Glomerular Collagen Research Articles

Effects of Dipeptidyl Peptidase-4 Inhibitor and Angiotensin-Converting Enzyme Inhibitor on Experimental Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease in the United States and worldwide. Proteinuria is a major marker of the severity of injury. Dipeptidyl peptidase-4 inhibitor (DPP-4I) increases incretin-related insulin production and is, therefore, used to treat diabetes. We investigated whether DPP4I could have direct effect on kidney independent of its hypoglycemic activity. We, therefore, tested the effects of DPP4I with or without angiotensin-converting enzyme inhibitor (ACEI) on the progression of diabetic nephropathy and albuminuria in a murine model of DKD. eNOS−/−db/db mice were randomized to the following groups at age 10 weeks and treated until sacrifice: baseline (sacrificed at week 10), untreated control, ACEI, DPP4I, and combination of DPP4I and ACEI (Combo, sacrificed at week 18). Systemic parameters and urine albumin–creatinine ratio were assessed at baseline, weeks 14, and 18. Kidney morphology, glomerular filtration rate (GFR), WT-1, a marker for differentiated podocytes, podoplanin, a marker of foot process integrity, glomerular collagen IV, and alpha-smooth muscle actin were assessed at the end of the study. All mice had hyperglycemia and proteinuria at study entry at week 10. Untreated control mice had increased albuminuria, progression of glomerular injury, and reduced GFR at week 18 compared with baseline. DPP4I alone reduced blood glucose and kidney DPP-4 activity but failed to protect against kidney injury compared with untreated control. ACEI alone and combination groups showed significantly reduced albuminuria and glomerular injury, and maintained GFR and WT-1+ cells. Only the combination group had significantly less glomerular collagen IV deposition and more podoplanin preservation than the untreated control. DPP-4I alone does not decrease the progression of kidney injury in the eNOS−/−db/db mouse model, suggesting that targeting only hyperglycemia is not an optimal treatment strategy for DKD. Combined DPP-4I with ACEI added more benefit to reducing the glomerular matrix.

Additional Value of Second Harmonic Generation Microscopy in the Diagnosis of Feline Collagen Type III Glomerulopathy

A 1.5-year-old neutered female Domestic Shorthair cat was euthanized after the diagnosis of end-stage protein-losing nephropathy associated with the onset of nephrotic syndrome. At necropsy, both kidneys were diffusely pale and swollen with a granular cortex. Histologically, glomeruli had diffuse global mesangial and capillary wall expansion by homogeneous pale eosinophilic material. This material was Congo red negative, blue with Masson's trichrome stain, weakly positive with periodic acid-Schiff stain, bright red with Picrosirius red and birefringent under polarized light. Transmission electron microscopy and second harmonic generation (SHG) microscopy revealed mesangial and subendothelial collagen fibril deposition. Type III collagen deposition was confirmed by immunohistochemistry. This study provides an original and complete description of feline collagen type III glomerulopathy and emphasizes the possibility of directly diagnosing glomerular collagen deposition on unstained slides through SHG microscopy.

Inhibition of suppressor of cytokine signaling-3 affects mesangial cell proliferation and cell cycle in mesangioproliferative glomerulonephritis.

To explore the role of suppressor of cytokine signaling-3 (SOCS-3) in mesangial proliferative glomerulonephritis (MsPGN). SOCS-3 expression in kidney tissues from MsPGN patients was detected using immunohistochemistry. Double immunofluorescence staining was performed to investigate the localization of SOCS-3 with α-SMA in glomeruli. Heminephrectomized wild-type (WT) and SOCS-3-/- (KO) mice were injected with Habu-snake venom (HSV) to establish MsPGN models, and renal function were compared. Simultaneously, immunofluorescence, periodic acid-Schiff staining, Picrosirius red staining, as well as immunohistochemistry for PCNA, MAC-2 and type IV collagen in glomeruli were performed. In addition, primary mouse renal mesangial cells and SV40 MES-13 cells were transfected with SOCS-3 siRNA or SOCS-3 lentiviral activation particles, followed by EdU assay, flow cytometry, quantitative reverse transcription-polymerase chain reaction, and Western blotting. Mesangial SOCS-3 expression was enhanced in glomeruli of MsPGN patients, and SOCS-3 was well co-localized with activated α-SMA. After HSV injection, WT and KO mice presented with the increases in the serum creatinine, urea nitrogen, and urinary protein, especially in KO mice. Besides, SOCS-3-/- alleviated the hyperplasia of glomerular MCs in MsPGN mice, with the reductions in PCNA, MAC-2, and collagen deposition. Furthermore, SOCS-3 inhibition reduced the cell proportion at S phase to suppress cell proliferation, with the downregulations of Cyclin A, Cyclin D1, PCNA, and Ki-67. SOCS-3 knockout can alleviate the hyperplasia of glomerular MCs in MsPGN mice via affecting the cell cycle and proliferation of MCs, thus being a potential therapeutic target for MsPGN.

Bovine serum albumin aggravates macrophage M1 activation and kidney injury in heterozygous Klotho-deficient mice via the gut microbiota-immune axis.

Klotho expression abnormalities induces kidney injury and chronic kidney disease, however, the underlying mechanism remains unclear. Here, Klotho+/- mice and wild-type mice were treated with low-dose bovine serum albumin (BSA). Pathological examination demonstrated that the area of glomerular collagen deposition and fibrosis in BSA-Kl-/+ mice was significantly larger than that in BSA-WT mice. The serum levels of superoxide dismutase, malondialdehyde, creatinine, and urea in BSA-Kl-/+ mice were significantly increased. Sequencing of gut microbiota 16S rRNA v3-v4 region indicated that BSA-Kl-/+ mice showed a significantly higher relative abundance of the genera Dubosiella, Akkermansia, Alloprevotella, and Lachnospiraceae and a significantly lower relative abundance of the genera Allobaculum and Muribaculaceae than BSA-WT mice. KEGG analysis revealed that the metabolic pathways of signal transduction, xenobiotic biodegradation and metabolism, and lipid metabolism increased significantly in BSA-Kl-/+ mice. Flow cytometry showed that the proportion of CD68+/CD11b+ cells in the peripheral blood was significantly higher in BSA-KL-/+ mice than that in BSA-WT mice. qPCR and western blot suggested that Klotho and Nrf2 expression in MΦ1 cells of BSA-KL-/+ mice was significantly decreased. Thus, the findings suggest during the immune activation and chronic inflammation induced by the gut microbiota imbalance in Klotho-deficient mice treated to BSA, disrupted expression of proteins in the Nrf2/NF-κB signaling pathway in monocyte-derived macrophage M1 cells leads to the aggravation of inflammation and kidney injury.

Non-purine selective xanthine oxidase inhibitor ameliorates glomerular endothelial injury in InsAkita diabetic mice.

Endothelial dysfunction represents a predominant early feature of diabetes, rendering patients with diabetes prone to renal complications, e.g., proteinuria. Recent studies have indicated a possible role for xanthine oxidase (XO) in the pathogenesis of vascular dysfunctions associated with diabetes. In the present study, we investigated the contribution of XO activation on the progression of diabetic nephropathy in a mouse model using selective XO inhibitors. Male Ins2Akita heterozygous mice were used with wild-type mice as controls. Akita mice were treated with topiroxostat (Topi) or vehicle for 4 wk. Serum uric acid levels were significantly reduced in Akita + Topi mice compared with Akita + vehicle mice. The Akita + Topi group had a significant reduction in urinary albumin excretion compared with the Akita + vehicle group. Mesangial expansion, glomerular collagen type IV deposition, and glomerular endothelial injury (assessed by lectin staining and transmission electron microscopy) were considerably reduced in the Akita + topi group compared with the Akita + vehicle group. Furthermore, glomerular permeability was significantly higher in the Akita + vehicle group compared with the wild-type group. These changes were reduced with the administration of Topi. We conclude that XO inhibitors preserve glomerular endothelial functions and rescue compromised glomerular permeability, suggesting that XO activation plays a vital role in the pathogenesis of diabetic nephropathy.

Impact of sex on diabetic nephropathy and the renal transcriptome in UNx db/db C57BLKS mice.

Diabetic nephropathy (DN) is associated with albuminuria and loss of kidney function and is the leading cause of end‐stage renal disease. Despite evidence of sex‐associated differences in the progression of DN in human patients, male mice are predominantly being used in preclinical DN research and drug development. Here, we compared renal changes in male and female uninephrectomized (UNx) db/db C57BLKS mice using immunohistochemistry and RNA sequencing. Male and female UNx db/db mice showed similar progression of type 2 diabetes, as assessed by obesity, hyperglycemia, and HbA1c. Progression of DN was also similar between sexes as assessed by kidney and glomerular hypertrophy as well as urine albumin‐to‐creatinine ratio being increased in UNx db/db compared with control mice. In contrast, kidney collagen III and glomerular collagen IV were increased only in female UNx db/db as compared with respective control mice but showed a similar tendency in male UNx db/db mice. Comparison of renal cortex transcriptomes by RNA sequencing revealed 66 genes differentially expressed (p < .01) in male versus female UNx db/db mice, of which 9 genes were located on the sex chromosomes. In conclusion, male and female UNx db/db mice developed similar hallmarks of DN pathology, suggesting no or weak sex differences in the functional and structural changes during DN progression.

Establishing equivalent diabetes in male and female Nos3-deficient mice results in a comparable onset of diabetic kidney injury.

Clinical studies indicate that sex differences exist in susceptibility for developing diabetic kidney disease (DKD), supporting the need to examine both sexes in animal studies of DKD. Streptozotocin (STZ) is commonly used in male mice to induce diabetes and DKD. However, females are not normally included because their sex hormones partially protect them from STZ‐induced islet injury and consequent diabetes. To address this issue, we identified a strategy to induce comparable diabetes in male and female mice using STZ and determined whether both sexes develop equivalent renal injury. Male and female mice lacking the gene for endothelial nitric oxide synthase (Nos3‐/‐) were made diabetic with five or six low‐dose STZ injections, respectively. Groups of male and female mice with equivalent hyperglycemia at week 3 after STZ were assessed for DKD at week 8. STZ‐treated male and female Nos3‐/‐ mice maintained comparable hyperglycemia between weeks 3 and 8 had an equivalent increase in HbA1c levels and comparable hypertension. Urine albumin/creatinine levels were elevated eightfold in mice of both sexes at week 8, accompanied by an equivalent loss of podocytes. In diabetic males and females, plasma cystatin C levels and glomerular collagen deposition were similarly increased. Kidney mRNA levels of proinflammatory and profibrotic markers and kidney injury molecule‐1 (KIM‐1) were equally elevated in males and females, indicating comparable kidney injury. This study shows that equivalent diabetes induces a comparable onset of DKD in male and female Nos3‐/‐ mice, demonstrating that it is possible to include males and females together in studies of DKD.

Glomerular Collagen Deposition and Lipocalin-2 Expression Are Early Signs of Renal Injury in Prediabetic Obese Rats.

Feeding rats with high-fat diet (HFD) with a single streptozotocin (STZ) injection induced obesity, slightly elevated fasting blood glucose and impaired glucose and insulin tolerance, and caused cardiac hypertrophy and mild diastolic dysfunction as published before by Koncsos et al. in 2016. Here we aimed to explore the renal consequences in the same groups of rats. Male Long-Evans rats were fed normal chow (CON; n = 9) or HFD containing 40% lard and were administered STZ at 20 mg/kg (i.p.) at week four (prediabetic rats, PRED, n = 9). At week 21 blood and urine samples were taken and kidney and liver samples were collected for histology, immunohistochemistry and for analysis of gene expression. HFD and STZ increased body weight and visceral adiposity and plasma leptin concentration. Despite hyperleptinemia, plasma C-reactive protein concentration decreased in PRED rats. Immunohistochemistry revealed elevated collagen IV protein expression in the glomeruli, and Lcn2 mRNA expression increased, while Il-1β mRNA expression decreased in both the renal cortex and medulla in PRED vs. CON rats. Kidney histology, urinary protein excretion, plasma creatinine, glomerular Feret diameter, desmin protein expression, and cortical and medullary mRNA expression of TGF-β1, Nrf2, and PPARγ were similar in CON and PRED rats. Reduced AMPKα phosphorylation of the autophagy regulator Akt was the first sign of liver damage, while plasma lipid and liver enzyme concentrations were similar. In conclusion, glomerular collagen deposition and increased lipocalin-2 expression were the early signs of kidney injury, while most biomarkers of inflammation, oxidative stress and fibrosis were negative in the kidneys of obese, prediabetic rats with mild heart and liver injury.

494-P: Whole-Kidney 3D Imaging and Image Analysis Enables Detailed Quantification of Diabetic Nephropathy Features in the Uninephrectomized db/db Mouse Model

Diabetic nephropathy (DN) is a serious complication of diabetes and the leading cause of end-stage renal disease. To reproducibly test novel therapies, there is a need for precise quantification of DN pathology in rodent models. We compared the accelerated development of DN in male and female uninephrectomized db/db mice using advanced imaging techniques. Unilateral nephrectomy (UNx) was performed in 7-8 weeks old male and female db/db mice. Sham-operated db/+ mice served as controls. Kidneys were preserved for histology and stereology. In a separate study, UNx was performed in 18 weeks old male db/db mice. These mice and control db/+ mice were injected with lectin-594 prior to termination to visualize glomerular morphology by 3D light sheet microscopy. All mice were terminated at 24 weeks of age. Male and female db/db UNx mice showed comparable increases in albuminuria. Total glomerular volume was markedly higher in male and female db/db UNx mice compared to db/+ controls (mean males; 4.42 vs. 2.71 mm3; p&amp;lt;0.001; females; 5.04 vs. 2.69 mm3; p&amp;lt;0.001). Tubulointerstitial collagen III immuno-staining was significantly increased only in female db/db UNx mice compared to db/+ mice. In contrast, total glomerular collagen IV levels were increased in male db/db UNx mice compared to db/+ controls (mean 1.30 vs. 0.80 mm3; p&amp;lt;0.01), and female db/db UNx mice displayed increased glomerular collagen IV compared to male db/db UNx mice (mean 1.80 vs. 1.30 mm3; p&amp;lt;0.05). 3D imaging at 24 weeks following UNx at 18 weeks of age confirmed expansion in glomerular volume (median db/+ 96.000 vs. db/db 145.000 µm3). Moreover, a marked increase was seen in cortical lectin-594 staining, indicating glomerular leakage in db/db UNx mice. In conclusion, male and female db/db UNx mice displayed comparable features of DN and both constitute valid models for DN. The use of whole-kidney 3D imaging provides a novel avenue for assessment of individual glomerular volume and permeability. Disclosure L.N. Fink: Employee; Self; Gubra. Stock/Shareholder; Self; Novo Nordisk A/S. F.E. Sembach: Consultant; Self; Novo Nordisk A/S. Employee; Self; Gubra. U. Roostalu: Employee; Self; Gubra. T. Johansen: Employee; Self; Gubra. J.L. Skytte: Employee; Self; Gubra. T. Secher: Employee; Self; Gubra. Employee; Spouse/Partner; Novo Nordisk A/S. Stock/Shareholder; Self; Gubra. Stock/Shareholder; Spouse/Partner; Novo Nordisk A/S. K. Fosgerau: Stock/Shareholder; Self; Gubra. N. Vrang: Board Member; Self; Gubra. Stock/Shareholder; Self; Gubra. J. Jelsing: Stock/Shareholder; Self; Gubra. J. Hecksher-Sørensen: Employee; Self; Gubra. Stock/Shareholder; Self; Novo Nordisk A/S. T.X. Pedersen: Employee; Self; Gubra.

Change in Renal Glomerular Collagens and Glomerular Filtration Barrier-Related Proteins in a Dextran Sulfate Sodium-Induced Colitis Mouse Model.

Renal disease is not rare among patients with inflammatory bowel disease (IBD) and is gaining interest as a target of research. However, related changes in glomerular structural have rarely been investigated. This study was aimed at clarifying the changes in collagens and glomerular filtration barrier (GFB)-related proteins of glomeruli in a dextran sulfate sodium (DSS)-induced colitis mouse model. Acute colitis was induced by administering 3.5% DSS in Slc:ICR strain mice for eight days. Histological changes to glomeruli were examined by periodic acid-Schiff (PAS) and Masson’s trichrome staining. Expressions of glomerular collagens and GFB-related proteins were analyzed by immunofluorescent staining and Western blot analysis. DSS-colitis mice showed an elevated disease activity index (DAI), colon shortening, massive cellular infiltration and colon damage, confirming that DSS-colitis mice can be used as an IBD animal model. DSS-colitis mice showed increased glycoprotein and collagen deposition in glomeruli. Interestingly, we observed significant changes in glomerular collagens, including a decrease in type IV collagen, and an increment in type I and type V collagens. Moreover, declined GFB-related proteins expressions were detected, including synaptopodin, podocalyxin, nephrin and VE-cadherin. These results suggest that renal disease in DSS-colitis mice might be associated with changes in glomerular collagens and GFB-related proteins. These findings are important for further elucidation of the clinical pathological mechanisms underlying IBD-associated renal disease.

Unbiased Stereological Quantification of Key Features of Diabetic Nephropathy

Diabetic nephropathy (DN) is a serious long-term complication of diabetes. There is no curative treatment of DN, and the lack of knowledge about mechanisms leading to DN hampers the development of efficient therapies. To facilitate drug development, the ability to quantify key histopathological changes in animal models of human DN is essential. In order to develop a more precise determination of translatable nephrotic changes, we used novel and refined image analyses and stereological quantification of key features of DN in a model approach combining genetic diabetes (db/db mice) with uninephrectomy (UNx). UNx or sham-operation was performed in db/db or db/+ male and female mice (n=8-16 mice per group) and the study was terminated 10 or 16 weeks after surgery. Diabetes development was similar in sham and UNx db/db mice. Compared to sham-operation, UNx increased average kidney weight in db/db females both after 10 (43%) and 16 weeks (48%). Blood urea nitrogen (BUN) was increased in UNx vs. sham-operated animals 4 weeks post-surgery, but not at termination. Notably, kidney fibrosis was increased in UNx and sham db/db vs. sham db/+ females (16 weeks; mg total collagen; 12.7 ± 1.3 and 10.7 ± 1.8, respectively, vs. 5.7 ± 0.8, p&amp;lt;0.05). Urinary albumin was progressively increased in all db/db groups with significantly lower variance in UNx db/db females than sham (F-test, p=0.02), permitting smaller group sizes in pre-clinical studies. Unbiased stereological quantification is ongoing to establish volume of glomeruli and number of podocytes. Glomerular collagen is quantified by double-fluorescence imaging concomitantly detecting podocin and collagen. In conclusion, renal hypertrophy and raised plasma BUN suggest increased pressure on the remaining kidney in UNx mice, leading to fibrosis and decreased kidney function. The thorough quantification of translatable features of DN in the db/db UNx model may provide refinement of this model enabling improved pharmacological testing of compounds targeting DN. Disclosure T.X. Pedersen: Employee; Self; Gubra. T.T. Johansen: None. L.N. Fink: Employee; Self; Gubra. Stock/Shareholder; Self; Novo Nordisk A/S. N. Vrang: Board Member; Self; Gubra. Employee; Self; Gubra. Stock/Shareholder; Self; Gubra. T. Secher: Employee; Self; Gubra. Employee; Spouse/Partner; Novo Nordisk A/S.

The effects of single and combined application of ramipril and losartan on renal structure and function in hypertensive rats

ABSTRACTThe objective of the present study was to investigate the effects of single and combined administration of ramipril and losartan on renal structure and function in spontaneously hypertensive rats (SHRs). Thirty-two 9-week-old SHRs and eight Wistar-Kyoto (WKY) rats were randomly divided into five groups: the WKY control group, the SHR control group, the SHR-ramipril group, the SHR-losartan group, and the SHR-combined mediation group. The rat body weight, SBP, heart rate, and urinary albumin excretion rate (UAER) were measured. (1) The SBP was reduced to the normal level in all groups of rats except for the SHR control group. Combined administration of ramipril and losartan can be reduced to the normal level earlier than single (P < 0.01). (2) The SHR-ramipril group and the SHR-losartan group still experienced a higher UAER than that in the WKY control group (P < 0.01). (3) The renal mass/BW ratio was decreased in the SHR-ramipril group, SHR-losartan group, and SHR-combined medication group compared to that in the SHR control group (P < 0.01). (4) Compared with the SHR control group, the SHR-ramipril group, the SHR-losartan group, and the SHR-combined medication group had a lower percentage of the IOD of glomerular collagen relative to the glomerular area (P < 0.01). (5) The reduction in tubulointerstitial injury score was more significant in the SHR-combined medication group than in the SHR-ramipril group and the SHR-losartan group (P < 0.01). The combination of ramipril and losartan is superior to either single drug in reducing the UAER, resisting glomerular collagen deposition, and protecting renal tubular structure.

Vitamin C deficiency exacerbates diabetic glomerular injury through activation of transforming growth factor-β signaling

BackgroundThe hyperglycemia and hyperoxidation that characterize diabetes lead to reduced vitamin C (VC) in diabetic humans and experimentally diabetic animals. Herein, we access the effects of VC deficiency on the diabetic kidney injury and explore the underlying mechanism. Methodsl-gulonolactone oxidase conventional knockout (Gulo−/−) mice genetically unable to synthesize VC were subjected to streptozotocin-induced diabetic kidney injury and the role of VC deficiency was evaluated by biochemical and histological approaches. Rat mesangial cells were cultured to investigate the underlying mechanism. ResultsFunctionally, VC deficiency aggravates the streptozotocin-induced renal insufficiency, exhibiting the increased urine albumin, water intake, and urine volume in Gulo−/− mice. Morphologically, VC deficiency exacerbates the streptozotocin-induced kidney injury, exhibiting the increased glomerular expansion, deposition of Periodic Acid-Schiff- and Masson-positive materials, and expression of α-smooth muscle actin, fibronectin and type 4 collagen in glomeruli of Gulo−/− mice. Mechanistically, VC activates protein kinase B (Akt) to destabilize Ski and thereby induce the expression of Smad7, resulting in suppression of TGF-β/Smad signaling and extracellular matrix deposition in mesangial cells. ConclusionsVC is essential for the renal function maintenance in diabetes. General significanceCompensation for the loss of VC could be an effective remedy for diabetic kidney injury.

The VEGF-A inhibitor sFLT-1 improves renal function by reducing endothelial activation and inflammation in a mouse model of type 1 diabetes

Aims/hypothesisAnimal models of diabetic nephropathy show increased levels of glomerular vascular endothelial growth factor (VEGF)-A, and several studies have shown that inhibiting VEGF-A in animal models of diabetes can prevent albuminuria and glomerular hypertrophy. However, in those studies, treatment was initiated before the onset of kidney damage. Therefore, the aim of this study was to investigate whether transfecting mice with the VEGF-A inhibitor sFlt-1 (encoding soluble fms-related tyrosine kinase 1) can reverse pre-existing kidney damage in a mouse model of type 1 diabetes. In addition, we investigated whether transfection with sFlt-1 can reduce endothelial activation and inflammation in these mice.MethodsSubgroups of untreated 8-week-old female C57BL/6J control (n = 5) and diabetic mice (n = 7) were euthanised 5 weeks after the start of the experiment in order to determine the degree of kidney damage prior to treatment with sFLT-1. Diabetes was induced with three i.p. injections of streptozotocin (75 mg/kg) administered at 2 day intervals. Diabetic nephropathy was then investigated in diabetic mice transfected with sFlt-1 (n = 6); non-diabetic, non-transfected control mice (n = 5); non-diabetic control mice transfected with sFlt-1(n = 10); and non-transfected diabetic mice (n = 6). These mice were euthanised at the end of week 15. Transfection with sFlt-1 was performed in week 6.ResultsWe found that transfection with sFlt-1 significantly reduced kidney damage by normalising albuminuria, glomerular hypertrophy and mesangial matrix content (i.e. glomerular collagen type IV protein levels) (p < 0.001). We also found that transfection with sFlt-1 reduced endothelial activation (p < 0.001), glomerular macrophage infiltration (p < 0.001) and glomerular TNF-α protein levels (p < 0.001). Finally, sFLT-1 decreased VEGF-A-induced endothelial activation in vitro (p < 0.001).Conclusions/interpretationThese results suggest that sFLT-1 might be beneficial in treating diabetic nephropathy by inhibiting VEGF-A, thereby reducing endothelial activation and glomerular inflammation, and ultimately reversing kidney damage.

Novel Differences in Renal Gene Expression in a Diet Induced Obesity Model of Diabetic Nephropathy

Diabetic nephropathy (DN) is a complication of diabetes mellitus. To identify novel genes differentially regulated in the early stages of DN using an unbiased approach, male C57bl/6 mice were fed high fat diet (HFD, 60% kcal fat) or matched control diet (CD, 10% kcal fat) for 9 weeks starting at 6 weeks of age to induce metabolic syndrome and DN. HFD mice had impaired glucose tolerance in a glucose tolerance test (Area Under the Curve, p=0.01, n=5 mice per group), demonstrating a pre‐diabetic like phenotype. HFD mice trended towards enlarged glomeruli (p=0.09, n= &gt;50 glomeruli from 4 mice per group) and an increase in glomerular collagen infiltration. No differences were seen in mesangial matrix deposition between HFD and CD mice. HFD mice also had an increased glomerular filtration rate/body weight (p=0.01, n= 4 mice per group). These findings are consistent with early DN. Next, RNASeq was performed on RNA from the renal cortex (n=4 CD, n=4 HFD). We identified 1134 genes differentially expressed in the renal cortex on HFD; of the 22 genes with the greatest fold changes, only 12 have been previously been studied in a diabetic context. We then utilized Taqman real‐time (RT) PCR arrays to confirm our initial findings. This secondary screen included the 9 most upregulated and 11 most downregulated genes from the RNA Seq data, with an additional 11 genes altered by RNA Seq and of interest to our group (primarily sensory receptors and G proteins). These arrays (31 genes + 18S control) were used to screen additional tissue samples (renal medulla, liver, heart, n=3 CD, n=3 HFD), and an expanded cohort of renal cortex samples (n=5 CD, n=5 HFD). All 9 of the genes significantly upregulated with HFD by RNA Seq were also upregulated by RT‐PCR (Atp12a, Ccl28, Ctxn3, Cyp2b10, Lhx2, Popdc3, Ptpn5, Sorcs1, Synpr; p&lt;0.05). However, of the remaining 22 genes (downregulated + other genes of interest) only 2 were confirmed by RT‐PCR (Gsta2, Slc7a12; p&lt;0.05). Other tissues (renal medulla, heart, and liver) were then screened for these 11 genes to determine if these changes are cortex‐specific. There were 3 genes for which changes in the renal medulla mirrored changes seen in the renal cortex. However, only 1 gene changed (p&lt;0.05) in the same direction as in the renal cortex in both the liver (Gsta2) and the heart (Cyp2b10). These data demonstrate that our RNA Seq data regarding upregulation were more reproducible than those regarding downregulation, and that changes are largely kidney specific. Furthermore, these data imply that renal changes are downstream of metabolic changes, and not non‐specific global changes due to an alteration in diet. Changes were then examined in samples from CD and HFD female mice, which were either diet matched (DM; fed the diet described above) or weight matched (WM; fed diet for 12 weeks from weaning). Only 1 gene (Cyp2b10, p&lt;0.05) was altered as expected in the DM females, while a different gene (Synpr, p&lt;0.05) was altered in the WM females, indicating that the changes seen in our initial cohort are likely male‐specific, in agreement with the fact that female mice fail to develop metabolic syndrome on this diet. Thus, we have identified genes in the renal cortex which are differentially regulated in DN, the majority of which are sex‐specific, and many of which have never before been studied in a diabetic context.

Renal dysfunction in early adulthood following birth asphyxia in male spiny mice, and its amelioration by maternal creatine supplementation during pregnancy.

Acute kidney injury affects ~70% of asphyxiated newborns, and increases their risk of developing chronic kidney disease later in life. Acute kidney injury is driven by renal oxygen deprivation during asphyxia, thus we hypothesized that creatine administered antenatally would protect the kidney from the long-term effects of birth asphyxia. Pregnant spiny mice were fed standard chow or chow supplemented with 5% creatine from 20-d gestation (midgestation). One day prior to term (37-d gestation), pups were delivered by caesarean or subjected to intrauterine asphyxia. Litters were allocated to one of two time-points. Kidneys were collected at 1 mo of age to estimate nephron number (stereology). Renal function (excretory profile and glomerular filtration rate) was measured at 3 mo of age, and kidneys then collected for assessment of glomerulosclerosis. Compared with controls, at 1 mo of age male (but not female) birth-asphyxia offspring had 20% fewer nephrons (P < 0.05). At 3 mo of age male birth-asphyxia offspring had 31% lower glomerular filtration rate (P < 0.05) and greater glomerular collagen IV content (P < 0.01). Antenatal creatine prevented these renal injuries arising from birth asphyxia. Maternal creatine supplementation during pregnancy may be an effective prophylactic to prevent birth asphyxia induced acute kidney injury and the emergence of chronic kidney disease.

Discoidin domain receptor 1 kinase activity is required for regulating collagen IV synthesis

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that binds to and is activated by collagens. DDR1 expression increases following kidney injury and accumulating evidence suggests that it contributes to the progression of injury. To this end, deletion of DDR1 is beneficial in ameliorating kidney injury induced by angiotensin infusion, unilateral ureteral obstruction, or nephrotoxic nephritis. Most of the beneficial effects observed in the DDR1-null mice are attributed to reduced inflammatory cell infiltration to the site of injury, suggesting that DDR1 plays a pro-inflammatory effect. The goal of this study was to determine whether, in addition to its pro-inflammatory effect, DDR1 plays a deleterious effect in kidney injury by directly regulating extracellular matrix production. We show that DDR1-null mice have reduced deposition of glomerular collagens I and IV as well as decreased proteinuria following the partial renal ablation model of kidney injury. Using mesangial cells isolated from DDR1-null mice, we show that these cells produce significantly less collagen compared to DDR1-null cells reconstituted with wild type DDR1. Moreover, mutagenesis analysis revealed that mutations in the collagen binding site or in the kinase domain significantly reduce DDR1-mediated collagen production. Finally, we provide evidence that blocking DDR1 kinase activity with an ATP-competitive small molecule inhibitor reduces collagen production. In conclusion, our studies indicate that the kinase activity of DDR1 plays a key role in DDR1-induced collagen synthesis and suggest that blocking collagen-mediated DDR1 activation may be beneficial in fibrotic diseases.

Once daily administration of the SGLT2 inhibitor, empagliflozin, attenuates markers of renal fibrosis without improving albuminuria in diabetic db/db mice.

Blood glucose control is the primary strategy to prevent complications in diabetes. At the onset of kidney disease, therapies that inhibit components of the renin angiotensin system (RAS) are also indicated, but these approaches are not wholly effective. Here, we show that once daily administration of the novel glucose lowering agent, empagliflozin, an SGLT2 inhibitor which targets the kidney to block glucose reabsorption, has the potential to improve kidney disease in type 2 diabetes. In male db/db mice, a 10-week treatment with empagliflozin attenuated the diabetes-induced upregulation of profibrotic gene markers, fibronectin and transforming-growth-factor-beta. Other molecular (collagen IV and connective tissue growth factor) and histological (tubulointerstitial total collagen and glomerular collagen IV accumulation) benefits were seen upon dual therapy with metformin. Albuminuria, urinary markers of tubule damage (kidney injury molecule-1, KIM-1 and neutrophil gelatinase-associated lipocalin, NGAL), kidney growth, and glomerulosclerosis, however, were not improved with empagliflozin or metformin, and plasma and intra-renal renin activity was enhanced with empagliflozin. In this model, blood glucose lowering with empagliflozin attenuated some molecular and histological markers of fibrosis but, as per treatment with metformin, did not provide complete renoprotection. Further research to refine the treatment regimen in type 2 diabetes and nephropathy is warranted.

Incomplete Restoration of Angiotensin II-Induced Renal Extracellular Matrix Deposition and Inflammation Despite Complete Functional Recovery in Rats.

Some diseases associated with a temporary deterioration in kidney function and/or development of proteinuria show an apparently complete functional remission once the initiating trigger is removed. While it was earlier thought that a transient impairment of kidney function is harmless, accumulating evidence now suggests that these patients are more prone to developing renal failure later in life. We therefore sought to investigate to what extent renal functional changes, inflammation and collagen deposition are reversible after cessation of disease induction, potentially explaining residual sensitivity to damage. Using a rat model of Angiotensin II (Ang II)-induced hypertensive renal disease we show the development of severe hypertension (212 ± 10.43 vs. 146 ± 1.4 mmHg, p<0.001) and proteinuria (51.4 ± 6.3 vs. 14.7 ± 2.0 mg/24h, p<0.01) with declined creatinine clearance (2.0 ± 0.5 vs. 4.9 ± 0.6 mL/min, p<0.001) to occur after 3 weeks of Ang II infusion. At the structural level, Ang II infusion resulted in interstitial inflammation (18.8 ± 4.8 vs. 3.6 ± 0.5 number of macrophages, p<0.001), renal interstitial collagen deposition and lymphangiogenesis (4.1 ± 0.4 vs. 2.2 ± 0.4 number of lymph vessels, p<0.01). Eight weeks after cessation of Ang II, all clinical parameters, pre-fibrotic changes such as myofibroblast transformation and increase in lymph vessel number (lymphangiogenesis) returned to control values. However, glomerular desmin expression, glomerular and periglomerular macrophages and interstitial collagens remained elevated. These dormant abnormalities indicate that after transient renal function decline, inflammation and collagen deposition may persist despite normalization of the initiating pathophysiological stimulus perhaps rendering the kidney more vulnerable to further damage.

Glomerular Collagen V Codeposition and Hepatic Perisinusoidal Collagen III Accumulation in Canine Collagen Type III Glomerulopathy.

Collagen type III glomerulopathy, also known as collagenofibrotic glomerulopathy, is a rare renal disease of unknown pathogenesis. The disease occurs in humans and animals and is characterized by massive glomerular accumulations of collagen type III. In the present study, we describe a Drever dog litter affected by an early onset variant of this glomerular disease, where 4 of 9 puppies developed renal failure within 50 days of age. Necropsy specimens of kidney from the 4 affected cases were studied by light microscopy, electron microscopy, and immunohistochemistry, and characteristic lesions compatible with a diagnosis of collagen type III glomerulopathy were found. In addition, 2 cases showed atypical epithelium in the collecting ducts of the medulla, so-called adenomatoid change. Immunohistochemistry of renal specimens from collagen type III glomerulopathy-affected dogs (n = 10) originating from two different dog strains, the Drever dogs and a mixed-breed strain, demonstrated that the deposited glomerular collagen is composed of a mixture of collagen III and collagen V. The distribution of the collagen V corresponded to the localization of collagen III; however, differences in staining intensity showed that collagen type III is the dominating component. Immunohistochemistry for collagen III (n = 9) and a transmission electron microscopic study (n = 1) showed hepatic perisinusoidal collagen type III deposition in affected cases from both dog strains. This is the first report documenting glomerular accumulations of collagen type V and perisinusoidal liver collagen III deposition in canine collagen type III glomerulopathy.