Urinary active transforming growth factor β in feline chronic kidney disease

Hemogram-Derived Inflammatory Markers in Cats with Chronic Kidney Disease

Chronic kidney disease (CKD) is characterized by chronic inflammation, which mediates the progressive replacement of functional nephrons by fibrotic tissue. Hemogram-derived inflammatory markers are known to serve as markers of pathological conditions; however, their diagnostic value in feline CKD is still unknown. The aim of this retrospective study was to investigate selected hemogram-derived inflammatory markers (neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR) and the systemic immune-inflammatory index (SII)) in cats at different clinical stages of CKD. Eighty-eight client-owned cats with CKD and thirty-two healthy control cats were included. Cats with CKD were divided into two groups: early CKD (IRIS stage 1 and 2; 62 cats) and progressed CKD (IRIS stage 3 and 4; 26 cats). The values of inflammatory markers were compared between the two CKD groups and the control group. All investigated hemogram-derived inflammatory markers were significantly (p < 0.05) greater in cats with advanced CKD than in those in the other two groups. Additionally, we demonstrated a statistically significant weak to moderate correlation between serum urea, creatinine, selected hematologic and urinary parameters, and the investigated inflammatory markers in cats with CKD. Chronic inflammation can be easily and inexpensively assessed with hemogram-derived markers.

Decreased circulating transforming growth factor-beta (TGF-β) and kidney TGF-β immunoreactivity predict renal disease in cats with naturally occurring chronic kidney disease

OBJECTIVES

The aim of the present study was to compare the circulating transforming growth factor-beta (TGF-β) of clinically normal age-matched and naturally occurring chronic kidney disease (CKD) cats and to determine the correlation between the TGF-β expression and histopathological changes in cats with CKD.

METHODS

A total of 11 clinically normal age-matched and 27 cats with naturally occurring CKD were included in this study. Circulating TGF-β was quantified by immunoassays. Kaplan-Meier analysis was used to calculate the association between survival time and the concentration of circulating TGF-β. A general linear model was used to compare the circulating TGF-β between groups. Immunohistochemical analyses revealed TGF-β expression in renal tissues from cats with CKD that died during the study (n = 7) and in available archived renal tissue specimens taken at necropsy from cats that had previous CKD with renal lesions (n = 10). Correlations of the TGF-β expression and clinical parameters (n = 7) and histopathological changes (n = 17) were analysed using Spearman's rank correlation.

RESULTS

The median survival time of cats with a lower concentration of circulating TGF-β was shorter than that of cats with a higher concentration. The area under the curve of circulating TGF-β for predicting CKD was 0.781, indicating good differentiation. The study indicated a significant difference in circulating TGF-β concentrations between clinically normal cats and those with CKD and demonstrated that TGF-β expression is correlated with tubular atrophy.

CONCLUSIONS AND RELEVANCE

The study findings suggest that decreased serum TGF-β and tubular atrophy with TGF-β immunoreactivity may be significant in cats with CKD.

Cytokines' Role in the Pathogenesis and Their Targeting for the Prevention of Frozen Shoulder: A Narrative Review

Frozen shoulder (FS) is a common name for shoulder movement limitation with different degrees of shoulder rigidity and pain. It is characterized by varying developmental courses, different levels of shoulder movement limitation, and background ambiguity due to the multiplicity of its causative factors. Systemic inflammatory cytokines monitoring and restraining is easy to apply, fast to conduct, and needs lower costs compared to invasive methods for frozen shoulder stage evaluation and early controlling of its progress to the stage that necessitates surgical intervention. The aim of this review was to assess the recent findings concerning the role of cytokines in FS pathogenesis and the possibility of preventing or controlling their progress through targeting these cytokines by the new drugs candidates, such as hyaluronan (HA), botulinum toxin type A (BoNT A), Tetrandrine, tumor necrosis factor-stimulated gene-6 (TSG-6), and cannabidiol. Searching the PubMed site, we encountered out of 1608 records, from which 16 original studies were included for the quantitative construction of this systematic review screening of the recent studies to investigate the different FS pathogenic pathways. Most of the scenarios are centered around the inflammatory and fibrotic process triggered by synovial and capsular fibroblast stimulation. This mechanism depends mainly on alarmins cytokines, including thymic stromal lymphopoietin (TSLP), interleukin-33 (IL-33), and interleukin-25 (IL-25), with the stimulation of interleukin-1 α (IL-1α), interleukin-1 β (IL-1β), tumor necrosis alpha (TNF-α), cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in a joint capsule. Different pathways of transforming growth factor- β (TGF-β) stimulation, resulting in overexpression of the fibrotic factors as tenascin C (TNC), fibronectin 1, collagen I (COL 1) and collagen III (COL III), and matrix metalloproteinases (MMPs) in the capsular or synovial/capsular fibroblasts. The overall investigation of these studies led us to conclude that the new drug candidates proved their efficiency in controlling the common pathogenesis of the inflammatory and fibrotic pathways of frozen shoulder and therefore represent a prospect for easy and early controlling and efficiently treating this serious disease.

Glutathione prevents high glucose-induced pancreatic fibrosis by suppressing pancreatic stellate cell activation via the ROS/TGFβ/SMAD pathway

The activation of pancreatic stellate cells (PSCs) is the key mechanism of pancreatic fibrosis, which can lead to β-cell failure. Oxidative stress is an important risk factor for PSC activation. There is no direct evidence proving if administration of glutathione can inhibit fibrosis and β-cell failure. To explore the role of glutathione in pancreatic fibrosis and β-cell failure induced by hyperglycaemia, we established a rat model of pancreatic fibrosis and β-cell failure. The model was founded through long-term oscillating glucose (LOsG) intake and the setup of a sham group and a glutathione intervention group. In vitro, rat PSCs were treated with low glucose, high glucose, or high glucose plus glutathione to explore the mechanism of high glucose-induced PSC activation and the downstream effects of glutathione. Compared with sham rats, LOsG-treated rats had higher reactive oxygen species (ROS) levels in peripheral leukocytes and pancreatic tissue while TGFβ signalling was upregulated. In addition, as the number of PSCs and pancreatic fibrosis increased, β-cell function was significantly impaired. Glutathione evidently inhibited the upregulation of TGFβ signalling and several unfavourable outcomes caused by LOsG. In vitro treatment of high glucose for 72 h resulted in higher ROS accumulation and potentiated TGFβ pathway activation in PSCs. PSCs showed myofibroblast phenotype transformation with upregulation of α-SMA expression and increased cell proliferation and migration. Treatment with either glutathione or TGFβ pathway inhibitors alleviated these changes. Together, our findings suggest that glutathione can inhibit PSC activation-induced pancreatic fibrosis via blocking ROS/TGFβ/SMAD signalling in vivo and in vitro.

TGF-β/Smad Signaling Pathway in Tubulointerstitial Fibrosis

Chronic kidney disease (CKD) was a major public health problem worldwide. Renal fibrosis, especially tubulointerstitial fibrosis, is final manifestation of CKD. Many studies have demonstrated that TGF-β/Smad signaling pathway plays a crucial role in renal fibrosis. Therefore, targeted inhibition of TGF-β/Smad signaling pathway can be used as a potential therapeutic measure for tubulointerstitial fibrosis. At present, a variety of targeting TGF-β1 and its downstream Smad proteins have attracted attention. Natural products used as potential therapeutic strategies for tubulointerstitial fibrosis have the characteristics of acting on multiple targets by multiple components and few side effects. With the continuous research and technique development, more and more molecular mechanisms of natural products have been revealed, and there are many natural products that inhibited tubulointerstitial fibrosis via TGF-β/Smad signaling pathway. This review summarized the role of TGF-β/Smad signaling pathway in tubulointerstitial fibrosis and natural products against tubulointerstitial fibrosis by targeting TGF-β/Smad signaling pathway. Additionally, many challenges and opportunities are presented for inhibiting renal fibrosis in the future.

MicroRNAs are differentially expressed in the serum and renal tissues of cats with experimentally induced chronic kidney disease: a preliminary study

OBJECTIVE

To identify differentially expressed microRNA in the serum and renal tissues of cats with experimentally induced chronic kidney disease (CKD).

SAMPLE

Banked renal tissues and serum from 4 cats.

PROCEDURES

Cats previously underwent 90-minute unilateral ischemia with delayed contralateral nephrectomy 3 months after ischemia. Tissues were collected from the contralateral kidney at the time of nephrectomy and from the ischemic kidney 6 months after nephrectomy (study end). Serum was collected prior to ischemia (baseline serum) and at study end (end point serum). Total RNA was isolated from tissues and serum, and microRNA sequencing was performed with differential expression analysis between the contralateral and ischemic kidney and baseline and end point serum.

RESULTS

20 microRNAs were differentially expressed between ischemic and contralateral kidneys, and 52 microRNAs were differentially expressed between end point and baseline serum. Five microRNAs were mutually differentially expressed between ischemic and contralateral kidneys and baseline and end point serum, with 4 (mir-21, mir-146, mir-199, and mir-235) having increased expression in both the ischemic kidney and end point serum and 1 (mir-382) having increased expression in the ischemic kidney and decreased expression in end point serum. Predicted target search for these microRNA revealed multiple genes previously shown to be involved in the pathogenesis of feline CKD, including hypoxia-inducible factor-1α, transforming growth factor-β, hepatocyte growth factor, fibronectin, and vascular endothelial growth factor A.

CLINICAL RELEVANCE

MicroRNAs were differentially expressed after CKD induction in this preliminary study. Regulation of renal fibrosis in feline CKD may occur through microRNA regulation of mRNAs of pro- and anti-fibrotic genes.

Immunohistochemical Expression of TGF-β1 in Kidneys of Cats with Chronic Kidney Disease

Transforming growth factor-beta 1 (TGF-β1) plays a central role in the progression of chronic kidney disease (CKD). However, in feline CKD, renal expression of TGF-β1 and how it changes as the disease progresses have not been fully studied. In the present study, we immunohistochemically assessed the renal expression levels of TGF-β1 in cats with CKD and statistically analyzed its correlation with CKD severity. Clear immunosignals were detected in the glomerular mesangial cells, Bowman’s capsules, proximal tubules, distal nephrons, platelets, and vascular smooth muscles in the kidneys of cats with CKD. Statistically, luminal signals in the distal nephrons showed positive correlations with plasma creatinine levels and glomerulosclerosis, while those in the proximal tubules and platelets showed negative correlations with plasma urea and/or creatinine levels. Therefore, it was suggested that the changes in the renal expression of TGF-β1 could be associated with progression of feline CKD.

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.

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.

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.

Preliminary study of urinary excretion of liver-type fatty acid-binding protein in a cat model of chronic kidney disease

Urinary liver-type fatty acid-binding protein (uL-FABP) is a clinically useful biomarker for monitoring chronic kidney disease (CKD) in humans. However, long-term monitoring of uL-FABP in CKD cats has not been reported. The objective of this preliminary study was to investigate whether the urinary excretion of L-FABP could predict the deterioration of renal function in 2 CKD model cats. Urinary liver-type fatty acid-binding protein (uL-FABP) increased before standard renal biomarkers, including serum creatinine, blood urea nitrogen, and symmetric dimethylarginine, in 1 cat with deteriorating renal function, but remained low and relatively stable in another cat with stable renal function. Our results suggest that uL-FABP is a potential clinical biomarker for predicting the progression of CKD in cats, as it is in humans.

Kidney function and glucose metabolism in overweight and obese cats

Background: In people, obesity and prediabetes mellitus might predispose to chronic kidney disease (CKD).Aims: To assess the association of overweight [Body condition score (BCS) >5] and glucose metabolism alterations, with established or potential markers of CKD. In addition, fructosamine and fasted blood glucose were compared as predictors of early abnormal glucose metabolism.Methods: 54 clinically healthy cats were included in a cross-sectional study comprising 25 neutered males and 29 (28 neutered) females aged 7.2 (5.5-9.4) years. Two potential markers of CKD, namely urinary free active transforming growth factor-β1-creatinine ratio and urinary retinol binding protein-creatinine ratio were measured along with other parameters to assess CKD. A receiver operating curve was used to identify the best sensitivity and specificity of fructosamine to identify cats with fasting glucose >6.5 mmol/L.Results: No association was found between BCS and markers of CKD. Fructosamine was greater in cats with fasting glucose >6.5 mmol/L compared to those with fasting glucose ≤6.5 mmol/L. A fructosamine concentration ≥250 µmol/L was able to detect cats with hyperglycemia with a sensitivity of 77% and a specificity of 65%. Furthermore, fructosamine was more strongly correlated with fasting glucose than albumin-corrected fructosamine (r = 0.43, p = 0.002 vs r = 0.32, p = 0.026). Cats with higher fructosamine had lower serum symmetric dimethylarginine concentrations.Conclusion: The present study does not suggest an effect of obesity on renal function in domestic cats.Clinical relevance: Fructosamine might be of value for the diagnosis of prediabetes mellitus in cats.

Effects of low-dose meloxicam in cats with chronic kidney disease

OBJECTIVES

Meloxicam therapy may benefit cats with degenerative joint disease, and retrospective studies suggest it could slow kidney disease progression and increase survival. This study aimed to prospectively evaluate the renal effects of low-dose meloxicam treatment (0.02 mg/kg/day) over 6 months in cats with chronic kidney disease (CKD).

METHODS

Twenty-one cats with stable International Renal Interest Society stage 2 or 3 CKD were recruited and randomized to placebo or meloxicam groups. Cats were evaluated at baseline and at 1, 3 and 6 months, including blood pressure, chemistry, symmetric dimethylarginine (SDMA), glomerular filtration rate (GFR), urinalysis, urine protein:creatinine ratio (UPC), urine transforming growth factor-beta (β):creatinine ratio, urine clusterin, urine cystatin B and serum inosine.

RESULTS

No statistical difference was observed in systolic blood pressure, blood urea nitrogen, creatinine, SDMA, GFR, urine transforming growth factor-β:creatinine ratio, urine clusterin, urine cystatin B or serum inosine in cats receiving meloxicam vs placebo. Mean UPC was greater in the meloxicam group (0.33) than the placebo group (0.1) at 6 months (P = 0.006). Four cats had meloxicam discontinued owing to potential (mainly gastrointestinal) adverse effects.

CONCLUSIONS AND RELEVANCE

No decline in renal excretory function was observed when meloxicam was administered to cats with CKD. However, gastrointestinal adverse effects were observed, and cats that received meloxicam had greater proteinuria at 6 months than cats that received placebo. As proteinuria is associated with negative outcomes (progression of azotemia and hypertension) in cats with CKD, this finding suggests that meloxicam should be used with caution in cats with CKD and UPC monitored. Until further research is available, clinicians should weigh the risk of potential increased proteinuria against quality of life benefits when considering meloxicam for analgesia in cats with renal disease.

Investigation of the transforming growth factor-beta 1 signalling pathway as a possible link between hyperphosphataemia and renal fibrosis in feline chronic kidney disease

•

Chronic kidney disease (CKD) is associated with development of hyperphosphataemia.

•

Severity of renal fibrosis has been correlated with degree of hyperphosphataemia.

•

Transforming growth factor-β1 (TGF-β1) is a major pro-fibrotic mediator in CKD.

•

A phosphate restricted diet did not affect urinary active TGF-β1 excretion in cats.

•

Increased extracellular phosphate had no pro-fibrotic effect on feline renal cells.

Chronic kidney disease (CKD) is common in geriatric cats, and is characterised in the majority of cases by tubulointerstitial inflammation and fibrosis. Hyperphosphataemia is a frequent complication of CKD and is independently associated with severity of renal fibrosis and disease progression. Transforming growth factor-beta 1 (TGF-β1) signalling is thought to be a convergent pathway which mediates the progression of renal fibrosis in CKD. The aims of this study were to explore the interaction between increased extracellular phosphate and the TGF-β1 signalling pathway by investigating: (a) the effect of a commercially available, phosphate-restricted, diet on urinary TGF-β1 excretion in cats with CKD; and (b) the role of increased extracellular phosphate in regulating proliferation, apoptosis, and expression of genes related to TGF-β1 signalling and extracellular matrix (ECM) production in feline proximal tubular epithelial cells (FPTEC) and cortical fibroblasts from cats with azotaemic CKD (CKD-FCF).

The dietary intervention study revealed no effect of dietary phosphate restriction on urinary active TGF-β1 excretion after 4–8 weeks (P = 0.98), despite significantly decreasing serum phosphate (P < 0.001). There was no effect of increased growth media phosphate concentration (from 0.95 mM to 2 mM and 3.5 mM) on proliferation (P = 0.99) and apoptotic activity in FPTEC (P = 0.22), or expression of genes related to ECM production and the TGF-β1 signalling pathway in FPTEC and CKD-FCF (P > 0.05). These findings suggest the beneficial effects of dietary phosphate restriction on progression of feline CKD may not occur through modulation of renal TGF-β1 production, and do not support a direct pro-fibrotic effect of increased extracellular phosphate on feline renal cells.

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.

Evaluation of profibrotic gene transcription in renal tissues from cats with naturally occurring chronic kidney disease

BACKGROUND

Increased gene transcription of hypoxia-induced mediators of fibrosis in renal tissue has been identified in experimentally induced, ischemic chronic kidney disease (CKD).

OBJECTIVE

To characterize hypoxia-induced profibrotic pathways in naturally occurring CKD in cats.

ANIMALS

Twelve client-owned cats with CKD and 8 healthy control cats.

METHODS

In this prospective, cross-sectional study, bilateral renal tissue samples were assessed histologically for inflammation, tubular atrophy, and fibrosis, and by reverse transcription-quantitative PCR for characterization of transcript levels of hypoxia-inducible factor-1α (HIF1A), matrix metalloproteinases-2 (MMP2), -7 (MMP7), and -9 (MMP9), tissue inhibitor of metalloproteinase-1 (TIMP1), transforming growth factor-β1 (TGFB1), and vascular endothelial growth factor-A (VEGFA). Linear mixed models were used to compare gene transcription between diseased and healthy kidneys, and to examine the association between transcript levels and serum creatinine concentration for all cats, and between transcript levels and histologic scores of diseased kidneys.

RESULTS

Kidneys from cats with CKD had significantly higher transcript levels of HIF1A, MMP2, MMP7, MMP9, TIMP1, and TGFB1 (all P < .001), and lower levels of VEGFA (P = .006) than those from control cats. Transcript levels of MMP7 (P = .05) and TIMP1 (P = .005) were positively associated with serum creatinine in cats with CKD, but not in control cats. In diseased kidneys, transcript levels of MMP2 (P = .002), MMP7 (P = .02), and TIMP1 (P = .02) were positively, whereas those of VEGFA (P = .003) were negatively, associated with histologic score severity.

CONCLUSION AND CLINICAL SIGNIFICANCE

Evaluation of the expression of the corresponding proteins in larger populations could identify therapeutic targets and/or biomarkers of tubulointerstitial fibrosis in cats.

Animal Models and Renal Biomarkers of Diabetic Nephropathy

Diabetes mellitus (DM) is the first cause of end stage chronic kidney disease (CKD). Animal models of the disease can shed light on the pathogenesis of the diabetic nephropathy (DN) and novel and earlier biomarkers of the condition may help to improve diagnosis and prognosis. This review summarizes the most important features of animal models used in the study of DN and updates the most recent progress in biomarker research.

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.

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.

The cat as a naturally occurring model of renal interstitial fibrosis: Characterisation of primary feline proximal tubular epithelial cells and comparative pro-fibrotic effects of TGF-β1

Chronic kidney disease (CKD) is common in both geriatric cats and aging humans, and is pathologically characterised by chronic tubulointerstitial inflammation and fibrosis in both species. Cats with CKD may represent a spontaneously occurring, non-rodent animal model of human disease, however little is known of feline renal cell biology. In other species, TGF-β1 signalling in the proximal tubular epithelium is thought to play a key role in the initiation and progression of renal fibrosis. In this study, we first aimed to isolate and characterise feline proximal tubular epithelial cells (FPTEC), comparing them to human primary renal epithelial cells (HREC) and the human proximal tubular cell line HK-2. Secondly, we aimed to examine and compare the effect of human recombinant TGF-β1 on cell proliferation, pro-apoptotic signalling and genes associated with epithelial-to-mesenchymal transition (EMT) in feline and human renal epithelial cells. FPTEC were successfully isolated from cadaverous feline renal tissue, and demonstrated a marker protein expression profile identical to that of HREC and HK-2. Exposure to TGF-β1 (0-10 ng/ml) induced a concentration-dependent loss of epithelial morphology and alterations in gene expression consistent with the occurrence of partial EMT in all cell types. This was associated with transcription of downstream pro-fibrotic mediators, growth arrest in FPTEC and HREC (but not HK-2), and increased apoptotic signalling at high concentrations of TGF- β1. These effects were inhibited by the ALK5 (TGF-β1RI) antagonist SB431542 (5 μM), suggesting they are mediated via the ALK5/TGF-β1RII receptor complex. Taken together, these results suggest that TGF-β1 may be involved in epithelial cell dedifferentiation, growth arrest and apoptosis in feline CKD as in human disease, and that cats may be a useful, naturally occurring model of human CKD.

Characterisation of feline renal cortical fibroblast cultures and their transcriptional response to transforming growth factor β1

Background

Chronic kidney disease (CKD) is common in geriatric cats, and the most prevalent pathology is chronic tubulointerstitial inflammation and fibrosis. The cell type predominantly responsible for the production of extra-cellular matrix in renal fibrosis is the myofibroblast, and fibroblast to myofibroblast differentiation is probably a crucial event. The cytokine TGF-β1 is reportedly the most important regulator of myofibroblastic differentiation in other species. The aim of this study was to isolate and characterise renal fibroblasts from cadaverous kidney tissue of cats with and without CKD, and to investigate the transcriptional response to TGF-β1.

Results

Cortical fibroblast cultures were successfully established from the kidney tissue of cats with normal kidney function (FCF) and cats with chronic kidney disease (CKD-FCF). Both cell types expressed the mesenchymal markers vimentin, CD44 and CD29, and were negative for the epithelial marker cytokeratin, mesangial cell marker desmin and endothelial cell marker vWF. Only CKD-FCF expressed VCAM-1, a cell marker associated with inflammation. Incubation with TGF-β1 (0–10 ng/ml) induced a concentration dependent change in cell morphology, and upregulation of myofibroblast marker gene α-SMA expression alongside collagen 1α1, fibronectin, TGF-β1 and CTGF mRNA. These changes were blocked by the TGF-β1 receptor 1 antagonist SB431542 (5 μM).

Conclusions

FCF and CKD-FCF can be cultured via a simple method and represent a model for the investigation of the progression of fibrosis in feline CKD. The findings of this study suggest TGF-β1 may be involved in fibroblast-myofibroblast transition in feline CKD, as in other species.

Role of artesunate in TGF‑β1‑induced renal tubular epithelial‑mesenchymal transdifferentiation in NRK‑52E cells

The implications of epithelial-mesenchymal transdifferentiation (EMT) have extended beyond the confines of renal fibrosis to renal tubulointerstitial fibrosis. It has been proposed that EMT may be one of the mechanisms involved in the pathogenesis of renal fibrosis. However, the underlying mechanisms remain unknown. Transforming growth factor (TGF)-β1 is considered to be an important cytokine which regulates the transdifferentiation of tubular epithelial cells into myofibroblasts in renal tubulointerstitial fibrosis. In the present study, normal rat kidney tubular epithelial cells (NRK-52E) were treated for 48 h with TGF-β1 (5 ng/ml) and different concentrations of artesunate (ART; 0.01, 0.1 and 1 µg/ml). Western blotting, reverse transcription-semi quantitative polymerase chain reaction analysis and immunofluorescence staining were used to evaluate the expression of bone morphogenetic protein (BMP)-7, uterine sensitization-associated gene (USAG)-1, E-cadherin, α-smooth muscle actin (α-SMA) and extracellular matrix collagen type I (Col I) mRNA. ART was able to attenuate renal injury in a unilateral ureteral obstruction model. However, its anti-fibrotic effect remains to be elucidated. In the present study, it was observed that ART was able to ameliorate the TGF-β1-induced alterations in cellular morphology. In addition, ART inhibited the TGF-β1-induced USAG-1 increase and the decrease in BMP-7. Treatment with ART markedly attenuated the TGF-β1-induced upregulation of α-SMA and downregulation of E-cadherin. Additionally, ART was able to significantly attenuate the deposition of interstitial collagens, including Col I. The results of the present study further verified the therapeutic efficacy of ART in TGF-β1-induced renal interstitial fibrosis. These findings indicated that ART may hold the potential to prevent chronic kidney diseases via the suppression of USAG-1 expression or by increasing BMP-7 expression.

TGF-β1-miR-200a-PTEN induces epithelial-mesenchymal transition and fibrosis of pancreatic stellate cells

Although the function of miR-200a has been discussed in many cancers and fibrotic diseases, its role in pancreatic fibrosis is still poorly understood. In this study, we for the first time confirm that miR-200a attenuates TGF-β1-induced pancreatic stellate cells activation and extracellular matrix formation. First, we find that TGF-β1 induces activation and extracellular matrix (ECM) formation in PSCs, and the effects are blocked by the inhibitor of PI3K (LY294002). Furthermore, we identify that miR-200a is down-regulated in TGF-β1-activated PSCs, and up-regulation of miR-200a inhibits PSCs activation induced by TGF-β1. Meanwhile, TGF-β1 inhibits the expression of the epithelial marker E-cadherin, and increases the expression of mesenchymal markers vimentin, and the expression of ECM proteins a-SMA and collagen I, while miR-200a mimic reversed the above effects in PSCs, indicating that miR-200a inhibits TGF-β1-induced activation and epithelial-mesenchymal transition (EMT). In addition, overexpression of miR-200a promotes the expression of PTEN and decreases the expression of matrix proteins and attenuates phosphorylation of Akt and mTOR. Taken together, our study uncovers a novel mechanism that miR-200a attenuates TGF-β1-induced pancreatic stellate cells activation and ECM formation through inhibiting PTEN /Akt/mTOR pathway.