Proinflammatory role of stem cells in abdominal aortic aneurysms.

OBJECTIVE: The pathogenesis of abdominal aortic aneurysm (AAA) formation includes inflammation, vascular smooth muscle cell apoptosis, extracellular matrix degradation, and oxidative stress. That multipotent stem cells have an important role in cardiovascular health and disease has been well established, but the role of stem cells in aortic structural deterioration is poorly defined. We sought to describe the presence of stem cells in human AAA tissue and also investigated the differentiation of stem cells within the aneurysmal aorta. METHODS: Infrarenal aortic wall specimens were collected from patients (n = 7) undergoing open AAA surgical repair. Nonaneurysmal infrarenal aortic control samples (n = 4) were collected at autopsies. Using immunohistochemistry, we compared the abundance of Stro1-positive ((+)), c-kit(+), and CD34(+) cells in aortic tissue. Using double-immunofluorescence staining, we evaluated stem cell differentiation into smooth muscle cells (SM22), fibroblasts (FSP1), and macrophages (CD68). We then investigated the colocalization of CD68(+) cells with the cellular marker of proliferation Ki67. RESULTS: The media and adventitia of infrarenal AAA samples both demonstrated a significantly greater number of c-kit(+) and CD34(+) cells compared with matched control nonaneurysmal aortic tissues; however, the abundance of Stro1(+) cells was not significantly different between the groups. Using double-immunofluorescence staining, we identified that AAA stem cells express the macrophage marker CD68 but not the smooth muscle cell marker SM22 or the fibroblast marker FSP1. CD68(+) cells within the aortic wall colocalized with the cellular marker of proliferation Ki67. CONCLUSIONS: Stem cells are significantly elevated in infrarenal AAA tissue compared with matched control aortic tissue. Our data also demonstrate that AAA stem cells express macrophage surface antigens but not smooth muscle cell or fibroblast markers. Furthermore, CD68(+) cells within the aortic wall colocalized with the cellular marker of proliferation Ki67. These finding suggest an inflammatory/immune role of stem cells during AAA pathogenesis and raise the possibility of localized replenishment therapy within the aneurysm wall.

Immunohistochemical analysis of the natural killer cell cytotoxicity pathway in human abdominal aortic aneurysms.

Our previous analysis using genome-wide microarray expression data revealed extreme overrepresentation of immune related genes belonging the Natural Killer (NK) Cell Mediated Cytotoxicity pathway (hsa04650) in human abdominal aortic aneurysm (AAA). We followed up the microarray studies by immunohistochemical analyses using antibodies against nine members of the NK pathway (VAV1, VAV3, PLCG1, PLCG2, HCST, TYROBP, PTK2B, TNFA, and GZMB) and aortic tissue samples from AAA repair operations (n = 6) and control aortae (n = 8) from age-, sex- and ethnicity-matched donors from autopsies. The results confirmed the microarray results. Two different members of the NK pathway, HCST and GRZB, which act at different steps in the NK-pathway, were actively transcribed and translated into proteins in the same cells in the AAA tissue demonstrated by double staining. Furthermore, double staining with antibodies against CD68 or CD8 together with HCST, TYROBP, PTK2B or PLCG2 revealed that CD68 and CD8 positive cells expressed proteins of the NK-pathway but were not the only inflammatory cells involved in the NK-pathway in the AAA tissue. The results provide strong evidence that the NK Cell Mediated Cytotoxicity Pathway is activated in human AAA and valuable insight for future studies to dissect the pathogenesis of human AAA.

The potential role of DNA methylation in abdominal aortic aneurysms.

Abdominal aortic aneurysm (AAA) is a complex disorder that has a significant impact on the aging population. While both genetic and environmental risk factors have been implicated in AAA formation, the precise genetic markers involved and the factors influencing their expression remain an area of ongoing investigation. DNA methylation has been previously used to study gene silencing in other inflammatory disorders and since AAA has an extensive inflammatory component, we sought to examine the genome-wide DNA methylation profiles in mononuclear blood cells of AAA cases and matched non-AAA controls. To this end, we collected blood samples and isolated mononuclear cells for DNA and RNA extraction from four all male groups: AAA smokers (n = 11), AAA non-smokers (n = 9), control smokers (n = 10) and control non-smokers (n = 11). Methylation data were obtained using the Illumina 450k Human Methylation Bead Chip and analyzed using the R language and multiple Bioconductor packages. Principal component analysis and linear analysis of CpG island subsets identified four regions with significant differences in methylation with respect to AAA: kelch-like family member 35 (KLHL35), calponin 2 (CNN2), serpin peptidase inhibitor clade B (ovalbumin) member 9 (SERPINB9), and adenylate cyclase 10 pseudogene 1 (ADCY10P1). Follow-up studies included RT-PCR and immunostaining for CNN2 and SERPINB9. These findings are novel and suggest DNA methylation may play a role in AAA pathobiology.

Novel pathways in the pathobiology of human abdominal aortic aneurysms.

OBJECTIVES: Abdominal aortic aneurysm (AAA), a dilatation of the infrarenal aorta, typically affects males >65 years. The pathobiological mechanisms of human AAA are poorly understood. The goal of this study was to identify novel pathways involved in the development of AAAs. METHODS: A custom-designed 'AAA-chip' was used to assay 43 of the differentially expressed genes identified in a previously published microarray study between AAA (n = 15) and control (n = 15) infrarenal abdominal aorta. Protein analyses were performed on selected genes. RESULTS: Altogether 38 of the 43 genes on the 'AAA-chip' showed significantly different expression. Novel validated genes in AAA pathobiology included ADCY7, ARL4C, BLNK, FOSB, GATM, LYZ, MFGE8, PRUNE2, PTPRC, SMTN, TMODI and TPM2. These genes represent a wide range of biological functions, such as calcium signaling, development and differentiation, as well as cell adhesion not previously implicated in AAA pathobiology. Protein analyses for GATM, CD4, CXCR4, BLNK, PLEK, LYZ, FOSB, DUSP6, ITGA5 and PTPRC confirmed the mRNA findings. CONCLUSION: The results provide new directions for future research into AAA pathogenesis to study the role of novel genes confirmed here. New treatments and diagnostic tools for AAA could potentially be identified by studying these novel pathways.

Role of complement cascade in abdominal aortic aneurysms.

OBJECTIVE: The goal of this study was to investigate the role of complement cascade genes in the pathobiology of human abdominal aortic aneurysms (AAAs). METHODS AND RESULTS: Results of a genome-wide microarray expression profiling revealed 3274 differentially expressed genes between aneurysmal and control aortic tissue. Interestingly, 13 genes in the complement cascade were significantly differentially expressed between AAA and the controls. In silico analysis of the promoters of the 13 complement cascade genes showed enrichment for transcription factor binding sites for signal transducer and activator of transcription (STAT)5A. Chromatin-immunoprecipitation experiments demonstrated binding of transcription factor STAT5A to the promoters of the majority of the complement cascade genes. Immunohistochemical analysis showed strong staining for C2 in AAA tissues. CONCLUSIONS: These results provide strong evidence that the complement cascade plays a role in human AAA. Based on our microarray studies, the pathway is activated in AAA, particularly via the lectin and classical pathways. The overrepresented binding sites of transcription factor STAT5A in the complement cascade gene promoters suggest a role for STAT5A in the coordinated regulation of complement cascade gene expression.

Analysis of positional candidate genes in the AAA1 susceptibility locus for abdominal aortic aneurysms on chromosome 19.

BACKGROUND: Abdominal aortic aneurysm (AAA) is a complex disorder with multiple genetic risk factors. Using affected relative pair linkage analysis, we previously identified an AAA susceptibility locus on chromosome 19q13. This locus has been designated as the AAA1 susceptibility locus in the Online Mendelian Inheritance in Man (OMIM) database. METHODS: Nine candidate genes were selected from the AAA1 locus based on their function, as well as mRNA expression levels in the aorta. A sample of 394 cases and 419 controls was genotyped for 41 SNPs located in or around the selected nine candidate genes using the Illumina GoldenGate platform. Single marker and haplotype analyses were performed. Three genes (CEBPG, PEPD and CD22) were selected for DNA sequencing based on the association study results, and exonic regions were analyzed. Immunohistochemical staining of aortic tissue sections from AAA and control individuals was carried out for the CD22 and PEPD proteins with specific antibodies. RESULTS: Several SNPs were nominally associated with AAA (p < 0.05). The SNPs with most significant p-values were located near the CCAAT enhancer binding protein (CEBPG), peptidase D (PEPD), and CD22. Haplotype analysis found a nominally associated 5-SNP haplotype in the CEBPG/PEPD locus, as well as a nominally associated 2-SNP haplotype in the CD22 locus. DNA sequencing of the coding regions revealed no variation in CEBPG. Seven sequence variants were identified in PEPD, including three not present in the NCBI SNP (dbSNP) database. Sequencing of all 14 exons of CD22 identified 20 sequence variants, five of which were in the coding region and six were in the 3'-untranslated region. Five variants were not present in dbSNP. Immunohistochemical staining for CD22 revealed protein expression in lymphocytes present in the aneurysmal aortic wall only and no detectable expression in control aorta. PEPD protein was expressed in fibroblasts and myofibroblasts in the media-adventitia border in both aneurysmal and non-aneurysmal tissue samples. CONCLUSIONS: Association testing of the functional positional candidate genes on the AAA1 locus on chromosome 19q13 demonstrated nominal association in three genes. PEPD and CD22 were considered the most promising candidate genes for altering AAA risk, based on gene function, association evidence, gene expression, and protein expression.

Regional expression of HOXA4 along the aorta and its potential role in human abdominal aortic aneurysms.

BACKGROUND: The infrarenal abdominal aorta exhibits increased disease susceptibility relative to other aortic regions. Allograft studies exchanging thoracic and abdominal segments showed that regional susceptibility is maintained regardless of location, suggesting substantial roles for embryological origin, tissue composition and site-specific gene expression. RESULTS: We analyzed gene expression with microarrays in baboon aortas, and found that members of the HOX gene family exhibited spatial expression differences. HOXA4 was chosen for further study, since it had decreased expression in the abdominal compared to the thoracic aorta. Western blot analysis from 24 human aortas demonstrated significantly higher HOXA4 protein levels in thoracic compared to abdominal tissues (P < 0.001). Immunohistochemical staining for HOXA4 showed nuclear and perinuclear staining in endothelial and smooth muscle cells in aorta. The HOXA4 transcript levels were significantly decreased in human abdominal aortic aneurysms (AAAs) compared to age-matched non-aneurysmal controls (P < 0.00004). Cultured human aortic endothelial and smooth muscle cells stimulated with INF-γ (an important inflammatory cytokine in AAA pathogenesis) showed decreased levels of HOXA4 protein (P < 0.0007). CONCLUSIONS: Our results demonstrated spatial variation in expression of HOXA4 in human aortas that persisted into adulthood and that downregulation of HOXA4 expression was associated with AAAs, an important aortic disease of the ageing population.

Role of A-kinase anchoring proteins in cyclic-AMP-mediated Schwann cell proliferation.

Proliferation of Schwann cells during peripheral nerve development is stimulated by the heregulin/neuregulin family of growth factors expressed by neurons. However, for neonatal rat Schwann cells growing in culture, heregulins produce only a weak mitogenic response. Supplementing heregulin with forskolin, an agent that elevates cyclic AMP levels, produces a dramatic increase in the proliferation of cultured Schwann cells. The mechanisms underlying this synergistic effect required for Schwann cell proliferation in vivo is not well established. Characterizing the A-kinase anchoring proteins (AKAPs) in Schwann cells might help identify substrates tethered to and phosphorylated by the cAMP-dependent protein kinase A (PKA). Using an RII overlay assay that detects AKAPs that are bound to the type II regulatory subunits of PKA, we identified AKAP150 in Schwann cells. Western blot analysis revealed that additional AKAPs, specifically AKAP95, and yotiao were also present. Disruption of PKA/AKAP interaction with Ht-31 peptide resulted in an increase in luciferase-conjugated cyclin D3 promoter activity. Transfection with sequence-specific AKAP siRNAs for AKAP150 and AKAP95 produced a marked reduction in cell proliferation. Immunoblot analysis revealed that knock down of AKAP95 protein caused a significant decrease in expression of the cell cycle regulatory proteins cyclin D2, cyclin D3 and the cell survival signal Akt/Protein Kinase B (Akt/PKB). Morphological characterization of Schwann cell AKAPs indicated the presence of nuclear (AKAP95), cytoplasm-associated (AKAP150) and perinuclear (yotiao) A-kinase anchoring proteins. These results indicate a role for AKAP95 and AKAP150 in the synergistic response of Schwann cells to treatment with heregulin and forskolin.

Heat shock protein expression is highly sensitive to ischemia-reperfusion injury in rat kidneys.

Renal injury is known to trigger upregulation of many intracellular signal proteins, but those most sensitive in responding to renal injury remain debatable. We used gene microarray analysis to compare gene expression in rat kidneys subjected to early ischemia-reperfusion injury (30 min of renal ischemia and 3 hr of reperfusion) with non-ischemic kidneys as controls. Among 31,100 genes analyzed, microarray analysis revealed 21 genes with >3-fold increase in expression in ischemic kidneys compared to control non-ischemic kidneys. These upregulated genes included heat shock protein 70 (43-fold), heat shock protein 27 (12-fold), heme oxygenase-1 (10-fold), kidney injury molecule-1 (8-fold), and several subtypes of S100 calcium-binding proteins (3.1- to 7.5-fold). Following a prolonged reperfusion period (48 hr) after 30 min of ischemia, acute tubular necrosis was obvious in the S3 segment of proximal tubules of ischemic kidneys. Injured proximal tubules showed upregulated expression of heat shock protein 70 by immunohistochemistry and by Western blotting. These data suggest that heat shock proteins (eg, heat shock protein 70, heat shock protein 27, and heme oxygenase-1) are crucial for renal cell response to ischemic injury and that heat shock protein 70 is a highly sensitive intracellular marker of ischemia-reperfusion injury.

SMAD3 deficiency promotes vessel wall remodeling, collagen fiber reorganization and leukocyte infiltration in an inflammatory abdominal aortic aneurysm mouse model.

TGF-ß signaling plays critical roles in the pathogenesis of aneurysms; however, it is still unclear whether its role is protective or destructive. In this study, we investigate the role of SMAD3 in the pathogenesis of calcium chloride (CaCl2)-induced abdominal aortic aneurysms (AAA) in Smad3(-/-), Smad3(+/-) and Smad3(+/+) mice. We find that loss of SMAD3 drastically increases wall thickening of the abdominal aorta. Histological analyses show significant vessel wall remodeling with elastic fiber fragmentation. Remarkably, under polarized light, collagen fibers in the hyperplastic adventitia of Smad3(-/-) mice show extensive reorganization accompanied by loosely packed thin and radial collagen fibers. The expressions of matrix metalloproteinases including MMP2, MMP9, and MMP12 and infiltration of macrophage/T cells are drastically enhanced in the vascular wall of Smad3(-/-) mice. We also observe marked increase of NF-κB and ERK1/2 signaling as well as the expression of nuclear Smad2, Smad4 and TGF-ß1 in the vessel wall of Smad3(-/-) mice. In addition, we find that SMAD3 expression is reduced in the dedifferentiated medial smooth muscle-like cells of human AAA patients. These findings provide direct in vivo evidence to support the essential roles of SMAD3 in protecting vessel wall integrity and suppressing inflammation in the pathogenesis of AAAs.

Urine kidney injury molecule-1: a potential non-invasive biomarker for patients with renal cell carcinoma.

BACKGROUND: KIM-1 staining is upregulated in proximal tubule-derived renal cell carcinoma (RCC) including clear renal cell carcinoma and papillary renal cell carcinoma, but not in chromophobe RCC (distal tubular tumor). This study was designed to prospectively examine urine KIM-1 level before and 1 month after removal of renal tumors. PATIENTS AND DESIGN: A total of 19 patients were eventually enrolled in the study based on pre-operative imaging studies. Pre-operative and follow-up (1 month) urine KIM-1 levels were measured. The urine KIM-1 levels (uKIM-1) were then normalized to urine creatinine levels (uCr). Renal tumors were also stained for KIM-1 using immunohistochemical techniques. RESULTS: The KIM-1-negative staining group included 7 cases, and the KIM-1-positive group consisted of 12 cases. The percentage of KIM-1-positive staining RCC cells ranged from 10 to 100 %, and the staining intensity ranged from 1+ to 3+. In both groups, serum creatinine levels were both significantly elevated after nephrectomy. In the KIM-1-negative group, uKIM-1/uCr remained at a similar level before (0.37 ± 0.1 ng/mg Cr) and after nephrectomy (0.32 ± 0.01 ng/mg Cr). However, in the KIM-1-positive group, elevated uKIM-1/uCr at 1.20 ± 0.31 ng/mg Cr was significantly reduced to 0.36 ± 0.1 ng/mg Cr, which was similar to the pre-operative uKIM-1/uCr (0.37 ± 0.1 ng/mg Cr) in the KIM-1-negative group. CONCLUSION: Our small but prospective study showed significant reduction in uKIM-1/uCr after nephrectomy in the KIM-1 positive group, suggesting that urine KIM-1 may serve as a surrogate biomarker for kidney cancer and a non-invasive pre-operative measure to evaluate the malignant potential of renal masses.

MicroRNA expression signature in human abdominal aortic aneurysms.

BACKGROUND: Abdominal aortic aneurysm (AAA) is a dilatation of the aorta affecting most frequently elderly men. Histologically AAAs are characterized by inflammation, vascular smooth muscle cell apoptosis, and extracellular matrix degradation. The mechanisms of AAA formation, progression, and rupture are currently poorly understood. A previous mRNA expression study revealed a large number of differentially expressed genes between AAA and non-aneurysmal control aortas. MicroRNAs (miRNAs), small non-coding RNAs that are post-transcriptional regulators of gene expression, could provide a mechanism for the differential expression of genes in AAA. METHODS: To determine differences in miRNA levels between AAA (n = 5) and control (n = 5) infrarenal aortic tissues, a microarray study was carried out. Results were adjusted using Benjamini-Hochberg correction (adjusted p < 0.05). Real-time quantitative RT-PCR (qRT-PCR) assays with an independent set of 36 AAA and seven control tissues were used for validation. Potential gene targets were retrieved from miRNA target prediction databases Pictar, TargetScan, and MiRTarget2. Networks from the target gene set were generated and examined using the network analysis programs, CytoScape® and Ingenuity Pathway Core Analysis®. RESULTS: A microarray study identified eight miRNAs with significantly different expression levels between AAA and controls (adjusted p < 0.05). Real-time qRT-PCR assays validated the findings for five of the eight miRNAs. A total of 222 predicted miRNA target genes known to be differentially expressed in AAA based on a prior mRNA microarray study were identified. Bioinformatic analyses revealed that several target genes are involved in apoptosis and activation of T cells. CONCLUSIONS: Our genome-wide approach revealed several differentially expressed miRNAs in human AAA tissue suggesting that miRNAs play a role in AAA pathogenesis.

Nephrotic range proteinuria: rare manifestation of scleroderma renal crisis.

The nephrotic range of proteinuria is uncommon in scleroderma renal crisis. This 46-yr-old woman with a medical history of scleroderma presented with very high blood pressure, a sudden elevation of serum creatinine, and proteinuria in the nephrotic range. Renal biopsy revealed onion-skin type of arterial changes with necrosis, confirming the presence of scleroderma nephropathy. Electron microscopy showed diffuse fusion of foot processes. Immunohistochemical staining (IHC) revealed increased expression in glomeruli of phosphorylated mammalian target of rapamycin (p-mTOR). These findings suggest that fusion of foot processes and activation of mammalian target of rapamycin-dependent pathways in podocytes are most likely responsible for the severe proteinuria in this patient with scleroderma nephropathy.

Microarray analysis of gene expression in proliferating Schwann cells: synergistic response of a specific subset of genes to the mitogenic action of heregulin plus forskolin.

Cultured Schwann cells treated with heregulin growth factor require costimulation with a cyclic adenosine monophosphate-elevating agent to produce maximal cell proliferation. Gene chip expression analysis was used to identify genes that are induced or repressed when Schwann cells are treated with heregulin and/or forskolin. By utilizing arrays that contained 8799 probes, the expression of over 1000 genes was found to be significantly changed after 30 hr of treatment with heregulin, forskolin, or heregulin plus forskolin. Hierarchical clustering revealed groups of genes with distinct expression patterns. Of particular interest was a cluster of 140 genes that were up-regulated by heregulin plus forskolin but not by heregulin or forskolin alone. Many of the genes in this group have roles in cell division, such as cyclin B, cyclin D3, E2F-5, cdc 25B, polo-like kinase, and protein kinase C type III. These findings identify a profile of gene expression for Schwann cell proliferation.

Tissue-specific regulation of protein synthesis by insulin and free fatty acids.

The purpose of the study described herein was to investigate how the mammalian target of rapamycin (mTOR)-signaling pathway and eukaryotic initiation factor 2B (eIF2B) activity, both having key roles in the translational control of protein synthesis in skeletal muscle, are regulated in cardiac muscle of rats in response to two different models of altered free fatty acid (FFA) and insulin availability. Protein synthetic rates were reduced in both gastrocnemius and heart of 3-day diabetic rats. The reduction was associated with diminished mTOR-mediated signaling and eIF2B activity in the gastrocnemius but only with diminished mTOR signaling in the heart. In response to the combination of acute hypoinsulinemia and hypolipidemia induced by administration of niacin, protein synthetic rates were also diminished in both gastrocnemius and heart. The niacin-induced changes were associated with diminished mTOR signaling and eIF2B activity in the heart but only with decreased mTOR signaling in the gastrocnemius. In the heart, mTOR signaling and eIF2B activity correlated with cellular energy status and/or redox potential. Thus FFAs may contribute to the translational control of protein synthesis in the heart but not in the gastrocnemius. In contrast, insulin, but not FFAs, is required for the maintenance of protein synthesis in the gastrocnemius.