Decorin Protein Research Articles

Role of Glomerular Proteoglycans in IgA Nephropathy

Mesangial matrix expansion is a prominent feature of the most common form of glomerulonephritis, IgA nephropathy (IgAN). To find molecular markers and improve the understanding of the disease, the gene and protein expression of proteoglycans were investigated in biopsies from IgAN patients and correlated to clinical and morphological data. We collected and microdissected renal biopsies from IgAN patients (n = 19) and from healthy kidney donors (n = 14). Patients were followed for an average time of 4 years and blood pressure was according to target guidelines. Distinct patterns of gene expression were seen in glomerular and tubulo-interstitial cells. Three of the proteoglycans investigated were found to be of special interest and upregulated in glomeruli: perlecan, decorin and biglycan. Perlecan gene expression negatively correlated to albumin excretion and progress of the disease. Abundant decorin protein expression was found in sclerotic glomeruli, but not in unaffected glomeruli from IgAN patients or in controls. Transforming growth factor beta (TGF-β), known to interact with perlecan, decorin and biglycan, were upregulated both on gene and protein level in the glomeruli. This study provides further insight into the molecular mechanisms involved in mesangial matrix expansion in IgAN. We conclude that perlecan is a possible prognostic marker for patients with IgAN. In addition, the up-regulation of biglycan and decorin, as well as TGF-β itself, indicate that regulation of TGF-β, and other profibrotic markers plays a role in IgAN pathology.

Effects of Ultraviolet-A and Riboflavin on the Interaction of Collagen and Proteoglycans during Corneal Cross-linking

Corneal cross-linking using riboflavin and ultraviolet-A (RFUVA) is a clinical treatment targeting the stroma in progressive keratoconus. The stroma contains keratocan, lumican, mimecan, and decorin, core proteins of major proteoglycans (PGs) that bind collagen fibrils, playing important roles in stromal transparency. Here, a model reaction system using purified, non-glycosylated PG core proteins in solution in vitro has been compared with reactions inside an intact cornea, ex vivo, revealing effects of RFUVA on interactions between PGs and collagen cross-linking. Irradiation with UVA and riboflavin cross-links collagen α and β chains into larger polymers. In addition, RFUVA cross-links PG core proteins, forming higher molecular weight polymers. When collagen type I is mixed with individual purified, non-glycosylated PG core proteins in solution in vitro and subjected to RFUVA, both keratocan and lumican strongly inhibit collagen cross-linking. However, mimecan and decorin do not inhibit but instead form cross-links with collagen, forming new high molecular weight polymers. In contrast, corneal glycosaminoglycans, keratan sulfate and chondroitin sulfate, in isolation from their core proteins, are not cross-linked by RFUVA and do not form cross-links with collagen. Significantly, when RFUVA is conducted on intact corneas ex vivo, both keratocan and lumican, in their natively glycosylated form, do form cross-links with collagen. Thus, RFUVA causes cross-linking of collagen molecules among themselves and PG core proteins among themselves, together with limited linkages between collagen and keratocan, lumican, mimecan, and decorin. RFUVA as a diagnostic tool reveals that keratocan and lumican core proteins interact with collagen very differently than do mimecan and decorin.

Mapping structural landmarks, ligand binding sites, and missense mutations to the collagen IV heterotrimers predicts major functional domains, novel interactions, and variation in phenotypes in inherited diseases affecting basement membranes

Collagen IV is the major protein found in basement membranes. It comprises three heterotrimers (α1α1α2, α3α4α5, and α5α5α6) that form distinct networks, and are responsible for membrane strength and integrity.We constructed linear maps of the collagen IV heterotrimers ("interactomes") that indicated major structural landmarks, known and predicted ligand-binding sites, and missense mutations, in order to identify functional and disease-associated domains, potential interactions between ligands, and genotype–phenotype relationships. The maps documented more than 30 known ligand-binding sites as well as motifs for integrins, heparin, von Willebrand factor (VWF), decorin, and bone morphogenetic protein (BMP). They predicted functional domains for angiogenesis and haemostasis, and disease domains for autoimmunity, tumor growth and inhibition, infection, and glycation. Cooperative ligand interactions were indicated by binding site proximity, for example, between integrins, matrix metalloproteinases, and heparin. The maps indicated that mutations affecting major ligand-binding sites, for example, for Von Hippel Lindau (VHL) protein in the α1 chain or integrins in the α5 chain, resulted in distinctive phenotypes (Hereditary Angiopathy, Nephropathy, Aneurysms, and muscle Cramps [HANAC] syndrome, and early-onset Alport syndrome, respectively). These maps further our understanding of basement membrane biology and disease, and suggest novel membrane interactions, functions, and therapeutic targets.

Decorin Antagonizes Met Receptor Activity and Down-regulates β-Catenin and Myc Levels

A theme emerging during the past few years is that members of the small leucine-rich proteoglycan gene family affect cell growth by interacting with multiple receptor tyrosine kinases (RTKs), mostly by a physical down-regulation of the receptors, thereby depriving tumor cells of pro-survival signals. Decorin binds and down-regulates several RTKs, including Met, the receptor for hepatocyte growth factor. Here we demonstrate that decorin blocks several biological activities mediated by the Met signaling axis, including cell scatter, evasion, and migration. These effects were mediated by a profound down-regulation of noncanonical β-catenin levels. In addition, Myc, a downstream target of β-catenin, was markedly down-regulated by decorin, whereas phosphorylation of Myc at threonine 58 was markedly induced. The latter is known to destabilize Myc and target it for proteasomal degradation. We also discovered that systemic delivery of decorin using three distinct tumor xenograft models caused down-regulation of Met and a concurrent suppression of β-catenin and Myc levels. We found that decorin protein core labeled with the near infrared dye IR800 specifically targeted the tumor cells expressing Met. Even 68-h post-injection, decorin was found to reside within the tumor xenografts with little or no binding to other tissues. Collectively, our results indicate a role for a secreted proteoglycan in suppressing the expression of key oncogenic factors required for tumor progression.

Plasma decorin predicts the presence of esophageal squamous cell carcinoma

Using a microarray technique, we found decorin to be underexpressed, but osteopontin (OPN) to be overexpressed, in esophageal squamous cell carcinoma (ESCC). This study aims to examine whether plasma decorin and OPN plus personal substances use (tobacco, alcohol and areca) can serve as suitable clinical markers to predict the presence of ESCC. In total, 570 archived plasma specimens (275 patients and 295 controls) were collected from 2 medical centers in Taiwan between 2000 and 2008. Decorin and OPN protein levels were measured by ELISA. Means and standard deviation of plasma decorin were 5.6 + or - 3.6 ng/ml in case patients, which were significantly lower than those in controls (7.8 + or - 3.1, p < 0.0001). Plasma OPN levels in case patients were not significantly different from controls (p = 0.33). When compared to subjects with the lowest quartile of plasma decorin, those with the highest quartile one had a significantly lower risk to have ESCC (Adjusted OR = 0.03, p < 0.001). Receiver operator characteristic (ROC) analysis was performed for the combination of plasma decorin and 3 substances use (smoke, alcohol and areca) for the patients compared with the controls. The area under the curve was 88.6% and the optimal cut-point of ROC curve (any 3 factors) had 73.5% sensitivity and 90.2% specificity with approximately 82% of corrected classification. Plasma decorin, but not OPN, is a potential clinical marker for the detection of ESCC. When plasma decorin plus the use of the 3 substances are combined, this factor cluster could be used to detect the presence of ESCC.

Inositol-requiring enzyme 1α is a key regulator of angiogenesis and invasion in malignant glioma

Inositol-requiring enzyme 1 (IRE1) is a proximal endoplasmic reticulum (ER) stress sensor and a central mediator of the unfolded protein response. In a human glioma model, inhibition of IRE1alpha correlated with down-regulation of prevalent proangiogenic factors such as VEGF-A, IL-1beta, IL-6, and IL-8. Significant up-regulation of antiangiogenic gene transcripts was also apparent. These transcripts encode SPARC, decorin, thrombospondin-1, and other matrix proteins functionally linked to mesenchymal differentiation and glioma invasiveness. In vivo, using both the chick chorio-allantoic membrane assay and a mouse orthotopic brain model, we observed in tumors underexpressing IRE1: (i) reduction of angiogenesis and blood perfusion, (ii) a decreased growth rate, and (iii) extensive invasiveness and blood vessel cooption. This phenotypic change was consistently associated with increased overall survival in glioma-implanted recipient mice. Ectopic expression of IL-6 in IRE1-deficient tumors restored angiogenesis and neutralized vessel cooption but did not reverse the mesenchymal/infiltrative cell phenotype. The ischemia-responsive IRE1 protein is thus identified as a key regulator of tumor neovascularization and invasiveness.

Decorin Accumulation Contributes to the Stromal Opacities Found in Congenital Stromal Corneal Dystrophy

Congenital stromal corneal dystrophy (CSCD) is characterized by stromal opacities that morphologically are seen as interlamellar layers of amorphous substance with small filaments, the nature of which has hitherto been unknown. CSCD is associated with truncating mutations in the decorin gene (DCN). To understand the molecular basis for the corneal opacities we analyzed the expression of decorin in this disease, both at the morphologic and the molecular level. Corneal specimens were examined after contrast enhancement with cuprolinic blue and by immunoelectron microscopy. Decorin protein from corneal tissue and keratocyte culture was studied by immunoblot analysis before and after O- and N-deglycosylation. The relative level of DCN mRNA expression was examined using Q-RT-PCR, and cDNA was sequenced. Recombinant wild-type and truncated decorin transiently expressed in HEK293 cells were analyzed by gel filtration and immunoblotting. The areas of interlamellar filaments were stained by cuprolinic blue. Immunoelectron microscopy using decorin antibodies revealed intense labeling of these areas. Both wild-type and truncated decorin protein was expressed in corneal tissue and keratocytes of affected persons. When decorin expressed in HEK293 cells was examined by gel filtration, the truncated decorin eluted as high molecular weight aggregates. Accumulation of decorin was found in the interlamellar areas of amorphous substance. The truncated decorin is present in CSCD corneas, and there is evidence it may aggregate in vitro. Thus, decorin accumulation appears to contribute to the stromal opacities that are characteristic of CSCD.

Decorin expression is decreased in human idiopathic fetal growth restriction

Fetal growth restriction (FGR) is a clinically significant pregnancy disorder in which the fetus fails to achieve its full growth potential in utero. Most cases of FGR are idiopathic and are associated with placental thrombosis. Previous studies suggest that proteoglycans, such as decorin, that contain the glycosaminoglycan dermatan sulfate are the principal anticoagulants in the normal placenta. The present study investigated decorin expression in placentas from pregnancies complicated by idiopathic FGR (n = 26) and gestation-matched controls (n = 27). Real-time polymerase chain reaction demonstrated significantly reduced decorin mRNA expression in FGR compared with control (1.52 +/- 0.14 v. 2.21 +/- 0.22, respectively; P < 0.01). Immunoblotting revealed decreased decorin protein (40 kDa) expression in FGR compared with controls (420.8 +/- 39.0 v. 690.1 +/- 42.2, respectively; n = 12 in each group; P = 0.0007). Immunohistochemistry demonstrated the presence of immunoreactive decorin protein in the placental villous stroma surrounding the fetal capillaries and a significant decrease in decorin protein presence in FGR compared with control (1.75 +/- 0.66 v. 2.98 +/- 1.12, respectively; n = 6 in each group; P < 0.01, t-test). This is the first study to demonstrate reduced decorin in idiopathic FGR, indicating a potentially significant role for decorin in the aetiology of placental thrombosis in idiopathic FGR.

Altered production of extra-cellular matrix components by muscle-derived Duchenne muscular dystrophy fibroblasts before and after TGF-β1 treatment

To probe pro-fibrotic mechanisms in dystrophic muscle, we isolated primary fibroblasts from Duchenne muscular dystrophy (DMD) and control muscle biopsies and induced transdifferentiation in myofibroblasts by transforming growth factor beta1 (TGF-beta1) treatment. We compared proliferating activity, soluble collagen production, and transcript and protein levels of decorin, myostatin, TGF-beta1, matrix metalloproteinase-1 (MMP-1; interstitial collagenase), MMP-2 (gelatinase), MMP-3 (stromelysin), MMP-7 (matrilysin), and the tissue inhibitors of metalloproteinases inhibitors (TIMPs) 1-4, in fibroblasts and myofibroblasts. Principal differences included a significantly greater proliferation rate and soluble collagen production, a significant upregulation of decorin, myostatin and MMP-7 transcripts and proteins, and a significant downregulation of MMP-1 and TIMP-3 transcripts (with MMP-1 protein being reduced as shown by enzyme-linked immunosorbent assay and TIMP-3 protein apparently being reduced on Western blot), in untreated DMD fibroblasts compared with controls. TGF-beta1 transdifferentiation significantly lowered decorin and myostatin and significantly increased TGF-beta1 transcript and protein, significantly increased MMP-1 and TIMP-3, and significantly lowered MMP-7 transcript and protein in DMD cells compared with pretreatment controls. The differences between DMD and control fibroblasts showed that DMD fibroblasts had a profibrotic phenotype, accentuated by TGF-beta1 treatment. Dystrophin absence itself could exert a direct influence on the homeostasis of the extracellular matrix (ECM) by allowing leakage of cellular components to the extracellular space or by abnormal cellular uptake of extracellular growth factors, cytokines, or enzymes influencing muscle fibroblasts either directly by altering adhesion properties or indirectly by interactions with molecules released into the ECM by muscle or inflammatory cells. The transdifferentiation of muscle fibroblasts might serve as a simplified model of fibrosis for further elucidation of the mechanisms of muscle fibrosis and for testing possible anti-fibrotic agents.

Presence of activating KRAS mutations correlates significantly with expression of tumour suppressor genes DCN and TPM1 in colorectal cancer

BackgroundDespite identification of the major genes and pathways involved in the development of colorectal cancer (CRC), it has become obvious that several steps in these pathways might be bypassed by other as yet unknown genetic events that lead towards CRC. Therefore we wanted to improve our understanding of the genetic mechanisms of CRC development.MethodsWe used microarrays to identify novel genes involved in the development of CRC. Real time PCR was used for mRNA expression as well as to search for chromosomal abnormalities within candidate genes. The correlation between the expression obtained by real time PCR and the presence of the KRAS mutation was investigated.ResultsWe detected significant previously undescribed underexpression in CRC for genes SLC26A3, TPM1 and DCN, with a suggested tumour suppressor role. We also describe the correlation between TPM1 and DCN expression and the presence of KRAS mutations in CRC. When searching for chromosomal abnormalities, we found deletion of the TPM1 gene in one case of CRC, but no deletions of DCN and SLC26A3 were found.ConclusionOur study provides further evidence of decreased mRNA expression of three important tumour suppressor genes in cases of CRC, thus implicating them in the development of this type of cancer. Moreover, we found underexpression of the TPM1 gene in a case of CRCs without KRAS mutations, showing that TPM1 might serve as an alternative path of development of CRC. This downregulation could in some cases be mediated by deletion of the TPM1 gene. On the other hand, the correlation of DCN underexpression with the presence of KRAS mutations suggests that DCN expression is affected by the presence of activating KRAS mutations, lowering the amount of the important tumour suppressor protein decorin.

Increased expression of decorin during the regeneration stage of mdx mouse

Satellite cells exist in postnatal muscle tissue and constitute the main source of muscle precursor cells for growth and repair. These cells carry out important roles for skeletal muscle formation postnatally during growth of muscle mass as well as damage-induced regenerative processes. Muscle regeneration supports muscle function in aging and has a role in the functional impairment caused by progressive neuromuscular diseases. Major substances controlling this process are growth factors and extracellular matrix. Myostatin, a member of TGF-beta family, was mainly expressed in muscle tissue. Decorin, a member of the small leucine-rich proteoglycan gene family, is composed of a core protein and a dermatan/chondroitin sulfate chain. Recent studies have shown that decorin enhanced the proliferation and differentiation of myogenic cells by suppressing myostatin activity. Thus, decorin appears to be a new molecule in the myostatin signaling pathway and a promising target for treatment of progressive neuromuscular diseases. Therefore, in this study, we examined the localization of decorin as well as myostatin in a muscular dystrophy model in mdx mice and B10 Scott Snells mice as a control to elucidate the differences between decorin and myostatin messages as well as protein distribution. This study revealed increased expression of decorin protein as well as mRNA at the regenerative stage of mdx mice compared to early stages, while only weak expression of decorin was detected in the control mice. Our study contributes to identifying the relationship between decorin and myostatin as well as the development of a therapeutic strategy for progressive neuromuscular diseases.

Genetic variation in stromal proteins decorin and lumican with breast cancer: investigations in two case-control studies

IntroductionThe stroma is the supportive framework of biologic tissue in the breast, consisting of various proteins such as the proteoglycans, decorin and lumican. Altered expression of decorin and lumican is associated with breast tumors. We hypothesized that genetic variation in the decorin (DCN) and lumican (LUM) genes may contribute to breast cancer.MethodsWe investigated associations of 14 common polymorphisms in the DCN and LUM genes with 798 breast cancer cases and 843 controls from Mayo Clinic, MN, USA. One polymorphism per gene with the strongest risk association in the Mayo Clinic sample was genotyped in 4,470 breast cancer cases and 4,560 controls from East Anglia, England (Studies of Epidemiology and Risk Factors in Cancer Heredity (SEARCH)).ResultsIn the Mayo Clinic sample, six polymorphisms were associated with breast cancer risk (Ptrend ≤ 0.05). The association with LUM rs2268578, evaluated further in SEARCH, was positive, although the odds ratios (OR) were weaker and not statistically significant. ORs were 1.4 (95% confidence interval [CI], 1.1 to 1.8) for heterozygotes and 2.2 (95% CI, 1.1 to 4.3; P2 df = 0.002) for homozygotes in the Mayo Clinic sample, and were 1.1 (95% CI, 0.9 to 1.2) for heterozygotes and 1.4 (95% CI, 1.0 to 2.1; P2 df = 0.13) for homozygotes in the SEARCH sample. In combined analyses, the ORs were 1.1 (95% CI, 1.0 to 1.2) for heterozygotes and 1.6 (95% CI, 1.2 to 2.3; P2 df = 0.005) for homozygotes. Positive associations for this polymorphism were observed for estrogen receptor-positive tumors in both the Mayo Clinic sample (OR for heterozygotes = 1.5, 1.1 to 1.9 and OR for homozygotes = 2.5, 1.2 to 5.3;P2 df = 0.001) and the SEARCH sample (OR for heterozygotes = 1.0, 0.9 to 1.1 and OR for homozygotes = 1.6, 1.0 to 2.5; P2 df = 0.10). In combined analyses, the ORs were 1.1 (95% CI, 0.9 to 1.2) for heterozygotes and 1.9 (95% CI, 1.3 to 2.8; P2 df = 0.001) for homozygotes.ConclusionsAlthough LUM rs2268578 was associated with breast cancer in the Mayo Clinic study, particularly estrogen receptor-positive breast cancer, weaker and modest associations were observed in the SEARCH sample. These modest associations will require larger samples to adequately assess the importance of this polymorphism in breast cancer.

An Antimetastatic Role for Decorin in Breast Cancer

Decorin, a member of the small leucine-rich proteoglycan gene family, down-regulates members of the ErbB receptor tyrosine kinase family and attenuates their signaling, leading to growth inhibition. We investigated the effects of decorin on the growth of ErbB2-overexpressing mammary carcinoma cells in comparison with AG879, an established ErbB2 kinase inhibitor. Cell proliferation and anchorage-independent growth assays showed that decorin was a potent inhibitor of breast cancer cell growth and a pro-apoptotic agent. When decorin and AG879 were used in combination, the inhibitory effect was synergistic in proliferation assays but only additive in both colony formation and apoptosis assays. Active recombinant human decorin protein core, AG879, or a combination of both was administered systemically to mice bearing orthotopic mammary carcinoma xenografts. Primary tumor growth and metabolism were reduced by approximately 50% by both decorin and AG879. However, no synergism was observed in vivo. Decorin specifically targeted the tumor cells and caused a significant reduction of ErbB2 levels in the tumor xenografts. Most importantly, systemic delivery of decorin prevented metastatic spreading to the lungs, as detected by novel species-specific DNA detection and quantitative assays. In contrast, AG879 failed to have any effect. Our data support a role for decorin as a powerful and effective therapeutic agent against breast cancer due to its inhibition of both primary tumor growth and metastatic spreading.

Decorin moieties tethered into PEG networks induce chondrogenesis of human mesenchymal stem cells

A versatile approach to fabricate PEG-peptide copolymer gels was utilized to design niches to promote chondrogenic differentiation of human mesenchymal stem cells (hMSCs). The sequences RGD and KLER were chosen as motifs to modify PEG gels through a thiol-acrylate polymerization. The KLER sequence, a binding site from decorin protein, is known to bind strongly to collagen type II and is responsible for matrix organization, while RGD promotes general survival of encapsulated cells. hMSCs were encapsulated at 2 x 10(6) cells/mL into 10 wt % PEG gels with 1 mM CRGDSG in the presence or absence of 5 mM CKLERG. A scrambled sequence served as a control. The gels were cultured in control and chondrogenic media, containing 5 ng/mL TGFbeta(1) over a 6-week period. Cell/gel constructs were analyzed at various time points for glycosaminoglycan (GAG) content, type II collagen deposition, immunostaining, and gene analysis. After 14 days in chondrogenic cultures, cells in RGDS and KLER functionalized gels produced 2.5 times as much GAG/cell as those in gels containing only RGD. By day 28, hMSCs within the chondrogenic KLER gels produced 27-fold higher hydroxyproline than that of day 0, whereas cells in chondrogenic culture with RGDS alone produced twofold of initial. Immunostained images indicated that col II was more predominant in the KLER-derivatized gels than others, and enhanced chondrogenic differentiation in KLER containing gels was further supported by RT-PCR analysis of type II collagen and aggrecan expression. Collectively, these results demonstrate how incorporation of matrix-binding peptide interacts with hMSCs inducing chondrogenic differentiation and cartilage-specific ECM deposition.

Upregulation and function of GADD45γ in unilateral ureteral obstruction

We performed differential display analysis to determine transcriptional activity in the rat kidney, following unilateral ureteral obstruction and found a 12-fold increase in the expression of Growth Arrest and DNA Damage-45gamma (GADD45gamma), a stress-responsive molecule that interacts with cell-cycle proteins. GADD45gamma was strongly expressed in as little as 6 h following ureteric obstruction in the renal tubules, and was also found in kidney tissue of patients with chronic glomerulonephritis. Adenovirus-mediated expression of GADD45gamma in cultured renal tubular cells activated p38 along with a significant upregulation of C-C and C-X3-C chemokine ligands and fibrosis-related factors such as several matrix metalloproteinases, transforming growth factor-beta1, decorin, and bone morphogenetic protein 2. Silencing of GADD45gamma expression significantly blunted the upregulation of these inflammatory and fibrogenic mediators and monocyte infiltration in the ureteral obstructed rat kidney. Our study shows that GADD45gamma is quickly upregulated in the kidney with an obstructed ureter, enhancing the production of factors regulating the pathogenesis of kidney disease.

Collagens, Proteoglycans, MMP-2, MMP-9 and TIMPs in Human Achilles Tendon Rupture

Tendon integrity depends on the extracellular matrix (ECM) metabolism which is regulated by proteolytic enzymes. However, it is unclear which enzymes play a role in tendon rupture. We studied the ECM of 19 ruptured human Achilles tendons, comparing the composition of specimens harvested close to the rupture with specimens harvested from an apparently healthy area in the same tendon. We compared gene expression of collagen Type I, decorin, and versican including enzymes involved in their metabolism as matrix metalloproteases (MMP-2 and -9) and tissue inhibitory of metalloproteinase (TIMP-1 and -2) using real-time PCR, zymography and FACE analysis. We found greater gene expression of proteoglycan core protein decorin and versican, collagen Type I, MMPs and TIMPs in the tendon rupture. Zymography analysis, reflecting expression of enzymatic activity, confirmed the gene expression data at protein level. Carbohydrate content was greater in the macroscopically healthy area than in the ruptured area. In the ruptured area, we found increased core protein synthesis but without the normal glycosaminoglycan production. The tissue in the area of rupture undergoes marked rearrangement at molecular levels and supports the role of MMPs in the pathology.

Decorin is a secreted protein associated with obesity and type 2 diabetes

To characterize the expression of the small leucine-rich glycoprotein decorin in adipose tissue. Real-time PCR was used to measure decorin gene expression in adipose tissue from normal glucose tolerant (NGT), impaired glucose tolerant and type 2 diabetic (T2D) Psammomys obesus. Adipose tissue was fractionated to determine which cells were responsible for decorin expression. The location of decorin protein expression in adipose tissue was determined using immunohistochemistry. Real-time PCR was used to measure decorin mRNA levels in human adipose tissue from 16 insulin-sensitive, 16 insulin-resistant and 6 T2D human subjects. Circulating plasma decorin concentrations were measured by enzyme-linked immunosorbent assay in 145 NGT and 141 T2D human individuals from a large-scale epidemiological study in Mauritius. Decorin mRNA was found to be highly expressed in adipose tissue, and decorin gene expression was significantly higher in visceral than that in subcutaneous adipose tissue depots in both P. obesus and human subjects (P=0.002 and P=0.001, respectively). Decorin mRNA was predominantly expressed by stromal/vascular cells of adipose tissue, and decorin protein in adipose tissue was primarily detected adjacent to blood vessels. Circulating plasma decorin levels in humans were elevated by 12% in T2D (P=0.049) compared to NGT subjects. There was a significant independent correlation between plasma decorin levels and waist-to-hip ratio (WHR, P=0.024). In male subjects, plasma decorin levels were significantly correlated with WHR (P=0.006), and fasting and 2-h glucose levels in an oral glucose tolerance test (P=0.027 and P=0.001, respectively). Decorin expression in adipose tissue was markedly upregulated in the obese state and may therefore play a role in adipose tissue homeostasis or in pathophysiology associated with obesity.

Tissue Engineering the Aortic Valve Spongiosa Using Matrigel‐Cell‐Scaffold‐Composites (MCSCs)

The middle layer of the aortic valve, termed the spongiosa, consists mainly of glycosaminoglycans (GAGs). Its function is to serve as a shock absorber and resist compression forces between the two outer layers of the valve, and is therefore a necessary component of the bioengineered valve. MCSCs were created by seeding radial artery cells (RACs; 2×106/ml) mixed with endothelial growth media and Matrigel onto small intestinal submucosa, and incubated at 37°C for 0, 1, 2 or 3 weeks. Composites were stained with Alcian Blue for GAGs and immunohistochemistry was used to detect the core protein decorin. Thickness of constructs and cell proliferation were quantified, and gelatin zymography was performed to test for extracellular matrix remodeling. Constructs stayed intact for a minimum of three weeks and stained positively for GAGs and decorin. As culture time increased, MCSC thickness increased. Cell density was stable across all culture times. Zymography revealed the presence of both latent and active matrix metalloproteinase 2. In summary, these composites have shown they are capable of producing GAGs, along with one of their associated core proteins, can lay down new matrix, maintain a constant rate of proliferation, and are likely to be engaging in matrix remodeling. These findings support the use of Matrigel and RACs in our bioengineering efforts. This research is funded by The Heart and Stroke Foundation of Ontario.

HtrA1 Inhibits Mineral Deposition by Osteoblasts: REQUIREMENT FOR THE PROTEASE AND PDZ DOMAINS

HtrA1 is a secreted multidomain protein with serine protease activity. In light of increasing evidence implicating this protein in the regulation of skeletal development and pathology, we investigated the role of HtrA1 in osteoblast mineralization and identified domains essential for this activity. We demonstrate increased HtrA1 expression in differentiating 2T3 osteoblasts prior to the appearance of mineralization. HtrA1 is subsequently down-regulated in fully mineralized cultures. The functional role of HtrA1 in matrix calcification was investigated using three complementary approaches. First, we transfected a full-length HtrA1 expression plasmid into 2T3 cells and showed that overexpression of HtrA1 delayed mineralization, reduced expression of Cbfa1 and collagen type I mRNA, and prevented BMP-2-induced mineralization. Second, knocking down HtrA1 expression using short interfering RNA induced mineral deposition by 2T3 cells. Third, by expressing a series of recombinant HtrA1 proteins, we demonstrated that the protease domain and the PDZ domain are essential for the inhibitory effect of HtrA1 on osteoblast mineralization. Finally, we tested whether HtrA1 cleaves specific matrix proteins that are known to regulate osteoblast differentiation, mineralization, and/or BMP-2 activity. Full-length recombinant HtrA1 cleaved recombinant decorin, fibronectin, and matrix Gla protein. Both the protease domain and the PDZ domain were necessary for the cleavage of matrix Gla protein, whereas the PDZ domain was not required for the cleavage of decorin or fibronectin. Type I collagen was not cleaved by recombinant HtrA1. These results suggest that HtrA1 may regulate matrix calcification via the inhibition of BMP-2 signaling, modulating osteoblast gene expression, and/or via the degradation of specific matrix proteins.

Expression of decorin, a small leucine‐rich proteoglycan, as a prognostic factor in soft tissue tumors

Decorin is a major extracellular matrix protein which has recently become the focus of various cancer studies. However, there have so far been no reports describing the clinicopathological implications of decorin in soft tissue tumors. The aim of this study was to examine whether decorin expression is a prognostic factor in soft tissue tumors. Decorin expression was examined in 85 samples obtained from 77 patients by real-time quantitative PCR and immunohistochemistry. Lower levels of decorin were expressed in liposarcoma and malignant peripheral nerve sheath tumor than in lipoma (<0.01) and neurofibroma (P < 0.05), respectively. An immunohistochemical analysis for spindle-cell sarcomas demonstrated decorin protein to be produced by myofibroblastic cells in the peripheral stromal extracellular spaces. On a Kaplan-Meier analysis, lower levels of decorin were associated with lower disease-free and overall survival rates (P < 0.05) in 31 spindle-cell sarcomas. A multivariate analysis revealed a significant correlation between a reduced decorin expression and a poor disease-free survival (P = 0.04). In all seven patients with recurrent or metastatic lesions, the decorin expression levels were lower in secondary lesions than in primary lesions. A reduced decorin expression was found to be a useful biomarker of aggressiveness in soft tissue tumor.