Tubulointerstitial Damage Research Articles

MO070NEW ASPECTS OF THE PATHOMORPHOLOGIC SEQUENCE OF NEPHRON LOSS IN DIABETIC NEPHROPATHY

Abstract Background and Aims Diabetic nephropathy (DN) is the leading cause of end-stage-renal disease in western countries. Despite of innumerable studies undertaken to elucidate the pathogenesis of DN the underlying morphologic alterations have been insufficiently analyzed. Method Re-evaluation of more than 800 biopsies was done showing several unknown features. Results: 1. Matrix accumulation in the mesangium: Thickening of the glomerular basement membrane (GBM) and expansion of the mesangial matrix are hallmarks of DN, generally considered to emerge from different sites of overproduction: GBM components from podocytes and mesangial matrix from mesangial cells. We show, that the accumulation of matrix in the mesangium emerges from an overproduction of GBM material by podocytes and endothelial cells and an impaired degradation by mesangial cells. The progressing deposition of worn-out GBM material into the mesangium accounts for the advancement from diffuse mesangial sclerosis (DMS) to nodular sclerosis (NS) and to the herniation of the tuft through the glomerular vascular pole to the outside; the latter is associated with the outgrowth of glomerular capillaries into the peri-glomerular space leading to the destruction of the juxtaglomerular apparatus. 2.The role of podocytes Podocytes have frequently been accused to play a central role in DN. This is correct, but in another way than generally assumed. Damage to podocytes cannot be seen in DMS. The albuminuria regularly seen during this stage derives, as previously suggested by others, from an increased leakiness of the glomerular capillary endothelium based on a deranged glycocalyx. Podocyte detachments start at the transition from DMS to NS, based on the loss of cross talk signals with the capillary endothelium: the increasing deposition of matrix leads to the collapse of many capillaries. These podocytes contribute little to the further progression of the damage: they are lost into primary urine or they undergo cell lysis.In addition to their role in increased matrix production, podocytes take an active role in the formation of tuft adhesions to Bowman’s capsule (BC), starting the progression to NS. Expansion of the matrix within the mesangium has led to expansion of the tuft (frequently associated with nodules) towards Bowman’s capsule (BC) or towards the urinary orifice. Podocytes on the surface of these expansions are in their majority structurally intact, exhibiting an intact pattern of foot processes. These podocytes come into contact with parietal epithelial cells and initiate DN-specific tuft adhesions to BC allowing the proliferation of glomerular capillaries into BC. There they deliver an exudate into BC that spreads around the entire circumference of the glomerulus presenting as giant insudative spaces. Moreover, this process encroaches via the glomerulo-tubular junction onto the tubule constituting the major pathway of glomerular damage extending to the tubulointerstitium. 3. Tubulointerstitial fibrosisIt is current opinion that the tubulointerstitial fibrosis may start from tubular damage resulting in an own, glomerular-independent pathway to nephron loss. However, there is scant evidence for such a mechanism. Studying 162 glomerulo-tubular transitions, we did not see a tubular epithelial or interstitial damage in those biopsies without any evidence of a glomerulo-tubular damage transfer. The only exception consists of the well-known prominent thickening of the tubular basement membrane, which may result in functional loss but does not lead to structural epithelial damage. Conclusion We consistently found that tubulo-interstitial damage develops after encroachment of the glomerular damage onto the tubule, leading first to a gradual degeneration of tubules which subsequently initiate the process of interstitial fibrosis.

MO558ROLE OF ANEMIA ON PROGRESSION AND CLINICAL OUTCOMES OF CKD: A PATIENT-LEVEL, RETROSPECTIVE, COHORT ANALYSIS OF A CKD OUTPATIENTS POPULATION

Abstract Background and Aims Anemia is a well-know complication of Chronic Kidney Disease (CKD) and it seems to contribute for deterioration of kidney function. Experimental data suggest that anemia produces hypoxia of tubular cells which leads to tubulointerstitial damage resulting on CKD progression. Other mechanism described is that red blood cells have antioxidant properties that prevent the damage of tubulointerstitial cells and glomerulosclerosis from oxidative stress. There aren’t many observational studies that evaluated the association between anemia and progression of CKD. Therefore, our aim was to evaluate the association of anemia and CKD progression and its association outcomes in an outpatient ND-CKD population. Method We conduct a retrospective, patient-level, cohort analysis of all adult ND-CKD patients evaluated in an outpatient nephrology clinic over a 6 years period. The follow up time was at least 12 months. Anemia was defined according to the WHO definition (hemoglobin [hb] < 13.0 g/dL in men and 12.0 g/dL in women). Progression of CKD was defined by one of the following criteria: decline in eGFR (CKD-EPI) superior to 5 ml/min/1.73 m2/year; duplication of serum creatinine or the need renal replacement therapy. Demographics and clinical data were also accessed. Results Out of 3008 patients referred to the nephrology clinic, 49.9% had anemia (mean age 71.9±15.9 years; 50.4% male; 92% white; mean follow-up time of 2.3±1.2 years). The mean Hb was 11.8 ±1.9 g/dL. Important cardiovascular comorbidities in patients with anemia were arterial hypertension (86.7%), obesity (65.5%), Diabetes Mellitus (DM) (52%) and dyslipidemia (46%). In univariate analysis, mortality was associated with anemia (36.9 vs 13.0%, p<0.001), obesity (30.1 vs 21.8%, p<0.001) and DM (30.1 vs 21.1%, p<0.001). Of the patients with anemia, 738 met the criteria for CKD progression. In univariate analysis, CKD progression was associated with anemia (49.6 vs 43.9%, p=0.002), male gender (49.5 vs 43.6% p= 0.001); DM (49.6 vs 44.8 % p=0.009) and hypertension (47.9 vs 42.3% p=0.0018). In multivariate logistic regression analysis, anemia emerged was an independent predictor of CKD progression (OR 1.435, CI 95% 1.21-1.71, p<0,001). Comparing hb values intervals (hb ≤10g/dl; hb10-12 g/dL; hb ≥12 g/dL), in the multivariate logistic regression analysis, hb ≤10g/dl was not associated with CKD progression and hb value between 10-12 g/dL was associated (OR 1,486, CI 95% 1.23-1.80, p<0,001), when compared with the group with hb ≥12g/dL. In multivariate logistic regression analysis, the independent predictors of mortality were: older age (OR per 1 year increase: 1.048, 95% CI 95% 1.04-1.06, p<0.001); arterial hypertension (OR 0.699 CI 95% 0.51-0.96, p=0.0029); obesity (OR 0.741, CI 95% 0.60-0.91, p=0.004) and hb value (OR per 1 g/dL decrease: 1.301, CI 95% 1.23-1.38, p<0.001). Cardiovascular events were correlated with Hb levels between 10-12 g/dL (univariate analysis: OR 2.021, CI 95% 1.27-3.22, P=0.003), but not with the group with hb≤10 g/dL (univariate analysis: OR 1.837, CI 95% 0.96-3.51, P=0.066), having the group with hb ≥12g/dL was reference. Anemia was strongly associated with hospitalizations (multivariate logistic regression analysis: OR per 1 g/dL of Hb decrease: 1.256 CI 95% 1.12-1.32 p<0.001), and this strong association was also observed on the groups with hb hb≤10 g/dL (multivariate logistic regression analysis: OR 3.591 CI 95% 32.67-4.84 p<0.001) and between 10-12 g/dL (multivariate logistic regression analysis: OR 1.678 CI 95% 1.40-2.02, p<0.001) Conclusion Our study suggests that anemia, at first consultation, increases the risk for rapid CKD progression and global mortality. This study could guide us on the development of futures studies in order to prove if anemia correction can slow the progression of CKD.

Tubular cell damage may be the earliest sign of renal extrahepatic manifestation caused by Hepatitis C.

Chronic kidney disease (CKD) is one of the most well-known extrahepatic manifestations caused by hepatitis C infection (HCV). CKD is typically discovered at a late stage. HCV-nephropathy may show different histopathologic patterns, as both glomerular and tubulointerstitial damage have been described. Identification of patients with early renal manifestations would be beneficial to provide treatment and avoid progression to CKD. The observational prospective single-center HCVKID study assessed the prevalence of early renal manifestations in patients with chronic HCV and compared these patients with HCV-negative healthy controls cross-sectionally. HCV-positive patients with and without renal manifestations were also compared to define biomarkers suitable for identifying early manifestations in standard clinical practice. Tubular proteinuria as judged by urine α 1-microglobulin was the most common early renal manifestation found in 11% in HCV-positive patients, followed by hematuria in 8%. Kidney filtration was statistically significantly lower among HCV-positive patients with renal manifestation according to any calculation method. There were no significant differences in duration of infection or stage of liver fibrosis between patients with or without renal manifestations. Tubular cell damage may be the earliest sign of renal dysfunction caused by HCV. Complement activation also correlates with the dysfunction, indicating of contribution to HCV-induced renal manifestations even in their early phase.

Ophiocordyceps lanpingensis polysaccharides alleviate chronic kidney disease through MAPK/NF-κB pathway

Ethnopharmacological relevanceOphiocordyceps lanpingensis (O. lanpingensis) is a traditional ethno-medicine distributed in Eastern Himalayas, which has been used by local minorities to prevent and treat urinary diseases for hundreds of years. However, the corresponding active components and related pharmacological mechanism of such medication are not clear yet. Aims of the studyThis study was performed to investigate the effects and potential mechanisms of O. lanpingensis polysaccharides (OLP) in the treatment of chronic kidney disease (CKD) based on our previous research results. Materials and methodsMethylation analysis was used to investigate the monosaccharide composition and glycosidic linkages in OLP. The animals were divided into the control group, CKD model group, losartan group and three different doses of OLP groups. The CKD mouse model was established by the adenine gavage. The histological changes of renal tissue were observed by Hematoxylin-eosin and Masson staining. Biochemical indicators, including blood urea nitrogen (BUN), serum creatinine (Scr), serum phosphorus (P), plasma calcium (Ca), reactive oxygen species (ROS), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and malondialdehyde (MDA) were measured to evaluate the alleviation of CKD by OLP. Moreover, the expression levels of a series of cytokines related to the inflammation, apoptosis and fibrosis were analyzed to explore the possible mechanisms of OLP to treat CKD. ResultsOLP is composed of three kinds of monosaccharides. There are eight kinds of glycosidic linkages in OLP, among which →4)-Glcp-(1→ is the main linkage. OLP could significantly attenuate CKD in mice and the tubulointerstitial damage was recovered to almost normal after the treatment of OLP. Compared with the CKD model group, the levels of Scr, BUN, MDA, P in OLP treatment groups were significantly decreased; and the levels of SOD and Ca were increased after OLP treatment. Furthermore, OLP could reduce the oxidative stress of the renal tissues, decrease the expression levels of pro-inflammatory factors through TLR4-mediated MAPK and NF-κB pathway, inhibit the apoptosis of renal cells by MAPK pathway, and relieve the renal fibrosis by down-regulating the expression of TGF-β1. ConclusionsOLP is composed of three kinds of monosaccharides and →4)-Glcp-(1→ is the main glycosidic linkage in the polysaccharide. OLP could ameliorate CKD in mice by declining the oxidative stress, inflammation, apoptosis and fibrosis in the kidneys. The study provided some evidences for the potential application of OLP in alleviating CKD.

Assessment of New Protected Mechanism of Liraglutide on CKD Progression

Podocyte injury represents the main reason for proteinuria and renal disease in diabetic and non-diabetic patients. Recently Liraglutide as a GLP-1 analog is hypothesized to play a vital role in preventing kidney damage by anti-inflammatory and anti-apoptotic effect mechanisms. This study was established to evaluate the effect of Liraglutide on deterioration that happens with time in chronic kidney disease. 36 male Wister rats with a weight of 250-300 g were used in this study. All selected animals were examined and determined to be normal on general examination. Rats were divided into three groups (12rats/group): control group: negative control group injected normal saline I.P, induction group: single I.P dose (7.5 mg/kg) of doxorubicin for 14 days then administered 0.5ml/kg normal saline intraperitoneal for 28 days, and treatment group: single I.P dose (7.5 mg/kg) of doxorubicin for 14 days then administered I.P Liraglutide 200μg/kg/day freshly dissolve in 0.5ml /kg normal saline 28 days. The treatment group appeared significantly decreased (P< 0.05) in the pro-inflammatory expression of TNF-α as compared with the induction group, while the treatment group revealed a significant increased (P< 0.05) in the expression of anti-apoptotic BCL-2 in the proximal tubule of the kidney. Besides the effect of Liraglutide on renal deterioration by lowering blood glucose, the main causes of oxidative stress, Liraglutide as GLP-1 analog can reduce the consequence of proteinuria in the cases of glomerulosclerosis and tubulointerstitial damage by decreased pro-inflammatory TNF-α expression and increase expression of BCL-2 in that cell.

A Systematic Review of Renal Pathology in Chronic Kidney Disease of Uncertain Etiology

IntroductionDespite much research on chronic kidney disease of uncertain etiology (CKDu) in Sri Lanka and the Mesoamerican nephropathy, the etiology and pathogenesis of this disease remains elusive. The pathology has broadly been described as chronic tubulointerstitial nephritis and no specific signature lesions have been identified.MethodsA scoping review was conducted through MEDLINE and Google Scholar databases for peer-reviewed publications on biopsy studies related to CKDu – Sri Lanka and Mesoamerican nephropathy to develop a comparative and critical analysis of the renal pathology found in these patients.ResultsThirteen studies met the selection criteria. Interstitial fibrosis was the predominant lesion in all the studies. Tubulointerstitial and glomerular abnormalities showed a more variable distribution. No characteristic histopathological feature was reported other than a proximal tubular lysosomal inclusion body which was claimed to indicate a toxic etiology. Three main pathogenetic mechanisms were postulated: repeated acute insults leading to scarring, low-grade chronic insults leading to non-inflammatory fibrosis, and tubulointerstitial damage in combination with glomerular injury. The main limitations in the interpretation and comparative analysis of these studies were the heterogeneity in case selection and biopsy reporting.ConclusionsAlthough no characteristic histopathological feature could be found in CKDu–Sri Lanka or Mesoamerican nephropathy, there are noticeable differences between these two groups in the frequency and severity of the glomerular and tubulointerstitial changes which warrant more explorative studies preferably on kidneys in early stages of the disease. Future strategies should ensure that more uniform selection criteria and reporting methods are used.

Evaluation of renal tubulointerstitial damage as a residual renal risk factor for adverse cardiac events in patients with myocardial infarction

BackgroundRenal dysfunction, defined as a lower estimated glomerular filtration rate (eGFR), has been shown to be related to cardiovascular events in patients with myocardial infarction (MI). However, the contribution of renal tubulointerstitial damage to the predictive value for cardiovascular events has not been established. The aim of this study was to elucidate whether renal tubulointerstitial damage is associated with the occurrence of cardiac death and recurrence of MI in patients who have had MI. Methods and resultsUrinary β2-microglobulin (β2MG) was measured in 681 consecutive patients with MI in our hospital. All patients were followed up for <12 years or until the occurrence of cardiac death and MI. During a median follow-up period of 6 years, the cumulative cardiac death rate was 5.4%, and the MI rate was 3.1%. When outcomes were divided into two groups according to the β2MG levels, cardiac death and MI rates were lower in patients with lower levels of β2MG (<0.319 mg/gCre: determined by receiver operating characteristic analyses) than in those with β2MG ≥0.319 mg/gCre (5.9% versus 17.1%, p<0.01). When outcomes were stratified according to the β2MG levels in combination with eGFR levels, Kaplan-Meier analyses showed that cardiac death and MI rates increased depending on an increase in the β2MG levels (p<0.05). Moreover, multivariate Cox analyses revealed that high levels of β2MG were a significant independent predictor of adverse events (hazard ratio: 1.956; 95% confidence interval: 1.014–3.774; p = 0.045). The addition of high levels of β2MG to conventional risk factors, including eGFR and urinary albumin, improved the net reclassification improvement (NRI) and integrated discrimination improvement (IDI) (NRI 0.5447, p = 0.0002; IDI 0.0126, p = 0.0454). ConclusionRenal tubulointerstitial damage, as assessed by urinary β2MG, is associated with the occurrence of cardiac death and recurrence of MI independent of renal glomerular function in patients with MI.

BIOMARKERS OF GLOMERULAR FILTRATION, BUT NOT TUBULAR DYSFUNCTION, ARE ASSOCIATED WITH UNCONTROLLED HYPERTENSION IN THE GENERAL POPULATION. THE TROMSØ STUDY

Objective: Uncontrolled hypertension (UHT) and chronic kidney disease (CKD) are common and frequently overlapping entities with considerable health consequences. Little is known about the relationship between low-grade kidney dysfunction and UHT. The importance of tubular in contrast to glomerular dysfunction in cardiovascular disease and hypertension has been recognised, but tubular biomarkers have not been examined in population-based studies of UHT. We assessed the associations between biomarkers of low-grade kidney dysfunction and UHT in treated hypertensive individuals from a general population. Design and method: In a cross-sectional design, we included all participants of the Tromsø Study 2007–08, second visit, who reported the use of two ore more blood pressure (BP) lowering drugs. The cohort was dichotomised into controlled hypertension or UHT; UHT was defined as systolic BP &gt;=140 mmHg and/or diastolic BP &gt;=90 mmHg. We used logistic regression to examine the associations between cardiovascular risk factors and UHT. In multivariable models we added estimated glomerular filtration rate (eGFR), urate, two urinary biomarkers of glomerular dysfunction (albumin-creatinine ratio [U-ACR] and orosomucoid-creatinine ratio [U-OCR]) and one biomarker of tubular dysfunction (N-acetyl-beta -D-glucosaminidase -creatinine ratio [U-NAG-Cr]). Results: Of the 7308 participants, 1189 persons (mean age 68.0 [8.9] years), fulfilled the inclusion criterion. Among these, 65% had UHT. Subjects with UHT were older and more frequently non-smokers than subjects with controlled hypertension. They had lower eGFR and higher U-ACR and U-OCR, whereas the level of U-NAG-Cr was similar between the groups. In multivariable analyses, higher U-OCR was associated with UHT (OR 1.17; 95% CI 1.02, 1.34 per log unit), whereas U-NAG-Cr was not. U-ACR was significantly associated UHT in models that did not include U-OCR (OR 1.14; 95% CI 1.03, 1.25 per log unit ACR). Conclusions: Although tubulointerstitial function is important in BP regulation, and tubulointerstitial damage appears early in CKD, we found no independent association between U-NAG-Cr and UHT. However, biomarkers of glomerular dysfunction, including U-ACR and U-OCR, were independently associated with UHT in treated subjects from the general population. The cross-sectional design limits conclusions about cause and effect, and prospective studies should be undertaken.

Kappa light chain myeloma: A case report

Light chain myeloma nephropathy is the most common form of renal involvement in plasma cell dyscrasias. It usually causes tubulointerstitial renal damage. About one in five people with multiple myeloma produce only light chains. We report a case of lambda light chain deposition disease in a 61-year-old female who presented with acute renal failure . She is currently in partial remission following treatment with bortezomib, cyclophosphamide, and steroids.We present a case with rare kappa light chain myeloma with light chain deposition in renal tubules.

Spectrum of cancer patients receiving renal biopsy

The frontier of onco-nephrology, particularly renal complications of cancer and treatment, remains unexplored. We revisit the fundamental tool of diagnosing kidney disease, renal biopsy, in cancer patients with renal manifestation. Patients who received renal biopsy from July 2015 to July 2019 were analyzed. Primary outcomes included end-stage renal disease (ESRD), mortality, and catastrophic outcome defined as either ESRD or mortality. A Cox proportional hazards model and Kaplan-Meier technique were used to assess the association with outcome measurements and survival analyses. Immunosuppression after renal biopsy and response to the treatment were evaluated. Among the 77 patients, the median age was 66 years (interquartile range [IQR] 59-73 years) and 46 (59.7%) were male. At the time of renal biopsy, 57 patients (74%) had various degrees of renal insufficiency. Tubulointerstitial damage score, quantified by renal pathology, were associated with higher hazards of ESRD (hazard ratio [HR], 1.77; 95% confidence interval [95% CI], 1.20 to 2.61; P=0.004) and catastrophic outcome (HR, 1.30; 95% CI, 0.99 to 1.70; P=0.058). The response rate to immunosuppression was lower in those diagnosed with tubulointerstitial nephritis (1 of 4 patients, 25%) than those with glomerulopathy (10 of 20 patients, 50%). Renal biopsy may improve diagnostic accuracy and assist in treatment guidance of cancer patients with renal manifestation. Renal biopsy should be encouraged with clinical indication. Collaboration between oncologists and nephrologists is of paramount importance to provide more comprehensive care for caner patients.

MAMs Protect Against Ectopic Fat Deposition and Lipid-Related Kidney Damage in DN Patients.

Ectopic fat deposition (EFD) in the kidney plays a key role in the development of diabetic nephropathy (DN). Mitochondria-associated ER membranes (MAMs) are structures that connect to the endoplasmic reticulum (ER) and are involved in lipid metabolism. However, there are few studies on MAMs in the field of kidney disease, and the relationship between EFD and MAMs in DN is still unclear. In this study, increased EFD in the kidneys of DN patients was observed, and analysis showed that the degree of EFD was positively correlated with renal damage. Then, the MAMs were quantified by an in situ proximity ligation assay (PLA). The MAMs in the kidneys were found to gradually decrease through the different stages of DN, while the expression of ADRP (a marker of lipid droplets) and tubulointerstitial damage increased. Moreover, correlation analysis showed that the MAMs were negatively correlated with serum lipid levels, the EFD in the kidney and renal damage. Finally, we observed decreased expression of MAM-control proteins (DsbA-L, PACS-2, and MFN-2) in different stages of DN and they were associated with lipid deposition and renal damage. These data showed that the destruction of MAMs in DN might be the cause of EFD and interstitial damage in the kidney.

JUN Amino-Terminal Kinase 1 Signaling in the Proximal Tubule Causes Cell Death and Acute Renal Failure in Rat and Mouse Models of Renal Ischemia/Reperfusion Injury

Activation of the JUN amino-terminal kinase (JNK) pathway is prominent in most forms of acute and progressive tubulointerstitial damage, including acute renal ischemia/reperfusion injury (IRI). There are two forms of JNK expressed in the kidney, JNK1 and JNK2. Systemic administration of pan-JNK inhibitors suppresses renal IRI; however, the contribution of JNK1 versus JNK2, and the specific role of JNK activation in the proximal tubule in IRI, remains unknown. These questions were addressed in rat and mouse models of acute bilateral renal IRI. Administration of the JNK inhibitor, CC-930, substantially reduced the severity of renal failure, tubular damage, and inflammation at 24 hours in a rat IRI model. Next, Jnk1-/- mice, but not Jnk2-/- mice, were shown to be significantly protected against acute renal failure, tubular damage, and inflammation in the IRI model. Furthermore, mice with conditional Jnk1 deletion in the proximal tubule also showed considerable protection from IRI-induced renal failure, tubular damage, and inflammation. Finally, primary cultures of Jnk1-/-, but not Jnk2-/-, tubular epithelial cells were protected from oxidant-induced cell death, in association with preventing phosphorylation of proteins (receptor interacting serine/threonine kinase 3 and mixed lineage kinase domain-like pseudokinase) in the necroptosis pathway. In conclusion, JNK1, but not JNK2, plays a specific role in IRI-induced cell death in the proximal tubule, leading to acute renal failure.

Fucoidan Ameliorates Renal Injury-Related Calcium-Phosphorus Metabolic Disorder and Bone Abnormality in the CKD-MBD Model Rats by Targeting FGF23-Klotho Signaling Axis.

Background: Recently, chronic kidney disease (CKD)-mineral and bone disorder (MBD) has become one of common complications occurring in CKD patients. Therefore, development of a new treatment for CKD–MBD is very important in the clinic. In China, Fucoidan (FPS), a natural compound of Laminaria japonica has been frequently used to improve renal dysfunction in CKD. However, it remains elusive whether FPS can ameliorate CKD–MBD. FGF23-Klotho signaling axis is reported to be useful for regulating mineral and bone metabolic disorder in CKD–MBD. This study thereby aimed to clarify therapeutic effects of FPS in the CKD–MBD model rats and its underlying mechanisms in vivo and in vitro, compared to Calcitriol (CTR). Methods: All male rats were divided into four groups: Sham, CKD–MBD, FPS and CTR. The CKD–MBD rat models were induced by adenine administration and uninephrectomy, and received either FPS or CTR or vehicle after induction of renal injury for 21 days. The changes in parameters related to renal dysfunction and renal tubulointerstitial damage, calcium-phosphorus metabolic disorder and bone lesion were analyzed, respectively. Furthermore, at sacrifice, the kidneys and bone were isolated for histomorphometry, immunohistochemistry and Western blot. In vitro, the murine NRK-52E cells were used to investigate regulative actions of FPS or CTR on FGF23-Klotho signaling axis, ERK1/2-SGK1-NHERF-1-NaPi-2a pathway and Klotho deficiency. Results: Using the modified CKD–MBD rat model and the cultured NRK-52E cells, we indicated that FPS and CTR alleviated renal dysfunction and renal tubulointerstitial damage, improved calcium-phosphorus metabolic disorder and bone lesion, and regulated FGF23-Klotho signaling axis and ERK1/2-SGK1-NHERF-1-NaPi-2a pathway in the kidney. In addition, using the shRNA-Klotho plasmid-transfected cells, we also detected, FPS accurately activated ERK1/2-SGK1-NHERF-1-NaPi-2a pathway through Klotho loss reversal. Conclusion: In this study, we emphatically demonstrated that FPS, a natural anti-renal dysfunction drug, similar to CTR, improves renal injury-related calcium-phosphorus metabolic disorder and bone abnormality in the CKD–MBD model rats. More importantly, we firstly found that beneficial effects in vivo and in vitro of FPS on phosphorus reabsorption are closely associated with regulation of FGF23-Klotho signaling axis and ERK1/2-SGK1-NHERF-1-NaPi-2a pathway in the kidney. This study provided pharmacological evidences that FPS directly contributes to the treatment of CKD–MBD.

Angiotensin II type 1a receptor loss ameliorates chronic tubulointerstitial damage after renal ischemia reperfusion

We investigate whether suppressing the activation of the angiotensin II type 1a receptor (AT1a) can ameliorate severe chronic tubulointerstitial damage (TID) after renal ischemia reperfusion (IR) using AT1a knockout homozygous (AT1a−/−) male mice. To induce severe chronic TID after renal IR, unilateral renal ischemia was performed via clamping of the right renal pedicle in both AT1a−/− and wild-type (AT1a+/+) mice for 45 min. While marked renal atrophy and severe TID at 70 days postischemia was induced in the AT1a+/+ mice, such a development was not provoked in the AT1a−/− mice. Although the AT1a+/+ mice were administered hydralazine to maintain the same systolic blood pressure (SBP) levels as the AT1a−/− mice with lower SBP levels, hydralazine did not reproduce the renoprotective effects observed in the AT1a−/− mice. Acute tubular injury at 3 days postischemia was similar between the AT1a−/− mice and the AT1a+/+ mice. From our investigations using IR kidneys at 3, 14, and 28 days postischemia, the multiple molecular mechanisms may be related to prevention of severe chronic TID postischemia in the AT1a−/− mice. In conclusion, inactivation of the AT1 receptor may be useful in preventing the transition of acute kidney injury to chronic kidney disease.

Role of Human Mesangial-Tubular Crosstalk in Secretory IgA-Induced IgA Nephropathy

Background: IgA nephropathy (IgAN) is characterized by the mesangial deposition of pathogenic IgA. We previously detected the deposition of pathogenic secretory IgA (SIgA) in the mesangium of about one-third of IgAN patients. Tubulointerstitial injury has an important role in the development of IgAN. However, the relationship between SIgA and tubulointerstitial damage is currently unclear. In this work, the role of the mesangial-tubular crosstalk was explored in the tubulointerstitial damage in SIgA-induced IgAN. Methods: SIgA deposition in renal tissues of IgAN patients was detected by immunofluorescence. Flow cytometry was used to assess the binding of SIgA to human renal mesangial cells (HRMC) and human proximal tubule epithelial (HK-2) cells. HK-2 was co-cultured with HRMC added with SIgA isolated from patients or normal volunteers. Protein synthesis and gene expressions of TNF-α, TGF-β1, and MCP-1 were determined by ELISA and PCR, respectively. The expressions of the above cytokines in renal tissues of patients and normal controls were detected by immunohistochemistry. Results: Twenty-nine of 96 patients had SIgA deposition in the mesangium, but SIgA was rarely detected in the tubulointerstitium. The binding rate of SIgA to HK-2 (2.79%) was significantly lower than that of HRMC (81.6%) (p < 0.001). The expressions of TNF-α, TGF-β1, and MCP-1 in HRMC were significantly higher than in SIgA-stimulated HK-2 (p < 0.05), and their expressions were significantly higher in the SIgA-stimulated co-culture group compared with SIgA-stimulated HRMC (p < 0.05). The expressions of the above cytokines were mainly detected in tubulointerstitium of IgAN patients with positive and negative SIgA deposition, without significant difference between the 2 groups, but to a significantly higher level than that in normal controls, and their expressions positively correlated with tubulointerstitial injury. Conclusion: Inflammatory factors released from the mesangium after SIgA deposition might mediate tubulointerstitial damage via mesangial-tubular crosstalk in IgAN.

Metabolomics reveals the renoprotective effect of n-butanol extract and amygdalin extract from Amygdalus mongolica in rats with renal fibrosis

Renal fibrosis (RF) is a pathological process of progression from chronic kidney disease to end-stage renal disease. Amygdalus mongolica is a traditional Chinese medicine, and our previous studies demonstrated that the n-butanol extract (BUT) and amygdalin extract (AMY) from its seeds can prevent RF. However, the underlying mechanism remains unclear. The present study investigated the exact mechanism of the protective effect of A. mongolica on RF. A renal fibrosis rat model was induced with unilateral ureteral obstruction. Biochemical indicators were measured and combined with histopathology of renal tissue to evaluate the anti-RF effects. A serum metabonomic method was used to clarify the changes in the metabolic profile. The tubulointerstitial damage and fibrosis were significantly improved and metabolic perturbations were restored after treatment with BUT and AMY. Thirty-eight metabolites associated with RF progression and related to the regulation of arginine and proline metabolism, nicotinate and nicotinamide metabolism, and histidine metabolism were identified. They were restored to levels similar to those in controls after treatment. Moreover, no significant differences in efficacy were observed between the BUT and AMY groups. This study reveals and compares the potential mechanisms of the renoprotective effects after treatment with BUT and AMY from a metabolomic perspective.

Renal SPECT/CT with 99mTc-dimercaptosuccinic acid is a non-invasive predictive marker for the development of interstitial fibrosis in a rat model of renal insufficiency.

Chronic kidney disease (CKD) increases cardiovascular risk and mortality. Renal fibrosis plays a major role in the progression of CKD but, to date, histology remains the gold standard to assess fibrosis. Non-invasive techniques are needed to assess renal parenchymal impairment and to perform the longitudinal evaluation of renal structure. Thus we evaluated renal isotopic imaging by single-photon emission computed tomography/computed tomography (SPECT/CT) with technetium-99m (99mTc)-dimercaptosuccinic acid (DMSA) to monitor renal impairment during renal insufficiency in rats. Renal insufficiency was induced by an adenine-rich diet (ARD) at 0.25 and 0.5% for 28 days. Renal dysfunction was evaluated by assaying biochemical markers and renal histology. Renal parenchymal impairment was assessed by SPECT/CT isotopic imaging with 99mTc-DMSA on Days 0, 7, 14, 21, 28, 35 and 49. Compared with controls, ARD rats developed renal dysfunction characterized by increased serum creatinine and blood urea nitrogen, fibrosis and tubulointerstitial damage in the kidneys, with a dose-dependent effect of the adenine concentration. 99mTc-DMSA SPECT-CT imaging showed a significant decrease in renal uptake over time in 0.25 and 0.5% ARD rats compared with control rats (P = 0.011 and P = 0.0004, respectively). 99mTc-DMSA uptake on Day 28 was significantly inversely correlated with Sirius red staining evaluated on Day 49 (r = 0.89, P < 0.0001, R2 = 0.67). 99mTc-DMSA renal scintigraphy allows a longitudinal follow-up of risk of renal fibrosis in rats. We found that the reduction of renal parenchyma in ARD rats is inversely proportional to newly formed fibrous tissue in the kidney. Our results suggest that 99mTc-DMSA renal scintigraphy may be a useful non-invasive prognostic marker of the development of renal fibrosis in animals and should be tested in humans.

Therapeutic potential of human induced pluripotent stem cells and renal progenitor cells in experimental chronic kidney disease

BackgroundChronic kidney disease (CKD) is a global public health problem. Cell therapy using pluripotent stem cells represents an attractive therapeutic approach for the treatment of CKD.MethodsWe transplanted mitomycin C (MMC)-treated human induced pluripotent stem cells (hiPSCs) and renal progenitor cells (RPCs) into a CKD rat model system. The RPC and hiPSC cells were characterized by immunofluorescence and qRT-PCR. Untreated 5/6 nephrectomized rats were compared to CKD animals receiving the same amount of MMC-treated hiPSCs or RPCs. Renal function, histology, and immunohistochemistry were evaluated 45 days post-surgery.ResultsWe successfully generated hiPSCs from peripheral blood and differentiated them into RPCs expressing renal progenitor genes (PAX2, WT1, SIX2, and SALL1) and podocyte-related genes (SYNPO, NPHS1). RPCs also exhibited reduced OCT4 expression, confirming the loss of pluripotency. After cell transplantation into CKD rats, the body weight change was significantly increased in both hiPSC and RPC groups, in comparison with the control group. Creatinine clearance (CCr) was preserved only in the hiPSC group. Similarly, the number of macrophages in the kidneys of the hiPSC group reached a statistically significant reduction, when compared to control rats. Both treatments reduced positive staining for the marker α-smooth muscle actin. Histological features showed decreased tubulointerstitial damage (interstitial fibrosis and tubular atrophy) as well as a reduction in glomerulosclerosis in both iPSC and RPC groups.ConclusionsIn conclusion, we describe that both MMC-treated hiPSCs and RPCs exert beneficial effects in attenuating CKD progression. Both cell types were equally efficient to reduce histological damage and weight loss caused by CKD. hiPSCs seem to be more efficient than RPCs, possibly due to a paracrine effect triggered by hiPSCs. These results demonstrate that the use of MMC-treated hiPSCs and RPCs improves clinical and histological CKD parameters, avoided tumor formation, and therefore may be a promising cell therapy strategy for CKD.Graphical abstract

The sodium-glucose cotransporter 2 inhibitor tofogliflozin prevents diabetic kidney disease progression in type 2 diabetic mice.

Trials on cardiovascular and renal outcomes in patients with type 2 diabetes have consistently demonstrated that sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk of diabetic kidney disease (DKD) progression. However, their renal protective mechanisms have yet to be completely understood and the effect on albuminuria reduction in animal models is controversial. We investigated these issues using KK and KK-Ay mice as a control (CTRL) and as a model for type 2 diabetes (DKD), respectively. KK-Ay mice were treated with 0.015% tofogliflozin, which is an SGLT2 inhibitor, starting at seven weeks of age for eight weeks. Compared with the CTRL mice, the DKD mice had higher HbA1c levels and albuminuria. Although tofogliflozin treatment significantly lowered HbA1c levels, it did not reverse albuminuria. Tofogliflozin treatment enhanced damage in both the glomerular (i.e., enlarged mesangial area, increased foot process effacement rate, and decreased number of WT-1-positive cells) and tubulointerstitial (increased protein levels of KIM-1 and MCP-1, increased number of macrophages, and abnormal mitochondrial morphology) areas. Our results suggest that tofogliflozin may prevent glomerular and tubulointerstitial damage, partly by ameliorating hyperglycemia, renal inflammation, and abnormalmitochondrial morphology.

Normoalbuminuric Diabetic Kidney Disease- Need for Renal Biopsy? An Autopsy Study on Western Indian Population

Introduction: Persistent albuminuria and glomerular filtration rate are considered as the gold standard for the diagnosis of Diabetic Nephropathy (DN).&#x0D; Methods: In this autopsy study, we evaluated data from a cohort of 67 patients with Type 2 Diabetes Mellitus. We determined the histological prevalence of DN irrespective of the clinical manifestations of renal disease. Patients were stratified by proteinuria and estimated glomerular filtration rate(eGFR). The glomerular, interstitial and vascular lesions were scored as per the established histopathologic classification for DN.&#x0D; Results: 55 of the 67 patients had clinical as well as histological lesions consistent with DN. 12 patients had histological lesions of DN at autopsy but no clinical evidence of proteinuria, including microalbuminuria in their lifetime.4 of these patients had maintained eGFR. There was no difference in the glomerular lesions in patients with normoalbuminuria regardless of the eGFR. However,50% of the patients with low eGFR showed presence of interstitial fibrosis and tubular atrophy while no interstitial lesions were noted in patients with normoalbuminuria and maintained eGFR. Significant amount of arteriosclerosis was noted in the normoalbuminuric low eGFR patients. Haematuria was significantly associated with proteinuric low GFR patients.&#x0D; Conclusion: Histological evidence of DN may be seen even in the absence of clinical manifestations, suggesting that, in diabetic kidneys some amount of glomerular and tubulointerstitial damage has already occurred before the onset of proteinuria. Hence, there is a need for routine kidney biopsies in diabetic patients with normoalbuminuria. This will help in the timely diagnosis and appropriate management in the early stages of DN.