Comparative nephritogenicity of two monoclonal antibodies that recognize different epitopes of rat Thy-1.1 molecule

Quantitative characterization of glomerular fibrosis with magnetic resonance imaging: a feasibility study in a rat glomerulonephritis model

Glomerular fibrosis occurs in the early stages of multiple renal diseases, including hypertensive and diabetic nephropathy. Conventional assessment of glomerular fibrosis relies on kidney biopsy, which is invasive and does not reflect physiological aspects such as blood perfusion. In this study, we sought to assess potential changes of cortical perfusion and microstructure at different degrees of glomerular fibrosis using magnetic resonance imaging (MRI). A rat model of glomerular fibrosis was induced by injecting anti-Thy-1 monoclonal antibody OX-7 to promote mesangial extracellular matrix proliferation. For six rats on day 5 and five rats on day 12 after the induction, we measured renal cortical perfusion and spin-spin relaxation time (T₂) in a 3-Tesla MRI scanner. T₂ reflects tissue microstructural changes. Glomerular fibrosis severity was evaluated by histological analysis and proteinuria. Four rats without fibrosis were included as controls. In the control rats, the periodic acid-Schiff (PAS)-positive area was 22 ± 1% of total glomerular tuft, which increased significantly to 56 ± 12% and 45 ± 10% in the day 5 and day 12 fibrotic groups, respectively ( P < 0.01). For the three groups (control, day 5, and day 12 after OX-7 injection), cortical perfusion was 7.27 ± 2.54, 3.78 ± 2.17, and 3.32 ± 2.62 ml·min^-1·g^-1, respectively, decreasing with fibrosis severity ( P < 0.01), and cortical T₂ was 75.2 ± 4.6, 84.1 ± 3.0, and 87.9 ± 5.6 ms, respectively ( P < 0.01). In conclusion, extracellular matrix proliferation in glomerular mesangial cells severely diminished blood flow through the glomeruli and also altered cortical microstructure to increase cortical T₂. The MRI-measured parameters are proven to be sensitive markers for characterizing glomerular fibrosis.

Possible role for glomerular-derived angiotensinogen in nephrotic syndrome

Background and objective:

Renin–angiotensin system (RAS) inhibitors reduce glomerular injury and proteinuria, indicating that angiotensin II (Ang II) is involved in glomerular diseases. Although the local RAS is reported to play an essential role in maintaining local tissue functions, the role of the local RAS in regulating glomerular function is not well evaluated. In this study, we analyzed the glomerular expression of RAS components in nephrotic models and the effect of Ang II receptor blockers (ARB) on the expression of angiotensinogen (AGT).

Methods:

The levels of glomerular expression of RAS components were analyzed in two nephrotic models: anti-nephrin antibody-induced nephropathy and PAN nephropathy, a mimic of human minimal change nephrotic syndrome. The effect of the ARB irbesartan on the expression of AGT in the nephrotic model was analyzed.

Results:

Glomerular expression of AGT and the receptors for Ang II was clearly increased in the nephrotic models, while the expression levels of renin, ACE and ACE2 were decreased. ARB treatment suppressed the increase of glomerular expression of AGT in the nephrotic model.

Conclusion:

It is conceivable that the promoted local RAS action participated in the glomerular dysfunction, and that ARB treatment ameliorated slit diaphragm injury by inhibiting the positive feedback loop of the activated local Ang II action.

Exploring the mechanisms of renoprotection against progressive glomerulosclerosis

In this review, I introduce the strategy developed by our laboratory to explore the mechanisms of renoprotection against progressive glomerulosclerosis leading to renal death. First, I describe the experimental rat model in which disturbances of vascular regeneration and glomerular hemodynamics lead to irreversible glomerulosclerosis. Second, I discuss the possible mechanisms determining the progression of glomerulosclerosis and introduce a new imaging system based on intravital confocal laser scanning microscopy. Third, I provide an in-depth review of the regulatory glomerular hemodynamics at the cellular and molecular levels while focusing on the pivotal role of Ca(2+)-dependent gap junctional intercellular communication in coordinating the behavior of mesangial cells. Last, I show that local delivery of renoprotective agents, in combination with diagnostic imaging of the renal microvasculature, allows the evaluation of the therapeutic effects of angiotensin II receptor and cyclooxygenase activity local blockade on the progression of glomerulosclerosis, which would otherwise lead to renal death.

Bone marrow cell infusion ameliorates progressive glomerulosclerosis in an experimental rat model

Bone marrow (BM) cells contribute to the maintenance and repair of several compartments of the kidney, including the endothelium, interstitium, epithelium, and the mesangium. The aim of this study was to explore the therapeutic use of bone marrow-derived cells (BMDC) that can differentiate into endothelial and mesangial cells in a model of progressive glomerulosclerosis. To investigate the involvement of BMDC in glomerular repair, progressive glomerulosclerosis was induced in enhanced green fluorescent protein BM chimeric rats by a one-shot injection of anti-Thy-1.1 monoclonal antibody, followed by unilateral nephrectomy. Subsequently, these rats were treated with either a BM cell infusion or phosphate-buffered saline. Renal function, intravital glomerular hemodynamics, and histological alterations were examined 12 weeks after anti-Thy-1.1 monoclonal antibody injection. Inflammatory infiltration of macrophages in the kidneys was evaluated by immunofluorescence of ED-1. We also determined whether BMDC contributed to repair and regeneration of endothelial and mesangial cells by immunofluorescence monitoring. As a result, BM cell infusion improved renal function and glomerular hemodynamics, and histological alterations with reduced glomerular infiltration of macrophages, leading to dramatically reduced mortality in this model of progressive glomerulosclerosis. We also demonstrated that, in the BM cell infusion group, more BMDC contributed to repair and regeneration of endothelial and mesangial cells than in the untreated group. The present study provides us with a conceptual basis for the development of therapeutic stem cell strategies aimed at enhancing recovery from progressive glomerulosclerosis.

Exogenous 5'-nucleotidase improves glomerular autoregulation in Thy-1 nephritic rats

Experiments were performed to characterize renal hemodynamics in Thy-1 nephritic rats. A monoclonal antibody against Thy-1 was intravenously injected to induce mesangiolysis in rats, and 2 days later renal hemodynamic responses to variations in blood pressure were determined. In the first series of experiments, autoregulation of renal plasma flow (RPF) or glomerular filtration rate (GFR) was impaired in nephritic rats. In response to a reduction in blood pressure (98 +/- 2 to 80 +/- 1 mmHg), both RPF (4.17 +/- 0.63 to 3.20 +/- 0.45 ml x min(-1) x g kidney wt(-1), P < 0.05, n = 6) and GFR (0.88 +/- 0.05 to 0.75 +/- 0.06 ml x min(-1).g kidney wt(-1), P < 0.05) were decreased in nephritic rats. Intravenous administration of furosemide and 30% albumin, both of which inhibit tubuloglomerular feedback, diminished renal autoregulation in control but not nephritic rats. In the second studies, the infusion of 5'-nucleotidase, an enzyme expressed on mesangial cells, into a renal artery ameliorated the magnitude of autoregulatory decrements in GFR in nephritic rats (-16 +/- 5 to -6 +/- 2%, P < 0.05, n = 6), but this enzyme failed to alter renal autoregulation in control rats. In the third studies, the effects of indomethacin were examined in nephritic rats. Inhibition of prostaglandin synthesis reduced RPF (4.07 +/- 0.30 to 1.54 +/- 0.22 ml x min(-1) x g kidney wt(-1), P < 0.05, n = 5) and GFR (1.03 +/- 0.18 to 0.69 +/- 0.13 ml x min(-1) x g kidney wt(-1), P < 0.05) in nephritic rats. However, cyclooxygenase inhibition failed to restore renal autoregulation in nephritic rats. Our results indicate that renal autoregulation is impaired in Thy-1 nephritis. Furthermore, the present data provide evidence that prostanoids contribute to maintain renal circulation in nephritic rats. Finally, our findings suggest that mesangial cells and/or 5'-nucleotidase plays an important role in mediating renal autoregulation.

Bone marrow cells contribute to regeneration of damaged glomerular endothelial cells

BACKGROUND

There is accumulating evidence that adult bone marrow (BM) cells show unexpected plasticity, and can differentiate into a wide range of specialized cells. In the case of intrinsic renal glomerular cells, BM-derived cells have been reported to differentiate into both mesangial cells and podocytes. However, there is controversy on recruitment of glomerular endothelial cells, although endothelial cells in other tissues are known to be recruited from the BM.

METHODS

Sprague-Dawley (SD) rats and SD rats made chimeric by transplantation of bone marrow cells from enhanced green fluorescent protein (EGFP) transgenic littermate rats, were injected with anti-Thy-1.1 antibody, followed by unilateral nephrectomy (1-kidney model). Chimeric rats used in 1-kidney model were sacrificed for histologic examination at weeks 2, 4, 8, and 11. We examined isolated glomeruli and frozen sections of kidneys from rats of each group at weeks 2 and 11 by confocal laser scan microsopy (CLSM), both immunohistologically and three dimensionally.

RESULTS

In the 1-kidney group, using chimeric rats transplanted with EGFP(+) bone marrow cells, most rats died, presumably of uremia, after 8 to 11 weeks. A CLSM study using isolated glomeruli and frozen sections of kidneys revealed that bone marrow-derived PECAM-1(+), RECA-1(+) cells, and OX-7(+) cells contributed to the structural support for the glomerular capillaries during the chronic course. Global glomerular sclerotic lesions and diffuse tubular atrophic changes, with interstitial cell infiltration, were remarkable at weeks 8 and 11.

CONCLUSION

Bone marrow-derived endothelial progenitor cells participated in glomerular endothelial cell turnover after severe damage. Treatment that could target bone marrow-derived endothelial progenitor cells and promote angiogenesis in regions of progressive glomerular lesions may be a promising therapeutic approach for preventing end-stage renal disease.

Distribution and excretion of a phosphorothioate oligonucleotide in rats with experimentally induced renal injury

The effects of renal injury on the urinary excretion and tissue distribution of a 20-mer phosphorothioate oligonucleotide were investigated in male Sprague-Dawley rats. Renal injury was produced by treating the rats with either 5.0 mg/kg cisplatin or 2.5 mg/kg of a monoclonal antibody (mAb) directed toward Thy1.1. Controls received saline. Three days after cisplatin treatment or 2 days after anti- Thy1.1 treatment, the rats received 10 mg/kg ISIS 3521. Blood was collected at various times to assess the plasma concentrations of ISIS 3521, and rats were killed at various times from 6 to 48 hours after intravenous (i.v.) infusion of oligonucleotide to assess tissue concentrations by capillary gel electrophoresis (CGE). Cisplatin and anti-Thy1.1 antibody produced histologic and biochemical changes consistent with proximal tubular damage and glomerular damage, respectively. Urinary excretion of oligonucleotides was increased 2- to 4-fold of control; however, this amount accounted for only 1% to 2% of dose compared to 0.5% in controls. Proximal tubular damage reduced renal accumulations of ISIS 3521 and other oligonucleotide metabolites, but there were no obvious compensatory increases in concentrations in other organs except for a slight increase in spleen levels of total oligonucleotide. Glomerular damage was not associated with any change in oligonucleotide disposition. Immunohistochemical studies showed no evidence of alterations in the pattern of distribution within the injured kidney. The data suggest that acute renal dysfunction, either renal tubular or glomerular, does not markedly alter the urinary elimination and tissue deposition of a phosphorothioate oligonucleotide.

Mycophenolate mofetil and roscovitine decrease cyclin expression and increase p27(kip1) expression in anti Thy1 mesangial proliferative nephritis

The response of mesangial cells to a phlogistic challenge includes cell proliferation and mesangial matrix expansion. Cell proliferation is a highly regulated process which includes enhancing factors such as cyclins, cyclin dependent kinases, and inhibitory proteins, such as p27(kip1). The aim of the study was to evaluate the effects of Mycophenolate mofetil (MMF), and roscovitine (R), on the cell cycle regulatory system when administered in the florid phase of the experimental model of mesangial proliferative nephritis induced by the anti Thy-1 antigen monoclonal antibody. Three days after nephritis induction, different groups were given MMF and R. Rats treated with MMF or R showed a slight decrease in mesangial proliferation and matrix expansion. Samples of cortical tissue were tested by 'real time' RT-PCR in order to study gene expression of cyclins B, D1, D2, D3, E, and the cyclin inhibitor p27(kip1). Localization of mRNA was evaluated by in situ hybridization. Real time RT-PCR analysis showed a significant decrease in cyclins B, D1, D2, and D3 in rats treated with either MMF or R as compared to controls. Both MMF and R treatment induced a significant increase in p27(kip1) mRNA expression. In situ hybridization showed a mesangial-endothelial expression pattern in glomeruli. The number of labelled cells per glomerulus, the number of positive glomeruli in each examined slide as well as cyclin D2 and D3 signal intensity was significantly lower in rats treated with MMF or R as compared to controls, whereas MMF or R treatment up-regulated p27(kip1) mRNA expression. Immunohistochemical evaluation of p27(kip1) aimed to examine the influence of MMF or R on protein expression confirmed up-regulation.

The characterization of a specific Thy-1 molecular epitope expressed on rat mesangial cells

BACKGROUND

An Experimental model of proliferative glomerulonephritis induced by an antibody against Thy-1 antigen has been established. However, the pathophysiologic role and the critical epitope of Thy-1 molecule for induction of mesangial cell dysfunction remain unknown. We have reported that monoclonal antibody 1-22-3 recognizes specific epitope which could transduce highly effective activation in mesangial cells. Identification of functional domains on cell surfaces is indispensable for understanding the molecular mechanisms of mesangial cell function. This study was undertaken to determine the functional domain containing the specific epitope recognized by monoclonal antibody 1-22-3.

METHODS

A series of glutathione-S-transferase (GST)-truncated-Thy-1 proteins were generated using pGEX 4T-1 vector. COS cells were transiently transfected with plasmid vectors which could express the rat Thy-1 and mutant-Thy-1.

RESULTS

Western blot analysis using recombinant GST-truncated-Thy-1 revealed that 1-22-3 bound to epitope at amino acids 15-23 (LRLDCRHEN). Enzyme-linked immunosorbent assay (ELISA) revealed that synthetic LRLDCRHEN peptides could inhibit the binding of 1-22-3 to rat mesangial cells and GST-Thy-1 protein. Using peptides as antigens, ELISA showed that 1-22-3 bound to the LRLDCRHEN but not to the RVNLFSDRF, which was corresponding to at amino acids 59-67 of rat Thy-1. 1-22-3 could bind the COS cells which express rat Thy-1 proteins, but could not bind rat truncated-Thy-1 which lacks residues 15-23.

CONCLUSION

Critical epitope detected by 1-22-3 in this study may play an important role in mesangial function and injury.

Neuron-binding human monoclonal antibodies support central nervous system neurite extension

Two human IgMs (sHIgM12 and sHIgM42) were identified that supported in vitro central nervous system (CNS) neurite extension equal to the potent neurite stimulatory molecule laminin. Both IgMs bound to multiple cell types in unfixed CNS tissue and to the surface of neurons in culture. Both monoclonal antibodies (mAbs) overrode the inhibitory effect of CNS mouse myelin on granule cell neurite extension. Neither mAb bound to the surface of mature oligodendrocytes or strictly colocalized with myelin proteins. Sialidase treatment eliminated the neuronal surface binding of both mAbs, whereas blocking sphingolipid synthesis with Fumonisin B1 or removing GPI-linked proteins with PIPLC did not. When used as substrates for mixed neuron/glia aggregates, sHIgM12 and sHIgM42 supported robust neurite extension while astrocytes remained in the aggregates. In contrast, laminin supported astrocyte migration and spreading. Human mAbs that support neurite extension are novel factors that may be of use in encouraging axon repair following injury while minimizing glial cell infiltration. Both human mAbs were isolated from individuals with monoclonal gammopathy. Each individual has carried high mAb titers in circulation for years without detriment. sHIgM12 and sHIgM42 are therefore unlikely to be systemically pathogenic.

Retinoic acid receptor alpha and retinoid X receptor specific agonists reduce renal injury in established chronic glomerulonephritis of the rat

Retinoids, derivatives of vitamin A, inhibit mesangial cell proliferation, glomerular inflammation, and extracellular matrix deposition in acute anti-Thy1.1 glomerulonephritis (Thy-GN) of the rat. We examined a model, chronic mesangioproliferative Thy-GN (MoAb 1-22-3), which is more akin to human disease. Treatment started on day 23 when Thy-GN had already been established. Nonnephritic control and Thy-GN rats were treated orally for 67 days with vehicle or with two doses of either the retinoic acid receptor alpha-specific agonist AGN 195183 (RARalpha agonist) or the retinoid X receptor specific agonist AGN 194204 (RXR agonist). Doses of either the RARalpha or the RXR agonist significantly reduced albuminuria and normalized blood pressure during the course of treatment. The glomerulosclerosis index, glomerular cell and interstitial cell counts, and area of the interstitial space were significantly lower in nephritic rats treated with the RARalpha agonist or RXR agonist than with vehicle. The RARalpha and RXR agonist significantly reduced the infiltration of the glomerulus by macrophages. The increase in glomerular TGFbeta1 and prepro-ET(1) gene expression in vehicle-treated nephritic rats was significantly attenuated by RARalpha or RXR agonists. Glomerular expression of RXRalpha and RARalpha receptor mRNA was significantly greater in vehicle-treated nephritic rats than in nonnephritic controls. Treatment with RARalpha or RXR agonists tended to normalize retinoid-receptor gene expression. Our data indicate that both RARalpha agonists and RXR agonists reduce renal damage in rats with established chronic glomerulonephritis. Receptor-specific retinoids may provide a novel therapeutic approach for the treatment of chronic glomerulonephritis.

Fractalkine expression and the recruitment of CX3CR1+ cells in the prolonged mesangial proliferative glomerulonephritis

BACKGROUND

We established the reversible and the prolonged models of mesangial proliferative glomerulonephritis (GN) with anti-Thy 1 antibody 1-22-3. However, the essential factors leading to the prolonged glomerular alterations have not been identified.

METHODS

The expressions of several chemokines and cytokines were compared in the reversible and the prolonged models. Expression of fractalkine and the number of the fractalkine receptor CX3CR1-positive cells in the glomeruli in the prolonged model were significantly higher than those in the reversible model. Then, the localization of fractalkine and the characteristics of CX3CR1+ cells were analyzed in glomeruli. To elucidate the significance of the fractalkine expression, we analyzed the expression in the model treated with angiotensin II receptor antagonist, candesartan.

RESULTS

Immunostaining of fractalkine was detected on endothelial cells on the fifth day, and fractalkine staining also was detected in the mesangial area on day 14. Major parts of the CX3CR1+ cells in the glomeruli were macrophages, especially ED3+ cells. Candesartan treatment ameliorated the glomerular morphological findings at six weeks after disease induction. Although the treatment did not ameliorate the morphological finding at two weeks, decreased expression of fractalkine and CX3CR1+ were already detected at two weeks in rats treated with candesartan.

CONCLUSIONS

Fractalkine expression and the recruitment of CX3CR1+ cells in glomeruli might play an important role in the development of the prolonged disease. These expressions could be predictors of the prolonged disease of the mesangial proliferative glomerulonephritis.

FK506 ameliorates proteinuria and glomerular lesions induced by anti-Thy 1.1 monoclonal antibody 1-22-3

BACKGROUND

We have previously reported that CD4 T lymphocytes and their cytokines contribute to development of Thy 1.1 glomerulonephritis (GN). FK506 is reported to suppress the production of Th1 cytokines. The aims of this study were to elucidate the role of Th1 cytokines on mesangial alteration and to examine whether FK506 is available for therapy of mesangial proliferative GN.

METHODS

The effects of daily treatments of FK506 from day -5 and from day +1 of Thy 1.1 GN induction on glomerular alterations were analyzed.

RESULTS

FK506 treatment with 1.0 and 0.3 mg/kg body weight (BW) daily from day 1 to day 4 significantly reduced the glomerular expression of mRNA for interferon-gamma (IFN-gamma; 1.0 mg/kg BW FK506, 32.4% to the placebo group, P < 0.01) and IL-2 (55.6%, P < 0.01) on day 5. FK506 treatment from day -5 of GN induction reduced proteinuria and glomerular alteration in a dose-dependent manner. Although no side effects were detected in rats with 0.3 mg/kg BW of FK506 treatment from day +1, the treatment also ameliorated proteinuria (day 14, 3.7 +/- 0.89 vs. 19.8 +/- 12.3 mg/100 g BW/day P < 0.05) and glomerular alterations [total cell number, 63.1 +/- 3.1 vs. 80.2 +/- 7.4, P < 0.01; matrix expansion, 0.90 +/- 0.30 vs. 1.34 +/- 0.27, P < 0.05; alpha-smooth muscle actin (alphaSMA) expression; 1.20 +/- 0.12 vs. 1.96 +/- 0.29, P < 0.01] on day 14.

CONCLUSION

Th1 cytokines may play an important role in the development of mesangial proliferative glomerulonephritis, and could be targets for therapy. FK506 might be available for clinical use.

Retinoid receptor-specific agonists alleviate experimental glomerulonephritis

Retinoids are potent antiproliferative and anti-inflammatory compounds. We previously demonstrated that the natural pan-agonists all-trans retinoic acid (RA) and 13-cis RA efficiently preserve renal structure and function in rat mesangioproliferative glomerulonephritis. We examine effects of synthetic retinoid receptor-specific agonists 1) to identify common and receptor subtype-specific pathways in this model and 2) to characterize effects of retinoids on the renal endothelin (ET) system. Vehicle-injected control rats were compared with rats treated with daily subcutaneous injections of agonists specific for retinoid A (Ro-137410) and retinoid X (Ro-257386) receptors and the complex anti-activator protein-1 active retinoid BMS-453 7 days after induction of anti-Thy1.1 nephritis (n = 7-9/group). The different retinoids lowered glomerular ET-1 and ET type A and B receptor gene expression in control and nephritic rats with comparable efficacy. Reduction of glomerular c-Fos and GATA-2 mRNA expression levels suggests downregulation of transcription factors required for ET expression. The different retinoids were similar in their action on the glomerular capillary occlusion score, number of total glomerular cells, and glomerular infiltrating macrophage count. They differed in their ability to normalize blood pressure (Ro-257386 > BMS-453 > arotinoid), albuminuria (BMS-453 > Ro-257386 > arotinoid), and creatinine clearance (arotinoid > BMS-453 > Ro-257386). No signs of toxicity were observed. We conclude that all retinoid agonists with different subtype specificity are highly efficient in reducing renal damage and proliferation of mesangial cells. Retinoid X and A receptor-specific pathways are apparently involved in the antiproliferative, anti-inflammatory, and anti-ET action. Further studies are indicated to define the potential use of retinoid agonists in inflammatory renal disease.

Impairment of vascular regeneration precedes progressive glomerulosclerosis in anti-Thy 1 glomerulonephritis

BACKGROUND

It has been proposed that glomerular hemodynamic changes or glomerular growth response may promote the development of glomerulosclerosis, irrespective of its etiology. Further experimental models are needed to clarify the cellular and molecular mechanisms that lead to progressive glomerulosclerosis with an irreversible course. We designed a model of irreversible glomerulosclerosis, using anti-Thy-1.1 injection followed by uninephrectomy, and examined the role of glomerular endothelial cell responses in the process of progressive sclerotic changes.

METHOD

Rats were injected with anti-Thy-1.1 monoclonal antibody, 1-22-3, and 30 minutes later, unilateral nephrectomy (one-kidney group) or sham operation (two-kidney group) was performed. Rats were sacrificed for histological examination on days 3, 14, 56, and 84 after injection. The density of the glomerular capillary tuft was assessed by immunofluorescent staining for endothelial specific antigens. The mRNA expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), platelet-endothelial cell adhesion molecule-1 (PECAM-1), and vascular endothelial growth factor (VEGF) also was followed up by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Semiquantitative analysis revealed that the capillary density and mRNA expression of PECAM-1, VCAM-1 and VEGF were significantly lower in the one-kidney group compared to the two-kidney group on day 14. On day 84, progressive glomerulosclerotic lesions were found, followed by a decrease of the capillary density in the one-kidney group, while the glomerular architecture recovered to an almost normal state in the two-kidney group.

CONCLUSIONS

Progressive glomerulosclerosis can be induced in the rat by a one shot injection of anti-Thy 1.1 monoclonal antibody followed by unilateral nephrectomy. This model shows that there is a positive association between impairment of vascular regeneration and the development of glomerulosclerosis.

Podocyte injuries exacerbate mesangial proliferative glomerulonephritis

BACKGROUND

From the observations of morphology seen in early phases of the experimental models of the irreversible mesangial proliferative glomerulonephritis, we hypothesized that podocyte injury is one of the important factors in bringing upon irreversible glomerular alterations. To verify this hypothesis, we investigated whether podocyte injury induced by puromycin aminonucleoside (PAN) injection affects the mesangial alterations of anti-Thy 1.1 glomerulonephritis.

METHODS

Female Wistar rats were injected with 0.5 mg monoclonal antibody (mAb) 1-22-3 five days after the injection of 10 mg or 5 mg/100 g body weight (BW) of puromycin aminonucleoside (PAN), and sacrificed at 7 days or 8 weeks after the mAb 1-22-3 injection.

RESULTS

Consecutive injections of 10 mg/100 g BW of PAN and mAb 1-22-3 caused the irreversible mesangial alteration with persistent proteinuria (at week 8, proteinuria 100.3 +/- 57.8 mg/24 h, matrix score 1.13 +/- 0.52, collagen type I score 2.04 +/- 0.53, mRNA for collagen type I 227 +/- 79% to the group with a single injection of 1-22-3). Although single injection of 5 mg/100 g BW of PAN was not capable of inducing abnormal proteinuria, consecutive injections of 5 mg/100 g BW of PAN and mAb 1-22-3 also caused irreversible mesangial alteration and persistent proteinuria.

CONCLUSIONS

Podocyte injury might be an important factor that exacerbates mesangial proliferation and mesangial matrix expansion. The irreversible mesangial alterations caused by consecutive injections of PAN and mAb 1-22-3 may be a novel model that could be used to analyze the mechanism of progressive mesangial alteration.

Anti-Thy-1 monoclonal antibody with specific reactivity with vascular endothelial cells in rat glomeruli

Inoculation with anti-Thy-1 antibodies (Abs) in rats induces glomerulonephritis resembling human mesangiolytic and/or mesangioproliferative diseases. Some anti-Thy-1 monoclonal Abs (mAbs) react with both mesangial and glomerular endothelial cells, whereas others react solely with mesangial cells in rat kidney. These findings suggest that the rat Thy-1 molecule possesses at least 2 variant forms, including a mesangial and a vascular endothelial isoform. However, anti-Thy-1 mAbs with specific reactivity with glomerular endothelial cells have not been available. We describe here a unique anti-rat Thy-1 mAb, TM78-8. The epitope for TM78-8 is closely related, but not identical, to that for OX-7, a commercially available anti-rat Thy-1 mAb. Immunoblotting, immunohistochemistry and immunoelectron microscopy confirm that TM78-8 reacts exclusively with Thy-1 antigens on the surface of vascular endothelial cells in rat glomeruli. TM78-8 may be a suitable marker for rat glomerular endothelial cells as well as for the vascular endothelial isoform of the rat Thy-1 molecule. Intravenous injection of TM78-8 did not induce glomerulonephritis in rats, whereas OX-7 did, indicating that TM78-8 is not nephritogenic. This finding also corresponds with the current consensus that Thy-1 antigens expressed on mesangial cells play an essential role in the development of Thy-1 nephritis.

Lung uptake of antibodies to endothelial antigens: key determinants of vascular immunotargeting

Vascular immunotargeting is a mean for a site-selective delivery of drugs and genes to endothelium. In this study, we compared recognition of pulmonary and systemic vessels in rats by candidate carrier monoclonal antibodies (MAbs) to endothelial antigens platelet endothelial cell adhesion molecule (PECAM)-1 (CD31), intercellular adhesion molecule (ICAM)-1 (CD54), Thy-1.1 (CD90.1), angiotensin-converting enzyme (ACE; CD143), and OX-43. Tissue immunostaining showed that endothelial cells were Thy-1.1 positive in capillaries but negative in large vessels. In the lung, anti-ACE MAb provided a positive staining in 100% capillaries vs. 5–20% capillaries in other organs. Other MAbs did not discriminate between pulmonary and systemic vessels. We determined tissue uptake after infusion of 1 μg of 125I-labeled MAbs in isolated perfused lungs (IPL) or intravenously in intact rats. Uptake in IPL attained 46% of the injected dose (ID) of anti-Thy-1.1 and 20–25% ID of anti-ACE, anti-ICAM-1, and anti-OX-43 (vs. 0.5% ID of control IgG). However, after systemic injection at this dose, only anti-ACE MAb 9B9 displayed selective pulmonary uptake (16 vs. 1% ID/g in other organs). Anti-OX-43 displayed low pulmonary (0.5% ID/g) but significant splenic and cardiac uptake (7 and 2% ID/g). Anti-Thy-1.1 and anti-ICAM-1 displayed moderate pulmonary (4 and 6% ID/g, respectively) and high splenic and hepatic uptake (e.g., 18% ID/g of anti-Thy-1.1 in spleen). The lung-to-blood ratio was 5, 10, and 15 for anti-Thy-1.1, anti-ACE, and anti-ICAM-1, respectively. PECAM antibodies displayed low pulmonary uptake in perfusion (2% ID) and in vivo (3–4% ID/g). However, conjugation with streptavidin (SA) markedly augmented pulmonary uptake of anti-PECAM in perfusion (10–54% ID, depending on an antibody clone) and in vivo (up to 15% ID/g). Therefore, ACE-, Thy-1.1-, ICAM-1-, and SA-conjugated PECAM MAbs are candidate carriers for pulmonary targeting. ACE MAb offers a high selectivity of pulmonary targeting in vivo, likely because of a high content of ACE-positive capillaries in the lungs.

Real-time observation of hemodynamic changes in glomerular aneurysms induced by anti-Thy-1 antibody

BACKGROUND

Blood flow in the microvasculature plays a pivotal role in determining the outcome of injury and repair in inflamed tissue. Real-time observation of the kidney microvasculature, including the glomerular capillary tufts, is extremely difficult because of the methodological limitations of currently available microscope optics. In the present study, we attempted to analyze hemodynamic events that occurred in vivo during microvascular regeneration following destruction of the glomerular capillary tuft, functionally and quantitatively by the use of a real-time confocal laser-scanning microscope (CLSM) system.

METHODS

A polyethylene catheter was inserted into the carotid artery to allow blood pressure measurement. Mesangiolytic lesions producing microaneurysms were induced by the injection of anti-Thy-1.1 antibody. On days 3 and 7 after antibody injection, we examined hemodynamic changes under an intravital microscope equipped with real-time CLSM in combination with a high-speed CCD video camera. To measure vessel diameter and erythrocyte velocity, rats were injected with fluorescein isothiocyanate (FITC)-labeled dextran and FITC-labeled red blood cells (RBCs).

RESULTS

On day 3 of the disease, mean arterial blood pressure was 112 +/- 5 mm Hg, which was significantly higher than that of normal rat or of rats on day 7 (93 +/- 1 and 101 +/- 9 mm Hg, respectively). Within mircroaneurysms on day 3, RBC velocity was greatly suppressed. By day 7, RBC velocity, in glomeruli with normal appearances, recovered to about half of the level seen in normal controls (430.6 +/- 284.7 microm/sec), while in narrowed glomerular tufts, it was still only 104.6 +/- 35.1 microm/sec.

CONCLUSIONS

The noninvasive procedure, using CLSM in combination with a high-speed video camera, allowed us to examine hemodynamic events quantitatively and to analyze microvascular architecture three dimensionally in the kidney. It is useful for estimating hemodynamic response and vascular regeneration in vivo and may be promising for clinical application.

Localization of Smad6 and Smad7 in the rat kidney and their regulated expression in the anti-Thy-1 nephritis

Under normal conditions, kidney expresses Smad6 and Smad7 most abundantly among the organs of the body. To understand the physiological roles of these Smad expressions in the kidney, we first identified the sites of Smad6 and Smad7 expression in the rat kidney by in situ hybridization. The expression of Smad7 in the rat kidney was only observed in the glomeruli, while Smad6 was expressed in both the glomeruli and thick ascending limb of Henle's loop. In order to investigate whether Smad6 and 7 are also involved in the negative feedback loop of TGF-beta signaling in vivo, we examined the changes of mRNA levels of these Smads in the glomeruli of rat anti-Thy1 (1-22-3) nephritis, a model where the expression of TGF-beta in the glomeruli has been shown to be most up-regulated from day 4 to 14 after the antibody injection. Unexpectedly, 7 days after injection, the levels of Smad6 and Smad7 did not increase but rather decreased to approximately 70% of the levels on day 0. During that period, Smad7 immunostaining was observed in the glomerular endothelial cells (GEN) where Smad3 immunostaining was also observed. This suggested that Smad7 expression was not augmented by the TGF-beta signal in GEN in vivo in anti-Thy-1 nephritis. The absence of up-regulation of these inhibitory Smads may be involved in the pathogenesis of anti-Thy-1 nephritis.

An anti-CD5 monoclonal antibody ameliorates proteinuria and glomerular lesions in rat mesangioproliferative glomerulonephritis

BACKGROUND

Increased numbers of lymphocytes have been identified in biopsy specimens of human mesangial proliferative glomerulonephritis (GN). However, the causal relationship between infiltrating T lymphocytes and mesangial changes in mesangial proliferative GN has not been previously evaluated. In this study, we elucidated the role of lymphocytes in the development of mesangial proliferative GN.

METHOD

Immunohistological and flow cytometric analyses as well as a reverse transcription-polymerase chain reaction (RT-PCR) studies were performed in monoclonal antibody (mAb) 1-22-3-induced Thy 1.1 GN. To elucidate the role of these lymphocytes, depletion studies were carried out using anti-CD8 mAb (OX-8), which depletes both CD8+ T lymphocytes and natural killer (NK) cells and anti-CD5 mAb (OX-19), which depletes both CD4+ and CD8+ T lymphocytes.

RESULTS

Immunofluorescence (IF) studies revealed that NK cells and CD4+ T lymphocytes were recruited into glomeruli. Glomerular mRNA expression for interferon-gamma, interleukin-2 (IL-2), IL-10, and perforin increased after induction of GN. Increased expressions of several chemokines, which have the potential to attract lymphocytes, were also detected. Anti-CD8 mAb treatment completely prevented the recruitment of NK cells; however, it had no protective effect on proteinuria and mesangial injury. By contrast, anti-CD5 mAb treatment suppressed the recruitment of CD4+ T lymphocytes into glomeruli and reduced proteinuria (60.4 +/- 25.7 vs. 120.0 +/- 32.3 mg/day, P < 0.05) and mesangial changes evaluated by total number of cells in glomeruli (63.2 +/- 6.0 vs. 81.4 +/- 5.9, P < 0.01) and alpha-smooth muscle actin staining score (1.4 +/- 0.2 vs. 2.2 +/- 0. 4, cf2eth P < 0.01) on day 14 after induction of GN. mRNA expression for IL-2 was significantly reduced by OX-19 treatment.

CONCLUSION

T lymphocytes participate in the development of mesangial proliferative GN.

Role of mesangial cell damage in progressive renal disease

Mesangial cell proliferation and matrix accumulation are considered to contribute to the development of glomerulosclerosis. To investigate the pathological role played by mesangial cell damage in progressive renal disease appropriate progressive models initiated by a mesangial cell injury should be developed. Monoclonal antibody (mAb) 1-22-3 (IgG3) recognizes a critical epitope of the Thy-1.1 molecule on the mesangial cell surface, binding of which induces more severe mesangial cell injury than in the case of OX-7, a commercially obtainable anti-Thy-1.1 mAb. The mAb 1-22-3 has enabled us to develop irreversible models of renal damage induced by two consecutive injections, by a single injection into unilaterally nephrectomized rats, or by a single simultaneous injection with another mAb, in addition to the corresponding reversible model. Detailed examinations using the combination of both types of models, all of which are initiated by an immune mechanism directed against the identical epitope on the Thy-1.1 molecule, are expected to provide new insights into mechanisms of irreversible renal injury initiated by mesangial cell damage and also to develop novel and rational therapeutic approaches to progressive, primarily mesangial diseases.