Decorin and biglycan retain LDL in disease-prone valvular and aortic subendothelial intimal matrix

Objective

Subendothelial LDL retention by intimal matrix proteoglycans is an initial step in atherosclerosis and calcific aortic valve disease. Herein, we identify decorin and biglycan as the proteoglycans that preferentially retain LDL in intimal matrix at disease-prone sites in normal valve and vessel wall.

Methods

The porcine aortic valve and renal artery ostial diverter, initiation sites of calcific valve disease and renal atherosclerosis, respectively, from normal non-diseased animals were used as models in these studies.

Results

Fluorescent human LDL was selectively retained on the lesion-prone collagen/proteoglycan-enriched aortic surface of the valve, where the elastic lamina is depleted, as previously observed in lesion-prone sites in the renal ostium. iTRAQ mass spectrometry of valve and diverter protein extracts identified decorin and biglycan as the major subendothelial intimal matrix proteoglycans electrostatically retained on human LDL affinity columns. Decorin levels correlated with LDL binding in lesion-prone sites in both tissues. Collagen binding to LDL was shown to be proteoglycan-mediated. All known basement membrane proteoglycans bound LDL suggesting they may modulate LDL uptake into the subendothelial matrix. The association of purified decorin with human LDL in an in vitro microassay was blocked by serum albumin and heparin suggesting anti-atherogenic roles for these proteins in vivo.

Conclusions

LDL electrostatic interactions with decorin and biglycan in the valve leaflets and vascular wall is a major source of LDL retention. The complementary electrostatic sites on LDL or these proteoglycans may provide a novel therapeutic target for preventing one of the earliest events in these cardiovascular diseases.     

Biglycan expression in current cigarette smokers: A possible link between active smoking and atherogenesis

Objective: Cigarette smokers present early signs of vascular damage and systemic inflammation. Biglycan (BGN), an ubiquitous component of extracellular matrix orchestrating several physiological functions, has recently been indicated as a major source of low-density lipoprotein retention in the normal arterial intima-media layer. We evaluated whether BGN-mRNA expression was enhanced in peripheral monocytes of smokers with no additional cardiovascular risk factors (CVRFs), and if it was associated with altered carotid arterial stiffness (AS) or intima media thickness (cIMT). We also evaluated plasma markers of systemic and vascular inflammation, and correlation with BGN-mRNA. Methods: Two-hundred-fifty-one young smokers were enrolled, with no additional CVRFs, and 60 controls. Plasma lipids, fibrinogen, C-reactive protein (CRP), interleukin-6 (IL-6), AS and cIMT were assessed. A smoke exposure index (SEIx) was calculated. Results: Fibrinogen, CRP, AS indices, cIMT, and BGN-mRNA were higher in smokers compared to controls; HDL-C levels were lower, no difference was detected in IL-6 levels. After stratification of smokers in quartiles based on SEIx values, smokers in the highest quartiles presented highest fibrinogen, CRP, AS, cIMT, BGN, and also IL-6 values, and lowest HDL-C. Conclusion: BGN-mRNA was enhanced in young smokers, compared to controls, and appears associated to a proatherogenic profile, characterized by increased fibrinogen, CRP, and IL-6, lower HDL-C, altered AS and cIMT values, particularly in those with higher SEIx: the more cigarettes smoked over years, the more marked the alterations. Although we cannot state whether BGN have a direct causal role in inducing, maintaining and developing vascular damage, including intima-media wall thickening and arterial stiffening, our data could suggest that it may represent a link between proatherogenic status induced by cigarette smoking, and the development and progression of vascular damage.     

Literature Review on the Clinical Relationship between Ulcerative Jejunoileitis,Coeliac Disease,and Enteropathy-associated T-Cell Lymphoma

Background: The small interstitial proteoglycans decorin and biglycan have been shown to interact with various extracellular matrix molecules and with transforming growth factor-β. These interactions are proposed to be important for tissue repair, as the former interactions may affect the diameter and spacing of collagen fibrils, and the latter interaction the proliferation and differentiation of cells embedded in the matrix. The aim of this study is to localize these proteoglycans in the stomach and to investigate their suitability as potential markers of extracellular matrix activity in gastric lesions. Methods: Immunohis-tochemical techniques and in situ hybridization were used to study the phenotypic expression of these two proteoglycans in routinely processed specimens of human stomach tissue from 8 patients with gastric ulcer and 10 healthy control persons. Results: In normal gastric tissue, immunostaining for both proteoglycans was found in the interstitium, with a more pronounced staining in the pylorus region than in the corpus area. In addition, biglycan showed a strong staining of parietal cells. In specimens of healing gastric ulcers a larger deposition of decorin throughout scar tissue could be shown, and a higher expression of decorin was also found by in situ hybridization. Biglycan was only found at the edges of the lesions. Conclusion: This study shows for the first time the presence of decorin and biglycan in human gastric mucosa. We also showed that these proteoglycans may be involved in the gastric ulcer healing processes.     

Biglycan及VEGF对结肠癌细胞增殖、凋亡能力的影响及分子机制

[目的]观察Biglycan及VEGF对结肠癌细胞系HCTll6增殖、凋亡的影响并探讨其可能机制。[方法]向转染Biglycan的细胞系HCTll6中转染VEGFsiRNA．设对照组（Mock）、空载和干扰对照组（Vector＋siRNA-NC）、BiglycancDNA和干扰对照组（Biglycan＋siRNA-NC）及BiglycancDNA和VEGF干扰组fBiglycan＋siRNA-VEGF）。Western Blot检测Biglycan、VEGF及Ki67、PCNA、P21的表达：MTT检测细胞增殖情况：流式细胞术检测细胞凋亡及周期。[结果]过表达Biglycan后,Ki67、PCNA和VEGF显著上调,P21显著下调。干扰VEGF后,上述3种周期蛋白的表达正好相反;Biglycan上调后,细胞增殖能力显著提高,下调VEGF后增殖能力又显著降低（P〈0．05）;Biglycan过表达后S期细胞总数（44.39％±1.80％）较Mock组（31．41％±1．81％）和Vector＋siRNA．NC组（32．56％±1．07％）显著提高fP〈0．01）,凋亡率（0．12％±O．01％）较Mock组（1．75％±0．17％）和Veetor＋siRNA-NC组（1．83％±0．16％）显著下降（P〈0．01）;下调VEGF后S期细胞（20．76％±1．23％）显著降低（P〈0．01）,凋亡率（8．30％±0．71％）显著上升（P〈0．01）。[结论]Biglycan通过促进VEGF的表达来促进结肠癌细胞的增殖并抑制其凋亡。     

Effects of Bone CS-Proteoglycans, DS-Decorin, and DS-Biglycan on Hydroxyapatite Formation in a Gelatin Gel

The small leucine-rich bone proteoglycans, biglycan and decorin, can be purified by chromatography on hydroxyapatite columns, demonstrating their potential affinities for bone apatite. To determine their effects on in vitro apatite formation and growth, a mixture of the chondroitin-sulfate (CS) bone proteoglycans, or purified fractions of the dermatan sulfate (DS) containing proteoglycans, DS-decorin and DS-biglycan obtained from skin and articular cartilage, respectively, were analyzed in a gelatin gel diffusion system in which apatite formation occurs in the absence of proteins in a 3.5 day period. Low concentrations of the bone CS-proteoglycan mixture and low DS-biglycan concentrations (5–25 μg/ml) increased apatite formation relative to proteoglycan-free controls at 3.5 days. The CS-proteoglycan mixture was less effective at 50 μg/ml than at 10 μg/ml. DS-biglycan was similarly most effective at 5–25 μg/ml. At 5 days, when apatite growth and proliferation were assessed, 10 and 50 μg/ml of both CS-bone proteoglycan and DS-biglycan increased mineral yields. DS-decorin, in contrast, had no significant effect on mineral accumulation at any of these concentrations. In seeded growth experiments, 1 and 10 μg/ml CS-proteoglycan and 10 and 50 μg/ml DS-biglycan were significant effective inhibitors of mineral accretion, whereas DS-decorin showed no tendency to inhibit seeded growth. Using molar extinction coefficients to determine concentrations, the binding of DS-biglycan and DS-decorin to apatite (specific surface 54 m²/g) was determined using a Langmuir adsorption isotherm model. DS-biglycan had a greater affinity for apatite than DS-decorin (0.285 ml/μmol versus 0.0098 ml/μmol). DS-biglycan binding was more specific with fewer binding sites (3.5 μmol/m² compared with 18.2 μmol/m² for DS-decorin). Data suggest that of the small proteoglycans, biglycan may play a more significant role than decorin in the regulation of mineralization. Received: 10 June 1996 / Accepted: 25 April 1997     

Immunohistochemical Identification of Decorin and Biglycan in Human Dentin: A Correlative Field Emission Scanning Electron Microscopy/Transmission Electron Microscopy Study

Decorin and biglycan, two small leucine-rich proteoglycans, have been proposed to play important roles in matrix-mediated formation of mineralized tissues, and their three-dimensional arrangement in human dentin is still not completely understood. The aim of this study was to immunohistochemically analyze the distribution of decorin and biglycan in human predentin/dentin organic matrix under a high-resolution field emission in-lens scanning electron microscope (FEI-SEM) and a transmission electron microscope (TEM). Tooth dentin specimens were submitted to either a preembedding or a postembedding immunolabeling technique using primary antibodies antidecorin and antibiglycan and gold-conjugated secondary antibodies. Correlative FEI-SEM/TEM observations showed that the two antibodies yielded a similar labeling pattern over the processes of odontoblasts and the predentin. Decorin and biglycan were mainly associated with the collagen fibers within the predentin layer, revealing a moderate immunoreaction that was significantly higher compared to the one observed on dentin. Thus, a generally weak labeling for decorin was found in dentin, which, however, was significantly higher on odontoblast processes within dentinal tubules than in intertubular dentin. On the other hand, biglycan immunolocalization on dentin revealed few gold particles rather uniformly distributed, without showing significant differences between tubular and intertubular regions. In conclusion, this study reveals distinct distribution patterns of decorin and biglycan and their relation with collagen. Decorin’s and biglycan’s precise roles within prematrix and mineralized matrix in human teeth should be further clarified.     

Biglycan及FAK信号通路对结肠癌细胞增殖能力的影响及分子机制

目的 研究Biglycan及FAK信号通路对结肠癌细胞增殖的调控作用及其分子机制。方法 构建Biglycan过表达的人结肠癌HCT116细胞并采用FAK抑制剂处理。分为5组:正常对照组、空载体对照组、空载体抑制剂处理组、Biglycan过表达组和Biglycan过表达抑制剂处理组,处理时间为24h。通过Western blot及MTT检测的方法,观察各组HCT116细胞的增殖能力以及FAK、p-FAK、PCNA、p53的表达情况。结果 过表达Biglycan能够显著促进HCT116细胞的增殖以及FAK的磷酸化(P＜0.01),并导致PCNA表达水平的显著升高和p53表达水平的显著抑制(P＜0.01);而FAK抑制剂PF-562271作用能够明显抑制细胞的增殖能力,Biglycan对p-FAK、PCNA、p53蛋白表达水平的调控被抑制(P＜0.01)。结论 Biglycan通过促进FAK信号通路的活化调控结肠癌细胞的增殖。     

Biglycan deficiency increases osteoclast differentiation and activity due to defective osteoblasts

Bone mass is maintained by a fine balance between bone formation by osteoblasts and bone resorption by osteoclasts. Although osteoblasts and osteoclasts have different developmental origins, it is generally believed that the differentiation, function, and survival of osteoclasts are regulated by osteogenic cells. We have previously shown that the extracellular matrix protein, biglycan (Bgn), plays an important role in the differentiation of osteoblast precursors. In this paper, we showed that Bgn is involved in regulating osteoclast differentiation through its effect on osteoblasts and their precursors using both in vivo and in vitro experiments. The in vivo osteolysis experiment showed that LPS (lipopolisaccharide)-induced osteolysis occurred more rapidly and extensively in bgn deficient mice compared to wild type (WT) mice. To further understand the mechanism of action, we determined the effects of Bgn on 1, 25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃)-induced osteoclast differentiation and bone resorption in an co-culture of calvariae-derived pre-osteoblasts and osteoclast precursors derived from spleen or bone marrow. Time course and dose response experiments showed that tartrate-resistant acid phosphatase-positive multinuclear cells appeared earlier and more extensively in the co-cultures containing calvarial cells from bgn deficient mice than WT mice, regardless of the genotype of osteoclast precursors. The osteoblast abnormality that stimulated osteoclast formation appeared to be independent of the differential production of soluble RANKL and OPG and, instead, due to a decrease in osteoblast maturation accompanied by increase in osteoblastic proliferation. In addition to the imbalance between differentiation and proliferation, there was a differential decrease in secretory leukocyte protease inhibitor (slpi) in bgn deficient osteoblasts treated with 1,25-(OH)₂D₃. These findings point to a novel molecular factor made by osteoblasts that could potentially be involved in LPS-induced osteolysis.     

Biglycan在牙周损伤愈合中的免疫化学定位和表达

目的：研究biglycan在牙周组织损伤愈合过程中的免疫化学定位。方法：损伤成年鼠磨牙周围的牙周组织，跟踪28d，对biglycan和Ⅰ型、Ⅲ型胶原在愈合过程中的免疫组织化学分布进行分析。结果：biglycan在结缔组织中的免疫组织化学分布与Ⅰ型胶原相似。在牙周损伤愈合早期，biglycan在损伤区炎性细胞和移行的牙龈上皮细胞有强烈表达。愈合中期，biglycan广泛表达于肉芽组织成纤维细胞及其基质。愈合晚期，biglycan在新骨成骨细胞中表达明显。结论：biglycan在牙周组织损伤区中的细胞内特征性表达，预示其在牙周损伤愈合过程中起着不可忽视的作用。