Progressive Glomerular Sclerosis Research Articles

Mitochondrial Dysfunction in Podocytes Caused by CRIF1 Deficiency Leads to Progressive Albuminuria and Glomerular Sclerosis in Mice.

Recent studies have implicated mitochondrial disruption in podocyte dysfunction, which is a characteristic feature of primary and diabetic glomerular diseases. However, the mechanisms by which primary mitochondrial dysfunction in podocytes affects glomerular renal diseases are currently unknown. To investigate the role of mitochondrial oxidative phosphorylation (OxPhos) in podocyte dysfunction, glomerular function was examined in mice carrying a loss of function mutation of the gene encoding CR6-interacting factor-1 (CRIF1), which is essential for intramitochondrial production and the subsequent insertion of OxPhos polypeptides into the inner mitochondrial membrane. Homozygotic deficiency of CRIF1 in podocytes resulted in profound and progressive albuminuria from 3 weeks of age; the CRIF1-deficient mice also developed glomerular and tubulointerstitial lesions by 10 weeks of age. Furthermore, marked glomerular sclerosis and interstitial fibrosis were observed in homozygous CRIF1-deficient mice at 20 weeks of age. In cultured mouse podocytes, loss of CRIF1 resulted in OxPhos dysfunction and marked loss or abnormal aggregation of F-actin. These findings indicate that the OxPhos status determines the integrity of podocytes and their ability to maintain a tight barrier and control albuminuria. Analyses of the glomerular function of the podocyte-specific primary OxPhos dysfunction model mice demonstrate a link between podocyte mitochondrial dysfunction, progressive glomerular sclerosis, and tubulointerstitial diseases.

Pathophysiology of diabetic kidney disease: impact of SGLT2 inhibitors.

Diabetic kidney disease is the leading cause of kidney failure worldwide; in the USA, it accounts for over 50% of individuals entering dialysis or transplant programmes. Unlike other complications of diabetes, the prevalence of diabetic kidney disease has failed to decline over the past 30 years. Hyperglycaemia is the primary aetiological factor responsible for the development of diabetic kidney disease. Once hyperglycaemia becomes established, multiple pathophysiological disturbances, including hypertension, altered tubuloglomerular feedback, renal hypoxia, lipotoxicity, podocyte injury, inflammation, mitochondrial dysfunction, impaired autophagy and increased activity of the sodium-hydrogen exchanger, contribute to progressive glomerular sclerosis and the decline in glomerular filtration rate. The quantitative contribution of each of these abnormalities to the progression of diabetic kidney disease, as well as their role in type 1 and type 2 diabetes mellitus, remains to be determined. Sodium-glucose co-transporter 2 (SGLT2) inhibitors have a beneficial impact on many of these pathophysiological abnormalities; however, as several pathophysiological disturbances contribute to the onset and progression of diabetic kidney disease, multiple agents used in combination will likely be required to slow the progression of disease effectively.

Thrombomodulin ameliorates transforming growth factor-β1–mediated chronic kidney disease via the G-protein coupled receptor 15/Akt signal pathway

Kidney fibrosis is the common consequence of chronic kidney diseases that inexorably progresses to end-stage kidney disease with organ failure treatable only with replacement therapy. Since transforming growth factor-β1 is the main player in the pathogenesis of kidney fibrosis, we posed the hypothesis that recombinant thrombomodulin can ameliorate transforming growth factor-β1-mediated progressive kidney fibrosis and failure. To interrogate our hypothesis, we generated a novel glomerulus-specific human transforming growth factor-β1 transgenic mouse to evaluate the therapeutic effect of recombinant thrombomodulin. This transgenic mouse developed progressive glomerular sclerosis and tubulointerstitial fibrosis with kidney failure. Therapy with recombinant thrombomodulin for four weeks significantly inhibited kidney fibrosis and improved organ function compared to untreated transgenic mice. Treatment with recombinant thrombomodulin significantly inhibited apoptosis and mesenchymal differentiation of podocytes by interacting with the G-protein coupled receptor 15 to activate the Akt signaling pathway and to upregulate the expression of anti-apoptotic proteins including survivin. Thus, our study strongly suggests the potential therapeutic efficacy of recombinant thrombomodulin for the treatment of chronic kidney disease and subsequent organ failure.

Novel Variant in COL4A5 Gene Associated with X-linked Alport Syndrome

Alport syndrome is an inherited disease of collagen IV leading to progressive glomerular sclerosis associated with variable degrees of proteinuria and haematuria, sensorineural deafness and ocular abnormalities. Here we describe a novel mutation involving the COL4A5 gene leading to X-linked Alport syndrome (XLAS) in a Singhalese family of six children born to nonconsanguineous parents of Sri Lankan origin.

P1839GLOMERULAR HYPERFILTRATION: THEORY AND APPLICATIONS

Abstract Background and Aims The role of glomerular hyperfiltration in the development and progression of diabetic and non-diabetic chronic kidney disease (CKD) was established during the 80’s of the last century and represented a paradigm shift in current nephrology practice. Method A web-based review of relevant bibliography: articles and textbooks, reporting the development of hyperfiltration theory and its clinical applications was conducted. Results In 1982, after a series of animal studies, Brenner and colleagues proposed that glomerular hyperfiltration, in diabetic and other glomerulopathies, contributes to intrarenal hypertension and predispose to progressive glomerular sclerosis and deterioration of renal function. Clinical trials during late 80’s and early 90’s then focused on inhibition of Renin Angiotensin Aldosteron system (RAAS) to reverse glomerular hyperfiltration, and suggested that ACE inhibitors can be anti-proteinuric independent of their blood pressure-lowering effect in non-diabetic and diabetic nephropathies. In 1993, a randomized controlled trial (RCT) by Lewis and colleagues proved a beneficial effect of captopril in patients with nephropathy caused by type 1 diabetes. Few years later, the results of Ramipril Efficacy in Nephropathy (REIN) study proved the renoprotective role of ACE inhibition in patients with non-diabetic nephropathies with nephrotic and non-nephrotic proteinuria in 2 Lancet articles in 1997 and 1999 respectively. The renoprotective role of RAAS inhibition with ARBs in patients with type 2 diabetes was proven in 3 RCTs published in the New England Journal of Medicine in 2001: Irbesartan in Patients with Type 2 Diabetes and Microalbuminuria (IRMA) Study, Irbesartan Diabetic Nephropathy Trial (IDNT), and Reduction of Endpoints in NIDDM with the Angiotensin II Antagonist Losartan (RENAAL) study. Dual blockade with an ACE inhibitor and an ARB was then attempted to further ameliorate glomerular hyperfiltration. Yet this approach was faced by an increased risk of hyperkalemia and acute kidney injury in 2 RCTs: the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) in 2008 and The Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) study in 2013. It was until 2014 when evidence appeared for a potential role of SGLT2 inhibition in attenuating glomerular hyperfiltration. The 1st clinical evidence of renoprotective effect of SGLT2i appeared in 2016 when the results of the EMPA-REG OUTCOME study found that empagliflozin was associated with lower rates of renal events. Subsequently, the Canagliflozin Cardiovascular Assessment Study (CANVAS) Program trials and the Dapagliflozin Effect on Cardiovascular Events–Thrombolysis in Myocardial Infarction 58 (DECLARE-TIMI 58) trial found similar reductions in composite renal endpoints. The Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) trial published in 2019 was the first study designed to assess the effects of a SGLT2i, canagliflozin, on renal outcomes in patients with type 2 diabetes and albuminuric CKD, and proved significant reduction in the composite renal outcome with canagliflozin. The potentiality for renoprotective role of SGLT2i in patients with non-diabetic CKD has stimulated a number of ongoing clinical trials: DIAMOND and Dapa-CKD using Dapagliflozin and EMPATHY and EMPA-KIDNEY using Empagliflozin. Conclusion The hyperfiltration theory represents the basis for current therapeutic interventions in diabetic and non-diabetic CKD. Current guidelines recommend using RAAS blockers in diabetic and non-diabetic proteinuric CKD and SGLT2i in patients with type 2 diabetes and CKD. Whether SGLT2i could be considered in patients with CKD independent of the diabetic state awaits the results of ongoing studies which might change the management practice of CKD.

The protective effect of Phellinus linteus decoction on podocyte injury in the kidney of FSGS rats

BackgroundThis study aimed to investigate the effect of the Phellinus linteus (Mesima) decoction on podocyte injury in a rat model of focal and segmental glomerulosclerosis (FSGS) and evaluate the potential mechanisms.MethodsFSGS resembling primary FSGS in humans was established in rats by uninephrectomy and the repeated injection of doxorubicin. The FSGS rats were randomly divided into the model group, low-dose group of P. linteus decoction (PLD-LD), medium-dose group of P. linteus decoction (PLD-MD), and high-dose group of P. linteus decoction (PLD-HD). Blood and urine analysis were performed after 12 weeks and the molecular indicators of renal function and the renal pathological changes were examined.ResultsFSGS developed within 12 weeks in the test group and showed progressive proteinuria and segmental glomerular scarring. Urinary protein, serum creatinine, urea nitrogen, triglycerides and cholesterol were significantly reduced following the 12-week intervention with P.linteus decoction, especially in the PLD-LD group. Renal nephrin and podocin were markedly increased. Moreover, the pathological damage in the renal tissue was alleviated by the PLD-LD intervention.ConclusionThe P. linteus decoction alleviated the podocyte injury in the FSGS rat model, thus minimizing the progression of glomerular sclerosis and improving renal function.

SUN-142 HYDROGEN SULFIDE INHIBITS ADRAMYCIN-INITIATED GLOMERULAR PODOCYTE INJURY VIA INTERFERENCE OF TRX/ASK1/P38 SIGNALING PATHWAY

Podocyte injury is an important factor contributing to the initiation and progression of glomerular sclerosis. It is implicated in a variety of renal diseases. Most of them are known to be caused by oxidative stress. It is, therefore, highly desirable to find more effective therapeutic approaches against oxidative podocyte injury. Hydrogen sulfide (H2S) is a gaseous mediator that has multi-faced biological activities. It also has antioxidative property. Here, we tested whether and how hydrogen sulfide affected oxidative podocyte injury.

Transcriptional Profile of Kidney from Type 2 Diabetic db/db Mice.

Diabetic nephropathy (DN), a common diabetic microvascular complication, is characterized by progressive glomerular sclerosis and tubulointerstitial fibrosis. However, the underlying mechanisms involved in DN remain to be elucidated. We explored changes in the transcriptional profile in spontaneous type 2 diabetic db/db mice by using the cDNA microarray. Compared with control db/m mice, the db/db mice exhibited marked increases in body weight, kidney weight, and urinary albumin excretion. Renal histological analysis revealed mesangial expansion and thickness of the basement membrane in the kidney of the db/db mice. A total of 355 differentially expressed genes (DEGs) were identified by microarray analysis. Pathway enrichment analysis suggested that biological oxidation, bile acid metabolism, and steroid hormone synthesis were the 3 major significant pathways. The top 10 hub genes were selected from the constructed PPI network of DEGs, including Ccnb2 and Nr1i2, which remained largely unclear in DN. We believe that our study can help elucidate the molecular mechanisms underlying DN.

Moxibustion Alleviates Injury in a Rat Focal Segmental Glomerulosclerosis Model.

Objectives To evaluate the therapeutic effects of moxibustion at Shenshu (BL-23) and Geshu (BL-17) acupoints in a focal segmental glomerulosclerosis (FSGS) model in rats. Methods A FSGS rat model was established by single nephrectomy and repeated injection of doxorubicin. The FSGS rats were randomly divided into the model group, losartan (positive control) group, Shenshu moxibustion group, and Geshu moxibustion group. Molecular indicators of kidney function and renal pathological changes were monitored. Results Urinary protein, serum creatinine, urea nitrogen, and serum uric acid were significantly reduced after 12-week intervention with losartan, Shenshu, or Geshu moxibustion. Renal α-SMA, FN, and TGF-β were also decreased, while podocin and nephrin protein and mRNA were increased. The pathological damage in renal tissue was obviously alleviated by all three treatments, which suggests that moxibustion may have similar efficacy to losartan in the treatment of FSGS. Conclusion Moxibustion alleviates podocyte injury and inhibits renal interstitial fibrosis in the FSGS rat model, thereby minimizing the progression of glomerular sclerosis and improving renal function.

Progenitor-like cells derived from mouse kidney protect against renal fibrosis in a remnant kidney model via decreased endothelial mesenchymal transition.

IntroductionPathophysiological changes associated with chronic kidney disease impair angiogenic processes and increase renal fibrosis. Progenitor-like cells derived from adult kidney have been previously used to promote regeneration in acute kidney injury, even though it remained unclear whether the cells could be beneficial in chronic kidney disease (CKD).MethodsIn this study, we established a CKD model by five-sixths nephrectomy and mouse kidney progenitor-like cells (MKPCs) were intravenously administered weekly for 5 weeks after establishing CKD. We examined the impact of MKPCs on the progression of renal fibrosis and the potential of MKPCs to preserve the angiogenic process and prevent endothelial mesenchymal transition in vivo and in vitro.ResultsOur results demonstrate that the MKPCs delayed interstitial fibrosis and the progression of glomerular sclerosis and ameliorated the decline of kidney function. At 17 weeks, the treated mice exhibited lower blood pressures, higher hematocrit levels, and larger kidney sizes than the control mice. In addition, the MKPC treatment prolonged the survival of the mice with chronic kidney injuries. We observed a decreased recruitment of macrophages and myofibroblasts in the interstitium and the increased tubular proliferation. Notably, MKPC both decreased the level of vascular rarefaction and prevented endothelial mesenchymal transition (EndoMT) in the remnant kidneys. Moreover, the conditioned medium from the MKPCs ameliorated endothelial cell death under hypoxic culture conditions and prevented TGF-β-induced EndoMT through downregulation of phosphorylated Smad 3 in vitro.ConclusionsMKPCs may be a beneficial treatment for kidney diseases characterized by progressive renal fibrosis. The enhanced preservation of angiogenic processes following MKPC injections may be associated with decreased fibrosis in the remnant kidney. These findings provide further understanding of the mechanisms involved in these processes and will help develop new cell-based therapeutic strategies for regenerative medicine in renal fibrosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0241-8) contains supplementary material, which is available to authorized users.

Glomerular Damage in Experimental Proliferative Glomerulonephritis Under Glomerular Capillary Hypertension

Background/Aims: Immunologically and hemodynamically mediated the destruction of glomerular architecture is thought to be the major causes of end-stage renal failure. The purpose of this study is to evaluate the effect of glomerular hypertension on glomerular injury and the progression of glomerular sclerosis after Thy-1 nephritis was induced. Method: Thy-1 nephritis was induced in the stroke-prone spontaneously hypertensive rat strain (SHR-SP) (group SP) and in age-matched Wistar-Kyoto (WKY) (group WKY) rats, following unilateral nephrectomy (UNX), and a vehicle was injected alone in UNX SHR-SP as control (group SC). Result: The degree of glomerular damage in response to a single dose of anti-thy-1 antibody, and its functional consequences (eg. proteinuria, diminished GFR) are more pronounced in group SP than normotensive group WKY and hypertensive group SC without mesangial cell injury. While normotensive group WKY rats recovered completely from mesangial cell injury on day 28-42, glomeruli in group SP kept on persistent macrophage infiltration, α-SMA expression on day 42-56. In addition, glomerular capillary repair with the GECs was rarely seen in pronouncedly proliferative and sclerostic areas. The incidence of glomerular sclerosis and the level of proteinuria were markedly increased by day 56 in the group SP. Conclusions: Our results demonstrate that glomerular hypertension aggravate glomerular damage and glomerulosclerosis in this model of Thy 1 nephritis.

A Decrease in Glomerular Endothelial Cells and Endothelial-mesenchymal Transition during Glomerulosclerosis in the Tensin2-deficient Mice (ICGN strain)

The ICR-derived glomerulonephritis (ICGN) mouse is a unique model of nephrotic syndrome, and albuminuria becomes evident in a neonatal stage, due to a genetic mutation of tensin2. We previously provided evidence that an apparent decrease in nephrin, caused by tensin2-deficiencient states, leads to podocytopathy, albuminuria and eventually, chronic renal failure. In general, glomerular endothelial cells (ECs) function as a barrier through tight attachment of glomerular basement membrane to podocytes, while decreased ECs can worsen renal failure. Nevertheless, it is still unknown whether glomerular ECs are altered under the tensin-2-deficient states during the manifestation of chronic renal failure. Herein, we examined the changes of glomerular ECs, with focus on the expression of PECAM-1 and VE-cadherin (EC-specific markers), or of α-SMA (myofibroblast marker) in this mouse model by histological methods. Compared with the non-nephrotic (+/nep) mice, the nephrotic (nep/nep) mice exhibited the reduced expression of PECAM-1, or of VE-cadherin, in glomerular area. Notably, some glomerular ECs showed the positive stainings for both PECAM-1 and α-SMA, suggesting endothelial-to-mesenchymal transition (EndoMT) during progression of glomerular sclerosis. This is the first report showing that a decrease in glomerular ECs, at least in part, via EndoMT is involved in tensin2-deficient pathological conditions.

Role of NADPH Oxidase-Mediated Reactive Oxygen Species in Podocyte Injury

Proteinuria is an independent risk factor for end-stage renal disease (ESRD) (Shankland, 2006). Recent studies highlighted the mechanisms of podocyte injury and implications for potential treatment strategies in proteinuric kidney diseases (Zhang et al., 2012). Reactive oxygen species (ROS) are cellular signals which are closely associated with the development and progression of glomerular sclerosis. NADPH oxidase is a district enzymatic source of cellular ROS production and prominently expressed in podocytes (Zhang et al., 2010). In the last decade, it has become evident that NADPH oxidase-derived ROS overproduction is a key trigger of podocyte injury, such as renin-angiotensin-aldosterone system activation (Whaley-Connell et al., 2006), epithelial-to-mesenchymal transition (Zhang et al., 2011), and inflammatory priming (Abais et al., 2013). This review focuses on the mechanism of NADPH oxidase-mediated ROS in podocyte injury under different pathophysiological conditions. In addition, we also reviewed the therapeutic perspectives of NADPH oxidase in kidney diseases related to podocyte injury.

The mitochondrial SIRT1–PGC-1α axis in podocyte injury

Dysfunction of mitochondria in podocytes is believed to be a trigger of injury and contributes to progressive glomerular sclerosis; however, the mechanisms had not been fully understood. Yuan et al. report involvement of SIRT1 (a homolog of the life-extending gene sir2 in mammals) and PPAR-γ coactivator 1α, a major regulator of oxidative metabolism, in mitochondria during podocyte injury. This information will be important in exploration of the mechanisms and future treatment of glomerular sclerosis.

Injection of Amniotic Fluid Stem Cells Delays Progression of Renal Fibrosis

Injection of amniotic fluid stem cells ameliorates the acute phase of acute tubular necrosis in animals by promoting proliferation of injured tubular cells and decreasing apoptosis, but whether these stem cells could be of benefit in CKD is unknown. Here, we used a mouse model of Alport syndrome, Col4a5(-/-) mice, to determine whether amniotic fluid stem cells could modify the course of progressive renal fibrosis. Intracardiac administration of amniotic fluid stem cells before the onset of proteinuria delayed interstitial fibrosis and progression of glomerular sclerosis, prolonged animal survival, and ameliorated the decline in kidney function. Treated animals exhibited decreased recruitment and activation of M1-type macrophages and a higher proportion of M2-type macrophages, which promote tissue remodeling. Amniotic fluid stem cells did not differentiate into podocyte-like cells and did not stimulate production of the collagen IVa5 needed for normal formation and function of the glomerular basement membrane. Instead, the mechanism of renal protection was probably the paracrine/endocrine modulation of both profibrotic cytokine expression and recruitment of macrophages to the interstitial space. Furthermore, injected mice retained a normal number of podocytes and had better integrity of the glomerular basement membrane compared with untreated Col4a5(-/-) mice. Inhibition of the renin-angiotensin system by amniotic fluid stem cells may contribute to these beneficial effects. In conclusion, treatment with amniotic fluid stem cells may be beneficial in kidney diseases characterized by progressive renal fibrosis.

Phosphate overload induces podocyte injury via type III Na-dependent phosphate transporter

Uptake of P(i) at the cellular membrane is essential for the maintenance of cell viability. However, phosphate overload is also stressful for cells and can result in cellular damage. In the present study, we investigated the effects of the transgenic overexpression of type III P(i) transporter Pit-1 to explore the role of extracellular P(i) in glomerular sclerosis during chronic renal disease. Pit-1 transgenic (TG) rats showed progressive proteinuria associated with hypoalbuminemia and dyslipidemia. Ultrastructural analysis of TG rat kidney by transmission electron microscopy showed a diffuse effacement of the foot processes of podocytes and a thickening of the glomerular basement membrane, which were progressively exhibited since 8 wk after birth. TG rats died at 32 wk of age due to cachexia. At this time, more thickening of the glomerular basement membrane and segmental sclerosis were observed in glomeruli of the TG rats. Immunohistochemical examination using anti-connexin 43 and anti-desmin antibodies suggested the progressive injury of podocytes in TG rats. TG rats showed higher P(i) uptake in podocytes than wild-type rats, especially under low P(i) concentration. When 8-wk-old wild-type and TG rats were fed a 0.6% normal phosphate (NP) or 1.2% phosphate (HP) diet for 12 wk, HP diet-treated TG rats showed more progressive proteinuria and higher serum creatinine levels than NP diet-treated TG rats. In conclusion, our findings suggest that overexpression of Pit-1 in rats induces phosphate-dependent podocyte injury and damage to the glomerular barrier, which result in the progression of glomerular sclerosis in the kidney.

Uremic toxicity of indoxyl sulfate.

Indoxyl sulfate, a uremic toxin, is accumulated in the serum of chronic kidney disease (CKD) patients. A part of the dietary protein-derived tryptophan is metabolized into indole by tryptophanase in intestinal bacteria. Indole is absorbed into the blood from the intestine, and is metabolized to indoxyl sulfate in the liver. Indoxyl sulfate is normally excreted into urine. In CKD, however, an inadequate renal clearance of indoxyl sulfate leads to its elevated serum levels. The oral adsorbent AST-120 reduces the serum levels of indoxyl sulfate by adsorbing indole in the intestines and stimulating its excretion into feces. I have proposed a protein metabolite theory by which endogenous protein metabolites such as indoxyl sulfate play a significant role in the progression of CKD. A progressive decline in the glomerular filtration rate leads to increased serum levels of endogenous protein metabolites such as indoxyl sulfate, and to the adverse effects of their overload on the remnant nephrons. Indoxyl sulfate stimulates progressive both tubulointerstitial fibrosis and glomerular sclerosis by increasing the expression of transforming growth factor-beta1, a tissue inhibitor of metalloproteinase-1 and proalpha1 (I) collagen, leading to a further loss of nephrons. AST-120 delays the progression of CKD by removing serum indoxyl sulfate. Moreover, indoxyl sulfate induces oxidative stress in tubular cells, mesangial cells, vascular smooth muscle cells, endothelial cells and osteoblasts as well as stimulating aortic calcification in hypertensive rats, it is also involved in the progression of CKD, cardiovascular disease (CVD) and osteodystrophy. Thus, the removal of indoxyl sulfate by AST-120 ameliorates the progression of not only CKD, but also of CVD and osteodystrophy.

Abnormalities in signaling pathways in diabetic nephropathy

Diabetic nephropathy (DN) is characterized by a plethora of signaling abnormalities that together ultimately result in the clinical and pathologic hallmarks of DN, namely progressive albuminuria followed by a gradual decline in glomerular filtration rate leading to kidney failure, and accompanied by podocyte loss, progressive glomerular sclerosis and, ultimately, progressive tubulointerstitial fibrosis. Over the past few years, the general understanding of the abnormalities in signaling pathways that lead to DN has expanded considerably. In this review, some of the important pathways that appear to be involved in driving this process are discussed, with special emphasis on newer findings and insights. Newer concepts regarding signaling changes in bradykinin, mTOR, JAK/STAT, MCP-1, VEGF, endothelial nitric oxide synthase, activated protein C and other pathways are discussed.

Localization of Tissue Transglutaminase (tTG) in Kidney of ICR-Derived Glomerulonephritis (ICGN) Mice

ICR-derived glomerulonephritis (ICGN) mice are a known inbred strain with hereditary nephrotic syndrome and are considered a good animal model of human idiopathic nephrotic syndrome. ICGN mice show proteinuria at a young age, and hypoalbuminemia, hyperlipidemia, anemia and edema accompanies their symptoms with aging. In addition, ICGN mice develop severe anemia with the progression of renal fibrosis similar to human chronic kidney disease (CKD). Recently, tissue transglutaminase (tTG) has been shown to be related to the renal fibrosis in several animal models and CKD patients. In the present study, we investigated the relationship between the progression of renal fibrosis and the localization of tTG in the kidneys using histochemistry and image analysis. Male ICGN mice aged 26-43 weeks were used. They were divided into two groups of early and terminal stages of renal fibrosis, based on plasma levels of blood urea nitrogen (BUN). Normal ICR males aged 11 weeks were used as a control group. tTG was localized to the interstitium in the normal ICR mice. In the early stage of renal fibrosis, the localization of tTG increased in renal tubules showing luminal dilation, as well as in the interstitium; however, the amount of tubular and interstitial tTG decreased in the late stage. In the glomeruli, tTG-immunoreactivity decreased in the late stage of renal fibrosis, despite the progression of glomerular sclerosis. The results suggest that epsilon(gamma-glutamyl) lysine cross-linking is not directly related to the progression of renal fibrosis in ICGN mice.

Reply to: Schreuder

reply: In aging male Wistar rats, renal injury develops spontaneously ([2][1]). It is gratifying that Dr. Schreuder is intrigued by our recent finding of a protective effect of early postnatal protein restriction (i.e., during lactation) on the spontaneous development of renal injury in male Wistar