Fibrosis in the kidney: is a problem shared a problem halved?

M2 macrophage polarization modulates epithelial-mesenchymal transition in cisplatin-induced tubulointerstitial fibrosis

Cisplatin-induced nephrotoxicity leaded to apoptosis of tubular epithelial cells (ECs) and tubulointerstitial fibrosis through ROS stress and inflammatory cytokines. Tubulointerstitial fibrosis caused by cisplatin might be via activation of resident fibroblasts and epithelial-mesenchymal transition (EMT) of tubular ECs. Inflammatory niche was crucial for progression of fibroblast activation or EMT. It had been reported that M1/M2 macrophage polarization regulated pro-inflammation or pro-resolving phase in damage repairing. However, the role of macrophage polarization on cisplatin-induced EMT of tubular ECs had not been well elucidated. In this study, we used co-cultured cell model and condition medium to examine the interaction between tubular ECs, fibroblasts and M1/M2 macrophages. Our data showed that cisplatin alone induced incomplete EMT of tubular ECs, whereas fibroblasts co-cultured with cisplatin-treated ECs could lead to fibroblast activation by detection of α-SMA and collagen-1. Moreover, decrease of iNOS and increase of argenase-1 and CD206 expression indicated that macrophages co-cultured with cisplatin-treated ECs would turn to M2 phenotype. Finally, we found that condition medium of M2 macrophages could promote complete EMT of cisplatin-treated ECs. Taken together, cisplatin created an inflammatory niche via tubular ECs to activate fibroblasts and stimulated M2 macrophage polarization. M2 macrophages could turn back to promote EMT of cisplatin-treated ECs. These results revealed the cooperative roles of tubular ECs, fibroblast and M2 macrophages to facilitate the progression of renal fibroblasis.

Clinical application of sonoelastography in thyroid, prostate, kidney, pancreas, and deep venous thrombosis

This article reviews the clinical applications of current ultrasound elastography methods in non-hepatic conditions including thyroid nodules, prostate cancer, chronic kidney disease, solid renal lesions, pancreatic lesions, and deep vein thrombosis. Pathophysiology alters tissue mechanical properties via ultrastructural changes including fibrosis, increased cellularity, bleeding, and necrosis, creating a target biomarker, which can be imaged qualitatively or quantitatively with US elastography. US elastography methods can add information to conventional US methods and improve the diagnostic performance of conventional US in a range of disease processes.

Animal Models to Study Links between Cardiovascular Disease and Renal Failure and Their Relevance to Human Pathology

The close association between cardiovascular pathology and renal dysfunction is well documented and significant. Patients with conventional risk factors for cardiovascular disease like diabetes and hypertension also suffer renal dysfunction. This is unsurprising if the kidney is simply regarded as a “modified blood vessel” and thus, traditional risk factors will affect both systems. Consistent with this, it is relatively easy to comprehend how patients with either sudden or gradual cardiac and or vascular compromise have changes in both renal hemodynamic and regulatory systems. However, patients with pure or primary renal dysfunction also have metabolic changes (e.g., oxidant stress, inflammation, nitric oxide, or endocrine changes) that affect the cardiovascular system. Thus, cardiovascular and renal systems are intimately, bidirectionally and inextricably linked. Whilst we understand several of these links, some of the mechanisms for these connections remain incompletely explained. Animal models of cardiovascular and renal disease allow us to explore such mechanisms, and more importantly, potential therapeutic strategies. In this article, we review various experimental models used, and examine critically how representative they are of the human condition.

Shear wave elastography in chronic kidney disease: a pilot experience in native kidneys

Background

There currently is a need for a non-invasive measure of renal fibrosis. We aim to explore whether shear wave elastography (SWE)-derived estimates of tissue stiffness may serve as a non-invasive biomarker that can distinguish normal and abnormal renal parenchymal tissue.

Methods

Participants with CKD (by estimated GFR) and healthy volunteers underwent SWE. Renal elasticity was estimated as Young’s modulus (YM) in kilopascals (kPa). Univariate Wilcoxon rank-sum tests were used.

Results

Twenty-five participants with CKD (median GFR 38 mL/min; quartile 1, quartile 3 28, 42) and 20 healthy controls without CKD underwent SWE performed by a single radiologist. CKD was associated with increased median YM (9.40 [5.55, 22.35] vs. 4.40 [3.68, 5.70] kPa; p = 0.002) and higher median intra-subject inter-measurement estimated YM’s variability (4.27 [2.89, 9.90] vs. 1.51 [1.21, 2.05] kPa; p < 0.001).

Conclusions

SWE-derived estimates of renal stiffness and intra-subject estimated stiffness variability are higher in patients with CKD than in healthy controls. Renal fibrosis is a plausible explanation for the observed difference in YM. Further studies are required to determine the relationship between YM, estimated renal stiffness, and renal fibrosis severity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0120-7) contains supplementary material, which is available to authorized users.

SnoN as a novel negative regulator of TGF-β/Smad signaling: a target for tailoring organ fibrosis

Remodeling of the extracellular matrix is beneficial during the acute wound healing stage following tissue injury. In the short term, resident fibroblasts and myofibroblasts regulate the matrix remodeling process through production of matricellular protein components that provide structural support to the damaged tissue. This process is largely governed by the transforming growth factor-β1 (TGF-β1) pathway, a critical mediator of the remodeling process. In the long term, chronic activation of the TGF-β1 pathway promotes excessive synthesis and deposition of matrix proteins, including fibrillar collagens, which ultimately leads to organ failure. SnoN (and its alternatively-spliced isoforms SnoN2, SnoA, and SnoI) is one of four members of a family of negative regulators of TGF-β1 signaling that includes Ski and functional Smad-suppressing elements on chromosomes 15 and 18. SnoN has been shown to be structurally and functionally similar to Ski and has been demonstrated to directly interact with Ski to abrogate gene expression. Despite this, little progress has been made in delineating a specific role for SnoN in the regulation of myofibroblast phenotype and function. This review outlines the current body of knowledge of what we refer to as the “Ski-Sno superfamily,” with a focus on the structural and functional importance of SnoN in mediating the fibrotic response by myofibroblasts following tissue injury.

De novo design based pharmacophore query generation and virtual screening for the discovery of Hsp-47 inhibitors

Heat shock protein-47 (Hsp-47) is exclusive collagen specific molecular chaperone involved in the maturation, processing and secretion of procollagen. Hsp-47 is consistently upregulated in several fibrotic diseases. Till date there is no potential antifibrotic small molecule drug available and Hsp-47 is known to be potential therapeutic target for fibrotic disorder and drug designing. We used the de novo drug design approach followed by pharmacophore generation and virtual screening to propose Hsp-47 based antifibrotic molecules. We used e-LEAD server for de novo drug design and ZINCPharmer for 3D pharmacophore generation and virtual screening. The virtually screened molecule may inhibit direct recruitment of collagen triple helix to interact with Hsp-47 and act as antifibrotic drug.

The balance mediated by miRNAs and the heme oxygenase 1 feedback loop contributes to biological effects

Heme oxygenase-1 (HMOX1) is a ubiquitously expressed inducible enzyme that degrades heme to carbon monoxide, biliverdin, and free iron ions. Since 1950, many studies have revealed the role of HMOX1 in reducing the impact of oxidative stress in many types of diseases, such as Alzheimer's disease, heart disease, and the development of tumors. These effects arise as a result of the removal of heme, the biological activities of the products of HMOX1 and the activity of HMOX1 itself. However, HMOX1 has some contradictory effects. The discovery of microRNAs (miRNAs) and their relationship with HMOX1 has provided a new direction for research in this field. Here, we discuss the role of a potential regulatory feedback loop between HMOX1 and miRNAs in pathological processes based on recently published data. We hope to describe a new mechanism for HMOX1 function based on miRNAs to address the contradictory results reported in the literature.

Increasing cGMP-dependent protein kinase activity attenuates unilateral ureteral obstruction-induced renal fibrosis

Our previous studies support the protective effect of cGMP and cGMP-dependent protein kinase I (PKG-I) pathway on the development of renal fibrosis. Therefore, in the present studies, we determined whether pharmacologically or genetically increased PKG activity attenuates renal fibrosis in a unilateral ureteral obstruction (UUO) model and also examined the mechanisms involved. To increase PKG activity, we used the phosphodiesterase 5 inhibitor sildenafil and PKG transgenic mice. UUO model was induced in wild-type or PKG-I transgenic mice by ligating the left lateral ureteral and the renal fibrosis was observed after 14 days of ligation. Sildenafil was administered into wild-type UUO mice for 14 days. In vitro, macrophage and proximal tubular cell function was also analyzed. We found that sildenafil treatment or PKG transgenic mice had significantly reduced UUO-induced renal fibrosis, which was associated with reduced TGF-β signaling and reduced macrophage infiltration into kidney interstitial. In vitro data further demonstrated that both macrophages and proximal tubular cells were important sources of UUO-induced renal TGF-β levels. The interaction between macrophages and tubular cells contributes to TGF-β-induced renal fibrosis. Taken together, these data suggest that increasing PKG activity ameliorates renal fibrosis in part through regulation of macrophage and tubular cell function, leading to reduced TGF-β-induced fibrosis.

Tyrosine kinases inhibition by Imatinib slows progression in chronic anti-thy1 glomerulosclerosis of the rat

Background

Chronic progressive mesangioproliferative nephropathy represents a major cause of end-stage renal disease worldwide. Until now, effective approaches to stop or even slow its progression are limited. We tested the effects of an inhibitor of PDGF receptor, abl and c-kit tyrosine kinases, Imatinib, in a chronic progressive model of mesangioproliferative glomerulosclerosis.

Methods

Anti-thy1 glomerulosclerosis was induced by injection of anti-thy1 antibody into uninephrectomized Wistar rats. One week after disease induction, according to the degree of proteinuria, animals were stratified and assigned to chronic glomerulosclerosis (cGS) and cGS plus Imatinib (10 mg/kg body weight/day). In week 20, renoprotective actions of Imatinib were analyzed by a set of functional, histological and molecular biological parameters.

Results

Untreated cGS rats showed elevation of systolic blood pressure and marked progression in proteinuria, renal fibrosis, cell infiltration, cell proliferation and function lost. Administration of Imatinib went along significantly with lower systolic blood pressure (−10 mmHg) and proteinuria (−33%). Imatinib administration was paralled by significant reductions in tubulointerstitial accumulation of matrix proteins (−44%), collagen I deposition (−86%), expression of TGF-beta1 (−30%), production of fibronectin (−23%), myofibroblast differentiation (−87%), macrophage infiltration (−36%) and cell proliferation (−45%), respectively. In comparison with untreated cGS animals, Imatinib therapy lowered also blood creatinine (−41%) and blood urea concentrations (−36%) and improved creatinine clearance (+25%). Glomerular fibrotic changes were lowered moderately by Imatinib.

Conclusions

Therapy with Imatinib limits the progressive course of chronic anti-thy1 glomerulosclerosis towards tubulointerstitial fibrosis and renal insufficiency. This was paralleled by direct and indirect sign of TGF-β1 and PDGF inhibition. The findings suggest that the pharmacological principal of inhibition of tyrosine kinases with drugs such as Imatinib might serve as approach for limiting progression of human mesangioproliferative glomerulosclerosis.

Corticomedullary strain ratio: a quantitative marker for assessment of renal allograft cortical fibrosis

OBJECTIVES

To quantitatively assess the correlation between the corticomedullary strain ratio and cortical fibrosis in renal transplants.

METHODS

Using quasistatic ultrasound elasticity imaging, we prospectively assessed the corticomedullary strain ratio in renal allografts of 33 patients who underwent renal transplant sonography and biopsy. Based on Banff score criteria for renal cortical fibrosis, 33 allografts were divided into 2 groups: group 1 (n = 19), with mild (<25%) fibrosis; and group 2 (n = 14), with moderate (>26%) fibrosis. We used 2-dimensional speckle-tracking software to perform offline analysis of cortical and medullary strain induced by external compression by the ultrasound transducer. We then calculated the corticomedullary strain ratio (cortical normalized strain/medullary normalized strain; normalized strain = developed strain/applied strain [deformation from the abdominal wall to the pelvic muscles]). An unpaired 2-tailed t test was used to determine differences in normalized strain and the strain ratio between the groups. Receiver operating characteristic curve analysis was performed to determine the best strain ratio cutoff value for identifying moderate fibrosis.

RESULTS

Normalized strain differed between the cortex and medulla (mean ± SD: group 1, 4.58 ± 2.02 versus 2.58 ± 1.38; P = .002; group 2, 1.71 ± 0.42 versus 2.60 ± 0.87; P = .0011). The strain ratio in group 1 was higher than in group 2 (2.06 ± 1.33 versus 0.70 ± 0.20; P = .0007). The area under the receiver operating characteristic curve was 0.964. The sensitivity and specificity of a strain ratio cutoff value of 0.975 for determining moderate fibrosis were 92.9% and 94.7%, respectively.

CONCLUSIONS

Strain values vary in different compartments of the kidney. The corticomedullary strain ratio on ultrasound elasticity imaging decreases with increasing renal cortical fibrosis, which makes it potentially useful as a noninvasive quantitative marker for monitoring the progression of fibrosis in renal transplants.