Contribution of epithelial plasticity to renal transplantation-associated fibrosis

Every year in the United States, 5000 renal transplant recipients start or restart dialysis because of the unusual propensity of these allografts to develop interstitial fibrosis and tubular atrophy (IF/TA). Although IF/TA often follows one or more identifiable events, our capacity to specifically treat, prevent, or even detect IF/TA at an early stage is poor. These limitations are largely related to our lack of adequate tools to assess graft failure over time. Data accumulated over the past 5 years have demonstrated that tubular epithelial cells may react to certain fibrogenic stimuli to engage in the process of epithelial-to-mesenchymal transition (EMT). In this review, we highlight the current view of EMT with a focus on both its role in the context of renal transplantation and the potential for utilizing markers of EMT to identify patients undergoing early IF/TA.

Contribution of bone microenvironment to leukemogenesis and leukemia progression

Tumor microenvironment has a major role in cancer progression and resistance to treatment. The bone marrow (BM) is a dynamic network of growth factors, cytokines and stromal cells, providing a permissive environment for leukemogenesis and progression. Both BM stroma and leukemic blasts promote angiogenesis, which is increased in acute lymphoblastic leukemia and acute myeloid leukemia. Growth factors like vascular endothelial growth factor (VEGF), basic fibroblast growth factor and angiopoietins are the main proangiogenic mediators in acute leukemia. Autocrine proleukemic loops have been described for VEGF and angiopoietin in hematopoietic cells. Interactions of stromal cells and extracellular matrix with leukemic blasts can also generate antiapoptotic signals that contribute to neoplastic progression and persistence of treatment-resistant minimal residual disease. High expression of CXC chemokine ligand 4 (CXCR4) by leukemic blasts and activation of the CXCR4-CXCL12 axis is involved in leukemia progression and disruption of normal hematopoiesis. Leukemia-associated bone microenvironment markers could be used as prognostic or predictive indicators of disease progression and/or treatment outcome. Studies related to bone microenvironment would likely provide a better understanding of the treatment resistance associated with leukemia therapy and design of new treatments.

The role of endothelial-to-mesenchymal transition in cancer progression

Recent evidence has demonstrated that endothelial-to-mesenchymal transition (EndMT) may have a significant role in a number of diseases. Although EndMT has been previously studied as a critical process in heart development, it is now clear that EndMT can also occur postnatally in various pathologic settings, including cancer and cardiac fibrosis. During EndMT, resident endothelial cells delaminate from an organised cell layer and acquire a mesenchymal phenotype characterised by loss of cell–cell junctions, loss of endothelial markers, gain of mesenchymal markers, and acquisition of invasive and migratory properties. Endothelial-to-mesenchymal transition -derived cells are believed to function as fibroblasts in damaged tissue, and may therefore have an important role in tissue remodelling and fibrosis. In tumours, EndMT is an important source of cancer-associated fibroblasts (CAFs), which are known to facilitate tumour progression in several ways. These new findings suggest that targeting EndMT may be a novel therapeutic strategy, which is broadly applicable not only to cancer but also to various other disease states.

Choosing a mouse model to study the molecular pathobiology of Alport glomerulonephritis

Alport syndrome, caused by mutations that interfere with the normal assembly of the alpha3alpha4alpha5(IV) collagen network in the glomerular basement membrane (GBM), is the most common inherited glomerular disease leading to renal failure. A detailed knowledge of the underlying pathogenic mechanisms is necessary for developing new, more specific, and effective therapeutic strategies aimed at delaying the onset and slowing disease progression. Studies of several dog and mouse models of Alport syndrome have significantly enhanced our understanding of the disease mechanisms and provided systems for testing potential therapies. In the most widely used Col4a3-/- mouse models of autosomal-recessive Alport syndrome (ARAS), the genetic background strongly affects renal survival. One contributing factor may be the strong ectopic deposition of alpha5alpha6(IV) collagen in the GBM of Col4a3-/- mice on the C57BL/6J background, which is almost undetectable on the 129/Sv background. This isoform 'switch' has not been observed in human ARAS, although it had been reported in the dog model of ARAS. In human patients as well as dog and mouse models of X-linked Alport syndrome, the alpha3-alpha6(IV) collagen chains are absent from the GBM. These biochemical differences among Alport animal models provide an opportunity to determine how the molecular makeup of the GBM affects the glomerular function. At the same time, potentially confounding influences of characteristics unique to a particular strain or model should be carefully considered in the design of studies aiming to define key events underlying the pathobiology of Alport glomerular disease.

Structural basis for the functions of endogenous angiogenesis inhibitors

Tipping the angiogenic balance between pro- and antiangiogenic stimuli to favor vasculature induction and enhanced angiogenesis is a key event in the growth and progression of tumors. Recently, we demonstrated that the genetic loss of normal physiological levels of individual endogenous inhibitors of angiogenesis leads to a change in the balance between proangiogenic stimulators and their inhibitors, thus favoring enhanced angiogensis and increased tumor growth. Therefore, these endogenous angiogenesis inhibitors provide a physiological threshold against the induction of angiogenesis. The antiangiogenic activities of endostatin, tumstatin, and thrombospondin-1 are evaluated and correlated with their three-dimensional structure and active sites, deriving a structural basis for their activities. Collectively, structural analysis of all three inhibitors demonstrates that the active antiangiogenic sites on these molecules are exposed on the surface and available to bind their putative integrin receptors on proliferating endothelial cells.

Exploring the connection between chronic renal fibrosis and bone morphogenic protein-7

Tubulointerstitial fibrosis is a hallmark feature of chronic renal injury. Specific therapies to control the progression of renal fibrosis towards end-stage renal failure are still limited. Transforming growth factor-beta1 (TGF-beta1) has been identified as a major mediator of renal fibrosis. Recent reports have suggested that Bone Morphogenic Protein-7 (BMP-7), another member of the TGF-beta superfamily, accelerates repair of acute renal injury and ameliorates progression of chronic renal fibrosis in a variety of animal models. Interestingly, BMP-7, an endogenous molecule which is present in the normal kidney, vastly decreases its expression during renal injury. Although, the mechanism of BMP-7 action in the kidney is not yet fully understood, the idea of an endogenous molecule with reno-protective function is intriguing.

Renal fibrosis: collagen composition and assembly regulates epithelial-mesenchymal transdifferentiation

Type IV collagen is a major component of basement membranes and it provides structural and functional support to various cell types. Type IV collagen exists in a highly complex suprastructure form and recent studies implicate that protomer (the trimeric building unit of type IV collagen) assembly is mediated by the NC1 domain present in the C-terminus of each collagen alpha-chain polypeptide. Here we show that type IV collagen contributes to the maintenance of the epithelial phenotype of proximal tubular epithelial cells, whereas type I collagen promotes epithelial-to-mesenchymal transdifferentiation (EMT). In addition, the recombinant human alpha1NC1 domain inhibits assembly of type IV collagen NC1 hexamers and potentially disrupts the deposition of type IV collagen, facilitating EMT in vitro. Inhibition of type IV collagen assembly by the alpha1NC1 domain up-regulates the production of transforming growth factor-beta1 in proximal tubular epithelial cells, an inducer of EMT. These results strongly suggest that basement membrane architecture is pivotal for the maintenance of epithelial phenotype and that changes in basement membrane architecture potentially lead to up-regulation of transforming growth factor-beta1, which contributes to EMT during renal fibrosis.

Extracellular matrix-derived peptide binds to alpha(v)beta(3) integrin and inhibits angiogenesis

Angiogenesis is associated with several pathological disorders as well as with normal physiological maintenance. Components of vascular basement membrane are speculated to regulate angiogenesis in both positive and negative manner. Recently, we reported that tumstatin (the NC1 domain of alpha 3 chain of type IV collagen) and its deletion mutant tum-5 possess anti-angiogenic activity. In the present study, we confirm that the anti-angiogenic activity of tumstatin and tum-5 is independent of disulfide bond requirement. This property of tum-5 allowed us to use overlapping synthetic peptide strategy to identify peptide sequence(s) which possess anti-angiogenic activity. Among these peptides, only the T3 peptide (69-88 amino acids) and T7 peptide (74-98 amino acids) inhibited proliferation and induced apoptosis specifically in endothelial cells. The peptides, similar to tumstatin and the tum-5 domain, bind and function via alpha(v)beta(3) in an RGD-independent manner. Restoration of a disulfide bond between two cysteines within the peptide did not alter the anti-angiogenic activity. Additionally, these studies show that tumstatin peptides can inhibit proliferation of endothelial cells in the presence of vitronectin, fibronectin, and collagen I. Anti-angiogenic effect of the peptides was further confirmed in vivo using a Matrigel plug assay in C57BL/6 mice. Collectively, these experiments suggest that the anti-angiogenic activity of tumstatin is localized to a 25-amino acid region of tumstatin and it is independent of disulfide bond linkage. Structural features and potency of the tumstatin peptide make it highly feasible as a potential anti-cancer drug.

Renal fibroblast-like cells in Goodpasture syndrome rats

BACKGROUND

The extent of renal fibrosis is the best predictor for functional outcomes in a variety of progressive renal diseases. Interstitial fibroblast-like cells (FbLCs) are presumably involved in the fibrotic process. However, such FbLCs have never been well characterized in the kidney.

METHODS

We characterized renal FbLCs in the nephritic kidney (in which the number of FbLCs and extracellular matrix accumulation were significantly increased) with regards to their expression of phenotypic and functional markers using day 49 Goodpasture syndrome (GPS) rats.

RESULTS

Within the renal cortical interstitium, there were a number of alpha-smooth muscle actin(+) (alpha-SMA(+)) FbLCs, negative for vimentin (VIM) and transforming growth factor-beta 1, and not equipped with well-developed rough endoplasmic reticulum and actin-stress fibers. All of these findings were incompatible with the typical features of granulation tissue alpha-SMA(+) myofibroblasts. On the other hand, FbLCs negative for alpha-SMA and VIM produced alpha1(I) procollagen in the nephritic kidney.

CONCLUSION

A number of FbLC populations reside within the cortical interstitium of the kidney in GPS rats, each of which is likely to have developed independently in response to the local conditions of the nephritic kidney, contributing to renal fibrogenesis. Further studies are needed to clarify the key type of FbLC that orchestrates other members to produce renal fibrosis.

Identification of the anti-angiogenic site within vascular basement membrane-derived tumstatin

Components of vascular basement membrane are involved in regulating angiogenesis. Recently, tumstatin (the NC1 domain of alpha3 chain of type IV collagen) was identified as possessing anti-angiogenic activity. In the present study, the anti-angiogenic activity of tumstatin was localized to the putative 54-132-amino acid Tum-5 domain, and the activity mediated by alpha(v)beta(3) integrin interaction in an RGD-independent manner. The recombinant Tum-5 produced in Escherichia coli and Pichia Pastoris specifically inhibited proliferation and caused apoptosis of endothelial cells with no significant effect on nonendothelial cells. Tum-5 also inhibited tube formation of endothelial cells on Matrigel and induced G1 endothelial cell cycle arrest. Moreover, anti-angiogenic effect of Tum-5 was also examined in vivo using both a Matrigel plug assay in C57BL/6 mice and human prostate cancer (PC-3) xenografts in nude mice. The in vivo results demonstrate that Tum-5 at 1 mg/kg significantly inhibited growth of PC-3 tumors in association with a decrease in CD31 positive vasculature. These in vivo studies also show that, at molar equivalents, human Tum-5 is at least 10-fold more active than human endostatin. In addition, these studies for the first time suggest that through the action of endogenous inhibitors, alpha(v)beta(3) integrin may also function as a negative regulator of angiogenesis. Taken together, these findings demonstrate that Tum-5, a domain derived from tumstatin, is an effective inhibitor of tumor-associated angiogenesis and a promising candidate for the treatment of cancer.

Cell surface glypicans are low-affinity endostatin receptors

Endostatin, a collagen XVIII fragment, is a potent anti-angiogenic protein. We sought to identify its endothelial cell surface receptor(s). Alkaline phosphatase- tagged endostatin bound endothelial cells revealing two binding affinities. Expression cloning identified glypican, a cell surface proteoglycan as the lower-affinity receptor. Biochemical and genetic studies indicated that glypicans' heparan sulfate glycosaminoglycans were critical for endostatin binding. Furthermore, endostatin selected a specific octasulfated hexasaccharide from a sequence in heparin. We have also demonstrated a role for endostatin in renal tubular cell branching morphogenesis and show that glypicans serve as low-affinity receptors for endostatin in these cells, as in endothelial cells. Finally, antisense experiments suggest the critical importance of glypicans in mediating endostatin activities.

Identification and localization of type IV collagen chains in the inner ear cochlea

Mutations in the genes encoding the alpha3(IV), alpha4(IV) and alpha5(IV) chains of type IV collagen have been implicated in the pathogenesis of Alport's syndrome, a hereditary disorder characterized by progressive nephropathy and sensorineural deafness. The known expression of these chains in kidney basement membranes supports the contention that they play a crucial role in the ultrafiltration function. Whether they play a role in auditory signal transduction remains unknown as heretofore, they have not been identified in the inner ear. In the present study, the expression of type IV collagen in cochlea of the inner ear of guinea pigs was determined. All six alpha-chains of type IV collagen were identified by biochemical and immunological methods. By indirect immunofluorescence, alpha1(IV) and alpha2(IV) chains were localized to the spiral limbus, basilar membrane and tectorial membrane. The alpha3(IV), alpha4(IV), alpha5(IV) and alpha6(IV) chains localized exclusively to the tectorial membrane and basilar membrane. These results suggest a possible role of type IV collagen chains in the active tuning of the basilar and tectorial membrane, an essential step in frequency discrimination and amplification of auditory signals.

Aminopeptidase A: a nephritogenic target antigen of nephrotoxic serum

BACKGROUND

We investigated potential targets of antibody-mediated glomerular injury induced with a noncomplement binding fraction of sheep anti-rat nephrotoxic serum (NTS). This model is characterized by severe complement- and leukocyte-independent proteinuria within 24 hours of NTS injection into rats.

METHODS

NTS-reactive glomerular cell and matrix proteins were identified by immunoprecipitation, Western blot analysis, protein sequencing, cDNA library screening, and enzyme-linked immunosorbent assay. Proteinuria was measured in rats injected with NTS from which reactivity against type IV collagen had been removed by immunoadsorption, and antibodies were eluted from the glomeruli of proteinuric rats that had been injected with unabsorbed NTS. Having identified aminopeptidase A (APA) as a major target of NTS, we studied the effect of NTS and anti-APA on mouse glomerular epithelial cells in culture.

RESULTS

NTS identified several podocyte and matrix proteins; however, APA was the only cell surface protein reactive with antibodies eluted from the glomeruli of rats injected with NTS. Although the eluate also contained reactivity to the noncollagenous domains of alpha1 and alpha3 chains of type IV collagen, immunodepletion of these antibodies did not diminish the ability of NTS to cause proteinuria. We also documented the surface expression of APA on mouse glomerular epithelial cells in culture, and found that NTS and specific anti-APA antibodies induce a time- and temperature-dependent redistribution of the antigen.

CONCLUSIONS

APA, a type II integral membrane metallopeptidase, is a major target of NTS in vivo and is known to be present on the surface of podocytes. NTS-induced proteinuria is independent of reactivity to known nephritogenic matrix proteins. These findings, in combination with previous studies showing that monoclonal anti-APA antibodies induce severe proteinuria in mice, suggest that anti-APA antibodies are responsible for complement-independent proteinuria in this model.

Distortion-product source unmixing: a test of the two-mechanism model for DPOAE generation

This paper tests key predictions of the "two-mechanism model" for the generation of distortion-product otoacoustic emissions (DPOAEs). The two-mechanism model asserts that lower-sideband DPOAEs constitute a mixture of emissions arising not simply from two distinct cochlear locations (as is now well established) but, more importantly, by two fundamentally different mechanisms: nonlinear distortion induced by the traveling wave and linear coherent reflection off pre-existing micromechanical impedance perturbations. The model predicts that (1) DPOAEs evoked by frequency-scaled stimuli (e.g., at fixed f2/f1) can be unmixed into putative distortion- and reflection-source components with the frequency dependence of their phases consistent with the presumed mechanisms of generation; (2) The putative reflection-source component of the total DPOAE closely matches the reflection-source emission (e.g., low level stimulus-frequency emission) measured at the same frequency under similar conditions. These predictions were tested by unmixing DPOAEs into components using two completely different methods: (a) selective suppression of the putative reflection source using a third tone near the distortion-product frequency and (b) spectral smoothing (or, equivalently, time-domain windowing). Although the two methods unmix in very different ways, they yield similar DPOAE components. The properties of the two DPOAE components are consistent with the predictions of the two-mechanism model.

NM-3, an isocoumarin, increases the antitumor effects of radiotherapy without toxicity

We examined the effects of a new antiangiogenic isocoumarin, NM-3, as a radiation modifier in vitro and in vivo. The present studies demonstrate that NM-3 is cytotoxic to human umbilical vein endothelial cells (HUVECs) but not to Lewis lung carcinoma (LLC) cells nor Seg-1, esophageal adenocarcinoma cells, in clonogenic survival assays. When HUVEC cultures are treated with NM-3 combined with ionizing radiation (IR), additive cytotoxicity is observed. In addition, the combination of NM-3 and IR inhibits HUVEC migration to a greater extent than either treatment alone. The effects of treatment with NM-3 and IR were also evaluated in tumor model systems. C57BL/6 female mice bearing LLC tumors were given injections for 4 consecutive days with NM-3 (25 mg/kg/day) and treated with IR (20 Gy) for 2 consecutive days. Combined treatment with NM-3 and IR significantly reduced mean tumor volume compared with either treatment alone. An increase in local tumor control was also observed in LLC tumors in mice receiving NM-3/IR therapy. When athymic nude mice bearing Seg-1 tumor xenografts were treated with NM-3 (100 mg/kg/day for 4 days) and 20 Gy (four 5 Gy fractions), significant tumor regression was observed after combined treatment (NM-3 and IR) compared with IR alone. Importantly, no increase in systemic or local tissue toxicity was observed after combined treatment (NM-3 and IR) when compared with IR alone. The bioavailability and nontoxic profile of NM-3 suggests that the efficacy of this agent should be tested in clinical radiotherapy.

Integrin alpha1beta1 and transforming growth factor-beta1 play distinct roles in alport glomerular pathogenesis and serve as dual targets for metabolic therapy

Alport syndrome is a genetic disorder resulting from mutations in type IV collagen genes. The defect results in pathological changes in kidney glomerular and inner-ear basement membranes. In the kidney, progressive glomerulonephritis culminates in tubulointerstitial fibrosis and death. Using gene knockout-mouse models, we demonstrate that two different pathways, one mediated by transforming growth factor (TGF)-beta1 and the other by integrin alpha1beta1, affect Alport glomerular pathogenesis in distinct ways. In Alport mice that are also null for integrin alpha1 expression, expansion of the mesangial matrix and podocyte foot process effacement are attenuated. The novel observation of nonnative laminin isoforms (laminin-2 and/or laminin-4) accumulating in the glomerular basement membrane of Alport mice is markedly reduced in the double knockouts. The second pathway, mediated by TGF-beta1, was blocked using a soluble fusion protein comprising the extracellular domain of the TGF-beta1 type II receptor. This inhibitor prevents focal thickening of the glomerular basement membrane, but does not prevent effacement of the podocyte foot processes. If both integrin alpha1beta1 and TGF-beta1 pathways are functionally inhibited, glomerular foot process and glomerular basement membrane morphology are primarily restored and renal function is markedly improved. These data suggest that integrin alpha1beta1 and TGF-beta1 may provide useful targets for a dual therapy aimed at slowing disease progression in Alport glomerulonephritis.

Antitumor interaction of short-course endostatin and ionizing radiation

PURPOSE

The purpose of this study was to evaluate whether endostatin, an antiangiogenic cleavage fragment of collagen XVIII, enhances the antitumor effects of ionizing radiation (IR). Endostatin was injected to coincide with fractionated radiotherapy.

METHODS

Xenografts of radioresistant SQ-20B tumor cells were established in athymic nude mice. Lewis lung carcinoma cells were injected into C57BI/6 mice. Mice bearing SQ-20B xenografts were injected intraperitoneally with 2.5 mg/kg/day of murine recombinant endostatin 5 times per week for 2 weeks 3 hours before IR treatment (50 Gy total dose). Mice bearing Lewis lung carcinoma tumors were injected intraperitoneally with endostatin (2.5 mg/kg/day) four times; the first injection was given 24 hours before the first IR dose (15 Gy) and then 3 hours before IR (15 Gy/day) for 3 consecutive days. Microvascular density was assessed on tumor tissue sections by use of CD31 immunohistochemistry and light microscopy. Endothelial cell survival analyses were employed to evaluate endostatin effects on human aortic endothelial cells and human umbilical vein endothelial cells. Endothelial cell apoptosis was examined by use of FACS analysis and DAPI microscopy.

RESULTS

In SQ-20B xenografts, combined treatment with endostatin and IR produced tumor growth inhibition that was most pronounced at the nadir of regression (day 21). By day 35, tumors receiving combined treatment with endostatin and IR were 47% smaller than tumors treated with endostatin alone. Interactive cytotoxic treatment effects between endostatin and IR were also demonstrated in mice bearing Lewis lung carcinoma tumors. Significant tumor growth inhibition was observed in the endostatin/IR group at days 11 and 13 compared with IR alone. Histologic analyses demonstrated a reduction in microvascular density after combined treatment with endostatin and IR compared with endostatin treatment alone. Survival analyses confirmed interactive cytotoxicity between endostatin and IR in both human aortic endothelial cells and human umbilical vein endothelial cells but not in SQ-20B tumor cells. Combined treatment with endostatin and IR produced an increase in cow pulmonary artery endothelial apoptosis compared with either treatment alone.

DISCUSSION

The tumor regression observed after combined treatment with endostatin and IR suggests additive antitumor effects in both human and murine tumors. Importantly, the concentrations of endostatin employed produced little tumor regression when endostatin was employed as a single agent. The results from the clonogenic and apoptosis assays support the hypothesis that the endothelial compartment is the target for the endostatin/IR interaction.

Two RGD-independent alpha vbeta 3 integrin binding sites on tumstatin regulate distinct anti-tumor properties

Vascular basement membrane is an important regulator of angiogenesis and undergoes many alterations during angiogenesis and these changes are speculated to influence neovascularization. Recently, fragments of collagen molecules have been identified to possess anti-angiogenic activity. Tumstatin (alpha3(IV)NC1 domain) is one such novel molecule with distinct anti-tumor properties and possesses an N-terminal (amino acids 54-132) anti-angiogenic and a C-terminal (amino acids 185-203) anti-tumor cell activity (Maeshima, Y., et al. 2000) J. Biol. Chem. 275, 21340-21348). Previous studies have identified the 185-203 amino acid sequence as a ligand for alpha(v)beta(3) integrin (Shahan, T. A., et al. (1999) Cancer Res. 59, 4584-4590). In the present study, we found distinct additional RGD-independent alpha(v)beta(3) integrin binding site within 54-132 amino acids of tumstatin. This site is not essential for inhibition of tumor cell proliferation but necessary for the anti-angiogenic activity. A fragment of tumstatin containing 54-132 amino acid (tum-2) binds both endothelial cells and melanoma cells but only inhibited proliferation of endothelial cells, with no effect on tumor cell proliferation. A similar experiment with fragment of tumstatin containing the 185-203 amino acid (tum-4) demonstrates that it binds both endothelial cells and melanoma cells but only inhibits the proliferation of melanoma cells. The presence of cyclic RGD peptides did not affect the alpha(v)beta(3) integrin-mediated activity of tumstatin, although significant inhibition of endothelial cell binding to vitronectin was observed. The two distinct RGD-independent binding sites on tumstatin suggest unique alpha(v)beta(3) integrin-mediated mechanisms governing the two distinct anti-tumor properties of tumstatin.

Distinct antitumor properties of a type IV collagen domain derived from basement membrane

Vascular basement membrane is an important structural component of blood vessels. During angiogenesis this membrane undergoes many alterations and these changes are speculated to influence the formation of new capillaries. Type IV collagen is a major component of vascular basement membrane, and recently we identified a fragment of type IV collagen alpha2 chain with specific anti-angiogenic properties (Kamphaus, G. D., Colorado, P. C., Panka, D. J., Hopfer, H., Ramchandran, R., Torre, A., Maeshima, Y., Mier, J. W., Sukhatme, V. P., and Kalluri, R. (2000) J. Biol. Chem. 275, 1209-1215). In the present study we characterize two different antitumor activities associated with the noncollagenous 1 (NC1) domain of the alpha3 chain of type IV collagen. This domain was previously discovered to possess a C-terminal peptide sequence (amino acids 185-203) that inhibits melanoma cell proliferation (Han, J., Ohno, N., Pasco, S., Monboisse, J. C., Borel, J. P., and Kefalides, N. A. (1997) J. Biol. Chem. 272, 20395-20401). In the present study, we identify the anti-angiogenic capacity of this domain using several in vitro and in vivo assays. The alpha3(IV)NC1 inhibited in vivo neovascularization in matrigel plug assays and suppressed tumor growth of human renal cell carcinoma (786-O) and prostate carcinoma (PC-3) in mouse xenograft models associated with in vivo endothelial cell-specific apoptosis. The anti-angiogenic activity was localized to amino acids 54-132 using deletion mutagenesis. This anti-angiogenic region is separate from the 185-203 amino acid region responsible for the antitumor cell activity. Additionally, our experiments indicate that the antitumor cell activity is not realized until the peptide region is exposed by truncation of the alpha3(IV)NC1 domain, a requirement not essential for the anti-angiogenic activity of this domain. Collectively, these results effectively highlight the distinct and unique antitumor properties of the alpha3(IV)NC1 domain and the potential use of this molecule for inhibition of tumor growth.

High affinity of anti-GBM antibodies from Goodpasture and transplanted Alport patients to alpha3(IV)NC1 collagen

BACKGROUND

Anti-glomerular basement membrane (anti-GBM) antibody-mediated diseases are characterized by rapidly progressive glomerulonephritis (RPGN) that often results in irreversible loss of renal function and renal failure. Although many factors contribute to the fulminant nature and treatment resistance of this disease, we questioned whether high affinity autoantibody-alpha3(IV) collagen interactions lead to persistent antibody deposition, thereby perpetuating inflammation. To address this hypothesis, the binding kinetics of human anti-GBM antibodies (Ab) to alpha3(IV)NC1 were evaluated using an optical biosensor interaction analysis.

METHODS

Polyclonal anti-GBM Abs were purified by alpha3(IV)NC1 affinity chromatography from the sera of patients with anti-GBM AB-mediated diseases, including individuals with Goodpasture syndrome (GS), idiopathic RPGN (N = 7), and Alport syndrome (AL) following kidney transplantation (N = 4). The affinity-binding characteristics of the autoantibodies were determined using a biosensor analysis system, with immobilized bovine alpha3(IV)NC1 dimers.

RESULTS

All of the autoantibody preparations bound to alpha3(IV)NC1, whereas none bound to alpha1(IV)NC1 (control). Purified, normal serum IgG did not bind to either antigen. Estimated dissociation constants (Kd) for the purified autoantibodies were 1.39E-04 +/- 7.30E-05 s-l (GS) and 8. 90E-05 +/- 2.80E-05 s-l (AL). Their estimated association constants (Ka) were 2.67E+04 +/- 1.8E+04 (M-ls-l) and 2.76E+04 +/- 1. 70E+04(M-ls-l) for GS and AL patients, respectively. By comparison with other Ab interactions, these Abs demonstrated high affinity, with relatively high on (binding) rates and slow off (dissociation) rates.

CONCLUSIONS

The results suggest that anti-GBM Abs bind rapidly and remain tightly bound to the GBM in vivo. This property likely contributes to both the fulminant nature of this disease and its resistance to therapy, because persistent glomerular Ab deposition has the potential to produce continuous inflammation, despite removal of circulating Abs and adequate immunosuppression.

Fibrosis and angiogenesis

Research during the past few years has contributed vastly to a better understanding of fibrosis and angiogenesis. Although studies to understand the molecular processes associated with fibrosis and angiogenesis were performed independently of each other, some common parallels have emerged. Translation of these observations into potential therapeutic possibilities needs further exploration.

Reactive oxygen species expose cryptic epitopes associated with autoimmune goodpasture syndrome

Goodpasture syndrome is an autoimmune disease of the kidneys and lungs mediated by antibodies and T-cells directed to cryptic epitopes hidden within basement membrane hexamers rich in alpha3 non-collagenous globular (NC1) domains of type IV collagen. These epitopes are normally invisible to the immune system, but this privilege can be obviated by chemical modification. Endogenous drivers of immune activation consequent to the loss of privilege have long been suspected. We have examined the ability of reactive oxygen species (ROS) to expose Goodpasture epitopes buried within NC1 hexamers obtained from renal glomeruli abundant in alpha3(IV) NC1 domains. For some hexameric epitopes, like the Goodpasture epitopes, exposure to ROS specifically enhanced recognition by Goodpasture antibodies in a sequential and time-dependent fashion; control binding of epitopes to alpha3(IV) alloantibodies from renal transplant recipients with Alport syndrome was decreased, whereas epitope binding to heterologous antibodies recognizing all alpha3 NC1 epitopes remained the same. Inhibitors of hydrogen peroxide and hydroxyl radical scavengers were capable of attenuating the effects of ROS in cells and kidney by 30-50%, respectively, thereby keeping the Goodpasture epitopes largely concealed when compared with a 70% maximum inhibition by iron chelators. Hydrogen peroxide administration to rodents was sufficient to expose Goodpasture epitope in vivo and initiate autoantibody production. Our findings collectively suggest that ROS can alter the hexameric structure of type IV collagen to expose or destroy selectively immunologic epitopes embedded in basement membrane. The reasons for autoimmunity in Goodpasture syndrome may lie in an age-dependent deterioration in inhibitor function modulating oxidative damage to structural molecules. ROS therefore may play an important role in shaping post-translational epitope diversity or neoantigen formation in organ tissues.

Anti-angiogenic cues from vascular basement membrane collagen

Vascular basement membrane is an important structural component of blood vessels and has been shown to interact with and modulate vascular endothelial behavior during angiogenesis. During the inductive phase of tumor angiogenesis, this membrane undergoes many degradative and structural changes and reorganizes to a native state around newly formed capillaries in the resolution phase. Such matrix changes are potentially associated with molecular modifications that include expression of matrix gene products coupled with conformational changes, which expose cryptic protein modules for interaction with the vascular endothelium. We speculate that these interactions provide important endogenous angiogenic and anti-angiogenic cues. In this report, we identify an important antiangiogenic vascular basement membrane-associated protein, the 26-kDa NC1 domain of the alpha1 chain of type IV collagen, termed arresten. Arresten was isolated from human placenta and produced as a recombinant molecule in Escherichia coli and 293 embryonic kidney cells. We demonstrate that arresten functions as an anti-angiogenic molecule by inhibiting endothelial cell proliferation, migration, tube formation, and Matrigel neovascularization. Arresten inhibits the growth of two human xenograft tumors in nude mice and the development of tumor metastases. Additionally, we show that the anti-angiogenic activity of arresten is potentially mediated via mechanisms involving cell surface proteoglycans and the alpha1beta1 integrin on endothelial cells. Collectively, our results suggest that arresten is a potent inhibitor of angiogenesis with a potential for therapeutic use.

Assembly of type IV collagen. Insights from alpha3(IV) collagen-deficient mice

Type IV collagen includes six genetically distinct polypeptides named alpha1(IV) through alpha6(IV). These isoforms are speculated to organize themselves into unique networks providing mammalian basement membranes specificity and inequality. Recent studies using bovine and human glomerular and testis basement membranes have shown that unique networks of collagen comprising either alpha1 and alpha2 chains or alpha3, alpha4, and alpha5 chains can be identified. These studies have suggested that assembly of alpha5 chain into type IV collagen network is dependent on alpha3 expression where both chains are normally present in the tissue. In the present study, we show that in the lens and inner ear of normal mice, expression of alpha1, alpha2, alpha3, alpha4, and alpha5 chains of type IV collagen can be detected using alpha chain-specific antibodies. In the alpha3(IV) collagen-deficient mice, only the expression of alpha1, alpha2, and alpha5 chains of type IV collagen was detectable. The non-collagenous 1 domain of alpha5 chain was associated with alpha1 in the non-collagenous 1 domain hexamer structure, suggesting that network incorporation of alpha5 is possible in the absence of the alpha3 chain in these tissues. The present study proves that expression of alpha5 is not dependent on the expression of alpha3 chain in these tissues and that alpha5 chain can assemble into basement membranes in the absence of alpha3 chain. These findings support the notion that type IV collagen assembly may be regulated by tissue-specific factors.

Inhibition of monocyte chemoattractant protein-1 expression in tubular epithelium attenuates tubulointerstitial alteration in rat Goodpasture syndrome

BACKGROUND

To examine the role of monocyte chemoattractant protein-1 (MCP-1) expressed by tubular epithelium in tubulointerstitial alterations in situ, the level of MCP-1 mRNA in tubular epithelium was lowered selectively in the rat model of Goodpasture syndrome (GPS).

METHODS

Intravenously administered antisense oligodeoxynucleotide (ODN) is taken up by renal tubular epithelium and has been found to block expression of target genes in rats. MCP-1 antisense ODN was injected into GPS rats every second day from days 27 to 35 after immunization (this represents the time when renal MCP-1 mRNA level was increased and interstitial mononuclear cell infiltration was aggravated).

RESULTS

In addition to a reduction in the level of tubular MCP-1 mRNA, antisense ODN treatment attenuated monocyte infiltration significantly and preserved renal function in GPS rats. However, ODN injection did not affect glomerular MCP-1 expression and glomerular histopathology, and there were no significant changes in the urinary protein excretion rate.

CONCLUSION

Our findings provide direct evidence that MCP-1, expressed by tubular epithelium, plays a pivotal role in mediating secondary tubulointerstitial alterations in the GPS model.

Identification of alpha3, alpha4, and alpha5 chains of type IV collagen as alloantigens for Alport posttransplant anti-glomerular basement membrane antibodies

BACKGROUND

Alport syndrome is a hereditary disorder of basement membranes especially affecting the kidneys, ears, and eyes. Some patients who undergo renal transplantation lose their kidneys as a result of posttransplant anti-glomerular basement membrane (anti-GBM) disease.

METHODS

In the present study, we analyzed serum from 21 unselected Alport patients who underwent renal transplantation. Eleven samples were from patients without posttransplant anti-GBM nephritis, and 10 were from patients with this disease.

RESULTS

Thirteen serum samples [10 alport posttransplant nephritis serum (APTN) and three Alport posttransplant serum (APT)] revealed linear binding to the GBM by indirect immunofluorescence. By using direct ELISA and immunoblotting with GBM constituents and type IV collagen NC1 domains from bovine, human, and recombinant sources, we detected anti-GBM antibodies in all Alport patients in varying titers. Five samples showed specific reactivity to the alpha3 chain, four to the alpha5 chain, six to both alpha3 and alpha5 chains, one to the alpha3 and alpha4 chains, and two to the alpha3, alpha4, and alpha5 chains of type IV collagen. The varied spectrum of reactivities was present equally in nephritic and non-nephritic sera. Ten control samples from non-Alport transplant patients did not exhibit specific binding to the GBM.

CONCLUSIONS

These results suggest that the absence of alpha3, alpha4, and alpha5 chains of type IV collagen in the Alport kidney leads to alloantibodies in all Alport patients who receive transplants, irrespective of whether they develop nephritis or not. Although all Alport transplant patients develop this humoral response, only a select few develop anti-GBM disease. We suggest that this difference could be attributable to a genotypic effect on the ability of some individuals to launch a cell-mediated immune response.

Canstatin, a novel matrix-derived inhibitor of angiogenesis and tumor growth

We isolated and identified an endogenous 24-kDa human basement membrane-derived inhibitor of angiogenesis and tumor growth, termed canstatin. Canstatin, a fragment of the alpha2 chain of type IV collagen, was produced as a recombinant molecule in Escherichia coli and 293 embryonic kidneys cells. Canstatin significantly inhibited human endothelial cell migration and murine endothelial cell tube formation. Additionally, canstatin potently inhibited 10% fetal bovine serum-stimulated endothelial cell proliferation and induced apoptosis, with no inhibition of proliferation or apoptosis observed on non-endothelial cells. Inhibition of endothelial proliferation was not concomitant with a change in extracellular signal-regulated kinase activation. We demonstrate that apoptosis induced by canstatin was associated with a down-regulation of the anti-apoptotic protein, FLIP. Canstatin also suppressed in vivo growth of large and small size tumors in two human xenograft mouse models with histology revealing decreased CD31-positive vasculature. Collectively, these results suggest that canstatin is a powerful therapeutic molecule for suppressing angiogenesis.

Osteopontin expressed by renal tubular epithelium mediates interstitial monocyte infiltration in rats

In this study, we have shown that intravenously administered antisense oligodeoxynucleotide (ODN) was demonstrated to be taken up by tubular epithelium, after which it blocked mRNA expression of target genes in normal and nephritic rats. Therefore, we injected osteopontin (OPN) antisense ODN to Goodpasture syndrome (GPS) rats every second day between days 27 and 35, the time when renal OPN expression increased and interstitial monocyte infiltration was aggravated. In parallel to blockade of tubular OPN expression, this treatment significantly attenuated monocyte infiltration and preserved renal plasma flow in GPS rats at day 37, compared with sense ODN-treated and untreated GPS rats. No significant changes were observed in OPN mRNA level by RT-PCR and histopathology of the glomeruli after ODN treatment, which was compatible with an absence of differences in the urinary protein excretion rate. In conclusion, OPN expressed by tubular epithelium played a pivotal role in mediating peritubular monocyte infiltration consequent to glomerular disease.

Role for transforming growth factor-beta1 in alport renal disease progression

BACKGROUND

Alport syndrome results from mutations in either the alpha3(IV), alpha4(IV), or alpha5(IV) collagen genes. The disease is characterized by a progressive glomerulonephritis usually associated with a high-frequency sensorineural hearing loss. A mouse model for an autosomal form of Alport syndrome [collagen alpha3(IV) knockout] was produced and characterized. In this study, the model was exploited to demonstrate a potential role for transforming growth factor-beta1 (TGF-beta1) in Alport renal disease pathogenesis.

METHODS

Kidneys from normal and Alport mice, taken at different stages during the course of renal disease progression, were analyzed by Northern blot, in situ hybridization, and immunohistology for expression of TGF-beta1 and components of the extracellular matrix. Normal and Alport human kidney was examined for TGF-beta1 expression using RNase protection.

RESULTS

The mRNAs encoding TGF-beta1 (in both mouse and human), entactin, fibronectin, and the collagen alpha1(IV) and alpha2(IV) chains were significantly induced in total kidney as a function of Alport renal disease progression. The induction of these specific mRNAs was observed in the glomerular podocytes of animals with advanced disease. Type IV collagen, laminin-1, and fibronectin were markedly elevated in the tubulointerstitium at 10 weeks, but not at 6 weeks, suggesting that elevated expression of specific mRNAs on Northern blots reflects events associated with tubulointerstitial fibrosis.

CONCLUSIONS

The concomitant accumulation of mRNAs encoding TGF-beta1 and extracellular matrix components in the podocytes of diseased kidneys may reflect key events in Alport renal disease progression. These data suggest a role for TGF-beta1 in both glomerular and tubulointerstitial damage associated with Alport syndrome.

Angiotensin II induces alpha3(IV) collagen expression in cultured murine proximal tubular cells

Angiotensin II (ANG II) induces cellular hypertrophy of cultured proximal tubular cells from various species. This hypertrophic response is associated with an increase in synthesis of basement membrane-associated collagen type IV. Previous investigations by our group have shown that ANG II stimulates mRNA and protein expression of the "classic" alpha1 and alpha2(IV) chains in cultured murine proximal tubular cells (murine cortical tubules [MCT cells]). Since it is clearer today that kidney basement membranes also contain heterotrimers of novel type IV collagens, the aim of the present study was to evaluate whether ANG II may influence the expression of alpha3 and alpha5(IV) collagen chains in MCT cells. A single dose of 10-8-10-6 M ANG II stimulated mRNA expression of alpha3(IV), but not of alpha5(IV), in MCT cells cultured in serum-free media. This response was mediated through AT1-receptors because losartan, but not an AT2-receptor antagonist, abolished the ANG II-induced expression of alpha3(IV) transcripts. Transient transfection of MCT cells with transforming growth factor-beta1 (TGF-beta1) antisense phosphorothioate-modified oligonucleotides partly abolished the ANG II-induced alpha3(IV) mRNA expression. Furthermore, Western blots of cellular lysates incubated with polyclonal antibodies generated against the recombinant collagen chains revealed that ANG II stimulated alpha3(IV) but not alpha5(IV) protein expression. This stimulation was partly prevented by co-incubation with a neutralizing anti-TGF-beta1-3 antibody. In summary, our data indicate that ANG II stimulates expression of the alpha3(IV) collagen chain in cultured MCT cells, due in part to TGF-beta1 activation.

Rat amnion type IV collagen composition and metabolism: implications for membrane breakdown

We report here that rat amnion type IV collagens are composed primarily of alpha1(IV) and alpha2(IV) chains. Amnion basement membrane collagens were more sensitive to degradation by collagenases than were adult rat kidney basement membrane collagens, which are enriched in alpha3(IV), alpha4(IV), and alpha6(IV) chains. Amnion type IV collagen content per unit of protein was markedly reduced by Day 21 of pregnancy, the day of delivery. Increased amnion levels of matrix metalloproteinase (MMP)-2 and MMP-9, gelatinases that degrade type IV collagen, were found by Day 21, suggesting that collagen breakdown was responsible, in part, for the decline in amnion type IV collagen. Infection of organ cultures of Day 18 rat amnions with a recombinant adenovirus expressing MMP-9 (AdMMP-9) caused release of collagen fragments detected as hydroxyproline in the culture fluid, amnion cell detachment, and apoptosis. The AdMMP-9-induced apoptosis was prevented by the MMP inhibitor batimastat. These findings suggest that MMPs are implicated in anoikis and apoptotic death of amnion cells, and may be part of a complex program of fetal membrane remodeling that occurs before delivery.

Induction of matrix metalloproteinases and collagenolysis in chick embryonic membranes before hatching

The membranes surrounding the chick embryo undergo striking morphological changes before hatching, which include structural degradation of the allantoic membrane. The fibrillar collagen content of the membranes declined by embryonic day (ED) 20 (the day of hatching). By ED 19, a 55-kDa matrix metalloproteinase (MMP) activity appeared in the extraembryonic fluid, and by ED 20 there was substantial 55-kDa MMP activity in embryonic membrane extracts. Reverse transcription-polymerase chain reaction was employed to clone a partial cDNA representing the chicken homologue of MMP-13, a 55- to 57-kDa enzyme. MMP-13 mRNA dramatically increased in abundance in embryonic membranes by ED 19, reaching a peak on ED 20. Introduction of the MMP inhibitor batimastat into the extraembryonic fluid prevented the structural changes in the embryonic membranes before hatching. We conclude that, like mammalian fetal membranes, chick embryonic membranes undergo terminal remodeling before hatching, in part as a result of increased MMP activity. The chicken egg system represents a novel in vivo model for exploring biochemical events leading to embryonic membrane remodeling prior to birth and to test inhibitors of MMPs for their ability to prevent collagenolysis and fetal membrane rupture.

Experimental Goodpasture's syndrome in Wistar-Kyoto rats immunized with alpha3 chain of type IV collagen

BACKGROUND

Glomerulonephritis and lung hemorrhage of autoimmune Goodpasture syndrome develop due to immune reactions against epitope(s) of the non-collagenous (NC1) domain of alpha3-chain of type IV collagen [alpha3(IV) NC1]. Whether thymic mechanisms have a role in the loss of tolerance to the Goodpasture epitope has not been established. We studied the renal and pulmonary effects of immunization with different forms (monomer, dimer, or hexamer) of alpha3(IV) NC1 collagen in Wistar-Kyoto (WKY) rats, and assessed whether the intrathymic inoculation of the antigen may protect against anti-GBM disease.

METHODS

WKY rats were immunized with bovine alpha3(IV) monomer, dimer, or hexamer, or with alpha3(IV) NC1 synthetic peptide. Renal function, kidney and lung immunohistology, and circulating and tissue bound antibodies to type IV collagen chains were analyzed. Effects of intrathymic inoculation of antigen on subsequent disease induction were analyzed in WKY rats given alpha3(IV) NC1 dimer or GBM preparation intrathymically 48 hours before immunization.

RESULTS

Proteinuria, linear IgG deposition in GBM, and crescentic glomerulonephritis developed in WKY rats immunized with alpha3(IV) NC1 dimer or hexamer. Lesions were dose-dependent upon injections of 10 to 100 microgram dimer. The alpha3(IV) NC1 monomer induced less severe proteinuria and no crescents. Pulmonary hemorrhage was detectable in 35% of rats immunized with 25 to 100 microgram alpha3(IV) NC1 dimer; alpha3(IV) synthetic peptide (36 carboxyl terminal) did not induce disease. Rats injected intrathymically with up to 100 microgram alpha3(IV) NC1 dimer or with GBM 48 hours before immunization were not protected against subsequent development of proteinuria and glomerulonephritis.

CONCLUSIONS

These findings document that glomerulonephritis and lung hemorrhage can be elicited in WKY rats by immunization with alpha3(IV) NC1. Failure of the intrathymic inoculation of antigen to prevent disease suggests that immunological tolerance cannot be achieved by this intervention, in contrast to other autoimmune conditions, and may imply independent roles for cellular and humoral nephritogenic pathways in anti-GBM nephritis.

Augmented expression of glomerular basement membrane specific type IV collagen isoforms (alpha3-alpha5) in experimental membranous nephropathy

In human and experimental membranous nephropathy, new extracellular matrix accumulates between, and eventually surrounds, immune deposits on the subepithelial aspect of the glomerular basement membrane (GBM). To define the nature and source of this newly deposited matrix, we studied by in situ hybridization and immunohistology the production and tissue deposition of the recently defined basement membrane type IV collagen chain isoforms alpha3, alpha4, and alpha5, the mesangium-specific alpha1 and alpha2 isoforms of type IV collagen, and the fibrillar interstitial type I collagen during the development of immunological injury in passive Heymann nephritis (PHN), a rodent model of membranous nephropathy. Our results show that steady-state mRNA levels of alpha3-alpha5 (IV) but not alpha1 (IV) are significantly increased in the glomeruli of rats with PHN at the peak of immunological injury after 14 days. Increased signal for alpha4 (IV) and the new appearance of alpha1 (I) could be clearly localized to glomerular podocytes, the target of injury in this model. In addition, increased levels of immunoreactive alpha3-alpha5 were visible in the peripheral and paramesangial GBM together with de novo deposits of type I collagen. A modest increase in mesangial staining for alpha1/alpha2 (IV) was present in PHN glomeruli. In rats depleted of complement for 5 days after PHN induction, the peak of alpha4 (IV) mRNA expression on day 14 was blunted. In conclusion, we have shown increased production of the intrinsic GBM type IV collagen isoforms alpha3-alpha5 and ectopic production of type I collagen by injured podocytes in PHN. These changes may contribute to the formation of an expanded and disorganized GBM, as seen in experimental and human membranous nephropathy.

Human Goodpasture anti-alpha3(IV)NC1 autoantibodies share structural determinants

To examine the structural relationship among autoantibodies produced by individuals with anti-GBM antibody-mediated disease, a polyclonal anti-idiotype directed against human anti-alpha3(IV)NC1 antibodies was produced and then used to study autoantibodies from other patients. For this purpose, anti-alpha3(IV)NC1 antibodies (anti-GBM), derived from a single patient (LL) with high titer and typical anti-GBM antibody specificity, were isolated using recombinant alpha3(IV)NC1-sepharose affinity chromatography. Following hyperimmunization of rabbits with anti-GBM IgG, irrelevant rabbit anti-human IgG antibodies were removed from the antiserum using a human IgG-sepharose column. The rabbit anti-alpha3(IV)NC1 antibodies (anti-Id GBM) effluent bound to human anti-GBM antibodies, but it did not bind to either normal human IgG or recombinant alpha3(IV)NC1 protein. The Id-anti-Id interaction was conformationally dependent on intact heavy and light chains of the anti-alpha3(IV)NC1 antibodies (ELISA and Western blotting). A competitive immunoassay was developed to evaluate structural and potential genetic relationships among anti-alpha3(IV)NC1 antibodies from different patients. All patients tested (9 of 9) had a substantial fraction (producing > 50% inhibition) of anti-GBM antibodies expressing Id-GBM. The results indicate that shared determinants are expressed by anti-GBM antibodies from different individuals, and they raise the possibility that common genetic elements are used to encode them. These regions are potential targets for design of reagents to regulate autoreactive B cells and/or interfere with pathogenic antibody-GBM interactions, in individuals with anti-GBM antibody mediated diseases.

Goodpasture syndrome involving overlap with Wegener's granulomatosis and anti-glomerular basement membrane disease

A 68-year-old Caucasian woman presented to the hospital with nodular pulmonary infiltrates and acute renal failure. Wegener's granulomatosis was initially considered to be most likely because of the presence of increased serum levels of c-anti-neutrophil cytoplasmic antibodies (c-ANCA). A consultation through the Internet after a renal biopsy demonstrated crescentic, necrotizing glomerulonephritis and linear deposits of immunoglobulin G (IgG) and complement C3, typical of anti-glomerular basement membrane (GBM) disease. Hemodialysis was instituted; however, the patient suddenly developed a massive cerebral hemorrhage and died before full therapy could take effect. Postmortem analysis of the patient's sera revealed high titers of IgG against the alpha 3 NC1 domain of type IV collagen. Serologic evidence of both p-ANCA and anti-GBM antibodies are becoming more frequently recognized in the setting of rapidly progressive glomerulonephritis. The patient reported here had the unusual combination of c-ANCA antibodies with anti-GBM disease, and this association raises complex questions regarding the pathogenesis of this type of renal injury.

Susceptibility to anti-glomerular basement membrane disease and Goodpasture syndrome is linked to MHC class II genes and the emergence of T cell-mediated immunity in mice

We developed a new mouse model of human anti-glomerular basement membrane (GBM) disease to better characterize the genetic determinants of cell-mediated injury. While all major histocompatibility complex (MHC) haplotypes (H-2a, k, s, b, and d) immunized with alpha3 NC1 domains of type IV collagen produce anti-alpha3(IV) NC1 antibodies that cross-react with human Goodpasture [anti-GBM/anti-alpha3(IV) NC1] autoantibodies, only a few strains developed nephritis and lung hemorrhage associated with Goodpasture syndrome. Crescentic glomerulonephritis and lung hemorrhage were MHC-restricted in haplotypes H-2s, b, and d (A beta/A alpha region in H-2s) and associated with the emergence of an IL-12/Th1-like T cell phenotype. Lymphocytes or anti-alpha3(IV) NC1 antibodies from nephritogenic strains transfer disease to syngeneic recipients. However, passive transfer of isogenic alpha3(IV) NC1 antibodies into -/- T cell receptor-deficient mice failed to produce nephritis. Finally, nephritis and its associated IL-12/Th1-like T cell response attenuate in disease-susceptible mice tolerized orally to alpha3(IV) collagen before immunization. Our findings suggest collectively, as a hypothesis, that anti-GBM antibodies in mice only facilitate disease in MHC haplotypes capable of generating nephritogenic lymphocytes with special T cell repertoires.

Early role of Fsp1 in epithelial-mesenchymal transformation

A seamless plasticity exists among cells shifting between epithelial and mesenchymal phenotypes during early development and again later, in adult tissues, following wound repair or organ remodeling in response to injury. Fsp1, a gene encoding a fibroblast-specific protein associated with mesenchymal cell morphology and motility, is expressed during epithelial-mesenchymal transformations (EMT) in vivo. In the current study, we identified several cytokines that induce Fsp1 in cultured epithelial cells. A combination of these factors, however, was most efficacious at completing the process of EMT. The optimal combination identified were two of the cytokines classically associated with fibrosis, i.e., transforming growth factor-beta1 (TGF-beta1) and epidermal growth factor (EGF). To confirm that it was the induction of Fsp1 by these cytokines mediating EMT, we used antisense oligomers to block Fsp1 production and subsequently measured cell motility and markers of EMT phenotype. The antisense oligomers suppressed Fsp1 expresison and epithelial transformation; therefore, we conclude that the appearance of Fsp1 is an important early event in the pathway toward EMT.

The immunohistochemical composition of corneal basement membrane in keratoconus

PURPOSE

Keratoconus is a gradually progressing disease of unknown cause, characterized by central thinning, increased curvature, and finally scarring of the cornea. This causes myopia and astigmatism and the ultimate treatment is keratoplasty. We studied the composition of basement membranes (BMs) in normal, scarred and keratoconus corneas to find out possible changes specific for keratoconus.

METHODS

Frozen sections of normal, scarred and keratoconus corneas were immunostained with various antibodies against basement membrane (BM) proteins and integrin beta 4.

RESULTS

In the keratoconus corneas, we found discontinuities or defects in Bowman's layer, sometimes distorted stroma beneath the defects, and also thinning of the stroma. The results show that within the defects in keratoconus corneas, there is an expression of proteins that are not normally present in the corneal BM, i.e. collagen alpha 1/2 (IV) chains, and on the contrary, absence of the expression of some proteins, i.e. collagen alpha 5-6 (IV) chains that normally are continuously expressed in the corneal epithelial BM. In addition, either increased or decreased expression of laminin-1 (alpha 1 beta 1 gamma 1), laminin-5 (alpha 3 beta 3 gamma 2) and collagen type VII, depending on the keratoconus defect, was seen and the expression of integrin beta 4 was decreased. These findings seem to be specific for keratoconus, as they were not found in scarred corneas.

CONCLUSIONS

The results show that the defects in BM and changes in the BM composition are involved in the pathogenesis of keratoconus. Furthermore, it seems that scarring alone does not explain the breaks in Bowman's layer and immunohistochemical changes seen in keratoconus. Therefore, we suggest that a process similar to wound healing, which is initiated by breaks in Bowman's layer, would largely contribute to the differences seen in keratoconus corneas.

Seminiferous tubule basement membrane. Composition and organization of type IV collagen chains, and the linkage of alpha3(IV) and alpha5(IV) chains

Seminiferous tubule basement membrane (STBM) plays an important role in spermatogenesis. In the present study, the composition and structural organization of type IV collagen of bovine STBM was investigated. STBM was found to be composed of all six alpha-chains of type IV collagen based upon immunocytochemical and biochemical analysis. The content of alpha3(IV) chain (40%) and the alpha4(IV) chain (18%) was substantially higher than in any other basement membrane collagen. The supramolecular structure of the six alpha(IV) chains was investigated using pseudolysin (EC 3.4.24.26) digestion to excise triple-helical molecules, subsequent collagenase digestion to produce NC1 hexamers and antibody affinity chromatography to resolve populations of NC1 hexamers. The hexamers, which reflect specific arrangements of alpha(IV) chains, were characterized for their alpha(IV) chain composition using high performance liquid chromatography, two-dimensional electrophoresis, and immunoblotting with alpha(IV) chain-specific antibodies. Three major hexamer populations were found that represent the classical network of the alpha1(IV) and alpha2(IV) chains and two novel networks, one composed of the alpha1(IV)-alpha6(IV) chains and the other composed of the alpha3(IV)-alpha6(IV) chains. The results establish a structural linkage between the alpha3(IV) and alpha5(IV) chains, suggesting a molecular basis for the conundrum in which mutations in the gene encoding the alpha5(IV) chain cause defective assembly of the alpha3(IV) chain in the glomerular basement membrane of patients with Alport syndrome.

Expression of type IV collagen alpha1(IV)-alpha6(IV) polypeptides in normal and developing human kidney and in renal cell carcinomas and oncocytomas

Type IV collagen trimer is a major component of basement membranes (BMs). It is composed of polypeptides named alpha1(IV)-alpha6(IV) chains. Chains alpha1,2(IV) are widely expressed in BMs while alpha3(IV)-alpha6(IV) are more restricted in human tissues. We have now studied by immunohistochemical means the distribution of collagen IV chains in fetal and adult human kidney, in oncocytomas, in renal cell carcinomas (RCCs) and their metastases and in experimental xenografts of human tumors. alpha1,2(IV) chains were found in all BMs of fetal and adult kidney as well as of renal tumors, while alpha3(IV)-alpha6(IV) chains were found in BMs of distal segments of developing and mature tubules. alpha3(IV)-alpha5(IV) chains were seen also in BMs of developing fetal glomeruli after the capillary loop stage. Most of the RCCs and their metastases showed occasional expression of alpha3(IV)-alpha6(IV) with papillary variants showing only expression of alpha5(IV) chain. There was a distinct expression of alpha3(IV)-alpha5(IV) chains in BMs of 3 oncocytomas. In 2 of them a variable expression of the alpha6(IV) chain was seen. In 3 of 4 xenografts, immunoreactivity for human-specific monoclonal antibody (MAb) for alpha1,2(IV) was seen in the BM-like structures. No alpha3-alpha6(IV) was seen in any of the xenografts, while polyclonal antiserum for type IV collagen presented immunoreactivity in BMs of all xenografts. Our results show that oncocytomas and most of the RCCs express scarce variants of type IV collagen containing alpha3(IV)-alpha6(IV) chains. In experimental xenograft tumors, both implanted RCC cells and host stromal cells have a capacity to produce type IV collagen.

Isoform switching of type IV collagen is developmentally arrested in X-linked Alport syndrome leading to increased susceptibility of renal basement membranes to endoproteolysis

Normal glomerular capillaries filter plasma through a basement membrane (GBM) rich in alpha3(IV), alpha4(IV), and alpha5(IV) chains of type IV collagen. We now show that these latter isoforms are absent biochemically from the glomeruli in patients with X-linked Alport syndrome (XAS). Their GBM instead retain a fetal distribution of alpha1(IV) and alpha2(IV) isoforms because they fail to developmentally switch their alpha-chain use. The anomalous persistence of these fetal isoforms of type IV collagen in the GBM in XAS also confers an unexpected increase in susceptibility to proteolytic attack by collagenases and cathepsins. The incorporation of cysteine-rich alpha3(IV), alpha4(IV), and alpha5(IV) chains into specialized basement membranes like the GBM may have normally evolved to protectively enhance their resistance to proteolytic degradation at the site of glomerular filtration. The relative absence of these potentially protective collagen IV isoforms in GBM from XAS may explain the progressive basement membrane splitting and increased damage as these kidneys deteriorate.

Structural features of nephritogenic lupus autoantibodies

We have identified monoclonal antibodies derived from MRL-lpr/lpr lupus-prone mice that produced nephritis after passive transfer to normal mice. Our present goal was to elucidate the structural and immunochemical features of nephritogenic Ig that facilitate immune deposition. For this purpose the antigen binding properties, capacity to form immune deposits, and nucleotide sequence of a genetically related autoantibody subgroup were compared. The prototype, H147 (an IgG encoded by 7183/81X VH gene), produced glomerular and tubular basement membrane, mesangial immune deposits, and proliferative glomerulonephritis after passive transfer to normal mice. For comparison three other 7183/81X encoded anti-DNA IgG (H257, H171, and H8a) were evaluated (predicted heavy chain aa homology >75%). H257 produced similar types of immune deposits as H147, and this was associated with nephritis; H8a produced predominantly mesangial deposits, whereas H171 did not produce significant deposits. Although their antigen binding profile to a panel of soluble autoantigens was variable, only H147 and H257 bound to both mesangial and aortic endothelial cell surfaces. V gene sequence analysis of the IgG suggests that individual residues, motifs, and conformations influence the autoantigen binding specificities that contributed to the observed differences in immune deposit formation.