Long-term course of post-transplant mesangial IgA deposition: clinicopathologic study of nine cases

Abstract:  We conducted the present study to elucidate the fate of post-transplant mesangial IgA deposit under the long-term observation. Out of a total of 45 cases with post-transplant mesangial IgA deposition, nine cases with more than 4 yr of follow-up term were enrolled in this study, and clinicopathologic characteristics were described. The study included three men and six women with a mean age of 34.2 yr. The average observation time from the detection of mesangial IgA deposition was 6.1 yr. Three cases were categorized as recurrent IgA nephropathy, while six cases were classified into latent mesangial IgA deposition. One case with hypertension developed end-stage renal disease. The significant improvement in microscopic hematuria was observed in one recurrent IgA nephropathy case. Microscopic findings included mild mesangial stalk thickening in all but one case. IgA deposition demonstrated a significant decrease in three latent mesangial IgA deposition cases. No apparent reduction in dense deposit quantity was observed on electron microscopy. There was no association between clinicopathologic findings and the regimen of anti-immunosuppressive agents. This study showed the improvement of the disease activity did occur in both recurrent IgA nephropathy and latent mesangial IgA deposition. Further investigation of latent mesangial IgA deposition may present the important clue to the pathogenesis of IgA nephropathy.     

Interleukin-12 alters the physicochemical characteristics of serum and glomerular IgA and modifies glycosylation in a ddY mouse strain having high IgA levels.

BACKGROUND: We recently developed a ddY mouse strain having high IgA levels (HIGA) that provided a murine model of IgA nephropathy. We additionally showed that administration of interleukin (IL)-12, a potent helper T (Th)1-inducing cytokine, induced an apparent reduction in serum IgA levels. In the present study, we assessed the influence of IL-12 administration on several physicochemical characteristics of nephritogenic IgA molecules in HIGA mice. METHODS: HIGA mice received daily intraperitoneal injections of IL-12 or control injections of phosphate-buffered saline for 3 weeks. Crescent formation and levels of circulating and glomerular IgA were analysed. Moreover, potential changes in charge, size, and glycosylation of serum and glomerular IgA were investigated. RESULTS: In the IL-12 group, glomerular IgA deposition was faint, although crescent formation was more marked than in the control group. Serum IgA levels in IL-12 mice were significantly lower than in controls. IL-12-treated mice also showed markedly decreased acidic and polymeric IgA both in sera and in glomerular eluate. A lectin-binding study revealed a markedly reduced ratio of sialylated and galactosylated IgA in the sera and in glomerular eluate from HIGA mice kidneys. IL-12 treatment significantly increased sialylation and galactosylation of circulating IgA, although glycosylation of IgA in glomerular eluate remained low. CONCLUSIONS: In HIGA mice showing under-glycosylation, IL-12 administration may lead to changes in the physicochemical characteristics of IgA, and this may occur through a shift to Th1. These results suggest that the Th1 and Th2 balance might play a role in the development of immunopathologic lesions in this model of IgA nephropathy.     

An increased polymeric IgA level is not a prognostic marker for progressive IgA nephropathy.

BACKGROUND: Elution of IgA from renal biopsies of patients with primary IgA nephropathy (IgAN) has suggested that mesangial IgA deposits are mainly multimeric in nature. This macromolecular IgA consists of dimeric and polymeric IgA and may be derived from the circulation. In children with IgAN, circulating macromolecular IgA levels correlate with bouts of macroscopic haematuria, but in adults a correlation with disease activity is less clear. Therefore, we have designed a novel method to assess the levels of polymeric IgA (pIgA) in sera from patients and controls. METHODS: A novel precipitation assay using recombinant CD89 was developed to measure pIgA. Polymeric IgA levels were measured in serum samples obtained from healthy volunteers (n = 21) and patients with IgAN (n = 51). Subsequently, serum pIgA levels were correlated with clinical parameters of disease. RESULTS: Serum pIgA levels were significantly increased in patients with IgAN. However, pIgA concentrations relative to total IgA were significantly lower in sera of patients with IgAN. No correlation was found between serum pIgA levels and clinical parameters of IgAN, such as decline of glomerular filtration rate, haematuria or proteinuria. CONCLUSIONS: Although absolute levels of serum pIgA are increased in patients with IgAN as compared with controls, levels of pIgA relative to total serum IgA are lower. No significant correlation was found between serum concentrations of pIgA and clinical parameters of disease. These data support the notion that it is not the size alone, but the physicochemical composition of the macromolecular IgA that is the key factor leading to mesangial deposition.     

Expression of mesangial IgA nephropathy in a family with several HLA-dentical members

SUMMARY: The familial incidence of mesangial IgA nephropathy (IgAN) is well recognized. However, the genetic implications of this finding remain uncertain. We report a family of East Timorese origin where six out of eight members, including the mother and five first-degree offspring, have had histologically proven mesangial IgAN. All eight members have undergone HLA A, B, C and DR typing as well as determination of C4 allotype. Among the offspring, there are HLA-identical male twins (A11,-; B13,15; Cw3,-; DR2,3) and three HLA-identical females (A11,-; B13,27; Cw3,-; DR2,3). Their C4 allotype is also identical (i.e. A3; B1,2,96 and A3; B1,96, respectively). There were histological and biochemical differences between the twins: subject ii-2 showed focal mesangial proliferation on light microscopy and a 24 h urine protein excretion of 1–2 g on presentation while subject ii-3 was normal at that time. the latter subsequently underwent a renal biopsy 15 years later and this showed changes only on immunofluorescence microscopy. There were major differences in expression of renal disease among the HLA-identical sisters: two developed end-stage renal failure (ESRF) by the age of 30 years, while the third retains normal renal function after 15 years follow-up. the angiotensin converting enzyme (ACE) genotype was examined for insertion (I)/deletion (D) polymorphism; this showed that both patients with severe renal disease had the ID genotype and this was also present in the two unaffected female members. the study shows no relationship between the HLA A, B, C, DR, C4 supratype and progress of renal disease in this family with mesangial IgAN. Moreover, no association could be demonstrated between progress and the ACE genotype, although the number of patients involved was small. the data suggest that environmental factors and/or genetic/environmental interaction influence the severity of renal injury.     

Cerivastatin inhibits fetal calf serunvinduced DNA synthesis in cultured rat mesangial cells

SUMMARY: Inhibition of mevalonate synthesis by several statins has been shown to suppress DNA synthesis in glomerular mesangial cells. In the present study, we investigated the effect of a new statin, cerivastatin, on fetal calf serum (FCS)-induced DNA synthesis of cultured rat mesangial cells. Cultured rat mesangial cells were stimulated by 10% FCS in the presence or absence of cerivastatin and mevalonate. 5-bromo-2-deoxyuridine (BrdU) incorporation was used to assess DNA synthesis. the present study showed that 10% FCS caused marked stimulation of DNA synthesis in the mesangial cells. Cerivastatin inhibited FCS-stimulated BrdU incorporation in a dose-dependent manner. IC₅₀ was approximately 1 umol/L. Exogenous mevalonate, farnesyl pyrophosphate and geranylgeranyl pyrophosphate significantly prevented the inhibitory effect of cerivastatin on DNA replication. It appears that cerivastatin, by inhibiting the synthesis of mevalonate, may suppress DNA synthesis in the mesangial cells.     

Inhibitory effects of rosmarinic acid on the proliferation of cultured murine mesangial cells.

BACKGROUND: Rosmarinic acid is a phenolic compound widely distributed in Labiatae herbs such as rosemary, sweet basil, and perilla, which are frequently used with meat and fish dishes in Western and Asian countries. In the present study we investigated the effects of rosmarinic acid on cultured murine mesangial cell proliferation. METHODS: Cultured murine mesangial cells were stimulated by growth factors with or without rosmarinic acid, and [(3)H]thymidine incorporation was measured in regard both to signal transduction and to cell cycle dependency. In other experiments, mRNA extracted from the cells was analysed by Northern blotting. RESULTS: Rosmarinic acid inhibited the cell proliferation induced by platelet-derived growth factor (PDGF) (P<0.01; IC(50) values, 1.4 microg/ml) or tumour necrosis factor-alpha (P<0.01; IC(50) values, 3. 8 microg/ml), and these effects involved both the G(0)/G(1) and G(1)/S phases of the cell cycle. Rosmarinic acid also suppressed the mRNA expressions of PDGF and c-myc in PDGF-stimulated mesangial cells. CONCLUSIONS: Rosmarinic acid inhibits cytokine-induced mesangial cell proliferation and suppresses PDGF and c-myc mRNA expression in PDGF-stimulated mesangial cells. Rosmarinic acid in Labiatae herbs might be a promising agent to prevent mesangial cell proliferation.     

Polymeric IgA increases the synthesis of macrophage migration inhibitory factor by human mesangial cells in IgA nephropathy.

BACKGROUND: It has been suggested that polymeric IgA (pIgA) or IgA immune complexes play a significant pathogenic role in IgA nephropathy (IgAN). Macrophage migration inhibitory factor (MIF) shares many activities with other pro-inflammatory cytokines. In human glomerulonephritis, including IgAN, glomerular expression of MIF is found to correlate with progressive renal injury. We hypothesized that deposition of pIgA within the kidney may lead to enhanced synthesis of MIF by mesangial cells. METHODS: In this study we examined the effect of pIgA and monomeric IgA (mIgA) from randomly selected patients with IgAN in clinical quiescence on the gene expression and protein synthesis of MIF in cultured human mesangial cells (HMC). RESULTS: Both pIgA and mIgA from IgAN patients or matched healthy controls increased MIF gene expression and protein synthesis in a dose-dependent fashion. The magnitude of MIF protein induction by pIgA (100 microg/ml) was similar to that of tumour necrosis factor-alpha (TNF-alpha) at 10 pg/ml. In all subjects, the induction of MIF was higher for pIgA when compared with mIgA (P < 0.01). Furthermore, the up-regulation of MIF synthesis by either pIgA or mIgA was significantly higher in IgAN patients than in healthy controls (P < 0.05). Similarly, pIgA and mIgA were able to induce TNF-alpha gene expression and protein synthesis in mesangial cells. Incubation of mesangial cells with neutralizing antibody to TNF-alpha reduced the MIF synthesis induced by pIgA. CONCLUSION: We demonstrate that pIgA is capable of inducing MIF and TNF-alpha production in HMC, which may play a major pathogenic role in IgAN. Induction of MIF can be partially blocked by neutralizing antibody to TNF-alpha, suggesting the possibility that up-regulation of MIF synthesis in HMC is mediated via an amplifying proinflammatory loop involving TNF-alpha.     

Assessment of the effect of mesangial hypercellularity in childhood nephropathies to the clinical and laboratory findings

Aim: To assess the relationship between mesangial hypercellularity in various childhood nephropathies and clinical and laboratory parameters. Methods and patients: The reports of the renal biopsies were evaluated retrospectively. The patients with diagnosis of IgA nephropathy (isolated and Henoch–Schönlein nephritis), IgM nephropathy, or isolated mesangial proliferative glomerulonephritis were included. Each nephropathy group was divided into two subgroups according to the severity of mesangial hypercellularity as mild and severe. The biochemical data and histopathological findings of the patients were recorded. Results: When the groups were compared, it was found that the patients with IgA nephropathy had hematuria (p?=?0.043) and the patients with IgM nephropathy had nephrotic syndrome more frequently than the other patients (p?=?0.01). No difference was detected between the groups regarding the severity of mesangial hypercellularity. On the other hand, when the groups were evaluated within themselves, no significant association was detected between the severity of mesangial hypercellularity and clinical and laboratory parameters. It was determined that the renal biopsy was performed earlier in patients with Henoch–Schönlein nephritis compared to the other cases (p?=?0.004). Compared to the isolated IgA nephropathy group, it was found that the number of cases with severe mesangial hypercellularity was higher and the level of proteinuria was more prominent in patients with Henoch–Schönlein nephritis. Additionally, when the patients with Henoch–Schönlein nephritis were evaluated, the degree of proteinuria was found to be higher in patients with severe mesangial hypercellularity compared to those of showing mild mesangial hypercellularity (p?=?0.002). Conclusion: It was observed that there is no direct relation between the severity of mesangial hypercellularity and clinical and laboratory findings in various childhood nephropathies. However, when Henoch–Schönlein nephritis is compared with IgA nephropathy, it was found that the severity of mesangial hypercellularity was higher in cases with Henoch–Schönlein nephritis and the level of proteinuria was more prominent in those cases. However, no difference was detected in glomerular filtration rates and biochemical data with regard to the level of mesangial hypercellularity.     

Pathogenic role of the IgA molecule in IgA nephropathy

SUMMARY: Deposits of IgA together with complement in different body tissues support the hypothesis that IgA can trigger inflammatory mechanisms. IgA nephropathy (IgAN) is characterized by predominant mesangial IgA₁ deposits of a polymeric nature. So far, the mechanism of polymeric IgA₁ deposition in the kidney mesangium is poorly understood in IgAN. the exact pathophysiological sequel preceding renal fibrosis following the mesangial deposition of IgA immune complexes remains speculative. Recent in vitro studies revealed that binding of IgA to mesangial cells led to increased expression of growth factors, cytokines, and integrins. the release of these proinflammatory factors is likely to enhance inflammatory injury. In addition, the local renin-angiotensin system present in renal tissues also contributes to renal fibrosis through the activation of transforming growth factor-β. the question of whether polymeric IgA isolated from patients with IgAN exerted any upregulatory effect on the synthesis of macrophage migration inhibitory factor (MIF) and components of the renin-angiotensin system in human mesangial cells was explored. the in vitro studies revealed that polymeric IgA from IgAN patients upregulated the gene expression of renin and MIF in human mesangial cells in a dose-dependent manner. These findings further support the notion that glomerular deposition of IgA is not only a pathological epiphenomenon of IgAN, but that polymeric IgA exerts a pathophysiologic effect on the mesangial cells leading to renal fibrosis.     

Sequential measurement of mesangial matrix area occupying the glomerulus in children with IgA nephropathy

Background IgA nephropathy is the most common form of primary glomerulonephropathy in children it has a variable clinical course, from spontaneous remission to progression to renal death. It has been reported that predominant mesangial hypercellularity is characteristic of early lesions, and that it changes to a gradual matricial increase, with sclerosis, according to the disease progression. Methods A sequential measurement of the ratio of mesangial matrix area to glomerular area (M/G) was done in 5 children with moderately proteinuric IgA nephropathy, who underwent 3 consecutive, repeat renal biopsies. A prompt initiation of alternate-day prednisolone therapy (an initial dosage at 1 mg/kg, maximum 60 mg) after the first renal biopsy was done in 4 cases. The remaining patient received this therapy after the second renal biopsy. Results A sequential measurement of the M/G in the former cases did not show an increase between the biopsies, while measurement of the latter one showed a progressive increase. Moreover, the case that had an increase in the M/G showed renal impairment at the third biopsy. Conclusion Although a small number of cases were examined, a sequential measurement of the M/G in children with moderately proteinuric IgA nephropathy may be a valuable indicator for a more precise evaluation of clinical outcome in a clinical setting.     

Semiquantitative measurement of total extracellular matrix protein produced by cultured mesangial cells

SUMMARY: To evaluate the effect of several cytokines on the total production of insoluble ECM, we performed immunoperoxidase staining directly on rat mesangial cells cultured on flat-bottomed 96-well plates. the peroxidase activity was demonstrated by orthophenilenediamine (OPD) and measured directly as optic density at 490 nm (OD490) by a microplate reader. After this procedure, cell number in each well was determined by crystal violet staining of which intensity was measured at 540 nm (OD540). the amount of ECM measured as OD490 was corrected by OD540 (OD490/OD540). OD540 was linearly correlated with actual cell number in the well and OD490 for each ECM was firmly correlated with cell number in the well. By this method, dose dependent decrease of fibronectin (FN) and laminin (LM) was observed in the presence of rat recombinant interferon gamma (IFNγ). Human recombinant platelet derived growth factor (PDGF) increased the total production of LM and type IV collagen (Col IV) as well as cell number. This method would also be useful in evaluation for other proteins of insoluble form as well as ECM produced by attached form of cultured cells.     

Oxidation of low-density lipoproteins by rat mesangial cells and the interaction of oxidized low-density lipoproteins with rat mesangial cells in vitro

Glomerulosclerosis and atherosclerosis share common pathobiologicalmechanisms. Experiments carried out in vitro over the past decadeusing cells thought to be involved in the atherosclerotic processsuch as endothelial cells, smooth muscle cells, and monocyte/macrophageshave shown that postsecretory modifications such as oxidationincrease the atherogenicity of LDL. Animal experiments employingantioxidant therapy have also been shown to slow the progressionof atherosclerotic lesions. We set out to investigate the interactionsbetween oxidized LDL (oxLDL) and rat mesangial cells (RMC) thatmight be of importance in the glomerulosclerotic process. Ourresults show that RMC have the ability to oxidize LDL, thatoxLDL binding was 2–3-fold greater than native LDL (nLDL),and that oxLDL was more cytotoxic to these cells than nLDL.We speculate that cell-mediated oxidation of LDL in vivo mayplay a role in the progression of the glomerulosclerotic process.     

Synthesis of immunoglobulins against Haemophilus parainfluenzae by tonsillar lymphocytes from patients with IgA nephropathy.

BACKGROUND: We previously demonstrated glomerular deposition of Haemophilus parainfluenzae (HP) antigens and the presence of IgA antibody against HP antigens in patients with IgA nephropathy (IgAN). In this report we examine the synthesis of immunoglobulins against HP antigens in tonsillar lymphocytes from patients with IgAN. METHODS: We used tonsillar lymphocytes isolated from the palatine tonsils of 15 patients with IgAN and 16 patients with chronic tonsillitis but without renal disease. We examined lymphocyte proliferation and production of IgA, IgG, and IgM antibodies against HP antigens by measuring thymidine uptake and concentrations of these antibodies in culture supernatants after lymphocyte incubation with HP antigens by ELISA. RESULTS: Lymphocytes from patients with IgAN showed a significantly higher stimulation index (SI) on exposure to HP antigens (thymidine incorporation in tonsillar lymphocytes exposed to HP (c.p.m.)/ thymidine incorporation in unstimulated tonsillar lymphocytes (c.p.m.)) than did controls (P=0. 0015). Lymphocytes from patients with IgAN also showed a significantly higher IgA SI (concentrations of IgA against HP antigens in supernatants from HP-stimulated lymphocytes/IgA against HP antigens in supernatants from unstimulated tonsillar lymphocytes) than did controls (P=0.0004). We found positive correlations between concentrations of IgA and IgG antibodies, between IgA and IgM antibodies, and between IgG and IgM antibodies against HP antigens after HP stimulation. CONCLUSIONS: Our results suggest that HP antigens stimulate tonsillar T and B lymphocytes in patients with IgAN and that these patients have polyclonal activation of lymphocytes against HP antigens, with isotype switching of antibody production from IgM to IgA.     

Discrepant effects of vasoconstrictors on the growth of early passaged cultured rat mesangial cells

Summary: Mesangial cell growth stimulation by endothelin (ET) and arginine vasopressin (AVP) has been reported, but only in studies using late (3 times) pasaged cells. In the present study, we examined the effects of ET, AVP and platelet activating factor (PAF) on the proliferation of early (<3 times) passaged cultured rat mesangial cells which maintained their original characteristics. Cell growth was estimated by [³H]-thymidine incorporation into DNA and by counting cell nuclei. After 48 h preincubation in minimal essential medium containing 0.5% fetal calf serum, ET-1 (1-100 nmol/L), AVP (100 pmol/L-1 μmol/L) or PAF (1–100 nmol/L) was added to the incubation medium. In contrast to studies using late passaged cells, ET-1 attenuated and AVP did not increase thymidine uptake (ET-1: 18.4% inhibition at 10 nmol/L) or cell counts in early passaged cells, while the growth stimulatory effects of these agents were reproduced in late passaged cells. Platelet activating factor showed definite stimulation of cell growth in both early and late passaged cells in a dose-dependent manner. These data strongly suggest that ET-1 attenuates, and AVP does not stimulate, the cell growth of original mesangial cells. the PAF-induced cell growth seems to be the constant feature of mesangial cells in vivo.