Influence of VEGF polymorphism on progression of autosomal dominant polycystic kidney disease.

BACKGROUND: Significant phenotypical variability is observed in autosomal dominant polycystic kidney disease (ADPKD). Dysregulation of vascular endothelial growth factor (VEGF) expression in the kidney has been demonstrated in a wide range of renal diseases. The aim of the present study was to assess the influence of the -2578 C/A and the -1154 G/A polymorphisms in the regulatory region of the VEGF gene upon the progression of ADPKD toward end-stage renal disease (ESRD). METHODS: The study was performed on 283 ADPKD patients (145 males, 138 females, mean age 51.7 +/- 10.3 years) who had reached ESRD. Patients were divided into three groups: (1) ESRD development later than in 63 years (slow progressors, n = 47), (2) ESRD development before 45 years (rapid progressors, n = 69), and (3) ESRD development between 45 and 63 years (intermediate progressors, n = 167). Genetically unrelated healthy Czech individuals were analyzed as a control group (n = 311, 153 males, 158 females, mean age 44.6 +/- 9.2 years). DNA samples were genotyped for the -2578 C/A and for the -1154 G/A polymorphisms of the VEGF gene promoter. The serum levels of VEGF were established in 111 healthy Czech individuals from the control group. RESULTS: The VEGF -2578 C/A and -1154 G/A genotype distribution showed no differences among the groups of slow, rapid and intermediate progressors. The age of ESRD with regard to different genotypes was not significantly different in all ADPKD patients. However, the AA genotype of the -2578 C/A polymorphism was associated with a significantly higher age of ESRD than other genotypes in rapid progressors (42.7 vs. 40.5 years, p = 0.01). The CG haplotype was found significantly more frequent in ADPKD rapid progressors than in slow progressors (p = 0.047). Serum levels of VEGF did not significantly differ in the control group, according to different genotypes of both polymorphisms. CONCLUSION: To conclude, AA genotype of the -2578 C/A polymorphism was related to better prognosis of the disease in a limited group of ADPKD patients. Classical genetic recessive and dominant model did not find significant influence of separate VEGF polymorphisms on the progression of ADPKD. Accordingly, CG haplotype was associated with earlier onset of ESRD in ADPKD patients.

The influence of two megsin polymorphisms on the progression of IgA nephropathy.

The clinical course of chronic renal diseases and their progression to ESRD is highly variable. The strongest predictors of poor outcome of IgAN involve hypertension, severe proteinuria and elevated serum creatinine level. Different candidate gene polymorphisms have been advocated as possible modulators of the progression of IgAN. Megsin belongs to the serpin superfamily and was mapped to chromosome 18q21.3. Megsin plays a role in the regulation of a wide variety of processes in mesangial cells, such as matrix metabolism, cell proliferation, and apoptosis. Overexpression of Megsin might lead to mesangial dysfunction, and impair degradation of the mesangial matrix and disposal of immune complexes. The expression of Megsin is upregulated in a variety of glomerular diseases with mesangial injury in humans and in animal models. We investigated a possible association of two C2093T, C2180T polymorphisms of the megsin gene with the progression of IgAN towards ESRD, as well as the haplotype reconstruction of megsin gene polymorphisms and clinical manifestation of IgAN. We examined a group of 197 pts with histologically proven IGAN (84 pts with normal renal function, 113 pts with progressive renal insufficiency); as a control group we used 61 genetically unrelated healthy subjects. DNA samples from collected blood were genotyped for two singlenucleotide polymorphisms of megsin C2093T, C2180T by means of PCR with defined primers, electrophoresis on 2% agarose gel, UV light visualization and direct sequencing. The megsin genotype distribution showed no differences among the groups of IgAN with normal renal function, progressive renal insufficiency and the control group. According to haplotype analysis, the TT haplotype (defined as T-2093, T-2180 alleles) was substantially more frequent in pts with IgAN and normal renal function (Table 1, P = 0.025; Table 3, P = 0.062). Pts in the progressive group showed significantly higher levels of 24-h UP (3.53 +/- 2.80 vs 2.06 +/- 2.06, P = 0.042; Table 10), diastolic blood pressure (92.89 +/- 15.66 vs 84.93 +/- 10.43, P = 0.047; Table 10) and almost significantly systolic blood pressure (150.79 +/- 32.88 vs 135.21 +/- 14.88, P = 0.058; Table 10). We confirmed the negative prognostic influence of hypertension and proteinuria on the progression of IgAN in Czech pts. We found out that the TT haplotype (defined as T-2093, T-2180 alleles) could play a protective role in the progression of IgAN. In our Czech population, we excluded the negative influence of the 2093C-2180T haplotype, which was proposed by Chinese studies.

The influence of endothelin-A receptor gene polymorphism on the progression of autosomal dominant polycystic kidney disease and IgA nephropathy.

ADPKD is the most common hereditary renal disease. IGAN is a mesangial proliferative glomerulonephritis characterized by diffuse mesangial deposition of immunoglobulin A. ET-1 has been suggested to be a major disease-promoting factor in renal diseases. The vasoconstrictor effect of ET-1 is mediated by the ET-A receptor. We have investigated the influence of C/T polymorphism in exon 8 of the EDNRA gene. A total number of 193 patients (87 males, 106 females) with ADPKD entered into this study. Patients were divided into three groups: 1. 47 pts with ESRD later than in 63 years (slow progressors), 2. 49 pts with ESRD before 45 (rapid progressors) and 3. 97 pts with ESRD between 45-63 years. Moreover, we examined a group of 153 pts with histologically proven IGAN (116 males, 37 females). Pts were divided into two groups: 1. 79 pts with ERSD during 5 years of the study (IGAN rapid progressors) and 2. 74 patients with normal renal function (IGAN slow progressors). As a control group we used 100 genetically unrelated healthy subjects. The distribution of C/T polymorphism did not significantly differ between rapid and slow progressors of ADPKD and IGAN. The comparison of ESRD ages showed that CC females with ADPKD failed significantly later than CT heterozygotes: CC (57.4 +/- 8.1 years), CT (53.0 +/- 9.1 years) and TT (54.5 +/- 6.4years) (t-test, P = 0.018). To conclude, the CC genotype could be protective in ADPKD females. This genotype was described to be associated with lower pulse pressure.

The influence of three endothelin-1 polymorphisms on the progression of IgA nephropathy.

The clinical course of chronic renal diseases and their progression to ESRF is highly variable. Different candidate gene polymorphisms have been advocated as possible modulators of ESRF progression. Moreover, ET-1 has been suggested as a major promoting factor in renal disease. However, limited data are available regarding an association of three ET-1 SNP K198N, T- 1370G and 3A/4A with the progression of IgAN to ESRF. We examined a group of 122 pts with histologically proved IgAN (91 pts with normal renal function, 31 pts with ESRF), as a control group we used 132 genetically unrelated healthy subjects. Patients' DNAs were genotyped for three ET-1 SNP: K198N, T-1370G and 3A/4A by means of PCR. The frequencies of different genotypes and ET-1 gene haplotypes were compared among control group, IgAN pts with normal renal function and IgAN pts with ESRF. The ET-1 genotype distribution showed no differences among the groups of IgAN with normal renal function (1. K198N - 63.74% KK, 32.97% KN, 3.3% NN; 2. TT - 68.13% TT, 28.57% TG, 3.3% GG; 3. 3A/4A - 42.22% 3A/3A, 50.0% 3A/4A, 7.69% 4A/4A ), IgAN with ESRF (1. K198N - 74.19% KK, 25.81% KN, 0% NN; 2. TT - 77.42% TT, 22.58% TG, 0% GG, 3. 3A/4A - 56.25% 3A/3A, 37.5% 3A/4A, 6.25% 4A/4A ) and the control group (1. K198N - 66.67% KK, 31.82% KN, 1.52% NN, 2. TT - 76.51% TT, 22.72% TG, 0.76% GG, 3. 3A/4A - 43.94% 3A/3A, 44.70% 3A/4A, 11.36% 4A/4A ). The analysis of haplotypes showed that the frequency of G-198, G-1370 and 4A allele combination was significantly higher in comparison with the control group (P=0.0056). We excluded the effect of K198N, T-1370G and 3A/4A polymorphisms of the ET-1 gene in single-gene analysis on the progression of IgAN to ESRF. A significant association of the GG4A haplotype with IgAN, demonstrated by haplotype reconstruction of the ET-1 gene, could suggest a role in the pathogenesis of IgAN.

The pathogenetic aspects and gene polymorphisms of IgA nephropathy.

Immunoglobulin A nephropathy is an immune-complex-mediated glomerulonephritis characterized by diffuse mesangial deposition of immunoglobulin A or IgA--containing immune complexes. Although its most common clinical presentation is macroscopic hematuria provoked by upper respiratory tract infection, this is neither universal nor necessary for the diagnosis. The patients with IgA nephropathy manifest with variable clinical symptoms (e.g., microhematuria with preserved renal function or progressive deterioration of renal functions resulting in end-stage renal disease). The pathogenetic mechanisms include the abnormality of O-glycosylation of the IgA1 molecule, genetic factors, environmental factors and various inflammatory mediators. The source of mesangial IgA deposits is total circulating serum IgA but the response of the mesangium and the mesangial cells to the deposited IgA is critical to the development of IgAN. Without a genetic predisposition to IgAN, IgA deposition can cause no risk for triggering glomerulonephritis. If generic progression risk factors of an unfavourable outcome coincide (e.g. hypertension, severe proteinuria, elevated serum creatinine level), this will increase the likelihood of progressive renal impairment. Further studies are needed to disclose the precise pathogenetic mechanisms involved in primary IgA nephropathy and to facilitate the development of newer therapeutic possibilities.

Genetic basis of nephrotic syndrome--review.

Nephrotic syndrome (NS) is one of the most frequent syndromes characterized namely by heavy proteinuria. Majority of NS occurs as a sporadic form, the incidence of familial cases is from 3 to 5%. Seven genes have been recognized till present, which mutations are responsible for severe forms of NS: NPHS1, NPHS2, ACTN4, CD2AP and WT1, TRPC6, LAMB2. Proteins encoded by these genes (nephrin, podocin, alpha-actinin-4, an adapter protein anchoring CD2 and others) influence the function of the podocytes. In cases of mutation in NPHS1 gene, causing congenital nephrotic syndrome of the Finnish type (CNF), resistance to steroid therapy occurs regularly and recurrence of proteinuria after renal transplantation is about 20-25%. Mutations in NPHS2 gene lead to autosomal recessive steroid resistant nephrotic syndrome (histologically focal segmental glomerulosclerosis). It was concluded that patients with steroid resistant nephrotic syndrome (SRNS) with homozygous or compound heterozygous mutations in NPHS2 have reduced risk for recurrence of focal segmental glomerulosclerosis (FSGS) in renal transplant (only 8% in comparison with 35% in patients without mutation in NPHS2). A functional polymorphism of NPHS2 gene--R229Q was associated with a late-onset nephrotic syndrome and also with an increased risk of microalbuminuria in the general population. The R229Q variant encodes a protein with lower affinity for binding nephrin. This polymorphism appears to enhance susceptibility to FSGS in association with a second mutant NPHS2 allele. There are also 3 genetic loci connected with autosomal dominant forms of FSGS: ACTN4, TRPC6 and CD2AP (found only in the mice models). These forms of FSGS differ from the recessive form by later-onset and more slowly progressive course of the disease; these mutations seem to be responsible for only a fraction of the autosomal dominant pattern of FSGS.

Does electron microscopy change the view of the diagnosis of IgA nephropathy?

Our study is aimed to reveal the frequency and clinical significance of the coincidence of two widely spread entities, e.g. minimal change disease (MCD) and IgA nephropathy (IgAN), claimed to be found in an overwhelming number in some Asian regions. We retrospectively analyzed clinical and histological data from 627 renal biopsies, performed in our department from January 2002 to January 2005 and completed electron microscopy in 112 specimens diagnosed as IgAN. The coincidence of IgAN and MCD was found in 8 patients (7.1%). The coincidence of IgAN and minimal change nephrotic syndrome (MCNS) clinically--especially presence of nephrotic syndrome and the response to drug therapy (with corticosteroids)--behaves as "pure" MCN. Our data from Czech Republic seem to suggest that the combination of IgAN with MCNS can be found relatively frequently not only in Asian patients (as stressed by some authors of Asian origin) but also in European inhabitants. The pathogenesis of the coincidence of IgAN and MCD needs to be elucidated by further studies.