Ischemia-induced transplant arteriosclerosis in the rat. Induction of peptide growth factor expression

Novel Biomarkers for Evaluation of Endothelial Dysfunction

Endothelial dysfunction is one of the earliest indicators of cardiovascular (CV) dysfunction, and its evaluation would be of considerable importance to stratify CV risk of many diseases and to assess the efficacy of atheroprotective treatments. Flow-mediated dilation is the most widely used method to study endothelial function. However, it is operator-dependent and can be influenced by physiological variations. Circulating biomarkers are a promising alternative. Due to the complexity of endothelial function, many of the biomarkers studied do not provide consistent information about the endothelium when measured alone. New circulating markers are being explored and some of them are thought to be suitable for the clinical setting. In this review, we focus on novel biomarkers of endothelial dysfunction, particularly endothelial microparticles, endocan, and endoglin, and discuss whether they fulfill the criteria to be applied in clinical practice.

Hypercholesterolemia leads to elevated TGF-beta1 activity and T helper 3-dependent autoimmune responses in atherosclerotic mice

OBJECTIVE

The pathogenesis of atherosclerosis involves inflammation and immune reactions. Low-density lipoproteins accumulate and are oxidized (oxLDL) in the arterial intima during hypercholesterolemia, leading to activation of endothelial cells, macrophages and T cells. We have previously found that severe hypercholesterolemia can induce a switch of autoimmune responses from T helper (Th)1 to Th2 effector type in atherosclerotic apoE knockout (E0) mice. The present study was performed to investigate whether Th3 immune effector responses and their inducing cytokine, transforming growth factor-beta (TGF-beta) are affected by hypercholesterolemia.

METHODS AND RESULTS

In E0 mice fed with high cholesterol diet and in C57BL/6J mice treated with poloxamer P-407, an agent that elevates plasma cholesterol and triglycerides, severe hypercholesterolemia led to elevated circulating TGF-beta1 levels, increased TGF-beta1(+)CD4(+) Th3 cells in lesions and spleen, and increased Th3 dependent IgG2b antibodies to oxLDL. A positive correlation was observed between plasma TGF-beta1 and cholesterol levels and between plasma TGF-beta1 and IgG2b anti-oxLDL.

CONCLUSIONS

Such elevation of TGF-beta may increase the stability of plaques by inhibiting T cell responses and macrophage activation and by stimulating collagen synthesis. This new finding could be important in the regulation of immune activity, inflammation and fibrosis in the atherosclerotic plaque.

Atorvastatin attenuates transplant-associated coronary arteriosclerosis in a murine model of cardiac transplantation

Accelerated coronary arteriosclerosis remains a major problem for the long-term survival of cardiac transplant recipients. However, the pathogenesis of transplant vasculopathy is poorly understood and there is no effective therapy. HMG-CoA reductase inhibitors, or statins, are widely prescribed to lower plasma cholesterol level. Accumulating evidence indicates that statins have various effects on vascular cells which are independent of their lipid-lowering effect. We investigated whether orally administered atorvastatin, one of the most potent statins, inhibits the development of intima hyperplasia in a mouse model of cardiac transplantation. Cardiac allografts from DBA mice were transplanted heterotopically into B10.D2 mice. Mice were administered either vehicle or atorvastatin everyday by gavage. Morphometrical analysis revealed that atorvastatin significantly reduced the development of coronary arteriosclerosis on the cardiac allografts harvested at one month. Immunohistochemical analysis revealed that atorvastatin attenuated infiltration of inflammatory cells with reduced expression of TGF-beta and adhesion molecules. These results suggest that atorvastatin may be effective in preventing transplant-associated arteriosclerosis along with other immunosuppressive agents.

Trophic factor supplemented UW solution reduces intimal hyperplasia in the rat aortic transplant model

BACKGROUND

Chronic allograft nephropathy (CAN) is associated with delayed graft function, cold ischemic injury, and is an important cause of premature graft loss. A characteristic vascular lesion of CAN is intimal hyperplasia (IH). The goal of this study was to evaluate the effect of cold storage in University of Wisconsin solution supplemented with trophic factors (UW-TF) on IH in rat aortic isograft (IG) and allograft (AG) models.

METHODS

F344 --> F344 and Lewis --> F344 orthotopic abdominal aortic transplants were performed after 48 h of cold storage in either UW or UW-TF solution with and without immunosuppression.

RESULTS

Significant reduction in IH was observed when IG were stored in UW-TF solution compared to UW solution. A significant reduction in intimal inflammation was observed in UW-TF stored, nonimmunosuppressed AG. In immunosuppressed recipients, AG stored in UW-TF solution evidenced significantly less IH compared to those stored in UW alone.

CONCLUSIONS

UW-TF solution decreased IH in both alloindependent and dependent models.

Increased mRNA Expression of Transforming Growth Factor Beta in the Arterial Wall of Chronically Rejected Renal Allografts in Humans

INTRODUCTION

Transforming growth factor beta (TGF-beta) has an established role in interstitial damage of renal transplants during chronic rejection (CR). However, its involvement in transplant vasculopathy is not clear. The aim of the study was to assess TGF-beta gene expression in the walls of large-caliber arteries within chronically rejecting renal allografts. We evaluated associations between gene expression of this factor and intimal thickness or clinical data.

MATERIAL AND METHODS

Renal artery samples of kidney allografts were obtained from 20 hemodialysis patients with end-stage renal graft disease due to CR, who were undergoing graftectomy. The control group included 32 hemodialysis patients with end-stage renal disease, undergoing nephrectomy due to autosomal dominant polycystic kidney disease (n = 12), chronic pyelonephritis (n = 13), or kidney limited tumor (n = 7). Gene expression of TGF-beta was measured using real-time PCR.

RESULTS

TGF-beta mRNA expression was 3.25-fold higher in CR than in control patients (P < .001). Expression of mRNA for this cytokine was not influenced by the following factors: intimal thickness; age; serum cholesterol, triglycerides and glucose; BMI; graft survival; time of dialysis before transplantation; total ischemic time; immunosuppressive regimen; incidence of acute rejection episode; panel reactive antibodies; and period of dialysis before graftectomy. TGF-beta is involved in neointimal formation in CR.

Effect of fluvastatin on renal end points in the Assessment of Lescol in Renal Transplant (ALERT) trial

BACKGROUND

Hyperlipidemia is a risk factor for long-term renal transplant dysfunction, but no prospective clinical trials have investigated the effects of statin treatment on graft function in renal transplant recipients. The aim of the present study was to evaluate the effect of fluvastatin on long-term renal transplant function and development of chronic allograft nephropathy in the ALERT (Assessment of Lescol in Renal Transplantation) study.

METHODS

ALERT was a randomized, double-blind, placebo-controlled study of the effect of fluvastatin, 40 mg and 80 mg daily, in renal transplant recipients. Patients were randomized to receive either fluvastatin (N= 1050) or placebo (N= 1052) and followed for five to six years. Renal end points included graft loss or doubling of serum creatinine or death; glomerular filtration rate (GFR) was also measured during follow-up in a subset of patients (N= 439).

RESULTS

There were 283 patients (13.5%) with graft loss, mainly due to chronic rejection (82%), yielding an annual rate of 2.4%. Fluvastatin treatment significantly lowered mean low-density lipoprotein (LDL)-cholesterol levels by 32% (95% CI -33 to -30) compared with placebo, but had no significant effect on the incidence of renal graft loss or doubling of serum creatinine, or decline in GFR throughout follow-up in the whole study population. Neither was any treatment effect by fluvastatin found in any of the subgroups analyzed.

CONCLUSION

Fluvastatin treatment significantly improves lipid values in renal transplant recipients but has no effect on graft loss or doubling of serum creatinine.

Role of E2F and ERK1/2 in STI571-mediated smooth muscle cell growth arrest and cyclin A transcriptional repression

Platelet-derived growth factor (PDGF) ligand and receptors (PDGF-R) activate smooth muscle cell (SMC) proliferation, a key event during vascular obstructive disease. The PDGF-R tyrosine kinase inhibitor STI571 attenuates SMC proliferation and experimental neointimal thickening. Here, we investigated the molecular mechanisms underlying STI571-dependent SMC growth arrest. STI571 abrogates PDGF-BB-dependent cyclin D1 and cyclin A protein expression and inhibits transcriptional activation of reporter genes driven by the human cyclin A gene promoter. Repression of cyclin A promoter activity by STI571 requires a functional E2F-binding site, and forced expression of E2F overrides this inhibitory effect. Moreover, STI571 inhibits E2F DNA-binding activity in SMCs. We also found that STI571 abrogates PDGF-BB-dependent activation of extracellular-regulated kinase 1 and 2 (ERK1/2), and forced activation of these factors impaired STI571-dependent inhibition of both cyclin A promoter activity and SMC proliferation. Thus, E2F and ERK1/2 play an important role in STI571-mediated SMC growth arrest and cyclin A transcriptional repression. These findings may have importance in the development of novel therapeutic strategies for the treatment of neointimal hyperplasia.

Latent transforming growth factor-beta binding protein-1, a component of latent transforming growth factor-beta complex, accelerates the migration of aortic smooth muscle cells in diabetic rats through integrin-beta3

Aortic smooth muscle cells (SMCs) of diabetic animals have unique properties, including the overexpression of transforming growth factor-beta (TGF-beta) type II receptor, fibronectin, and platelet-derived growth factor beta-receptor. TGF-beta1 is produced and secreted as latent high-molecular weight complex consisting of mature TGF-beta1, latency-associated peptide (LAP), and a latent TGF-beta1 binding protein (LTBP-1). LAP has an important function in the latency of TGF-beta complex, but the role of LTBP-1 is not known in diabetic angiopathy. SMC migration from the medial layer to the intimal layer of an artery is an initial major process of the formation of intimal thickening of an artery. Migration activities of SMCs from diabetic rat with 1-500 pg/ml of LTBP-1 increased significantly compared with that without LTBP-1. LTBP-1 at 10-500 pg/ml stimulated the migration of diabetic SMCs more than SMCs from control rat. An anti-integrin-beta(3) antibody reduced LTBP-1-stimulated migration of diabetic SMCs to 51% compared with no antibody, but it did not reduce that of control SMCs. Furthermore, cross-linking experiments show that LTBP-1 binds integrin-beta(3) in diabetic SMCs much more than in control SMCs in coincidence with the increase of integrin-beta(3) in diabetic aorta by immunohistochemistry. Taken together, these observations suggest that LTBP-1 plays a critical role in intimal thickening of diabetic artery through the acceleration of SMC migration via integrin-beta(3).

Novel PDGFbetaR antisense encapsulated in polymeric nanospheres for the treatment of restenosis

Nanospheres composed of the biocompatible and biodegradable polymer, poly-DL-lactide/glycolide and containing platelet-derived growth factor beta-receptor antisense (PDGFbetaR-AS) have been formulated and examined in vitro and in vivo in balloon-injured rat restenosis model. The nanospheres (approximately 300 nm) of homogenous size distribution exhibited high encapsulation efficiency (81%), and a sustained release of PDGFbetaR-AS (phosphorothioated). Cell internalization was visualized, and the inhibitory effect on SMC was observed. Partially phosphorothioated antisense sequences were found to be more specific than the fully phosphorothioated analogs. A significant antirestenotic effect of the naked AS sequence and the AS-NP (nanoparticles) was observed in the rat carotid in vivo model. The extent of mean neointimal formation 14 days after injection of AS-NP, measured as a percentage of luminal stenosis, was 32.21 +/- 4.75% in comparison to 54.89 +/- 8.84 and 53.84 +/- 5.58% in the blank-NP and SC-NP groups, respectively. It is concluded that PLGA nanospheres containing phosphorothioated oligodeoxynucleotide antisense could serve as an effective gene delivery systems for the treatment of restenosis.

Increased expression of TGF-beta1 and IGF-I in inflammatory stenotic lesions of hemodialysis fistulas

BACKGROUND

Hemodialysis fistula dysfunction due to stenotic lesions remains a frequent cause of hospitalization for hemodialysis patients. Transforming growth factor-beta(TGF-beta) and insulin-like growth factor-I (IGF-I) are known to be involved in atherogenesis. The latent TGF-beta1 binding protein-1 (LTBP-1) targets extracellular matrix (ECM) interactions and is involved in the regulation of TGF-beta latency.

METHODS

We investigated the expression of TGF-beta1, LTBP-1 and IGF-I in 15 occluded or severely narrowed vein segments of primary arteriovenous fistulas, in 29 non-stenosed control veins from uremic, pre-dialysis patients, and in 15 non-stenosed control saphenous veins obtained from patients undergoing aortocoronary bypass grafting. Immunohistochemistry was performed on snap-frozen tissue specimens using antibodies recognizing either the latency-associated peptide of TGF-beta1 (96-1), LTBP-1 (Ab39) or IGF-I. Serum levels of TGF-beta1 and IGF-I were determined by commercially available IRMA.

RESULTS

In stenosed hemodialysis fistulas, a pronounced intimal thickening with deposition of ECM was observed with light and electron microscopy. Infiltrating cells were seen in stenosed vessels, mostly in areas of intimal hyperplasia and in the media. TGF-beta1, LTBP-1 and IGF-I expression were mostly localized in the neointimal and medial layers, and were significantly higher than in the control groups. A positive correlation between the presence of inflammatory cells and the staining intensity for TGF-beta1, LTBP-1 and IGF-I was found in all vessels analyzed.

CONCLUSION

Neointimal thickening of primary arteriovenous fistulas represents a local inflammatory process and appears to be associated with increased protein expression of TGF-beta1 and IGF-I. While local IGF-I is likely to stimulate smooth muscle cell proliferation in this setting, TGF-beta1 may be an important trigger of ECM production and deposition.

Tranilast inhibits transplant-associated coronary arteriosclerosis in a murine model of cardiac transplantation

Accelerated coronary arteriosclerosis remains a major problem for the long-term survival of cardiac transplant recipients. However, the pathogenesis of graft vasculopathy is poorly understood and there is no effective therapy. Tranilast is a promising drug that may prevent post-angioplasty restenosis. Here, we investigated whether orally administered tranilast inhibits the development of intima hyperplasia in a mouse model of cardiac transplantation. Cardiac allografts from BALB/c mice were transplanted heterotopically into C3H/He mice. Mice were administered either vehicle or tranilast everyday by gavage. Morphometrical analysis of the cardiac allografts harvested at 2 months revealed that the administration of tranilast significantly reduced the development of coronary atherosclerosis. In the mice treated with tranilast, up-regulation of the cyclin-dependent kinase inhibitor p21 was observed in the allografts, accompanied by a reduced number of proliferating cells. Tranilast also suppressed transforming growth factor-beta (TGF-beta) expression. Tranilast may be effective in preventing transplant-associated arteriosclerosis through its anti-inflammatory and anti-proliferative effects.

Fas ligand overexpression on allograft endothelium inhibits inflammatory cell infiltration and transplant-associated intimal hyperplasia

Despite recent advances in immunosuppressive therapy, accelerated coronary atherosclerosis remains a major problem in the long-term survival of transplant recipients. Chronic graft vasculopathy is believed to result from recipient inflammatory responses, and it is characterized by early mononuclear cell infiltration of the transplanted vessel. Here we show that endothelial cells can be genetically modified to overexpress functional, cell-surface Fas ligand (FasL) by adenovirus-mediated gene transfer without undergoing self-destruction. In a rodent model of transplant graft vasculopathy, endothelial overexpression of FasL attenuated T cell and macrophage infiltration at 1 wk posttransplantation. These vessels also displayed reduced neointima formation at one and 2 mo posttransplantation. These results indicate that inhibition of the early inflammatory response to allografted vessels by endothelial cell-specific overexpression of FasL may have utility in the treatment of transplant arteriosclerosis.

Candesartan cilexetil reduces graft arteriosclerosis in aortic transplantation model in rat

To date established treatment of transplant arteriosclerosis is basically missing and there is a need for new therapeutic approaches. Angiotensin II (Ang II) and Ang II receptor type 1 (AT) are present in the vascular wall. Blocking of the AT1 receptor by pharmacological agents may inhibit damaging effects of Ang II on endothelial and smooth muscle cells. The purpose of the study was to evaluate the effect of the AT1 receptor blocker Candesartan cilexetil on the development of graft arteriosclerosis in a rat aortic transplant model. Two strain combinations were used for aortic transplantation: DA to PVG; and PVG to PVG. The animals received Candesartan cilexetil treatment (9.5 + 1.4 mg/kg/day) for 8 weeks. Candesartan cilexetil treatment reduced neointimal formation both in allografts (Qint 30.2 +/- 8.8% vs. 22.1 +/- 8.7%, P < 0.05) and in isografts (Qint 15.5 +/- 4.4% vs. 6.7 +/- 3.3%, P = 0.0001). Blocking of the AT1 receptor signalling by Candesartan cilexetil was also associated with a reduced expression of TGF-beta1. Macrophage infiltration was not affected by the treatment. Candesartan cilexetil treatment leads to reduced neointimal formation in aortic transplant. The positive effect of the drug might be partly explained by a reduction of TGF-beta1 expression in the grafts. Candesartan treatment may provide another possibility for prevention of transplant arteriosclerosis and chronic rejection.

The significance of CD105, TGFbeta and CD105/TGFbeta complexes in coronary artery disease

We have quantified levels of CD105, its ligand TGFbeta and receptor-ligand complexes in sera from healthy individuals (n=31), patients with triple vessel disease documented by coronary angiography (TVD; n=36) and patients with chest pain and a positive exercise electrocardiogram but with normal coronary angiogram (NCA; n=30). Both active TGFbeta1 and active plus acid-activatable TGFbeta1 [(a+l)TGFbeta1] were significantly depressed in patients with TVD compared with the other two groups (P</=0.04). CD105 levels in TVD patients were also diminished but elevated in NCA patients. In contrast, patients with TVD had more CD105/TGFbeta1 complex in their sera than the other two groups, suggesting that this may be the reason why TVD patients had low levels of receptor and ligand. TGFbeta3 levels were similar in the three groups, but elevated CD105/TGFbeta3 levels were noted in patients with NCA compared with those with TVD and healthy individuals (P< or =0.02). CD105 was correlated with both active TGFbeta1 and (a+l)TGFbeta1 (P=0.02). CD105 also strongly correlated with TGFbeta3 and CD105/TGFbeta3 complexes (P=0.001 in both cases). The changes in levels of CD105, TGFbeta1 and the receptor-ligand complexes in sera of patients with atherosclerosis suggest that these molecules may be important in the pathobiology of the atherosclerotic disease. Further studies on sequential samples from a larger cohort of patients are needed to define a causal relationship between these molecules and the disease progression.

Intragraft platelet-derived growth factor-alpha and transforming growth factor-beta1 during the development of accelerated graft vascular disease after clinical heart transplantation

This study was to determine whether the growth factors platelet-derived growth factor-alpha (PDGF-alpha) and transforming growth factor-beta1 (TGF-beta1) contribute to the development of graft vascular disease (GVD) after clinical heart transplantation. We analysed intragraft PDGF-alpha and TGF-beta1 messenger RNA (mRNA) expression levels by competitive template reverse transcriptase polymerase chain reaction (RT-PCR). Endomyocardial biopsies (EMB) were obtained at 1 and 9 months post-transplant from cardiac allograft recipients with (n = 11) and without (n = 11) angiographic evidence of GVD at 1 year. In 1-month EMB, comparable TGF-beta1 mRNA levels were found in patients with and without GVD at 1 year (p = 0.84, Mann-Whitney U-test). In contrast, in 9-month EMB during the development of GVD, intragraft mRNA levels of both PDGF-alpha (p = 0.08) and TGF-beta1 (p = 0.03) were higher in patients with GVD after the first year compared to patients without GVD. These results suggest that intragraft PDGF-alpha and TGF-beta1 play a role in the pathogenesis of accelerated GVD after clinical heart transplantation.

Estrogen replacement inhibits intimal hyperplasia and the accumulation and effects of transforming growth factor beta1

BACKGROUND

The role of estrogens in providing atheroprotection has been well documented in both epidemiologic and experimental studies. This phenomenon has traditionally been attributed to the beneficial lipid-modifying effects of estrogens. Previous studies have used models of either diet- or injury-induced atherosclerosis. As such, the interrelationship between estrogens, lipids, and atherosclerosis remains unclear. We hypothesized that estrogens are atheroprotective independent of changes in serum lipids by directly influencing the accumulation and effects of the peptide growth factor transforming growth factor beta1 (TGF-beta1).

MATERIAL AND METHODS

Thirteen female sheep (8 years old) were randomized to sham, ovariectomy, or ovariectomy with 17beta-estradiol replacement. Serum lipid levels were serially measured. At 9 months, necropsy was performed with histologic morphometric analysis of the aortoiliac bifurcation. Levels of TGF-beta1 were determined in serum and aortic tissue. Human aortic smooth muscle cells were isolated and cultured.

RESULTS

Serum triglyceride, lipoprotein a, and total, low-density lipoprotein, and high-density lipoprotein cholesterol levels were similar and normal between groups. Ovariectomy resulted in aortoiliac intimal hyperplasia compared with sham (P < 0.001) and hormone replacement (P < 0.001) groups. Compared with ovariectomy, estrogen replacement attenuated aortic accumulation of TGF-beta1 (P < 0.02). In vitro, estradiol potentiated TGF-beta1 inhibition of human vascular smooth muscle cell (VSMC) proliferation and increased TGF-beta1 release in stimulated VSMCs (P < 0.001).

CONCLUSIONS

Without dietary manipulation, ovarian ablation induces aortic intimal hyperplasia in the ewe. Estradiol abrogates this response independently of its effects on serum lipids. Hormone replacement decreases the accumulation of TGF-beta1, suggesting that estrogens may provide atheroprotection both by modifying local production and by modulating the influence of TGF-beta1 on VSMC growth.

Eotaxin and capping protein in experimental vasculopathy

Ischemia-induced tissue activation may contribute to the pathogenesis of graft vasculopathy, but the mediators implicated have only partially been characterized. To gain further insight into the molecular mechanisms involved, syngeneic rat aortic transplants with cold-storage-induced vasculopathy were studied for differentially expressed mRNA transcripts. Vessel segments were exposed to either 1 or 18 hours of cold ischemia, followed by transplantation into syngeneic recipients. After 3 days or 4 weeks, the grafts were removed and total mRNA was isolated and used for differential display to identify modulation of transcript expression related to prolonged storage. Using 15 sets of random primers, 17 polymerase chain reaction products were up-regulated and 2 were downregulated in grafts exposed to 18 hours of ischemia. Sequencing of these amplicons showed that 6 had a high degree of homology to known sequences whereas 13 had no homology to any of the genes in the database. Two of the differentially displayed amplicons (capping protein and eotaxin) were cloned, re-amplified, and used as probes for Northern blot analysis to confirm their differential expression. Immunohistochemistry using monoclonal antibodies against capping protein-alpha and eotaxin confirmed that both proteins are expressed in the media of normal aortas and that there was an increased expression in vessels exposed to prolonged ischemia albeit that the increase at the protein level seemed less compared with changes in transcript expression. Northern blots with RNA from aortic allografts exposed to prolonged ischemic storage also showed increased levels of capping protein and eotaxin mRNA whereas there was a decrease in the relative amount of these transcripts in vessels exposed to balloon denudation, suggesting that the increase after prolonged ischemic exposure is not the result of a nonspecific response to injury. Based on the biological characteristics of capping protein and eotaxin it is conceivable that they play a pathogenetic role in ischemia-induced vessel wall remodeling. It remains to be established whether these genes or their products serve as target molecules for therapeutic interventions to prevent or treat cold-storage-induced graft vasculopathy.

Tolerance induction ameliorates allograft vasculopathy in rat aortic transplants. Influence of Fas-mediated apoptosis

Based on successful induction of donor-specific unresponsiveness by alloantigenic stimulation in several animal models of acute rejection, we hypothesized that similar immune manipulations would also inhibit the evolution of chronic rejection and transplant vasculopathy. To induce immune tolerance, DA rats received a PVG heart allograft and were immunosuppressed with cyclosporine for 30 d. At day 100 the animals were challenged with a PVG aortic allograft after either 1 or 18 h of cold ischemia. 8 wk after the aortic transplantation, the grafts were investigated for morphological changes, infiltrating cells, apoptosis, and Fas-Fas ligand expression. Control allografts showed advanced transplant arteriosclerosis, whereas tolerance-induced aortic allografts displayed reduced neointimal formation, less medial atrophy, fewer apoptotic cells, and fewer Fas- and FasL-expressing cells. Prolonged ischemic storage time did not profoundly alter the morphological changes of the allografts. Fas expression was found in T cells, macrophages, vascular smooth muscle cells, and endothelial cells, whereas FasL was expressed mainly by T cells and macrophages. FasL mRNA expression was evident throughout the entire allograft wall. In conclusion, induction of allospecific tolerance can effectively prevent transplant arteriosclerosis. Cold ischemia damage does not abrogate the beneficial effect of tolerance, but creates a separate identity of mainly endothelial lesions. Furthermore, Fas-mediated apoptosis appears to be involved in the pathological lesions seen in chronic rejection.

Role of latent TGF-beta 1 binding protein in vascular remodeling

Transforming growth factor-beta (TGF-beta) is secreted as a latent, high molecular weight complex, which is composed of TGF-beta, a latency associated peptide (LAP) and a latent TGF-beta binding protein (LTBP). In this study, we report on the role of LTBP in vascular remodeling. 0.01-5 ng/ml of LTBP stimulated the migration activities of cultured rat arterial smooth muscle cells (SMC) about 4-7 fold compared with control in vitro. The maximal activity of SMC migration by LTBP was 75% of that by 10 ng/ml of PDGF-BB. A checker board analysis showed that the migration by LTBP was chemotactic, not chemokinetic. By cross-linking experiment, LTBP associated with 80-120 kd cell surface protein of SMC, suggesting that a part of LTBP can bind with SMC. Furthermore, LTBP was more strongly expressed in the intimal layer than in the medial layer of BCI artery. These results suggest that LTBP plays an important role in the initial stage of arterial intimal thickening through the acceleration of SMC migration from the medial to intimal layer and is one of the essential factors influencing vascular remodeling.

Increased immunoreactivity of transforming growth factor-beta in human kidney transplants

Transforming growth factor-beta (TGF-beta) has been known to be involved in the pathogenesis of various kidney diseases. TGF-beta is also a potent immunosuppressor that has been shown to be induced after allogeneic transplantation. We have studied the distribution of immunoreactive TGF-beta proteins in different compartments of 21 allogeneic transplanted kidneys that had been rejected through acute (eight interstitial or six vascular) and chronic (seven vascular) processes. This distribution was compared with that in seven non-rejected transplanted and five non-transplanted kidneys with intact morphology. There were no obvious differences between the three groups of rejected grafts and the transplanted non-rejected group for the expression of TGF-beta s. A major difference was seen between transplanted kidneys, which exhibited clearly positive TGF-beta and LTBP1 (latent TGF-beta binding protein) immunoreactivities, and the non-transplanted kidneys. The non-transplanted kidneys showed only very weak or no immunoreactivity for these proteins. The morphologically intact non-rejected grafts showed a significantly increased immunoreactivity compared with the non-transplanted kidneys. When the transplanted kidneys were classified into two groups (i.e. with or without diabetes mellitus) and compared with regard to the expression of all TGF-beta s, no difference was found. Thus, transplantation was the most important predictor for expression of TGF-beta s and LTBP1, and the largest expression increase in the allografts occurred in the interstitium, followed by the glomeruli and blood vessels. Tubuli and lymphocyte aggregates stained only faintly. The results imply that TGF-beta is induced rapidly after kidney transplantation. This induction can suppress immunoreactivation, but concomitantly promotes changes such as arteriosclerosis and fibrosis associated with rejection.