Transcriptomic analysis reveals partial epithelial-mesenchymal transition and inflammation as common pathogenic mechanisms in hypertensive nephrosclerosis and Type 2 diabetic nephropathy

Hypertensive nephrosclerosis (HN) and Type 2 diabetic nephropathy (T2DN) are the leading causes of chronic kidney disease (CKD). To explore shared pathogenetic mechanisms, we analyzed transcriptomes of kidney biopsies from patients with HN or T2DN. Total RNA was extracted from 10 μm whole kidney sections from patients with HN, T2DN, and normal controls (Ctrl) (n = 6 for each group) and processed for RNA sequencing. Differentially expressed (log2 fold change >1, adjusted p < 0.05) genes (DEG) and molecular pathways were analyzed, and selected results were validated by immunohistochemistry (IHC). ELISA on serum samples was performed on a related cohort consisting of patients with biopsy-proven HN (n = 13) and DN (n = 9), and a normal control group (n = 14). Cluster analysis on RNA sequencing data separated diseased and normal tissues. RNA sequencing revealed that 88% (341 out of 384) of DEG in HN were also altered in T2DN, while gene set enrichment analysis (GSEA) showed that over 90% of affected molecular pathways, including those related to inflammation, immune response, and cell-cycle regulation, were similarly impacted in both HN and T2DN samples. The increased expression of genes tied to interleukin signaling and lymphocyte activation was more pronounced in HN, while genes associated with extracellular matrix organization were more evident in T2DN. Both HN and T2DN tissues exhibited significant upregulation of genes connected with inflammatory responses, T-cell activity, and partial epithelial to mesenchymal transition (p-EMT). Immunohistochemistry (IHC) further confirmed T-cell (CD4+ and CD8+ ) infiltration in the diseased tissues. Additionally, IHC revealed heightened AXL protein expression, a key regulator of inflammation and p-EMT, in both HN and T2DN, while serum analysis indicated elevated soluble AXL levels in patients with both conditions. These findings underline the shared molecular mechanisms between HN and T2DN, hinting at the potential for common therapeutic strategies targeting both diseases.

MicroRNA-214-3p in the Kidney Contributes to the Development of Hypertension

BACKGROUND

In spite of extensive study, the mechanisms for salt sensitivity of BP in humans and rodent models remain poorly understood. Several microRNAs (miRNAs) have been associated with hypertension, but few have been shown to contribute to its development.

METHODS

We examined miRNA expression profiles in human kidney biopsy samples and rat models using small RNA deep sequencing. To inhibit an miRNA specifically in the kidney in conscious, freely moving rats, we placed indwelling catheters to allow both renal interstitial administration of a specific anti-miR and measurement of BP. A rat with heterozygous disruption of the gene encoding endothelial nitric oxide synthase (eNOS) was developed. We used bioinformatic analysis to evaluate the relationship between 283 BP-associated human single-nucleotide polymorphisms (SNPs) and 1870 human miRNA precursors, as well as other molecular and cellular methods.

RESULTS

Compared with salt-insensitive SS.13BN26 rats, Dahl salt-sensitive (SS) rats showed an upregulation of miR-214-3p, encoded by a gene in the SS.13BN26 congenic region. Kidney-specific inhibition of miR-214-3p significantly attenuated salt-induced hypertension and albuminuria in SS rats. miR-214-3p directly targeted eNOS. The effect of miR-214-3p inhibition on hypertension and albuminuria was abrogated in SS rats with heterozygous loss of eNOS. Human kidney biopsy specimens from patients with hypertension or hypertensive nephrosclerosis showed upregulation of miR-214-3p; the gene encoding miR-214-3p was one of several differentially expressed miRNA genes located in proximity to human BP-associated SNPs.

CONCLUSIONS

Renal miR-214-3p plays a functional and potentially genetic role in the development of hypertension, which might be mediated in part by targeting eNOS.

Cell adhesion molecule-1 shedding induces apoptosis of renal epithelial cells and exacerbates human nephropathies

Chronic kidney disease (CKD) is an important problem throughout the world, associated with the increase of blood urea nitrogen (BUN) and serum creatinine (sCre) and with renal tubular injuries. It is crucial to elucidate the molecular mechanisms of renal injuries to identify the new therapeutics and early diagnostic methods. We focused on cell adhesion molecule-1 (CADM1) protein. CADM1, its isoform SP4, is expressed in the epithelial cells of various tissues, including renal distal tubules, localized on the lateral cell membrane, mediates cell-cell adhesion via trans-homophilic binding, and interacts with various proteins. We previously reported that its expression was downregulated by post-proteolytic cleavage (α- and β-shedding) in pulmonary diseases. To investigate whether CADM1 α-shedding occurs in human nephropathies, we performed Western blotting and immunohistochemical analysis of specimens with arterionephrosclerosis (AS) and diabetic nephropathy (DN) from autopsied kidneys. CADM1 α-shedding was induced in AS and DN kidneys and derived from the decrease in full-length CADM1 (FL-CADM1) and increase of the COOH-terminal fragment (α-CTF). In particular, the reduced FL-CADM1 level was correlated with tubular and tubulointerstitial injuries and the increases in BUN and sCre levels. Apoptosis of renal tubular epithelial cells (TECs) was promoted in both nephropathies, and it was significantly correlated with the decrease in the FL-CADM1. Furthermore, FL-CADM1 knockdown by small interfering RNA downregulated anti-apoptotic Bcl-2 protein and promoted apoptosis of cultured renal TECs. The present study suggests that the reduction of FL-CADM1 leads to renal TEC apoptosis and could exacerbate renal tubular and tubulointerstitial injuries, which contribute to the development of CKD.

Intrarenal and Urinary Th9 and Th22 Cytokine Gene Expression in Lupus Nephritis

OBJECTIVE

We studied the urinary sediment mRNA level of Th9- and Th22-related cytokines in patients with systemic lupus erythematosus (SLE).

METHODS

We quantified urinary mRNA levels of interleukin (IL) 9, IL-10, IL-22, and their corresponding transcription factors in 73 patients with active lupus nephritis, 13 patients with hypertensive nephrosclerosis (HTN), and 25 healthy subjects.

RESULTS

There was no detectable IL-9 mRNA in all samples. Patients with proliferative lupus nephritis had significantly lower urinary IL-22 mRNA levels than those with nonproliferative nephritis (2.2 ± 5.4 vs 8.6 ± 20.0 copies, p = 0.019), and urinary IL-22 mRNA level inversely correlated with the histological activity index (r = -0.427, p < 0.0001). In contrast, patients with lupus nephritis had significantly higher urinary IL-10 mRNA levels than patients with HTN (7.8 ± 18.5 vs 1.9 ± 4.0 copies, p = 0.012), and urinary IL-10 mRNA levels correlated with its intrarenal mRNA levels (r = 0.337, p = 0.004) and SLE disease activity index (r = 0.277, p = 0.018). Urinary IL-10 mRNA level was significantly lower among patients who achieved complete remission than those with partial remission or no response (4.1 ± 6.5 vs 14.1 ± 28.0 copies, p = 0.036).

CONCLUSION

Urinary IL-22 mRNA level is decreased in patients with SLE with proliferative nephritis, while urinary IL-10 mRNA levels correlates with its intrarenal mRNA level and disease activity. Urinary IL-10 mRNA levels may also predict treatment response. These results suggest that urinary mRNA levels of IL-10 and IL-22 might be used as biomarkers for assessing disease activity and risk stratification in lupus nephritis.

[Genetic approach to hypertensive nephrosclerosis]

Several epidemiological and experimental studies suggest an important role of genetic factors in the pathogenesis of hypertensive nephrosclerosis. However, identification of susceptibility genes is difficult. The association between apolipoprotein L1 gene (APOL1) variants and non-diabetic chronic kidney disease in African Americans has modified the approach to hypertensive glomerular sclerosis, as a member of a single disease spectrum: APOL1-associated FSGS.

ADAMTS13--more than just TMA and TTP

ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type-1 motifs 13) has been shown to be of major pathophysiological importance for thrombotic microangiopathy (TMA) in the setting of thrombocytic thrombocytopenic purpura (TTP) when either lacking (inherited TTP) or if antibodies against ADAMTS13 are present (acquired TTP). A potential pathophysiological role of ADAMTS13 has also been postulated in other diseases i.e. myocardial infarction, atrial fibrillation and diabetic angiopathy. Recent data provides evidence, however, for a completely different role of ADAMTS13 in vascular physiology and pathophysiology. In the present issue of Nephrology Dialysis and Transplantation, Bockmeyer et al. documented a physiological expression of ADAMTS13 in arteriolar vascular smooth muscle cells (VSMCs) which is maintained in the early, so-called benign nephrosclerosis, i.e. under conditions of early hypertensive vascular damage, and is completely lost if the damage proceeds to late, fibrotic stages of vascular injury. Thus, the recent report identifies ADAMTS13 as a new marker for the contractile phenotype of VSMC which is maintained in the early, hyalinotic phase of vascular damage, but is lost in later, more fibrotic stages of benign nephrosclerosis. This finding adds a novel and potentially important aspect to the unsolved and underestimated problem of benign or hypertensive nephrosclerosis.

Gene polymorphism of vascular endothelial growth factor -1154 G>A is associated with hypertensive nephropathy in a Hispanic population

The aim of this study was to determine the association between hypertensive nephropathy and gene polymorphisms of vascular endothelial growth factor (VEGF) in a self-reported Hispanic patient group. A total of 155 Hispanic living kidney donors as controls and a total of 86 Hispanic kidney transplant patients, whose renal failure was attributed to hypertensive nephropathy after ruling out diabetes mellitus or other causes, were genotyped for four different single nucleotide polymorphisms of VEGF: -2578 C>A (rs699947), -1154 G>A (rs1570360), -460 C>T (rs833061), and +936 C>T (rs3025039). The homozygous mutant type (AA) of VEGF -1154 G>A (rs1570360) was found with significantly higher frequency in the hypertensive nephropathy patients than in controls. On the other hand, homozygous wild type (GG) was found less frequently in the hypertensive nephropathy patient group than in the control group. Linkage disequilibrium (LD) analyses revealed a high degree of LD among VEGF -2578 C>A (rs699947), VEGF -1154 G>A (rs1570360), and VEGF -460 C>T (rs833061). The haplotype analysis revealed that two haplotypes, CGTC and CATC (in the order of VEGF -2578 C>A (rs699947), -1154 G>A (1570360), -460 C>T (rs833061), and +936 C>T (3025039)), were significantly associated with hypertensive nephropathy in Hispanic patients. Hence, the -1154 G>A polymorphism (rs1570360) and two haplotypes (CGTC and CATC) of VEGF appear to be associated with hypertensive nephropathy in Hispanic patients who developed end-stage renal disease requiring kidney transplant.

Common charge-shift mutation Glu65Lys in K+ channel β₁-Subunit KCNMB1: pleiotropic consequences for glomerular filtration rate and progressive renal disease

BACKGROUND

Glomerular filtration rate (GFR) is a heritable trait, and hyperfiltration (GFR increment in remnant nephrons) may accelerate renal functional decline in chronic kidney disease (CKD). Mesangial and vascular smooth myocytes control GFR by contraction, dependent on voltage-gated Ca(2+) influx, which is controlled by the regulatory β₁-subunit (KCNMB1) of large-conductance heteromeric K+ ('BK') channels. KCNMB1 gain-of-function variant Glu65Lys results in generalized vasorelaxation and thus protection against systemic hypertension. Here we asked whether the Glu65Lys variant influences GFR, in the basal state or during progressive renal decline.

METHODS

We explored Glu65Lys effects on GFR in three populations spanning two ethnicities and two diseases (hypertension and nephrosclerosis). GFR was either estimated (eGFR from serum creatinine) or directly measured (iothalamate clearance).

RESULTS

The 65Lys variant was relatively common, occurring on ∼5-10% of chromosomes in different biogeographic ancestry groups, and 65Lys carriers exhibited higher eGFR in two primary care populations: extreme BP values in Kaiser clinics (p = 0.029, accounting for ∼0.2% of trait variance), or treated hypertensives in VA clinics (p = 0.017, accounting for ∼0.9% of trait variance). In blacks with progressive renal disease (NIDDK AASK), 65Lys carriers displayed a steeper slope in GFR chronic decline (p = 0.030, accounting for ∼0.4% of trait variance), and Glu65Lys genotype also predicted time of onset of renal failure (log rank p = 0.019).

CONCLUSIONS

Common KCNMB1 gain-of-function variant Glu65Lys influences GFR, and 65Lys carriers exhibit not only elevated baseline GFR, but also more rapid GFR decline (and consequent development of renal failure) in CKD. The results suggest that profiling patients at Glu65Lys can assist in gauging renal prognosis as well as selection of rational therapy in hypertension with progressive renal disease.

Progression of chronic kidney disease: Adrenergic genetic influence on glomerular filtration rate decline in hypertensive nephrosclerosis

BACKGROUND

African-Americans are likely to develop hypertension and hypertensive nephrosclerosis. This grave prognosis, coupled with familial aggregation of end-stage renal disease (ESRD) in Blacks, prompts a search for genetic risk factors for ESRD. Recent evidence implicates a crucial role for the sympathetic nervous system in progressive renal disease.

METHODS

We used the African-American Study of Kidney Disease to probe whether beta2-adrenergic receptor (ADRB2) predicts glomerular filtration rate (GFR) decline rate. A total of 580 participants were included. Baseline GFR was 51.2 +/- 0.5 ml/min/1.73 m2. Subjects were randomized in a 2 x 3 block design: to intensively lowered (MAP < or = 92 mm Hg) versus 'usual' (MAP = 102-107 mm Hg) blood pressure goal groups, and also divided by three randomized antihypertensive drugs (ramipril, metoprolol, or amlodipine). We scored 4 SNPs at the ADRB2 locus.

RESULTS

Haplotypes at ADRB2 predicted chronic GFR decline rate, GFR declined more slowly in individuals with haplotype-1 (-804G-->173T-->16Gly-->27GIn), and faster in those who carried haplotype-3 (-804G-->173T-->16Arg-->27Gln). ADRB2 genotype interacted with antihypertensive drug class to influence GFR slope (p = 0.001-0.037). We extended our findings to an independent case/control sample of Black hypertensive ESRD, in which we found that variant Gly16Arg that tagged the GFR slope-determining ADRB2 haplotype also conferred risk for the ESRD trait in Blacks.

CONCLUSIONS

The GFR decline/progression rate in hypertensive renal disease is controlled in part by genetic variation within the adrenergic pathway.

A perspective on arterionephrosclerosis: from pathology to potential pathogenesis

The morphological findings of so-called hypertensive nephrosclerosis, rather than implying a linear direct relationship to damage induced by hypertension, may indicate complex environmental and genetic factors, which together foster the coexistence of renal lesion and hypertension in this clinical setting. We discuss the clinical and pathological criteria for diagnosis of arterionephrosclerosis, and possible pathogenetic factors, including hypertension, ethnicity, aberrant autoregulation, prothrombotic mechanisms, low birth weight, decreased nephron number, genetic factors and dysmetabolic syndrome.

The clot thickens

Vascular sclerosis has been linked to many risk factors, including smoking, family history, low birth weight, and hypertension. In interesting studies, Goforth et al. show an increased rate of mutations in thrombophilic molecules in patients with vascular sclerosis in renal biopsies, suggesting yet another mechanism.

Renal vascular sclerosis is associated with inherited thrombophilias

Vascular sclerosis is often seen in renal biopsies. It is usually associated with diabetes mellitus, hypertension, smoking, etc. However, whether inherited thrombophilic states such as factor V gene mutation, prothrombin gene mutation, and methylenetetrahydrofolate reductase (MTHFR) gene mutation are associated with the vascular sclerosis is not known. Renal biopsies that showed vascular disease were grouped into five groups: (1) diabetic patients, (2) hypertensive patients, (3) diabetic and hypertensive patients, (4) smokers, and (5) vascular sclerosis of unknown etiology (idiopathic renal disease). Renal biopsies with no vascular sclerosis were used as controls. Frozen tissue was analyzed for factor V Leiden mutation, prothrombin G20210A mutation, and MTHFR C677T. Factor V Leiden mutation and prothrombin G20210A mutation was not seen in patients with diabetes, hypertension, or smoking, whereas MTHFR C677T polymorphism in these groups was not significant, compared to the controls. In the idiopathic renal disease group, three of the 17 patients (17.6%) had prothrombin G20210A mutation, two of the 17 patients (11.8%) had the factor V Leiden mutation, and five of the 17 (29.4%) were homozygous for the MTHFR C677T polymorphism. When the data were evaluated as a whole, 10 mutations were found in 17 patients (P<0.0005 compared to controls) or eight of the 17 patients (47%) were observed to have at least one of the three forms of inherited thrombophilia (P<0.001 compared to controls). These findings indicate that renal vascular lesions, in the absence of diabetes, hypertension, or smoking appears to be associated with inherited thrombophilias.

Prevention of mesangial sclerosis by bone marrow transplantation

Previously we have shown that bone marrow (BM) transplantation (BMT) can attenuate progression of and even ameliorate mesangial sclerosis (MS) in Wt1-heterozygous mice. However, it is unclear whether BMT performed before the onset of disease will prevent the development of MS. To investigate whether intravenous (i.v.) or intrarenal (i.r.) administration of BM have equal effects on the progression of MS in Wt1-heterozygous mice, young Wt1-heterozygous mice that had not yet developed renal disease were used as recipients for BMT. After preconditioning with 750 cGy radiation, mice were transplanted with one million wild-type BM via i.v. or i.r. administration. All recipients and untreated controls were assessed for urinary albumin loss, renal pathology, and BM donor-derived renal cells over time. Representative kidney samples were subjected to transmission electron microscopy (TEM) analysis. Interestingly, i.r. and i.v. administration of BM cells gave comparable hematopoietic engraftment levels, and both were able to prevent the onset of MS as assessed by improved lifespan, renal function, renal histology, and TEM analysis. Taken together, we show for the first time that MS can be prevented if BMT is performed before disease onset. Similar therapeutic effects were obtained whether the BM was administered i.v. or i.r.

Two cases of isolated diffuse mesangial sclerosis with WT1 mutations

Here we report two cases of isolated diffuse mesangial sclerosis (IDMS) with early onset end-stage renal failure. These female patients did not show abnormalities of the gonads or external genitalia. Direct sequencing of WT1 PCR products from genomic DNA identified WT1 mutations in exons 8 (366 Arg>His) and 9 (396 Asp>Tyr). These mutations have been reported previously in association with Denys-Drash syndrome (DDS) with early onset renal failure. Therefore we suggest that, at least in part, IDMS is a variant of DDS and that investigations for the WT1 mutations should be performed in IDMS patients. In cases with identified WT1 mutations, the same attention to tumor development should be required as in DDS patients, and karyotyping and serial abdominal ultrasonograms to evaluate the gonads and kidney are warranted.

Von der Molekulargenetik des Alport-Syndroms zu Prinzipien der Organprotektion bei chronischen Nierenerkrankungen

BACKGROUND

Scarring is known to be the endpoint of most chronic kidney diseases. Therefore, prevention of renal fibrosis is a very important topic. The hereditary type IV collagen disease Alport's syndrome is a rare, but challenging cause of chronic renal fibrosis.

PATHOGENESIS OF GLOMERULAR AND INTERSTITIAL RENAL FIBROSIS IN HUMANS

Increasing knowledge about the pathogenesis of Alport's syndrome may help to find principles of nephro-protection in chronic renal diseases. The defect gene in Alport's syndrome causes an altered assembly of extracellular matrix leading to a defect cell-matrix interaction and fibrosis. This scarring is regulated by comparable mechanisms as in diabetic nephropathy or chronic inflammatory renal diseases. NEPHRO-PROTECTION IN ANIMAL MODELS: By using an Alport animal model of chronic renal fibrosis, principles of nephro-protective therapies such as blockade of the renin-angiotensin system or the effect of HMG-CoA reductase inhibitors can be investigated. CURRENT AND FUTURE NEPHRO-PROTECTION IN HUMANS: The same model serves for evaluation of new organo-protective therapies such as vasopeptidase inhibitors, blockade of endothelin, chemokine and collagen receptors as well as stem cell therapy and their potential benefit for patients with chronic renal diseases.

The MTHFR 677TT and 677CT/1298AC genotypes in Cypriot patients may be predisposing to hypertensive nephrosclerosis and chronic renal failure

AIM

The homozygous 677TT mutation of the MTHFR gene has been linked to deep vein thrombosis and to arterial atherosclerotic events of the coronary, carotid and peripheral arteries. Its putative association with renal arteriosclerosis and chronic renal failure (CRF) in the presence of hypertensive nephrosclerosis is yet to be investigated.

METHODS

Two hundred and twenty-one Greek-Cypriot patients with CRF from one single renal unit in Cyprus were divided into 6 diagnostic categories: 49 due to chronic glomerulonephritis (22.2%), 43 due to diabetes mellitus (19.4%), 26 due to autosomal dominant polycystic kidney disease (11.8%), 30 due to essential hypertension leading to nephrosclerosis (13.6%), including 4 patients with primary malignant hypertension, 32 with other rarer causes of CRF (14.5%) and 41 of uncertain etiology (18.5%). These 221 CRF patients had their MTHFR C677T and A1298C genotypes analyzed by the polymerase chain reaction and agarose gel electrophoresis after restriction enzyme digestion. The frequency of the homozygous states 677TT and 1298CC and the double heterozygous 677CT/1298AC were compared to those of 210 unrelated normal local controls.

RESULTS

A statistically significant increase in the frequency of the 677TT genotype compared to controls was only found in the hypertensive nephrosclerosis CRF sub-group of patients. The prevalence rate of the 677TT genotype was 46.7% (controls 17.6%, P=0.0007). Combined together the homozygous 677TT and the double heterozygous 677CT/1298AC genotypes were found in 86.7% of the hypertensive nephrosclerotic CRF patients, compared to 46.6% in normal controls (P=0.0001).

CONCLUSIONS

The findings support the hypothesis that Caucasian patients with essential hypertension, homozygous for 677TT or doubly heterozygous for 677CT/1298AC genotypes, are predisposed to develop hypertensive nephrosclerosis and CRF.

[Pathogenesis of renal failure in hypertension. The role of genetic factors, low weight at birth and endothelial dysfunction]

Nephrosclerosis is usually diagnosed in patients with essential hypertension with no or mild proteinuria and no urinary abnormalities. Microalbuminuria is considered to be a marker of high risk for progressive renal disease in patients with diabetes mellitus but there is still no solid evidences that this alteration entails an adverse renal prognosis in essential hypertension. Independently of hypertension, nephrosclerosis is associated with endothelial dysfunction and evidence is accruing that genetic factors and a low number of nephrons at birth are important determinants of this disease.

Prostacyclin-deficient mice develop ischemic renal disorders, including nephrosclerosis and renal infarction

BACKGROUND

Prostacyclin (PGI2) is a short-lived endogenous inhibitor of platelet aggregation and a potent vasodilator and regulator of the growth of vascular smooth muscle cells. To study the role of PGI2 in the vascular system in vivo, PGI2-deficient (PGID) mice were established by genetic disruption of the PGI2 synthase gene.

METHODS AND RESULTS

PGI2 synthase-null mice were generated by replacing the exons of PGI2 synthase gene that encodes for the catalytic site of the enzyme with a neomycin resistance gene. In these mice, PGI2 levels in the plasma, kidneys, and lungs were reduced, whereas thromboxane and prostaglandin E2 levels became elevated. Blood pressure and the amounts of urea nitrogen and creatinine in plasma of the PGID mice were significantly higher than those of wild-type mice (P<0.05). They developed progressive morphological abnormalities in the kidneys, accompanied by atrophy, surface irregularity, fibrosis, cyst, arterial sclerosis, and hypertrophy of vessel walls. Thickening of the thoracic aortic media and adventitia were observed in aged PGID mice. Importantly, these phenotypes have not been reported in PGI2 receptor-deficient mice.

CONCLUSIONS

PGI2 deficiency resulted in the development of vascular disorders with the thickening of vascular walls and interstitial fibrosis, especially in mouse kidneys. The findings demonstrated in vivo that PGI2 is important in the homeostasis of blood vessels. Our established PGID mice are useful for studies on the initiation and development of vascular diseases, such as ischemic renal disorders with arterial sclerosis and infarction, and also for studies on the novel signaling pathway of PGI2.

[Nephropathy associated with arterial hypertension: genes and Barker's hypothesis]

For about three decades glomerular diseases have been the most intensively investigated research area in nephrology. The increasing proportion of patients with end-stage renal disease (ESRD) secondary to hypertension has now revived interest in hypertension. Prospective studies have firmly established that high blood pressure is associated with an increased risk of renal failure independent of other risk factors. Hypertension-related renal injury might be interpreted in a general context taking into account genes, intrauterine growth and environmental factors. Disturbed intrauterine growth (due to malnutrition or other factors) has a negative influence on the development of the cardiovascular system and favours the occurrence of hypertension, insulin resistance, hypercholesterolaemia and hyperuricaemia in adult life (Barker's hypothesis). Altered intrauterine growth has also been associated with a reduced number of nephrons at birth. Damage attributable to glomerular hyperperfusion in kidneys with a reduced number of nephrons is aggravated by vascular lesions in middle and small arterial vessels (secondary to hypertension, hyperlipidaemia and environmental risk factors such as smoking). The observation that subjects homozygous for the D allele of the ACE gene are predisposed to both cardiovascular complications and nephrosclerosis, suggests that genetic factors may interact with altered intrauterine growth in determining the risk of cardiovascular and renal diseases.

A patient with apolipoprotein E2 variant (Q187E) without lipoprotein glomerulopathy

Four apolipoprotein (apo) E variants have been reported to be associated with lipoprotein glomerulopathy (LPG), which is characterized by type III hyperlipoproteinemia (type III HLP) and proteinuria and frequently leads to nephrotic syndrome. We report the histologic findings in the kidneys of a type III HLP patient with an apo E variant, apo E Toranomon, in which the glutamine at residue 187 in apo E is substituted by glutamic acid (Q187E). The patient also had type 2 diabetes mellitus. No evidence of lipoprotein thrombi suggestive of LPG was detected, however, and the histologic diagnosis was diabetic nephrosclerosis. This unique case illustrates that not all apo E variants result in LPG, and the location of mutations in the apo E protein is one of the important determinants for the development of LPG.

Mechanisms in nephrosclerosis and hypertension-beyond hemodynamics

These studies support that global glomerulosclerosis is a key lesion in human hypertensive nephrosclerosis, and cannot be simply explained by worse vascular sclerosis caused by higher blood pressure. Possible pathogenetic mechanisms include genetic susceptibility, accelerated aging and a primary microvascular disease. The potential importance of the renin angiotensin system in glomerular sclerosis is underscored by the effectiveness of therapies that aim to inhibit its manifold actions, including induction of plasminogen activator inhibitor-1 (PAI-1). Further, regression of existing glomerulosclerosis, including age-related renal and vascular sclerosis, can be achieved in various experimental settings by high dose angiotensin inhibiton, and is linked to inhibition of PAI-1. Ongoing studies will establish which of these provocative findings from animal models are relevant to human diseases, and may lead to optimal therapies to forestall progression and perhaps even induce regression of sclerosis.

Inaccuracy of clinical phenotyping parameters for hypertensive nephrosclerosis

BACKGROUND

Multiple studies suggest that hypertension-induced end-stage renal disease (ESRD) is heritable. Identification of nephropathy susceptibility genes absolutely requires accurate phenotyping, but the clinical hypertensive nephrosclerosis (HN) phenotype is poorly characterized. We hypothesized that many patients with HN as the indicated cause of ESRD on the Health Care Financing Administration (HCFA) 2728 form, fail to satisfy stringent HN phenotyping criteria.

METHODS

Since renal biopsy documentation of HN is uncommon, clinical parameters for HN phenotype were applied: family history of hypertension, left ventricular hypertrophy, proteinuria <0.5 g/day, and hypertension preceding renal dysfunction (Schlessinger et al., 1994) or urine protein:creatinine (prot:creat) ratio <2.0 and no evidence of other renal diseases (AASK Trial Group, 1997).

RESULTS

ESRD patients (n=607, 73% African American, 25% Caucasian) were enrolled in a study to identify HN susceptibility genes. HN was the most common cause of ESRD according to HCFA 2728 forms (37% prevalence). Phenotyping of randomly selected patients with HN from the total cohort revealed that 4/100 subjects satisfied the Schlessinger criteria, and 28/91 African Americans met AASK criteria for HN. From these figures, the adjusted prevalence of HN was only 1.5-13.5%. Of patients that could not be phenotyped for HN, 14 were misdiagnosed, 14 had urine prot:creat >2.0, and insufficient data were available in the remainder. Four patients underwent renal biopsy, but histology from only one was consistent with HN. If the HN phenotype definitions are revised to exclude 'hypertension preceding renal dysfunction', or proteinuria limits, then 44/100 and 39/91 patients respectively satisfy clinical phenotyping parameters for HN.

CONCLUSIONS

(i) We provide the strongest evidence to date that HN is less frequent in an ESRD population than commonly assumed if strict clinical criteria are used; many patients clinically diagnosed with HN may have undetected, treatable renal disease from other causes; (ii) relaxing HN phenotype criteria may erroneously include patients with glomerular diseases and secondary hypertension; (iii) reliance on HCFA 2728 diagnoses will confound identification of HN susceptibility genes; (iv) to attain adequate statistical power for genotype analysis, rigorous HN phenotyping will require screening an extremely large number of patients, which can be reasonably accomplished only in a multi-centre trial design.

The deletion polymorphism of the angiotensin-converting enzyme is associated with nephroangiosclerosis

The D allele of the angiotensin-converting enzyme (ACE) gene has been linked with diabetic nephropathy and IgA glomerulonephritis and with faster renal disease progression. The association of this allele with nephroangiosclerosis has been scarcely investigated. We have tested this association in 45 hypertensive patients (all whites) with well defined nephroangiosclerosis (diagnosis established on the basis of renal biopsy in all cases) and moderate to severe renal failure. As studies of genetic association of small size often produce conflicting results, besides a control group of 343 Italian patients with essential hypertension and normal renal function, we elected to use also a very large control group of race-matched subjects taken from a meta-analysis of 27,565 whites. The proportion of patients with the D allele (64%) was higher in patients with nephroangiosclerosis than that in Italian hypertensives (54%) and in whites (54%). DD and DI genotypes were more prevalent in patients than in control groups. The dominant model (DD and DI v II: nephroangiosclerosis v Italian controls: chi2 = 6.19, P = .012; nephroangiosclerosis v whites chi2 = 6.86, P = .009) fitted the data better than the codominant and the recessive model (P < or = .022). The D allele is associated with nephroangiosclerosis with a dominant effect in the sample of patients studied. Although intervention studies are needed to see whether these findings imply a causal association, our data suggest that this allele may at least act as disease marker in nephroangiosclerosis.

Angiotensin converting enzyme gene I/D polymorphism in essential hypertension and nephroangiosclerosis

An insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene significantly influences circulating ACE levels and plays a role in the development of target organ damage, that is, left ventricular hypertrophy in essential hypertension (EH), and microalbuminuria in diabetes mellitus. We have examined the role of the I/D polymorphism in essential hypertensive patients with renal involvement. The study was divided in two independent protocols. In protocol 1, we retrospectively analyzed the ACE genotypes in 37 essential hypertensive patients with a clinical and histopathological diagnosis of nephroangiosclerosis. In protocol 2, ACE genotypes as well as microalbuminuria and renal hemodynamic parameters were investigated in 75 patients with EH with normal renal function and a strong family history of hypertension. As control group, 75 healthy subjects with BP < 130/85 mm Hg and no family history of cardiovascular diseases were studied. The ACE variants were determined by PCR and the genotypes were classified as DD, DI and II. In protocol 1, patients with nephroangiosclerosis displayed a significant difference in the genotype distribution (57% DD, 27% DI, 16% II) when compared to the control population (25% DD, 64% DI, 11% II; P < 0.001). There was no significant difference in genotype distribution between hypertensive patients with normal renal function (protocol 2; 33% DD, 59% DI, 8% II) and the control group. There were no differences in age, blood pressure, microalbuminuria and duration of the disease among the three genotypes in the EH group from protocol 2. Taken together, these findings suggest that the DD genotype of ACE is associated with histopathologic-proven kidney involvement in patients with EH and that this polymorphism could be a potential genetic marker in hypertensives at risk of renal complications.

Genetic susceptibility to hypertension-induced renal damage in the rat. Evidence based on kidney-specific genome transfer

To test the hypothesis that genetic factors can determine susceptibility to hypertension-induced renal damage, we derived an experimental animal model in which two genetically different yet histocompatible kidneys are chronically and simultaneously exposed to the same blood pressure profile and metabolic environment within the same host. Kidneys from normotensive Brown Norway rats were transplanted into unilaterally nephrectomized spontaneously hypertensive rats (SHR-RT1.N strain) that harbor the major histocompatibility complex of the Brown Norway strain. 25 d after the induction of severe hypertension with deoxycorticosterone acetate and salt, proteinuria, impaired glomerular filtration rate, and extensive vascular and glomerular injury were observed in the Brown Norway donor kidneys, but not in the SHR-RT1.N kidneys. Control experiments demonstrated that the strain differences in kidney damage could not be attributed to effects of transplantation-induced renal injury, immunologic rejection phenomena, or preexisting strain differences in blood pressure. These studies (a) demonstrate that the kidney of the normotensive Brown Norway rat is inherently much more susceptible to hypertension-induced damage than is the kidney of the spontaneously hypertensive rat, and (b) establish the feasibility of using organ-specific genome transplants to map genes expressed in the kidney that determine susceptibility to hypertension-induced renal injury in the rat.

Does keloid pathogenesis hold the key to understanding black/white differences in hypertension severity?

Repeated national surveys have shown that in the United States hypertension is more common and more severe in the black than in the white population. This discussion presents the hypothesis that the racial difference in hypertension severity is because of differences in growth factors (cytokines) affecting vascular smooth muscle cell growth. This hypothesis is derived from studies of keloids, which occur almost exclusively in blacks. Keloid fibroblasts in culture have growth characteristics that differ substantially from those of normal skin. Furthermore, there is evidence that peripheral blood mononuclear cells from patients with keloids produce different amounts of cytokines than do similar preparations from the blood of individuals without keloids. A growing body of evidence indicates that growth factors play a pivotal role in the pathogenesis of atherosclerosis, in experimental forms of hypertension, and in various renal diseases; it may be that they function in clinical hypertension as well.

Transforming growth factor-beta 1 expression and phenotypic modulation in the kidney of hypertensive rats

We have previously reported that renal mRNA levels for transforming growth factor-beta 1, fibronectin, and collagens were increased in 32-week-old stroke-prone spontaneously hypertensive rats (SHRSP) with severe nephrosclerosis. To elucidate the mechanism of hypertension-induced nephrosclerosis, we examined gene expression and localization of transforming growth factor-beta 1 and cellular phenotype in the kidney of 25-week-old SHRSP with moderate renal damage. Renal mRNA was measured by Northern blot analysis. The localization of transforming growth factor-beta 1 and cellular phenotype was determined by immunohistochemistry. In the kidney of 25-week-old SHRSP, renal transforming growth factor-beta 1 mRNA was elevated compared with Wistar-Kyoto rats (WKY), whereas renal collagen mRNAs of SHRSP were not increased. Immunoreactive transforming growth factor-beta 1 in SHRSP was mainly localized in glomerular cells. Furthermore, alpha-smooth muscle actin and desmin were significantly expressed in SHRSP glomerular cells, in contrast to negligible expression of these proteins in WKY. alpha-Smooth muscle actin staining was also observed in interstitial cells, and vimentin, another phenotypic marker, was expressed in atrophic tubular cells of SHRSP, despite no staining of these proteins in WKY. Furthermore, all these phenotypic changes in SHRSP were associated with increased cell proliferation, as shown by the increased number of proliferating cell nuclear antigen-positive cells. Treatment of SHRSP with cilazapril and nifedipine (from the age of 13 to 25 weeks) prevented the increase in transforming growth factor-beta 1 expression and the cellular phenotypic modulation and was accompanied by a reduction of urinary albumin excretion and inhibition of cell proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

The link between hypertension and nephrosclerosis

Nephrosclerosis is literally defined as hardening of the kidneys (Greek derivation: nephros, kidney; sklerosis, hardening). It is the result of scarring or replacement of the normal renal parenchyma by dense collagenous tissue. In practice, nephrosclerosis refers to diseases with predominant pathologic changes occurring in the preglomerular microvasculature and secondarily involving the glomeruli and interstitium. The relationship between mild to moderate hypertension and either nephrosclerosis or end-stage renal disease (ESRD) remains circumstantial, although these syndromes have long been associated in the medical literature. Nephrologists credit hypertension as the etiology of nephrosclerosis in 25% of patients initiating Medicare-supported renal replacement therapy, even though other processes may cause similar renal pathologic findings. Strikingly, serum creatinine values infrequently increase in patients with long-standing mild to moderate hypertension. Patients classified as having hypertensive ESRD typically present with advanced disease, making the processes that initiated the renal disease difficult to detect. Nephrologists are twice as likely to label an African-American patient as having hypertensive nephrosclerosis, compared with a white patient, when presented with identical clinical histories. This review proposes that many patients classified as having hypertensive nephrosclerosis actually have intrinsic renal parenchymal diseases, renal artery stenosis, unrecognized episodes of accelerated hypertension, or a primary renal microvascular disease. The familial clustering of ESRD attributed to hypertension in African-Americans and the identification of genes associated with renal injury in animals support the concept that inherited factors may predispose to renal failure. African-American families often have members with ESRD from disparate etiologies, including hypertensive ESRD. This suggests that common mechanisms, be they inherited or environmental, underlie the development of progressive renal failure in diverse forms of nephropathy. Identification of the mechanisms producing susceptibility to progressive renal disease would support the concept that mild to moderate elevations in blood pressure per se are uncommon causes of nephrosclerosis.

The Denys-Drash syndrome

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Glomerular expression of type III and type IV collagens in benign nephrosclerosis: immunohistochemical and in situ hybridization study

The development of glomerular sclerosis in benign nephrosclerosis (BNS) was studied. We investigated the intraglomerular expression of type III and IV collagens and their mRNAs by immunohistochemistry and by the in situ hybridization method. Formalin-fixed paraffin sections from 28 patients with BNS and 10 control cases were stained by the avidin-biotin complex (ABC) method using monoclonal antibodies for human type III and IV collagens. In the course of the sclerotic process of the glomerulus in BNS, the glomerular staining intensity of type IV collagen increased. The strongest staining was observed in the glomerulus at the early sclerotic stage, and intensity decreased slightly at the later stages. Although type III collagen was absent in normal and nonsclerotic glomeruli, peripheral regions of the sclerotic glomeruli were positive at the early sclerotic stage. Later, type III collagen was diffusely observed in the completely hyalinized glomeruli. The expression of type III and type IV collagen mRNAs was detected in the glomeruli of BNS by the non-radioactive in situ hybridization method using thymine-thymine (T-T) dimerized synthetic oligonucleotides. The number of mRNA positive cells for type III and type IV collagens increased at the presclerotic and early sclerotic stages. But these cells gradually decreased in number as glomerular sclerosis developed. We concluded that type III collagen was presumably synthesized by the intraglomerular cells and may contribute to the development of glomerular sclerosis in BNS along with type IV collagen.

Spontaneous hypertension in the fawn-hooded rat: a cardiovascular disease model

The fawn-hooded (FH) rat develops hypertension spontaneously. Systolic blood pressure is already elevated at 5 weeks of age, increases with age, and the final range is 180-240 mmHg at the age of 1 year. Concomitantly with the rise in blood pressure proteinuria occurs and increases with age. Fawn-hooded rats reaching the accelerated phase of the hypertension are characterized by blood pressure values exceeding 220 mmHg, heavy proteinuria and increased heart, kidney, liver, adrenal and spleen weights. Those prone to malignant hypertensive disease show a period of increased water turnover for several weeks after weaning; during this period, they do not show the pronounced decrease in water intake upon fasting for 24 h as observed in FH rats of the same age prone to a milder form of hypertension, i.e. diuresis and drinking continue even when no food is consumed. The major cause of death for FH rats is malignant nephrosclerosis with the nephrotic syndrome and/or cardiac failure with chronic pulmonary congestion. Some animals die of bleeding from mesenteric vessels with periarteritis nodosa. In FH rats with malignant hypertension, heart, kidney, liver and spleen weights are significantly increased compared with FH rats of the same age with mild hypertension. Histopathology shows myocardial fibrosis and myocardial infarctions. Generalized arteriolosclerosis is common, sometimes accompanied with local fibrinoid degeneration and (peri)arteritis. Some major arteries show intimal proliferation. It is concluded that the FH rat provides an interesting model for the study of hypertension and its consequences.