Dysregulation of Lysyl Oxidases Expression in Diabetic Nephropathy and Renal Cell Carcinoma

Lysyl oxidases (LOXs) are amino oxidase enzymes that catalyze the oxidative deamination of lysine and hydroxylysine residues to form allysine, the first step towards the development of the final cross-linking reaction in collagens, a crucial macromolecule that reinforces extracellular matrices. Basement membranes are specialized extracellular matrices that are essential components of the glomerular filtration barrier, which also support tubular epithelial cells. Lysyl oxidases are post-translational enzymes indispensable for tissue architecture, participating actively in the development and function of kidneys. The differential expression and dysregulation of these enzymes promote diabetic nephropathy, one of the major complications observed in end-stage renal diseases. In addition, these enzymes act as transcription factors that trigger the epithelial-mesenchymal transition responsible for the generation of different cancers. In the kidney, the expression studies in physiological conditions identified LOXL1 and LOXL2 as constituent proteins of glomerular basement membranes. Besides, LOX and LOXL2 are upregulated in fibrosis and renal cell carcinoma. The current review summarizes the physiological expression of LOXs enzymes in the nephrons, including glomerulus and tubules. Their roles in renal diseases are particularly highlighted in diabetic nephropathy and renal cell carcinoma, two pathophysiological conditions where these enzymes have been demonstrated to participate. The focus of the present study is to describe and discuss the current understanding in this field. The current potential of LOXs enzymes as a biomarker and pharmacological target to kidney diseases that involves extracellular matrix cross-linking enzymes is also discussed. LOXs isoforms and their capacity as therapeutic targets could be used for diagnostic and prognostic purposes and in treating these renal complications.

The Influence of a Nanopatterned Scaffold that Mimics Abnormal Renal Mesangial Matrix on Mesangial Cell Behavior

The alteration of mesangial matrix (MM) components in mesangium, such as type IV collagen (COL4) and type I collagen (COL1), is commonly found in progressive glomerular disease. Mesangial cells (MCs) responding to altered MM, show critical changes in cell function. This suggests that the diseased MM structure could play an important role in MC behavior. To investigate how MC behavior is influenced by the diseased MM 3D nanostructure, we fabricated the titanium dioxide (TiO2)-based nanopatterns that mimic diseased MM nanostructures. Immortalized mouse MCs were used to assess the influence of disease-mimic nanopatterns on cell functions, and were compared with a normal-mimic nanopattern. The results showed that the disease-mimic nanopattern induced disease-like behavior, including increased proliferation, excessive production of abnormal MM components (COL1 and fibronectin) and decreased normal MM components (COL4 and laminin α1). In contrast, the normal-mimic nanopattern actually resulted in cells displaying normal proliferation and the production of normal MM components. In addition, increased expressions of α-smooth muscle actin (α-SMA), transforming growth factor β1 (TGF-β1) and integrin α5β1 were detected in cells grown on the disease-mimic nanopattern. These results indicated that the disease-mimic nanopattern induced disease-like cell behavior. These findings will help further establish a disease model that mimics abnormal MM nanostructures and also to elucidate the molecular mechanisms underlying glomerular disease.

Correlation Between Renal Cortical Stiffness and Histological Determinants by Point Shear-Wave Elastography in Patients With Kidney Transplantation

INTRODUCTION

Renal allograft biopsy is the gold standard for the detection of histological lesions of chronic allograft dysfunction. The identification of a noninvasive routine test would be desirable. Elastosonography is used to assess tissue stiffness according to viscosity, and no data are available on the use of point quantification shear-wave elastography (ElastPQ) for the evaluation of renal chronic lesions.

RESEARCH QUESTION

To evaluate the feasibility of ElastPQ to assess cortical allograft stiffness and to determine the correlation of clinical, biological, and pathological factors with the diagnostic accuracy of kidney stiffness values in patients with histological lesions.

DESIGN

Forty-two patients underwent kidney transplant biopsy and 10 valid measurements of ElastPQ, blindly performed by 2 operators. The interobserver reproducibility was assessed according to intraclass correlation coefficient. The ElastPQ measurements and the clinical data were compared using the Spearman correlation analysis.

RESULTS

97.6% reliable measurements were obtained using ElastPQ, with an excellent interobserver agreement. The kidney stiffness was significantly higher in the patients with a time since transplantation >12 months and was correlated with chronic lesions (interstitial fibrosis, tubular atrophy transplant glomerulopathy, and mesangial matrix), with the interstitial fibrosis/tubular atrophy, score and with the sum of the scores of the chronic lesions. Mesangial matrix increase is the only independent determinant of kidney stiffness.

DISCUSSION

ElastPQ is a noninvasive, reproducible, and sensitive diagnostic tool able to detect moderate/severe chronic lesions. Its routine use during follow-up can identify patients eligible for biopsy, which remains the gold standard exam for detecting chronic allograft dysfunction.

FAR2 is associated with kidney disease in mice and humans

Mesangial matrix expansion is an important process in the initiation of chronic kidney disease, yet the genetic factors driving its development are unknown. Our previous studies have implicated Far2 as a candidate gene associated with differences in mesangial matrix expansion between mouse inbred strains. Consistent with the hypothesis that increased expression of Far2 leads to mesangial matrix expansion through increased production of platelet-activating factor precursors, we show that FAR2 is capable of mediating de novo platelet-activating factor synthesis in vitro and driven by the transcription factor NKX3.2. We demonstrate that knockdown of Far2 in mice delays the progression of mesangial matrix expansion with at least six months (equivalent to ~15 yr in human). Furthermore, we show that increased FAR2 expression in human patients is associated with diabetic nephropathy, lupus nephritis, and IgA nephropathy. Taken together, these results highlight FAR2's role in the development of mesangial matrix expansion and chronic kidney disease.