Cyclosporine-associated thrombotic microangiopathy/hemolytic uremic syndrome following kidney and kidney-pancreas transplantation

Cyclosporine-associated thrombotic microangiopathy (CsA-TMA) is characterized by anemia, acute renal failure, and renal TMA. We report a case-control study of 13 patients (seven kidney-alone transplant recipients and six kidney-pancreas transplant recipients) who developed TMA (12 CsA, 1 FK506). Once CsA-TMA was identified, CsA or FK506 was discontinued and isradipine, aspirin, and pentoxifylline were started. Cyclosporine was reinstituted in all patients once serum creatinine reached the previous baseline value. Patients developing further decreases in renal function on rechallenge with CsA were converted to FK506 (n = 3). Rechallenge with CsA was successful in nine of the 13 patients (69%), with three (23%) converted to FK506 for a total salvage rate of 92%. The creatinine clearance at 6 months, 1 year, and 2 years following transplantation was 73.2 +/- 25.7 mL/min, 54.7 +/- 18.8 mL/min, and 57.0 +/- 32.0 mL/min, respectively, for patients successfully rechallenged with CsA compared with 67 +/- 17 mg/min, 71.8 +/- 21.2 mL/min, and 69 +/- 19 mg/min, respectively, for controls (P = NS). The average creatine clearance for patients converted to FK506 was 44.7 +/- 31.2 mL/min at 6 months following transplantation (n = 3) and 27.0 +/- 11.3 mL/min at 1 year. In this case-controlled retrospective series of renal transplant patients with documented CsA-TMA, the triple-drug combination of isradipine, aspirin, and pentoxifylline allowed for the successful reinstitution of CsA or conversion to FK506 in the setting of TMA, and resulted in increased transplant survival compared with previous reports.

Oxidation-specific epitopes in human coronary atherosclerosis are not limited to oxidized low-density lipoprotein

BACKGROUND

Previous small studies have demonstrated positive immunohistochemical staining in rabbit and human atherosclerotic plaques by antibodies that recognize oxidized low-density lipoprotein (OxLDL), but none have examined a large number of human coronary arteries or evaluated whether epitopes recognized by these antibodies might be present on plaque proteins other than OxLDL.

METHODS AND RESULTS

Immunohistochemistry was performed on atherosclerotic (n = 87) and nonatherosclerotic (n = 51) coronary arterial segments from 20 patients by use of monoclonal antibodies that recognize epitopes on macrophages, smooth muscle cells, apolipoprotein (apo) B, and OxLDL. Staining with the OxLDL antibody (Ox5) was much more prevalent in atherosclerotic than in control segments. Extracellular Ox5 staining colocalized with apo B, but cell-associated Ox5 staining occurred in the absence of cell-associated apo B staining, which suggests that cell-associated epitopes for Ox5 were on proteins other than LDL. Epitopes for Ox5 formed in vitro on two readily available non-apo B proteins, human serum albumin and apo A-I, when these proteins were incubated under conditions of oxidant stress with polyunsaturated but not monounsaturated fatty acids; furthermore, an antioxidant inhibited Ox5 epitope formation. Thus, epitopes for Ox5 can form on proteins other than apo B. Also, phorbol ester-treated macrophages cultured in apo B-free medium developed epitopes for Ox5.

CONCLUSIONS

These findings are consistent with the hypothesis that atherosclerosis is associated with oxidative modification of proteins in addition to LDL, particularly cell-associated proteins, and that the antiatherosclerotic effects of antioxidants seen in some studies may not be solely due to prevention of LDL oxidation.

SPARC is expressed by mesangial cells in experimental mesangial proliferative nephritis and inhibits platelet-derived-growth-factor-medicated mesangial cell proliferation in vitro

Mesangial cell proliferation is a characteristic feature of many glomerular diseases and often precedes extracellular matrix expansion and glomerulosclerosis. This study provides the first evidence that SPARC (secreted protein acidic and rich in cysteine) could be an endogenous factor mediating resolution of experimental mesangial proliferative nephritis in the rat. SPARC is a platelet-derived-growth-factor-binding glycoprotein that inhibits proliferation of endothelial cells and fibroblasts. We now show that SPARC is synthesized by mesangial cells in culture and that SPARC mRNA levels are increased by platelet-derived growth factor and basic fibroblast growth factor. Recombinant SPARC or the synthetic SPARC peptide 2.1 inhibited platelet-derived-growth-factor-induced mesangial cell DNA synthesis in vitro. In a model of experimental mesangioproliferative glomerulonephritis, SPARC mRNA was increased 5-fold by day 7 and was identified in the mesangium by in situ hybridization. Similarly, SPARC was increased in glomerular mesangial cells and visceral epithelial cells by day 5 and reached maximal expression levels by day 7. Mesangial cell proliferation increased by 36-fold on day 5 and decreased abruptly on day 7. Maximal expression of SPARC was correlated with the resolution of mesangial cell proliferation. We propose that SPARC functions in part as an endogenous inhibitor of platelet-derived-growth-factor-mediated mesangial cell proliferation in glomerulonephritis and that it could account for the resolution of cellular proliferation in this disease.

Apolipoproteins B, (a), and E accumulate in the morphologically early lesion of 'degenerative' valvular aortic stenosis

Nonrheumatic aortic stenosis of trileaflet aortic valves has been considered to be a "degenerative" process, but the early lesion of aortic stenosis contains the chronic inflammatory cells, macrophages and T lymphocytes. Because lipoprotein deposition is prominent in atherosclerosis, another chronic inflammatory process, this study examined whether lipoproteins accumulate in aortic valve lesions. Immunohistochemical studies were performed to detect apolipoprotein (apo) B, apo(a), apoE, macrophages, and alpha-actin-expressing cells on 18 trileaflet aortic valves that ranged from normal to stenotic. All three apolipoproteins were detected in early through end-stage lesions of aortic stenosis but not in histologically normal regions. Comparison with oil red O staining suggested that most of the extracellular neutral lipid in these valves was associated with either plasma-derived or locally produced apolipoproteins. Thus, in early through end-stage aortic valve lesions, apolipoproteins accumulate and are associated with the majority of extracellular valve lipid. These results are consistent with the hypothesis that lipoprotein accumulation in the aortic valve contributes to pathogenesis of aortic stenosis.

Platelet-derived growth factor-A mRNA expression in fetal, normal adult, and atherosclerotic human aortas. Analysis by competitive polymerase chain reaction

BACKGROUND

To understand which growth factors are important for growth of atherosclerotic plaques, it is necessary to know the factor's relative abundance and how its gene is regulated in relation to cell proliferation. We tested whether platelet-derived growth factor-A (PDGF-A) mRNA levels correlated with cell proliferation in developing aorta, normal adult aorta, and atherosclerotic plaques.

METHODS AND RESULTS

We developed a competitive reverse transcription-polymerase chain reaction (RT-PCR) assay to measure human PDGF-A mRNA levels in small tissue samples. A mutated PDGF-A synthetic RNA was used as an internal standard to compete with endogenous PDGF-A mRNA for amplification. The assay is highly sensitive and much more precise than routine RT-PCR. Correction for heteroduplex pairing between the endogenous and mutant PCR products correlates precisely with synthetic RNA standards and quantitative Northern blotting. Immunostaining with the proliferation marker (proliferating cell nuclear antigen) showed the following rank order of proliferation: fetal aorta >> atherosclerotic plaque > normal aortic media. PDGF-A mRNA levels, however, did not correlate with proliferation. Normal adult aorta contained the most PDGF-A mRNa (34.0+/-7.6 amol/microgram total RNA). Fetal aortas were intermediate (10.2+/-1.6 amol/microgram total RNA); advanced atherosclerotic plaques contained the least PDGF-A mRNA (0.3+/-0.1 amol/microgram total RNA). PDGF-A protein was readily detectable in normal media by immunostaining. Advanced plaques generally had less cell-associated PDGF-A protein, although A-chain was also detected in plaque matrix.

CONCLUSIONS

PDGF-A mRNA and protein do not correlate with proliferation among these three groups. The significance of high levels of PDGF-A mRNA in the "quiescent" aortic media is unknown but it clearly does not promote cell replication.

Expression of collagen, interstitial collagenase, and tissue inhibitor of metalloproteinases-1 in restenosis after carotid endarterectomy

Extracellular matrix is the principal component of the fibrous caps of atherosclerotic plaques and intimal hyperplastic lesions of reconstructed arteries. Interstitial collagen form an important part of the matrix, and the balance between collagen synthesis and degradation by interstitial collagenase (matrix metalloproteinase-1, MMP-1) may determine whether plaques rupture or vessels develop stenosis. We examined type I procollagen gene expression in human atherosclerotic and restenotic carotid arteries using in situ messenger RNA (mRNA) hybridization and the expression of MMP-1 and its endogenous inhibitor (tissue inhibitor of metalloproteinases-1, TIMP-1) by immunohistochemistry. Compared with normal arteries, atherosclerotic plaques bed increased expression of immunoreactive MMP-1 and TIMP-1 with modest increase of type 1 procollagen mRNA. Early restenotic lesions (< 1.5 years) contained abundant type I procollagen mRNA but little immunoreactive MMP-1 and TIMP-1. Late restenotic lesions (> 4 years) resembled atheroma and exhibited increased immunoreactive MMP-1 and TIMP-1 as well as abundant type I procollagen mRNA. Compared with atherosclerotic plaques, type I procollagen is increased and MMP-1 is decreased in early restenotic lesions. MMP-1 and TIMP-1 expressions are upregulated in lesions with a clear atheroma. These findings suggest that the balance between proteolysis and matrix synthesis may influence both the stability of atheromatous plaques and the development of restenotic lesions.

Mechanisms involved in the pathogenesis of tubulointerstitial fibrosis in 5/6-nephrectomized rats

The 5/6 nephrectomy model is used to study pathogenetic mechanisms underlying chronic renal failure. We previously demonstrated that increased mesangial cell proliferation and glomerular PDGF B-chain expression precede glomerulosclerosis in this model. In the present study we have assessed the concomitant changes in the cortical tubulointerstitium. A wave of tubular and interstitial cell proliferation (as determined by immunostaining for PCNA) occurred at week 1 after 5/6 nephrectomy. This wave preceded the peak glomerular cell proliferation by one week. Tubulointerstitial cell proliferation decreased thereafter and reached control values by week 10. In situ hybridization and immunostaining for PDGF B-chain and beta-receptor in sham-operated controls showed labeling of distal tubules and collecting ducts, while no signal was present in the interstitium. PDGF B-chain mRNA and protein expression was markedly increased in tubules at weeks 2 and 4 after 5/6 nephrectomy and in the interstitium (particularly in areas of inflammatory infiltrates) at weeks 2 to 10. Similar changes occurred with PDGF receptor beta-subunit immunostaining. Interstitial expression of desmin and alpha-smooth muscle actin (markers of myofibroblasts) progressively increased after week 1. Interstitial influx of monocytes/macrophages with focal accentuation started at week 2. Counts of lymphocytes, neutrophils and platelets showed only minor changes. In parallel to the monocyte/macrophage influx, progressive interstitial accumulation of collagens I and IV, laminin, and fibronectin occurred. All of these changes were correlated with the increase in serum creatinine, proteinuria and an index of tubulointerstitial damage. We conclude that tubulointerstitial changes after 5/6 nephrectomy show similarities with those observed in the glomeruli. Tubular and interstitial overexpression of PDGF B-chain and its receptor may play a role in mediating fibroblast migration and/or proliferation in areas of tubulointerstitial injury.

Neovascular expression of E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in human atherosclerosis and their relation to intimal leukocyte content

BACKGROUND

Leukocyte recruitment is an early event in atherogenesis, and the leukocyte adhesion molecules E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) recently have been detected in human atherosclerosis. However, no previous study has evaluated either the distribution of these three molecules at different sites within the arterial intima or their relation to plaque leukocyte content.

METHODS AND RESULTS

Immunohistochemistry was performed on 99 coronary artery segments (34 controls and 65 with atherosclerotic plaque) to identify E-selectin, ICAM-1, VCAM-1, macrophages, smooth muscle cells, and T lymphocytes. For each segment, the presence or absence of adhesion molecule was determined at the arterial lumen, on intimal neovasculature, and on intimal nonendothelial cells. Each segment was scored for intimal macrophage and T-lymphocyte densities on a semiquantitative scale of 0 to 3. In atherosclerotic plaques, the prevalences of E-selectin, ICAM-1, and VCAM-1 on plaque neovasculature were twofold higher than their prevalences on arterial luminal endothelium. E-selectin was the only adhesion molecule for which expression on arterial luminal endothelial cells was more prevalent in plaques than in control segments. Increased plaque intimal macrophage density was associated with expression of VCAM-1 on neovasculature (P < .01) and on nonendothelial cells (P < .01). Increased plaque intimal T-lymphocyte density was associated with the presence of both ICAM-1 and VCAM-1 on neovasculature (both P < .01) and on nonendothelial cells (both P < .01).

CONCLUSIONS

In atherosclerotic plaques, the expression of all three leukocyte adhesion molecules was more prevalent on intimal neovasculature than on arterial luminal endothelium. Further, the presence on neovasculature and nonendothelial cells of VCAM-1 and ICAM-1 was strongly associated with increased intimal leukocyte accumulation. These findings suggest that leukocyte recruitment through and/or activation of intimal neovasculature may play important roles in the pathogenesis of human atherosclerosis.

Monocyte chemoattractant protein-1 mRNA expression in hemangiomas and vascular malformations

Hemangiomas are vascular tumors that appear at or shortly after birth and undergo a rapid growth before involuting. During the proliferative phase, hemangiomas are infiltrated by macrophages, cells that are capable of initiating angiogenesis. Vascular malformations grow slowly, commensurate with the child, and do not regress or become infiltrated by macrophages. We demonstrate by in situ hybridization increased monocyte chemoattractant protein-1 (MCP-1) mRNA expression during hemangioma and vascular malformation growth. We found markedly upregulated expression of MCP-1 mRNA in all proliferative hemangioma specimens, expressed by alpha-actin perivascular smooth muscle cells and interstitial HAM 56+ macrophages. In contrast, 9 of 10 clinically involuting hemangiomas displayed no expression of MCP-1 mRNA. We found no expression of MCP-1 mRNA in vascular malformations, which correlates with the minimal monocytic infiltration of these lesions. We also showed that dexamethasone and interferon-alpha downregulate MCP-1 mRNA in cultured human vascular smooth muscle cells. Glucocorticoids can be efficacious in 30-50% of cases when given in the proliferative phase of hemangioma growth, but have no beneficial effect on vascular malformations. Interferon-alpha has been used to dramatically induce regression of steroid-refractory hemangiomas. Both of these agents' beneficial action on proliferative hemangiomas may, in part, result from reduced MCP-1 production and reduced influx of angiogenic macrophages.

Role of the complement membrane attack complex (C5b-9) in mediating experimental mesangioproliferative glomerulonephritis

Previous studies have demonstrated that most pathologic changes in the antithymocyte serum (ATS) model of mesangioproliferative glomerulonephritis are complement-dependent. These include mesangiolysis, glomerular platelet infiltration, mesangial cell proliferation, mesangial cell production of growth factors and phenotypic change to express alpha-actin, glomerular macrophage infiltrate, mesangial matrix expansion, and proteinuria. The mechanism by which complement mediates these effects has not been defined. Because neutrophils do not participate in the ATS model, we hypothesized that the complement effects observed are consequent to glomerular cell insertion of the C5b-9 membrane attack complex of complement. This hypothesis was tested utilizing PVG rats which exhibit an absence of C6 inherited in an autosomal recessive pattern. C6 deficient (C-) PVG rat serum activated by zymosan produced normal amounts of C5a compared to normocomplementemic (C+) PVG rat controls but no C5b-9. When ATS was induced, C- PVG rats had a significant and marked reduction in mesangiolysis, platelet infiltration, mesangial cell proliferation, alpha-actin expression, macrophage infiltration, collagen IV deposition, and proteinuria compared to C+ controls. The reduction in each of these parameters was comparable to that achieved by systemic complement depletion of C+ PVG rats with cobra venom factor. These findings establish the role of C5b-9 in mediating each of the complement-dependent features of the ATS model and indicate that C5b-9 accounts for all of the complement-mediated effects observed. This study provides the first documentation of a functional role for C5b-9 in mediating a non-membranous inflammatory type of glomerular injury in vivo.

Identification of platelet-derived growth factor A and B chains in human renal vascular rejection

Platelet-derived growth factor (PDGF) exists as a dimer composed of two homologous but distinct peptides termed PDGF-A and -B chains, and may exist as AA, AB, and BB isoforms. The PDGF-B chain has been implicated as a mediator of renal vascular rejection by virtue of up-regulated expression of its receptor, PDGF beta-receptor, in affected arteries. A role for PDGF-A chain in mediating intimal proliferation has been suggested in human atherosclerosis (Rekhter MD, Gordon D: Does platelet-derived growth factor-A chain stimulate proliferation of arterial mesenchymal cells in human atherosclerotic plaques? Circ Res 1994, 75:410), but no studies of this molecule in human renal allograft injury have been reported to date. We used two polyclonal antisera to detect expression of PDGF-A chain and one monoclonal antibody to detect PDGF-B chain by immunohistochemistry in fixed, paraffin-embedded tissue from 1) normal adult kidneys, 2) a series of renal transplant biopsies chosen to emphasize features of vascular rejection, and 3) allograft nephrectomies. Immunohistochemistry was correlated with in situ hybridization on adjacent, formalin fixed tissue sections from nephrectomies utilizing riboprobes made from PDGF-A and -B chain cDNA. PDGF-A chain is widely expressed by medial smooth muscle cells of normal and rejecting renal arterial vessels of all sizes by immunohistochemistry and in situ hybridization. PDGF-A chain is also expressed by a population of smooth muscle cells (shown by double immunolabeling with an antibody to alpha-smooth muscle actin) comprising the intima in chronic vascular rejection. In arteries demonstrating acute rejection, up-regulated expression of PDGF-A chain by endothelial cells was detected by both immunohistochemistry and in situ hybridization. In contrast, PDGF-B chain was identified principally in infiltrating monocytes within the rejecting arteries, similar to its localization in infiltrating monocytes in human atherosclerosis. Although less prominent than the case for PDGF-A chain, PDGF-B chain also was present in medial and intimal smooth muscle cells in both rejecting and nonrejecting renal arteries. PDGF-A and -B chains have now been localized at both the mRNA and protein levels to the intimal proliferative lesions of vascular rejection. These peptides, which are known stimuli for smooth muscle cell migration and proliferation in experimental vascular injury, may have similar stimulatory effects on smooth muscle cells in an autocrine and/or paracrine manner to promote further intimal expansion and lesion progression in this form of human vasculopathy.

Alpha-v beta-3 integrin expression in normal and atherosclerotic artery

Recent evidence suggests that alpha v beta 3 integrin is a critical molecule in several processes involved in atherosclerosis progression and in restenosis, eg, smooth muscle cell (SMC) migration and angiogenesis. While several ligands for this integrin are known to be present in atherosclerotic plaque, little is known about the presence of alpha v beta 3 integrin at this site. In the present study, we have examined alpha v beta 3 expression in normal and atherosclerotic arteries. Thirty-six coronary artery segments from the recipient hearts of 24 patients undergoing heart transplantation were classified into two groups: nonatherosclerotic diffuse intimal thickening (DIT) and atherosclerotic plaques. Serial frozen sections were examined immunohistochemically with four different monoclonal antibodies directed against human alpha v beta 3 complex or the beta 3 subunit and with cell markers for SMCs, macrophages, and endothelial cells. The endothelium along the lumen of both DIT and plaque arteries showed high expression of alpha v beta 3. The media of both DIT and plaque arteries showed less intense but extensive expression of alpha v beta 3. Immunoprecipitation and reverse-transcribed polymerase chain reaction (RT-PCR) analyses performed on extracts from the aortic media confirmed the presence of alpha v beta 3 in the media. In the intima of both DIT and plaque arteries, alpha v beta 3 expression generally colocalized with SMCs but rarely with macrophages. The microvessels in the adventitia as well as in the plaque showed prominent expression of alpha v beta 3, in contrast to low expression in similar-sized microvessels of the skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Participation of glomerular endothelial cells in the capillary repair of glomerulonephritis

In many glomerular diseases severe injury to the mesangium may occur, leading to matrix dissolution and damage to the glomerular capillaries. Although the destruction of glomerular architecture may lead to permanent injury, in some cases spontaneous recovery occurs. The mechanisms that mediate this recovery are unknown. In this study we provide evidence for glomerular capillary repair (angiogenesis) in the adult injured glomerulus. Injection of anti-Thy 1 antibody into rats results in severe mesangiolysis with capillary ballooning, microaneurysm formation, and loss of endothelial cells in addition to mesangial cells. Although mesangial proliferation is a major response to injury, proliferation of endothelial cells also can be documented from days 2 to 14 in association with repair of the capillaries. The endothelial cell proliferation peaks on days 2 and 7, when it is seven- to ninefold greater than normal. Many of the endothelial cells display morphological features of angiogenesis. The initial wave of endothelial cell proliferation can be reduced by 40% with neutralizing anti-basic fibroblast growth factor antibodies (P < 0.001). The later glomerular endothelial cell proliferation is associated with upregulated expression of vascular permeability factor/endothelial cell growth factor (VPF/VEGF) and an increase of flk, a VPF/VEGF receptor. Although PDGF is expressed in this model, anti-PDGF antibody treatment did not affect the endothelial cell proliferative response. In summary, glomerular endothelial cells have an active role in the glomerular response to injury. Glomeruli are capable of healing microaneurysms, and the mechanism involves basic fibroblast growth factor- and VPF/VEGF-mediated endothelial proliferative responses.

Osteopontin is expressed in human aortic valvular lesions

BACKGROUND

Nonrheumatic stenosis of trileaflet aortic valves, in which calcification is a prominent feature, has been termed a "degenerative" condition, but it has been demonstrated recently that chronic inflammation is a characteristic feature of the developing lesion of aortic stenosis. This observation raised the possibility that calcification in the aortic valve might be actively regulated. Thus, the present study investigated whether osteopontin, a protein implicated in the regulation of both normal and dystrophic calcification, could be detected in lesions of valvular aortic stenosis.

METHODS AND RESULTS

Morphological and immunohistochemical studies were performed on 14 human aortic valves, representing a range of pathology from normal to clinically stenotic. The extent of calcification and macrophage accumulation and their relation to the presence of osteopontin protein were characterized. Highly statistically significant associations were found between the degree of osteopontin expression and the degrees of both calcification and macrophage accumulation in early through late lesions of aortic stenosis. Further, in situ hybridization localized osteopontin mRNA to a subset of lesion macrophages.

CONCLUSIONS

These results suggest that, rather than representing a degenerative and unmodifiable process, calcification in aortic stenosis may be, in part, an actively regulated process with the potential for control either through modification of inflammation or synthesis of proteins such as osteopontin, which may modulate calcification in this tissue.

Glomerulonephritis in renal allografts associated with hepatitis C infection: a possible relationship with transplant glomerulopathy in two cases

Chronic infection with hepatitis C virus (HCV) has been identified as a cause of type I membranoproliferative glomerulonephritis (MPGN). HCV infection is common in patients with end-stage renal disease and may persist in renal allograft recipients. MPGN in the allograft may therefore be a manifestation of persistent HCV infection. We report two cases of glomerulopathy with features of both MPGN and transplant glomerulopathy in renal transplant patients chronically infected with HCV. We discuss the course of interferon alfa therapy in both patients as well as a possible relationship of HCV infection with transplant glomerulopathy.

Pathogenesis of cyclosporine nephropathy: roles of angiotensin II and osteopontin

Low-salt-diet, cyclosporine (CsA; 15 mg/kg per day)-treated rats develop striped interstitial fibrosis, arteriolar hyalinosis, and azotemia similar to the chronic nephropathy observed in humans. To examine the role of angiotensin II in this model, rats on a low-salt diet were given CsA, CsA and the angiotensin II receptor Type I antagonist Losartan (10 mg/kg per day), CsA and hydralazine/furosemide, or vehicle. At Day 35, CsA-treated rats had tubular injury, arteriolopathy of the afferent arteriole, increased expression of the monocyte-macrophage adhesive protein osteopontin, interstitial macrophage infiltration, increased interstitial transforming growth factor-beta expression, and interstitial fibrosis. This study provides new insight in both pathogenic and therapeutic aspects of CsA nephropathy. The pathogenesis of CsA nephropathy involves the expression of osteopontin by tubular epithelial cells, the level of which closely correlates with the degree of macrophage infiltration and interstitial fibrosis in all groups (r = 0.79 and 0.74, respectively; P < 0.001). Therapeutic conclusions can be drawn from the observation that both losartan and hydralazine/furosemide reduced osteopontin expression, macrophage infiltration, transforming growth factor-beta expression, and interstitial fibrosis, but did not prevent the decrease in GFR. Treatment with losartan, but not with hydralazine and furosemide, markedly reduced arteriolopathy. It was concluded that angiotensin II contributes to the vasculopathy (hyalinosis) induced by CsA. In contrast, the interstitial fibrosis mediated by CsA can be partially prevented by both an angiotensin II Type I receptor antagonist or by hydralazine and furosemide. This suggests that the interstitial fibrosis can be dissociated from the vascular effects of CsA. The beneficial effects of lowering blood pressure or vasodilation per se may be difficult to distinguish from the specific effects of angiotensin II receptor blockade.

Interstitial collagenase (MMP-1) expression in human carotid atherosclerosis

BACKGROUND

In human atherosclerosis, most clinical events occur when plaque integrity is compromised and hemorrhage and thrombosis result. One mechanism for this might be the release by plaque cells of matrix-degrading proteases, such as interstitial collagenase (matrix metalloproteinase-1, MMP-1), which degrades two major plaque structural proteins, types I and III collagen. This study was undertaken to determine whether MMP-1 is expressed in human atherosclerotic plaques.

METHODS AND RESULTS

To determine the cellular source and location of MMP-1 in human carotid atherosclerotic lesions, in situ hybridization and immunohistochemistry were performed on 20 endarterectomy specimens. Six nonatherosclerotic carotid arteries also were studied. Intense MMP-1 expression (mRNA and protein) was detected in a subset of plaque macrophages located at the borders of the lipid cores adjacent to fibrous caps and shoulder regions. Subsets of plaque smooth muscle cells and endothelial cells also expressed MMP-1. There was a strong correlation between the percentage of the lipid core occupied by hemorrhage and the percentage of the lipid core perimeter positive for MMP-1 (r = .823, P = .0001). MMP-1 was not detected in any cell type in nonatherosclerotic carotid arteries.

CONCLUSIONS

This study demonstrates that MMP-1 is expressed by several cell types in human carotid atherosclerosis and that there is a correlation between the expression of the protease and histopathological evidence of plaque instability. Since MMP-1 may degrade the major structural collagens of the plaque, expression of the protease by macrophages in regions critical to plaque integrity could contribute to plaque expansion, rupture, and hemorrhage.

Hepatitis C virus associated membranous glomerulonephritis

Hepatitis C virus infection has been associated with a variety of extrahepatic disorders. We report four patients with membranous glomerulonephritis and hepatitis C virus infection. In contrast to patients previously reported with HCV infection and membranoproliferative glomerulonephritis, these patients have normal or minimally reduced complement levels and no evidence of rheumatoid factor or cryoglobulinemia. A liver biopsy in one patient was consistent with chronic active hepatitis although liver enzymes were only minimally elevated and coagulation studies normal. Three patients were treated with alpha-interferon with some success. Treatment with alpha-interferon may have a beneficial effect in reducing proteinuria and improving liver function and may be related to the ability of interferon to suppress viremia. Future studies need to focus on clarifying the role of the virus in causing glomerular disease and improving dosing strategies for alpha-interferon. Randomized, controlled studies need to be performed to determine whether the beneficial effect of alpha interferon is significant, and if so, if it is superior to conventional therapies.

Cellular proliferation and macrophage influx precede interstitial fibrosis in cyclosporine nephrotoxicity

Chronic cyclosporine (CsA) nephrotoxicity is a major complication of solid organ transplantation, and is characterized histologically by striped tubulointerstitial fibrosis, tubular atrophy, and hyalinization of the afferent arteriole, a highly specific finding in cyclosporine injury. The salt-depleted rat model of chronic cyclosporine nephropathy mimics these lesions in humans. We conducted sequential studies of this model in groups of pair fed rats (N = 6) treated with CsA (15 mg/kg, s.q.) or an equivalent dose of olive oil. Proliferation of tubular and interstitial cells was documented early in the medulla by day 5 (3.2 +/- 2.1 vs. 0.81 +/- 0.4 cells/HPF in CsA vs. control, P < 0.02), and was maximal in areas of interstitial fibrosis by day 35 (7.9 +/- 3.7 vs. 0.52 +/- 0.2 cells/HPF in CsA vs. control, P < 0.005). The interstitial fibrosis was associated with a significant macrophage influx by day 35 (13.9 +/- 3.5 vs. 1.5 +/- 0.32 cells/HPF, CsA vs. control, P < 0.005), which correlated with increased cortical tubular staining for the macrophage adhesion protein, osteopontin. Elevated serum creatinine correlated with interstitial fibrosis at day 35 (0.85 +/- 0.11 vs. 0.40 +/- 0.03 mg/dl Cr, CsA vs. control, P < 0.005) by linear regression (r = 0.9, P < 0.05). Medullary proliferation and interstitial fibrosis correlated with decreased tubular concentrating ability, and higher urinary volume. Cortical interstitial fibrosis was maximal at day 35 and was associated with an increase in type I and type IV collagen deposition, while tubular injury was associated with increased vimentin expression. Tubular interstitial cells also expressed increased vimentin early in the medulla (day 10) and later in the cortex. Both groups remained normotensive despite significantly elevated juxtaglomerular (JG) apparatus renin expression in CsA treated animals, implicating the intrarenal-renal renin-angiotensin system in this disease. We conclude that cyclosporine nephrotoxicity is associated with early tubular and interstitial cell proliferation, and a significant macrophage influx that precedes the development of cortical interstitial fibrosis and afferent arteriolar hyalinosis. These early cellular changes correlate with functional abnormalities including decreased creatinine clearance (CCr) and decreased medullary concentrating ability, which stabilized despite progressive fibrosis. These cellular events may be important in the pathogenesis of chronic CsA nephrotoxicity.

Cyclosporine A induced arteriolopathy in a rat model of chronic cyclosporine nephropathy

Chronic cyclosporine (CsA) nephrotoxicity is a major complication of heart, bone marrow, and renal transplantation, and is characterized in humans by striped interstitial fibrosis, tubular dilatation and atrophy, and hyalinization of hilar arterioles. This last feature is highly specific for cyclosporine injury and has been difficult to reproduce in normotensive animal models. Salt-depletion has been shown to sensitize rodents to the effects of CsA and accelerate the disease process. We conducted sequential studies in chronically salt depleted, pair fed rats treated with CsA (15 mg/kg, s.c.) or an equivalent dose of olive oil vehicle, and found a histologic lesion associated with CsA that consisted of striped cortical interstitial fibrosis, tubular dilatation and atrophy, and hyalinization of many afferent arterioles. The arteriolopathy was first detected at day 10 with progressive hyalinization of arterioles continuing until termination of the study at day 35. The arteriolopathy consisted initially of eosinophilic granular transformation of smooth muscle cells comprising afferent hilar glomerular arterioles, and progressed to foci of smooth muscle cell vacuolization and accumulation of discrete hyaline deposits in vessel walls. Electron microscopy demonstrated marked accumulation of typical renin granules throughout the smooth muscle cell cytoplasm, corresponding to the eosinophilic granular transformation revealed histologically. Immunocytochemistry confirmed the up-regulated production of renin in these vessels. This study documents a rodent model for CsA arteriolopathy and CsA-associated interstitial fibrosis that strikingly reproduces the most characteristic nephropathic effects of cyclosporine found in human patients treated with this agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet-derived growth factor A-chain expression in developing and mature human kidneys and in Wilms' tumor

Regulated expression of PDGF A-chain may be important in kidney development. We employed two polyclonal antisera to detect expression of PDGF A-chain in fetal and normal adult kidneys by immunohistochemistry. Specificity of the antisera was demonstrated by Western blots of fetal and adult kidneys, demonstrating monospecific bands at 10 to 15 kD, and by absorption studies with PDGF-A peptide. PDGF A-chain is uniformly expressed by visceral glomerular epithelial cells and the epithelial cells of the distal nephron, including collecting ducts and contiguous urothelium lining the renal pelvis, in both fetal and adult kidneys. Fetal kidneys also demonstrate expression of PDGF A-chain at the earliest stages of vesicle formation from the metanephric blastema; this expression is then only intermittently detectable in developing glomeruli until differentiation of visceral epithelial cells occurs. Fetal and mature arterial smooth muscle cells, and some express PDGF A-chain. In situ hybridization with a riboprobe made from PDGF A-chain cDNA showed close correlation of mRNA expression with protein immunohistochemistry. PDGF A-chain expression was also identified in epithelial elements of 5/6 Wilms' tumors studied. These are the first studies to localize PDGF A-chain expression in human kidney and suggest sites of activity for PDGF A-chain in development, neoplasia, and in the renal arterial sclerosis of aging.

Hepatitis C virus-associated glomerulonephritis

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease and is associated with a variety of extrahepatic manifestations, including cryoglobulinemia and glomerulonephritis. Epidemiologic evidence suggests that HCV infection may be a major risk factor for both cryoglobulinemic and type I membranoproliferative glomerulonephritis (MPGN). Clinical symptoms and laboratory data may or may not reflect the presence of chronic liver disease. Most patients have evidence of hypocomplementemia, circulating rheumatoid factors, and cryoglobulinemia. The pathogenesis of HCV-associated MPGN is probably a result of glomerular deposition of circulating HCV and anti-HCV antibodies. Treatment with interferon-alpha has been shown to improve proteinuria, suppress viremia, and stabilize renal function. However, patients often relapse after therapy is stopped. The optimal therapy remains to be defined but may involve different dosage regimens of interferon-alpha or the combination of several antiviral agents.

Hepatitis C--associated glomerular disease in liver transplant recipients

Hepatitis C virus (HCV) infection may be associated with extrahepatic illness including renal disease. We investigated the clinical and virological characteristics of three patients who developed a mesangial proliferative and sclerosing glomerulopathy alone or in association with membranoproliferative glomerulonephritis after liver transplantation for end-stage liver disease secondary to HCV infection. Using polymerase chain reaction technology and the IgM RIBA assay, viral load, genotype and IgM antibody response to HCV in the setting of glomerulonephritis was evaluated. Within 1 year of transplantation, the patients showed decreased renal function, proteinuria and recurrent hepatitis C liver disease. Likewise, HCV viral load increased following transplantation, whereas the viral genotypes remained unchanged. Although the first patient presented with classic type II cryoglobulinemia in association with glomerulonephritis, the second patient developed an IgM directed specifically against the hepatitis C core antigen. The third patient developed a low-titered IgM directed against the hepatitis C core antigen with rheumatoid factor activity but without cryoglobulinemia. All of the patients show IgM in glomerular capillary walls by biopsy. One patient has shown a clinical response to interferon (IFN) alfa-2b therapy without evidence of hepatic allograft rejection. The second and third patients have not responded to IFN or developed hepatic rejection. This study suggests that HCV-associated glomerulonephritis may complicate liver transplantation in conjunction with the production of increased amounts of IgM of variable specificity. The posttransplant setting may provide a unique situation in which to investigate the specific requirements for the onset of renal disease.

Cellular events in the evolution of experimental diabetic nephropathy

In several models of progressive glomerular disease, mesangial cell proliferation, phenotypic change and increased growth factor expression precede up-regulation of genes for extracellular matrix components (ECM) and mesangial expansion. To examine these events in diabetic nephropathy (DN) we conducted sequential studies of glomeruli in rats with streptozotocin induced DN. We found prominent mesangial cell proliferation at three days (4.34 +/- 2.24 PCNA + cells/glom vs. 1.6 +/- 0.74 in controls, P < 0.001) associated with increased alpha-actin expression. PDGF B-chain mRNA was slightly increased at day one, and PDGF B-chain immunostaining was slightly increased at days one and six. Staining for bFGF was significantly increased at three days (2.2 +/- 0.6 vs. 1.2 +/- 0.1 in controls, P < 0.01). There was also an early increase in platelets in glomeruli of diabetic animals, and platelet depletion significantly inhibited the early phase of proliferation. In addition to mesangial cell proliferation, a prominent glomerular macrophage infiltration began at day three and peaked at day 30 (3.94 +/- 1.47 vs. 2.08 +/- 1.13 in controls, P < 0.01). TGF-beta mRNA increased at days 14 and 30. Insulin treatment prevented mesangial cell proliferation, actin expression, and macrophage infiltration, and normalized TGF-beta expression at 14 and 30 days. These multiple cellular events preceded any detectable increases in glomerular gene expression or deposition of collagen I, IV or laminin.