Vascular endothelial growth factor expression in human chronic renal allograft rejection

Pro- and anti-fibrotic effects of vascular endothelial growth factor in chronic kidney diseases

Renal fibrosis is the inevitable common end-point of all progressive chronic kidney diseases. The underlying mechanisms of renal fibrosis are complex, and currently there is no effective therapy against renal fibrosis. Renal microvascular rarefaction contributes to the progression of renal fibrosis; however, an imbalance between proangiogenic and antiangiogenic factors leads to the loss of renal microvasculature. Vascular endothelial growth factor (VEGF) is the most important pro-angiogenic factor. Recent studies have unraveled the involvement of VEGF in the regulation of renal microvascular rarefaction and fibrosis via various mechanisms; however, it is not clear whether it has anti-fibrotic or pro-fibrotic effect. This paper reviews the available evidence pertaining to the function of VEGF in the fibrotic process and explores the associated underlying mechanisms. Our synthesis will help identify the future research priorities for developing specialized treatments for alleviating or preventing renal fibrosis. Abbreviation: VEGF: vascular endothelial growth factor; CKD: chronic kidney disease; ESKD: end-stage kidney disease; ER: endoplasmic reticulum; VEGFR: vascular endothelial growth factor receptor; AKI: acute kidney injury; EMT: epithelial-to-mesenchymal transition; HIF: hypoxia-inducible factor; α-SMA: α smooth muscle actin; UUO: unilateral ureteral obstruction; TGF-β: transforming growth factor-β; PMT: pericyte-myofibroblast transition; NO: nitric oxide; NOS: nitric oxide synthase; nNOS: neuronal nitric oxide synthase; iNOS: inducible nitric oxide synthase; eNOS: endothelial nitric oxide synthase; sGC: soluble guanylate cyclase; PKG: soluble guanylate cyclase dependent protein kinases; UP R: unfolded protein response

Association of Vascular Endothelial Growth Factor 936 C/T Gene Polymorphism with Renal Allograft Outcome: A Study from North India

The significance of vascular endothelial growth factor (VEGF) and its polymorphisms in renal allograft rejection has recently become the subject of extensive research. Recently, some studies have shown some role of VEGF in rejection episodes and graft survival. VEGF +936 C>T polymorphism is significant in the transcription regulation of VEGF. Herein, we report the results of a prospective, single-center study seeking an association of VEGF +936 C/T gene polymorphism and allograft rejection. One hundred and forty-seven kidney transplant recipients with age-and sex-matched controls were included in this study. VEGF 936 C/T genes were studied using restriction fragment length polymorphism analysis of the blood specimen of these patients. All patients were studied for allograft rejection, response to treatment, and overall graft survival. We found that CT genotype and T allele carrier state were associated with good graft outcomes (P = 0.008 and 0.002, respectively). There was a lower number of rejection episodes with T allele, although it was not a significant finding (P = 0.880). Our findings suggest that good graft outcome in kidney transplant recipients is associated with an increased frequency of the VEGF 936 CT genotype and T allele, and that determination of the T allele might be helpful for the identification of recipients with overall good graft survival.

Inhibition of Vascular Endothelial Growth Factor Receptors 1 and 2 Attenuates Natural Killer Cell and Innate Immune Responses in an Experimental Model for Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) after lung transplantation is a nonreversible, life-threatening complication. We investigated the role of vascular endothelial growth factor receptor (VEGFR)-1 and -2 in the development of obliterative airway disease (OAD), an experimental model for OB. The nonimmunosuppressed recipients underwent transplantation with fully major histocompatibility complex mismatched heterotopic tracheal allografts and received VEGFR-1 and -2-specific monoclonal antibodies either alone or in combination or rat IgG as a control. The treatment with VEGFR-1- or -2-blocking antibody significantly decreased intragraft mRNA expression of natural killer cell activation markers early after transplantation. This was followed by reduced infiltration of CD11b⁺ cells and CD4⁺ T cells as well as down-regulated mRNA expression of proinflammatory chemokines and profibrotic growth factors. However, blocking of both VEGFR-1 and -2 was necessary to reduce luminal occlusion. Furthermore, concomitant inhibition of the calcineurin activation pathway almost totally abolished the development of OAD. This study proposes that blocking of VEGF receptors blunted natural killer cell and innate immune responses early after transplantation and attenuated the development of OAD. The results of this study suggest that further studies on the role of VEGFR-1 and -2 blocking in development of obliterative airway lesions might be rewarding.

Sinomenine in Cardio-Cerebrovascular Diseases: Potential Therapeutic Effects and Pharmacological Evidences

Cardio-cerebrovascular diseases, as a major cause of health loss all over the world, contribute to an important part of the global burden of disease. A large number of traditional Chinese medicines have been proved effective both clinically and in pharmacological investigations, with the acceleration of the modernization of Chinese medicine. Sinomenine is the main active constituent of sinomenium acutum and has been generally used in therapies of rheumatoid arthritis and neuralgia. Varieties of pharmacological effects of sinomenine in cardio-cerebrovascular system have been discovered recently, suggesting an inspiring application prospect of sinomenine in cardio-cerebrovascular diseases. Sinomenine may retard the progression of atherosclerosis by attenuating endothelial inflammation, regulating immune cells function, and inhibiting the proliferation of vascular smooth muscle cells. Sinomenine also alleviates chronic cardiac allograft rejection relying on its anti-inflammatory and anti-hyperplastic activities and suppresses autoimmune myocarditis by immunosuppression. Prevention of myocardial or cerebral ischemia-reperfusion injury by sinomenine is associated with its modulation of cardiomyocyte death, inflammation, calcium overload, and oxidative stress. The regulatory effects on vasodilation and electrophysiology make sinomenine a promising drug to treat hypertension and arrhythmia. Here, in this review, we will illustrate the pharmacological activities of sinomenine in cardio-cerebrovascular system and elaborate the underlying mechanisms, as well as give an overview of the potential therapeutic roles of sinomenine in cardio-cerebrovascular diseases, trying to provide clues and bases for its clinical usage.

Amniotic fluid stem cell-derived vesicles protect from VEGF-induced endothelial damage

Injection of amniotic fluid stem cells (AFSC) delays the course of progression of renal fibrosis in animals with Alport Syndrome, enhancing kidney function and improving survival. The mechanisms responsible for these protective outcomes are still largely unknown. Here, we showed that vascular endothelial growth factor (VEGF) signaling within the glomeruli of Alport mice is strongly elevated early on in the disease, causing glomerular endothelial cell damage. Intraventricular injected AFSC that homed within the glomeruli showed strong modulation of the VEGF activity, particularly in glomerular endothelial cells. To investigate this phenomenon we hypothesized that extracellular vesicles (EVs) produced by the AFSC could be responsible for the observed renoprotection. AFSC derived EVs presented exosomal and stem cell markers on their surface membrane, including VEGFR1 and VEGFR2. EVs were able to modulate VEGF in glomerular endothelial cells by effectively trapping the excess VEGF through VEGFR1-binding preventing cellular damage. In contrast, VEGFR1/sVEGFR1 knockout EVs failed to show similar protection, thus indicating that VEGF trapping is a potentially viable mechanism for AFSC-EV mediated renoprotection. Taken together, our findings establish that EVs secreted by AFSC could target a specific signaling pathway within the glomerulus, thus representing a new potential glomerulus-specific targeted intervention.

Vascular Endothelial Growth Factor Gene Polymorphism Is Associated With Long-term Kidney Allograft Outcomes

Introduction

Vascular endothelial growth factor (VEGF) regulates vasculogenesis in physiological and pathological states. We evaluated the role of VEGF single-nucleotide polymorphisms (SNPs) −1154 G/A, −2578 C/A, +936 C/T, and −2549 Ins/Del in chronic allograft nephropathy.

Methods

Blood samples were collected before renal transplantation, and DNA was extracted. Genotyping of VEGF SNPs −1154 G/A (rs1570360), −2578 C/A (rs699947), +936 C/T (rs112005313), and −2549 Ins/Del (18bpindel) polymorphisms were carried out. Relative quantification of VEGF-A mRNA expression for 4 VEGF SNPs were quantified by the 2^−ΔΔCt algorithm. Kidney allografts were categorized into graft loss (n = 98) and normally functioning (n = 174) groups. Genotype frequencies were calculated using additive, dominant, and recessive models. Hardy−Weinberg Equilibrium was assessed between outcome groups by standard procedure using χ² analysis. The cumulative allograft survival was estimated by Kaplan−Meier analysis and compared among VEGF genotypes by the log-rank test. Study limitations were the lack of VEGF serum levels, donor-specific antigens, and protocol biopsies.

Results

There was an association of AA (hazard ratio = 2.42, P = 0.0001) and CA (hazard ratio = 1.83, P = 0.009) genotypes of −2578 C/A SNP with graft loss. After adjustment for transplant-related covariates, associations of VEGF SNPs −2578 C/A and −2549 Ins/Del with graft failure were found to be significant. There was prolonged graft survival for cases with the CC genotype of VEGF −2578 C/A SNP. The carrier −2578*CC, −1154*GG, and +936*CC genotypes were shown to have a strongly protective association. There was no association with posttransplantation lymphomas.

Conclusion

Recipients of kidney allografts possessing low-producing VEGF genotypes are associated with less prolonged graft survival.

Impact of vascular endothelial growth factor single nucleotide polymorphism association on acute renal allograft rejection

BACKGROUND

Vascular endothelial growth factor (VEGF) is a cytokine which plays an important role in the division, proliferation and migration of endothelial cells. In the kidney, VEGF expression is found in glomerular podocytes and in tubular epithelial cells, which may result in acute inflammatory reactions.

METHODS

The role of VEGF gene polymorphisms (-2578 C/A, -2549 18 bp Ins/Del, -1154 G/A and +936 C/T) was investigated in 272 patients who underwent renal transplantation. ARMS-PCR and PCR-RFLP were used. Patients were categorized into acute allograft rejection (n = 76) and nonrejection (n = 196).

RESULTS

The VEGF -1154 GG genotype and the +936 T allele were found to be susceptible to acute rejection (AR). T-A-A-I, T-A-A-D, T-G-C-I and C-A-A-I haplotypes revealed a predisposition among AR cases. In silico analysis revealed +936 T as a significant allele involved in the transcription regulation.

CONCLUSION

These results highlight the role of VEGF polymorphisms in acute allograft rejection.

Expression of vascular endothelial growth factor and basic fibroblast growth factor in acute rejection reaction following rat orthotopic liver transplantation

The aim of the present study was to investigate the expression levels of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in acute rejection reaction (ARR) following orthotopic liver transplantation in a rat model. Serum VEGF and bFGF levels were detected using ELISA, and their expression levels in liver and spleen tissues were determined using immunohistochemistry. The mRNA expression levels of VEGF and bFGF were detected by conducting a quantitative polymerase chain reaction during the ARR following orthotopic liver transplantation. The expression levels of VEGF and bFGF in the serum 3 days following liver transplantation were significantly higher compared with those in the other groups (1 and 7 days following transplantation; P<0.01). In addition, the numbers of cells in the liver tissue that were shown to be positive for the expression VEGF and bFGF using immunohistochemistry were significantly higher 3 days following transplantation than at the other time points (P<0.0001). Furthermore, the numbers of cells positive for VEGF and bFGF expression in the spleen detected 3 days following the transplantation surgery were also significantly higher compared with those at the other time points (P<0.01). VEGF and bFGF mRNA expression levels were also increased from 1 day following the surgery and reached a peak at day 3, prior to declining gradually and remaining at a relatively high level. VEGF and bFGF mRNA expression levels changed dynamically, by peaking and then declining, in ARR following orthotopic liver transplantation. These changes may have an important impact on angiogenesis and the inflammatory reaction, and the identification of these changes increases the current understanding of ARR following orthotopic liver transplantation.

VEGF-C, VEGF-A and related angiogenesis factors as biomarkers of allograft vasculopathy in cardiac transplant recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV), the major cause of late allograft loss after cardiac transplantation, results from donor-directed cellular and humoral alloimmune responses. Graft vascular endothelial cells (EC) are primary targets of these destructive responses, suggesting that factors associated with endothelial injury and repair could serve as biomarkers of CAV.

METHODS

Using a protein profiler array platform, we measured the levels of 55 angiogenesis-related proteins in sera from 33 adult heart transplant recipients, including 17 with angiographically documented CAV and 16 age- and gender-matched controls without CAV. All patients were >2 years after heart transplant.

RESULTS

The study population was 75% male with a mean age of 62 ± 11 years. On average, patients were 12 ± 5 years after heart transplantation. We found that vascular endothelial growth factor (VEGF)-C, VEGF-A, angiopoietin-2, artemin, urokinase-type plasminogen activator and vasohibin were strongly associated with established CAV (all p < 0.01). Multivariable modeling identified VEGF-C, VEGF-A and platelet factor-4 (PF-4) as significant independent biomarkers of CAV. Furthermore, receiver-operating characteristic curve analysis demonstrated that the combination of all 3 molecules provided outstanding performance for the diagnosis of CAV (area under the curve [AUC] = 0.98; p < 0.001).

CONCLUSIONS

Serum levels of VEGF-C, VEGF-A and PF-4 demonstrate strong associations with established CAV and, together with related angiogenesis factors, may serve as a reliable, non-invasive diagnostic test for CAV in cardiac transplant recipients.

Targeting the intragraft microenvironment and the development of chronic allograft rejection

In this review, we discuss a paradigm whereby changes in the intragraft microenvironment promote or sustain the development of chronic allograft rejection. A key feature of this model involves the microvasculature including (a) endothelial cell (EC) destruction, and (b) EC proliferation, both of which result from alloimmune leukocyte- and/or alloantibody-induced responses. These changes in the microvasculature likely create abnormal blood flow patterns and thus promote local tissue hypoxia. Another feature of the chronic rejection microenvironment involves the overexpression of vascular endothelial growth factor (VEGF). VEGF stimulates EC activation and proliferation and it has potential to sustain inflammation via direct interactions with leukocytes. In this manner, VEGF may promote ongoing tissue injury. Finally, we review how these events can be targeted therapeutically using mTOR inhibitors. EC activation and proliferation as well as VEGF-VEGFR interactions require PI-3K/Akt/mTOR intracellular signaling. Thus, agents that inhibit this signaling pathway within the graft may also target the progression of chronic rejection and thus promote long-term graft survival.

Key Features of the Intragraft Microenvironment that Determine Long-Term Survival Following Transplantation

In this review, we discuss how changes in the intragraft microenvironment serve to promote or sustain the development of chronic allograft rejection. We propose two key elements within the microenvironment that contribute to the rejection process. The first is endothelial cell proliferation and angiogenesis that serve to create abnormal microvascular blood flow patterns as well as local tissue hypoxia, and precedes endothelial-to-mesenchymal transition. The second is the overexpression of local cytokines and growth factors that serve to sustain inflammation and, in turn, function to promote a leukocyte-induced angiogenesis reaction. Central to both events is overexpression of vascular endothelial growth factor (VEGF), which is both pro-inflammatory and pro-angiogenic, and thus drives progression of the chronic rejection microenvironment. In our discussion, we focus on how inflammation results in angiogenesis and how leukocyte-induced angiogenesis is pathological. We also discuss how VEGF is a master control factor that fosters the development of the chronic rejection microenvironment. Overall, this review provides insight into the intragraft microenvironment as an important paradigm for future direction in the field.

Thalidomide attenuates graft arteriosclerosis of aortic transplant in a rat model

OBJECTIVE

The purpose of the current study was to evaluate the effects of thalidomide on graft arteriosclerosis.

MATERIALS AND METHODS

Male Lewis rats received abdominal aorta grafts from male Brown-Norway rats. The animals were divided into 4 groups: no treatment controls, a low-dose group that received thalidomide (50 mg/kg per day), a middle dose group that received thalidomide (100 mg/kg per day), and a high-dose group that received thalidomide (200 mg/kg per day) by daily intragastric administration. Rats were humanely killed at 60 days after surgery. The grafted aortas were analyzed by histology, immunohistochemistry, and Western blot analysis. The serum was analyzed by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The neointimal thickness of the thalidomide treated aortas was significantly thinner compared with that of no treatment aortas (P < .05). Vascular endothelial growth factor (VEGF), platelet-derived growth factor, and intracellular adhesian molecule (ICAM-1) protein expression in the treatment group were significantly lower than those in the control group (P < .05). Moreover, thalidomide significantly inhibited the production of VEGF and ICAM-1 in serum (P < .05).

CONCLUSION

Our data suggested that thalidomide can attenuate graft arteriosclerosis so as to protect aortic grafts.

Roles of vascular endothelial growth factor in acute rejection reaction following liver transplantation

The presently known cytokines that participate in acute rejection of organ transplantation include four categories by order of function: inflammatory cytokines, immunospecific cytokines, inflammatory cell activating cytokines and growth cytokines. Of them, growth cytokines that directly induce division, proliferation and migration of endothelial cells mainly include the vascular endothelial growth factor (VEGF) family and the fibroblast growth factor (FGF) family [1]. Recent studies [2] showed that interactions and time overlap of inflammatory cell infiltration and angiogenesis are the main mechanisms that induce acute rejection (AR) following organ transplantation, which has been demonstrated by the clinical fact that AR symptoms after liver transplantation could only be relieved by combination use of drugs for improving micro vessels and those for improving micro bile ducts. This article is a review of VEGF that mediates inflammatory cell infiltration and angiogenesis in the portal area [3].

Sirolimus-based regimen is associated with decreased expression of glomerular vascular endothelial growth factor

BACKGROUND

Sirolimus (SRL) is a potent immunosuppressant used in organ transplantation. It is known to decrease vascular endothelial growth factor (VEGF) synthesis, making it an interesting treatment option for transplant patients who develop Kaposi sarcoma or other malignant diseases. Because VEGF plays a key role in glomerular function and vascular remodelling, we determined the effect of SRL on renal VEGF expression.

METHODS

Using immunohistochemistry and quantitative image analysis, we examined renal VEGF expression in routine kidney biopsies performed at 1 year post-transplant in the CONCEPT study, a prospective randomized study comparing a cyclosporine (CsA)-based regimen to a SRL-based regimen in association with mycophenolate mofetil (MMF).

RESULTS

A total of 74 patients were included in this substudy; 35 were randomized to the CsA group and 39 to the SRL group. Using continuous variables, the mean percentage of glomerular VEGF expression at Week 52 was significantly lower in the SRL group (14.7 ± 13%) compared to CsA group (21.2 ± 14%: P = 0.02). The percentage of glomerular VEGF expression at Week 52 was not influenced by recipient or donor age, gender, renal function, CsA dose, CsA blood level, SRL dose or SRL blood level. It was significantly lower in patients with a proteinuria over versus below 0.5 g/day (11.58 ± 7.9 versus 19.45 ± 15.53; P = 0.036).

CONCLUSIONS

There is emerging evidence that the VEGF system can play either a beneficial or a detrimental role depending on the specific pathologic situations. Therefore, modulating the renal VEGF axis by using an SRL-based regimen may influence the evolution of kidney injury associated with renal transplantation.

Effect of vascular endothelial growth factor and its receptor KDR on the transendothelial migration and local trafficking of human T cells in vitro and in vivo

In these studies, we find that the vascular endothelial growth factor (VEGF) receptor KDR is expressed on subsets of mitogen-activated CD4(+) and CD8(+) T cells in vitro. We also found that KDR colocalizes with CD3 on mitogen-activated T cells in vitro and on infiltrates within rejecting human allografts in vivo. To evaluate whether VEGF and KDR mediate lymphocyte migration across endothelial cells (ECs), we used an in vitro live-time transmigration model and observed that both anti-VEGF and anti-KDR antibodies inhibit the transmigration of both CD4(+) and CD8(+) T cells across tumor necrosis factor α (TNFα)-activated, but not unactivated ECs. In addition, we found that interactions among CD4(+) or CD8(+) T cells and TNFα-activated ECs result in the induction of KDR on each T cell subset, and that KDR-expressing lymphocytes preferentially transmigrate across TNFα-activated ECs. Finally, using a humanized severe combined immunodeficient mouse model of lymphocyte trafficking, we found that KDR-expressing lymphocytes migrate into human skin in vivo, and that migration is reduced in mice treated with a blocking anti-VEGF antibody. These observations demonstrate that induced expression of KDR on subsets of T cells, and locally expressed VEGF, facilitate EC-dependent lymphocyte chemotaxis, and thus, the localization of T cells at sites of inflammation.

WITHDRAWN: Endothelium in the allograft

The paper entitled "Endothelium in the allograft" by Bryan N Becker et al, which was published online on 9 September 2009, has been withdrawn at the authors' request. Kidney International advance online publication, 9 September 2009; doi:10.1038/ki.2009.333.

Improved renal function after kidney transplantation is associated with heme oxygenase-1 polymorphism

Heme oxygenase-1 (HO-1) has a microsatellite polymorphism based on the number of guanosine-thymidine nucleotide repeats (GT) repeats that regulates expression levels and could have an impact on organ survival post-injury. We correlated HO-1 polymorphism with renal graft function. The HO-1 gene was sequenced (N = 181), and the allelic repeats were divided into subclasses: short repeats (S) (<27 repeats) and long repeats (L) (>/=27 repeats). A total of 47.5% of the donors carried the S allele. The allograft function was statistically improved six months, two and three yr after transplantation in patients receiving kidneys from donors with an S allele. For the recipients carrying the S allele (50.3%), the allograft function was also better throughout the follow-up, but reached statistical significance only three yr after transplantation (p = 0.04). Considering only those patients who had chronic allograft nephropathy (CAN; 74 of 181), allograft function was also better in donors and in recipients carrying the S allele, two and three yr after transplantation (p = 0.03). Recipients of kidney transplantation from donors carrying the S allele presented better function even in the presence of CAN.

Renal protective effects of leukotriene receptor blockers in an experimental model of cyclosporine nephrotoxicity

BACKGROUND

Chronic cyclosporine (CsA) nephrotoxicity is associated with renal fibrosis and hyaline arteriolopathy. Fibrogenic cytokines, such as transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF), play a pivotal role in CsA nephrotoxicity. Previous studies have demonstrated the possible role of leukotrienes (LT) in chronic CsA nephrotoxicity. The aim of this study was to examine the possible beneficial effects of LT blockers in attenuating the morphological and histochemical effects induced by CsA in a rat model of CsA nephrotoxicity.

MATERIALS AND METHODS

Twenty-four male Wistar rats were divided into 3 groups (n = 8). The first group (G1) was treated with vehicle intraperitoneally (IP) for 60 days. The second group (G2) was treated with 15 mg/kg CsA IP for 60 days. The third group (G3) was treated with the same dose of CsA plus 4 mg/kg montelukast administered by oral gavage for 60 days.

RESULTS

There was a statistically significant decrease in glomerular filtration rate (GFR) among G2 compared with G1 animals: 0.41 +/- 0.03 vs 1.63 +/- 0.12 mL/min (P < .001), or G3 hosts: 0.41 +/- 0.03 vs 0.95 +/- 0.05 mL/min (P < .005), respectively. The percentage of hyaline arteriolopathic changes was higher in G2 than G1 or G3: 81.66% +/- 8.2% vs 11.83% +/- 0.87% (P < .01) or 37.0% +/- 8.8% (P < .01), respectively. Fibrosis score was higher in G2 compared with G1 or G3: 1.5 +/- 0.04 vs 0.16 +/- 0.02 (P < .001) and 1.0 +/- 0.05 (P < .05), respectively. TGF-beta and VEGF immunoexpression were significantly increased in G2 compared with G1 (P < .05) or G3 (P < .05).

CONCLUSIONS

Our study suggested that LT may play a critical role in the pathogenesis of chronic CsA nephrotoxicity; the administration of montelukast, a LT receptor blocker, may prevent CsA-induced nephrotoxicity.

Vascular endothelial growth factor in chronic rat allograft nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) is a complex process of alloimmune responses and chronic inflammation leading to fibrosis and vasculopathy. We examined the biological role of proinflammatory vascular endothelial growth factor (VEGF) in a rat renal transplantation model of CAN.

METHODS

Syngraft and allograft recipients were treated with a suboptimal dose of cyclosporine A which allows acute rejection and CAN to develop. Intragraft VEGF, VEGFR-1 and VEGFR-2 expressions were determined at 5, 14, 30 and 60 days. Protein tyrosine kinase inhibitor PTK787 was used to inhibit VEGFR activity.

RESULTS

In nontransplanted kidneys and syngrafts, mild VEGF expression was observed in the glomeruli and tubuli. VEGFR-1 was detected in vascular structures and VEGFR-2 in glomeruli as well. In allografts, total intragraft VEGF expression and interstitial inflammatory cell VEGF expression were induced and correlated with the chronic allograft damage index (CADI) score. Total intragraft and interstitial inflammatory cell VEGFR-1 expression was induced and interstitial cell VEGFR-1 expression correlated with the CADI score. Blocking VEGF receptor signaling with PTK787 significantly reduced fibrosis and the CADI score, but did not affect early inflammation or VEGF, VEGFR-1, VEGFR-2 expressions compared to vehicle treated group.

CONCLUSIONS

Interstitial inflammatory cell VEGF and VEGFR-1 expressions are induced during the development of CAN. Increased VEGF activity may enhance the alloimmune induced inflammatory responses leading to fibrosis and CAN.

Peritubular capillary rarefaction and lymphangiogenesis in chronic allograft failure

BACKGROUND

Chronic renal allograft failure is a common and multifactorial but incompletely understood process with no effective treatment strategy.

METHODS

We used immunohistochemistry to evaluate changes in density and turnover (proliferation) of the microvasculature and lymphatic vessels in endstage human transplant nephrectomies and control tissue derived from macroscopically normal areas of native nephrectomy specimens removed for renal carcinoma. We also examined the expression of angiogenic and lymphangiogenic growth factors in the associated inflammatory infiltrate.

RESULTS

Endstage allografts showed reduced microvascular density in cortex and medulla compared with controls (P<0.0001), despite the presence of endothelial cell proliferation. However, the grafts also showed new lymphatic vessels in the tubulointerstitium, not evident in controls, and which appeared to be functional with luminal macrophages. Double labeling studies showed a subpopulation of the graft-infiltrating macrophages to be immunopositive for inducible nitric oxide synthase or vascular endothelial growth factor-C (a lymphatic-specific growth factor). B cells also strongly expressed the inflammatory and angiogenic cytokine vascular endothelial growth factor A.

CONCLUSIONS

The present results identify contrasting changes in the microanatomy of vascular and lymphatic beds in endstage renal allografts associated with subpopulations of infiltrating macrophages and B cells that potentially regulate some of these changes. These cells and processes could become a new therapeutic target in chronic allograft failure.

Chronic allograft nephropathy in paediatric renal transplantation

Chronic allograft nephropathy (CAN) is now the leading cause of renal transplant loss in paediatric transplant recipients. Despite improvements in immunosuppression, which have significantly reduced the incidence of acute rejection, the rates of chronic kidney loss have remained unchanged in paediatric transplant patients over the last 20 years. Chronic allograft nephropathy is a pathological diagnosis of which the key features are tubular atrophy and interstitial fibrosis. More consistent definitions and grading of these through the Banff classification have allowed more rigorous study of the development of chronic allograft nephropathy along with further identification of specific lesions associated with the underlying aetiologies. While initially thought to be primarily due to immune injury, it is now evident that CAN is the end result of a variety of immune and non-immune injuries including ischaemia reperfusion injury, calcineurin inhibitor (CNI) toxicity and infections. Protocol biopsy studies have demonstrated rates of CAN development in children similar to those in adults with comparable underlying pathological processes. This review outlines the current knowledge of CAN within the context of paediatric renal transplantation.

Expression of fractalkine, CX3CR1, and vascular endothelial growth factor in human chronic renal allograft rejection

AIM

Fractalkine/CX3CR1 system may contribute to the pathogenesis of renal allograft chronic rejection (CR). Vascular endothelial growth factor (VEGF) is an endothelial mitogen, which shows increased expression in inflammation and vasculopathy. This study sought describe the expression and distribution of Fractalkine/CX3CR1 and VEGF, and their relationship to human renal allograft CR.

METHODS

Renal tissue from 10 patients with CR was examined for Fractalkine/CX3CR1 and VEGF protein by immunohistochemistry for comparison with patients displaying hyperacute rejection (n = 10), acute rejection (n = 10), and normal kidneys (n = 10). All patients were selected based upon histologically proven diagnoses between 1992 and 2003.

RESULTS

Immunohistochemistry revealed that Fractalkine/CX3CR1 were mostly expressed in the tubulointerstitium and tubular epithelial cell basolateral membrane. Some vessels showed positive staining for Fractalkine/CX3CR1 as well as occasionally glomerular parietal wall cells. Among the CR group, VEGF was mostly expressed in tubular epithelium and the tubulointerstitium. A proportion of glomeruli and vessels had positive staining for VEGF, which was up-regulated most strikingly in the interstitial compartment in CR. There was markedly increased expression of Fractalkine/CX3CR1 and VEGF protein in the interstitium of the CR compared with other groups (P < .05). VEGF colocalized with the expression of Fractalkine/CX3CR1.

CONCLUSION

Fractalkine/CX3CR1 and VEGF may play an important role in the development of interstitial fibrosis via mononuclear cell-induced cytokine production and myofibroblast stimulation in CR. Further studies are necessary to identify the role in the pathogenesis of CR.

Vascular Endothelial Growth Factor (VEGF) Ligand and Receptor Induction in Rat Renal Allograft Rejection

BACKGROUND

Acute rejection is the single most important risk factor for the subsequent development of chronic allograft nephropathy (CAN), which is still the primary reason for late allograft loss in kidney transplantation. Vascular endothelial growth factor (VEGF) is a proangiogenic factor that has an important role in the development and maintenance of physiological endothelium. While its role has been characterized in the pathology of diabetic nephropathy and preeclampsia, its role in the development of acute and chronic allograft rejection remains unclear.

METHODS

Kidney transplantations were performed from DA to WF rats and syngeneic control transplantations were performed between DA rats. Normal kidneys were used as controls to evaluate physiological VEGF and VEGFR-1 expression. Allografted rats were immunosuppressed with cyclosporine (CsA) (1.5 mg/kg/d subcutaneously); and no immunosuppression was given to syngeneic grafts. Grafts were harvested at 5 and 90 days after transplantation for histology and immunohistochemistry (VEGF, VEGFR-1).

RESULTS

In normal kidneys VEGF ligand and receptor expression was almost nonexistent. Only mild glomerular, arterial, and tubular VEGF expression was seen. In syngeneic grafts, no histological signs of acute or chronic rejection were seen, whereas characteristics of both acute and chronic rejection were seen in CsA-treated allografts. Altough VEGF expression was increased in syngenic grafts when compared to controls it still remained mild in both the early and the late posttransplant period. In CsA-treated allografts moderate VEGF expression was seen already 5 days after transplantation; the expression increased at 90 days after transplantation. The same pattern was also discovered for VEGFR-1 expression although the difference was not as remarkable after 5 days.

CONCLUSIONS

Our results demonstrated that VEGF ligand and receptor expression was increased in both acute and chronic rejection. Our data suggested that VEGF may have an important role in the pathology of chronic rejection. Based on our findings VEGF inhibition could be a potential intervention to prevent CAN in clinical kidney transplantation.

IL-1beta induces VEGF, independently of PGE2 induction, mainly through the PI3-K/mTOR pathway in renal mesangial cells

Vascular endothelial growth factor (VEGF) could play a relevant role in angiogenesis associated with chronic allograft nephropathy. Interleukin-1beta (IL-1beta) has a key role in inflammatory response. It induces prostaglandin (PG) E2, which is involved in VEGF release by some normal and tumor cells. In the present work, we studied the effect of IL-1beta on VEGF release by rat mesangial cells, the transduction signal, and whether or not PGE2 is involved in this effect. IL-1beta induced a time-dependent formation of VEGF (analyzed by enzyme-linked immunosorbent assay) and PGE2 (analyzed by enzyme immunoassay). The latter correlated with microsomal-PGE-synthase (mPGES)-1 expression rather than with cyclooxygenase (COX)-2 in terms of protein, determined by Western blotting. No effect of IL-1beta on COX-1, cytosolic PGES, or mPGES-2 expression was observed. Indomethacin exerted a nonsignificant effect on IL-1beta-induced VEGF, and exogenously added PGE2 exhibited a nonsignificant stimulatory effect on VEGF formation. SB 203580, a p38 mitogen-activated protein kinase inhibitor, weakly inhibited the induction of VEGF by IL-1beta in a concentration-dependent manner, whereas LY 294002, a phosphoinoside 3-kinase (PI3-K) inhibitor, and rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, strongly inhibited both IL-1beta- and tumor necrosis factor-alpha-induced VEGF formation in a concentration-dependent manner. Rapamycin also decreased glomerular VEGF levels in the anti-Thy1.1 model of experimental glomerulonephritis. In conclusion, the PI3-K-mTOR pathway seems to be essential in cytokine-induced release of VEGF in mesangial cells.

The pathobiology of polyomavirus infection in man

This article traces the discovery of polyomaviruses and outlines investigations, which shed light on potential modes of transmission of this increasingly important group of human pathogens. The pathobiology of the virus is summarized with particular reference to interactions with host cell receptors, cell entry, cytoplasmic trafficking, and targeting of the viral genome to the nucleus. This is followed by a discussion of sites of viral latency and factors leading to viral reactivation. Finally, we present biochemical mechanisms that could potentially explain several key elements of tissue pathology characteristic of BKV mediated damage to human kidney.

Expression of vascular endothelial growth factor in chronic alcoholic liver fibrosis in rats

AIM: To investigate the expression of vascular endothelial growth factor (VEGF) and its role in the pathogenesis and development of chronic alcoholic liver fibrosis in rats.

METHODS: Liver fibrosis models were established in 24 SD rats by intragastric administration (7 g/kg) of alcohol (56º, 560 mL/L) every morning, and 10 normal rats served as controls. The rats in model group were killed by exsanguination from femoral vein at 4, 12 and 24 wk. Pathological changes of liver tissues in rats were identified by Masson staining, and the expression of VEGF mRNA was detected by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: VEGF mRNA expression was not detected in the control rats. The expression of VEGF mRNA in model rats was the highest at 4 wk, reaching 83.3% (5/6), which was significantly higher than that in the controls (P < 0.01). The positive rate of VEGF mRNA expression dropped to 18.2% (2/11) at 12 wk, and then rose up again to 57.1% (4/7) at 24 wk, which was markedly higher than that in the controls. The expression of VEGF mRNA was also notably different between 4 and 12 wk (P < 0.01), but not between 4 and 24 wk (P > 0.05). Fatty and vacuole-like degeneration, necrosis and production of collagen were observed in the model rats.

CONCLUSION: VEGF plays an important role in the pathogenesis and development of chronic alcoholic liver fibrosis.

Predictors of chronic allograft nephropathy from protocol biopsies using histological and immunohistochemical techniques

AIM

Chronic allograft nephropathy is a predictor of poor allograft survival. Protocol and diagnostic biopsies were used to identify markers contributing to its pathogenesis.

METHODS

Diagnostic, 3- and 12-month protocol biopsies in renal transplant recipients were examined. Immunohistochemical staining with monoclonal antibodies for memory T cells (CD45RO), macrophages (CD68) and alpha smooth muscle actin was undertaken on protocol biopsies.

RESULTS

Protocol biopsies revealed the incidence of chronic allograft nephropathy to be 10.7% (3/28) at 3 and 57.6% (19/33) at 12 months. There was a trend towards a higher serum creatinine in patients with chronic allograft nephropathy compared with those without (0.15 +/- 0.04 vs 0.12 +/- 0.04 mmol/L, P = 0.047). The strongest predictor of chronic allograft nephropathy at 12 months was the presence of arteriolar hyaline change (P = 0.035; odds ratio 1.22, 95% CI 0.036-0.887) whereas a higher CD45RO and CD68 count at 12 months was associated with chronic allograft nephropathy (74.7 +/- 56.9 cells/mm(2) and 22.4 +/- 23.5 cells/mm(2)) compared with patients without it (29.2 +/- 29.2 cells/mm(2) and 8.3 +/- 9.9 cells/mm(2), P = 0.006 and P = 0.03, respectively). The number of smooth muscle actin positive cells correlated significantly with chronic allograft nephropathy at 12 month (107.6 +/- 44 vs 73.9 +/- 20.8 cells/mm(2), P = 0.009).

CONCLUSION

The high prevalence of chronic allograft nephropathy in renal transplant recipients is associated with renal dysfunction. Arteriolar hyalinosis was the most significant predictor at 12 months. There was a significantly higher macrophage and T cell infiltrate in stable grafts undergoing chronic allograft nephropathy at 12 months post transplant.

Chronic allograft nephropathy: current concepts and future directions

The paradigm that chronic rejection causes all progressive late allograft failure has been replaced by a hypothesis of cumulative damage, where a series of time-dependent immune and nonimmune mechanisms injure the kidney and lead to chronic interstitial fibrosis and tubular atrophy, representing a final common pathway of injury and its consequent fibrotic healing response. Allograft damage is common, progressive, time-dependent, clinically important and modified by immunosuppression. Early after transplantation, tubulointerstitial damage is predominantly related to ischemia reperfusion injury, acute tubular necrosis, acute and subclinical rejection and/or calcineurin inhibitor nephrotoxicity, superimposed on preexisting donor disease. Later, cellular inflammation lessens and is replaced by microvascular and glomerular injury from calcineurin inhibitor nephrotoxicity, hypertension, immune-mediated fibrointimal vascular hyperplasia, transplant glomerulopathy and capillary injury, polyoma virus and/or recurrent glomerulonephritis. Additional mechanisms of injury include internal architectural disruption of the kidney, cortical ischemia, persistent chronic inflammation, replicative senescence, cytokine excess and fibrosis induced by epithelial-to-mesenchymal transition. Current understanding of the etiology, pathophysiology and evolution of pathological changes are detailed. An approach to histological assessment of the individual failing graft are presented and a series of postulates are defined for future studies of chronic allograft nephropathy.

Differential Expression of Profibrotic and Growth Factors in Chronic Allograft Nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) is a multifactorial process, where both immunological and nonimmunological factors play roles. Microarrays detect thousands of genes simultaneously.

METHODS

We have analyzed gene expression profiles of 16 kidney transplant biopsy samples with CAN by high-density oligonucleotide microarrays, comparing to six normal transplant biopsies. Eight CAN biopsies showed nodular arteriolar hyalinization and one was positive for C4d staining.

RESULTS

Hierarchical clustering analysis of the 22 biopsies revealed differential gene expression patterns in CAN versus the control biopsies. However, microarray analysis did not reveal differential gene expression patterns in patients with or without arteriolar hyalinization. Fifty percent of the 100 genes with highest hybridization intensities in a C4d positive sample were related to cellular and humoral immune response. Although 212 genes were upregulated a minimum of 1.5-fold, 112 genes were downregulated in CAN samples. There was differential expression of profibrotic and growth factors that while transforming growth factor-beta induced factor, thrombospondin 1, and platelet derived growth factor-C were up-regulated, vascular endothelial growth factor, epidermal growth factor, and fibroblast growth factors 1 and 9 were downregulated. Selected differentially expressed genes were confirmed in microdissected samples by real-time quantitative PCR. Immunopathologic examination of biopsies revealed strong TGF-beta but decreased glomerular VEGF expression in CAN.

CONCLUSION

Microarrays might be an important tool to uncover the mechanisms of multifactorial diseases, such as CAN.

Sirolimus-induced thrombotic microangiopathy is associated with decreased expression of vascular endothelial growth factor in kidneys

The aim of this study was to examine the clinical characteristics, the histological features and the renal expression of vascular endothelial growth factor (VEGF) of five patients with sirolimus-associated thrombotic microangiopathy (TMA). Sirolimus-induced TMA occurs preferentially in kidneys with concomitant endothelial injury: it was observed in three patients with acute cellular rejection on calcineurin inhibitor-free regimen, in one patient with chronic graft rejection on a calcineurin inhibitor-free protocol and in one patient with chronic calcineurin inhibitor nephrotoxicity. We found that renal VEGF expression during sirolimus-induced TMA was significantly lower than VEGF expression in normal transplanted kidneys (p < 0.01). Decreased expression of VEGF seems to be a consequence of sirolimus treatment since (i) analysis of two biopsies performed after the switch of sirolimus to calcineurin inhibitor showed reappearance of VEGF expression, (ii) no decreased expression of VEGF was found in five kidneys with classical TMA and, (iii) an increased expression of VEGF was observed in seven kidneys with acute cellular rejection on a sirolimus-free immunosuppressive regimen (p < 0.01). The potential role of sirolimus-induced downregulation of VEGF as a predisposing factor to the development of TMA is discussed.

Function of the Vascular Endothelial Growth Factor Receptors Flt-1 and Flk-1/KDR in the Alloimmune Response In Vivo

BACKGROUND

We have recently reported that vascular endothelial growth factor (VEGF) functions as a proinflammatory cytokine to regulate the trafficking of leukocytes into allografts in the early posttransplant period. VEGF binds two major VEGF receptors: VEGFR-1 (flt-1) and VEGFR-2 (flk-1/KDR). Here, we wished to investigate the expression and function of VEGF receptors in the process of acute allograft rejection in vivo.

METHODS

We performed fully MHC-mismatched C57BL/6 (H-2b) into BALB/c (H-2d) vascularized heterotopic murine cardiac transplants and we examined the expression of VEGF and VEGF receptors by immunohistochemistry during acute allograft rejection. Next, we treated mice with specific neutralizing monoclonal antibodies against murine VEGFR-1 and VEGFR-2 and examined their effect on the development of acute allograft rejection by histology and by analysis of graft survival. The intragraft expression of cytokines and chemokines were also evaluated by quantitative real-time PCR analysis.

RESULTS

The expression of VEGF, VEGFR-1 and VEGFR-2 were significantly up-regulated during allograft rejection as compared to isografts. Administration of either anti-VEGFR-1 or anti-VEGFR-2 alone failed to inhibit allograft rejection. However, coadministration of both antibodies together inhibited leukocyte infiltration of allografts and prolonged allograft survival. Furthermore, the effect of VEGFR blockade was associated with the downregulation of intragraft cytokine and chemokine expression.

CONCLUSIONS

Our data suggest that VEGF-VEGFR interactions function in the alloimmune response in vivo. Targeting VEGFRs may represent a novel therapy to protect allografts following clinical transplantation.

Vascular endothelial growth factor expression and cyclosporine toxicity in renal allograft rejection

The aim of this study was to evaluate the influence of vascular endothelial growth factor (VEGF) on renal function and on development of interstitial fibrosis (IF) in renal allografts. Tubular and interstitial expressions of VEGF and TNF-alpha, and density of macrophages in the interstitium were examined in 92 patients with nonrejected kidneys, acute rejection (AR), chronic allograft nephropathy (CAN), borderline changes (BC) and acute cyclosporin A (CsA) toxicity. Follow-up biopsy specimens from patients with AR and BC were evaluated for development of IF. A significant difference in tubular and interstitial VEGF expressions was found between patients with AR, BC, CAN and CsA toxicity (p < 0.001). Macrophage infiltration was positively correlated with VEGF and TNF-alpha expressions (p < 0.001). VEGF expression increased with increasing expression of TNF-alpha (p < 0.001). Renal function in first 6 months after initial biopsy was better in patients with marked tubular VEGF expression (p < 0.01); however, in follow-up, development of IF and graft loss was found earlier in these patients (p < 0.01 and p < 0.05, respectively). Increased renal VEGF expression has protective properties immediately following renal allograft but allows for increased risk of early IF, and therefore poor graft outcome in the long term.

Combined vascular endothelial growth factor and platelet-derived growth factor inhibition in rat cardiac allografts: beneficial effects on inflammation and smooth muscle cell proliferation

BACKGROUND

Perivascular inflammation and subsequent smooth muscle cell (SMC) proliferation are central in the development of cardiac allograft arteriosclerosis. We examined the effect of combined inhibition of proinflammatory vascular endothelial growth factor (VEGF) and SMC mitogen platelet-derived growth factor (PDGF) in rat cardiac allografts.

METHODS

Heterotopic cardiac transplantations were performed between fully major histocompatibility mismatched rat strains receiving cyclosporine A immunosuppression. In situ hybridization and immunohistochemistry were performed to examine VEGF and PDGF ligand and receptor (R) expression. Protein tyrosine kinase inhibitors PTK787 and imatinib were used to inhibit VEGFR and PDGFR activity, respectively. Rat coronary artery SMC migration and proliferation assays were used to examine the effect of VEGF and PDGF and tyrosine kinase inhibitors in vitro.

RESULTS

Both ligand and receptor expression of VEGF and PDGF were detected in chronically rejecting allografts. In vitro, PDGF-BB mediated rat coronary artery SMC migration and proliferation was completely inhibited with imatinib and partially with PTK787. In vivo, combined treatment with PTK787 and imatinib significantly reduced the formation of neointimal lesions in arteries of cardiac allografts at 8 weeks, producing a greater effect than either drug alone. PTK787, in contrast with imatinib, reduced the number of ED1 macrophages and PDGF-B immunoreactivity in the allografts at 4 weeks.

CONCLUSIONS

Blocking VEGF and PDGF receptor signaling in cardiac allografts has distinctive effects on inflammation and SMC proliferation, suggesting that targeting both inflammation and pathologic vascular remodeling may be needed to inhibit cardiac allograft arteriosclerosis.

The role of vascular endothelial growth factor (VEGF) in renal pathophysiology

Vascular endothelial growth factor (VEGF) is an endothelial-specific growth factor that promotes endothelial cell proliferation, differentiation and survival, mediates endothelium-dependent vasodilatation, induces microvascular hyperpermeability and participates in interstitial matrix remodeling. In the kidney, VEGF expression is most prominent in glomerular podocytes and in tubular epithelial cells, while VEGF receptors are mainly found on preglomerular, glomerular, and peritubular endothelial cells. The role of VEGF in normal renal physiology is essentially unknown. The absence of prominent effects of VEGF blockade in normal experimental animals suggests a limited function during homeostasis, although a role in the formation and maintenance of glomerular capillary endothelial fenestrations has been suggested. VEGF and its receptors are up-regulated in experimental animals and humans with type 1 and type 2 diabetes. Inhibition of VEGF has beneficial effects on diabetes-induced functional and structural alterations, suggesting a deleterious role for VEGF in the pathophysiology of diabetic nephropathy. VEGF is required for glomerular and tubular hypertrophy and proliferation in response to nephron reduction, and loss of VEGF is associated with the development of glomerulosclerosis and tubulointerstitial fibrosis in the remnant kidney. No firm conclusions on the role of VEGF in minimal change or membranous glomerulonephritis can be drawn. VEGF may be an essential mediator of glomerular recovery in proliferative glomerulonephritis. Glomerular and tubulointerstitial repair in thrombotic microangiopathy and cyclosporin nephrotoxicity may also be VEGF-dependent. In conclusion, VEGF is required for growth and proliferation of glomerular and peritubular endothelial cells. While deleterious in some, it may contribute to recovery in other forms of renal diseases.

The role of nitric oxide in renal transplantation

This review discusses the concept that nitric oxide synthase (NOS) may orchestrate both the inflammatory response to the renal allograft and anti-inflammatory defense in the graft itself. NO is produced by endothelial, epithelial, as well as inflammatory cells. In the setting of transplantation, the endothelium is the first lining to be subjected to the early response to injury. In turn, activated endothelial cells facilitate leukocyte recruitment, immune-mediated injury, and angiogenesis. On activation by inflammatory stimuli, endothelial cells up-regulate multiple vasoactive substances, oxygen radicals, cytokines, chemokines, and growth factors. Therefore, endothelial integrity, especially the expression of protecting vasoactive agents, such as NO, may be a key factor in resistance or sensitivity to transplantation-mediated injury. Thus, evaluating the mechanisms by which NO is involved in either protecting or injuring the transplanted allogeneic kidney is important for our understanding of renal allograft rejection. This review focuses on the role of NO in the inflammatory endothelial-leukocyte interactions, which are implicated in acute and chronic rejection of the transplanted kidney.

De novo kidney transplantation without use of calcineurin inhibitors preserves renal structure and function at two years

We performed a randomized prospective trial comparing calcineurin inhibitor (CNI)-free to CNI-based immunosuppression to determine the impact on renal function, structure and gene expression. Sixty-one kidney recipients treated with basiliximab mycophenolate mofetil (MMF) and prednisone (P) were randomly assigned to concentration-controlled sirolimus or cyclosporine. Two years post-transplant 55 patients underwent renal function studies, 48 (87%) underwent transplant biopsies; all classified by Banff scoring and 41 by DNA microarrays. Comparing sirolimus/MMF/P to cyclosporine/MMF/P there was a significantly lower serum creatinine (1.35 vs. 1.81 mg/dL; p = 0.008), higher Cockroft-Gault glomerular filtration rate (GFR) (80.4 vs. 63.4 mL/min; p = 0.008), iothalamate GFR (60.6 vs. 49.2 mL/min; p = 0.018) and Banff 0 (normal) biopsies (66.6 vs. 20.8%; p = 0.013). Regression analysis of calculated GFRs from 1 to 36 months yielded a positive slope for sirolimus of 3.36 mL/min/year, and a negative slope for cyclosporine of -1.58 mL/min/year (p = 0.008). Gene expression profiles from kidneys with higher Banff chronic allograft nephropathy (CAN) scores confirmed significant up-regulation of genes responsible for immune/inflammation and fibrosis/tissue remodeling. At 2 years the sirolimus-treated recipients have better renal function, a diminished prevalence of CAN and down-regulated expression of genes responsible for progression of CAN. All may provide for an alternative natural history with improved graft survival.

CD40-induced transcriptional activation of vascular endothelial growth factor involves a 68-bp region of the promoter containing a CpG island

Vascular endothelial growth factor (VEGF) is produced by several cell types in the kidney, and its expression is tightly regulated for the maintenance of normal renal physiology. Increases or decreases in its expression are associated with proteinuria and renal disease. Recently, we found that the expression of VEGF is markedly induced following interactions between CD40 ligand (CD40L) and CD40. Here, endothelial cells (EC) or Jurkat T cell lines were transiently transfected with luciferase reporter constructs under the control of the human VEGF promoter and were treated with human soluble CD40L (sCD40L). We identified a CD40-responsive 68-bp region (bp -50 to +18) of the promoter and 43 bp within this region (bp -25 to +18) that have 97% homology to a sequence of CpG dinucleotides. A computerized search revealed that the CpG region has putative binding domains for the transcriptional repressor protein methyl CpG binding protein-2 (MeCP2). In EMSA, we found that the 43-bp methylated sequence formed four complex(es) with nuclear extracts from untreated EC and reduced binding of at least one complex when nuclear lysates from sCD40L-activated EC (30 min) were used. Supershift analysis using anti-MeCP2 demonstrated that most of the complex(es) in both untreated and sCD40L-activated EC involved interactions between the 43-bp DNA and MeCP2. In addition, we found that other CpG binding proteins may also interact with this region of the promoter. Taken together, this is the first demonstration that CpG binding transcriptional repressor proteins including MeCP2 may be of importance in VEGF biology.

Proinflammatory functions of vascular endothelial growth factor in alloimmunity

Vascular endothelial growth factor (VEGF), an established angiogenesis factor, is expressed in allografts undergoing rejection, but its function in the rejection process has not been defined. Here, we initially determined that VEGF is functional in the trafficking of human T cells into skin allografts in vivo in the humanized SCID mouse. In vitro, we found that VEGF enhanced endothelial cell expression of the chemokines monocyte chemoattractant protein 1 and IL-8, and in combination with IFN-gamma synergistically induced endothelial cell production of the potent T cell chemoattractant IFN-inducible protein-10 (IP-10). Treatment of BALB/c (H-2d) recipients of fully MHC-mismatched C57BL/6 (H-2b) donor hearts with anti-VEGF markedly inhibited T cell infiltration of allografts and acute rejection. Anti-VEGF failed to inhibit T cell activation responses in vivo, but inhibited intragraft expression of several endothelial cell adhesion molecules and chemokines, including IP-10. In addition, whereas VEGF expression was increased, neovascularization was not associated with acute rejection, and treatment of allograft recipients with the angiogenesis inhibitor endostatin failed to inhibit leukocyte infiltration of the grafts. Thus, VEGF appears to be functional in acute allograft rejection via its effects on leukocyte trafficking. Together, these observations provide mechanistic insight into the proinflammatory function of VEGF in immunity.

The Role of Vascular Endothelial Growth Factor in the Kidney in Health and Disease

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen, angiogenic factor and enhancer of vascular permeability. Expressed in the epithelial cells of the developing glomerulus and tubular epithelium, VEGF plays an important role in the development and maintenance of the early vasculature of the kidney. Here, we review the available literature regarding the expression and function of VEGF both in the developing and healthy adult kidney. Furthermore, we highlight how VEGF expression is altered in the diseased kidney and how this modulated expression may impact on and reflect underlying functional changes occurring during the disease process. As discussed, many controversial issues remain, particularly concerning the role of VEGF in the diseased kidney. That VEGF has been proposed as a potential future therapeutic target for the management of some renal diseases requires first that the precise role of VEGF in the normal kidney and various renal pathologies be further and more clearly defined.

Expression patterns of vascular endothelial growth factor in human cardiac allografts: association with rejection

BACKGROUND

Vascular endothelial growth factor (VEGF), a major angiogenesis factor, has been found to have proinflammatory properties in vivo in several chronic inflammatory diseases. However, little is known of the expression or function of VEGF in acute and chronic allograft rejection.

METHODS

In a cross-sectional analysis, we evaluated the expression of VEGF by immunohistochemistry in human endomyocardial biopsies (n=101) from 10 cardiac transplant patients. We correlated expression (scores from 0-4) with CD3+ T cell, CD68+ monocyte and macrophage infiltrates, or rejection (International Society of Heart and Lung Transplantation grades 0-4). In addition, we evaluated the temporal patterns of VEGF expression in consecutive biopsies from seven patients (total of 74 biopsies) who were assessed for the development of graft vascular disease (GVD) by intravascular ultrasonography at 1 year posttransplantation.

RESULTS

VEGF is expressed in normal human endomyocardial biopsies at low levels and is induced (scores >1) in association with CD3+ T cells (odds ratio [OR], 19.90; P<0.001), CD68+ monocyte and macrophage infiltrates (OR, 8.49; P<0.001), and all grades of acute rejection (OR, 5.4; P<0.001). Increases in VEGF expression were persistent during the first posttransplant year in biopsies from four patients who demonstrated evidence of GVD (mean annual score of 2.3). In contrast, limited expression of VEGF was found in three patients without GVD (mean annual score 1.2).

CONCLUSIONS

These findings define VEGF as an important proinflammatory cytokine after transplantation and indicate that its expression pattern might identify patients at risk for the development of GVD.

Role of VEGF in kidney development, microvascular maintenance and pathophysiology of renal disease

Vascular endothelial growth factor, VEGF, is essential for endothelial cell differentiation (vasculogenesis) and for the sprouting of new capillaries from preexisting vessels (angiogenesis). In addition, there is strong evidence that VEGF is a survival factor allowing the cells to survive and proliferate under conditions of extreme stress. Hypoxia is a key regulator of VEGF gene expression. Besides hypoxia, many cytokines, hormones and growth factors can up-regulate VEGF mRNA expression in various cell types. VEGF is present in the glomerulus of both the fetal and adult kidney. The VEGF produced by glomerular epithelial cell may be responsible for maintenance of the fenestrated phenotype of glomerular epithelial cells, thus facilitating the high rate of glomerular ultrafiltration. But there is little known about the role of VEGF in the tubule. VEGF is thought to be involved in many kinds of kidney diseases. Whereas VEGF has a beneficial role in the pathogenesis in some diseases, it does harmful action in others. Because VEGF is known to be associated with the pathogenesis of some diseases, such as diabetic nephropathy, renal tumor and polycystic kidney disease, the study about the role of VEGF is going to be a target for disease control. On the other hand, an attempt at enhancing the role of VEGF has to be made at diseases like several ARF models and experimental glomerulonephritis.

Tubulointerstitial disease: role of ischemia and microvascular disease

PURPOSE OF REVIEW

Tubulointerstitial injury is characteristic of aging-associated renal injury and progressive renal disease. Salt-sensitive hypertension is also associated with tubulointerstitial inflammation, especially when accompanied by microvascular disease. Here we summarize recent studies on the pathogenesis and consequences of tubulointerstitial disease, emphasizing the role of ischemia and the microvasculature.

RECENT FINDINGS

Tubulointerstitial injury occurs via several mechanisms of which one of the most important is chronic ischemia. Recent studies suggest that chronic vasoconstriction may contribute to the renal injury associated with angiotensin II, catecholamines, nitric oxide inhibition, hypokalemia, hyperuricemia, and cyclosporine nephropathy. Salt-sensitivity may result as a consequence of the tubulointerstitial inflammatory response to these conditions, and this appears to be perpetuated by the development of preglomerular vascular disease. With progression of tubulointerstitial disease there is also a loss of peritubular capillaries, and stimulating microvascular growth with angiogenic factors can stabilize renal function in these models.

SUMMARY

Ischemia secondary to vasoconstriction or to structural changes of the renal vasculature may have important consequences both in terms of mediating salt-sensitive hypertension and renal progression. Angiogenic factors may have potential benefit in preventing or treating these conditions.