Model Of Chronic Kidney Disease Research Articles

Chronic kidney disease alters tryptophan metabolite concentrations in male and female Sprague Dawley rats

Kynurenine is the first stable metabolite of tryptophan degradation. An increased ratio of kynurenine (KYN) to tryptophan (TRP) has been implicated in many disease states including chronic kidney disease (CKD) in humans. We hypothesized that we would see a similar increase in KYN/TRP in a CKD model in male and female rats. We induced CKD with a 0.25% adenine diet for 15 weeks and then measured a variety of renal parameters. Serum and kidneys were collected at sacrifice. We found that GFR was better preserved in CKD female rats compared to males (0.232 ± 0.056 vs. 0.081 ± 0.019 ml/min/100g BW) but was decreased significantly compared to controls (0.739 ± 0.048 female, 0.635 ± 0.099 male). Urine volume was elevated significantly in CKD rats compared to controls (80.0 ± 6.9 ml/day male CKD, 72.5 ± 4.7 female CKD vs. 13.3 ± 1.1 male CTL and 22.0 ± 1.8 female CTL). However, male CKD rats consumed significantly more water than female CKD (104.1 ± 7.3 ml/day male vs. 81.0 ± 5.1 female), although water consumption was similar in controls in both sexes (30.9 ± 2.6 male and 30.1 ± 2.5 female). Weekly food consumption and body weight were similar between same sex groups. Both male and female rats showed increased KYN/TRP in CKD compared to controls (0.102 ± 0.010 in male and 0.105 ± 0.011 in female CKD vs. 0.049 ± 0.005 and 0.033 ± 0.002 CTL). Similarly, kynurenic acid was elevated significantly in both sexes in CKD (305.7 ± 76.7 nmol/L male and 669.2 ± 140.7 female) compared to controls (92.3 ± 17.7 and 118.1 ± 14.7) respectively. These data show that the adenine feeding model of CKD reproduces many of the characteristics of human disease including alterations in TRP metabolites. This model will allow study of TRP metabolites in CKD progression. This work was supported by Career Development Award IK2 BX004997 from the United States Department of Veteran Affairs, Biomedical Laboratory Research and Development Service. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cognate Antigen-Independent Differentiation and Activation of Resident Memory T cells in Chronic Kidney Disease

Resident memory T cells (TRMs) are a memory subset of T cells which are retained locally within barrier and epithelial tissues such as the kidney and have also been noted for their role in perpetuating chronic inflammation. While T cells have gained recognition for their ability to modulate kidney inflammation in various models of kidney injury TRMs are still poorly understood and their contributions to sterile models of chronic kidney disease (CKD) are unknown. We hypothesized that kidney TRMs are activated and modulate kidney inflammation in the setting of CKD. We utilized an aristolochic acid (AA) model of murine CKD to investigate the presence of kidney TRMs via flow cytometry and characterized their transcriptional profile via single cell RNA sequencing (scRNAseq). We also measured kidney cytokine levels with an MSD cytokine plate. Six weeks after AA-induced CKD, kidney CD8+ T cells were significantly increased compared to control mice (29.6 ± 1.6% vs. 4.7 ± 0.6% of CD45+, respectively; p<0.0001), as were CD4+ T cells (34.4 ± 1.4% vs. 8.2 ± 0.7% of CD45+, respectively; p<0.0001). 53.6 ± 2.5% of CD8+ T cells expressed CD103, a TRM marker, in AA mice compared to 4.8 ± 1.2% in control mice, and 36.0 ± 1.7% vs 1.6 ± 0.3% of CD4+ T cells. Kidney protein lysates of AA mice had significantly higher levels of IFNγ than control kidneys (18.9 ± 1.6 vs. 2.9 ± 0.7 pg/mg, respectively; p=0.0003) as well as TNF (98.6 ± 8.9 pg/mg vs. 6.9 ± 0.8 pg/mg, respectively; p=0.0002) and IL-6 (247.6 ± 39.1 pg/mg vs. 75.4 ± 22.5 pg/mg, respectively; p=0.0226). scRNAseq of immune cells revealed T cells bearing TRM markers CD103 and CD49a which lacked expression of tissue egress molecules S1pr1, Sell, Ccr7, and Klf2. scRNAseq analysis of this TRM population also revealed downregulation of Eomes and Tbx21 transcription factors and upregulation of Runx3 transcription factor, all of which correspond with previously described TRM transcriptional profiles. We next evaluated signaling pathways involved with the survival and transcriptional profile of TRMs, namely IL-15 and TGF-β. While Il2rb and Il2rg (encoding IL-15 receptor subunits) were upregulated in TRMs, IL-15 protein lysate levels were not elevated in AA kidneys compared to controls (2,600 ± 145 pg/mg protein vs. 2,281 ± 96 pg/mg protein, respectively; p=0.0831). Tgfbr1 and Tgfbr2 (encoding TGF-β receptor subunits) were also upregulated in TRMs, but TGF-β protein lysate levels were not significantly elevated in AA kidneys compared to controls (2,158 ± 159 pg/mg protein vs. 1,924 ± 202 pg/mg protein, respectively; p=0.3886). Gene ontology pathway analysis showed enrichment of pathways involved in T cell receptor signaling. Because of this we assessed the kidney immune profile of transgenic OT-1 mice, which can only recognize specific ovalbumin residues in the context of MHC class 1 H-2Kb. Six weeks after AA-induced CKD, injured OT-1 mice still had a significant increase in the proportion of CD8+ T cells that were CD103+ compared to vehicle control OT-1 mice (47.3 ± 2.9% vs. 9.6 ± 1.6% of CD45+, respectively; p<0.0001) and CD4+ T cells that were CD103+ (26.7 ± 3.1% vs. 6.4 ± 2.4% of CD45+, respectively; p=0.0040). Here we demonstrate the differentiation and activation of TRMs during AA-induced CKD independent of cognate antigen interaction and highlight their activated profile, as well as an increase in kidney IFNγ, TNF, and IL-6, all proinflammatory cytokines typical of TRMs. Future studies will aim to determine the contributions of TRMs to CKD progression. F32 DK136187, T32 DK007545, R01 DK 118932, U54 DK137301. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Kidney disease associated with pre-pubertal obesity initiates pathological alterations in the brain of Dahl salt-sensitive rats

Childhood/pre-pubertal obesity (PPO) is implicated in the development of chronic kidney disease (CKD), and there is evidence that PPO also increases the risk of developing Alzheimer disease (AD) later in life. In the current study, we aim to investigate the correlation between CKD and the development of AD-like pathology in a rat model of CKD associated with PPO. We hypothesize that systemic inflammation due to PPO exacerbates CKD and induces AD-like pathology in the brain at older age. In our preliminary studies, we utilized the Dahl salt sensitive leptin receptor mutant rat (SSLepRmutant), which is a novel model of PPO. 6-week-old Dahl salt-sensitive (SS) (control, n=3) and SSLepRmutant rats (n=5) were monitored for proteinuria every 3 weeks, for a 12-week period. Throughout the study, we observed significantly elevated proteinuria in SSLepRmutant rats (Week-6: 337±81 mg/day, Week-9: 371±147 mg/day, Week-18: 1920±318 mg/day) compared to SS rats (Week-6: 25±7 mg/day, Week-9: 35±39 mg/day, Week-18: 35±33 mg/day). At 18-week, creatinine levels were significantly higher in SSLepRmutant rats (1.5±0.5 mg/dL) versus SS rats (0.4±0.03 mg/dL) indicating CKD. Additionally, we found significant elevation of triglycerides in SSLepRmutant rats (5134±1211 mg/dL) compared to SS rats (79±21 mg/dL). To investigate the brain pathology, we performed immunochemical analysis (dot-blot assay) using A11 antibody to determine the levels of Amyloid-beta oligomers (Aβo). Our results show that there was tendency for Aβo levels to be increased in the brains from obese SSLepRmutant rats compared to SS. Finally, we tested the permeability of the blood-brain barrier to Evans blue dye and observed that the brain of SSLepRmutant rats was more permeable to the dye compared to SS rats as early as 8 weeks of age. Overall, these results indicate that PPO obesity not only increases the susceptibility to develop CKD but also causes Alzheimer-like pathology during the prepubescent stage. NIDDK (DK109133) and AG (AG057842) awarded to Jan M. Williams. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Novel Mouse Model of Physical Inactivity to Study the Role of Mitochondria in Chronic Kidney Disease

Chronic kidney disease (CKD) is a progressive disorder marked by a decline in kidney function. It is thought that a decline in mitochondrial function likely contributes to the pathogenesis of CKD, but the detailed mechanisms remain unclear. This gap in knowledge is contributed by a lack of a murine CKD model that does not rely on injury, toxin, or gene deletion to induce reduced kidney function. In humans, obesity and sedentary behavior strongly contribute to the development of CKD. The aim of the study was to employ small mouse cage (SMC) housing, a novel mouse physical inactivity model that was recently developed in our lab, and test whether it can be used to reliably induce CKD in mice. Wildtype C57BL6J mice were given standard chow or Western high-fat diet (HFD) with or without SMC intervention for 24 weeks to examine the effects of HFD and SMC on glomerular filtration rate (GFR) and respiration on isolated mitochondria from kidney cortex. Although the GFR values of the HFD+SMC group trended higher than other groups, the kidney function was still considered to be normal. Neither HFD nor HFD+SMC group had developed CKD, but mitochondrial respiration of SMC+HFD (1512.64 ± 77.86 pmol·sec−1·mgprotein−1) was significantly greater than that of the HFD-only group (1307.82 ± 79.08 pmol·sec−1·mgprotein−1, p = 0.0017) or the standard chow group (1104.69 ±143.12 pmol·sec−1·mgprotein−1, p = 0.0314. One-way ANOVA followed by Tukey’s test for multiple comparisons). Increased mitochondrial respiration may suggest a hyperfiltration-induced stress response, as commonly observed in the early stages of CKD in humans, and/or an increase in respiration to compensate for reduced effciency of oxidative phosphorylation. We interpret these data to mean that HFD and HFD+SMC are beginning to show adaptations that are in an early phase of CKD development. However, this model requires further optimization to yield the CKD phenotype. Therefore, we intend to further adapt the intervention to induce symptomatic CKD. We envision that developing preclinical models of CKD will help better elucidate its molecular mechanism and identify therapeutic targets for treating CKD in human patients. DK107397, DK127979. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Glomerular Hyperfiltration and Th17 Responses Promote Glomerulosclerosis Following Nephron Loss

Objective: Chronic kidney disease (CKD) affects 37 million Americans resulting in $87 billion healthcare cost annually. Impaired renal autoregulation in obesity, diabetes and hypertension causes elevated glomerular capillary pressure and whole-kidney hyperfiltration, leading to progressive glomerulosclerosis and CKD. In advanced CKD with less than 50% functional nephron mass, single-nephron hyperfiltration causes further nephron loss, ultimately leading to hypofiltration and end-state kidney disease. Increased renal perfusion pressure directly drives T cell infiltration to the kidney. We and others have shown that T helper (Th) 17 cells promote vascular stiffening in hypertension and renal interstitial fibrosis after ischemia-reperfusion injury, but their roles in glomerulosclerosis and CKD are poorly understood. We hypothesized that glomerular hypertension and hyperfiltration promote renal fibrosis through Th17-mediated immune responses. Methods: We investigated the causal roles of glomerular hyperfiltration and Th17 responses in a mouse CKD model induced by reduced kidney mass (RKM), which involved right kidney nephrectomy and partial renal artery ligation in the left kidney such that the functional renal mass is reduced by ~ 5/6. Male 129/S6 mice received sham or RKM surgery at 8 weeks of age, and blood pressure (BP, by radiotelemetry), glomerular filtration rate (GFR, by transcutaneous FITC-sinistrin) and serum/urine CKD markers were assessed at baseline (BL) and week 1, 2, 3, 4, 8, and 12 post-surgery. Results: BP and GFR of RKM mice were identical to sham controls at BL (n=4-6). Immediately after the RKM procedure, GFR dropped to 22% of BL, consistent with the extent of renal mass ablation. BP increased by 29 mmHg first week after 5/6 ablation (144 ± 8 vs BL 112 ± 2 mmHg, p<0.05, 2-way ANOVA), exposing the remnant nephrons to increased renal perfusion pressure. Serum creatinine, blood urea nitrogen and urinary albumin were significantly elevated by week 2. BP and CKD markers remained elevated through week 12 in the 5/6 ablation mice. The GFR of ablated mice gradually increased to 38% of BL at day 3, 57% at week 1 and 68% at week 2, suggesting that systemic hypertension and impaired renal autoregulation may have caused substantial single-nephron hyperfiltration in the remnant kidney mass. GFR plateaued at ~ 70% of BL in week 3-4 then declined to 48% at week 8-12 when glomerular, interstitial, and microvascular fibrosis developed as evidence by Periodic Acid Schiff and Picro Sirius Red staining. Supporting a causal role of hemodynamic derangements in CKD progression, calcium channel blocker amlodipine, a potent vasodilator, dose dependently (5-10 mg/kg/day, n=7-9) exacerbated glomerular hyperfiltration, glomerulosclerosis and mortality despite marked BP-lowering effects. Importantly, the adaptive increase of GFR in the first 2 weeks post 5/6 ablation was accompanied by significant increase of renal Th17 cells, which not only preceded the infiltration of CD11b+ myeloid cells, F4/80+ monocyte/macrophages and T regulatory cells, but also the glomerulosclerosis and GFR decline in week 8. Conclusions: Our data suggest that glomerular hyperfiltration causes progressive nephron loss and kidney fibrosis, at least in part, through Th17-mediated renal inflammation. To further establish causality, ongoing studies will assess if Th17 blockade ameliorates glomerulosclerosis and retard CKD progression. Funding: This work was supported by NIDDK R01 DK094907, R01 DK113632, R01 DK128677 to THL, and K01 DK126972 to JW. JW is also supported by an American Heart Association Second Century Early Faculty Independence Award (23SCEFIA1148464), a University of Rochester Environmental Health Science Center pilot award (Prime sponsor: NIEHS P30ES001247), and a University of Rochester Program for Advanced Immune Bioimaging Pilot Award (Prime Sponsor: NIAID P01AI102851). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Impact of lymphangiogenesis on renal phosphate handling following kidney injury

Overconsumption of inorganic phosphate (Pi) causes tubular cell damage and kidney dysfunction, and hyperphosphatemia can lead to Ca2+ retention, vascular calcification, and cardiovascular disease. Conversely, kidney injury and chronic kidney disease (CKD) cause hyperphosphatemia and Pi retention. We hypothesized that the damage caused by chronic Pi consumption likely induces kidney lymphangiogenesis and that changes to renal lymphatic density may alter kidney mineral handling. We identified significant lymphangiogenesis and increased expression of the lymphatic growth factors VEGF-C/D in kidneys of mice fed a 2% Pi diet for 2 months and as early as three weeks of diet. We then utilized “KidVD” mice, a mouse model of kidney-specific inducible expression of VEGF-D, to expand renal lymphatic density and test Pi handling. Mineral handling was largely normal in male and female KidVD mice compared to littermates on Pi diet. In a Pi-driven CKD model mice were injured with 10 mg/kg cisplatin dose, allowed to recover for 2 weeks, then challenged with chow or 2% Pi diet for 3 weeks with VEGF-D induction. This resulted in Pi retention in all mice. Pi handling in both male and female KidVD mice were normal to controls. Female KidVD, however, demonstrated significantly increased Ca2+ excretion compared to controls. Circulating FGF23 levels were significantly elevated in male and female with VEGF-D overexpression. Gene expression of Fgfr1 was also significantly increased in male and female KidVD mice. Renal lymphangiogenesis thus appears to specifically impact Ca2+ retention through the FGF23-Fgfr1 axis. National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (R01 DK119497). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The c-Abl-RACK1-FAK signaling axis promotes renal fibrosis in mice through regulating fibroblast-myofibroblast transition

BackgroundRenal fibrosis is a prevalent manifestation of chronic kidney disease (CKD), and effective treatments for this disease are currently lacking. Myofibroblasts, which originate from interstitial fibroblasts, aggregate in the renal interstitium, leading to significant accumulation of extracellular matrix and impairment of renal function. The nonreceptor tyrosine kinase c-Abl (encoded by the Abl1 gene) has been implicated in the development of renal fibrosis. However, the precise role of c-Abl in this process and its involvement in fibroblast-myofibroblast transition (FMT) remain poorly understood.MethodsTo investigate the effect of c-Abl in FMT during renal fibrosis, we investigated the expression of c-Abl in fibrotic renal tissues of patients with CKD and mouse models. We studied the phenotypic changes in fibroblast or myofibroblast-specific c-Abl conditional knockout mice. We explored the potential targets of c-Abl in NRK-49F fibroblasts.ResultsIn this study, fibrotic mouse and cell models demonstrated that c-Abl deficiency in fibroblasts mitigated fibrosis by suppressing fibroblast activation, fibroblast-myofibroblast transition, and extracellular matrix deposition. Mechanistically, c-Abl maintains the stability of the RACK1 protein, which serves as a scaffold for proteins such as c-Abl and focal adhesion kinase at focal adhesions, driving fibroblast activation and differentiation during renal fibrosis. Moreover, specifically targeting c-Abl deletion in renal myofibroblasts could prove beneficial in established kidney fibrosis by reducing RACK1 expression and diminishing the extent of fibrosis.ConclusionsOur findings suggest that c-Abl plays a pathogenic role in interstitial fibrosis through the regulation of RACK1 protein stabilization and myofibroblast differentiation, suggesting a promising strategy for the treatment of CKD.

A nomogram to predict cognitive function impairment in patients with chronic kidney disease: A national cross-sectional survey

BackgroundCognitive function impairment (CFI) is common in patients with chronic kidney disease (CKD) and significantly impacts treatment adherence and quality of life. This study aims to create a simplified nomogram for early CFI risk detection. MethodsData were obtained from the National Health and Nutrition Examination Survey cycles spanning from 1999 to 2002 and again from 2011 to 2014. Stepwise logistic regression was used to select variables and construct a CFI risk prediction model. Furthermore, C-statistic and Brier Score (BS) assessed model performance. Additionally, Kaplan–Meier survival curves were utilised to assess risk group-death prognosis relationships. ResultsOf the 545 participants in the CKD model development cohort, a total of 146 (26.8 %) had CFI. The final model included the variables of age, race, education, annual family income, body mass index, estimated glomerular filtration rate, serum albumin and uric acid. The model had a C-statistic of 0.808 (95 % confidence interval (CI): 0.769–0.847) and a BS of 0.149. Furthermore, the 5-fold cross-validation internal C-statistic was 0.764 (interquartile range: 0.763–0.807) and BS was 0.154. Upon external validation, the model's C-statistic decreased to 0.752 (95 % CI: 0.654–0.850) and its BS increased to 0.182. The Kaplan–Meier survival curves demonstrated that intermediate-to-high-risk participants had shorter overall survival time than low-risk participants (log-rank test: p = 0.00042). ConclusionsThis study established an effective nomogram for predicting CFI in patients with CKD, which can be used for the early detection of CFI and guide the treatment of patients with CKD.

The secreted micropeptide C4orf48 enhances renal fibrosis via an RNA-binding mechanism.

Renal interstitial fibrosis is an important mechanism in the progression of chronic kidney disease (CKD) to end-stage kidney disease. However, we lack specific treatments to slow or halt renal fibrosis. Ribosome profiling identified upregulation of a secreted micropeptide, C4orf48 (Cf48), in mouse diabetic nephropathy. Cf48 RNA and protein levels were upregulated in tubular epithelial cells in human and experimental CKD. Serum Cf48 levels were increased in human CKD and correlated with loss of kidney function, increasing CKD stage, and the degree of active interstitial fibrosis. Cf48 overexpression in mice accelerated renal fibrosis, while Cf48 gene deletion or knockdown by antisense oligonucleotides significantly reduced renal fibrosis in CKD models. In vitro, recombinant Cf48 (rCf48) enhanced TGF-β1-induced fibrotic responses in renal fibroblasts and epithelial cells independently of Smad3 phosphorylation. Cellular uptake of Cf48 and its profibrotic response in fibroblasts operated via the transferrin receptor. RNA immunoprecipitation-sequencing identified Cf48 binding to mRNA of genes involved in the fibrotic response, including Serpine1, Acta2, Ccn2, and Col4a1. rCf48 binds to the 3'UTR of Serpine1 and increases mRNA half-life. We identify the secreted Cf48 micropeptide as a potential enhancer of renal fibrosis that operates as an RNA-binding peptide to promote the production of extracellular matrix.

Cognitive Impairment Related to Chronic Kidney Disease Is Associated with a Decreased Abundance of Membrane-Bound Klotho in the Cerebral Cortex.

Cognitive impairment (CI) is a complication of chronic kidney disease (CKD) that is frequently observed among patients. The aim of this study was to evaluate the potential crosstalk between changes in cognitive function and the levels of Klotho in the brain cortex in an experimental model of CKD. To induce renal damage, Wistar rats received a diet containing 0.25% adenine for six weeks, while the control group was fed a standard diet. The animals underwent different tests for the assessment of cognitive function. At sacrifice, changes in the parameters of mineral metabolism and the expression of Klotho in the kidney and frontal cortex were evaluated. The animals with CKD exhibited impaired behavior in the cognitive tests in comparison with the rats with normal renal function. At sacrifice, CKD-associated mineral disorder was confirmed by the presence of the expected disturbances in the plasma phosphorus, PTH, and both intact and c-terminal FGF23, along with a reduced abundance of renal Klotho. Interestingly, a marked and significant decrease in Klotho was observed in the cerebral cortex of the animals with renal dysfunction. In sum, the loss in cerebral Klotho observed in experimental CKD may contribute to the cognitive dysfunction frequently observed among patients. Although further studies are required, Klotho might have a relevant role in the development of CKD-associated CI and represent a potential target in the management of this complication.

Renal Artery Coil Embolization as an Endovascular Approach for Establishing a Rabbit Model of Chronic Kidney Disease

PurposeTo investigate the safety and feasibility of renal artery coil embolization for establishing chronic kidney disease (CKD) in rabbits. Materials and MethodsTen male adult New Zealand rabbits underwent renal artery coil embolization. Initially, the main renal artery on 1 side was completely embolized, followed by embolization of approximately two-thirds of the primary branches of the contralateral renal artery 1 week later. Four rabbits were randomly chosen for sacrifice at 4 weeks after embolization, whereas the remaining 6 were sacrificed at 8 weeks after embolization. The assessment encompassed the animals’ general condition, angiography, biochemical parameters, inflammatory markers, and histopathological examination of the kidneys and hearts. ResultsFour weeks after embolization, serum creatinine level showed a substantial increase (2.4 mg/dL [SD ± 0.6]; P = .009 vs baseline), with a subsequent 4.12-fold elevation at 8 weeks after embolization (4.9 mg/dL [SD ± 1.4]; P < .001 vs baseline). Additionally, considerable increases in serum blood urea nitrogen, calcium, and potassium ions were observed at 8 weeks after embolization (58.3 mg/dL [SD ± 19.0]; P < .001 vs baseline; 23.1 mg/dL [SD ± 4.4]; P < .001 vs baseline; and 6.3 mEq/L [SD ± 0.7]; P < .001 vs baseline, respectively). The completely embolized kidney exhibited notable atrophy, severe fibrosis, and cortical calcification, whereas the contralateral partially embolized kidney displayed compensatory hypertrophy, along with glomerulosclerosis, tubular dilation, tubular casts, and interstitial fibrosis. ConclusionsRenal artery coil embolization proved to be effective and safe for establishing a CKD model in rabbits.

Linking renal hypoxia and oxidative stress in chronic kidney disease: Based on clinical subjects and animal models.

This study aims to explore the relationships between renal function, hypoxia, and oxidative stress in chronic kidney disease (CKD). Seventy-six non-dialysis patients with CKD stages 1-5 and eight healthy subjects were included in the clinical research. They were divided into three groups: healthy subjects, CKD stages 1-3, and CKD stages 4-5. In the animal study, 16 rat models of CKD were established through 5/6 renal ablation/infarction (A/I) surgery, and 8 normal rats were split into 3 groups: Sham, CKD, and losartan groups. Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) was used to measure cortical and medullary T2* values (COT2* and MET2*) in all subjects and rats to evaluate renal oxygenation. Biochemical indicators were used to assess renal function and antioxidant capacity. Furthermore, the effects of losartan on renal fibrosis, hypoxia, and oxidative stress were examined using immunoblotting, colorimetric, and fluorometric assays. The results demonstrated significant positive associations between COT2* and MET2* with estimated glomerular filtration rate (eGFR). Patients with CKD stages 4-5 showed significantly lower serum superoxide dismutase (SOD) levels, which also had positive correlations with eGFR, COT2*, and MET2*. Furthermore, losartan treatment resulted in improved renal function and fibrosis, leading to increased levels of COT2*, MET2*, and SOD levels in 5/6 A/I rats. This was accompanied by reduced levels of hypoxia-inducible factor-1 alpha (HIF-1α) and malondialdehyde. Furthermore, losartan restored the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), and suppressed the expression of Kelch-like ECH-associated protein 1 (Keap1) in 5/6 A/I kidneys. The study indicates that decline in renal oxygenation and antioxidant capacity is associated with the severity of renal failure in CKD. Losartan can potentially alleviate renal hypoxia and oxidative stress in the treatment of CKD via Keap1-Nrf2/HO-1 pathway.

Common mouse models of chronic kidney disease are not associated with cachexia

The 5/6 nephrectomy and adenine-induced nephropathy mouse models have been extensively used to study Chronic Kidney Disease (CKD)-related cachexia. One common caveat of these CKD models is the cross-sectional nature of comparisons made versus controls. We here performed a comprehensive longitudinal assessment of body composition and energy metabolism in both models. The most striking finding is that weight loss is largely driven by reduced food intake which promotes rapid loss of lean and fat mass. However, in both models, mice catch up weight and lean mass a few days after the surgery or when they are switched back to standard chow diet. Muscle force and mass are fully recovered and no sign of cachexia is observed. Our data demonstrate that the time-course of kidney failure and weight loss are unrelated in these common CKD models. These data highlight the need to reconsider the relative contribution of direct and indirect mechanisms to muscle wasting observed in CKD.

Recovery of Water Homeostasis in Adenine-Induced Kidney Disease Is Mediated by Increased AQP2 Membrane Targeting.

Chronic kidney disease (CKD) represents a major public health burden with increasing prevalence. Current therapies focus on delaying CKD progression, underscoring the need for innovative treatments. This necessitates animal models that accurately reflect human kidney pathologies, particularly for studying potential reversibility and regenerative mechanisms, which are often hindered by the progressive and irreversible nature of most CKD models. In this study, CKD was induced in mice using a 0.2% adenine-enriched diet for 4 weeks, followed by a recovery period of 1 or 2 weeks. The aim was to characterize the impact of adenine feeding on kidney function and injury as well as water and salt homeostasis throughout disease progression and recovery. The adenine diet induced CKD is characterized by impaired renal function, tubular injury, inflammation, and fibrosis. A significant decrease in urine osmolality, coupled with diminished aquaporin-2 (AQP2) expression and membrane targeting, was observed after adenine treatment. Intriguingly, these parameters exhibited a substantial increase after a two-week recovery period. Despite these functional improvements, only partial reversal of inflammation, tubular damage, and fibrosis were observed after the recovery period, indicating that the inclusion of the molecular and structural parameters is needed for a more complete monitoring of kidney status.

Mechanical insights into jawbone characteristics under chronic kidney disease: A comprehensive nanoindentation approach

The mechanical properties of the jawbone play a critical role in determining the successful integration of dental prostheses. Chronic kidney disease (CKD) has been identified to abnormally accelerate bone turnover rates. However, the impact of CKD on the mechanical characteristics of the jawbone has not been extensively studied. This study sought to evaluate the time-dependent viscoelastic behaviors of rat jawbones, particularly in the scenarios both with and without CKD. We hypothesized that CKD might compromise the bone's innate toughening mechanisms, potentially owing to the time-dependent viscoelasticity of the bone matrix proteins. The maxillary and mandibular bones of Wistar rats were subjected to nanoindentation and Raman micro-spectroscopy. Load-hold-displacement curves from the cortical regions were obtained via nanoindentation and were mathematically characterized using a suitable viscoelastic constitutive model. Raman micro-spectroscopy was employed to identify nuanced vibrational changes in local molecular structures induced by CKD. The time course of indenter penetration onto cortical bones during the holding stage (creep behavior) can be mathematically represented by a series arrangement of the Kelvin–Voigt bodies. This configuration dictates the overall viscoelastic response observed during nanoindentation tests. The CKD model exhibited a reduced extent of viscoelastic contributions, especially during the initial ramp loading phase in both the maxillary and mandibular cortical bones. The generalized Kelvin–Voigt model comprises 2 K–Voigt elements that signify an immediate short retardation time (τ1) and a subsequent prolonged retardation time (τ2), respectively. Notably, the mandibular CKD model led to an increase in the delayed τ2 alongside an increase in non-enzymatic collagen cross-linking. These suggest that, over time, CKD diminishes the bone's capability for supplementary energy absorption and dimensional recovery, thus heightening their susceptibility to fractures.

Blockade of aryl hydrocarbon receptor restricts omeprazole-induced chronic kidney disease.

Chronic kidney disease (CKD) is the 16th leading cause of mortality worldwide. Clinical studies have raised that long-term use of omeprazole (OME) is associated with the morbidity of CKD. OME is commonly used in clinical practice to treat peptic ulcers and gastroesophageal reflux disease. However, the mechanism underlying renal failure following OME treatment remains mostly unknown and the rodent model of OME-induced CKD is yet to be established. We described the process of renal injury after exposure to OME in mice; the early renal injury markers were increased in renal tubular epithelial cells (RTECs). And after long-term OME treatment, the OME-induced CKD mice model was established. Herein, aryl hydrocarbon receptor (AHR) translocation appeared after exposure to OME in HK-2 cells. Then for both in vivo and in vitro, we found that Ahr-knockout (KO) and AHR small interfering RNA (siRNA) substantially alleviated the OME-induced renal function impairment and tubular cell damage. Furthermore, our data demonstrate that antagonists of AHR and CYP1A1 could attenuate OME-induced tubular cell impairment in HK-2 cells. Taken together, these data indicate that OME induces CKD through the activation of the AHR-CYP axis in RTECs. Our findings suggest that blocking the AHR-CYP1A1 pathway acts as a potential strategy for the treatment of CKD caused by OME. KEY MESSAGES: We provide an omeprazole-induced chronic kidney disease (CKD) mice model. AHR activation and translocation process was involved in renal tubular damage and promoted the occurrence of CKD. The process of omeprazole nephrotoxicity can be ameliorated by blockade of the AHR-CYP1A1 axis.

Multiplexed PLGA scaffolds with nitric oxide-releasing zinc oxide and melatonin-modulated extracellular vesicles for severe chronic kidney disease

IntroductionWith prevalence of chronic kidney disease (CKD) in worldwide, the strategies to recover renal function via tissue regeneration could provide alternatives to kidney replacement therapies. However, due to relatively low reproducibility of renal basal cells and limited bioactivities of implanted biomaterials along with the high probability of substance-inducible inflammation and immunogenicity, kidney tissue regeneration could be challenging. ObjectivesTo exclude various side effects from cell transplantations, in this study, we have induced extracellular vesicles (EVs) incorporated cell-free hybrid PMEZ scaffolds. MethodsHybrid PMEZ scaffolds incorporating essential bioactive components, such as ricinoleic acid grafted Mg(OH)2 (M), extracellular matrix (E), and alpha lipoic acid-conjugated ZnO (Z) based on biodegradable porous PLGA (P) platform was successfully manufactured. Consecutively, for functional improvements, melatonin-modulated extracellular vesicles (mEVs), derived from the human umbilical cord MSCs in chemically defined media without serum impurities, were also loaded onto PMEZ scaffolds to construct the multiplexed PMEZ/mEV scaffold. ResultsWith functionalities of Mg(OH)2 and extracellular matrix-loaded PLGA scaffolds, the continuous nitric oxide-releasing property of modified ZnO and remarkably upregulated regenerative functionalities of mEVs showed significantly enhanced kidney regenerative activities. Based on these, the structural and functional restoration has been practically achieved in 5/6 nephrectomy mouse models that mimicked severe human CKD. ConclusionOur study has proved the combinatory bioactivities of the biodegradable PLGA-based multiplexed scaffold for kidney tissue regeneration in 5/6 nephrectomy mouse representing a severe CKD model. The optimal microenvironments for the morphogenetic formations of renal tissues and functional restorations have successfully achieved the combinatory bioactivities of remarkable components for PMEZ/mEV, which could be a promising therapeutic alternative for CKD treatment.

Novel biomarkers related to oxidative stress and immunity in chronic kidney disease

IntroductionThe incidence of chronic kidney disease (CKD) has been increasing in recent years, gradually becoming a global health crisis. Due to limited treatment options, novel molecular pathways are urgently required to advance the treatment and diagnosis of CKD. Materials and methodsThe characteristics of differentially expressed genes (DEGs) in CKD patients were analyzed using Gene Expression Omnibus (GEO) database, and genes related to oxidative stress were retrieved from the Genecard database. Subsequently, a comprehensive approach was applied, including immune infiltration analysis, weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network analysis, to identify hub genes among differentially expressed immune-related oxidative stress genes (DEIOSGs). Validation of hub genes was performed using an external data set, and diagnostic potential capability was evaluated through receiver operating curve (ROC) analysis. In animal experiments, the expression of hub genes in CKD was confirmed by inducing a CKD model through a 5/6 nephrectomy procedure. Finally, the relationship between these hub genes and clinical characteristics were assessed using the Nephroseq v5 database. Results29 DEIOSGs were identified by comprehensive bioinformatics analysis. PPI analysis screened the hub genes NCF2, S100A9, and SELL. ROC analysis demonstrated excellent diagnostic efficacy. Further validation from other databases and animal experiments confirmed a substantial upregulation in the expression of hub genes in CKD. Additionally, clinical correlation analysis established a clear link between hub gene expression and renal function deterioration. ConclusionsOur study confirms NCF2, S100A9, and SELL as diagnostic biomarkers associated with immune response and oxidative stress in CKD, suggesting their potential as novel targets for CKD diagnosis and treatment.

Liver and spleen predominantly mediate calciprotein particle clearance in a rat model of chronic kidney disease.

Calciprotein particles (CPPs) provide an efficient mineral buffering system to prevent the complexation of phosphate and calcium in the circulation. However, in chronic kidney disease (CKD), the phosphate load exceeds the mineral buffering capacity, resulting in the formation of crystalline CPP2 particles. CPP2 have been associated with cardiovascular events and mortality. Moreover, CPP2 have been demonstrated to induce calcification in vitro. In this study, we examined the fate of CPP2 in a rat model of CKD. Calcification was induced in Sprague-Dawley rats by 5/6 nephrectomy (5/6-Nx) combined with a high-phosphate diet. Control rats received sham surgery and high-phosphate diet. Twelve weeks after surgery, kidney failure was significantly induced in 5/6-Nx rats as determined by enhanced creatinine and urea plasma levels and abnormal kidney histological architecture. Subsequently, radioactive and fluorescent (FITC)-labeled CPP2 ([89Zr]Zr-CPP2-FITC) were injected intravenously to determine clearance in vivo. Using positron emission tomography scans and radioactive biodistribution measurements, it was demonstrated that [89Zr]Zr-CPP2-FITC are mainly present in the liver and spleen in both 5/6-Nx and sham rats. Immunohistochemistry showed that [89Zr]Zr-CPP2-FITC are predominantly taken up by Kupffer cells and macrophages. However, [89Zr]Zr-CPP2-FITC could also be detected in hepatocytes. In the different parts of the aorta and in the blood, low values of [89Zr]Zr-CPP2-FITC were detectable, independent of the presence of calcification. CPP2 are cleared rapidly from the circulation by the liver and spleen in a rat model of CKD. In the liver, Kupffer cells, macrophages, and hepatocytes contribute to CPP2 clearance.NEW & NOTEWORTHY Calciprotein particles (CPPs) buffer calcium and phosphate in the blood to prevent formation of crystals. In CKD, increased phosphate levels may exceed the buffering capacity of CPPs, resulting in crystalline CPPs that induce calcification. This study demonstrates that labeled CPPs are predominantly cleared from the circulation in the liver by Kupffer cells, macrophages, and hepatocytes. Our results suggest that targeting liver CPP clearance may reduce the burden of crystalline CPP in the development of vascular calcification.

In chronic kidney disease altered cardiac metabolism precedes cardiac hypertrophy.

Conduit arterial disease in chronic kidney disease (CKD) is an important cause of cardiac complications. Cardiac function in CKD has not been studied in the absence of arterial disease. In an Alport syndrome model bred not to have conduit arterial disease, mice at 225 days of life (dol) had CKD equivalent to humans with CKD stage 4-5. Parathyroid hormone (PTH) and FGF23 levels were one log order elevated, circulating sclerostin was elevated, and renal activin A was strongly induced. Aortic Ca levels were not increased, and vascular smooth muscle cell (VSMC) transdifferentiation was absent. The CKD mice were not hypertensive, and cardiac hypertrophy was absent. Freshly excised cardiac tissue respirometry (Oroboros) showed that ADP-stimulated O2 flux was diminished from 52 to 22 pmol/mg (P = 0.022). RNA-Seq of cardiac tissue from CKD mice revealed significantly decreased levels of cardiac mitochondrial oxidative phosphorylation genes. To examine the effect of activin A signaling, some Alport mice were treated with a monoclonal Ab to activin A or an isotype-matched IgG beginning at 75 days of life until euthanasia. Treatment with the activin A antibody (Ab) did not affect cardiac oxidative phosphorylation. However, the activin A antibody was active in the skeleton, disrupting the effect of CKD to stimulate osteoclast number, eroded surfaces, and the stimulation of osteoclast-driven remodeling. The data reported here show that cardiac mitochondrial respiration is impaired in CKD in the absence of conduit arterial disease. This is the first report of the direct effect of CKD on cardiac respiration.NEW & NOTEWORTHY Heart disease is an important morbidity of chronic kidney disease (CKD). Hypertension, vascular stiffness, and vascular calcification all contribute to cardiac pathophysiology. However, cardiac function in CKD devoid of vascular disease has not been studied. Here, in an animal model of human CKD without conduit arterial disease, we analyze cardiac respiration and discover that CKD directly impairs cardiac mitochondrial function by decreasing oxidative phosphorylation. Protection of cardiac oxidative phosphorylation may be a therapeutic target in CKD.