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At least 955 records · Page 53Linked to original sources
PubMed2005

Plasma levels of matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-1 correlate with disease stage and survival in colorectal cancer patients.

PURPOSE: The matrix metalloproteinases and their inhibitors are known to be involved in the process of tumor invasion and progression. Our objective was to investigate the potential diagnostic and prognostic value of plasma matrix metalloproteinase-2 and -9 and tissue inhibitor of metalloproteinase-1 in colorectal cancer. METHODS: Gelatinase bioactivity and immunoreactivity of pro-matrix metalloproteinase-2 and -9, tissue inhibitor of metalloproteinase-1, and carcinoembryonic antigen were determined simultaneously in preoperative plasma and serum of colorectal cancer patients (n = 94) and in healthy controls (n = 51). RESULTS: Plasma pro-matrix metalloproteinase-2 levels were lower in colorectal cancer patients (P < 0.0001) than in controls, and its gelatinolytic activity revealed an inverse correlation with adverse clinicopathologic parameters, such as lymph node involvement (P = 0.017), stage (0, I, II vs. III, IV; P = 0.012), and the carcinoembryonic antigen level (P = 0.016). Pro-matrix metalloproteinase-9 levels did not differ between patients and controls. Pro-matrix metalloproteinase-2 gelatinolytic activity showed potential value in colorectal cancer diagnosis, identifying patients with 70 percent sensitivity at 95 percent specificity. Pro-matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-1, and carcinoembryonic antigen all showed lower sensitivities. Combining pro-matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-1 measurements increased the sensitivity significantly to 84 percent. With respect to prognosis, tissue inhibitor of metalloproteinase-1 showed value in predicting disease outcome in our patient group, whereas pro-matrix metalloproteinase-2 and -9 did not. The combination of tissue inhibitor of metalloproteinase-1 and carcinoembryonic antigen was better in predicting three-year survival than tissue inhibitor of metalloproteinase-1 alone, but it remains to be determined if the combination would be a better marker for survival than carcinoembryonic antigen alone. CONCLUSIONS: Low pro-matrix metalloproteinase-2 levels and high tissue inhibitor of metalloproteinase-1 levels correlate with parameters of colorectal cancer disease. These correlations may be used in the search for new markers in colorectal cancer diagnosis and prognosis.

Adult↗
PubMed2002

Increased membrane type 1 matrix metalloproteinase expression from adenoma to colon cancer: a possible mechanism of neoplastic progression.

PURPOSE: Membrane type 1 matrix metalloproteinase is a membrane-associated matrix metalloproteinase central to the degradation of basement membrane components via the activation of matrix metalloproteinase-2. Although membrane type 1 matrix metalloproteinase is overexpressed in invasive colon cancer, its expression in colonic polyps and carcinoma in situ has not been defined. In addition, the association of membrane type 1 matrix metalloproteinase expression by a primary tumor and recurrence of colon cancers has not been examined. METHODS: Immunoperoxidase staining was performed on randomly selected specimens containing adenoma (n = 17), carcinoma in situ (n = 9), or metastatic colon carcinoma (n = 8) with mouse monoclonal antibody to human membrane type 1 matrix metalloproteinase. Similar staining was also performed on randomly selected node-negative colon cancers that recurred within five years of resection (n = 17), matched for age, gender, stage, grade, and vascular, lymphatic, and perineural invasion, and node-negative colon cancers that did not recur within five years of resection (n = 17). Staining for membrane type 1 matrix metalloproteinase was graded. Mean scores for the groups were compared by Wilcoxon test. RESULTS: We found a progressive and significant increase in the mean score of membrane type 1 matrix metalloproteinase from normal mucosa to adenoma (P < 0.001), carcinoma in situ (P < 0.006), and invasive cancer (P < 0.009). However, there was no difference in membrane type 1 matrix metalloproteinase expression between the recurrent and nonrecurrent groups of node-negative colon cancer (P = not significant). CONCLUSIONS: These data suggest that membrane type 1 matrix metalloproteinase expression increases with progression from normal mucosa to invasive adenocarcinoma; however, it cannot be used as a prognostic indicator on which adjuvant therapy is based in node-negative colon cancer because of its failure to predict recurrence in this patient group.

Adenoma↗
PubMed1984

The synthesis of subendothelial matrix by bovine aortic endothelial cells in culture.

Bovine aortic endothelial cells cultured on collagenous or plastic substrata continuously synthesize and deposit a subendothelial matrix, independently of whether the cells are in the logarithmic or the stationary phase of growth. This subendothelial matrix contains fibrillar and amorphous elements comparable with those observed in the subendothelium in vivo. Deposition of subendothelial matrix on a collagen gel substratum both started earlier and progressed at approximately double the rate than that on denatured collagen. The relative composition of the subendothelial matrix was assessed by sequential incubation with trypsin, elastase and collagenase (Jones et al., 1979). The subendothelial matrix deposited on collagen gels by early confluent cultures and late post-confluent cultures differed in their enzyme sensitivity. These age-related changes in the enzyme sensitivity of the subendothelial matrix were characteristic for each cloned cell population examined. Comparable variations in the composition of the subendothelial matrix were not observed when the cells were cultured on plastic or gelatin-coated dishes; the subendothelial matrix deposited on these two substrata contained considerably more trypsin-sensitive material and less elastase and collagenase-sensitive material than the matrix deposited on native collagen gels. Age-related changes in the enzyme sensitivity of the subendothelial matrix deposited on collagen gels was found to be a function of the time elapsed since confluence and it was not related to the time elapsed since plating or to the number of cells present.

Animals↗
PubMed2005

Expression of matrix metalloproteinase-3 in the rat cervix during pregnancy and in response to prostaglandin E2.

OBJECTIVE: The purpose of this study was to evaluate the expression of matrix metalloproteinase-3 in the cervix during normal pregnancy and in response to prostaglandin E2 administration to determine how matrix metalloproteinase-3 expression correlates with changes in cervical tensile strength. STUDY DESIGN: We assessed cervical tensile strength at different time points in the rat gestation and after the administration of prostaglandin E2. Tensile strength was determined by the cervical creep method. Both active and latent forms of matrix metalloproteinase-3 protein were assayed by immunoblotting and densitometry. Matrix metalloproteinase-3 messenger RNA expression was determined with a real-time reverse transcriptase-polymerase chain reaction technique. RESULTS: Cervical tensile strength decreased through the second half of gestation, reaching a nadir by day 21, at 24 to 48 hours before parturition. Prostaglandin E2 that was administered on day 20 of gestation decreased cervical tensile strength in animals that were pretreated with indomethacin. Prostaglandin E2 treatment before day 20 of gestation produced no change in cervical tensile strength. Matrix metalloproteinase-3 messenger RNA and active protein expression paralleled the changes in cervical tensile strength during normal gestation. No change in total matrix metalloproteinase-3 protein expression was detected after prostaglandin E2 treatment. CONCLUSION: Matrix metalloproteinase-3 expression parallels changes in cervical tensile strength through pregnancy. Prostaglandin E2 induces the activation of matrix metalloproteinase-3 but does not affect matrix metalloproteinase-3 protein expression, which suggests that matrix metalloproteinase-3 gene transcription is not regulated by prostaglandin E2 but that rather there is another mechanism by which change is induced.

Animals↗
PubMed2005

Fibronectin fragmentation promotes alpha4beta1 integrin-mediated contraction of a fibrin-fibronectin provisional matrix.

In injured tissues, the fibrin-fibronectin (FN) provisional matrix provides a framework for cell adhesion, migration, and repair. Effective repair and remodeling require a proper balance between extracellular matrix (ECM) deposition, contraction, and turnover. We utilized a three-dimensional (3D) fibrin-FN provisional matrix model to determine the contributions of the FN-binding integrin receptors alpha5beta1 and alpha4beta1 to matrix contraction. CHOalpha5 cells expressing alpha5beta1, a receptor for FN's RGD cell-binding domain, were highly contractile, and cells were well spread on a 3D fibrin-FN matrix. In contrast, CHOalpha4 cells expressing the alpha4beta1 receptor for FN's alternatively spliced V region attached less efficiently to FN and were deficient in fibrin-FN matrix contraction. Surprisingly, cell adhesion and matrix contraction by CHOalpha4 cells were dramatically enhanced, to levels equivalent to CHOalpha5 cells, when proteolyzed FN was used in place of intact FN in the fibrin-FN matrix. Similar enhancement was observed when ligand binding by alpha4beta1 integrins was activated by treatment with Mn(++), but not by stimulation of actin organization with LPA. Therefore, alpha4beta1-dependent cell responses to the provisional matrix are modulated by cleavage of matrix components.

Animals↗
PubMed2003

The role of alpha3beta1 integrin in determining the supramolecular organization of laminin-5 in the extracellular matrix of keratinocytes.

Analyses of mice with targeted deletions in the genes for alpha3 and beta1 integrin suggest that the alpha3beta1 integrin heterodimer likely determines the organization of the extracellular matrix within the basement membrane of skin. Here we tested this hypothesis using keratinocytes derived from alpha3 integrin-null mice. We have compared the organizational state of laminin-5, a ligand of alpha3beta1 integrin, in the matrix of wild-type keratinocytes with that of laminin-5 in the matrix of alpha3 integrin-null cells. Laminin-5 distributes diffusely in arc structures in the matrix of wild-type mouse keratinocytes, whereas laminin-5 is organized into linear, spike-like arrays by the alpha3 integrin-null cells. The fact that alpha3 integrin-null cells are deficient in their ability to assemble a proper laminin-5 matrix is also shown by their failure to remodel laminin-5 when plated onto surfaces coated with purified laminin-5 protein. In sharp contrast, wild-type keratinocytes organize exogenously added laminin-5 into discrete ring-like organizations. These findings led us next to assess whether differences in laminin-5 organization in the matrix of the wild-type and alpha3 integrin-null cells impact cell behavior. Our results indicate that alpha3 integrin-null cells are more motile than their wild-type counterparts and leave extensive trails of laminin-5 over the surface on which they move. Moreover, HEK 293 cells migrate significantly more on the laminin-5-rich matrix derived from the alpha3 integrin-null cells than on the wild-type keratinocyte laminin-5 matrix. In addition, alpha3 integrin-null cells show low strength of adhesion to surfaces coated with purified laminin-5 compared to wild-type cells although both the wild type and the alpha3 integrin-null keratinocytes adhere equally strongly to laminin-5 that has been organized into arrays by other epithelial cells. These data suggest: (1) that alpha3beta1 integrin plays an important role in determining the incorporation of laminin-5 into its proper higher-order structure within the extracellular matrix of keratinocytes and (2) that the organizational state of laminin-5 has an influence on laminin-5 matrix function.

Animals↗
PubMed1995

Nuclear matrix isolated from plant cells.

Residual nuclear matrices can be successfully obtained from isolated nuclei of different monocot and dicot plant species using either high ionic or low ionic extraction protocols. The protein composition of isolated nuclear matrices depends on the details of isolation protocols. They are stable and present in all cases, a tripartite organization with a lamina, nucleolar matrix, and internal matrix network, and also maintain some of the basic architectural features of intact nuclei. In situ preparations demonstrate the continuity between the nuclear matrix and the plant cytoskeleton. Two-dimensional separation of isolated plant nuclear matrix proteins reveals a heterogeneous polypeptide composition corresponding rather to a complex multicomponent matrix than to a simple nucleoskeletal structure. Immunological identification of some plant nuclear matrix components such as A and B type lamins, topoisomerase II, and some components of the transcription and splicing machineries, internal intermediate filament proteins, and also specific nucleolar proteins like fibrillarin and nucleolin, which associate to specific matrix domains, establish a model of organization for the plant nuclear matrix similar to that of other eukaryotes. Components of the transcription, processing, and DNA-anchoring complexes are associated with a very stable nucleoskeleton. The plant matrix-attached regions share structural and functional characteristics with those of insects, vertebrates, and yeast, and some of them are active in animal cells. In conclusion, the available data support the view that the plant nuclear matrix is basically similar in animal and plant systems, and has been evolutionarily conserved in eukaryotes.

Base Sequence↗
PubMed2001

Tethered-TGF-beta increases extracellular matrix production of vascular smooth muscle cells.

Biomaterials developed for tissue engineering and wound healing applications need to support robust cell adhesion, yet also need to be replaced by new tissue synthesized by those cells. In order to maintain mechanical integrity of the tissue, the cells must generate sufficient extracellular matrix before the scaffold is degraded. We have previously shown that materials containing cell adhesive ligands to promote or improve cell adhesion can decrease extracellular matrix production (Mann et al., Modification of surfaces with cell adhesion peptides alters extracellular matrix deposition. Biomaterials 1999;20:2281-6). Such decreased matrix production by cells in tissue engineering scaffolds may result in tissue failure. However, we have found that TGF-beta1 can be used in scaffolds to dramatically increase matrix production. Matrix production by vascular smooth muscle cells grown on adhesive ligand-modified glass surfaces and in PEG hydrogels containing covalently bound adhesive ligands was increased in the presence of 0.04 pmol/ml (1 ng/ml) TGF-beta1. TGF-beta1 can counteract the effect of these adhesive ligands on matrix production; matrix production could be increased even above that observed in the absence of adhesive peptides. Further, TGF-beta1 covalently immobilized to PEG retained its ability to increase matrix production. Tethering TGF-beta1 to the polymer scaffold resulted in a significant increase in matrix production over the same amount of soluble TGF-beta1.

Animals↗
PubMed1997

Photodynamic therapy inactivates extracellular matrix-basic fibroblast growth factor: insights to its effect on the vascular wall.

PURPOSE: Photodynamic therapy (PDT), the light activation of photosensitizer dyes for the production of oxygen and other free radical moieties without the generation of heat, has been shown to inhibit the development of experimentally induced intimal hyperplasia. The host response to PDT, a form of vascular injury that results in complete vascular wall cell eradication, is devoid of inflammation and proliferation and promotes favorable vascular wall healing. These effects do not result in intimal hyperplasia and are suggestive of PDT-induced changes in the extracellular matrix (ECM). As a model to better understand the biologic consequences of PDT on the vascular wall matrix proteins, the effect of PDT was studied on the powerful matrix-resident mitogen basic fibroblast factor (bFGF) in vitro. METHODS: PDT (5 to 200 J/cm2, 100 mW/cm2, 675 nm) was used with the photosensitizer chloroaluminum sulfonated phthalocyanine (5 micrograms/ml) to inactivate bFGF in vitro while 100 J/cm2 of irradiation was administered 24 hours after 5 mg/ml of the photosensitizer was used in vivo. PDT was used on bFGF in solution and on endothelial cell-derived ECM. Enzyme-linked immunosorbent assay was used to quantitate bFGF in solution after PDT treatment or after extraction from the ECM by collagenase and heparin. Functional activity of matrix-associated bFGF was assessed by smooth muscle cell mitogenesis by 3H-thymidine incorporation. To demonstrate the in vivo relevance of these observations, immunohistochemical analysis of PDT-treated rat carotid arteries was undertaken. RESULTS: PDT eliminated detectable levels of bFGF in solution. PDT of ECM significantly reduced matrix-bound bFGF (1.0 +/- 0.6 vs 27.5 +/- 1.3 pg/ml; p < 0.0001). This reduction in bFGF after PDT of the ECM was associated with a decrease in vascular smooth muscle cell mitogenesis (52.4% +/- 4.6%; p < 0.0001) when plated on PDT-treated matrix compared with nontreated matrix. Quantitative replenishment of exogenous bFGF to PDT-treated matrix restored proliferation to baseline levels. PDT of rat carotid arteries demonstrated a loss of bFGF staining compared with control nontreated arteries. CONCLUSIONS: PDT inactivation of matrix-resident bFGF and possibly other bioactive molecules can provide a mechanism by which PDT suppresses smooth muscle cell proliferation in the vessel wall. This free radical-mediated alteration of matrix may contribute to favorable vascular healing when PDT is used for the inhibition of injury-induced intimal hyperplasia.

Animals↗
PubMed2002

A survey of the use of matrix bands and their decontamination in general dental practice.

AIMS: The aims of this study were to determine the pattern of use and re-use of matrix bands in general practice in Scotland, to demonstrate which type of matrix band is most commonly used and to examine infection control measures of relevance to the safe use and re-use of matrix bands. MATERIALS AND METHODS SUBJECTS: 621 of Scotland's 1,849 general dental practitioners were randomly selected. DATA COLLECTION: A 19-item self-reported questionnaire was mailed in June 1999 with a follow-up mailing sent in August 1999. ANALYSIS: Data analysis involved descriptive statistics and cross-tabulation. Where appropriate, differences between categories were tested for significance by a Chi-square test. RESULTS: A total of 479 questionnaires were returned, representing a response rate of 77%. Reported compliance with routine glove wearing was high (91%). Most dentists (92%) provided training on instrument cleaning and sterilisation for their dental nurses. Ultrasonic baths were used by 59% of practitioners; the remainder soaked or manually scrubbed instruments to remove debris before autoclaving. The Siqveland matrix was the matrix of choice for 96% of respondents. 7% provided a new matrix band for each patient. Most (64%) changed bands only when they were bent or damaged; 29% changed them daily or weekly. Deterrents to use of a new band for each patient were cost (39%) and time (52%). A total of 54% of respondents considered matrix band replacement unnecessary between patients. CONCLUSIONS: The Siqveland matrix band is the most popular among the study group of dental practitioners. Re-use of matrix bands is common. Guidelines for the safe re-use of matrix bands are required.

Attitude of Health Personnel↗
PubMed2000

Wild-type p53 gene transfer inhibits invasion and reduces matrix metalloproteinase-2 levels in p53-mutated human melanoma cells.

The tumor suppressor gene p53 has inhibitory effects on cell growth and angiogenesis and induces apoptosis when overexpressed in melanoma and in a variety of tumor cells by adenovirus-mediated gene transfer. The invasive ability of tumor cells, facilitating local infiltration and metastasis, is related to matrix metalloproteinase levels. In melanoma, matrix metalloproteinase-2 and matrix metalloproteinase-9 have a prominent role in this process. The aim of this study was to evaluate whether wild-type p53 overexpression, obtained by a recombinant adenovirus vector (AdCMV.p53), affects cell invasiveness through modulation of matrix metalloproteinase-2 and matrix metalloproteinase-9. Two human melanoma cell lines were used in this study: the SK-MEL-110, carrying a mutated p53 gene, and the SK-MEL-147, carrying the wild-type p53 gene. SK-MEL-110 cells infected with AdCMV.p53 exhibited decreased invasion capability from day 1 after infection, compared with cells not infected or infected with the control vector AdCMV.Null. This reduced invasiveness was associated with decreased matrix metalloproteinase-2 levels in conditioned media whereas no changes were detected in matrix metalloproteinase-9 secreted levels. No modulation in matrix metalloproteinase-2 mRNA levels was detectable, however, after wild-type p53 gene transfer. Furthermore, protein expression of secreted tissue inhibitor of metalloproteinase-2 was not altered by AdCMV.p53 treatment. In contrast, in SK-MEL-147 cells, AdCMV.p53 did not affect cell invasiveness and levels of secreted matrix metalloproteinase-2. Gene transfer of wild-type p53 inhibited proliferation of both cell lines, showing that also SK-MEL-147 cells respond to wild-type p53 overexpression. This novel mechanism of action of wild-type p53 gene transfer may contribute to its antitumor effect by downregulating cell invasion and matrix metalloproteinase-2 secreted levels in mutated p53 human melanoma cell lines.

Adenoviridae↗
PubMedDate not supplied

Epidermal growth factor induces acute matrix contraction and subsequent calpain-modulated relaxation.

During wound healing, dermal fibroblasts switch from a migratory, repopulating phenotype to a contractile, matrix-reassembling phenotype. The mechanisms controlling this switch are unknown. A possible explanation is suggested by the finding that chemokines that appear late in wound repair prevent growth factor-induced cell-substratum de-adhesion by blocking calpain activation. In this study, we tested the specific hypothesis that fibroblast contraction of the matrix is promoted by a pro-repair growth factor, epidermal growth factor, and is modulated by calpain-mediated release of adhesions. We employed an isometric force transduction system designed to measure the contraction of a collagen matrix under tension by a population of NR6 fibroblasts transfected with the human epidermal growth factor receptor. By maintaining a fixed level of strain, we could monitor both the initial contraction and subsequent relaxation of the matrix. Epidermal growth factor stimulated a transient, dose-dependent increase in matrix contraction that peaked within 60 minutes and then decayed over the ensuing 3 to 6 hours. Calpain inhibitor I (ALLN) prevented epidermal growth factor-stimulated cell de-adhesion and resulted in a significantly slower decay of matrix contraction, with only a slight decrease of the peak magnitude of contraction. The mitogen-activated protein kinase kinase-1-selective inhibitor PD 98059 that blocks signaling through the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway, required for epidermal growth factor receptor-mediated activation of calpain and de-adhesion, does not significantly affect the magnitude of matrix contraction within minutes of epidermal growth factor addition, but slows the decay similarly to calpain inhibition. Epidermal growth factor receptor signaling thus stimulates the complementary mechanisms of intracellular contractile force generation and calpain-mediated de-adhesion, which are known to coordinately facilitate cell migration. These findings suggest that calpain can act as a functional switch for transmission of intracellular contractile force to the surrounding matrix, with calpain-mediated de-adhesion reducing this transmission and corresponding matrix contraction. Countervailing processes that down-regulate calpain activation can, accordingly, direct the transition of cell function from locomotion to matrix contraction.

Animals↗
PubMed1999

The nuclear matrix prepared by amine modification.

The nucleus is spatially ordered by attachments to a nonchromatin nuclear structure, the nuclear matrix. The nuclear matrix and chromatin are intimately connected and integrated structures, and so a major technical challenge in nuclear matrix research has been to remove chromatin while retaining a native nuclear matrix. Most methods for removing chromatin require first a nuclease digestion and then a salt extraction to remove cut chromatin. We have hypothesized that cut chromatin is held in place by charge interactions involving nucleosomal amino groups. We have tested this hypothesis by chemically modifying amino groups after nuclease digestion. By using this protocol, chromatin could be effectively removed at physiological ionic strength. We compared the ultrastructure and composition of this nuclear matrix preparation with the traditional high-salt nuclear matrix and with the third nuclear matrix preparation that we have developed from which chromatin is removed after extensive crosslinking. All three matrix preparations reveal internal nuclear matrix structures that are built on a network of branched filaments of about 10 nm diameter. That such different chromatin-removal protocols reveal similar principles of nuclear matrix construction increases our confidence that we are observing important architectural elements of the native structure in the living cell.

Amines↗
PubMed1984

Extracellular matrix-specific induction of elastogenic differentiation and maintenance of phenotypic stability in bovine ligament fibroblasts.

We studied the process of elastogenic differentiation in the bovine ligamentum nuchae to assess the mechanisms that regulate elastin gene expression during development. Undifferentiated ( nonelastin -producing) ligament cells from early gestation animals initiate elastin synthesis when grown on an extracellular matrix (ECM) substratum prepared from late gestation ligamentum nuchae. ECM from ligaments of fetal calves younger than the time when elastin production occurs spontaneously in situ (i.e., beginning the last developmental trimester at approximately 180 d of gestation) does not stimulate elastin production in undifferentiated cells. Matrix-induced differentiation requires direct cell matrix interaction, is dependent upon cell proliferation after cell-matrix contact, and can be blocked selectively by incorporation of bromodeoxyuridine into the DNA of undifferentiated cells before (but not after) contact with inducing matrix. Quantitative analysis of elastin synthesis in young cells after matrix-induced differentiation indicates that the entire cell population is competent to respond to the matrix inducer, and continued synthesis of elastin after young cells are removed from the ECM substratum indicates that the phenotypic transition to elastin synthesis is stable and heritable. Although ligament cells do not require continuous contact with ECM to express the elastin phenotype, elastin synthesis is increased substantially when elastin-producing cells are grown on ligament matrix, suggesting that elastogenic differentiation is stabilized by ECM. The matrix substratum was also found to alter the distribution of tropoelastin between the medium and matrix cell layer. When grown on tissue culture plastic, ligament cells secrete greater than 80% of newly synthesized tropoelastin into the culture medium. When cultured on ECM, however, 50-70% of the newly synthesized tropoelastin remains associated with the cell layer and is cross-linked to form insoluble elastin as shown by the incorporation of radiolabeled lysine into desmosine.

Age Factors↗
PubMed2005

Mechanisms of action of demineralized bone matrix in the repair of cortical bone defects.

Demineralized bone matrix commonly is used to enhance and to facilitate bone grafting after skeletal injury or disease; however, the biologic bases for its bone-inducing abilities remain obscure. We have taken advantage of a mouse model of cortical bone defect healing to elucidate its mechanisms of action in vivo. Demineralized bone matrix combined with hyaluronan improved skeletal healing by inducing early deposition of an osteoid matrix. Demineralized bone matrix combined with hyaluronan might accelerate bone formation because it serves as a scaffold on which osteoprogenitor cells attach. We tested this possibility by comparing demineralized bone matrix combined with hyaluronan with heat-inactivated demineralized bone matrix combined with hyaluronan and found that the intact material was superior in terms of its ability to stimulate new bone formation. We also compared the bone inducing capacity of demineralized bone matrix combined with hyaluronan with a synthetic collagen sponge and found that not only the synthetic collagen scaffold delayed bone healing but also impaired bony bridging at later stages of repair. Another important property of demineralized bone matrix combined with hyaluronan was its ability to become actively degraded by osteoclasts during healing. Therefore, demineralized bone matrix combined with hyaluronan may not only attract osteoblasts and stimulate their differentiation, but also induce bone matrix resorption, which is a critically important regulator of bone formation and mineralization.

Animals↗
PubMed2004

Bradykinin decreases plasminogen activator inhibitor-1 expression and facilitates matrix degradation in the renal tubulointerstitium under angiotensin-converting enzyme blockade.

A number of experimental and clinical investigations support the notion that angiotensin-converting enzyme inhibitor (ACEi) and angiotensin II type 1 receptor blocker (ARB) compounds attenuate renal fibrosis. Fibrosis can be attenuated by either suppressing matrix formation or facilitating matrix degradation. In this study, drugs of ACEi and ARB classes were tested for their ability to facilitate matrix degradation in the kidney. A murine model system in which cyclosporin A (CsA) treatment for a specified period caused interstitial matrix deposition in the kidney was used. CsA was then discontinued, and experimental procedures were initiated to investigate matrix degradation. Benazepril, an ACEi, facilitated matrix degradation via the bradykinin (BK) B2 receptor on tubular epithelial cells in the kidney, whereas CGP-48933, an ARB, did not. In this murine model of CsA nephropathy under ACE blockade, plasminogen activator inhibitor-1 (PAI-1) expression was decreased in tubular epithelial cells, possibly leading to conversion of plasminogen to plasmin by plasminogen activator and subsequent activation of matrix metalloproteinases. These findings were confirmed in this study by measurements of plasmin activity, collagenolytic activity, and matrix metalloproteinase activities in the kidneys. In tubular epithelial cells stimulated in vitro, BK suppressed PAI-1 gene expression. All of these results suggest that ACEi can decrease PAI-1 expression via BK, thereby facilitating matrix degradation via activation of degradative enzymes to reduce interstitial matrix deposition.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Extracellular matrix incorporation of normal and NEM-alkylated fibronectin: liver and spleen deposition.

The incorporation of plasma fibronectin (pFn) into the extracellular matrix (ECM) is believed to influence tissue integrity, wound repair, and vascular permeability. In vitro, matrix assembly of Fn requires the binding of soluble Fn to cell-associated matrix assembly sites. Alkylation of human pFn (HFn) with N-ethylmaleimide (NEM) prevents the initial binding of Fn to matrix assembly sites as well as its in vitro incorporation into the ECM as reflected by detergent-insoluble 125I-labeled Fn (pool II Fn). We determined the kinetics of Fn matrix incorporation in tissue and whether NEM treatment of rat pFn (NEM-RFn) would limit its in vivo incorporation into ECM by analysis of pool I [deoxycholate (DOC) soluble] and pool II (DOC insoluble) 125I-Fn in tissues after its intravenous injection into rats. After intravenous injection, tissue incorporation of normal rat 125I-pFn was especially intense in liver and spleen, in agreement with the large amount of endogenous Fn detected in the matrices of these organs. Tissue deposition of plasma-derived 125I-RFn in liver and spleen peaked by 4 h, with significant (P < 0.01) loss over 24 h, indicating turnover of matrix Fn. Tissue localization of normal 125I-RFn in liver, lung, spleen, heart, and intestine was greater (P < 0.05) than 125I-NEM-RFn at 4 h. Normal HFn, but not NEM-HFn, was incorporated into tissues and colocalized with endogenous Fn in the matrix. To identify the cells mediating the intense incorporation of pFn into liver ECM, we compared matrix assembly of 125I-HFn by cultured fibroblasts, hepatocytes, and hepatic Kupffer cells. With fibroblasts, 125I-HFn in pool I reached steady state by 3 h, whereas 125I-HFn in pool II exceeded that in pool I by 6 h and continued to increase over 24 h. With hepatocytes, pool I 125I-HFn reached steady state by 1 h, and a progressive increase (P < 0.05) of 125I-HFn in pool II was observed over 24 h. Kupffer cells were not able to incorporate significant amounts of 125I-HFn into matrix. NEM-HFn displayed limited incorporation into ECM by both fibroblast and hepatocyte cultures. These novel observations suggest that the interaction of soluble pFn with matrix assembly sites is necessary to its in vivo incorporation into the ECM.

Alkylation↗
PubMed1997

Subendothelial retention of lipoprotein (a). Evidence that reduced heparan sulfate promotes lipoprotein binding to subendothelial matrix.

Vessel wall subendothelial extracellular matrix, a dense mesh formed of collagens, fibronectin, laminin, and proteoglycans, has important roles in lipid and lipoprotein retention and cell adhesion. In atherosclerosis, vessel wall heparan sulfate proteoglycans (HSPG) are decreased and we therefore tested whether selective loss of HSPG affects lipoprotein retention. A matrix synthesized by aortic endothelial cells and a commercially available matrix (Matrigel; , Rutherford, NJ) were used. Treatment of matrix with heparinase/heparitinase (1 U/ml each) increased LDL binding by approximately 1.5-fold. Binding of lipoprotein (a) [Lp(a)] to both subendothelial matrix and Matrigel(R) increased 2-10-fold when the HSPG were removed by heparinase treatment. Incubation of endothelial cells with oxidized LDL (OxLDL) or lysolecithin resulted in decreased matrix proteoglycans and increased Lp(a) retention by matrix. The effect of OxLDL or lysolecithin on endothelial PG was abolished in the presence of HDL. The decrease in matrix HSPG was associated with production of a heparanase-like activity by OxLDL-stimulated endothelial cells. To test whether removal of HSPG exposes fibronectin, a candidate Lp(a) binding protein in the matrix, antifibronectin antibodies were used. The increased Lp(a) binding after HSPG removal was inhibited 60% by antifibronectin antibodies. Similarly, the increased Lp(a) binding to matrix from OxLDL-treated endothelial cells was inhibited by antifibronectin antibodies. We hypothesize that atherogenic lipoproteins stimulate endothelial cell production of heparanase. This enzyme reduces HSPG which in turn promotes Lp(a) retention.

Animals↗