Combined AGE inhibition and ACEi decreases the progression of established diabetic nephropathy in B6 db/db mice

The accumulation of advanced glycation end products (AGE) is a key factor in diabetic nephropathy (DN). Pyridoxamine inhibits AGE formation and protects against type I DN. Herein we tested: (1) whether C57BL6 db/db mice as a model of established type II DN resembled patients treated with drugs which inhibit angiotensin II action; (2) whether pyridoxamine was effective as a single therapy; and (3) whether pyridoxamine would add to the benefit of angiotensin-converting enzyme inhibition (ACEi) by enalapril. In first set of experiments mice were treated with ACEi (benazepril) and an angiotensin II receptor blocker (valsartan) combination for 16 weeks after the onset of diabetes. In second group, mice with established DN were treated with pyridoxamine for 8 weeks. In a third set, mice with established DN were treated with pyridoxamine and enalapril combination for 16 weeks. Benazepril and valsartan combination partially prevented the development and progression of DN. Pyridoxamine treatment, as single therapy, decreased the progression of albuminuria and glomerular lesions. The combination of pyridoxamine with enalapril reduced both mortality and the progression of DN. In conclusion, (1) C57 BL6 db/db mice are a model of progressive type II DN; (2) The combination of pyridoxamine with enalapril decreased progression of type 2 DN and overall mortality. Thus, pyridoxamine could be a valuable adjunct to the current treatment of established type II DN.

Pentosan polysulfate decreases prostate smooth muscle proliferation and extracellular matrix turnover

Benign prostatic hyperplasia (BPH) involves proliferation of smooth muscle cells and increased deposition of extracellular matrix (ECM). We recently found that pentosan polysulfate (PPS) has marked effects on growth and ECM of smooth muscle cells derived from vascular tissues. We examined smooth muscle cells cultured from human prostates and the effects of PPS on their growth and ECM production. Fragments of surgical prostatectomy specimens were diced, digested with collagenase (0.01%), and placed in culture medium supplemented with 20% fetal bovine serum. Outgrowths of elongated cells were characterized by light microscopic examination and immunohistochemical techniques by the presence of F-actin, alpha-smooth muscle actin, and myosin, which is a characteristic of smooth muscle cells. Two independent isolates were propagated, and growth curves and ECM production were assessed in the presence and absence of PPS (10 or 100 microg/ml). PPS decreased cell number beginning at day 1 and throughout the incubation period, up to 4 days. The amount of the ECM degradative enzymes, metallo-proteinases MMP-9 and MMP-2, was examined by zymography. PPS did not alter the amount of MMP-2 in the supernatants but MMP-9 was increased 234.4 +/- 17.23-fold over control cells. Tissue inhibitor of MMP (TIMPS), examined by reverse zymography, increased 200% over control. The amount of alpha I type (IV) and alpha I type (I) collagen released in the supernatant, measured by ELISA, significantly decreased in PPS-treated cultures. In conclusion, we found that the administration of PPS decreased proliferation as well as ECM production in prostate smooth muscle. Since smooth muscle proliferation and ECM are involved in the pathophysiology of BPH, PPS may have therapeutic potential.

Glomerulosclerosis is transmitted by bone marrow-derived mesangial cell progenitors

We found that ROP Os/+ (Os/+) mice had diffuse glomerulosclerosis and glomerular hypertrophy and that their mesangial cells (the vascular smooth muscle cells of the glomerulus) displayed an apparent sclerosing phenotype. Since mesangial cells are the major source of scar tissue in glomerulosclerosis, we postulated that the sclerosis phenotype was carried by mesangial cell progenitors and that this phenotype could be derived from the bone marrow (BM). Therefore, we transplanted BM from Os/+ mice into congenic ROP +/+ mice (+/+ mice), which have normal glomeruli. We found that glomeruli of +/+ recipients of Os/+ marrow contained the Os/+ genotype, were hypertrophied, and contained increased extracellular matrix. Clones of recipient glomerular mesangial cells with the donor genotype were found in all +/+ recipients that developed mesangial sclerosis and glomerular hypertrophy, whereas +/+ recipients of +/+ BM had normal glomeruli. Thus, the sclerotic (Os/+) or normal (+/+) genotype and phenotype were present in, and transmitted by, BM-derived progenitors. These data show that glomerular mesangial cell progenitors are derived from the BM and can deliver a disease phenotype to normal glomeruli. Glomerular lesions may therefore be perpetuated or aggravated, rather than resolved, by newly arriving progenitor cells exhibiting a disease phenotype.

N-phenacylthiazolium bromide decreases renal and increases urinary advanced glycation end products excretion without ameliorating diabetic nephropathy in C57BL/6 mice

AIMS

Advanced glycation end products (AGE), which form from the non-enzymatic reaction of proteins and sugars, have been implicated in the pathogenesis of diabetic nephropathy. Recently, a compound [N-phenacylthiazolium bromide (PTB)] has been described which cleaves alpha,beta-dicarbonyl compounds. In the present study we used diabetic C57BL/6 mice to determine if PTB altered renal AGE levels and reduced diabetic glomerulosclerosis.

METHODS

Mice with stable hyperglycaemia induced by streptozotocin were given daily subcutaneous injections of either PTB (10 microg/g) or saline for 12 weeks. Renal-collagen bound AGE and urinary AGE-peptides were measured by ELISA using an anti-AGE-RNase antibody. Renal collagen-released Nepsilon(carboxymethyl)lysine (CML) and pentosidine were determined by high pressure liquid chromatography (HPLC). Glomerular lesions (volume and mesangial/total surface area) were evaluated by computer-assisted image analysis. We determined urinary protein/creatinine ratio as a functional parameter. AGE localization was examined by immunohistochemistry using the anti-AGE-RNase antibody.

RESULTS

Renal collagen-bound AGE were decreased and urinary AGE excretion was increased in PTB-treated diabetic mice. However, collagen-released CML and pentosidine were similar in both groups. Glomerular histology and morphometric analysis revealed also no differences between PTB-and saline-treated diabetic mice. The urinary protein/creatinine ratio was unaffected by PTB-treatment. AGE staining by anti-AGE-RNase antibody was present in Bowman's capsules, glomerular basement membranes and cortical tubules. It was decreased in all structures in PTB-treated diabetic mice.

CONCLUSION

In summary, PTB decreased renal AGE accumulation but did not ameliorate glomerular lesions or proteinuria. Thus, cleavage of AGE by PTB is not sufficient to prevent development of diabetic nephropathy in C57BL/6 mice.

Low-protein diet suppresses serum insulin-like growth factor-1 and decelerates the progression of growth hormone-induced glomerulosclerosis

A low-protein (LP) diet has been associated with amelioration of renal function in glomerulosclerosis (GS). However, the mechanisms involved are still unclear. We have used a mouse transgenic for bovine growth hormone (GH), which develops progressive GS and exhibits consistently elevated levels of circulating GH and insulin-like growth factor (IGF)-1, to study the effect of dietary protein restriction. LP (6% protein) and normal-protein (NP, 20% protein) diets were maintained for 30 weeks in mice with established GS of mild/moderate degree. The degree of GS was markedly attenuated in LP compared to NP mice. Quantitative analysis revealed a significantly lower GS index (1.4 +/- 0.9 in LP vs. 2.8 +/- 0.8 in NP) and glomerular volume (0.8 x 10(6) +/- 0.1 x 10(6) microm(3) in LP vs. 1.2 x 10(6) +/- 0.1 x 10(6) microm(3) in NP) in mice with restricted protein intake. These morphologic changes were accompanied by a significant reduction in renal expression of alpha(1) type-IV collagen (2.4-fold) and tenascin (1.4-fold) in LP mice. Serum IGF-1 decreased by 40% and showed a significant correlation with alpha(1) type-IV collagen expression with the LP diet. The present finding supports the use of the LP diet to decelerate the progression of GS and furthermore suggests that one of the mechanisms involved in this process is the GH/IGF-1 regulation by protein intake.

Analysis of glomerulosclerosis and atherosclerosis in lecithin cholesterol acyltransferase-deficient mice

To evaluate the biochemical and molecular mechanisms leading to glomerulosclerosis and the variable development of atherosclerosis in patients with familial lecithin cholesterol acyl transferase (LCAT) deficiency, we generated LCAT knockout (KO) mice and cross-bred them with apolipoprotein (apo) E KO, low density lipoprotein receptor (LDLr) KO, and cholesteryl ester transfer protein transgenic mice. LCAT-KO mice had normochromic normocytic anemia with increased reticulocyte and target cell counts as well as decreased red blood cell osmotic fragility. A subset of LCAT-KO mice accumulated lipoprotein X and developed proteinuria and glomerulosclerosis characterized by mesangial cell proliferation, sclerosis, lipid accumulation, and deposition of electron dense material throughout the glomeruli. LCAT deficiency reduced the plasma high density lipoprotein (HDL) cholesterol (-70 to -94%) and non-HDL cholesterol (-48 to -85%) levels in control, apoE-KO, LDLr-KO, and cholesteryl ester transfer protein-Tg mice. Transcriptome and Western blot analysis demonstrated up-regulation of hepatic LDLr and apoE expression in LCAT-KO mice. Despite decreased HDL, aortic atherosclerosis was significantly reduced (-35% to -99%) in all mouse models with LCAT deficiency. Our studies indicate (i) that the plasma levels of apoB containing lipoproteins rather than HDL may determine the atherogenic risk of patients with hypoalphalipoproteinemia due to LCAT deficiency and (ii) a potential etiological role for lipoproteins X in the development of glomerulosclerosis in LCAT deficiency. The availability of LCAT-KO mice characterized by lipid, hematologic, and renal abnormalities similar to familial LCAT deficiency patients will permit future evaluation of LCAT gene transfer as a possible treatment for glomerulosclerosis in LCAT-deficient states.

Cyclosporin A affects extracellular matrix synthesis and degradation by mouse MC3T3-E1 osteoblasts in vitro

BACKGROUND

Immunosuppressant therapy is thought to be a major contributor to post-transplant bone disease. Histological data and serum parameters suggest that Cyclosporin A (CsA) treatment causes osteopenia as a result of an altered bone turnover, but the pathogenic mechanisms of this process remain unclear. We investigate if CsA affects cell turnover and extracellular matrix (ECM) synthesis and degradation in MC3T3-E1 osteoblasts, as a surrogate model for in vivo events.

METHODS

Cells were exposed to increasing doses of CsA (0, 0.5, 1 and 5 microg/ml). Proliferation was evaluated by bromodeoxyuridine (BrdU) incorporation, viability by Trypan Blue exclusion and apoptosis by ELISA. Type I collagen was measured by ELISA and reverse transcription-polymerase chain reaction (RT-PCR), matrix metalloproteinases (MMP) by zymography and RT-PCR, and tissue inhibitors of MMP (TIMP) by reverse zymography.

RESULTS

CsA exposure for 48 h decreased osteoblast number in a dose-dependent manner in the absence of apoptosis or cytotoxicity. CsA at a dose of 5 microg/ml for 72 h caused decreased collagen type I mRNA expression and protein accumulation. While MMP-2 remained unaffected, MMP-9 activity increased. TIMP-1 activity was unaffected, while a dose-dependent increase of TIMP-2 was observed.

CONCLUSIONS

These data suggest that CsA alters ECM synthesis and degradation in MC3T3-E1 osteoblasts by decreasing type I collagen production and increasing MMP-9 activity. The combination of increased MMP-9 with unchanged TIMP-1 activity could reduce the osteoid matrix available for mineralization. In addition, decreased proliferation could further reduce the number of cells synthesizing new osteoid matrix and thus contribute to the process of bone loss.

Hepatocyte growth factor, but not insulin-like growth factor I, protects podocytes against cyclosporin A-induced apoptosis

Cyclosporin A (CsA) nephropathy is associated with altered expression of apoptosis regulatory genes such as Fas-ligand and Bcl-2 family members in the glomerular, tubulointerstitial, and vascular compartments. Both hepatocyte growth factor (HGF) and insulin-like growth factor (IGF-I) protect against apoptosis, and HGF specifically up-regulates Bcl-xL, a protein that regulates apoptosis. We investigated whether Bcl-xL and Fas/Fas-ligand were regulated by CsA in cultured podocytes and whether CsA-induced apoptosis was prevented by HGF or IGF-I. A murine podocyte cell line was treated with CsA in the presence or absence of HGF or IGF-I. Apoptosis was quantitated by ELISA and by flow cytometry; Bcl-xL, Fas, and Fas-ligand were measured by Western blotting. Inhibitors of MAP kinase/ERK kinase (MEK)-1 and of phosphatidylinositol 3'-kinase (PI3'-K) were used to determine the signaling pathways involved in Bcl-xL regulation. Apoptosis was induced by CsA in a dose- and time-dependent fashion. CsA also decreased Bcl-xL levels. HGF, but not IGF-I, prevented apoptosis and restored Bcl-xL levels. The regulation of Bcl-xL by HGF was mediated by the PI3'-K but not by the MEK-1 pathway. In summary, we showed that CsA induces apoptosis in podocytes. Apoptosis was prevented by pretreatment with HGF but not IGF-I. Decreased apoptosis appeared to be mediated by regulation of Bcl-xL via the PI3'-K pathway. Our data suggest that the effect of CsA on podocytes may contribute to the glomerular damage and that HGF could provide protection.

Matrix accumulation in mesangial cells exposed to cyclosporine A requires a permissive genetic background

BACKGROUND

Chronic nephrotoxicity is an important adverse effect of cyclosporine A (CsA) therapy. Tubulo-interstitial lesions and arteriolopathy are common histologic findings. Glomerular lesions are also described, but they are of variable severity. The aim of our study is to determine whether CsA has a direct effect on mesangial cells and whether the cellular response depends on the genetic background.

METHODS

We studied mesangial cells isolated from mice susceptible (ROP/Le-+Es1(b)+Es1(a), ROP) and resistant to glomerulosclerosis (B6SJLF1, C57). We previously showed that sclerosis-prone and sclerosis-resistant phenotypes are maintained in vitro. We examined whether CsA exposure directly affected extracellular matrix turnover in mesangial cells and whether the response is determined by the genetic background. Extracellular matrix synthesis and degradation were studied by proline incorporation, ELISA, reverse transcription-polymerase chain reaction, zymography, and reverse zymography. We chose a CsA dose that induced neither cytotoxicity nor apoptosis (1 microg/ml).

RESULTS

At the dose of 1 microg/ml total collagen accumulation was increased in ROP but not in C57 cells. Matrix metalloproteinase (MMP)-2 activity and mRNA levels were selectively decreased in ROP cells. CsA exposure did not affect tissue inhibitors of MMP (TIMP)-1 and -2 activity or TGF-beta1 mRNA expression and protein synthesis in either cell line.

CONCLUSION

CsA increases total collagen accumulation in mesangial cells from sclerosis-prone mice by decreasing MMP-2 activity, but does not affect cells from sclerosis-resistant mice. Thus, CsA directly affects mesangial cells, but only those with a permissive genetic background for glomerulosclerosis.

Pentosan polysulfate decreases proliferation and extracellular matrix deposition by vascular smooth muscle cells isolated from failed hemodialysis access grafts

BACKGROUND

Vascular access failure is a major cause of morbidity, and increased costs in patients undergoing maintenance hemodialysis. Stenosis, the most common underlying cause of loss of patency in failed grafts, appears to be caused by an obstructing mass of tissue containing proliferating smooth muscle cells and their associated extracellular matrix.

METHODS

To determine whether this process was amenable to pharmacologic intervention and/or prevention, we obtained samples of the material occluding vascular accesses from 7 patients undergoing revision surgery in order to characterize the cells contributing to the stenosis. In all 7 patients the outgrowth contained predominantly smooth muscle-like cells admixed with fibroblasts, which produced a large amount of type IV and type I collagen.

RESULTS

Treatment with pentosan polysulfate inhibited cell proliferation and significantly reduced the accumulation of types I and type IV collagens. This was associated with increase in metalloproteinase-9 (MMP-9) and a shift of tissue inhibitor of metalloproteinase-3 (TIMP-3) from the cell layer into the medium.

CONCLUSION

These data suggest that pentosan polysulfate (PPS) may have a favorable effect in patients with a polytetrafluoroethylene (PFTE) graft by decreasing cell proliferation and collagen deposition.

FK409, a spontaneous nitric oxide releaser, attenuates allograft vasculopathy in a rat aortic transplant model

Although systemic administration of NO donors has been shown to attenuate the development of neointimal hyperplasia in the balloon injury model, this strategy has not been tested in a model of allograft vasculopathy. In this study, we investigated the effect of FK409, a spontaneous NO releaser, on the development of allograft vasculopathy, using a rat aortic transplant model. Thoracic aortas from ACI rats were transplanted heterotopically into the abdominal aorta of Wistar-Furth rats. Postoperatively, recipients received FK409 orally every 8 hours from the day of transplantation to the time of euthanization. Morphometric and immunohistochemical analyses were performed on the aortic grafts 8 weeks after transplantation. Control allografts showed severe neointimal hyperplasia, which consists mainly of alpha-actin-containing vascular smooth muscle cells. The FK409-treated allografts showed a dose-dependent reduction (statistically significant compared with the control) in the neointimal thickness as the dose increased from 1 to 10 mg/kg (thrice per day). However, there was no significant difference in the neointimal thickness between groups treated with 10 and with 20 mg/kg. FK409 treatment (10 mg/kg) caused a significant decrease in DNA synthesis (5-bromo-2-deoxyuridine [BrdU] uptake), an increase in DNA fragmentation (terminal deoxynucleotidyltransferase-mediated uridine nick-end labeling [TUNEL]), and upregulation of Fas expression, in the neointimal vascular smooth muscle cells. These data suggest that FK409 attenuates the allograft vasculopathy in a rat aortic transplant model.

Glomerulosclerosis in mice transgenic for human insulin-like growth factor-binding protein-1

BACKGROUND

The growth hormone (GH)/insulin-like growth factor (IGF) system is thought to participate in the glomerulosclerosis process. Because IGF-binding proteins (IGFBPs) modulate IGF actions and hence GH secretion, this study assessed whether mice transgenic for human IGFBP-1 have altered susceptibility to glomerulosclerosis.

METHODS

A line of transgenic mice that express human IGFBP-1 mRNA in the liver under the control of the alpha1-antitrypsin promoter has been obtained, and morphological changes in the kidney tissue were assessed. Glomerulosclerosis was identified using light microscopy, light microscopic morphometry, and electron microscopy. Extracellular matrix components were analyzed by immunohistochemistry.

RESULTS

There was a marked increase in mesangial extracellular matrix area in homozygous transgenic mice at three months of age as compared with heterozygous transgenic mice and nontransgenic littermates. These changes were not associated with alterations in glomerular volume or cellularity. The expansion of extracellular matrix area was related to a marked increase in laminin and type IV collagen and to the appearance of type I collagen.

CONCLUSIONS

These observations indicate that the enhanced expression of IGFBP-1 may result in the development of glomerulosclerosis without glomerular hypertrophy. The changes are potentially related to a decrease in IGF-I availability and/or to an IGF-I-independent role of IGFBP-1.

Protection against diabetes-induced nephropathy in growth hormone receptor/binding protein gene-disrupted mice

To further investigate the role of GH in diabetic nephropathy, experimental diabetes was induced with streptozotocin (STZ) in mice in which the GH receptor/binding protein gene was disrupted. Body weight, blood glucose, and renal histology and morphometry were studied 10 weeks after diabetes induction in wild-type (+/+) mice and in mice heterozygous (+/-) and homozygous (-/-) for the disruption. Equivalent levels of hyperglycemia developed in all diabetic groups. Normal weight gain was absent in +/+ and +/- diabetic groups, and -/- diabetics lost weight during the study. Diabetic +/+ and +/- groups both showed evidence of glomerulosclerosis, increases in glomerular volume, and increases in the ratio of mesangial area to total glomerular area, whereas diabetic -/- mice showed none of these pathological changes. These results extend our previous findings of protection against diabetes-associated kidney damage in transgenic mice expressing a GH antagonist. Taken together, the results argue for an important role of GH in the development of diabetes induced end-organ damage.

Pentosan polysulfate treatment reduces cyclosporine-induced nephropathy in salt-depleted rats

BACKGROUND

Long-term cyclosporine (CsA) treatment leads to a decreased glomerular filtration rate, hyalinosis of afferent arterioles, and striped cortical tubulo-interstitial fibrosis. We showed previously that pentosan polysulfate (SP54) prevented the development of microvascular and interstitial lesions in mouse models of progressive glomerulosclerosis. In this study, we examined the effect of pentosan polysulfate on the development of CsA nephropathy.

METHODS

Pair-fed Sprague-Dawley rats were fed a low-sodium (0.03%) diet and received CsA (15 mg/kg, subcutaneously, in olive oil)/5% glucose, pentosan polysulfate (10 mg/kg, subcutaneously in 5% glucose) plus CsA, olive oil/pentosan polysulfate, or olive oil/5% glucose for 30 days. Creatinine clearance (CrCl) was determined at three time points. Afferent arteriolar lesions, glomerular volume, and tubulo-interstitial lesions were quantitated. RNA was extracted from cortex.

RESULTS

Severe lesions were found in the CsA group. A reduction in the number of affected arterioles (32%) and the degree of chronic tubulo-interstitial lesions (44%) was found in pentosan polysulfate/CsA-treated rats. A 20% decrease in glomerular volume was found in CsA rats, but not in pentosan polysulfate/CsA-treated rats. Pentosan polysulfate treatment did not prevent the CsA-induced decrease in CrCl (approximately 30%) at 4 weeks. CsA did not affect cortical endothelial or neuronal nitric-oxide synthase or mRNA levels, but there was small increase in neuronal nitric-oxide synthase mRNA levels in the pentosan polysulfate/CsA-treated group.

CONCLUSIONS

Pentosan polysulfate reduced structural renal lesions in CsA-treated, salt-depleted Sprague-Dawley rats.

Nephrotoxin exposure in utero reduces glomerular number in sclerosis-prone but not sclerosis-resistant mice

BACKGROUND

We have previously found that nephron number was not fixed, that is, there was a direct correlation between low birth weight and decreased nephron number in infants. In sclerosis-prone rats, we found that gentamicin exposure in utero induced a reduction in glomerular number and aggravated glomerulosclerosis in adults. In mice, we found that an inborn 50% reduction in nephron number, caused by the Os mutation, was associated with glomerulosclerosis in sclerosis-prone (ROP+/+) mice, but not in sclerosis-resistant (C57BL/6J) mice. Because the genetic background determined the response to decreased nephron number, we asked whether the susceptibility changes in glomerular number and glomerulosclerosis were linked.

METHODS

Gentamicin was administered before and after the onset of fetal nephrogenesis. (1) Prior to the onset of nephrogenesis, two groups of pregnant mice were treated from embryonic day (E) E8 to E12. In group A, early glomerular development was studied by placing ureteric ridges removed on E12 in vitro for four days, following which the ureteric bud branches and glomeruli were counted using lectin staining. In group B, nephron number was determined in spontaneously delivered 14-day-old (14PN) pups by counting glomeruli. (2) After the onset of nephrogenesis, to determine the direct effects of gentamicin on nephron induction, ureteric ridges were placed in organ culture at E12 of normal gestation, in the presence or absence of gentamicin. The number of glomeruli and ureteric bud branches were counted after six days in culture.

RESULTS

A decrease in glomerular number and ureteric bud branches was observed in sclerosis-prone (ROP+/+) mice, irrespective of whether gentamicin was administered prior to or after the onset of nephrogenesis. Glomerular number and ureteric bud branching were not decreased by gentamicin in sclerosis-resistant (C57BL/6) mice.

CONCLUSIONS

These data provide evidence that there is a positive correlation between the susceptibility to glomerulosclerosis in adulthood and a reduction in nephron number in utero. Thus, exposure to nephrotoxins in utero compounds the risk of renal failure as an adult in sclerosis-prone individuals.

IGF-1 decreases collagen degradation in diabetic NOD mesangial cells: implications for diabetic nephropathy

Nonobese diabetic (NOD) mice develop glomerulosclerosis shortly after the onset of diabetes. We showed that mesangial cells (MCs) from diabetic mice exhibited a stable phenotypic switch, consisting of both increased IGF-1 synthesis and proliferation (Elliot SJ, Striker LJ, Hattori M, Yang CW, He CJ, Peten EP, Striker GE: Mesangial cells from diabetic NOD mice constitutively secrete increased amounts of insulin-like growth factor-I. Endocrinology 133:1783-1788, 1993). Because the extracellular matrix (ECM) accumulation in diabetic glomerulosclerosis may be partly due to decreased degradation, we examined the effect of excess IGF-1 on collagen turnover and the activity of metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) in diabetic and nondiabetic NOD-MC. Total collagen degradation was reduced by 58 +/- 18% in diabetic NOD-MCs, which correlated with a constitutive decrease in MMP-2 activity and mRNA levels, and nearly undetectable MMP-9 activity and mRNA. TIMP levels were slightly decreased in diabetic NOD-MC. The addition of recombinant IGF-1 to nondiabetic NOD-MC resulted in a decrease in MMP-2 and TIMP activity. Furthermore, treatment of diabetic NOD-MC with a neutralizing antibody against IGF-1 increased the latent form, and restored the active form, of MMP-2. In conclusion, the excessive production of IGF-1 contributes to the altered ECM turnover in diabetic NOD-MC, largely through a reduction of MMP-2 activity. These data suggest that IGF-1 could be a major contributor to the development of diabetic glomerulosclerosis.

Nature and severity of the glomerular response to nephron reduction is strain-dependent in mice

Nephron reduction is an important factor in the development of glomerulosclerosis. In a study of the oligosyndactyly (Os) mutation that causes a congenital 50% reduction in nephron number, we previously found that ROP Os/+ mice developed glomerulosclerosis whereas C57B1/6J Os/+ mice did not. We concluded that the predisposition to glomerulosclerosis depended largely on the genetic background, the ROP being sclerosis-prone whereas the C57 strain was sclerosis-resistant. In the current experiments we asked whether the intensity of the sclerotic response to nephron reduction in the ROP strain was related to the time at which it occurred, ie, a pre- or post-natal event. We also determined whether the absence of lesions in C57 Os/+ mice was caused by a higher threshold for the induction of a sclerotic response in C57 mice. We further examined the relationship between glomerular hypertrophy and sclerosis. C57 +/+, C57 Os/+, ROP +/+, and ROP Os/+ mice were uninephrectomized (NX) at age 10 weeks and followed for 8 weeks. We found no sclerotic changes in NX C57 +/+ and C57 Os/+ mice, despite a 75% reduction in nephron number in the latter. In contrast, both NX ROP +/+ and NX ROP Os/+ mice had glomerulosclerosis, which was more severe in the NX ROP Os/+ mice. Examination of extracellular matrix synthesis and degradation at the mRNA level revealed that synthesis exceeded degradation in ROP Os/+ mice. The lesions in NX ROP +/+ were less severe than in sham-operated ROP/Os mice, suggesting that the timing of nephron reduction affected the amplitude of the sclerotic response in this strain. Following NX, an increase in glomerular volume was found in C57 +/+, ROP +/+, and ROP Os/+ mice. However, NX did not lead to a further increase in glomerular volume in C57 Os/+ mice. We make three conclusions: 1) sclerosis was more severe in the ROP strain when nephron reduction occurred in utero; 2) the absence of glomerulosclerosis in C57 mice was not related to a higher threshold for a sclerosis response in this strain; and 3) whereas glomerular size continued to increase as nephron number decreased in ROP mice, it reached a plateau in C57 mice.

Pentosan polysulfate decreases proliferation and net extracellular matrix production in mouse mesangial cells

Glomerulosclerosis is characterized by extracellular matrix accumulation and is often associated with mesangial cell proliferation. Heparin-like molecules have been shown to decrease glomerulosclerosis in vivo, although their cellular site and mechanism of action is still unclear. In this study, a line of glomerular mesangial cells derived from normal mice was used to determine whether pentosan polysulfate (PPS) inhibited proliferation and altered extracellular matrix turnover. Cells treated with PPS showed a decrease in cell number beginning 24 h after treatment, which was maintained for 5 d. For matrix accumulation and degradation studies, cells were treated for 5 d and collagen types I and IV protein were measured by enzyme-linked immunosorbent assay as well as matrix metalloproteinases (MMP) measured by zymography. Collagen types 1 and type IV were significantly decreased in the media (P < 0.0001) and cell layer (P < 0.005) after treatment with PPS but not after treatment with heparin. By zymography, MMP-2 was significantly increased after treatment with PPS (P < 0.001) and heparin (P < 0.05). PPS and heparin also decreased MMP-9 (P < 0.001) after treatment. Reverse zymography showed the presence of tissue inhibitors of metalloproteinases (TIMP)-1 and -2 in control mesangial cells. Treatment with PPS and heparin increased TIMP-1. In addition, TIMP-3 was found in the medium of treated but not control cells. In conclusion, PPS alters extracellular matrix turnover through the induction of MMP-2 and alterations in the TIMP profile and may be useful in decreasing progressive glomerulosclerosis.

The inheritance of glomerulosclerosis in mice is controlled by multiple quantitative trait loci

BACKGROUND

Glomerulosclerosis, the common terminal event in chronic glomerular diseases such as diabetic nephropathy or IgA nephropathy, leads to end-stage renal disease. The considerable variation in both the risk of developing glomerulosclerosis and the rate of progression in individual patients suggest a role for genetic factors which have not been identified so far. In this study we sought to examine the mode of inheritance of glomerulosclerosis in mice.

METHODS

F1 animals of a mating between glomerulosclerosis-prone ROP-Os/+ male and non-sclerotic C3H female mice were backcrossed to the ROP strain. We took advantage of the radiation-induced mutation oligosyndactylism (Os) to identify glomerulosclerosis at the age of 3 months. Kidneys were perfused in situ with PBS/Formalin 10%. The extent of glomerulosclerotic lesions was evaluated on PAS stained paraffin sections using computer-aided morphometry.

RESULTS

F1 mice did not show any glomerulosclerosis. In the backcross offspring, we found a wide distribution of glomerular lesions between individual animals, ranging from normal to very severe. We calculated that at least 8-10 loci determine the severity of glomerulosclerosis in mice.

CONCLUSIONS

Our data show that glomerulosclerosis is inherited in a recessive fashion involving at least 8-10 loci.

Strain differences rather than hyperglycemia determine the severity of glomerulosclerosis in mice

BACKGROUND

We reported that ROP, but not C57, mice were prone to glomerulosclerosis (GS) after nephron reduction (J Clin Invest 97:1242, 1996).

METHODS

In this study, we induced diabetes in ROP and C57 mice to determine if the glomerulosclerotic response was stimulus specific. We used the oligosyndactyly mutation (Os), to produce a congenital 50% reduction in nephron number. Stable hyperglycemia was induced by streptozotocin and mice were maintained for 12 weeks without insulin treatment.

RESULTS

Glomerular hypertrophy occurred in diabetic ROP +/+ and C57 +/+ mice, but glomeruli of diabetic ROP +/+ mice had 1.92-fold higher laminin B1 and 1.5-fold higher tenascin mRNA levels than diabetic C57 +/+ mice. Diabetic ROP Os/+ mice had severe glomerulosclerosis with arteriolar and tubulointerstitial lesions while there was only moderate mesangial sclerosis in diabetic C57 Os/+ mice. Glomerular size was increased in all non-diabetic Os/+ mice. It was further increased in diabetic ROP Os/+ mice, but not in diabetic C57 Os/+ mice. Glomerular mRNA levels were higher in diabetic ROP OS/+ than in diabetic C57 OS/+ mice [alpha 1 (i.v.) collagen 3.2-fold, laminin B1 2.1-fold, and tenascin 1.6-fold].

CONCLUSION

Overall, our data further support the hypothesis that the susceptibility to glomerulosclerosis is inherited, and suggest that hyperglycemia serves principally as a triggering event in the development of diabetic nephropathy. Since the acceleration of diabetic nephropathy by nephron reduction was also largely strain dependent, it appears that the propensity to glomerulosclerosis is a general renal response and is not stimulus specific.

Glomerular endothelial cells synthesize collagens but little gelatinase A and B

Mesangial sclerosis is a major feature of progressive renal disease. The mesangium contains mesangial cells and is bounded by the peripheral glomerular basement membrane and endothelial cells. Mesangial cells synthesize and degrade extracellular matrix. Whereas both mesangial and endothelial cells synthesize extracellular matrix components, the degradative pathway, well studied in the former, has not been investigated in endothelial cells. This study examines lines of all three glomerular cell types derived from female B6SJLF1/J mice, as well as mRNA levels for collagens alpha1(I), alpha1(IV), alpha3 (IV), alpha5 (IV), and alpha1 (VI), laminin, tenascin, matrix metalloproteinase-2 (MMP-2), and MMP-9. Type I and IV collagen synthesis was confirmed by enzyme-linked immunosorbent assay. MMP-2 and MMP-9 enzyme activity was measured by zymography. It was found that glomerular endothelial cells are a significant source of collagens, laminin, and tenascin. However, they express only low levels of MMP-2 and no detectable MMP-9. Stimulation with exogenous transforming growth factor-beta1 leads to a significant increase in collagen I, tissue inhibitors of metalloproteinase-1, and MMP-9 in conditioned media. These data suggest that glomerular endothelial cells may play an active role in extracellular matrix remodeling in glomerular disease.

Glomerulosclerosis, arteriosclerosis, and vascular graft stenosis: treatment with oral heparinoids

At present there is no known treatment for established glomerulosclerosis or atherosclerosis. Since the principal lesion in glomerulosclerosis involves mesangial cells, a vascular smooth muscle cell, we searched for new therapeutic approaches affecting vascular smooth muscle function, especially with respect to modifying the turnover of extracellular matrix. We used mice transgenic for bovine growth hormone (bGH), since these mice develop end-stage renal disease due to progressive glomerulosclerosis. We previously showed that the subcutaneous injection of a non-anticoagulant heparin reduced glomerulosclerosis in bGH mice. Since injectable drugs are not a practical means of controlling glomerulosclerosis in humans, we assessed oral heparin-like compounds and found that oral pentosan polysulfate (PPS) reduced glomerulosclerosis in bGH mice at non-toxic doses. Because the positive therapeutic response in the bGH model could have been principally hormone-mediated, we examined other models of non-immune mediated glomerulosclerosis, including ROP Os/+ non-diabetic and diabetic mice. We found that an oral PPS (Elmiron), which is approved for other indications in humans, reduced sclerosis in all of these forms of chronic, progressive glomerulosclerosis. Based on the similarity of the cellular events in glomerulosclerosis and arteriosclerosis, we assessed the effect(s) of PPS in congenital (Watanabe rabbits) and induced (New Zealand White lipid-fed rabbits) models of arteriosclerosis. The extent and severity of the lesions was significantly reduced in both models by PPS treatment. Finally, we asked whether the proliferative and sclerotic lesion, which is the cause of vascular graft stenosis, might also respond to PPS treatment. To do this we cultured cells from the materials removed from stenotic arteriovenous grafts in hemodialysis patients. We found that PPS inhibits the proliferation and matrix production in a dose-dependent manner.

Differential expression of glomerular extracellular matrix and growth factor mRNA in rapid and slowly progressive glomerulosclerosis: studies in mice transgenic for native or mutated growth hormone

We found that mice transgenic for native bovine growth hormone (bGH) gene had increased body size and rapidly progressive glomerulosclerosis, whereas mice transgenic for a mutated bGH gene (bGH-m11) had near normal body size and slowly progressive glomerulosclerosis. The aim of this study was to determine whether rapidly and slowly progressive glomerulosclerosis had distinct glomerular extracellular matrix (ECM) and growth factor mRNA levels. ECM and growth factors were quantitated by competitive reverse transcriptase-PCR in microdissected glomeruli from bGH, bGH-m11, and nontransgenic littermate control mice. In rapid progressors (bGH mice) at 2 to 3 months, the levels of mRNA-coding for some glomerular ECM and growth factors were increased (alpha 1(IV) collagen, 7.3-fold; laminin B1, 3.9-fold; tenascin, 8-fold; and tumor growth factor (TGF)-beta 1, 3.4-fold). These levels underwent a further 2.3-fold increase at 6 to 9 months. Platelet-derived growth factor (PDGF)-B mRNA was high at 2 to 3 months (7.4-fold) and 6 to 9 months (9.5-fold) and was associated with an increased [3H]-thymidine-labeling index and glomerular cell number. In slow progressors (bGH-m11 mice), the mRNA levels at 2 to 3 months were approximately one half that of rapid progressors (alpha 1(IV) collagen, 3.4-fold; laminin B1 1.9-fold; tenascin, 3-fold; TGF-beta 1, 2.2-fold). PDGF-B levels were normal. At 6 to 9 months, alpha 1(IV) collagen, TGF-beta 1, and PDGF-B mRNA levels doubled, whereas tenascin and laminin B1 levels remained stable. At 12 to 18 months, the alpha 1(IV) collagen, TGF-beta 1, and tenascin levels increased by nearly another 50%. The labeling index and PDGF levels were not increased at any time. The levels of expression of several glomerular ECM mRNA and growth factors of rapid progressors at 2 to 3 months of age was nearly double that of slow progressors, nearly doubling again by 6 to 9 months. In slow progressors, alpha 1(IV) collagen and TGF-beta 1 mRNA levels continued to increase at a slow rate, but tenascin and laminin mRNA levels were only further increased at 12 to 18 months. Thus, the initial levels of these mRNA and their rate of change correlated with the severity of glomerulosclerosis.

Co-expression of bovine growth hormone (GH) and human GH antagonist genes in transgenic mice

Bovine growth hormone (bGH) transgenic (Tg) mice have been shown to possess enhanced growth phenotypes and exhibit severe glomerulosclerosis. One amino acid substitution in GH, i.e. G119R in bGH or G120R in human (h) GH, results in GH antagonists (GHAs). GHA-Tg mice exhibit dwarf phenotypes and normal kidneys. In order to investigate the possibility of GHAs as pharmaceutical agents for the treatment of human diseases with excessive GH levels, we cross bred mice that express bGH with those that express hGHA. Double positive Tg mice were identified that express both genes although at different levels. Kidney histological studies revealed that the double positive Tg mice with high GHA/GH expression ratios possessed normal or near normal kidneys, whereas those with low GHA/GH ratios exhibited glomerulosclerosis similar to GH-Tg mice. Thus, co-expression of GH and GHA genes in vivo results in animal phenotypes and kidney histopathologies which are a reflection of the relative expression levels of each gene.

Mesangial cells from transgenic mice with progressive glomerulosclerosis exhibit stable, phenotypic changes including undetectable MMP-9 and increased type IV collagen

Mice transgenic for bovine growth hormone (bGH) develop progressive mesangial sclerosis resulting in uremia. Mesangial cells from bGH mice were isolated to determine whether the cells maintained a stable phenotypic change in the synthesis and degradation of extracellular matrix, which contribute to the glomerular lesions in vivo. The bGH mesangial cells were 1.2-fold larger than cells from control mice. They had a 1.7-fold increase in doubling time, a 7-fold decrease in labeling index (p < 0.0001), and a 2.4- and 2-fold decrease in c-myc (p < 0.05) and insulin-like growth factor I gene expression, respectively. Collagen synthesis and degradation were studied by PCR, ELISA, and gelatin zymography. bGH mesangial cell alpha 1 collagen IV mRNA levels were increased 2.3-fold (0.47 +/- 0.25 versus 0.20 +/- 0.09 attomoles/500 cells, p < 0.01) whereas secreted collagen IV and collagen IV in the cell lysates were increased 1.4-fold (25.1 +/- 5 versus 17.2 +/- 4 ng/ml/10(5) cells) and 1.8-fold (30.5 +/- 3 versus 16.7 +/- 3 ng/ml/10(5), p < 0.05), respectively. There were no differences in collagen I mRNA levels or in the protein content of either the media or cell lysates. We were not able to detect metalloproteinase 9 (MMP-9) mRNA expression or MMP-9 protein in bGH mesangial cell medium, whereas both mRNA and protein were present in controls. MMP-2 mRNA and enzyme activity in bGH cells were, however, elevated 1.5-fold (p < 0.05) and 2.1-fold (p = 0.05) over controls. Transforming growth factor beta 1 mRNA in bGH cells was 1.6-fold higher than that of controls (p < 0.05). The data suggest that (a) mesangial lesions may result from stable, genetically induced, phenotypic changes in mesangial cells, and (b) alterations of MMP-9 and collagen IV expression by mesangial cells may contribute to an imbalance between extracellular matrix synthesis and degradation and play a critical role in the genesis of glomerulosclerosis.

Inhibition of diabetic nephropathy by a GH antagonist: a molecular analysis

Streptozotocin-treated C57B1/SJL mice developed glomerular hypertrophy and light microscopic lesions mimicking human diabetic glomerulosclerosis. In contrast, there were no glomerular hypertrophy and lesions in diabetic mice transgenic (TG) for a mutated growth hormone (bGH-G119K) that competes with native endogenous GH and results in dwarfism. We examined the molecular events underlying these findings. The non-transgenic (non-TG) diabetic mouse glomeruli had an increase in mRNA coding for alpha 1IV collagen, laminin B1, TGF-beta 1, 72 kDa collagenase, and TIMP-3. In contrast, glomerular type IV collagen and laminin B1 mRNA levels were normal in diabetic TG dwarf mice. However, the 72 kDa gelatinase, TIMP-3, and TGF-beta 1 mRNAs were elevated in the diabetic dwarfs. Type IV collagen and laminin accumulated in the glomeruli of diabetic non-TG, but not of diabetic dwarf mice, by immunofluorescence microscopy, confirming the mRNA data. GH binding protein mRNA levels were comparable in glomeruli from dwarf and non-TG mice, both diabetic and non-diabetic. We did not detect GH receptor mRNA in glomeruli. These data suggest that diabetic glomerulosclerosis is associated with an increase in type IV collagen and laminin synthesis, and that these changes do not occur in mice transgenic for bGH119K, a functional antagonist of GH. The increase of 72 kDa gelatinase, TIMP-3 and TGF-beta 1 mRNAs, independent of GH, suggested that these changes induced by hyperglycemia were not sufficient for the induction of glomerulosclerosis.

TNF-alpha and IL-1 alpha induce mannose receptors and apoptosis in glomerular mesangial but not endothelial cells

The macrophage mannose receptor, a carbohydrate-binding membrane protein, mediates endocytosis and phagocytosis. This study was undertaken to determine whether mannose receptors were expressed in resting glomerular mesangial and endothelial cells and whether their level was affected by cytokines. Neither mannose receptor mRNA nor proteins were found in resting mesangial or endothelial cells. Mannose receptor mRNA was induced in a dose- and time-dependent manner in mesangial cells by interleukin-1 alpha (IL-1 alpha) or tumor necrosis factor-alpha (TNF-alpha) but not by platelet-derived growth factor-B or IL-6. Cell surface receptors were found by fluorescence-activated cell sorter analysis. Binding to stimulated mesangial cells was saturable and inhibited by excess mannose-bovine serum albumin (BSA) but not by galactose-BSA. TNF-alpha and IL-1 alpha also induced apoptosis in mesangial cells. Mannose receptor expression was not restricted to apoptotic stimulated mesangial cells. Neither agonist induced mannose receptor expression or apoptosis in endothelial cells. Because immunoglobulin A, M, and G contain mannose residues, immune aggregates may be removed from the mesangium through cytokine-induced mannose receptors.

Molecular analysis of glomerular diseases in renal biopsies: initial results of a collaborative international study. The International Study Group for Molecular Study of Kidney Biopsies

An accurate assessment of which patient with glomerular disease will progress to end-stage renal failure would be an important addition to establishing prognosis and evaluating therapeutic strategies. We previously found the development of glomerular scarring in animal models was preceded by an increase in glomerular type IV collagen mRNAs and that the level of scarring predicted the rate of progression. The purpose of this study was to determine whether these findings apply to human glomerular diseases using microdissected glomeruli and assessment of mRNA by competitive PCR. After showing that the levels of type IV collagen mRNAs were elevated in sclerotic glomeruli isolated from nephrectomies, we undertook this preliminary cross-sectional study of type IV collagen subchain mRNAs in renal biopsies in two of the leading causes of glomerulosclerosis, diabetic nephropathy, and membranous glomerulopathy. We found that glomerular type IV collagen mRNA levels were altered in disease-specific ways. The relative levels of the individual alpha-chains of type IV collagen depended on the anatomic site of the glomerular lesions. The alpha 2 type IV/alpha 3 type IV collagen mRNA ratio was high in diabetes mellitus, but not in membranous glomerulopathy. These data, coupled with those obtained from experimental animals, suggest that a dysregulation of basement collagen synthesis underlies progressive glomerular scarring. If these conclusions are verified in prospective studies it will be feasible to assess the risk of developing progressive glomerulosclerosis in the individual patient and to quantitatively assess therapeutic responses in a timely manner.

Dissociation of glomerular hypertrophy, cell proliferation, and glomerulosclerosis in mouse strains heterozygous for a mutation (Os) which induces a 50% reduction in nephron number

We reported that the Os mutation in ROP mice induced a 50% reduction in nephron number, glomerular hypertrophy, and severe glomerulosclerosis. We examined two mouse strains with the Os mutation, ROP Os/+ and C57 Os/+ mice, to determine whether the genetic background influenced the development of glomerulosclerosis. Nephron number was decreased by 50% in both ROP Os/+ and C57 Os/+ mice, and a glomerular volume and labeling index were two- to threefold increased in both. Whereas glomerulosclerosis was severe in ROP Os/+ mice, it was absent or minimal in C57 Os/+ mice. ROP Os/+ glomeruli had two- to threefold more type IV collagen, laminin, and tenascin than C57 Os/+ by immunofluorescence microscopy. Glomerular alpha 1IV collagen and tenascin mRNA levels were increased (2.8- and 1.7-fold) in ROP Os/+ and in C57 Os/+ (1.7- and 1.4-fold) mice. Both ROP Os/+ and C57 Os/+ mice had a slight increase (1.5- and 1.7-fold) in 72-kD collagenase mRNA levels. Whereas laminin B1 mRNA levels were twofold higher in ROP +/+ than in C57 +/+ mice, there was no further change in the presence of the Os mutation. Thus, the response to the Os mutation depended on the mouse strain, since severe glomerulosclerosis occurred only in ROP Os/+ mice, even though cell proliferation and glomerular hypertrophy also were present in C57 Os/+ mice.

Localization of glutamic acid decarboxylase in the kidneys of nonobese diabetic mice

Antibodies to glutamic acid decarboxylase (GAD), a pancreatic islet beta-cell antigen, are present in > 80% of newly diagnosed insulin-dependent diabetes mellitus (IDDM), and are found in nonobese diabetic (NOD) mice, a murine model of spontaneous IDDM. To determine whether GAD is a target antigen in the kidney damage of NOD mice, we studied GAD mRNAs (GAD65 and GAD67) by RT-PCR in mesangial cells, isolated glomeruli, and kidney cortex and medulla in NOD and SJL/C57BL mice. GAD mRNAs were detected in the cortex of both diabetic and nondiabetic NOD and SJL/C57BL mice and GAD antigen was present in proximal and distal tubules by immunofluorescence microscopy. Neither GAD antigen nor mRNA were present in mesangial cells or glomeruli of diabetic or nondiabetic mice. Thus, the expression of GAD in renal tubules raises the possibility that GAD antigens may play a role in diabetic tubulointerstitial disease, whereas the absence of these antigens in glomeruli suggests that GAD-triggered autoimmunity is not directly involved in the glomerular lesions.

Diabetic nephropathy: molecular analysis of extracellular matrix and clinical studies update

BACKGROUND

Progressive glomerulosclerosis associated with decreasing kidney function, resulting in end-stage renal failure, is the major finding in diabetic nephropathy. There are multiple components of the extracellular matrix, and neither the exact composition nor the factors responsible for its increase in diabetic nephropathy is known.

METHODS

We examined matrix synthesis and degradation at the level of gene expression and ECM composition, in the glomeruli of diabetic mice transgenic for a mutated bGH and their littermate controls, and in renal biopsies of patients with diabetic nephropathy.

RESULTS

We found that streptozotocin-treated C57BL/SJL mice developed histological lesions closely resembling human diabetic glomerulosclerosis, whereas there were no glomerular lesions in diabetic mice transgenic for a growth hormone analogue which competes with native GH and results in dwarfism. We found that diabetic glomerulosclerosis in mice was associated with an increase in type IV collagen and laminin synthesis, and that these changes are selectively inhibited in dwarf mice transgenic for the mutant GH analogue. Preliminary examination of glomeruli isolated from renal biopsies revealed a homogeneous elevation in the alpha 2/alpha 3IV ratio among diabetics.

CONCLUSIONS

These data suggested that diabetic nephropathy is characterized by modifications in ECM gene regulation in both mouse models and in diabetics, and that GH may promote the susceptibility to this complication. Finally, the data from the Diabetes Control and Complications Trial is updated, emphasizing the importance of close glucose control in the amelioration of an elevated albumin excretion rate as a continuous function of the level of control.

Administration of AGEs in vivo induces extracellular matrix gene expression

The role that advanced glycosylation end-products (AGEs) may play in the development of diabetic nephropathy is still not completely understood. In order to elucidate the nature of their effect, the consequences of exogenously administered AGEs on extracellular matrix gene expression were examined in mice by competitive PCR. Normal adult mice receiving repeated injections of AGEs had an increase in the expression of genes coding for type IV collagen and laminin in the glomeruli. The increase was accompanied by up-regulation of TGF-beta 1 but not PDGF-B expression. The expression of smooth muscle and beta-actin did not change, showing that the increase in gene expression was specific for genes implicated in the early stages of diabetic nephropathy. The co-administration of aminoguanidine, a drug that inhibits AGEs cross-links, prevented the up-regulation of gene expression in AGEs-injected mice. Thus, AGEs can induce extracellular matrix genes in the absence of hyperglycaemia.

Relationships between mesangial cell proliferation and types I and IV collagen mRNA levels in vitro

Changes in the composition of the mesangial extracellular matrix (ECM) and cell turnover are present in glomerular disease. To determine if ECM changes play a role in perpetuating mesangial cell dysfunction, we examined a line of mouse mesangial cells cultured on films or gels of several ECM components and also on methyl cellulose, an inert substrate that prevents attachment. Cells on films of fibronectin or type IV or I collagen had persistently high growth rates and high levels of alpha 1-I and alpha 1-IV collagen mRNAs. In contrast, on gels of type IV or I collagen or matrigel, the growth rate was low. The alpha 1-IV collagen mRNA levels were low on type IV collagen gel or matrigel, whereas the alpha 1-I collagen mRNA levels remained high. In contrast, the alpha 1-I collagen mRNA levels were low on type I collagen gel, and the alpha 1-IV collagen mRNA levels were high. Cells on methyl cellulose formed floating aggregates, did not proliferate, and had a 5- to 10-fold decrease in both alpha 1-I and alpha 1-IV collagen mRNA levels. These phenotypic changes were largely reversible. Finally, when matrigel was layered over cells on fibronectin films, alpha 1-IV collagen mRNA levels decreased, but alpha 1-I collagen mRNA levels and proliferation remained high. Thus proliferation and alpha 1-I and alpha 1-IV collagen mRNA levels in mesangial cells were independently regulated and depended on attachment and the nature of the adjacent matrix.

Molecular analysis of spontaneous glomerulosclerosis in Os/+ mice, a model with reduced nephron mass

Oligosyndactyly mice (ROP Os/+) are a radiation-induced mutant strain with reduced glomerular number and increased glomerular size. We found that they develop glomerulosclerosis. At 3 mo, ROP Os/+ mice had diffuse mesangial expansion by light microscopy, whereas their +/+ littermates did not. Electron microscopic morphometry revealed a twofold increase in mesangial areas but no changes in the thickness of glomerular basal laminae. Mean glomerular volume was increased 1.8-fold. Cell number and thymidine labeling index were increased 1.3- and 2.4-fold, respectively. The amount of glomerular type IV collagen and tenascin but not laminin was increased by immunofluorescence microscopy. mRNA levels in microdissected glomeruli were measured by competetive reverse transcription-polymerase chain reaction and corrected for cell number. alpha 1-Chain type IV collagen and tenascin mRNAs were increased 3.2-fold and 1.8-fold, whereas laminin B1 mRNA levels were not. The levels of 72-kDa collagenase mRNA were increased 1.6-fold. Transforming growth factor-beta 1 mRNA levels were elevated 1.8-fold, but platelet-derived growth factor-B mRNA levels remained normal. This is the first analysis of glomerular molecular and cellular changes in a model of congenital nephron reduction.

Collagen and collagenase mRNAs in normal and sclerotic glomeruli: predictors of progression and response to therapy

Progressive glomerulosclerosis is associated with decreasing kidney function, eventuating in end-stage renal failure. There are multiple components of the extracellular matrix, and the exact composition in various renal diseases is not known. Thus, we examined some of the major components of the extracellular matrix (ECM) in murine and human glomerular diseases. We studied matrix synthesis and degradation at the level of gene expression and ECM composition in the intact glomerulus. To determine whether the composition of sclerosis was similar among diseases, we examined a normal mouse strain and compared it with strains which spontaneously developed glomerulosclerosis. The baseline levels of matrix components varied between different mouse strains, and this level correlated with their propensity to develop glomerulosclerosis. In addition, when glomerulosclerosis was induced, the baseline ECM mRNA level predicted the subsequent outcome. We studied mice transgenic for bovine growth hormone, since they develop progressive glomerulosclerosis. Treatment with heparin substantially decreased the lesions without changes in type IV collagen mRNAs. However, there was an up-regulation of both the mRNA and enzyme activity for the 92 kD matrix metalloproteinase. In contrast, when these mice were treated with either angiotensin converting enzyme inhibitors or angiotensin II (Ang II) receptor antagonists, the glomerulosclerosis was accentuated histologically and the ECM synthetic and degradative mRNAs were elevated. These data suggest that the mRNA levels reflect response to therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration of AGEs in vivo induces genes implicated in diabetic glomerulosclerosis

Administration of advanced glycosylation end products (AGEs), prepared on mouse albumin, to normal young adult mice, resulted in an increase in mean glomerular volume and up-regulation of laminin B1 and alpha 1 type IV collagen mRNAs measured by competitive PCR in single microdissected glomeruli. Both glomerular hypertrophy and overexpression of genes coding for extracellular matrix were abrogated when aminoguanidine, an inhibitor of AGE cross-linking, was added to the AGEs injections, suggesting that the glomerular response to AGEs was specific. The effects of AGEs administration in vivo are comparable to those occurring in the early stage of diabetic nephropathy, suggesting a participation of AGEs in these events.

Effects of streptozotocin treatment in growth hormone (GH) and GH antagonist transgenic mice

To investigate GH's role in diabetic end organ damage, experimental diabetes was induced with streptozotocin (STZ) in bovine GH (bGH) or bGH antagonist transgenic mice and in their nontransgenic (NTG) litter mates. Body growth, blood glucose, serum insulin-like growth factor-I levels, liver GH receptor (GHR) binding, and kidney histology of these animals were evaluated. After administration of multiple low doses of STZ, 90% of the mice developed hyperglycemia. The diabetic animals, especially those expressing GH and GH antagonist transgenes, demonstrated retarded body growth and reduced insulin-like growth factor-I levels when compared with their nondiabetic litter mates. Kidney histology revealed severe glomerulosclerosis in diabetic and nondiabetic bGH transgenic mice. Diabetic NTG mice exhibited moderate kidney lesions. Diabetic bGH antagonist transgenic mice possessed normal glomeruli indistinguishable from those seen in nondiabetic NTG mice. GHR-binding assays revealed that liver GHR-binding sites were significantly reduced in diabetic NTG mice and transgenic dwarf mice when compared with their nondiabetic controls. Conversely, liver GHR-binding ability was significantly increased in bGH transgenic mice as compared with their NTG littermates and remained high during diabetes. It is concluded that transgenic mice that express a GH antagonist are protected from diabetes and or GH-induced nephropathy.

Overexpression of transforming growth factor-beta 1 mRNA is associated with up-regulation of glomerular tenascin and laminin gene expression in nonobese diabetic mice

Nonobese diabetic (NOD) mice spontaneously develop immune-mediated insulin-dependent diabetes mellitus and nephropathy, providing an opportunity to study the early molecular events in a model of diabetic glomerulosclerosis. The expression of several genes coding for growth factors and extracellular matrix was examined in microdissected glomeruli, by the use of reverse transcription-competitive polymerase chain reaction, in diabetic NOD mice (mean duration of diabetes, 28.5 +/- 7 days) and age-matched nondiabetic NOD mice with normal glucose tolerance. The levels of mRNA coding for transforming growth factor-beta 1, tenascin, and laminin B1 increased 1.9-, 2.0-, and 1.7-fold, respectively, whereas platelet-derived growth factor (PDGF)-B, alpha 1(IV) collagen, 72-kd collagenase, alpha-smooth muscle actin, and beta-actin mRNA remained stable in the diabetic mice. The kidney advanced glycosylation end-products levels increased 2.1-fold in the diabetic mice, and the diabetic glomeruli showed an accumulation of tenascin and laminin but not of type IV collagen by immunofluorescence microscopy. There was no increase in cell number per glomerulus after the onset of diabetes, a finding consistent with stable PDGF-B and alpha-smooth muscle actin mRNA levels. These findings provide evidence that increased glomerular transforming growth factor-beta 1, but not PDGF-B, mRNA is associated with the up-regulation of tenascin and laminin expression after advanced glycosylation endproduct accumulation, early after the onset of diabetes.