Accelerated glomerular injury in hemi-nephrectomized transgenic mice of mesangial cell-predominant serpin, megsin

Mesangial cells play a critical role in the maintenance of normal glomerular functions such as matrix remodeling and immune complex disposal. We recently identified a novel human mesangium-predominant gene, megsin, which is a new member of the serine protease inhibitor (serpin) superfamily. While our previous studies demonstrated progressive mesangial matrix expansion and an increase in the number of mesangial cells in megsin transgenic mice, it took 40 weeks to develop these manifestations. Here we performed hemi-nephrectomy to accelerate glomerular injury in megsin transgenic mice. Hemi-nephrectomized transgenic mice developed focal segmental mesangial expansion, which was associated with proteinuria. Megsin has thus a biologically relevant influence on the development of glomerular damage. The hemi-nephrectomized model of this transgenic mouse might serve as a tool to investigate the mechanisms of glomerular disease.     

Overexpression of the serpin megsin induces progressive mesangial cell proliferation and expansion

Mesangial cells maintain normal glomerular function by mediating ECM remodeling and immune complex disposal. We have recently identified megsin, a novel member of the serine protease inhibitor (serpin) superfamily predominantly expressed in the mesangium. While our previous studies suggested a role for megsin in the pathogenesis of human glomerular diseases, its exact biological significance remained unknown. Here we produced two lines of megsin transgenic mice. Overexpression of megsin led to progressive mesangial matrix expansion and an increase in the number of mesangial cells. These glomerular lesions were accompanied by an augmented immune complex deposition, together with Ig's and complement. Binding and functional assays in vitro identified plasmin as one biological substrate of megsin and confirmed its activity as a proteinase inhibitor. Transgenic animals exhibiting nephritis as a result of treatment with anti--glomerular basement membrane antiserum showed significantly more persistent expansion of the mesangial ECM than was seen in parental mice. Megsin therefore exerts a biologically relevant influence on mesangial function, and on the mesangial microenvironment, such that simple overexpression of this endogenous serpin engenders elementary mesangial lesions.     

Gene transfer into the rat renal glomerulus via a mesangial cell vector: site-specific delivery, in situ amplification, and sustained expression of an exogenous gene in vivo.

To evaluate the pathophysiological function of specific molecules in the renal glomerulus, selective, sustained, and modifiable expression of such molecules will be required. Towards achieving this end, we devised a gene transfer system using the glomerular mesangial cell as a vector for gene delivery. A reporter gene which encodes bacterial beta-galactosidase was introduced into cultured rat mesangial cells, and the stable transfectants were transferred into the rat kidney via the renal artery, leading to selective entrapment within the glomeruli. In the normal kidney, the reporter cells populated into 57 +/- 13% of glomeruli site specifically, and the expression of beta-galactosidase was sustained for 4 wk and declined thereafter. Within the glomerulus, some of the reporter cells remained in the glomerular capillaries, while others repopulated the mesangial area and, in part, extended their cytoplasmic processes toward the surrounding capillaries. When the cells were transferred into glomeruli subjected to transient mesangiolysis induced by monoclonal antibody 1-22-3, in situ expression of beta-galactosidase was amplified 7-12-fold, and the enhanced level of expression continued for up to 8 wk. The mesangial cell vector system thus achieves site-specific delivery of an exogenous gene into the glomerulus and is amenable to in situ amplification and sustained expression by preconditioning of the target site.     

Mesangial cell autoantigens in immunoglobulin A nephropathy and Henoch-Schönlein purpura.

The autoantigen(s) that we have previously described in human glomeruli, recognized in IgA nephropathy, has (have) been identified as mesangial cell in origin. Cultured mesangial cells expressed 48- and 55-kD components binding IgG isotype autoantibodies (IgG-MESCA) present in sera of patients with both IgA nephropathy and Henoch-Sch?nlein purpura (HSP). IgG-MESCA were not detected in sera of normals, or patients with other autoimmune-mediated glomerulonephritides: anti-glomerular basement membrane disease, Wegener's granulomatosis, or in IgM-mesangial proliferative disease. Binding specificity was proven by F(ab')2 studies in enzyme-linked immunosorbent assay (ELISA) and Western blotting, and there was no significant affinity of IgA or IgM immunoglobulins. Fluorescein isothiocyanate-conjugated IgG from ELISA-positive sera localized to the mesangium and peripheral capillary loops of glomeruli, supporting the belief that the antigen is expressed in normal human renal tissue. However, only about one third of mesangial cells in culture showed affinity for IgG from ELISA-positive sera, suggesting variable expression of the antigen(s) in vitro. The only autoantigen(s) present in glomeruli, and extractable from whole normal glomeruli by the techniques employed, localized on the mesangial cell. In both IgA nephropathy and HSP, autoimmunity was intermittently present, with fluctuating levels of IgG-MESCA detectable in sera. There were positive correlations with the degree of glomerular injury assessed by erythrocyturia and proteinuria in IgA nephropathy, but significance was reached with only the degree of hematuria in HSP. These findings suggest a contributing role in the pathogenesis of the mesangial proliferative lesions and demonstrate autoimmunity common to both IgA nephropathy and HSP.     

Rat glomerular mesangial cells synthesize basic fibroblast growth factor. Release, upregulated synthesis, and mitogenicity in mesangial proliferative glomerulonephritis.

Mesangial injury and cell proliferation are frequent findings in various glomerular diseases in man. Previous studies have demonstrated that basic fibroblast growth factor (bFGF) is a potent mesangial cell mitogen in vitro. To further elucidate the role of bFGF in rat mesangial cell (RMC) proliferation, we examined whether RMC synthesize bFGF in vitro and whether bFGF is involved in mesangial proliferation in vivo. Cultured RMC expressed bFGF protein (23, 21.5, and 18 kD forms) and bFGF mRNA, and released biologically active bFGF into the culture medium after antibody- and complement-mediated injury. Normal rat glomeruli in vivo contained no detectable bFGF mRNA, but bFGF protein (23 and 21.5 kD) could be demonstrated, which immunolocalized to the mesangium. Glomerular bFGF decreased markedly during the acute phase of glomerulonephritis induced by anti-Thy 1.1 antibody, compatible with mesangial bFGF release after complement-mediated mesangiolysis. During the subsequent mesangial proliferative phase, glomerular bFGF protein and mRNA increased above normal. Intrarenal infusion of heparin did not affect the bFGF immunostaining of glomeruli at this stage, indicating a predominantly intracellular localization of the bFGF. The capability of bFGF to mediate proliferation in the anti-Thy 1.1 model was further supported by experiments in which intravenous bFGF given 24 h after a subnephritogenic dose of anti-Thy 1.1 antibody led to a 4.9- to 5.1-fold increase in glomerular cell proliferation (with > 60% of the cells identified as mesangial cells by double immunolabeling). No such increase was observed in normal rats injected with bFGF. These data show that mesangial cells produce and release bFGF after injury and that bFGF is mitogenic for injured mesangial cells in vivo. Release of mesangial cell bFGF thus may be an important mechanism involved in the initiation of mesangial cell proliferation in vivo.     

The glomerular mesangium: I. Kinetic studies of macromolecular uptake in normal and nephrotic rats

This study was designed to define quantitatively the function of the rat glomerular mesangium in the uptake and processing of intravenously administered protein macromolecules (radiolabeled aggregated human IgG, AHIgG-(125)I), to relate this function to that of the general reticuloendothelial system, and to examine the effects of increased glomerular permeability to protein on the mesangial cell system.Mesangial localization of human IgG as demonstrated by immunofluorescent microscopy showed good correlation with concentrations of AHIgG-(125)I in preparations of isolated glomeruli. In normal rats the concentrations of AHIgG-(125)I in glomeruli were similar to those of lung, liver, and spleen and demonstrated a rapid decrease with increasing time intervals after aggregate administration.In rats given aminonucleoside of puromycin a marked increase in mesangial uptake of aggregates was found while studies of nephrotic lungs, liver, spleen, and blood showed no such differences. Glomerular levels of AHIgG-(125)I in aminonucleoside animals could not be correlated with the quantity of proteinuria.Nephrotic and control animals given unaggregated human IgG showed little glomerular localization by immunofluorescent microscopy; no difference in the concentration of this protein in nephrotic as compared to control glomerular isolates was found.Thus, the mesangium in normal animals functions in a manner analogous to that of the general reticuloendothelial system. In nephrotic rats the mesangial uptake of macromolecules is makedly increased, a finding not observed in other tissues.     

Glomerulosclerosis is transmitted by bone marrow–derived mesangial cell progenitors

We found that ROP Os/+ (Os/+) mice had diffuse glomerulosclerosis and glomerular hypertrophy and that their mesangial cells (the vascular smooth muscle cells of the glomerulus) displayed an apparent sclerosing phenotype. Since mesangial cells are the major source of scar tissue in glomerulosclerosis, we postulated that the sclerosis phenotype was carried by mesangial cell progenitors and that this phenotype could be derived from the bone marrow (BM). Therefore, we transplanted BM from Os/+ mice into congenic ROP +/+ mice (+/+ mice), which have normal glomeruli. We found that glomeruli of +/+ recipients of Os/+ marrow contained the Os/+ genotype, were hypertrophied, and contained increased extracellular matrix. Clones of recipient glomerular mesangial cells with the donor genotype were found in all +/+ recipients that developed mesangial sclerosis and glomerular hypertrophy, whereas +/+ recipients of +/+ BM had normal glomeruli. Thus, the sclerotic (Os/+) or normal (+/+) genotype and phenotype were present in, and transmitted by, BM-derived progenitors. These data show that glomerular mesangial cell progenitors are derived from the BM and can deliver a disease phenotype to normal glomeruli. Glomerular lesions may therefore be perpetuated or aggravated, rather than resolved, by newly arriving progenitor cells exhibiting a disease phenotype.     

Extraglomerular origin of the mesangial cell after injury. A new role of the juxtaglomerular apparatus.

We investigated the origin of the glomerular mesangial cell, a smooth muscle-like cell that provides structural support in the glomerulus. Injection of anti-Thy 1 antibody that binds the Thy 1 antigen on rat mesangial cells eliminated (> 95%) the mesangial population at 20-28 h, while Thy 1-positive cells in the juxtaglomerular apparatus (JGA) were sequestered from the circulation and survived. Single pulse labeling with [3H]thymidine at 36 h labeled Thy 1-positive cells in the JGA and hilus. Serial biopsies demonstrated the progressive migration (5-15 micron/d) and proliferation of these mesangial reserve cells until the entire glomerulus was repopulated. The regenerating mesangial population expressed contractile and migratory proteins preferentially at the leading edge of the migratory front. Single as well as multiple pulse labeling with [3H]thymidine confirmed that the entire mesangial cell repopulation originated from only a few mesangial reserve cells. These reserve cells resided in the extraglomerular mesangium in the JGA and were not renin-secreting cells, macrophages, smooth muscle cells, or endothelial cells. These studies document mesangial cell migration in the anti-Thy 1 model of mesangial proliferative glomerulonephritis and provide evidence for a new role for the juxtaglomerular apparatus in the maintenance of the mesangial cell population.     

Creation of an In vivo cytosensor using engineered mesangial cells. Automatic sensing of glomerular inflammation controls transgene activity.

Automatic control over exogenous gene expression in response to the activity of disease is a crucial hurdle for gene transfer-based therapies. Towards achieving this goal, we created a "cytosensor" that perceives local inflammatory states and subsequently regulates foreign gene expression. alpha-Smooth muscle actin is known to be expressed in glomerular mesangial cells exclusively in pathologic situations. CArG box element, the crucial regulatory sequence of the alpha-smooth muscle actin promoter, was used as a sensor for glomerular inflammation. Rat mesangial cells were stably transfected with an expression plasmid that introduces a beta-galactosidase gene under the control of CArG box elements. In vitro, the established cells expressed beta-galactosidase exclusively after stimulation with serum. To examine whether the cells are able to automatically control transgene activity in vivo, serum-stimulated or unstimulated cells were transferred into normal rat glomeruli or glomeruli subjected to anti-Thy 1 glomerulonephritis. When stimulated cells were transferred into the normal glomeruli, beta-galactosidase expression was switched off in vivo within 3 d. In contrast, when unstimulated cells were transferred into the nephritic glomeruli, transgene expression was substantially induced. These data indicate the feasibility of using the CArG box element as a molecular sensor for glomerular injury. In the context of advanced forms of gene therapy, this approach provides a novel concept for automatic regulation of local transgene expression where the transgene is required to be activated during inflammation and deactivated when the inflammation has subsided.     

Physiologic regulation of atrial natriuretic peptide receptors in rat renal glomeruli.

Isolated rat renal glomeruli and cultured glomerular mesangial and epithelial cells were examined for atrial natriuretic peptide (ANP) receptors, and for ANP-stimulated cyclic guanosine monophosphate (cGMP) generation. In glomeruli from normal rats, human (1-28) 125I-ANP bound to a single population of high affinity receptors with a mean equilibrium dissociation constant of 0.46 nM. Human (1-28) ANP markedly stimulated cGMP generation, but not cAMP generation in normal rat glomeruli. Analogues of ANP that bound to the glomerular ANP receptor with high affinity stimulated cGMP accumulation, whereas the (13-28) ANP fragment, which failed to bind to the receptor, was devoid of functional activity. Cell surface receptors for ANP were expressed on cultured glomerular mesangial but not epithelial cells, and appreciable ANP-stimulated cGMP accumulation was elicited only in mesangial cells. Approximately 12,000 ANP receptor sites were present per mesangial cell, with an average value for the equilibrium dissociation constant of 0.22 nM. Feeding of a low-salt diet to rats for 2 wk resulted in marked up regulation of the glomerular ANP receptor density to a mean of 426 fmol/mg protein, compared with 116 fmol/mg in rats given a high-salt diet. A modest reduction in the affinity of glomerular ANP receptors was also observed in rats fed the low-salt diet. ANP-stimulated cGMP generation in glomeruli did not change with alterations in salt intake. We conclude that high salt feeding in the rat results in reduced glomerular ANP receptor density relative to values in salt restricted rats. Furthermore, the mesangial cell is a principal target for ANP binding in the glomerulus.     

Tissue culture of isolated glomeruli in experimental crescentic glomerulonephritis

As a means of studying mechanisms of response to injury in glomerulonephritis, glomeruli from normal sheep and rabbits and from sheep and rabbits with experimental crescentic glomerulonephritis have been isolated and grown in tissue culture. The cellular outgrowths from the normal and diseased glomeruli have been compared. The outgrowth of glomeruli from normal animals contained only two cell populations whose microscopic and ultrastructural appearances were of epithelial and mesangial cells. The same cells were also observed in the outgrowths of glomeruli from animals with crescenti nephritis but in addition a third population of cells was present in large numbers. These cells were identified as macrophages by their mobility, ultrastructure, phagocytic capacity, and presence of Fc receptors. Glomerular outgrowth from sheep with crescentic glomerulonephritis contained 170 +/- 20 (SEM) macrophages and outgrowths from rabbits with crescentic nephritis contained 64 +/- 6 (SEM) macrophages per glomerulus. We have previously observed large numbers of macrophages in the outgrowth of isolated glomeruli from humans with rapidly progressive crescentic glomerulonephritis. The predominance of the macrophage in cultures of glomeruli from both human and animal crescentic glomerulonephritis suggests that this is an important cell in the inflammatory reaction occurring in crescentic glomerulonephritis and may comprise a substantial proportion of the cells forming the crescent.     

THE GLOMERULAR MESANGIUM : III. ACUTE IMMUNE MESANGIAL INJURY: A NEW MODEL OF GLOMERULONEPHRITIS

A mechanism of immune glomerular injury is described based on the fixation of antibody (Ab) to an antigen (Ag) that has localized in the glomerular mesangium. Rabbits were given, intravenously (i.v.), aggregated human IgG (AHIgG) or albumin (AHSA) and 10 h later, when the Ag by immunofluorescent microscopy was present in the mesangium, a kidney was removed and transplanted into a normal rabbit. The recipient then received, i.v., rabbit anti-HIgG or anti-HSA. Within minutes of Ab infusion, glomeruli of the donor kidney had polymorphonuclear (PMN) infiltration that over the next few hours became marked and was associated with glomerular cell swelling. At 24 h a decrease in PMN's and early mesangial proliferation was seen. By 3 days there was marked mesangial hypercellularity and increased mesangial matrix. Within minutes after Ab administration rabbit IgG, C3, and fibrin were seen in the glomerular mesangium. There was a fall in complement titer by 1 min after Ab infusion that was due to complement consumption by the donor kidney. Complement then returned to normal levels by 48 h. Significant glomerular injury did not occur (a) in the recipient's own kidney, (b) from Ag administration and transplantation without recipient Ab administration, or (c) from transplantation and Ab administration without prior Ag administration. These studies demonstrated that Ag localized in the glomerular mesangium can react with circulating Ab and complement resulting in severe glomerular injury.     

姜黄素对肾小球系膜细胞过氧化物酶体增殖物激活受体γ基因表达的影响

目的：观察姜黄素对肾小球系膜细胞过氧化物酶体增殖物激活受体γ（PPAR-γ）mRNA基因表达水平的影响。方法：将高浓度葡萄糖液及不同浓度的姜黄素液与肾小球系膜细胞共孵育,用逆转录聚合酶链反应（RT-PCR）法,检测各组细胞PPAR-γ mRNA表达强度。结果：单纯高浓度葡萄糖组肾系膜细胞PPAR-γ mRNA表达量（0.394±0.026）显著低于正常对照组（0.995±0.016）,P〈0.01;当姜黄素的浓度达100mg/L时,其PPAR-γ mRNA积分吸光度比值为0.701±0.04,高于高浓度葡萄糖＋姜黄素（25mg/L）组（0.541±0.018）,显著高于高浓度葡萄糖＋姜黄素（6.25mg/L）组（0.432±0.024）,P〈0.01。结论：姜黄素拮抗高浓度葡萄糖对肾系膜细胞PPAR-γ基因表达的抑制作用,上调PPAR-γ mRNA的表达水平。     

VEGF165 mediates glomerular endothelial repair

VEGF(165), the most abundant isoform in man, is an angiogenic cytokine that also regulates vascular permeability. Its function in the renal glomerulus, where it is expressed in visceral epithelial and mesangial cells, is unknown. To assess the role of VEGF(165) in glomerular disease, we administered a novel antagonist - a high-affinity, nuclease-resistant RNA aptamer coupled to 40-kDa polyethylene glycol (PEG) - to normal rats and to rats with mesangioproliferative nephritis, passive Heymann nephritis (PHN), or puromycin aminonucleoside nephrosis (PAN). In normal rats, antagonism of VEGF(165) for 21 days failed to induce glomerular pathology or proteinuria. In rats with mesangioproliferative nephritis, the VEGF(165) aptamer (but not a sequence-scrambled control RNA or PEG alone) led to a reduction of glomerular endothelial regeneration and an increase in endothelial cell death, provoking an 8-fold increase in the frequency of glomerular microaneurysms by day 6. In contrast, early leukocyte influx and the proliferation, activation, and matrix accumulation of mesangial cells were not affected in these rats. In rats with PHN or PAN, administration of the VEGF(165) aptamer did not influence the course of proteinuria using various dosages and administration routes. These data identify VEGF(165) as a factor of central importance for endothelial cell survival and repair in glomerular disease, and point to a potentially novel way to influence the course of glomerular diseases characterized by endothelial cell damage, such as various glomerulonephritides, thrombotic microangiopathies, or renal transplant rejection.     

Secondary nephrotic syndrome due to collagen disease and vasculitis

The most frequent and representative nephrotic syndrome associated with collagen disease is encountered in patients suffering from lupus nephritis. Lupus nephritis is a glomerulonephritis, which discloses various localizations of immune complexes in the endothelium, mesangium and subepithelium. In addition, vasculitides complicated by nephrotic syndrome also show the deposition of immune complexes in their glomeruli, such as Henoch-Sch?nlein nephritis and cryoglobulinemic nephritis. The pathogenetic mechanisms of these nephrotic syndromes are explained as follows. The depositions of immune complexes in glomeruli causes proteinuria through a variety of mechanisms. Namely, subendothelial and mesangial immune deposits give capillary and mesangial injuries as well as inflammation that are mediated through activation of complements and cytokines, and subsequently leads to nephrotic-range proteinuria and impairment of renal function. On the other hand, subepithelial and intramembranous deposits disrupt the regulated arrangement of epithelial cells and slit diaphragms, and then disturb the slit diaphragms. The eventual dysfunction of slit diaphragms accordingly progresses to massive proteinuria even without capillary injury. Therefore, nephrotic syndrome associated with collagen disease or vasculitis is usually observed in lupus nephritis or vasculitis related to immune complex depositions, but is not observed in non-immune complex glomerulopathy or vasculopathy.     

The glomerular mesangium. II. Studies of macromolecular uptake in nephrotoxic nephritis in rats

These studies were designed to explore the effects of nephrotoxic serum (NTS) in rats on the uptake and processing by the glomerular mesangium of intravenously administered protein macromolecules (radiolabeled aggregated human IgG, [125I]AHIgG). Measurements of [125I]AHIgG levels in preparations of isolated glomeruli correlated well with qualitative estimates of glomerular IgG deposition seen by immunofluorescent microscopy. Rats given 2 ml NTS received 25 mg/100 g body wt [125I]AHIgG 48 h later and were sacrificed at varying time intervals thereafter. NTS-treated animals demonstrated a marked increase in glomerular uptake of [125I]AHIgG as compared with concurrent controls but a normal ability to clear [125I]AHIgG from the mesangium over 72 hr. Animals given 1.0, 0.5, and 0.25 ml NTS had neither proteinuria nor significant light microscopic changes, yet had increased uptake of [125I]AHIgG of 4.4, 3.0, and 2.1 times control values, respectively at 8 h after the infusion of aggregates. Rats given 1 ml NTS and 12.5, 6.25, and 3.125 mg [125I]AHIgG/100 g body wt had increased glomerular uptake at 8 h, but there was, within both NTS and control groups, a disproportionate decrease in uptake at lower [125I]AHIgG doses. Rats given cobra venom factor (CoF) followed by a NTS shown to be complement dependent (proteinuria reduced by prior complement depletion with CoF) had less mesangial [125I]AHIgG uptake than NTS controls but greater uptake compared with normal controls. CoF itself had no effect on mesangial or reticuloendothelial system [125I]AHIgG uptake. These studies demonstrate a striking change in glomerular mesangial activity after fixation of nephrotoxic antibodies to the glomerular basement membrane, even in the absence of proteinuria and suggest that subtle alterations of the filtration surface can influence mesangial function. The effect of NTS on the mesangium is due, in large part, to the glomerular injury and proteinuria which nephrotoxic antibodies produce.     

Prophylaxis of antibody-induced acute glomerulonephritis with genetically modified bone marrow-derived vehicle cells

Glomerulonephritis is an inflammatory disease of the renal glomerulus, which often progresses either slowly or rapidly, ending in renal death despite the availability of various antiinflammatory drugs. Gene therapy may be a promising method of suppressing the progression of glomerulonephritis through the blockage of key inflammatory molecule(s). However, the difficulty of local gene delivery into the glomerulus has made the clinical use of gene therapy difficult. As a solution to this issue, we applied a novel ex vivo technique that may allow site-specific gene delivery into the inflamed site and thus suppress local inflammation in the glomerulus, and examined the feasibility of this system as a prophylaxis of glomerulonephritis. The gene encoding the antiinflammatory cytokine interleukin 1 receptor antagonist (IL-1ra) was delivered into animal models of inflamed glomeruli evoked by anti-glomerular basement membrane antibody; this animal model is an analog of the human Goodpasture syndrome. Vehicle cells did indeed accumulate in the glomeruli on the induction of nephritis and were confirmed to secrete recombinant IL-1ra. Renal functions as well as morphology were preserved by this intervention for up to 14 days after IL-1ra introduction. These data demonstrate the possible application of gene therapy for acute glomerulonephritis. A gene encoding an antiinflammatory molecule, IL-1 receptor antagonist, was delivered into inflamed glomeruli, using a technique that may allow site-specific gene delivery into inflamed tissues. The progression of experimental acute glomerulonephritis was effectively suppressed by this intervention for at least 14 days after gene introduction. This success may strengthen the rationale for gene therapy in the treatment of inflammatory diseases such as glomerulonephritis.     

Identification of plasma miR-106a-5p and miR-30a-5p as potential biomarkers for mesangial proliferative glomerulonephritis

BackgroundAlthough stable microRNAs (miRNAs) are present in human peripheral blood and have been considered as novel biomarkers for various diseases. But there is little research about miRNAs as biomarkers of mesangial proliferative glomerulonephritis (MsPGN). This study aimed to identify whether there exist disordered circulating miRNAs that can function as biomarkers for MsPGN disease activity.MethodsThe candidate miRNAs were validated in 70 MsPGN patients and 70 healthy controls by quantitative real-time PCR (RT-qPCR). The specificity and sensitivity of the miRNA panel was assessed by receiver operating characteristic (ROC) curves. In addition, the candidate miRNA levels were measured in the different MsPGN progression and in the membranous nephropathy (MN) patients and the hypothetical role of the candidate miRNA on mesangial cell proliferation was analysed. Situ hybridization was performed to examine the candidate miRNA levels in the glomerulus.ResultsThese results showed that miR-106a-5p and miR-30a-5p were highly expressed in MsPGN patients compared with healthy controls and could discriminate MsPGN from healthy controls with an area under the ROC curve (AUC) of 0.93. In addition, the two miRNAs were not only higher in moderate and severe MsPGN patients, but could distinguish MsPGN from MN. We also observed a decreased expression in MsPGN regression group after treatment. Plasma miR-106a-5p level was positively correlated with estimated glomerular filtration rate (eGFR). Furthermore, the two miRNAs were highly expressed in MsPGN glomerulus and their overexpression could prompt mesangial cell proliferation.ConclusionPlasma miR-30a-5p and miR-106a-5p can serve as novel and potential diagnostic biomarkers for MsPGN.     

Characterization of protein kinase C beta isoform activation on the gene expression of transforming growth factor-beta, extracellular matrix components, and prostanoids in the glomeruli of diabetic rats.

Induction of protein kinase C (PKC) pathway in the vascular tissues by hyperglycemia has been associated with many of the cellular changes observed in the complications of diabetes. Recently, we have reported that the use of a novel, orally effective specific inhibitor of PKC beta isoform (LY333531) normalized many of the early retinal and renal hemodynamics in rat models of diabetes. In the present study, we have characterized a spectrum of biochemical and molecular abnormalities associated with chronic changes induced by glucose or diabetes in the cultured mesangial cells and renal glomeruli that can be prevented by LY333531. Hyperglycemia increased diacylglycerol (DAG) level in cultured mesangial cells exposed to high concentrations of glucose and activated PKC alpha and beta1 isoforms in the renal glomeruli of diabetic rats. The addition of PKC beta selective inhibitor (LY333531) to cultured mesangial cells inhibited activated PKC activities by high glucose without lowering DAG levels and LY333531 given orally in diabetic rats specifically inhibited the activation of PKC beta1 isoform without decreasing PKC alpha isoform activation. Glucose-induced increases in arachidonic acid release, prostaglandin E2 production, and inhibition of Na+-K+ ATPase activities in the cultured mesangial cells were completely prevented by the addition of LY333531. Oral feeding of LY333531 prevented the increased mRNA expression of TGF-beta1 and extracellular matrix components such as fibronectin and alpha1(IV) collagen in the glomeruli of diabetic rats in parallel with inhibition of glomerular PKC activity. These results suggest that the activation of PKC, predominately the beta isoform by hyperglycemia in the mesangial cells and glomeruli can partly contribute to early renal dysfunctions by alteration of prostaglandin production and Na+-K+ ATPase activity as well as the chronic pathological changes by the overexpression of TGF-beta1 and extracellular matrix components genes.     

Renal synthesis of urokinase type-plasminogen activator, its receptor, and plasminogen activator inhibitor-1 in diabetic nephropathy in rats: modulation by angiotensin-converting-enzyme inhibitor

Plasmin is an important factor in the degradation of extracellular matrix. In the study reported here we examined the expression of plasminogen-activator inhibitor-1 (PAI-1), urokinase-type plasminogen activator (uPA), and uPA receptor (uPAR), as well as the relevance of such expression to the production of type IV collagen, a major component of extracellular matrix, in the renal tissue of rats with streptozotocin-induced diabetes. Because angiotensin II is involved in the synthesis of PAI-1 and uPA, we also examined the effect of benazepril, an angiotensin-converting-enzyme inhibitor, on the expression of PAI-1, uPA, and uPAR messenger RNAs (mRNAs) and type IV collagen protein. Rats with streptozocin-induced diabetes-some untreated and some treated with 30 mg/L benazepril-and nondiabetic control rats were sacrificed at 4, 12, or 24 weeks after induction of diabetes. We examined the expression of PAI-1, uPA, and uPAR mRNAs through the use of in situ hybridization and that of type IV collagen by means of immunohistochemical methods. In control rats, we detected weak signals for PAI-1, uPA, and uPAR mRNAs in glomeruli. Diabetic rats exhibited high levels of expression of PAI-1, uPA, and uPAR mRNAs and type IV collagen protein, mainly in mesangial cells. These mRNAs were synthesized in various renal cells (epithelial, mesangial, and endothelial cells and Bowman's capsule). Benazepril inhibited increases in all 3 mRNAs, especially in the mesangium; reduced type IV collagen expression; and attenuated mesangial expansion. Our results indicated that altered expression of PAI-1, uPA, and uPAR in diabetic nephropathy was associated with mesangial expansion and that the beneficial effects of ACE-I may be at least associated with such expression.