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

Weighted single-step GWAS identified candidate genes associated with carcass traits in a Chinese yellow-feathered chicken population

Carcass traits in broiler chickens are complex traits that are influenced by multiple genes. To gain deeper insights into the genetic mechanisms underlying carcass traits, here we conducted a weighted single-step genome-wide association study (wssGWAS) in a population of Chinese yellow-feathered chicken. The objective was to identify genomic regions and candidate genes associated with carcass weight (CW), eviscerated weight with giblets (EWG), eviscerated weight (EW), breast muscle weight (BMW), drumstick weight (DW), abdominal fat weight (AFW), abdominal fat percentage (AFP), gizzard weight (GW), and intestine length (IL). A total of 1,338 broiler chickens with phenotypic and pedigree information were included in this study. Of these, 435 chickens were genotyped using a 600K single nucleotide polymorphism chip for association analysis. The results indicate that the most significant regions for 9 traits explained 2.38% to 5.09% of the phenotypic variation, from which the region of 194.53 to 194.63Mb on chromosome 1 with the gene RELT and FAM168A identified on it was significantly associated with CW, EWG, EW, BMW, and DW. Meanwhile, the 5 traits have a strong genetic correlation, indicating that the region and the genes can be used for further research. In addition, some candidate genes associated with skeletal muscle development, fat deposition regulation, intestinal repair, and protection were identified. Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses suggested that the genes are involved in processes such as vascular development (CD34, FGF7, FGFR3, ITGB1BP1, SEMA5A, LOXL2), bone formation (FGFR3, MATN1, MEF2D, DHRS3, SKI, STC1, HOXB1, HOXB3, TIPARP), and anatomical size regulation (ADD2, AKT1, CFTR, EDN3, FLII, HCLS1, ITGB1BP1, SEMA5A, SHC1, ULK1, DSTN, GSK3B, BORCS8, GRIP2). In conclusion, the integration of phenotype, genotype, and pedigree information without creating pseudo-phenotype will facilitate the genetic improvement of carcass traits in chickens, providing valuable insights into the genetic architecture and potential candidate genes underlying carcass traits, enriching our understanding and contributing to the breeding of high-quality broiler chickens.

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.

Association of VEGF haplotypes with breast cancer risk in North-West Indians

BACKGROUND

Angiogenesis is a complex and coordinated process regulated by different growth factors and is one of the hallmark features of cancer. VEGF is one of the most important endothelial cell mitogen and has a critical role in normal physiological and tumor angiogenesis. The objective of this study was to investigate the potential association of haplotypes of six VEGF polymorphisms with breast cancer risk in North-West Indians.

METHODS

Samples of 250 breast cancer patients and 250 age and sex matched controls were genotyped for VEGF -2578C/A, -2549I/D, -460T/C, +405C/G, -7C/T and +936C/T polymorphisms. Haplotypes were generated to determine the better contribution of VEGF polymorphisms to breast cancer risk.

RESULTS

Haplotypes CDTCCC (OR = 0.56, 95%CI, 0.38-0.81; p = 0.003) and CDTGCC (OR = 0.63, 95%CI, 0.44-0.92; p = 0.018) of VEGF -2578C/A, -2549I/D, -460T/C, +405C/G, -7C/T and +936C/T polymorphisms were significantly associated with decreased risk of breast cancer. CDTCCC haplotype was also significantly associated with reduced risk of breast cancer in pre and post menopausal as well as both obese and non obese patients. Haplotype CDTGCC was marginally associated (p = 0.07) with reduced risk of breast cancer in non-obese patients as compared with non-obese controls where as haplotype AICGTC was marginally associated (p = 0.09) with reduced risk of breast cancer in obese patients when compared with non-obese patients. The CDTGCC haplotype was significantly associated with increased risk of breast cancer in premenopausal obese patients (OR = 1.98, 95%CI, 1.10-3.56; p = 0.02).

CONCLUSIONS

Our data indicated that CDTCCC and CDTGCC haplotypes of VEGF -2578C/A, -2549I/D, -460T/C, +405C/G, -7C/T and +936C/T polymorphisms were significantly associated with breast cancer risk in North-West Indians. Further studies on multiethnic groups with larger sample size are required to confirm our results.

Effects of mTOR inhibitor-related proteinuria on progression of cardiac allograft vasculopathy and outcomes among heart transplant recipients

We have previously described the use of sirolimus (SRL) as primary immunosuppression following heart transplantation (HT). The advantages of this approach include attenuation of cardiac allograft vasculopathy (CAV), improvement in glomerular filtration rate (GFR), and reduced malignancy. However, in some patients SRL may cause significant proteinuria. We sought to investigate the prognostic value of proteinuria after conversion to SRL. CAV progression and adverse clinical events were studied. CAV progression was assessed by measuring the Δ change in plaque volume (PV) and plaque index (PI) per year using coronary intravascular ultrasound. Proteinuria was defined as Δ urine protein ≥300 mg/24 h at 1 year after conversion to SRL. Overall, 137 patients were analyzed (26% with proteinuria). Patients with proteinuria had significantly lower GFR (P = .005) but similar GFR during follow-up. Delta PV (P < .001) and Δ PI (P = .001) were significantly higher among patients with proteinuria after adjustment for baseline characteristics. Multivariate Cox regression analysis showed higher all-cause mortality (hazard ratio 3.8; P = .01) with proteinuria but similar risk of CAV-related events (P = .61). Our results indicate that proteinuria is a marker of baseline renal dysfunction, and that HT recipients who develop proteinuria after conversion to SRL have less attenuation of CAV progression and higher mortality risk.

Circulating Long Noncoding RNA LNC-EPHA6 Associates with Acute Rejection after Kidney Transplantation

Acute rejection (AR) of a kidney graft in renal transplant recipients is associated with microvascular injury in graft dysfunction and, ultimately, graft failure. Circulating long noncoding RNAs (lncRNAs) may be suitable markers for vascular injury in the context of AR. Here, we first investigated the effect of AR after kidney transplantation on local vascular integrity and demonstrated that the capillary density markedly decreased in AR kidney biopsies compared to pre-transplant biopsies. Subsequently, we assessed the circulating levels of four lncRNAs (LNC-RPS24, LNC-EPHA6, MALAT1, and LIPCAR), that were previously demonstrated to associate with vascular injury in a cohort of kidney recipients with a stable kidney transplant function (n = 32) and recipients with AR (n = 15). The latter were followed longitudinally six and 12 months after rejection. We found higher levels of circulating LNC-EPHA6 during rejection, compared with renal recipients with a stable kidney function (p = 0.017), that normalized one year after AR. In addition, LNC-RPS24, LNC-EPHA6, and LIPCAR levels correlated significantly with the vascular injury marker soluble thrombomodulin. We conclude that AR and microvascular injury are associated with higher levels of circulating LNC-EPHA6, which emphasizes the potential role of lncRNAs as biomarker in the context of AR.

Elevated serum vascular endothelial growth factor and development of cardiac allograft vasculopathy in children

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a leading cause of retransplantation and death in pediatric heart transplant recipients. Our aim was to evaluate the association between serum vascular endothelial growth factor-A (VEGF) and CAV development in the pediatric heart transplant population.

METHODS

In this retrospective study performed at a university hospital, VEGF concentrations were measured by enzyme-linked immunosorbent assay in banked serum from pediatric heart transplant recipients undergoing routine cardiac catheterization. In subjects with CAV (n = 29), samples were obtained at 2 time-points: before CAV diagnosis (pre-CAV) and at the time of initial CAV diagnosis (CAV). In subjects without CAV (no-CAV, n = 16), only 1 time-point was used. VEGF concentrations (n = 74) were assayed in duplicate.

RESULTS

Serum VEGF is elevated in pediatric heart transplant recipients before catheter-based diagnosis of CAV (no-CAV mean: 144.0 ± 89.05 pg/ml; pre-CAV mean: 316.2 ± 118.3 pg/ml; p = 0.0002). Receiver-operating characteristic curve analysis of pre-CAV VEGF levels demonstrated an area under the curve of 87.7% (p = 0.0002), with a VEGF level of 226.3 pg/ml predicting CAV development with 77.8% sensitivity and 91.7% specificity. VEGF is similarly elevated in subjects with angiographically diagnosed CAV and in those with normal angiography but intravascular ultrasound (IVUS) evidence of CAV.

CONCLUSIONS

The increase in serum VEGF before onset of detectable CAV is fundamental to its utility as a predictive biomarker and suggests further investigations of VEGF in the pathogenesis of CAV are warranted in the pediatric heart transplant population.

Small Molecule Tyrosine Kinase Inhibitor Nintedanib Reduces Development of Cardiac Allograft Vasculopathy in Murine Aortic Allografts

BACKGROUND

Nintedanib is a small molecule tyrosine kinase inhibitor that blocks the action of the platelet-derived growth factor receptor (PDGFR), the vascular endothelial growth factor receptor (VEGFR) and the fibroblast growth factor receptor. All of these receptors have been shown to be involved in the development of cardiac allograft vasculopathy (CAV) after heart transplantation. We therefore hypothesized that blocking these tyrosine kinase receptors with nintedanib could prevent CAV.

METHODS

CBA/JRj (H2k) mice underwent an abdominal aortic transplantation with a graft derived from fully allogeneic C57BL/6JRj (H2b) mice. Nintedanib was given daily from the first day after transplantation until harvest on day 14 for polymerase chain reaction analysis of intragraft cytokine expression or harvest on day 30 for histological analysis of the graft.

RESULTS

Nintedanib treatment resulted in significantly reduced neointima formation in the aortic graft compared with untreated control allografts. Interestingly, the immigration of smooth muscle cells into the neointima was markedly reduced while graft infiltrating macrophages and T cells were not altered in nintedanib-treated animals. The expression of the growth factor PDGF was significantly reduced in the nintedanib group going along with a distinctly reduced expression of the corresponding receptors PDGFR α and -β.

CONCLUSIONS

Treatment with nintedanib caused a significant reduction of CAV development after aortic transplantation in mice. We hypothesize the attenuated neointima formation in nintedanib-treated animals to be mediated by a direct inhibition of intimal smooth muscle cell proliferation via reduced expression of PDGF and the appropriate receptors PDGFR α + β.

Acute Rejection After Kidney Transplantation Associates With Circulating MicroRNAs and Vascular Injury

Supplemental digital content is available in the text.

Background

Acute rejection (AR) of kidney transplants is associated with the loss of endothelial integrity, microvascular rarefaction and, ultimately, graft dysfunction. Circulating angiogenic microRNAs (miRNAs) may serve as markers for microvascular injury. Here, we investigated the short- and long-term effects of AR after kidney transplantation on systemic vascular injury and the associated circulating miRNA profile.

Methods

Systemic vascular injury was determined by measuring capillary tortuosity and density within the oral mucosa as well as by assessing circulating levels of angiopoietin-2/angiopoietin-1 ratio, vascular endothelial growth factor and soluble thrombomodulin. After a pilot study, we selected 48 miRNAs to assess the AR- and microvascular injury associated circulating miRNAs.

Results

In stable transplant recipients (n = 25) and patients with AR (n = 13), which were also studied longitudinally (1, 6, and 12 months post-AR), we found an AR-associated increase in markers of systemic vascular injury, of which vascular endothelial growth factor and soluble thrombomodulin normalized within 1 year after AR. Of the 48 selected miRNAs, 8 were either decreased (miR-135a, miR-199a-3p, and miR-15a) or increased (miR-17, miR-140-3p, miR-130b, miR-122 and miR-192) in AR. Of these, miR-130b, miR-199a, and miR-192 associated with markers of vascular injury, whereas miR-140-3p, miR-130b, miR-122, and miR-192 normalized within 1 year after AR.

Conclusions

AR after kidney transplantation is characterized by systemic microvascular injury and associates with specific circulating miRNA levels.

CD16+ Monocytes and Skewed Macrophage Polarization toward M2 Type Hallmark Heart Transplant Acute Cellular Rejection

Background

During acute heart transplant rejection, infiltration of lymphocytes and monocytes is followed by endothelial injury and eventually myocardial fibrosis. To date, no information is available on monocyte–macrophage-related cellular shifts and their polarization status during rejection. Here, we aimed to define and correlate monocyte–macrophage endomyocardial tissue profiles obtained at rejection and time points prior to rejection, with corresponding serial blood samples in 25 heart transplant recipients experiencing acute cellular rejection. Additionally, 33 healthy individuals served as control.

Materials and methods

Using histology, immunohistochemistry, confocal laser scan microscopy, and digital imaging expression of CD14, CD16, CD56, CD68, CD80, and CD163 were explored to define monocyte and macrophage tissue profiles during rejection. Fibrosis was investigated using Sirius Red stainings of rejection, non-rejection, and 1-year biopsies. Expression of co-stimulatory and migration-related molecules on circulating monocytes, and production potential for pro- and anti-inflammatory cytokines were studied using flow cytometry.

Results

At tissue level, striking CD16+ monocyte infiltration was observed during rejection (p < 0.001). Significantly more CD68+CD163+ M2 macrophages were documented during rejection compared to barely present CD68+CD80+ M1 macrophages. Rejection was associated with severe fibrosis in 1-year biopsies (p < 0.001). Irrespective of rejection status, decreased frequencies of circulating CD16+ monocytes were found in patients compared to healthy individuals. Rejection was reflected by significantly increased CD54 and HLA-DR expression on CD16+ monocytes with retained cytokine production potential.

Conclusion

CD16+ monocytes and M2 macrophages hallmark the correlates of heart transplant acute cellular rejection on tissue level and seem to be associated with fibrosis in the long term.

The intragraft microenvironment as a central determinant of chronic rejection or local immunoregulation/tolerance

PURPOSE OF REVIEW

Chronic rejection is associated with persistent mononuclear cell recruitment, endothelial activation and proliferation, local tissue hypoxia and related biology that enhance effector immune responses. In contrast, the tumor microenvironment elicits signals/factors that inhibit effector T cell responses and rather promote immunoregulation locally within the tissue itself. The identification of immunoregulatory check points and/or secreted factors that are deficient within allografts is of great importance in the understanding and prevention of chronic rejection.

RECENT FINDINGS

The relative deficiency of immunomodulatory molecules (cell surface and secreted) on microvascular endothelial cells within the intragraft microenvironment, is of functional importance in shaping the phenotype of rejection. These regulatory molecules include coinhibitory and/or intracellular regulatory signals/factors that enhance local activation of T regulatory cells. For example, semaphorins may interact with endothelial cells and CD4 T cells to promote local tolerance. Additionally, metabolites and electrolytes within the allograft microenvironment may regulate local effector and regulatory cell responses.

SUMMARY

Multiple factors within allografts shape the microenvironment either towards local immunoregulation or proinflammation. Promoting the expression of intragraft cell surface or secreted molecules that support immunoregulation will be critical for long-term graft survival and/or alloimmune tolerance.

Vascular endothelial growth factor A is associated with the subsequent development of moderate or severe cardiac allograft vasculopathy in pediatric heart transplant recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is the leading cause of chronic allograft loss after pediatric heart transplantation. We hypothesized that biomarkers of endothelial injury and repair would predict CAV development in pediatric heart transplant recipients.

METHODS

Blood was collected from pediatric heart transplant recipients at the time of routine annual coronary angiography, and the concentrations of 13 angiogenesis-related molecules were determined. The primary end point was the presence of moderate or severe CAV by angiography during a 5-year follow-up period.

RESULTS

The study enrolled 48 recipients (57% male) with a median age of 15.5 years (range, 2-22 years) and median time post-transplant of 5.8 years (range, 2-15 years). Eight recipients developed moderate/severe CAV at a median follow-up of 4.7 years, of whom 3 died, 3 underwent retransplantation, 1 had a myocardial infarction, and 1 was listed for retransplantation. Clinical characteristics associated with the development of moderate/severe CAV included prednisone use at enrollment (p = 0.03) and positive recipient cytomegalovirus immunoglobulin G at the time of transplant (p = < 0.01). Multivariable Cox proportional hazards regression identified plasma vascular endothelial growth factor (VEGF)-A concentration greater than 90 pg/ml at the time of blood draw as a significant predictor of time to moderate or severe CAV (hazard ratio, 14.3; 95% confidence interval, 1.3-163). Receiver operating characteristic curve analysis demonstrated that VEGF-A shows moderate performance for association with the subsequent development of CAV (area under the curve, 0.77; 95% confidence interval, 0.61-0.92).

CONCLUSIONS

VEGF-A levels in pediatric heart transplant recipients are associated with clinically important CAV progression within the subsequent 5 years.

Translational implications of endothelial cell dysfunction in association with chronic allograft rejection

Advances in therapeutics have dramatically improved short-term graft survival, but the incidence of chronic rejection has not changed in the past 20 years. New insights into mechanism are sorely needed at this time and it is hoped that the development of predictive biomarkers will pave the way for the emergence of preventative therapeutics. In this review, we discuss a paradigm suggesting that sequential changes within graft endothelial cells (EC) lead to an intragraft microenvironment that favors the development of chronic rejection. Key initial events include EC injury, activation and uncontrolled leukocyte-induced angiogenesis. We propose that all of these early changes in the microvasculature lead to abnormal blood flow patterns, local tissue hypoxia, and an associated overexpression of HIF-1α-inducible genes, including vascular endothelial growth factor. We also discuss how cell intrinsic regulators of mTOR-mediated signaling within EC are of critical importance in microvascular stability and may thus have a role in the inhibition of chronic rejection. Finally, we discuss recent findings indicating that miRNAs may regulate EC stability, and we review their potential as novel non-invasive biomarkers of allograft rejection. Overall, this review provides insights into molecular events, genes, and signals that promote chronic rejection and their potential as biomarkers that serve to support the future development of interruption therapeutics.

Multicenter Analysis of Immune Biomarkers and Heart Transplant Outcomes: Results of the Clinical Trials in Organ Transplantation-05 Study

Identification of biomarkers that assess posttransplant risk is needed to improve long-term outcomes following heart transplantation. The Clinical Trials in Organ Transplantation (CTOT)-05 protocol was an observational, multicenter, cohort study of 200 heart transplant recipients followed for the first posttransplant year. The primary endpoint was a composite of death, graft loss/retransplantation, biopsy-proven acute rejection (BPAR), and cardiac allograft vasculopathy (CAV) as defined by intravascular ultrasound (IVUS). We serially measured anti-HLA- and auto-antibodies, angiogenic proteins, peripheral blood allo-reactivity, and peripheral blood gene expression patterns. We correlated assay results and clinical characteristics with the composite endpoint and its components. The composite endpoint was associated with older donor allografts (p < 0.03) and with recipient anti-HLA antibody (p < 0.04). Recipient CMV-negativity (regardless of donor status) was associated with BPAR (p < 0.001), and increases in plasma vascular endothelial growth factor-C (OR 20; 95%CI:1.9-218) combined with decreases in endothelin-1 (OR 0.14; 95%CI:0.02-0.97) associated with CAV. The remaining biomarkers showed no relationships with the study endpoints. While suboptimal endpoint definitions and lower than anticipated event rates were identified as potential study limitations, the results of this multicenter study do not yet support routine use of the selected assays as noninvasive approaches to detect BPAR and/or CAV following heart transplantation.

Antibodies to HLA Molecules Mimic Agonistic Stimulation to Trigger Vascular Cell Changes and Induce Allograft Injury

Human leukocyte antigen (HLA)-induced signaling in endothelial and smooth muscle cells causes dramatic cytoskeletal rearrangement, increased survival, motility, proliferation, adhesion molecule and chemokine expression, and adhesion of leukocytes. These mechanisms are directly related to endothelial activation, neointimal proliferation, and intragraft accumulation of leukocytes during antibody-mediated rejection (AMR) and chronic rejection. Clustering of HLA by ligands in trans, such as in antigen-presenting cells at the immune synapse, triggers physiological functions analogous to HLA antibody-induced signaling in vascular cells. Emerging evidence has revealed previously unknown functions for HLA beyond antigen presentation, including association with coreceptors in cis to permit signal transduction, and modulation of intracellular signaling downstream of other receptors that may be relevant to HLA signaling in the graft vasculature. We discuss the literature regarding HLA-induced signaling in vascular endothelial and smooth muscle cells, as well as under endogenous biological conditions, and how such signaling relates to functional changes and pathological mechanisms during graft injury.

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.

Apoptosis and angiogenesis: an evolving mechanism for fibrosis

Fibrosis, seen in the liver, lung, heart, kidney, and skin, is a significant global disease burden. Currently, therapeutic treatment is limited, and the number of cases continues to grow. Apoptosis has been identified as a potential initiator and propagator of fibrosis. This review specifically examines the correlation between the presence of apoptotic cells and their effect on fibroblast phenotype and collagen metabolism in several different experimental models of fibrosis. Fibrosis in these models is generally preceded by robust angiogenesis and vascular regression, suggesting that the vascular apoptotic burden may be important to fibrotic outcomes. This review considers the emerging evidence that angiogenesis or vascular regression contributes to fibrosis and identifies initial vascular outgrowth or vascular apoptotic cell presence as possible regulators of fibrosis. A further understanding of the cellular mechanisms of fibrosis may suggest novel methods for the reduction of the fibrotic response and promotion of regeneration.

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.

Molecular imaging of vascular endothelial growth factor receptors in graft arteriosclerosis

OBJECTIVE

Vascular endothelial growth factor (VEGF) signaling plays a key role in the pathogenesis of vascular remodeling, including graft arteriosclerosis. Graft arteriosclerosis is the major cause of late organ failure in cardiac transplantation. We used molecular near-infrared fluorescent imaging with an engineered Cy5.5-labeled single-chain VEGF tracer (scVEGF/Cy) to detect VEGF receptors and vascular remodeling in human coronary artery grafts by molecular imaging.

METHODS AND RESULTS

VEGF receptor specificity of probe uptake was shown by flow cytometry in endothelial cells. In severe combined immunodeficiency mice, transplantation of human coronary artery segments into the aorta followed by adoptive transfer of allogeneic human peripheral blood mononuclear cells led to significant neointima formation in the grafts over a period of 4 weeks. Near-infrared fluorescent imaging of transplant recipients at 4 weeks demonstrated focal uptake of scVEGF/Cy in remodeling artery grafts. Uptake specificity was demonstrated using an inactive homolog of scVEGF/Cy. scVEGF/Cy uptake predominantly localized in the neointima of remodeling coronary arteries and correlated with VEGF receptor-1 but not VEGF receptor-2 expression. There was a significant correlation between scVEGF/Cy uptake and transplanted artery neointima area.

CONCLUSIONS

Molecular imaging of VEGF receptors may provide a noninvasive tool for detection of graft arteriosclerosis in solid organ transplantation.

Significance of vascular endothelial growth factor in growth and peritoneal dissemination of ovarian cancer

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis which drives endothelial cell survival, proliferation, and migration while increasing vascular permeability. Playing an important role in the physiology of normal ovaries, VEGF has also been implicated in the pathogenesis of ovarian cancer. Essentially by promoting tumor angiogenesis and enhancing vascular permeability, VEGF contributes to the development of peritoneal carcinomatosis associated with malignant ascites formation, the characteristic feature of advanced ovarian cancer at diagnosis. In both experimental and clinical studies, VEGF levels have been inversely correlated with survival. Moreover, VEGF inhibition has been shown to inhibit tumor growth and ascites production and to suppress tumor invasion and metastasis. These findings have laid the basis for the clinical evaluation of agents targeting VEGF signaling pathway in patients with ovarian cancer. In this review, we will focus on VEGF involvement in the pathophysiology of ovarian cancer and its contribution to the disease progression and dissemination.

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.

Primary xenografts of human prostate tissue as a model to study angiogenesis induced by reactive stroma

Characterization of the mechanism(s) of androgen-driven human angiogenesis could have significant implications for modeling new forms of anti-angiogenic therapies for CaP and for developing targeted adjuvant therapies to improve efficacy of androgen-deprivation therapy. However, models of angiogenesis by human endothelial cells localized within an intact human prostate tissue architecture are until now extremely limited. This report characterizes the burst of angiogenesis by endogenous human blood vessels in primary xenografts of fresh surgical specimens of benign prostate or prostate cancer (CaP) tissue that occurs between Days 6–14 after transplantation into SCID mice pre-implanted with testosterone pellets. The wave of human angiogenesis was preceded by androgen-mediated up-regulation of VEGF-A expression in the stromal compartment. The neo-vessel network anastomosed to the host mouse vascular system between Days 6–10 post-transplantation, the angiogenic response ceased by Day 15, and by Day 30 the vasculature had matured and stabilized, as indicated by a lack of leakage of serum components into the interstitial tissue space and by association of nascent endothelial cells with mural cells/pericytes. The angiogenic wave was concurrent with the appearance of a reactive stroma phenotype, as determined by staining for α-SMA, Vimentin, Tenascin, Calponin, Desmin and Masson's trichrome, but the reactive stroma phenotype appeared to be largely independent of androgen availability. Transplantation-induced angiogenesis by endogenous human endothelial cells present in primary xenografts of benign and malignant human prostate tissue was preceded by induction of androgen-driven expression of VEGF by the prostate stroma, and was concurrent with and the appearance of a reactive stroma phenotype. Androgen-modulated expression of VEGF-A appeared to be a causal regulator of angiogenesis, and possibly of stromal activation, in human prostate xenografts.

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.

The link between major histocompatibility complex antibodies and cell proliferation

Experimental evidence indicates that donor-specific antibodies targeting major histocompatibility complex classes I and II molecules can elicit the key features of transplant vasculopathy by acting on the graft vasculature in 3 ways: directly activating proliferative, prosurvival, and migratory signaling in the target endothelial and smooth muscle cells; increasing expression of mitogenic factors in vascular endothelial cells, creating a potential proliferative autocrine loop; and promoting recruitment of inflammatory cells that produce mitogenic factors and elicit chronic inflammation, proliferation, and fibrosis. Here, we review the experimental literature showing the complement and Fc-independent effects of major histocompatibility complex classes I and II antibodies on graft vascular cells that may directly contribute to the proliferative aspect of transplant vasculopathy.

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.

Hypoxia and myocardial remodeling in human cardiac allografts: a time-course study

BACKGROUND

Cardiac allografts are known to develop myocardial fibrosis, which may be a cause of progressive cardiac dysfunction. Apart from the renin-angiotensin and transforming growth factor-beta system, hypoxia has been proposed as an important player in the pathogenesis of fibrosis, but its significance remains unclear. This study examines the degree of myocardial fibrosis, cellular remodeling and hypoxic signaling over a time-course of 10 years after human cardiac allograft transplantation.

METHODS

Serial right ventricular biopsies of 57 patients were collected in 6-month intervals after cardiac transplant surgery for a total of 10 years to allow a retrospective longitudinal analysis. Over this period, tissue remodeling, including interstitial fibrosis and cellular changes, were determined morphometrically. Immunohistochemistry (IHC) was used to analyze expression of the following hypoxia-related proteins: hypoxia-induced factor 1-alpha (HIF1alpha); the oxygen sensor prolyl hydroxylase 3 (PHD3); and vascular endothelial growth factor (VEGF).

RESULTS

Fibrosis increased significantly from 12.6 +/- 6.5% at the point of transplantation throughout follow-up to 28.8 +/- 7.7% at 10 years. The DNA content and number of nuclei changed over the period of follow-up, displaying signs of cellular hypertrophy and a loss of myocytes. Whereas HIF1alpha expression revealed a U-shaped pattern with both early and late elevation during fibrogenesis, PHD3 and VEGF expression patterns showed a gradual increase with PHD3 decreasing again in later fibrogenesis.

CONCLUSIONS

In cardiac allografts, extensive and progressive tissue remodeling is present. Hypoxia may play a role in this process by up-regulating HIF1alpha and leading to differential regulation of pro-angiogenic signals.

mTOR-understanding the clinical effects

The target of rapamycin (TOR) is a highly conserved serine/threonine kinase that controls cell growth and metabolism in response to nutrients, growth factors, cellular energy, and stress. The TOR kinase, which was originally discovered in yeast, is also expressed in human cells as mammalian TOR (mTOR). In this review, we focus on how mTOR-inducible signals function in cell protection and cell survival of effector and regulatory T cells as well as its role in endothelial cell biology. We evaluate how signaling is important for vascular endothelial cell growth, survival, and proliferation; and we consider how the function of mTOR in endothelial cells may be clinically important in the rejection process. Understanding the biology of mTOR allows clinicians to use mTOR inhibitors optimally as therapeutics following solid organ transplantation.

Bronchiolitis obliterans in lung transplantation: the good, the bad, and the future

Lung transplantation remains the hope for many incurable pulmonary diseases, such as cystic fibrosis, pulmonary fibrosis, and chronic obstructive pulmonary disease. Remarkable progress has been made in improving outcomes, although the incidence of acute rejection remains more than 50% in the 1st year, and the 5-year graft survival is still less than 50% primarily because of the development of chronic rejection and graft dysfunction. Chronic rejection is characterized by the development of obliterative bronchiolitis in allografts and manifests as bronchiolitis obliterans syndrome in humans with no effective treatment. Previous studies support a role for alloreactive T cells in the development of bronchiolitis obliterans syndrome, but the specific mechanisms are unknown. One major stumbling block to research in the field of lung transplantation has been the lack of physiologic models to study the disease in the laboratory. We will review the current understanding of the immunology of the pathogenesis of obliterative bronchiolitis and will discuss exciting new advances from the laboratory as well as the implications for future research in lung transplantation.

Serum matrix metalloprotease-1 and vascular endothelial growth factor--a predict cardiac allograft rejection

Cardiac allograft rejection is currently diagnosed from endomyocardial biopsies (EMB) that are invasive and impractical to repeat. A serological marker could facilitate rejection monitoring and minimize EMB-associated risks. We investigated the relation of serum matrix metalloprotease (MMP)-1 and vascular endothelial growth factor (VEGF)-A concentrations to cardiac allograft rejection, using 1176 EMBs and serum samples obtained from 208 recipients. Acute cellular rejection was diagnosed in 186 EMBs. Mean week 1 and week 2 serum MMP-1 concentrations predicted rejection (p = 0.001, AUC = 0.80). At the optimal cut-off level of >or=7.5 ng/mL, MMP-1 predicted rejection with 82% sensitivity and 72% specificity. Initial serum MMP-1 <5.3 ng/mL (lowest quartile) was associated with rejection-free outcome in 80% of patients. Both MMP-1 (p < 0.001, AUC = 0.67-0.75) and VEGF-A (p < 0.01, AUC = 0.62-0.67) predicted rejection on the next EMB, while rejection at EMB was identified only by VEGF-A (p < 0.02, AUC = 0.70-0.77). Patients receiving combined cyclosporine-A and everolimus had the lowest serum MMP-1 concentrations. While serum MMP-1 predicts rejection-free outcome and VEGF-A identifies rejection on EMB, both markers predict rejection in follow-up of cardiac transplant recipients. Combination of serum MMP-1 and VEGF-A concentration may be a noninvasive prognostic marker of cardiac allograft rejection, and could have important implications for choice of surveillance and immunosuppression protocols.

CD40-induced signaling in human endothelial cells results in mTORC2- and Akt-dependent expression of vascular endothelial growth factor in vitro and in vivo

We have examined CD40-dependent signals in endothelial cells (EC) mediating the expression of vascular endothelial growth factor (VEGF) and VEGF-induced angiogenesis. We treated confluent cultures of EC with soluble CD40L (sCD40L), and by Western blot found a marked increase in the phosphorylation of Akt, 4EBP-1, and S6K1, compared with untreated cells. EC were transfected with a full-length VEGF promoter-luciferase construct and cultured in the absence or presence of rapamycin and sCD40L. We found that rapamycin, which blocks mTORC1 and mTORC2 signaling, inhibited sCD40L-mediated transactivation of VEGF. In addition, by Western blot, we found that the transfection of EC with small interfering RNA (siRNA) to rictor (to inhibit mTORC2), and not raptor (to inhibit mTORC1), inhibited sCD40L-dependent protein expression of VEGF. In additions, we found that basal levels of phosphorylated Akt as well as VEGF were increased in EC transfected with the raptor siRNA. Also, rapamycin failed to inhibit VEGF promoter activation, as well as VEGF protein expression in EC transfected with a constitutively active construct of Akt, further demonstrating that mTORC1 is not necessary for CD40- and Akt-induced expression of VEGF. Finally, we injected human CD40L-transfected fibroblasts or mock transfectants into human skin on SCID mice. We found that the injection of CD40L transfectants, but not mock cells, resulted in VEGF expression and mediated a marked angiogenesis reaction, and this response was reduced in mice treated with rapamycin. Together, these observations indicate that mTORC2 and Akt facilitate CD40-inducible expression of VEGF in EC, which is of clinical importance in tumor growth and the progression of chronic inflammatory diseases.

Overexpression of vascular endothelial growth factor and the development of post-transplantation cancer

Cancer is an increasing and major problem after solid organ transplantation. In part, the increased cancer risk is associated with the use of immunosuppressive agents, especially calcineurin inhibitors. We propose that the effect of calcineurin inhibitors on the expression of vascular endothelial growth factor (VEGF) leads to an angiogenic milieu that favors tumor growth. Here, we used 786-0 human renal cancer cells to investigate the effect of cyclosporine (CsA) on VEGF expression. Using a full-length VEGF promoter-luciferase construct, we found that CsA markedly induced VEGF transcriptional activation through the protein kinase C (PKC) signaling pathway, specifically involving PKC zeta and PKC delta isoforms. Moreover, CsA promoted the association of PKC zeta and PKC delta with the transcription factor Sp1 as observed by immunoprecipitation assays. Using promoter deletion constructs, we found that CsA-mediated VEGF transcription was primarily Sp1 dependent. Furthermore, CsA-induced and PKC-Sp1-mediated VEGF transcriptional activation was partially inhibited by von Hippel-Lindau protein. CsA also promoted the progression of human renal tumors in vivo, wherein VEGF is overexpressed. Finally, to evaluate the in vivo significance of CsA-induced VEGF overexpression in terms of post-transplantation tumor development, we injected CT26 murine carcinoma cells (known to form angiogenic tumors) into mice with fully MHC mismatched cardiac transplants. We observed that therapeutic doses of CsA increased tumor size and VEGF mRNA expression and also enhanced tumor angiogenesis. However, coadministration of a blocking anti-VEGF antibody inhibited this CsA-mediated tumor growth. Collectively, these findings define PKC-mediated VEGF transcriptional activation as a key component in the progression of CsA-induced post-transplantation cancer.

Genetic polymorphisms impact the risk of acute rejection in pediatric heart transplantation: a multi-institutional study

OBJECTIVE

The objective of this study was to determine the association between the genetic polymorphisms of proinflammatory and regulatory cytokines and long-term rates of repeat and late acute rejection episodes in pediatric heart transplant (PHTx) recipients.

METHODS

Three hundred twenty-three PHTx recipients: 205 White non-Hispanic, 43 Black non-Hispanic, and 75 Hispanic were analyzed for time to first repeat and late acute rejection episodes by race, age at transplantation, and gene polymorphism (interleukin [IL]-6, -174 G/C, IL-10, -1082 G/A, -819 C/T, 592 C/A; vascular endothelial growth factor (VEGF) -2578 C/A, -460 C/T, +405 C/G; tumor necrosis factor alpha (TNF-alpha)-308 G/A).

RESULTS

Recipient black race and older age at transplant were risk factors for both repeat and late rejections, though black race was more significantly related to late rejection (P=0.006). Individually, TNF-alpha high, IL-6 high, VEGF high, and IL-10 low phenotypes did not impact the risk of repeat or late rejection. However, the combination VEGF high/IL-6 high and IL-10 low was associated with increased estimated risk of late rejection (P=0.0004) and only marginally with repeat rejection (P=0.051). In a multivariate analysis, adjusting for age and race, VEGF high/IL-6 high and IL-10 low still remained an independent risk factor for late acute rejection (RR=1.91, P<0.001).

CONCLUSION

This is the largest multicenter study to document the impact of genetic polymorphism combinations on PHTx recipients' outcome. The high proinflammatory (VEGF high/IL-6 high) and lower regulatory (IL-10 low) cytokine gene polymorphism profile exhibited increased risk for late rejection, irrespective of age and race/ethnicity.

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.

Lack of association of the vascular endothelial growth factor gene polymorphisms with Kawasaki disease in Taiwanese children

INTRODUCTION

Kawasaki disease (KD) is an acute febrile vasculitis of unknown etiology that mainly occurs in infants and children. Clinical and histopathologic findings suggest that vascular endothelial growth factor (VEGF) is involved in the coronary artery lesions (CALs) development in KD. This study hypothesized that specific VEGF gene polymorphisms and their haplotypes are associated with KD susceptibility and CAL development in Taiwanese children.

SUBJECTS AND METHODS

The VEGF -2578 A/C, -634 G/C, and +936 C/T single-nucleotide polymorphisms (SNPs) were genotyped in 156 children with KD and 672 ethnically matched healthy controls using the Pre-Developed TaqMan Allelic Discrimination Assay.

RESULTS

No significant differences in genotype, allele, carrier, and haplotype frequencies of the three SNPs were found between healthy controls and children with KD or between patients with and without CAL.

CONCLUSION

Our data suggest that VEGF -2578 A/C, -634 G/C, and +936 C/T SNPs do not confer increased susceptibility to KD or to CAL development.

Maintenance of airway epithelium in acutely rejected orthotopic vascularized mouse lung transplants

Lung transplantation remains the only therapeutic option for many patients suffering from end-stage pulmonary disease. Long-term success after lung transplantation is severely limited by the development of bronchiolitis obliterans. The murine heterotopic tracheal transplantation model has been widely used for studies investigating pathogenesis of obliterative airway disease and immunosuppressive strategies to prevent its development. Despite its utility, this model employs proximal airway that lacks airflow and is not vascularized. We have developed a novel model of orthotopic vascularized lung transplantation in the mouse, which leads to severe vascular rejection in allogeneic strain combinations. Here we characterize differences in the fate of airway epithelial cells in nonimmunosuppressed heterotopic tracheal and vascularized lung allograft models over 28 days. Up-regulation of growth factors that are thought to be critical for the development of airway fibrosis and interstitial collagen deposition were similar in both models. However, while loss of airway epithelial cells occurred in the tracheal model, airway epithelium remained intact and fully differentiated in lung allografts, despite profound vascular rejection. Moreover, we demonstrate expression of the anti-apoptotic protein Bcl-2 in airway epithelial cells of acutely rejected lung allografts. These findings suggest that in addition to alloimmune responses, other stimuli may be required for the destruction of airway epithelial cells. Thus, the model of vascularized mouse lung transplantation may provide a new and more physiologic experimental tool to study the interaction between immune and nonimmune mechanisms affecting airway pathology in lung allografts.

VEGFR-1 and -2 Regulate Inflammation, Myocardial Angiogenesis, and Arteriosclerosis in Chronically Rejecting Cardiac Allografts

OBJECTIVE

Interplay between inflammation and angiogenesis is important in pathological reparative processes such as arteriosclerosis. We investigated how the two vascular endothelial growth factor receptors VEGFR-1 and -2 regulate these events in chronically rejecting cardiac allografts.

METHODS AND RESULTS

Chronic rejection in mouse cardiac allografts induced primitive myocardial, adventitial, and intimal angiogenesis with endothelial expression of CD31, stem cell marker c-kit, and VEGFR-2. Experiments using marker gene mice or rats as cardiac allograft recipients revealed that replacement of cardiac allograft endothelial cells with recipient bone marrow- or non-bone marrow-derived cells was rare and restricted only to sites with severe injury. Targeting VEGFR-1 with neutralizing antibodies in mice reduced allograft CD11b+ myelomonocyte infiltration and allograft arteriosclerosis. VEGFR-2 inhibition prevented myocardial c-kit+ and CD31+ angiogenesis in the allograft, and decreased allograft inflammation and arteriosclerosis.

CONCLUSIONS

These results suggest interplay of inflammation, primitive donor-derived myocardial angiogenesis, and arteriosclerosis in transplanted hearts, and that targeting VEGFR-1 and -2 differentially regulate these pathological reparative processes.

Role of platelet-derived growth factor and vascular endothelial growth factor in obliterative airway disease

RATIONALE

Platelet-derived growth factor (PDGF) is an important smooth muscle cell mitogen, and vascular endothelial growth factor (VEGF) is a known angiogenic and proinflammatory growth factor. We hypothesized that specific therapy aimed at these growth factors might inhibit the development of experimental obliterative airway disease (OAD).

METHODS

In fully mismatched rat tracheal allografts, we used imatinib and PTK/ZK, either alone or in combination, to block PDGF and VEGF receptor protein tyrosine kinase (RTK) action, respectively. Prophylaxis was initiated at the time of transplantation. Early treatment was commenced on Day 7 during the inflammatory phase and late treatment on Day 14 during the fibroproliferative phase of OAD. No immunosuppression was administered.

MEASUREMENTS AND MAIN RESULTS

Prophylaxis with either PTK/ZK or imatinib alone significantly reduced OAD, and combined prophylaxis completely prevented its development. Early treatment with PTK/ZK and imatinib also effectively reduced the development of OAD. Late treatment failed to show significant efficacy. Blocking VEGF RTK action with PTK/ZK reduced the activation of allograft blood vessels and the number of lymph vessels in the allograft airway wall, and significantly diminished allograft inflammation, whereas PDGF blockade with imatinib inhibited the growth of smooth muscle cells in the proliferating lesion.

CONCLUSIONS

Combined prophylactic PDGF and VEGF RTK blockade completely prevents the development of OAD. Also, when early treatment with PTK/ZK and imatinib is commenced during the inflammatory phase of OAD development, it significantly attenuates the development of tracheal occlusion, suggesting that these drugs could potentially be used to treat bronchiolitis obliterans syndrome in its early phase.

Angiogenic Growth Factors in Cardiac Allograft Rejection

Normal adult vasculature is in a quiescent state. In transplanted hearts, peri- and postoperative ischemic and alloimmune stimuli may be interpreted as inadequate tissue perfusion leading to activation of angiogenic signaling. Although this may have protective functions, improper activation of cardiac allograft endothelial cells and smooth muscle cells may actually result in impaired survival of cardiac allografts. In this paper, we review the current knowledge on angiogenic growth factors, vascular endothelial growth factor, angiopoietins, and platelet-derived growth factor in cardiac allografts. We also discuss the potential for therapies aimed at angiogenic growth factors in preventing and treating cardiac allograft rejection and transplant coronary artery disease.

Vascular endothelial growth factor-induced signaling pathways in endothelial cells that mediate overexpression of the chemokine IFN-gamma-inducible protein of 10 kDa in vitro and in vivo

Vascular endothelial growth factor (VEGF), an angiogenesis factor, has recently been found to have potent proinflammatory properties in vivo. However, the mechanism by which it mediates inflammation is poorly understood. In this study, we have evaluated the function of VEGF on the induced expression and function of the T cell chemoattractant chemokine IFN-gamma-inducible protein of 10 kDa (IP-10). In vitro, we find that VEGF augments the effect of IFN-gamma on the induction of IP-10 mRNA and protein expression in endothelial cells. Moreover, we show that VEGF and IFN-gamma regulate the activation of the IP-10 promoter, and that the kinases PI3K, phosphoinositide-dependent kinase 1, and Akt act as intermediary signaling molecules for cytokine-inducible IP-10 transcriptional activation in endothelial cells. To examine whether VEGF is functional for IP-10 expression in vivo, Chinese hamster ovary cells that were designed to secrete VEGF were injected s.c. into the skin of nude mice and were found to mediate a time-dependent increase in IP-10 mRNA. This response was reduced in animals treated systemically with the PI3K inhibitor wortmannin. When the Chinese hamster ovary cells expressing VEGF plasmid were injected s.c. into C57BL/6 wild-type or CXCR3-/- mice, they elicited an inflammatory reaction in wild-type but not in CXCR3-/- mice. Collectively, these findings indicate that VEGF-induced augmentation of IP-10 expression is a major mechanism underlying its proinflammatory function.

Angiogenesis and endothelial cell repair in renal disease and allograft rejection

This review discusses the concept that the turnover and replacement of endothelial cells is a major mechanism in the maintenance of vascular integrity within the kidney. CD133+CD34+KDR+ endothelial cell progenitor cells emigrate from the bone marrow and differentiate into CD34+KDR+ expressing cells, which are present in high numbers within the circulation. These progenitor cells are available for recruitment into normal or inflamed tissues to facilitate endothelial cell repair. In several forms of renal disease, proinflammatory insults mediate oxidative stress, senescence, and sloughing of endothelial cells. A lack of growth factors or an inefficient recruitment of endothelial cell progenitors results in hypoxic tissue injury and accelerates the process of chronic renal failure. Augmentation of vascular repair by the provision of growth factors such as vascular endothelial growth factor or by the transfer of progenitor cells directly into the kidney can be protective and prevent ongoing interstitial damage. In allografts, persistent injury results in excessive turnover of graft vascular endothelial cells. Moreover, chronic damage elicits a response that is associated with the recruitment of both leukocytes and endothelial cell progenitors, facilitating an overlapping process of inflammation and angiogenesis. Because the angiogenesis reaction itself is proinflammatory, this process becomes self-sustaining. Collectively, these data indicate that angiogenesis and endothelial cell turnover are important in renal inflammatory processes and allograft rejection. Manipulation of the response may have therapeutic implications to protect against injury and chronic disease processes.

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.

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.

Dual role of vascular endothelial growth factor in hepatic ischemia-reperfusion injury

BACKGROUND

Vascular endothelial growth factor (VEGF), a major angiogenic factor, mediates a variety of disease conditions through promotion of angiogenesis. It also plays a critical role as a potent proinflammatory cytokine in a variety of physiologic and pathologic immune responses. In the present study, we evaluated the expression of VEGF in hepatic warm ischemia-reperfusion (I/R) injury and examined the effect of recombinant human (rh)VEGF administration in an established murine model.

METHOD

The expression of VEGF in the liver was assessed by quantitative real-time polymerase chain reaction and immunohistochemistry during I/R injury using 70% partial hepatic ischemia model. The effect of rhVEGF administration on I/R injury was evaluated by measuring liver function and histology. In addition, local inducible nitric oxide synthase (iNOS) and endothelial NO synthase expressions were examined to address the underlying mechanisms.

RESULTS

The local expression of VEGF was significantly up-regulated at 2 hours after reperfusion after 60 minutes of ischemia compared with that in the naive liver. VEGF was expressed predominantly in CD11b+ cells infiltrating into the ischemic liver. The administration of rhVEGF had a significant protective effect on ischemic injury in the liver. This effect was associated with the up-regulation of iNOS expression in the rhVEGF-treated liver.

CONCLUSION

We demonstrate a dual role of VEGF in hepatic warm I/R injury. Although endogenous VEGF is expressed and functional to initiate hepatic I/R injury, exogenous rhVEGF has a beneficial effect on the ischemic liver. These data may provide new insights into the role of VEGF as well as pathophysiology of hepatic I/R injury.