Renal fibrosis in feline chronic kidney disease: known mediators and mechanisms of injury

The ultrasonographic appearance of renal medullary striations and their association with renal disease and renal histopathology in domestic cats

Medullary striations (MS) have been anecdotally observed on ultrasound of feline kidneys; however, their significance is unknown. Aims of this retrospective, case control, pilot study were to describe the appearance, prevalence, and clinicopathological correlates of MS in a referral feline population. Still images from 1247 feline abdominal ultrasound studies performed between 2011 and 2021 were reviewed. Cats with MS were identified and compared with age-matched controls. Serum urea, creatinine, calcium, phosphate, and calcium-phosphate-product, plus urine specific gravity, urine protein: creatinine ratio (UPC), prevalence of active sediment (defined as > 5 red (RBC) or white blood cells (WBC) per high-power field) and prevalence of positive urine culture were compared between MS and control groups using the Mann-Whitney U test or Fisher's Exact test. Data are presented as median [range]. 27 cats were identified as having MS, giving a prevalence of 2.2% with a significantly higher proportion being seen in males (P = 0.018). Medullary striation cats had significantly higher UPC values than controls (0.46 [0.16-7.57] vs. 0.16 [0.07-2.27]; P = 0.006). Cats with MS were more likely to have active urinary sediments (39% vs 8%, P = 0.023), but no difference in prevalence of positive urinary cultures was observed between groups. There was no significant difference in other parameters between MS and control cats. Renal histopathology performed in three MS cats revealed focal regions of linear medullary fibrosis. Medullary striations are associated with proteinuria and urinary tract inflammation in cats, which may reflect renal tubular dysfunction and/or inflammation. Hence identification might allow for earlier detection of renal pathology.

Symmetric Dimethylarginine is a Promising Biomarker for the Early Detection of Age-Related Kidney Dysfunction in Zoo Felids

Chronic renal failure is one of the leading causes of death in African lions, cheetahs, and tigers. Conventional methods to measure renal dysfunction include measuring serum creatinine and blood urea nitrogen (BUN). Symmetric dimethylarginine (SDMA) measurement is a reliable predictor of renal dysfunction in the domestic cat because SDMA serum levels increase early when the kidneys are damaged. Serum SDMA levels were assessed and correlated with creatinine as well as BUN from healthy captive Bengal tigers and lions at the Everland Zoo in Korea. Serum SDMA concentrations were increasingly associated with increased age in lions. However, SDMA concentrations were higher in some young Bengal tigers than in older ones, which may allow for earlier renal dysfunction detection in these young cats than would be BUN and creatinine alone. In Bengal tigers, the correlation between the SDMA and BUN was slightly higher than that between SDMA and creatinine. In lions, SDMA correlated better with creatinine than with BUN concentration. These results show that serum SDMA concentration can be used as a biomarker for age-associated renal dysfunction. SDMA measurement may be an essential preventive management method in zoos.

Bone marrow mesenchymal stem cell-derived extracellular vesicles containing miR-181d protect rats against renal fibrosis by inhibiting KLF6 and the NF-κB signaling pathway

Recent studies have investigated the ability of extracellular vesicles (EVs) in regulating neighboring cells by transferring signaling molecules, such as microRNAs (miRs) in renal fibrosis. EVs released by bone marrow mesenchymal stem cells (BMSCs) contain miR-181d, which may represent a potential therapy for renal fibrosis. miR-181d has been speculated to regulate Krüppel-like factor 6 (KLF6), which activates the nuclear factor-kappa B (NF-κB) signaling pathway. Luciferase assays were performed to confirm the relationship between miR-181d and KLF6. Gain- and loss-of-function studies in vivo and in vitro were performed to assess the effect of BMSC-derived EVs (BMSC-EVs), which contained miR-181d, on KLF6, NF-κB, and renal fibrosis. Transforming growth factor-β (TGF-β)-induced renal tubular epithelial HK-2 cells were treated with EVs derived from BMSCs followed by evaluation of collagen type IV α1 (Col4α1), Collagen I and α-smooth muscle actin (α-SMA) as indicators of the extent of renal fibrosis. Renal fibrosis was induced in rats by unilateral ureteral obstruction (UUO) followed by the subsequent analysis of fibrotic markers. BMSC-EVs had higher miR-181d expression. Overexpression of miR-181d correlated with a decrease in KLF6 expression as well as the levels of IκBα phosphorylation, α-SMA, Col4α1, TGF-βR1 and collagen I in HK-2 cells. In vivo, treatment with miR-181d-containing BMSC-derived EVs was able to restrict the progression of fibrosis in UUO-induced rats. Together, BMSC-EVs suppress fibrosis in vitro and in vivo by delivering miR-181d to neighboring cells, where it targets KLF6 and inhibits the NF-κB signaling pathway.

Renal biomarkers in cats: A review of the current status in chronic kidney disease

Serum creatinine concentration, the classical biomarker of chronic kidney disease (CKD) in cats, has important limitations that decrease its value as a biomarker of early CKD. Recently, serum symmetric dimethylarginine concentration was introduced as a novel glomerular filtration rate biomarker for the early detection of CKD in cats. However, data on its specificity are still limited. The limitations of conventional biomarkers and the desire for early therapeutic intervention in cats with CKD to improve outcomes have prompted the discovery and validation of novel renal biomarkers to detect glomerular or tubular dysfunction. Changes in the serum or urinary concentrations of these biomarkers may indicate early kidney damage or predict the progression of kidney before changes in conventional biomarkers are detectable. This review summarizes current knowledge on renal biomarkers in CKD in cats, a field that has progressed substantially over the last 5 years.

Chemokine (C-C Motif) Ligand 8 and Tubulo-Interstitial Injury in Chronic Kidney Disease

Kidney fibrosis has been accepted to be a common pathological outcome of chronic kidney disease (CKD). We aimed to examine serum levels and tissue expression of chemokine (C-C motif) ligand 8 (CCL8) in patients with CKD and to investigate their association with kidney fibrosis in CKD model. Serum levels and tissue expression of CCL8 significantly increased with advancing CKD stage, proteinuria level, and pathologic deterioration. In Western blot analysis of primary cultured human tubular epithelial cells after induction of fibrosis with rTGF-β, CCL8 was upregulated by rTGF-β treatment and the simultaneous treatment with anti-CCL8 mAb mitigated the rTGF-β-induced an increase in fibronectin and a decrease E-cadherin and BCL-2 protein levels. The antiapoptotic effect of the anti-CCL8 mAb was also demonstrated by Annexin V/propidium iodide staining assay. In qRT-PCR analysis, mRNA expression levels of the markers for fibrosis and apoptosis showed similar expression patterns to those observed by western blotting. The immunohistochemical analysis revealed CCL8 and fibrosis- and apoptosis-related markers significantly increased in the unilateral ureteral obstruction model, which agrees with our in vitro findings. In conclusion, CCL8 pathway is associated with increased risk of kidney fibrosis and that CCL8 blockade can ameliorate kidney fibrosis and apoptosis.

The bi-directional effect of markers of inflammation and a decrease in glomerular filtration rate in chronic kidney disease

The aim of the study was to analyze and evaluate the relationship between the cytokine profile, C-reactive blood protein, fibrinogen, and glomerular filtration rate in patients with chronic kidney disease. The study involved individuals (n = 816) with chronic kidney disease (CKD) from the 1st to 5th stage of the disease, aged 20 to 76 years. The male to female ratio was 48% and 52%, respectively. All examined individuals underwent a comprehensive clinical and laboratory study evaluating the concentration of interleukins (IL, IL-10, IL-6, TNF-α) and acute phase inflammation proteins (C-reactive protein, fibrinogen) in the blood. CKD categories were evaluated by glomerular filtration rate (GFR), which was calculated using the CKD-EPI formula (Chronic Kidney Disease Epidemiology Collaboration). In individuals with CKD, significantly high concentrations of IL-10 and IL-6 were observed at stage 3b of the disease. Systolic blood pressure, median TNF-α, blood fibrinogen, and the number of individuals with high CRP were significant at stage 4 of CKD. A statistically significant correlation was found between the estimated GFR with the level of IL-6, CRP, blood fibrinogen at the 2nd stage of the disease and the concentration of IL-10 at 3b and TNF-α at the 4th stage of CKD. At the initial stage of CKD, there is a significant relationship between a decrease in estimated GFR and an increase in the level of IL-6, IL-10, TNF-α, as well as an increase in CRP and blood fibrinogen, which becomes pronounced at stages 3b and 4 of CKD.

Renal Senescence, Telomere Shortening and Nitrosative Stress in Feline Chronic Kidney Disease

Kidney tissues from cats with naturally occurring chronic kidney disease (CKD) and adult and senior cats without CKD were assessed to determine whether telomere shortening and nitrosative stress are associated with senescence in feline CKD. The histopathologic assessment of percent global glomerulosclerosis, inflammatory infiltrate, and fibrosis was performed. Senescence and nitrosative stress were evaluated utilizing p16 and iNOS immunohistochemistry, respectively. Renal telomere length was evaluated using telomere fluorescent in situ hybridization combined with immunohistochemistry. CKD cats were found to have significantly increased p16 staining in both the renal cortex and corticomedullary junction compared to adult and senior cats. Senior cats had significantly increased p16 staining in the corticomedullary junction compared to adult cats. p16 staining in both the renal cortex and corticomedullary junction were found to be significantly correlated with percent global glomerulosclerosis, cortical inflammatory infiltrate, and fibrosis scores. p16 staining also correlated with age in non-CKD cats. Average telomere length was significantly decreased in CKD cats compared to adult and senior cats. CKD cats had significantly increased iNOS staining compared to adult cats. Our results demonstrate increased renal senescence, telomere shortening, and nitrosative stress in feline CKD, identifying these patients as potential candidates for senolytic therapy with translational potential.

Is proteinuria a rare condition in apparently healthy and sick cats? A feline practice experience (2007-2018)

Background:

Proteinuria is assumed to be less frequent in cats than in dogs and is mainly associated with chronic kidney disease (CKD).

Aim:

The current study aimed to evaluate and compare urine protein-to-creatinine (UPC) values retrospectively in cats visited for comprehensive annual health check or for presenting systemic clinical signs related to CKD.

Methods:

UPC ratio was retrospectively evaluated in 112 owned cats, out of which 51 (45.5%) were apparently healthy cats according to their owners who visited for comprehensive annual health checks and 61 (54.5%) sick cats, presenting systemic clinical signs suggesting CKD, such as weight loss or polyuria/polydipsia, among others.

Results:

Based on UPC, the present study found that 54.5% of all cats included were borderline proteinuric or proteinuric, having increased UPC (UPC ≥ 0.2), with 35.7% included in the sick group and 18.7% in the health-check group. Increased UPC was also statistically associated with azotemia and isosthenuria (urinary-specific gravity between 1,008 and 1,035) in both sick and health-check groups of cats.

Conclusion:

Independent of the reason for their medical visit, it could be concluded that borderline proteinuria and proteinuria were statistically mainly related to CKD in cats. Furthermore, the measurement of UPC could be very useful in the detection and management of CKD in apparently healthy cats during a medical visit for annual health check irrespective of the age.

Clinical progression of cats with early-stage chronic kidney disease fed diets with varying protein and phosphorus contents and calcium to phosphorus ratios

Background

Dietary protein and phosphorus (P) restriction is the mainstay for nutritional management of chronic kidney disease (CKD). However, adequate restriction levels for cats with early CKD remain unclear.

Objectives

To investigate responses in cats with early CKD to varying dietary protein, P, and calcium (Ca) : P ratio.

Animals

Nineteen research colony cats with International Renal Interest Society stages 1‐2 CKD.

Methods

In an opportunistic longitudinal case study, cats were fed a low protein (59 g/Mcal), low P (0.84 g/Mcal) dry diet (LP‐LP; Ca : P = 1.9) for 18 months and later transitioned onto a moderate protein (76‐98 g/Mcal), moderate P (1.4‐1.6 g/Mcal) dry‐wet diet regimen (MP‐MP; Ca : P = 1.4‐1.6) for 22 months. Fold‐changes in serum creatinine, total Ca (tCa) and P (primary outcomes) and fibroblast growth factor 23 (FGF23) were assessed by linear‐mixed models.

Results

While feeding LP‐LP, mean serum creatinine decreased (0.87‐fold, 95% confidence interval [CI] 0.81, 0.93, P < .001) to within reference range after 6 months, while increases in total Ca (tCa; 1.16‐fold, 95% CI 1.11, 1.22, P < .001) and FGF23 (2.72‐fold, 95% CI 1.72, 4.31, P < .001), but not in P (1.03‐fold, 95% CI 0.945, 1.124, P = .94), were observed after 17 months. On MP‐MP, mean creatinine, tCa and P remained within reference ranges and did not significantly change (P = .11, P = .98, and P = 1, respectively), while FGF23 significantly decreased (0.58‐fold, 95% CI 0.36, 0.95, P = .02) after 22 months.

Conclusions and Clinical Importance

Cats with early CKD developed hypercalcemia after long‐term feeding of a highly P‐restricted diet. Increasing dietary P and reducing Ca : P ratio maintained renal markers, while improving Ca‐P balance. Cats with early CKD could benefit from moderately protein‐ and P‐restricted diets.

Mesenchymal stem cells transplantation attenuates hyperuricemic nephropathy in rats

Mesenchymal stem cells (MSCs), due to their multi-directional differentiation, paracrine and immunomodulation potentials, and the capacity of homing to target organ, have been reported to facilitate regeneration and repair of kidney and improve kidney function in acute or chronic kidney injury. The present study was aimed to evaluate whether MSCs could have a protective effect in hyperuricemic nephropathy (HN) and the underlying mechanisms. A rat HN model was established by oral administration of a mixture of potassium oxonate (PO, 1.5 g/kg) and adenine (Ad, 50 mg/kg) daily for 4 weeks. For MSCs treatment, MSCs (3 × 10⁶ cells/kg per week) were injected via tail vein from the 2nd week for 3 times. The results showed that along with the elevated uric acid (UA) in HN rats, creatinine (CREA), blood urea nitrogen (BUN), microalbuminuria (MAU) and 24-hour urinary protein levels were significantly increased comparing with the normal control rats, while decreased after MSCs treatment. Moreover, the mRNA levels of inflammation and fibrosis-related gene were reduced in UA + MSCs group. Consistently, hematoxylin-eosin (HE) staining results showed the destruction of kidney structure and fibrosis were significantly alleviated after MSCs administration. Similarly, in vitro, NRK-52Es cells were treated with high concentration UA (10 mg/dL) in the presence of MSCs, and we found that MSCs co-culture could inhibited UA-induced cell injury, characterized as improvement of cell viability and proliferation, inhibition of apoptosis, inflammation, and fibrosis. Collectively, MSCs treatment could effectively attenuate UA-induced renal injury, and thus it might be a potential therapy to hyperuricemia-related renal diseases.

Hypoxia and chronic kidney disease: Possible mechanisms, therapeutic targets, and relevance to cats

There is mounting evidence that kidney ischaemia/hypoxia plays an important role in feline chronic kidney disease (CKD) development and progression, as well as in human disease and laboratory animal models. Ischaemic acute kidney injury is widely accepted as a cause of CKD in people and data from laboratory species has identified some of the pathways underlying this continuum. Experimental kidney ischaemia in cats results in morphological changes, namely chronic tubulointerstitial inflammation, tubulointerstitial fibrosis, and tubular atrophy, akin to those observed in naturally-occurring CKD. Multiple situations are envisaged that could result in acute or chronic episodes of kidney hypoxia in cats, while risk factors identified in epidemiological studies provide further support that kidney hypoxia contributes to spontaneously occurring feline CKD. This review evaluates the evidence for the role of kidney ischaemia/hypoxia in feline CKD and the proposed mechanisms and consequences of kidney hypoxia. As no effective treatments exist that substantially slow or prevent feline CKD progression, there is a need for novel therapeutic strategies. Targeting kidney hypoxia is one such promising approach, with therapies including those that attenuate the hypoxia-inducible factor (HIF) pathway already being utilised in human CKD.

Analysis of genes associated with proinflammatory and profibrotic pathways upregulated in ischemia-induced chronic kidney disease in cats

OBJECTIVE

To use RNA sequencing (RNAseq) to characterize renal transcriptional activities of genes associated with proinflammatory and profibrotic pathways in ischemia-induced chronic kidney disease (CKD) in cats.

SAMPLES

Banked renal tissues from 6 cats with experimentally induced CKD (renal ischemia [RI] group) and 9 healthy cats (control group).

PROCEDURES

Transcriptome analysis with RNAseq, followed by gene ontology and cluster analyses, were performed on banked tissue samples of the right kidneys (control kidneys) from cats in the control group and of both kidneys from cats in the RI group, in which unilateral (right) RI had been induced 6 months before the cats were euthanized and the ischemic kidneys (IKs) and contralateral nonischemic kidneys (CNIKs) were harvested. Results for the IKs, CNIKs, and control kidneys were compared to identify potential differentially expressed genes and overrepresented proinflammatory and profibrotic pathways.

RESULTS

Genes from the gene ontology pathways of collagen binding (eg, transforming growth factor-β1), metalloendopeptidase activity (eg, metalloproteinase [MMP]-7, MMP-9, MMP-11, MMP-13, MMP-16, MMP-23B, and MMP-28), chemokine activity, and T-cell migration were overrepresented as upregulated in tissue samples of the IKs versus control kidneys. Genes associated with the extracellular matrix (eg, TIMP-1, fibulin-1, secreted phosphoprotein-1, matrix Gla protein, and connective tissue growth factor) were upregulated in tissue samples from both the IKs and CNIKs, compared with tissues from the control kidneys.

CONCLUSIONS AND CLINICAL RELEVANCE

Unilateral ischemic injury differentially altered gene expression in both kidneys, compared with control kidneys. Fibulin-1, secreted phosphoprotein-1, and matrix Gla protein may be candidate biomarkers of active kidney injury in cats.

Chemokine Therapy in Cats With Experimental Renal Fibrosis and in a Kidney Disease Pilot Study

Background: Chronic tubulointerstitial fibrosis is a common final pathway leading to end stage kidney disease in cats and has no effective treatment. The use of cell-based molecules to treat kidney fibrosis may be a promising approach. The objectives were to test the effects of intra-renal chemokine CXCL12 injection in a pre-clinical cat model of unilateral ischemia/reperfusion (I/R)-induced kidney fibrosis and then, within a clinical pilot study, test the safety/feasibility of CXCL12 injection in cats that might have early chronic kidney disease (CKD). Methods: Pre-clinical: Thirty cats received intra-renal injection of 100, 200, or 400 ng of recombinant human CXCL12, or sterile saline, into the I/R kidney 70 days post-injury, or were non-injured, non-injected controls (n = 6/group). Kidney collagen content was quantified 4 months post-treatment using Masson's Trichrome and Picrosirius Red (PSR) stained tissues. In a separate study (n = 2) exploring short-term effects of CXCL12, 200 ng CXCL12 was injected into I/R kidneys and then harvested either 30 min (n = 1) or 1 month (n = 1) post-injection. Kidney concentrations of CXCL12, matrix metalloproteinase 1 (MMP-1), and lysyl oxidase-like enzyme 2 (LOXL-2) were quantified via ELISA. Clinical Pilot: 14 client-owned cats with potential early kidney disease received a single-treatment, bilateral intra-renal injection of 200 ng CXCL12 (n = 7), or received no injection (n = 7). Blood/urine samples were collected monthly for 9 months to assess renal function and CKD staging. Results: Pre-clinical: I/R increased the affected kidney collagen content, which both mid and high doses of CXCL12 restored to normal (ps < 0.05 vs. untreated). I/R increased collagen fiber width, which both mid and high doses of CXCL12 restored to normal (p < 0.001 vs. untreated). Early changes in kidney MMP-1, associated with collagen breakdown, and subsequent decreases in LOXL-2, associated with collagen cross-linking, in response to CXCL12 treatment may contribute to these findings. Clinical Pilot: Bilateral intra-renal injection of CXCL12 using ultrasound guidance in cats with CKD was feasible and safe in a general practice clinical setting with no obvious side effects noted during the 9-month follow-up period. Conclusions: Intra-renal injection of CXCL12 may prove to be an effective treatment for kidney fibrosis in cats with CKD. Additional mechanistic and clinical evaluations are needed.

Naringin attenuates renal interstitial fibrosis by regulating the TGF-β/Smad signaling pathway and inflammation

Interstitial fibrosis is a typical feature of all progressive renal diseases. The process of fibrosis is frequently coupled with the presence of pro-fibrotic factors and inflammation. Naringin is a dihydroflavone compound that has been previously reported to exhibit anti-fibrotic effects in the liver, where it prevents oxidative damage. In the present study, a rat model of renal interstitial fibrosis and fibrosis cell model were established to evaluate the effects of naringin on inflammatory proteins and fibrosis markers in kidney of rats and NRK-52E cells, and to elucidate the role of the TGF-β/Smad signaling pathway in this mechanism. Compared with those in fibrotic NRK-52E cells that were stimulated by transforming growth factor-β (TGF-β), gene expression levels of α-smooth muscle actin (α-SMA), collagen 1 (COL1A1), collagen 3 (COL3A1), interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α) were all found to be significantly decreased in fibrotic NRK-52E cells following treatment with naringin (50, 100 and 200 ng/ml). Results from the histopathological studies showed that naringin treatment preserved the renal tissue structure and reduced the degree of fibrosis in the kidney tissues of rats that underwent unilateral ureteral obstruction (UUO). In addition, naringin administration reduced the expression of α-SMA, COL1A1, COL3A1, IL-1β, IL-6 and TNF-α in the kidneys of rats following UUO. The current study, using western blot analysis, indicated that naringin also downregulated the activation of Smad2/3 and the expression of Smad4, high-mobility group protein B1, activator protein-1, NF-κB and cyclooxygenase-2 whilst upregulating the expression of Smad7 in fibrotic NRK-52E cells and rats in the UUO group. In conclusion, naringin could antagonize renal interstitial fibrosis by regulating the TGF-β/Smad pathway and the expression of inflammatory factors.

Evaluation of Urinary Big Endothelin-1 in Feline Spontaneous CKD

Simple Summary

Chronic kidney disease is a common and progressive disease of elderly cats. It is a cause of pet suffering and owner expense. Biologic biomarkers for early diagnosis and for noninvasive evaluation of kidney damage are certainly useful in both research and clinical practice. In this study, we evaluated the biomarker big endotelin-1 in the urine of cats affected with chronic kidney disease. Big endothelin-1 is molecule linked to inflammation and pressure regulation, and it was not previously evaluated in nephropathic cats. We found that urinary big endothelin was increased in patients at late stage of the disease and in patients with proteinuria (a marker of kidney damage). Despite that, big endothelin 1 seemed not to be a useful biomarker for disease progression. According to results of this preliminary study, we suggest this biomarker for future research on feline kidney disease.

Abstract

The endothelin-1 (ET-1) system has been implicated in the development and progression of chronic kidney disease (CKD). No information on big ET-1 in feline urine is available. The purpose of this study was to evaluate if urinary big endothelin-1 (bigET-1) is associated with feline CKD. Sixty urine samples were prospectively collected from 13 healthy cats at risk of developing CKD and 22 cats with CKD of different International Renal Interest Society (IRIS) stages (1–4). Urinary bigET-1 was measured using a commercially available ELISA. BigET-1 normalized to urine creatinine (bigET-1:UC) was compared amongst stages and substages, as proposed by IRIS, and correlated with serum creatinine concentration, proteinuria and blood pressure. BigET-1:UC at the time of inclusion was compared between cats that remained stable and cats that progressed after 12 months. BigET-1:UC was significantly higher (p = 0.002) in cats at IRIS stages 3–4 (median: 21.9; range: 1.88–55.6), compared to all other stages, and in proteinuric (n = 8, median: 11.0; range: 0.00–46.4) compared with nonproteinuric cats (n = 38 median: 0.33; range: 0.00–55.6) (p = 0.029). BigET-1:UC was not associated with CKD progression. Urinary bigET-1 increased in advanced stages of CKD and in proteinuric patients, suggesting that ET-1 may be indicative of the severity of feline CKD.

The association of bacteriuria with survival and disease progression in cats with azotemic chronic kidney disease

BACKGROUND

Cats with chronic kidney disease (CKD) have an increased prevalence of positive urine cultures (PUC). Limited information is available regarding the prognosis of cats with CKD and concurrent PUC.

OBJECTIVE

To determine the association of PUC with survival time and disease progression in cats with CKD.

ANIMALS

Medical records of 509 cats diagnosed with azotemic CKD between 1997 and 2018.

METHODS

Cats were classified as having "no-PUC" or "PUC." The PUC cats were further classified as having 1 or multiple PUC, and also were classified based on the presence or absence of clinical signs of urinary tract infection (UTI). Progression of CKD was defined as a plasma creatinine concentration increase of ≥25% within 365 days of CKD diagnosis; PUC also must have occurred within this time frame. Survival time and frequency of CKD progression were compared between groups.

RESULTS

No significant difference in survival time was found between cats with no-PUC and cats with any number of PUC (P = .91), or between cats with no-PUC, 1 PUC or multiple PUC (P = .37). Also, no significant difference was found in the frequency of CKD progression between PUC and no-PUC cats (P = .5), or among no-PUC, 1 PUC and multiple PUC cats (P = .22). When assessing cats with clinical signs of lower UTI, no significant difference was found in the frequency of CKD progression between cats with true UTI, subclinical bacteriuria or no-PUC (P = .8).

CONCLUSIONS AND CLINICAL IMPORTANCE

When treated with antibiotics, PUC in cats with CKD do not affect disease progression or survival time.

Renal ultrasonographic shear-wave elastography and urinary procollagen type III amino-terminal propeptide in chronic kidney disease dogs

Background and Aim:

Renal fibrosis is a well-established pathological alteration associated with chronic kidney disease (CKD) in several species and progresses as CKD advances. Although a renal biopsy is the gold standard for determining renal fibrosis, it is an invasive, impractical method for clinical practice. In humans, ultrasonographic shear-wave elastography (SWE), a novel advanced diagnostic imaging tool, can evaluate renal parenchyma stiffness, and urinary procollagen type III amino-terminal propeptide (uPIIINP), a promising renal fibrosis biomarker in humans, has increasingly been use applied to reduce the biopsies. This study compares renal tissue elasticity observed through SWE Young’s modulus (E) values between healthy dogs (HD) and those with CKD.

Materials and Methods:

The E value acquired by SWE, uPIIINP levels, and renal function were evaluated in 15 CKD dogs and 15 HD.

Results:

The renal cortical E values were significantly higher than the renal medullary E values in both groups (p<0.001). Renal cortical and medullary E values in CKD dogs were significantly higher than in HD (p<0.01). Cortical E values had greater significant correlations with renal functional parameters than the medullary E values and had a significant positive correlation with concentrations of plasma creatinine (Cr) (p<0.001); blood urea nitrogen (p<0.01); urine protein Cr ratio (p<0.01); and fractional excretions of sodium (p<0.05), potassium (p<0.05), chloride (p<0.05), and magnesium (p<0.001) while they had a negative correlation with urine specific gravity (p<0.05) and urine osmolality to plasma osmolality ratio (p<0.05). The uPIIINP to Cr (uPIIINP/Cr) ratios of CKD dogs were higher than those of HD (p<0.001). Moreover, the uPIIINP/Cr levels presented significant correlations with the renal cortical E values (p<0.01) and also the renal functional parameters.

Conclusion:

SWE offers a complementary, non-invasive diagnostic imaging tool for evaluating renal tissue stiffness in CKD dogs with renal function deterioration. In addition, uPIIINP levels are associated with renal function and structural changes in dogs. Therefore, the uPIIINP level might be a non-invasive, complementary, and promising biomarker for evaluating renal fibrosis in canine CKD.

An artificial neural network-based model to predict chronic kidney disease in aged cats

BACKGROUND

Chronic kidney disease (CKD) frequently causes death in older cats; its early detection is challenging.

OBJECTIVES

To build a sensitive and specific model for early prediction of CKD in cats using artificial neural network (ANN) techniques applied to routine health screening data.

ANIMALS

Data from 218 healthy cats ≥7 years of age screened at the Royal Veterinary College (RVC) were used for model building. Performance was tested using data from 3546 cats in the Banfield Pet Hospital records and an additional 60 RCV cats-all initially without a CKD diagnosis.

METHODS

Artificial neural network (ANN) modeling used a multilayer feed-forward neural network incorporating a back-propagation algorithm. Clinical variables from single cat visits were selected using factorial discriminant analysis. Independent submodels were built for different prediction time frames. Two decision threshold strategies were investigated.

RESULTS

Input variables retained were plasma creatinine and blood urea concentrations, and urine specific gravity. For prediction of CKD within 12 months, the model had accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 88%, 87%, 70%, 53%, and 92%, respectively. An alternative decision threshold increased specificity and PPV to 98% and 87%, but decreased sensitivity and NPV to 42% and 79%, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

A model was generated that identified cats in the general population ≥7 years of age that are at risk of developing CKD within 12 months. These individuals can be recommended for further investigation and monitoring more frequently than annually. Predictions were based on single visits using common clinical variables.

Expression analysis of protease-activated receptor-2 in cats

Chronic kidney disease (CKD) is a common disease in geriatric cats. Despite its high prevalence, the pathogenesis of feline CKD is poorly understood. Recently, there has been increasing evidence for the role of protease-activated receptor-2 (PAR-2) in the progression of CKD in humans and rodents. However, the role of PAR-2 in feline CKD has not been evaluated. In this study, we determined nucleotide sequence of feline PAR-2 from the kidney, evaluated PAR-2 mRNA and protein expression in normal feline tissues, and analyzed functional expression in the feline kidney epithelial cell line Crandell-Rees Feline Kidney (CRFK). The open reading frame of feline PAR-2 comprised 1,194 bp and encoded 397 amino acids, showing 90%, 90%, and 85% identities to human, dog, and mouse PAR-2, respectively. In healthy cats, expression levels of the PAR-2 mRNA and protein were relatively higher in the gastrointestinal tract and kidney, and was lowest in the heart. The feline PAR-2 protein expression was confirmed, and stimulation of trypsin and PAR-2 agonists induced a prompt increase in the intracellular calcium ion concentration in CRFK cells. The present study will provide fundamental information for investigation of the involvement of PAR-2 in the pathogenesis of CKD in cats.

Endothelin converting enzyme-1 (ECE-1) deletion in association with Endothelin-1 downregulation ameliorates kidney fibrosis in mice

Kidney fibrosis is a common final pathway of chronic kidney diseases, which are characterized by renal architecture damage, inflammation, fibroblast expansion and myofibroblast formation. Endothelin converting enzyme-1 (ECE-1) contributes to activation of Endothelin-1 (ET-1), a potent vasoconstrictor and pro-fibrotic substance. This study elucidated the effect of ECE-1 knockout in kidney fibrosis model in mice in association of ET-1 downregulation. Kidney fibrosis was performed in ECE-1 knockout (ECE-1 KO) and vascular endothelial derived ET-1 KO (VEETKO) mice (2 months, 20-30 g, n = 30) and their wild type (WT) littermates using unilateral ureteral obstruction (UUO) procedure. Mice were euthanized on day-7 and day-14 after UUO. Histopathological analysis was conducted for fibrosis and tubular injury. Immunostainings were done to quantify macrophages (F4/80), fibroblasts (FSP-1) and myofibroblasts (α-SMA). Monocyte Chemoattractant Protein-1 (MCP-1), ECE-1 and preproET-1 (ppET-1) mRNA expression were quantified with qRT-PCR, while Transforming Growth Factor-β1 (TGF-β1) and α-SMA protein level were quantified with Western blot. ECE-1 KO mice demonstrated reduction of ECE-1 and ppET-1 mRNA expression, attenuation of kidney fibrosis, tubular injury, MCP-1 mRNA expression and macrophage number compared to WT. Double immunostaining revealed fibroblast to myofibroblast formation after UUO, while ECE-1 KO mice had significantly lower fibroblast number and myofibroblast formation compared to WT, which were associated with significantly lower TGF-β1 and α-SMA protein levels in day-14 of UUO. VEETKO mice also demonstrated attenuation of ET-1 protein level, fibrosis and myofibroblast formation. In conclusion, ECE-1 knockout and ET-1 downregulation attenuated kidney fibrosis.

Fyn Kinase: A Potential Therapeutic Target in Acute Kidney Injury

Acute kidney injury (AKI) is a common disease with a complex pathophysiology which significantly contributes to the development of chronic kidney disease and end stage kidney failure. Preventing AKI can consequently reduce mortality, morbidity, and healthcare burden. However, there are no effective drugs in use for either prevention or treatment of AKI. Developing therapeutic agents with pleiotropic effects covering multiple pathophysiological pathways are likely to be more effective in attenuating AKI. Fyn, a non-receptor tyrosine kinase, has been acknowledged to integrate multiple injurious stimuli in the kidney. Limited studies have shown increased Fyn transcription level and activation under experimental AKI. Activated Fyn kinase propagates various downstream signaling pathways associated to the progression of AKI, such as oxidative stress, inflammation, endoplasmic reticulum stress, as well as autophagy dysfunction. The versatility of Fyn kinase in mediating various pathophysiological pathways suggests that its inhibition can be a potential strategy in attenuating AKI.

Identification of CD2, CCL5 and CCR5 as potential therapeutic target genes for renal interstitial fibrosis

Background

We aimed to explore potential gene biomarkers of renal interstitial fibrosis (RIF) due to a lack of effective and non-invasive methods for diagnosis.

Methods

Three data sets (GSE22459, GSE76882 and GSE57731) including 350 samples were acquired from Gene Expression Omnibus (GEO) database. We used bioconductor limma package to perform background adjustment. Cluster analysis was conducted by 'edgeR' package to identify the differentially expressed genes (DEGs). We generated heat maps with using heatmap package in R software. Function annotation of genes was performed by Gene Ontology (GO) enrichment analysis. STRING (Search Tool for the Retrieval of Interacting Genes) database was employed to construct the protein-protein interaction (PPI) network and the results were visualized by Cytoscape 3.6.1. At last, we applied Graphpad Prism 7.0. to explore the correlation between three hub genes and pathological degrees of RIF.

Results

By applying the "edgeR" package in R, we detected 116 DEGs with three data sets. These genes were enriched in 19 GO biological process categories. Three main hub genes (CD2, CCL5 and CCR5) were identified after construction of PPI network. In Pearson correlation coefficient, CD2, CCL5 and CCR5 was found to hold higher expression patterns in RIF samples based on independent data set GSE57731. Besides, their gene expression levels were found significantly positive correlation with the degree of RIF (CD2: P<0.05, r=0.29; CCL5: P<0.05, r=0.31; CCR5: P<0.05, r=0.38).

Conclusions

CD2, CCL5 and CCR5 might serve as potential early biomarkers of RIF. The mechanism between these genes and RIF remains to be further studied.

Immune-complex glomerulonephritis in cats: a retrospective study based on clinico-pathological data, histopathology and ultrastructural features

BACKGROUND

Chronic kidney disease (CKD) has typically a non-immune mediated origin in cats and immune-complex glomerulonephritis (ICGN) is scarcely described. Aims of this study were to characterize ICGN by light and electron microscopy and identify associations with clinico-pathological findings. In addition, comparisons between cats with ICGN and non immune-complex glomerulonephritis (non-ICGN) were performed. Renal samples examined between 2010 and 2019 were considered if both light and electron microscopy were performed. Signalment, feline immunodeficiency virus (FIV) and leukemia virus (FeLV) status, serum creatinine concentration, urine protein-to-creatinine (UPC) ratio, systolic blood pressure (SBP) and International Renal Interest Society (IRIS) stage were retrieved and used for comparisons.

RESULTS

Sixty-eight client-owned cats were included. Thirty-seven cats (54.4%) had ICGN and 31 (45.6%) non-ICGN. Eighteen (48.6%) with ICGN had membranous glomerulonephropathy (MGN), 14 (37.8%) membranoproliferative glomerulonephritis (MPGN), and 5 (13.5%) mesangioproliferative glomerulonephritis (MeGN). Clinico-pathological data were not associated with any type of ICGN. Among cats with non-ICGN, 11 (35.5%) had end-stage CKD, 9 (29%) focal segmental glomerulosclerosis, 6 (19.4%) global and multifocal mesangiosclerosis, 2 (6.5%) glomerular atrophy, 2 (6.5%) renal dysplasia and 1 (3.1%) amyloidosis. Eight (25.8%) cats with non-ICGN had chronic interstitial nephritis (CIN) grade 1, 13 (41.9%) grade 2 and 10 (32.3%) grade 3; creatinine and UPC ratio increased with CIN grades (p = 0.001, p < 0.001). Cats with ICGN were more frequently FIV or FeLV-infected (OR:11.4; 95%CI:1.4-94.4; p = 0.024), had higher UPC ratio (OR:6.8; 95%CI:2.5-18.2; p < 0.001) and were younger (OR:0.9; 95%CI:0.7-1.0; p = 0.042) than cats with non-ICGN.

CONCLUSIONS

MGN and MPGN were the most common morphological diagnoses of ICGN in cats. Unfortunately, none of the investigated findings differentiated ICGN morphological diagnoses. Serum creatinine concentration and UPC ratio were directly associated with grades of CIN (p = 0.001 and p < 0.001, respectively), confirming previous literature. More ICGN than non-ICGN was observed in cats with retroviral infections, younger cats and higher UPC ratio.

Alterations in Lipid Profile of the Aging Kidney Identified by MALDI Imaging Mass Spectrometry

During aging, the kidney undergoes functional and physiological changes that are closely affiliated with chronic kidney disease (CKD). There is increasing evidence supporting the role of lipid or lipid-derived mediators in the pathogenesis of CKD and other aging-related diseases. To understand the role of lipids in various metabolic processes during kidney aging, we conducted matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS) analysis in kidneys harvested from young (2 months old, n = 3) and old mice (24 months old, n = 3). MALDI-IMS analysis showed an increase in ceramide level and a decrease in sphingomyelin (SM) and phosphatidylcholine (PC) levels in kidneys of old mice. The increased expression of cPLA2 and SMPD1 protein in aged kidney was confirmed by immunohistochemistry and Western blot analysis. Our MALDI-IMS data showed the altered distribution of lipids in aged kidney as indicative of aging-related functional changes of the kidney. Combined analysis of MALDI-IMS and IHC confirmed lipidomic changes and expression levels of responsible enzymes as well as morphological changes.

Renal shear wave elastography and urinary procollagen type III amino-terminal propeptide (uPIIINP) in feline chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is one of the most common diseases occurring in cats. It is characterized by renal fibrosis, which is strongly correlated with impairment of renal function. Since renal biopsy is not performed routinely in clinical practice, the non-invasive method of ultrasonographic shear-wave elastography (SWE) was used to determine renal parenchymal stiffness. Currently, urinary procollagen type III amino-terminal propeptide (uPIIINP) is a renal fibrosis biomarker in humans. Moreover, PIIINP is increasingly applied for identification of fibrosis in various organs in animals.

RESULTS

The Young's modulus (E) value on SWE, uPIIINP, and renal function were evaluated in 23 CKD cats and 25 healthy cats (HC). The renal cortical E values were significantly higher than those of the renal medulla in both groups (P < 0.001). The E values of the renal cortex and medulla were significantly higher in CKD cats than in HC (P < 0.001 and P < 0.01, respectively). The E values, especially of the cortex, showed a significant positive correlation with concentrations of plasma creatinine (P < 0.001), blood urea nitrogen (P < 0.05), while they had a negative correlation with urine specific gravity (P < 0.001) and urine osmolality per plasma osmolality ratio (P < 0.01). The uPIIINP to creatinine ratios (uPIIINP/Cr) were significantly higher in CKD cats than in HC (P < 0.01) and were highly correlated with renal cortical E values (P < 0.001).

CONCLUSIONS

SWE might be an additively useful and non-invasive diagnostic imaging tool to evaluate renal parenchymal stiffness, which correlates with renal functional impairment in CKD cats. Moreover, the uPIIINP/Cr might be a promissing biomarker for adjunctive assessing the renal fibrosis in feline CKD.

Roles of Mesenchymal Stem Cells in Tissue Regeneration and Immunomodulation

Mesenchymal stem cells are classified as multipotent stem cells, due to their capability to transdifferentiate into various lineages that develop from mesoderm. Their popular appeal as cell-based therapy was initially based on the idea of their ability to restore tissue because of their differentiation potential in vitro; however, the lack of evidence of their differentiation to target cells in vivo led researchers to focus on their secreted trophic factors and their role as potential powerhouses on regulation of factors under different immunological environments and recover homeostasis. To date there are more than 800 clinical trials on humans related to MSCs as therapy, not to mention that in animals is actively being applied as therapeutic resource, though it has not been officially approved as one. But just as how results from clinical trials are important, so is to reveal the biological mechanisms involved on how these cells exert their healing properties to further enhance the application of MSCs on potential patients. In this review, we describe characteristics of MSCs, evaluate their benefits as tissue regenerative therapy and combination therapy, as well as their immunological properties, activation of MSCs that dictate their secreted factors, interactions with other immune cells, such as T cells and possible mechanisms and pathways involved in these interactions.

Extracellular matrix roles in cardiorenal fibrosis: Potential therapeutic targets for CVD and CKD in the elderly

Whereas hypertension, diabetes, and dyslipidemia are age-related risk factors for cardiovascular disease (CVD) and chronic kidney disease (CKD), aging alone is an independent risk factor. With advancing age, the heart and kidney gradually but significantly undergo inflammation and subsequent fibrosis, which eventually results in an irreversible decline in organ physiology. Through cardiorenal network interactions, cardiac dysfunction leads to and responds to renal injury, and both facilitate aging effects. Thus, a comprehensive strategy is needed to evaluate the cardiorenal aging network. Common hallmarks shared across systems include extracellular matrix (ECM) accumulation, along with upregulation of matrix metalloproteinases (MMPs) including MMP-9. The wide range of MMP-9 substrates, including ECM components and inflammatory cytokines, implicates MMP-9 in a variety of pathological and age-related processes. In particular, there is strong evidence that inflammatory cell-derived MMP-9 exacerbates cardiorenal aging. This review explores the potential therapeutic targets against CVD and CKD in the elderly, focusing on ECM and MMP roles.

Salvianolic acid A attenuates kidney injury and inflammation by inhibiting NF-κB and p38 MAPK signaling pathways in 5/6 nephrectomized rats

Salvianolic acid A (SAA) is a minor phenolic carboxylic acid extracted from Salviae miltiorrhizae Bunge (Danshen). SAA exhibits a variety of pharmacological activities, such as antioxidative, anti-thrombotic, neuroprotective, and anti-fibrotic effects, as well as protection from myocardial ischemia and prevention of diabetes and other diseases. Furthermore, SAA has shown renal-protective effects in doxorubicin-induced nephropathy. However, there has been limited research regarding the effects of SAA and underlying mechanisms in chronic kidney disease (CKD). Here, we examined the effects and molecular mechanisms of SAA in an established animal model of 5/6 nephrectomized (5/6Nx) rats. The rats were injected with SAA (2.5, 5, and 10 mg/kg per day, intraperitoneally (ip)) for 28 days. SAA dose-dependently lowered the levels of urine protein, blood urea nitrogen, serum creatinine, plasma total cholesterol, and plasma triglycerides in 5/6Nx rats. Histological examination revealed that SAA dose-dependently attenuated renal pathological lesions, evidenced by reduced renal tubulointerstitial fibrosis by decreasing the expression levels of tumor growth factor-β1 and α-smooth muscle actin in 5/6Nx rats. Moreover, SAA dose-dependently inhibited the activation of nuclear factor-κB (NF-κB) and p38 mitogen-activated protein kinase (MAPK) signaling pathways, subsequently attenuating the secretion of tumor necrosis factor-α and interleukin-1β and inhibiting the expression of monocyte chemotactic protein-1, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in kidneys of 5/6Nx rats. The above results were consistent with those obtained in lipopolysaccharide-induced HK-2 cells in vitro (a recognized in vitro inflammatory model). In conclusion, our results demonstrated that SAA effectively attenuates kidney injury in 5/6Nx rats. The therapeutic effects of SAA on kidney injury can be attributed to its anti-inflammatory activities through inhibition of the activation of the NF-κB and p38 MAPK signaling pathways.

Surfactant protein A induces the pathogenesis of renal fibrosis through binding to calreticulin

Renal fibrosis is a significant characteristic of chronic kidney diseases. Surfactant protein A (SP-A) is a recently identified fibrosis-associated factor in lung fibrosis; however, whether SP-A has the same role in renal fibrosis has remained elusive. The aim of the present study was to investigate the role of SP-A and its receptor calreticulin (CRT) in the pathogenesis of kidney fibrosis. The HK-2 human tubular epithelial cell line was cultured and treated with SP-A and SP-A + anti-CRT. The production of reactive oxygen species (ROS) at 30, 60 and 120 min was examined. Furthermore, cell apoptosis was assessed using an Annexin V assay and the expression of various proteins was measured using western blot analysis. In addition, the cell culture supernatants were collected and the expression of type I collagen was examined using ELISA. Compared with the control group, SP-A treatment significantly increased the ROS production, type I collagen secretion and cell apoptosis, which was partially inhibited by addition of anti-CRT. Furthermore, downregulation of matrix metalloproteinase (MMP)2 and -9 as well as upregulation of tissue inhibitor of metalloproteinase 1 indicated that SP-A treatment increased the degree of fibrosis in HK-2 cells, while addition of anti-CRT alleviated the fibrotic conditions. Finally, SP-A treatment significantly increased the expression of phosphorylated (p)-p38, p-p-65 and NADPH oxidase 2, which was partially inhibited by addition of anti-CRT. In conclusion, SP-A may participate in the pathogenesis of kidney fibrosis through binding to CRT and activate the mitogen-activated protein kinase/nuclear factor-κB-associated oxidative stress signaling pathway.

Profibrotic effects of angiotensin II and transforming growth factor beta on feline kidney epithelial cells

Objectives

The aim of this study was to evaluate the role of angiotensin II (AT-II) and its main mediator, transforming growth factor beta 1 (TGF-β1), in the development of feline renal fibrosis.

Methods

Expression of marker genes indicating epithelial-to-mesenchymal transition (EMT), profibrotic mediators and matricellular proteins was measured in feline kidney epithelial cells (Crandell Rees feline kidney [CRFK] cells) after incubation with AT-II and/or TGF-β1.

Results

Cells incubated with TGF-β1 or the combination of TGF-β1 with AT-II showed clear EMT with more stretched fibroblastic cells, whereas the cells incubated without TGF-β1 and AT-II (control) showed more epithelial cells. Gene expression of collagen type I (COL1), tenascin-C (TNC), trombospondin-1 (TSP-1), connective tissue growth factor (CTGF) and alpha-smooth muscle actin (α-SMA) increased significantly after incubation of the CRFK cells with TGF-β1 or TGF-β1 in combination with AT-II for 12 h. As incubation of the CRFK cells with only AT-II did not show any significant rise in gene expression of the above-mentioned genes, this was further investigated. In contrast to healthy feline kidney tissue, CRFK cells showed almost no expression of the AT-II type 1 (AT₁) receptor.

Conclusions and relevance

TGF-β1 significantly induced expression of the EMT marker gene α-SMA, profibrotic mediator CTGF, and fibrogenic proteins COL1, TNC and TSP-1 in CRFK cells. The effect of TGF-β1 on myofibroblast formation was also observed by the stretched appearance of the CRFK cells. As CRFK cells expressed almost no AT₁ receptors, this cell line proved not suitable for testing the efficacy of drugs that interact with the AT₁ receptor. As AT-II stimulates the effects of TGF-β1 in mammals, the results of this study suggest an indirect profibrotic effect of AT-II besides the demonstrated profibrotic effect of TGF-β1 and thus the development of feline renal fibrosis. Modulation of EMT or proliferation of myofibroblasts could serve as a diagnostic tool and a novel therapeutic target to inhibit renal fibrogenesis, and could possibly serve in the therapy of feline renal fibrosis.

Pilot study to evaluate the potential use of the renal resistive index as a preliminary diagnostic tool for chronic kidney disease in cats

Objectives Chronic kidney disease (CKD) is the most common renal pathology diagnosed in geriatric cats, and its prevalence increases with age. The arterial resistive index (RI) is important when evaluating vascular resistance and compliance, and can be applied in the kidney (renal RI [RRI]), allowing the evaluation of its vascular haemodynamics. The present study aimed to: (1) investigate in cats with CKD the relationships between the RRI and the following parameters: age, sex, body weight, plasmatic creatinine, blood urea nitrogen, potassium, urine specific gravity, urine protein:creatinine ratio and systolic arterial pressure; and (2) evaluate the potential use of the RRI as a preliminary diagnostic tool in cats with CKD. Methods The present study involved 24 cats of both sexes. Six were healthy cats (control group [CG]) and 18 had CKD, but did not have any concomitant diseases and were not being treated with any medications (study group [SG]). For RRI measurement we used colour Doppler ultrasound (CDUS). Results RRI differed significantly between the CG and SG ( P <0.01) and was higher in the SG. A statistically significant correlation was only achieved between the RRI and the body weight of the patients and it was negative. A strong and positive correlation was noted between the mean RRI of both kidneys (r = 0.66). Receiver-operating curve analysis allowed us to establish an admissible cut-off for the RRI value of 0.639 for a preliminary diagnosis of CKD for both kidneys. Conclusions and relevance No differences were found for the RRI between the left and right kidneys, suggesting that evaluation of only one kidney is sufficient to provide an estimate of the RRI value for both organs. RRI measurement, which can be achieved with CDUS, is an easy-to-use diagnostic tool that, with a cut-off value of 0.639 for both kidneys, is useful in establishing a preliminary diagnosis of CKD.

Prognostic importance of plasma total magnesium in a cohort of cats with azotemic chronic kidney disease

Background

Hypomagnesemia is associated with increased mortality and renal function decline in humans with chronic kidney disease (CKD). Magnesium is furthermore inversely associated with fibroblast growth factor 23 (FGF23), an important prognostic factor in CKD in cats. However, the prognostic significance of plasma magnesium in cats with CKD is unknown.

Objectives

To explore associations of plasma total magnesium concentration (tMg) with plasma FGF23 concentration, all‐cause mortality, and disease progression in cats with azotemic CKD.

Animals

Records of 174 client‐owned cats with IRIS stage 2‐4 CKD.

Methods

Cohort study. Cats with azotemic CKD were identified from the records of two London‐based first opinion practices (1999–2013). Possible associations of baseline plasma tMg with FGF23 concentration and risks of death and progression were explored using, respectively, linear, Cox, and logistic regression.

Results

Plasma tMg (reference interval, 1.73–2.57 mg/dL) was inversely associated with plasma FGF23 when controlling for plasma creatinine and phosphate concentrations (partial correlation coefficient, −0.50; P < .001). Hypomagnesemia was observed in 12% (20/174) of cats, and independently associated with increased risk of death (adjusted hazard ratio, 2.74; 95% confidence interval [CI], 1.35–5.55; P = .005). The unadjusted associations of hypermagnesemia (prevalence, 6%; 11/174 cats) with survival (hazard ratio, 2.88; 95% CI, 1.54–5.38; P = .001), and hypomagnesemia with progressive CKD (odds ratio, 17.7; 95% CI, 2.04–154; P = .009) lost significance in multivariable analysis.

Conclusions and Clinical Importance

Hypomagnesemia was associated with higher plasma FGF23 concentrations and increased risk of death. Measurement of plasma tMg augments prognostic information in cats with CKD, but whether these observations are associations or causations warrants further investigation.

[Screening active ingredients of Shenkangwan that regulate endothelial-mesenchymal transition of endothelial cells in vitro]

OBJECTIVE

To screen the effective components of Shenkangwan that regulate endothelial-mesenchymal transition in endothelial cells for optimizing prescription of Shenkangwan.

METHODS

ALK5 was identified as one of the target receptors that regulate endothelial-mesenchymal transition of endothelial cells using molecular docking technique. Nine molecules were screened as the candidate effective components in Shenkangwan, among which calycosin, ononin and stigmasterol were selected for testing. Glomerular epithelial cells were exposed to high glucose and treated with calycosin, ononin, or stigmasterol, and the cellular expressions of α-smooth muscle actin (α-SMA) and vimentin mRNA were detected with real-time fluorescence quantitative PCR. The phosphorylation of SMAD2/3 in the cells was detected using Western blotting.

RESULTS

Calycosin, ononin and stigmasterol did not produce significant cytotoxicity in glomerular epithelial cells (P>0.05). The cells exposed to high glucose and calycosin treatment showed significantly decreased mRNA levels of α-SMA and vimentin (P<0.05) and inhibited phosphorylation of SMAD2/3. Ononin and stigmasterol did not produce such effects in the cells.

CONCLUSION

In endothelial cells with high glucose-induced injury, calycosin can inhibit the up-regulation of α-SMA and vimentin and inhibit phosphorylation of SMAD2/3 to regulate endothelial-mesenchymal transition and improve diabetic nephropathy.

Mineral analysis of complete dog and cat foods in the UK and compliance with European guidelines

Mineral content of complete pet food is regulated to ensure health of the companion animal population. Analysis of adherence to these regulatory guidelines has not been conducted. Here, mineral composition of complete wet (n = 97) and dry (n = 80) canine and feline pet food sold in the UK was measured to assess compliance with EU guidelines. A majority of foods complied with ≥8 of 11 guidelines (99% and 83% for dry and wet food, respectively), but many failed to provide nutritional minimum (e.g. Cu, 20% of wet food) or exceeded nutritional maximum (e.g. Se, 76% of wet food). Only 6% (6/97) of wet and 38% (30/80) of dry food were fully compliant. Some foods (20–30% of all analysed) had mineral imbalance, such as not having the recommended ratio of Ca:P (between 1:1 to 2:1). Foods with high fish content had high levels of undesirable metal elements such as arsenic. This study highlights broad non-compliance of a range of popular pet foods sold in the UK with EU guidelines (94% and 61% of wet and dry foods, respectively). If fed exclusively and over an extended period, a number of these pet foods could impact the general health of companion animals.

A Double-blind, Placebo-controlled, Multicenter, Prospective, Randomized Study of Beraprost Sodium Treatment for Cats with Chronic Kidney Disease

Background

Chronic kidney disease (CKD) is a common progressive and irreversible disease in cats. The efficacy and safety of beraprost sodium (BPS) in cats with CKD have not been evaluated.

Hypothesis/Objectives

To evaluate the efficacy and safety of BPS in the treatment of cats with CKD, as compared to placebo.

Animals

Seventy‐four client‐owned cats with naturally occurring CKD.

Methods

Double‐blind, placebo‐controlled, multicenter, prospective, randomized trial. The cats received BPS (55 μg/cat) or a placebo PO q12 h for 180 days. The primary endpoint was prospectively defined as a change in the serum creatinine (sCr), serum phosphorus‐to‐calcium ratio or urine specific gravity (USG).

Results

The sCr increased significantly (P = 0.0030) in the placebo group (mean ± SD: 2.8 ± 0.7 to 3.2 ± 1.3 mg/dL) but not in the BPS group (2.4 ± 0.7 to 2.5 ± 0.7 mg/dL). The difference between the groups at day 180 was significant (0.8 mg/dL, 95% CI: 0.2 to 1.3 mg/dL, P = 0.0071). The serum phosphorus‐to‐calcium ratio was significantly (P = 0.0037) increased in the placebo group (0.46 ± 0.10 to 0.52 ± 0.21 mg/dL) but not in the BPS group (0.50 ± 0.08 to 0.51 ± 0.11 mg/dL). There was no significant change in the USG in either group. An adverse event judged as being treatment‐related included vomiting that occurred in 1 case in the placebo group. No clinically relevant change was observed in the CBC and other blood chemistry tests.

Conclusions and Clinical Importance

Beraprost sodium treatment was well tolerated and safe in cats with CKD. BPS inhibited the reduction in renal filtration function as measured by sCr increase.

Red meat intake in chronic kidney disease patients: Two sides of the coin

Red meat is an important dietary source of high biological value protein and micronutrients such as vitamins, iron, and zinc that exert many beneficial functions. However, high consumption of animal protein sources, especially red meat, results in an increased intake of saturated fat, cholesterol, iron, and salt, as well as an excessive acid load. Red meat intake may lead to an elevated production of uremic toxins by the gut microbiota, such as trimethylamine n-oxide (TMAO), indoxyl sulfate, and p-cresyl sulfate. These uremic toxins are associated with increased risk for cardiovascular (CV) mortality. Limiting the intake of red meat in patients with chronic kidney disease (CKD) thus may be a good strategy to reduce CV risk, and may slow the progression of kidney disease. In the present review, we discuss the role of red meat in the diet of patients with CKD. Additionally, we report on a pilot study that focused on the effect of a low-protein diet on TMAO plasma levels in nondialysis CKD patients.

Disease-syndrome combination modeling: metabolomic strategy for the pathogenesis of chronic kidney disease

Conventional disease animal models have limitations on the conformity to the actual clinical situation. Disease-syndrome combination (DS) modeling may provide a more efficient strategy for biomedicine research. Disease model and DS model of renal fibrosis in chronic kidney disease were established by ligating the left ureter and by ligating unilateral ureteral combined with exhaustive swimming, respectively. Serum metabolomics was conducted to evaluate disease model and DS model by using ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Potential endogenous biomarkers were identified by multivariate statistical analysis. There are no differences between two models regarding their clinical biochemistry and kidney histopathology, while metabolomics highlights their difference. It is found that abnormal sphingolipid metabolism is a common characteristic of both models, while arachidonic acid metabolism, linolenic acid metabolism and glycerophospholipid metabolism are highlighted in DS model. Metabolomics is a promising approach to evaluate experiment animal models. DS model are comparatively in more coincidence with clinical settings, and is superior to single disease model for the biomedicine research.

Controversies in Veterinary Nephrology: Renal Diets Are Indicated for Cats with International Renal Interest Society Chronic Kidney Disease Stages 2 to 4: The Con View

Renal diets typically incorporate protein and phosphorus restriction, supplement with potassium and Omega-3 fatty acids, and address metabolic acidosis. Compared to "maintenance" diets, these modifications appear to benefit cats with chronic kidney disease (CKD). However, there is limited data in cats justifying the specific amounts of the nutrients used in these diets, and there is little evidence supporting protein restriction in cats with CKD. Energy intake, maintenance of body weight, and muscle and body condition need to be addressed, and may take precedence over special diets. Further research is needed to better define optimum diets for cats with CKD.

Thymoquinone protects the rat kidneys against renal fibrosis

Thymoquinone (TQ) is the main active ingredient of Nigella sativa seeds with various pharmacological effects. The aim of this study was to investigate the effect of TQ on renal fibrosis and permeability and oxidative stress status in lipopolysaccharide (LPS)-induced inflammation in male rats. Eighty male Wistar rats were divided into 5 groups as follow: control (received normal saline), LPS (1 mg/kg/day), and LPS+TQ (by doses of 2, 5 and 10 mg/kg/day). After three weeks, the biochemical parameters such as blood urea nitrogen (BUN) and creatinine in serum samples, oxidative stress markers including malondialdehyde (MDA), total thiol groups, superoxide dismutase (SOD) and catalase (CAT) activities in renal tissue homogenate and renal permeability (evaluated by Evan’s blue dye method) were measured and renal fibrosis was evaluated, histologically using Masson’s trichrome staining. LPS administration induced renal fibrosis (1.49 ± 0.08 vs. 7.15 ± 0.18%) and significantly increased renal permeability (6.03 ± 1.05 vs. 13.5 ± 1.04 μg evans blue(EB)/g tissue), serum BUN and creatinine levels and oxidative stress marker (MDA) (P < 0.05), while, it reduced anti-oxidative markers including total thiol group, SOD and CAT activities (P < 0.05). Administration of TQ significantly improved these alterations which were dose-dependent in oxidative stress markers, renal permeability (TQ 2, 5 and 10 mg/kg: 10.7 ± 0.3, 9.2 ± 1.4 and 11.5 ± 0.6 μg EB/g tissue; respectively) and fibrosis (TQ 2, 5 and 10 mg/kg: 6.09 ± 0.7, 4.26 ± 0.14 and 2.52 ± 0.08%; respectively). In conclusion, administration of TQ reduced renal fibrosis and permeability and improved oxidative stress status. Thus, TQ can be considered in conditions accompanied with chronic inflammation at least as a part of treatment strategy.

Numb Protects Human Renal Tubular Epithelial Cells From Bovine Serum Albumin-Induced Apoptosis Through Antagonizing CHOP/PERK Pathway

In recent studies, we found that Numb is involved in oxidative stress-induced apoptosis of renal proximal tubular cells; however, its function on ER stress-induced apoptosis in proteinuric kidney disease remains unknown. The objective of the present study is to explore the role of Numb in urinary albumin-induced apoptosis of human renal tubular epithelial cells (HKCs). In this study, we demonstrate that incubation of HKCs with bovine serum albumin (BSA) resulted in caspase three-dependent cell death. Numb expression was down-regulated by BSA in a time- and dose-dependent manner. Knockdown of Numb by siRNA sensitized HKCs to BSA-induced apoptosis, whereas overexpression of Numb protected HKCs from BSA-induced apoptosis. Moreover, BSA activated CHOP/PERK signaling pathway in a time- and dose-dependent manner as indicated by increased expression of CHOP, PERK, and P-PERK. Furthermore, knockdown of CHOP or PERK significantly attenuated the promoting effect of Numb on BSA-induced apoptosis, while overexpression of CHOP impaired the protective effect of Numb on BSA-induced apoptosis. Taken together, our findings demonstrate that Numb plays a protective role on BSA-induced apoptosis through inhibiting CHOP/PERK signaling pathway in human renal tubular epithelial cells. Therefore, the results from this study provides evidence that Numb is a new target of ER-associated apoptotic signaling networks and Numb may serve as a promising therapeutic target for proteinuric diseases.

Elucidation of the therapeutic role of mitochondrial biogenesis transducers NRF-1 in the regulation of renal fibrosis

BACKGROUND

Mitochondrial dysfunction is a newly established risk factor for the development of renal fibrosis. Cell survival and injury repair is facilitated by mitochondrial biogenesis. Nuclear respiratory factor 1 (NRF-1) is a transcriptional regulation factor that plays a central role in the regulation of mitochondrial biogenesis. However, the transcription factor of this process in renal fibrosis is unknown. Thus, we hereby discussed the correlations of NRF-1 and renal interstitial fibrosis.

MATERIALS AND METHODS

In vitro fibrosis model was established by treatment with transforming growth factor-β1 (TGF-β1) in NRK-49F (Normal Rat kidney fibroblast). We investigated the ROS production, mitochondrial biogenesis and fibrogenic marker (e.q. fibronectin) during the progression of renal fibrosis by kit and Western blotting assay. Here, we used that two distinct mechanisms regulate NRF-1 activation and degradation of NRF-1. NRF-1 was transfect by pcDNA-NRF-1 overexpression gene to evaluate the NRF-1 activity of the therapeutic effect in renal fibrosis. In addition, NRF-1 was silenced by shRNA-NRF-1 to evaluate the significance of NRF-1. ELISA was used to evaluate the secreted fibronectin. Immunofluorescence staining was used to assay the in situ expression of proteins (e.g. fibronectin, NRF-1).

RESULTS

Under renal fibrosis conditions, TGF-β1 (5ng/ml) increased ROS. Simultaneously, TGF-β1-induced extracellular fibronectin by ELISA assay. In addition, TGF-β1 decreased expression of mitochondrial biogenesis. This is the first time to demonstrate that expression of NRF-1 is significantly decreased in renal fibrosis. However, NRK49F was a transfection with pcDNA-NRF-1 (2μg/ml) expression vector dramatically reverse TGF-β1-induced cellular fibrosis concomitantly with the suppression of fibronectin (both intracellular and extracellular fibronectin). More importantly, transfection with shRNA-NRF-1 (2μg/ml) significantly increased the expression of fibronectin of both intercellular and extracellular origins in NRK-49F cells.

DISCUSSION

These finding suggest that NRF-1 plays a pivotal role on renal cellular fibrosis. Moreover, NRF-1 might act as a novel renal fibrosis antagonist by down-regulating fibrosis signaling in renal fibroblast cells.

Treatment with cytokine thymic stromal lymphopoietin short hairpin RNA substantially reduces TGF-β1-induced interstitial cellular fibrosis

Thymic stromal lymphopoietin (TSLP) has previously been linked to allergic inflammatory diseases, and tissue fibrosis and organ dysfunction may also arise from such inflammation. It remains unclear, however, whether TSLP plays any role in the occurrence of renal fibrosis, so this study investigated that possibility. An in vitro fibrosis model was established by treating normal rat kidney fibroblast (NRK-49F) cells with transforming growth factor-β1 (TGF-β1), after which the levels of various fibrogenic markers (e.g., fibronectin) and downstream fibrogenic signal proteins (e.g., smad 7) were investigated. Also, TSLP shRNA was used to silence the effects of TSLP, while an ELISA was conducted to evaluate the fibronectin secretions. The level of fibronectin in the NRK-49F cells was dose- and time-dependently increased by the administration of exogenous TSLP (P<0.05). TSLP also significantly increased the level of fibrosis signaling, in addition to inducing a marked decrease in the down-regulation of Smad7. Interestingly, the application of TSLP shRNA caused a stark reversal of the TGF-β1-induced cellular fibrosis while simultaneously leading to the suppression of fibronectin and fibrogenic signal proteins. Taken together, these observations provide insights into how extracellular matrices develop and could thus lead to potential therapeutic interventions for the suppression of renal fibrosis.

Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses

Chronic kidney disease (CKD) is the most common metabolic disease of domesticated cats, with most affected cats being geriatric (>12 years of age). The prevalence of CKD in cats exceeds that observed in dogs, and the frequency of the diagnosis of CKD in cats has increased in recent decades. Typical histologic features include interstitial inflammation, tubular atrophy, and fibrosis with secondary glomerulosclerosis. In contrast to people and dogs, primary glomerulopathies with marked proteinuria are remarkably rare findings in cats. Although a variety of primary renal diseases have been implicated, the disease is idiopathic in most cats. Tubulointerstitial changes, including fibrosis, are present in the early stages of feline CKD and become more severe in advanced disease. A variety of factors-including aging, ischemia, comorbid conditions, phosphorus overload, and routine vaccinations-have been implicated as factors that could contribute to the initiation of this disease in affected cats. Factors that are related to progression of established CKD, which occurs in some but not all cats, include dietary phosphorus intake, magnitude of proteinuria, and anemia. Renal fibrosis, a common histologic feature of aged feline kidneys, interferes with the normal relationship between peritubular capillaries and renal tubules. Experimentally, renal ischemia results in morphologic changes similar to those observed in spontaneous CKD. Renal hypoxia, perhaps episodic, may play a role in the initiation and progression of this disease.

Cobrotoxin from Naja naja atra Venom Ameliorates Adriamycin Nephropathy in Rats

Chronic kidney disease (CKD) becomes a global health problem with high morbidity and mortality. Adriamycin- (ADR-) induced rodent chronic nephropathy is a classic experimental model of human minimal lesion nephrotic syndrome. The present study investigated the effect of cobrotoxin (CTX) on ADR-induced nephropathy. Rats were given 6 mg/kg ADR once through the tail vein to replicate ADR nephropathy model. CTX was administered to rats daily by placing a fast dissolving CTX membrane strip under the tongue starting from 5 days prior to ADR administration until the end of experiment. The results showed that CTX ameliorated the symptoms of ADR nephropathy syndrome with reduced body weight loss, proteinuria, hypoalbuminemia, dyslipidemia, serum electrolyte imbalance, oxidative stress, renal function abnormities, and kidney pathological lesions. Anti-inflammatory cytokine IL-10 expression was elevated after CTX administration in ADR nephropathy model. CTX inhibited the phosphorylation of IκB-α and NF-κB p65 nuclear translocation. Meanwhile, CTX upregulated the protein level of podocyte-specific nephrin and downregulated the level of fibrosis-related TGF-β. These findings suggest that CTX may be a potential drug for chronic kidney diseases.