the severity of tubulointerstitial lesions than with the degree of glomerular lesions In IgAN. Mesangial IgA deposition induces local release of cytokines, complement, and angiotensin II leading to glomerular inflammation. It remains unclear how mesangial IgA deposition leads to tubulointerstitial injury in IgAN. Moreover, IgA deposits are rarely detected in renal interstitium in IgAN. We hypothesize that mediators released from mesangial cells triggered by IgA deposition leads to activation of proximal tubular epithelial cells. Our preliminary findings implicate a glomerulotubular cross talk with mediators released from the mesangium contributing to the pathogenesis of tubulointerstitial damage in IgAN. We have also found the expression of angiotensin II subtype-1 receptor or angiotensin II subtype-2 receptor in proximal tubular epithelial cells differs from that of mesangial cells. One potential therapeutic approach is to counterbalance the growth-stimulatory effects of angiotensin II through subtype-1 receptor in tubular epithelial cells by subtype-2 receptor-mediated apoptosis and growth inhibition. These novel findings may provide clinicians new therapeutic approach for selective blockade of the RAS in IgAN.     

Does circulating erythropoietin reflect progression of IgA nephropathy? Comparison with urinary N-acetyl-beta-D-glucosaminidase.

BACKGROUND: Recent reports describe that erythropoietin (Epo) is produced by peritubular interstitial fibroblast-like cells in response to a hypoxic stimulus. We studied serum Epo levels as a possible marker of tubulointerstitial damage in the progression of IgA nephropathy (IgAN), in comparison with urinary (u-) levels of N-acetyl-beta-D-glucosaminidase (NAG), which is mainly derived from proximal tubular cells and is used as a marker of tubular damage. METHODS: Thirty-eight patients with IgA nephropathy (IgAN) with relatively preserved renal function (serum creatinine: sCr, 0.5-2.2 mg/dl) were examined. The severity of glomerulosclerosis and interstitial fibrosis of the renal biopsy tissue was expressed by semiquantitative grading scores. Clinical parameters including serum creatinine (sCr), blood pressures, and 24-h proteinuria levels were obtained at the renal biopsy. Epo was measured by a radioimmunoassay (RIA) of sera obtained in the morning and u-NAG was measured by colorimetric method of 24-h urine samples. RESULTS: The mean Epo level of the patients (17.7+/-6.3 mU/ml) was not different from the control level (19.3+/-3.7 mU/ml). There were no significant correlations between Epo levels and red blood cell (RBC) counts, haematocrit (Hct), or haemoglobin (Hb) levels. The mean u-NAG level of the patients (6.7+/-6.2 U/gCr) was significantly higher than the control level (1.9+/-0.5 U/gCr). There was an inverse quantitative correlation between Epo and u-NAG levels in the patients (P<0.02). The u-NAG levels showed quantitative positive correlations with sCr (P<0.001), u-proteins (P<0.001), systolic (SBP) (P<0.001), and diastolic blood pressures (DBP) (P<0.05). Conversely, Epo levels were inversely correlated with sCr, SBP and DBP (each P<0.05). The patients with higher u-proteins (>2.0 g/day) showed significantly decreased Epo levels (P<0.05) than those with lower u-proteins (<2.0 g/day). The both scores of glomerulosclerosis and interstitial fibrosis were positively correlated with the u-NAG levels (each P<0.001), but were not correlated with the Epo levels. CONCLUSIONS: The significant correlation between u-NAG and serum Epo levels suggests that tubular damage and interstitial cell dysfunction are associated each other in the progression of IgAN. Serum Epo levels bearing inverse correlations with sCr, blood pressure levels and heavy proteinuria seem to reflect clinical severity of IgAN, whereas u-NAG can be more useful progression marker of IgAN bearing correlations with both clinical and histological findings.     

DelCFHR3-1 influences graft survival in transplant patients with IgA nephropathy via complement-mediated cellular senescence

IgA nephropathy (IgAN) is a frequent cause of chronic kidney disease (CKD) and progressive renal impairment. A native renal biopsy diagnosis of IgAN is a predictor of graft loss, with a relative risk of 47% but it is difficult to predict graft survival and progressive allograft dysfunction in these patients. Deletion of complement factor H-related genes 1 and 3 (delCFHR3-1) has been associated with a decreased risk of developing IgAN on native kidneys, but the impact on the graft in IgAN-transplanted patients is unknown. We hypothesized that delCFHR3-1 is also associated with the processes that influence graft survival in transplant recipients with IgAN and tested whether cellular senescence is involved in mediating graft damage. We found that patients carrying two copies of CFHR1-3 had a worse outcome (P = .000321) and presented increased FHR1 deposits at glomerular and tubulointerstitial level associated with higher expression of the senescence marker p16^INK4a (P = .001) and tubulointerstitial fibrosis (P = .005). Interestingly, FHR1 deposits were associated with increased complement activation as demonstrated by C5b-9 deposits. These data support both the role of FHR1 in mediating complement activation and tubular senescence, and suggest the possibility of genotyping delCFHR3-1 to predict graft survival in IgAN-transplanted patients.     

The complex of immunoglobulin A and uromodulin as a diagnostic marker for immunoglobulin A nephropathy

Background

The only tool to diagnose immunoglobulinn A nephropathy (IgAN) is renal biopsy which requires hospitalization; moreover, renal biopsy has a risk of critical bleeding. Therefore, a non-invasive method for accurate diagnosis of IgAN is desirable and a must-to-have tool for the clinics. For this purpose, we evaluated the diagnostic value of the IgA–uromodulin complex in the urine of patients with IgAN for its feasibility and adequacy.

Method

We determined the IgA–uromodulin complex as a candidate for a diagnostic marker of IgAN by immunoprecipitation, liquid chromatography?mass spectrometry (LC–MS) and Western blot analysis. The enzyme-linked immunosorbent assay (ELISA) for the IgA–uromodulin complex was developed and applied to urine samples obtained from various kidney disease patients.

Result

One hundred and three of 126 urine samples (81.7%) from IgAN patients were positive for the IgA–uromodulin complex, while only 25 out of 94 urine samples (26.6%) in other kidney disease patients were positive. Sensitivity was 81.7%, specificity was 73.4%, and diagnosis efficiency was 78.2%. The complex was negative in eight urine samples obtained from patients with Alport syndrome which is almost impossible to discriminate from IgAN by routine urinalysis.

Conclusion

Detection of the urinary IgA–uromodulin complex by ELISA is a useful non-invasive method to diagnose IgAN.     

TGF-beta1 and CTGF mRNAs are correlated with urinary protein level in IgA nephropathy

The degree of tubulointerstitial fibrosis is a poor prognostic indicator in IgA nephropathy (IgAN). Recently, connective tissue growth factor (CTGF) was observed to be strongly up-regulated in human proliferative and fibrogenic diseases. Renal biopsy specimens were obtained from the 20 patients with IgAN. Based on a previously reported study (MDRD study), all cases were categorized into 2 groups. Group A included patients with urinary protein (u-protein) <1.0 g/day, and group B, those with u-protein > or =1.0 g/day. Expressions of transforming growth factor beta1 (TGF-beta1) and CTGF mRNAs in tubular epithelial cells (TECs) were examined in all cases using rapid in situ hybridization (rISH). Significantly strong and diffuse expressions of TGF-beta1 and CTGF mRNAs were observed in proximal TECs in group B, while the expressions of these 2 mRNAs were weak in proximal TECs in group A and in glomerular resident cells in both groups. These results closely correlated with the degree of disorder in conventional pathohistological findings and clinical parameters except for u-protein level. The increase of u-protein level is one of the most important factors influencing the expression of TGF-beta1 and CTGF mRNAs in TECs. Therefore, the authors conclude that both u-protein level and expressions of these 2 mRNAs in TECs were significantly correlated with the degree of tubulointerstitial damage in IgAN.