MMP-9 regulates both positively and negatively collagen gel contraction - A nonproteolytic function of MMP-9

peer reviewedaudience: researcher, professionalObjective: Constrictive remodeling accounts for lumen loss in postangioplasty restenosis. Matrix metalloproteinase-9 (MMP-9) has been shown to prevent constrictive remodeling in vivo. To investigate potential mechanisms for this observation, we investigated the role of MMP-9 in smooth muscle cell (SMC)-mediated collagen gel contraction, an in vitro model of constrictive remodeling. Methods: Fischer rat SMCs were stably transfected with a construct-expressing rat-MMP-9 under the control of a tetracycline (Tet)-off promoter. SMCs were seeded in type 1 collagen gels (2.4 mg/ml) in the presence or not of tetracycline (1 mu g/ml), and gel contraction was defined as the percentage of retraction of the collagen gel. The depletion of MMP-9 was obtained by using siRNA targeting MMP-9 mRNA or a blocking antibody. Results: Gel contraction was significantly reduced at all times when MMP-9 was overexpressed (Tet-) as compared with the control condition (Tet+). However, MMP-9 depletion of control (Tet+) SMCS (using siRNA or antibody) also inhibited gel contraction. To resolve the apparent discrepancy and determine if MMP-9 exerts a dose-dependent biphasic effect on gel contraction, conditioned medium and purified rat-MMP-9 were prepared. Gel contraction was significantly increased by addition of 0.8 mg/ml of MMP-9, while high concentrations of MMP-9 (>= 100 mg/ml) inhibited contraction. The addition of BB94 and TIMP-1 did not alter the inhibitory or stimulatory effect of MMP-9. Conclusions: Our data Suggest that MMP-9, independent of its proteolytic function, has a biphasic effect on SMC-mediated collagen gel contraction. Understanding the different roles of MMP-9 Should allow the development of better therapeutic strategies for restenotic vascular disease. (c) 2004 European Society of Cardiology. Published by Elsevier B.V. All rights reserved

The Sloan Digital Sky Survey Quasar Catalog III. Third Data Release

We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than M_i = -22 (in a cosmology with H_0 = 70 km/s/Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7), have at least one emission line with FWHM larger than 1000 km/s or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is 4188 sq. deg. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than four, of which 17 are at redshifts greater than five. For each object the catalog presents positions accurate to better than 0.2 arcsec. rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800--9200A at a spectral resolution about 2000; the spectra can be retrieved from the public database using the information provided in the catalog. A total of 44,221 objects in the catalog were discovered by the SDSS; 28,400 of the SDSS discoveries are reported here for the first time.Comment: 41 pages, 7 figures, Accepted for publication in A

Heparin inhibits thrombin-induced mitogen-activated protein kinase signaling in arterial smooth muscle cells

AbstractPurpose: Smooth muscle cell proliferation is a key event in the development of intimal hyperplasia after arterial injury. Heparin can suppress smooth muscle cell proliferation in vitro and prevents intimal hyperplasia after arterial injury, but the mechanisms of action are poorly understood. Recently, we observed that heparin inhibited serum-induced activation of mitogen-activated protein kinase in smooth muscle cells, but heparin did not inhibit signaling induced by platelet-derived growth factor BB and basic fibroblast growth factor, both ligands of tyrosine kinase receptors. Here, we examined the possibility that heparin inhibits signaling by thrombin and other activators of heterotrimeric G-proteins. Design of Study: Baboon aortic smooth muscle cells were stimulated with thrombin, angiotensin II, endothelin-1, and lysophosphatidic acid in the presence or absence of heparin. After stimulation, mitogen-activated protein kinase activity was measured with an in-gel phosphorylation assay, mitogen-activated protein kinase kinase-1 was immunoprecipitated from the same samples, and activity was measured with recombinant mitogen-activated protein kinase as a substrate. DNA synthesis was measured by 3H-thymidine labeling and scintillation counting. Results: Heparin inhibited sustained activity of mitogen-activated protein kinase kinase-1 and mitogen-activated protein kinase and prevented DNA synthesis induced by thrombin, angiotensin II, endothelin-1, and lysophosphatidic acid. Conclusions: Heparin inhibits growth of baboon smooth muscle cells by preventing prolonged mitogen-activated protein kinase activation elicited by ligands of seven transmembrane domain receptors and heterotrimeric G-proteins. The results indicate that heparin interferes with a specific pathway in smooth muscle cell growth, which could be a future target in attempts to inhibit lesion development after vascular surgery. (J Vasc Surg 1998;27:512-20.

Induction of vascular atrophy as a novel approach to treating restenosis. A review

Regardless of the type of arterial reconstruction, luminal narrowing (stenosis or restenosis) develops in approximately one third of the vessels. In the past, the focus of research has been on the mechanisms of stenosis (intimal hyperplasia, pathologic remodeling) and pharmacologic approaches to prevention. An alternative approach is to induce intimal atrophy after luminal narrowing has developed, thus limiting treatment to only those patients that develop a problem. This approach to treat established disease by reducing wall mass through induction of cell death and extracellular matrix removal would be particularly useful for treating stenosis in synthetic bypass grafts or stented vessels, in which intimal hyperplasia is the primary mechanism of stenosis. This approach may be applicable as well to other vascular proliferative disorders, such as pulmonary hypertension and chronic transplant arteriopathy. Proof of principle has been shown in experiments with antibodies to platelet-derived growth factor (PDGF) receptors that cause neointimal regression in baboon polytetrafluoroethylene (PTFE) grafts and with angiotensin-converting enzyme inhibitors that induce medial atrophy in hypertensive arteries. Possible molecular targets could include PDGF receptors, A20, and BMP4. Further studies are needed to determine the utility of such a therapeutic approach to vascular disease

Basic science curriculum in vascular surgery residency

Recognizing the importance of basic science teaching in surgical education, the leadership of the Association of Program Directors in Vascular Surgery (APDVS) appointed a panel to gather information and to present its findings at the 1999 Annual Fall Meeting of the APDVS. A questionnaire was distributed to the program directors present. In addition, information was gathered from the American Board of Surgery regarding the basic science content in the vascular surgery item pool on the Vascular Surgery Qualifying Examination (VQE). The vascular surgery unit of the surgical resident curriculum was also analyzed. Fifty-three program directors (64%) completed the questionnaire. Although only two program directors felt that their residents were better prepared to answer basic science questions, the results of the VQE showed that the examinees do not, as a group, perform differently on basic science items than on clinical management questions. In addition, only a minority of program directors (15%) use a specific method to monitor the learning process of their residents. The majority of the program directors responding (75%) felt that they were capable of teaching basic science to residents. Interestingly, almost half the 53 respondents (47%) said that a basic science curriculum should be comprehensive, not exclusively relevant to the clinical setting. VQE content outline and the vascular surgery unit of the surgical resident curriculum revealed great emphasis on clinically relevant basic science information. The APDVS panel recommends that a basic science curriculum should be comprehensive, yet clinically pertinent, and completely integrated with the clinical curriculum. In terms of how to teach basic science in vascular residencies, the panel supports teaching conferences that are problem-based with a faculty member acting as the resource person and with specific goals set for the conferences. The panel also suggested establishing a Web site that provides a series of questions, the answers of which could be readily available to trainees and program directors. Such immediate feedback could be of great help to program directors to focus the learning process of their residents and monitor its progress. (J Vasc Surg 2001;33:854-60.)