MT1-matrix metalloproteinase directs arterial wall invasion and neointima formation by vascular smooth muscle cells

The Atherosclerotic Plaque Microenvironment as a Therapeutic Target

PURPOSE OF REVIEW

Atherosclerosis is traditionally viewed as a disease triggered by lipid accumulation, but growing evidence underscores the crucial role of the plaque microenvironment in disease progression. This review explores recent advances in understanding how cellular and extracellular components of the plaque milieu drive atherosclerosis, with a focus on leveraging these microenvironmental factors for therapeutic intervention. This review highlights recent advances in cell-cell crosstalk and matrix remodeling, offering insights into innovative therapeutic strategies for atherosclerotic cardiovascular disease.

RECENT FINDINGS

While atherosclerosis begins with the subendothelial retention of apolipoprotein B (ApoB)-containing lipoproteins​, its progression is increasingly recognized as a consequence of complex cellular and extracellular dynamics within the plaque microenvironment. Soluble factors and extracellular matrix proteins shape mechanical properties and the biochemical landscape, directly influencing cell behavior and inflammatory signaling. For instance, the deposition of transitional matrix proteins, such as fibronectin, in regions of disturbed flow primes endothelial cells for inflammation​. Likewise, impaired clearance of dead cells and chronic extracellular matrix remodeling contribute to lesion expansion and instability, further exacerbating disease severity. Targeting the plaque microenvironment presents a promising avenue for stabilizing atherosclerotic lesions. Approaches that enhance beneficial cellular interactions, such as boosting macrophage efferocytosis to resolve inflammation while mitigating proatherogenic signals like integrin-mediated endothelial activation, may promote fibrous cap formation and reduce plaque vulnerability. Harnessing these mechanisms may lead to novel therapeutic approaches aimed at modifying the plaque microenvironment to combat atherosclerotic cardiovascular disease.

Mmp14-dependent remodeling of the pericellular-dermal collagen interface governs fibroblast survival

Dermal fibroblasts deposit type I collagen, the dominant extracellular matrix molecule found in skin, during early postnatal development. Coincident with this biosynthetic program, fibroblasts proteolytically remodel pericellular collagen fibrils by mobilizing the membrane-anchored matrix metalloproteinase, Mmp14. Unexpectedly, dermal fibroblasts in Mmp14-/- mice commit to a large-scale apoptotic program that leaves skin tissues replete with dying cells. A requirement for Mmp14 in dermal fibroblast survival is recapitulated in vitro when cells are embedded within, but not cultured atop, three-dimensional hydrogels of crosslinked type I collagen. In the absence of Mmp14-dependent pericellular proteolysis, dermal fibroblasts fail to trigger β1 integrin activation and instead actuate a TGF-β1/phospho-JNK stress response that leads to apoptotic cell death in vitro as well as in vivo. Taken together, these studies identify Mmp14 as a requisite cell survival factor that maintains dermal fibroblast viability in postnatal dermal tissues.

Vesicle transport of matrix metalloproteinases

Multicellular organisms consist of cells and extracellular matrix (ECM). ECM creates a cellular microenvironment, and cells locally degrade the ECM according to their cellular activity. A major group of enzymes that modify ECM belongs to matrix metalloproteinases (MMPs) and play major roles in various pathophysiological events. ECM degradation by MMPs does not occur in all cellular surroundings but only where it is necessary, and cells achieve this by directionally secreting these proteolytic enzymes. Recent studies have indicated that such enzyme secretion is achieved by targeted vesicle transport along the microtubules, and several kinesin superfamily proteins (KIFs) have been identified as responsible motor proteins involved in the processes. This chapter discusses recent findings of the vesicle transport of MMPs and their roles.

An interferon gamma response signature links myocardial aging and immunosenescence

AIMS

Aging entails profound immunological transformations that can impact myocardial homeostasis and predispose to heart failure. However, preclinical research in the immune-cardiology field is mostly conducted in young healthy animals, which potentially weakens its translational relevance. Herein, we sought to investigate how the aging T-cell compartment associates with changes in myocardial cell biology in aged mice.

METHODS AND RESULTS

We phenotyped the antigen-experienced effector/memory T cells purified from heart-draining lymph nodes of 2-, 6-, 12-, and 18-month-old C57BL/6J mice using single-cell RNA/T cell receptor sequencing. Simultaneously, we profiled all non-cardiomyocyte cell subsets purified from 2- to 18-month-old hearts and integrated our data with publicly available cardiomyocyte single-cell sequencing datasets. Some of these findings were confirmed at the protein level by flow cytometry. With aging, the heart-draining lymph node and myocardial T cells underwent clonal expansion and exhibited an up-regulated pro-inflammatory transcription signature, marked by an increased interferon-γ (IFN-γ) production. In parallel, all major myocardial cell populations showed increased IFN-γ responsive signature with aging. In the aged cardiomyocytes, a stronger IFN-γ response signature was paralleled by the dampening of expression levels of transcripts related to most metabolic pathways, especially oxidative phosphorylation. Likewise, induced pluripotent stem cells-derived cardiomyocytes exposed to chronic, low grade IFN-γ treatment showed a similar inhibition of metabolic activity.

CONCLUSIONS

By investigating the paired age-related alterations in the T cells found in the heart and its draining lymph nodes, we provide evidence for increased myocardial IFN-γ signaling with age, which is associated with inflammatory and metabolic shifts typically seen in heart failure.

Expression of MMP-14 and its role in bone destruction in middle ear cholesteatoma: A prospective observational study

Cholesteatoma is a noncancerous cystic lesion caused by an abnormal growth of keratinizing squamous epithelium which is invasive and capable of destroying structures. A prospective study on the expression of membrane type1-matrix metalloproteinases (MMP-14) and its related influencing factors in middle ear cholesteatoma was conducted to fully understand the pathogenesis of cholesteatoma in the molecular level. We examined the expression of MMP-14 by immunohistochemical staining 39 middle ear cholesteatoma specimens and 10 external auditory meatus epithelial cell specimens. The cholesteatoma specimens were divided into 4 groups according to the degree of destruction of the ossicles during surgery. The associated factors affecting MMP-14 expression were analyzed using statistical methods; The positive expression of MMP-14 in the epithelium of the external auditory canal was significantly different between middle ear cholesteatoma and normal patients (P < .05); Gender, age, and the degree of hearing loss had no statistically significant effect on MMP-14 expression (P > .05); The expression of MMP-14 was positively correlated with the severity of bone destruction (R = 0.535, P < .05); MMP-14 plays an important role in the pathological development of the epithelium of cholesteatoma; MMP-14 expression in middle ear cholesteatoma tissue was not strongly correlated with the level of hearing loss, age or gender, but was positively correlated with the degree of middle ear bone destruction.

Type I collagen proteolysis by matrix metalloproteinase-2 contributes to focal adhesion kinase activation and vascular smooth muscle cell proliferation in the aorta in early hypertension

INTRODUCTION

Increased matrix metalloproteinase (MMP)-2 activity contributes to increase vascular smooth muscle cell (VSMC) proliferation in the aorta in early hypertension by cleaving many proteins of the extracellular matrix. Cleaved products from type I collagen may activate focal adhesion kinases (FAK) that trigger migration and proliferation signals in VSMC. We therefore hypothesized that increased activity of MMP-2 proteolyzes type I collagen in aortas of hypertensive rats, and thereby, induces FAK activation, thus leading to increased VSMC proliferation and hypertrophic remodeling in early hypertension.

METHODS

Male Sprague-Dawley rats were submitted to renovascular hypertension by the two kidney-one clip (2K1C) model and treated with doxycycline (30 mg/kg/day) by gavage from the third to seventh-day post-surgery. Controls were submitted to sham surgery. Systolic blood pressure (SBP) was measured daily by tail-cuff plethysmography and the aortas were processed for zymography and Western blot for MMP-2, pFAK/FAK, integrins and type I collagen. Mass spectrometry, morphological analysis and Ki67 immunofluorescence were also done to identify collagen changes and VSMC proliferation. A7r5 cells were stimulated with collagen and treated with the MMP inhibitors (doxycycline or ARP-100), and with the FAK inhibitor PND1186 for 24 h. Cells were lysed and evaluated by Western blot for pFAK/FAK.

RESULTS

2K1C rats developed elevated SBP in the first week as well as increased expression and activity of MMP-2 in the aorta (p < 0.05 vs. Sham). Treatment with doxycycline reduced both MMP activity and type I collagen proteolysis in aortas of 2K1C rats (p < 0.05). Increased pFAK/FAK and increased VSMC proliferation (p < 0.05 vs. Sham groups) were also seen in the aortas of 2K1C and doxycycline decreased both parameters (p < 0.05). Higher proliferation of VSMC contributed to hypertrophic remodeling as seen by increased media/lumen ratio and cross sectional area (p < 0.05 vs Sham groups). In cell culture, MMP-2 cleaves collagen, an effect reversed by MMP inhibitors (p < 0.05). Increased levels of pFAK/FAK were observed when collagen was added in the culture medium (p < 0.05 vs control) and MMP and FAK inhibitors reduced this effect.

CONCLUSIONS

Increase in MMP-2 activity proteolyzes type I collagen in the aortas of 2K1C rats and contributes to activate FAK and induces VSMC proliferation during the initial phase of hypertension.

MT1-MMP as a Key Regulator of Metastasis

Membrane type1-matrix metalloproteinase (MT1-MMP) is a member of metalloproteinases that is tethered to the transmembrane. Its major function in cancer progression is to directly degrade the extracellular matrix components, which are mainly type I-III collagen or indirectly type IV collagen through the activation of MMP-2 with a cooperative function of the tissue inhibitor of metalloproteinase-2 (TIMP-2). MT1-MMP is expressed as an inactive form (zymogen) within the endoplasmic reticulum (ER) and receives truncation processing via furin for its activation. Upon the appropriate trafficking of MT1-MMP from the ER, the Golgi apparatus to the cell surface membrane, MT1-MMP exhibits proteolytic activities to the surrounding molecules such as extracellular matrix components and cell surface molecules. MT1-MMP also retains a non-proteolytic ability to activate hypoxia-inducible factor 1 alpha (HIF-1A) via factors inhibiting the HIF-1 (FIH-1)-Mint3-HIF-1 axis, resulting in the upregulation of glucose metabolism and oxygen-independent ATP production. Through various functions of MT1-MMP, cancer cells gain motility on migration/invasion, thus causing metastasis. Despite the long-time efforts spent on the development of MT1-MMP interventions, none have been accomplished yet due to the side effects caused by off-target effects. Recently, MT1-MMP-specific small molecule inhibitors or an antibody have been reported and these inhibitors could potentially be novel agents for cancer treatment.

Nuciferine attenuates atherosclerosis by regulating the proliferation and migration of VSMCs through the Calm4/MMP12/AKT pathway in ApoE(-/-) mice fed with High-Fat-Diet

BACKGROUND

Atherosclerosis (AS) is the pathological basis of multiple cardiovascular diseases. The pathogenesis of AS is closely related to the abnormal proliferation and migration of vascular smooth muscle cells (VSMCs). Nuciferine, an aporphine alkaloid from lotus leaf, has various pharmacological activities. However, the effect and mechanism of nuciferine on regulating proliferation and migration of VSMCs against AS is still unclear.

PURPOSE

To elucidate the pharmacological effect and molecular mechanism of nuciferine on AS in ApoE^(-/-) mice fed with High-Fat-Diet (HFD).

STUDY DESIGN

HFD-fed ApoE^(-/-) mice and 3% fetal bovine serum (FBS) induced mouse aortic vascular smooth muscle cells (MOVAS) were used to investigate the protective effect and mechanism of nuciferine on AS.

METHODS

Oil red O staining was used to detect the atherosclerotic lesions. Western blotting and immunofluorescence were used to determine calmodulin 4 (Calm4) expression and localization. CCK-8 assay, transwell and wound-healing assays were used to measure the migration and proliferation of MOVAS cells.

RESULTS

Nuciferine at 40 mg/kg significantly ameliorated the aortic lesion and vascular plaque in AS model, which was equal to the effect of the positive control drug (atorvastatin). In addition, nuciferine attenuated the migration and proliferation of VSMCs in vivo and in vitro. Importantly, nuciferine down-regulated the increase of Calm4 induced by HFD-fed in ApoE^(-/-) mice or 3% FBS induced MOVAS cells. However, the inhibitory effect of nuciferine on the migration and proliferation of MOVAS cells was blocked when Calm4 was overexpressed. Furthermore, we found that nuciferine suppressed MMP12 and PI3K/Akt signaling pathway via Calm4.

CONCLUSION

Our results illustrated that Calm4 promoted the proliferation and motility of MOVAS by activating MMP12/Akt signaling pathway in AS. Nuciferine has a significant anti-atherogenic effect by regulating the proliferation and migration of VSMCs through the Calm4/MMP12/AKT signaling pathway. Thus, Calm4 could potentially be a new target for AS therapy, and nuciferine could be a potential drug against AS.

Activation of the GTPase ARF6 regulates invasion of human vascular smooth muscle cells by stimulating MMP14 activity

Hormones and growth factors stimulate vascular smooth muscle cells (VSMC) invasive capacities during the progression of atherosclerosis. The GTPase ARF6 is an important regulator of migration and proliferation of various cell types, but whether this small G protein can be activated by a variety of stimuli to promote invasion of VSMC remains unknown. Here, we aimed to define whether Platelet-derived growth factor (PDGF), a mitogenic stimulant of vascular tissues, and Angiotensin II (Ang II), a potent vasoactive peptide, can result in the activation of ARF6 in a human model of aortic SMC (HASMC). We demonstrate that these two stimuli can promote loading of GTP on this ARF isoform. Knockdown of ARF6 reduced the ability of both PDGF and Ang II to promote invasion suggesting that this GTPase regulates key molecular mechanisms mediating degradation of the extracellular matrix and migration. We report that PDGF-BB-mediated stimulation of ARF6 results in the activation of the MAPK/ERK1/2, PI3K/AKT and PAK pathways essential for invasion of HASMC. However, Ang II-mediated stimulation of ARF6 only promotes signaling through the MAPK/ERK1/2 and PAK pathways. These ARF6-mediated events lead to activation of MMP14, a membrane-bound collagenase upregulated in atherosclerosis. Moreover, ARF6 depletion decreases the release of MMP2 in the extracellular milieu. Altogether, our findings demonstrate that the GTPase ARF6 acts as a molecular switch to regulate specific signaling pathways that coordinate invasiveness of HASMC.

Dynamic Expression of Membrane Type 1-Matrix Metalloproteinase (Mt1-mmp/Mmp14) in the Mouse Embryo

MT1-MMP/MMP14 belongs to a subgroup of the matrix metalloproteinases family that presents a transmembrane domain, with a cytosolic tail and the catalytic site exposed to the extracellular space. Deficient mice for this enzyme result in early postnatal death and display severe defects in skeletal, muscle and lung development. By using a transgenic line expressing the LacZ reporter under the control of the endogenous Mt1-mmp promoter, we reported a dynamic spatiotemporal expression pattern for Mt1-mmp from early embryonic to perinatal stages during cardiovascular development and brain formation. Thus, Mt1-mmp shows expression in the endocardium of the heart and the truncus arteriosus by E8.5, and is also strongly detected during vascular system development as well as in endothelial cells. In the brain, LacZ reporter expression was detected in the olfactory bulb, the rostral cerebral cortex and the caudal mesencephalic tectum. LacZ-positive cells were observed in neural progenitors of the spinal cord, neural crest cells and the intersomitic region. In the limb, Mt1-mmp expression was restricted to blood vessels, cartilage primordium and muscles. Detection of the enzyme was confirmed by Western blot and immunohistochemical analysis. We suggest novel functions for this metalloproteinase in angiogenesis, endocardial formation and vascularization during organogenesis. Moreover, Mt1-mmp expression revealed that the enzyme may contribute to heart, muscle and brain throughout development.

Salt-Inducible Kinase 3 Promotes Vascular Smooth Muscle Cell Proliferation and Arterial Restenosis by Regulating AKT and PKA-CREB Signaling

Objective

Arterial restenosis is the pathological narrowing of arteries after endovascular procedures, and it is an adverse event that causes patients to experience recurrent occlusive symptoms. Following angioplasty, vascular smooth muscle cells (SMCs) change their phenotype, migrate, and proliferate, resulting in neointima formation, a hallmark of arterial restenosis. SIKs (salt-inducible kinases) are a subfamily of the AMP-activated protein kinase family that play a critical role in metabolic diseases including hepatic lipogenesis and glucose metabolism. Their role in vascular pathological remodeling, however, has not been explored. In this study, we aimed to understand the role and regulation of SIK3 in vascular SMC migration, proliferation, and neointima formation.

Approach and Results

We observed that SIK3 expression was low in contractile aortic SMCs but high in proliferating SMCs. It was also highly induced by growth medium in vitro and in neointimal lesions in vivo. Inactivation of SIKs significantly attenuated vascular SMC proliferation and up-regulated p21CIP1 and p27KIP1. SIK inhibition also suppressed SMC migration and modulated actin polymerization. Importantly, we found that inhibition of SIKs reduced neointima formation and vascular inflammation in a femoral artery wire injury model. In mechanistic studies, we demonstrated that inactivation of SIKs mainly suppressed SMC proliferation by down-regulating AKT (protein kinase B) and PKA (protein kinase A)-CREB (cAMP response element-binding protein) signaling. CRTC3 (CREB-regulated transcriptional coactivator 3) signaling likely contributed to SIK inactivation-mediated antiproliferative effects.

Conclusions

These findings suggest that SIK3 may play a critical role in regulating SMC proliferation, migration, and arterial restenosis. This study provides insights into SIK inhibition as a potential therapeutic strategy for treating restenosis in patients with peripheral arterial disease.

Emerging roles of MT-MMPs in embryonic development

Membrane-type matrix metalloproteinases (MT-MMPs) are cell membrane-tethered proteinases that belong to the family of the MMPs. Apart from their roles in degradation of the extracellular milieu, MT-MMPs are able to activate through proteolytic processing at the cell surface distinct molecules such as receptors, growth factors, cytokines, adhesion molecules, and other pericellular proteins. Although most of the information regarding these enzymes comes from cancer studies, our current knowledge about their contribution in distinct developmental processes occurring in the embryo is limited. In this review, we want to summarize the involvement of MT-MMPs in distinct processes during embryonic morphogenesis, including cell migration and proliferation, epithelial-mesenchymal transition, cell polarity and branching, axon growth and navigation, synapse formation, and angiogenesis. We also considered information about MT-MMP functions from studies assessed in pathological conditions and compared these data with those relevant for embryonic development.

Osteoclast-mediated bone resorption is controlled by a compensatory network of secreted and membrane-tethered metalloproteinases

Osteoclasts actively remodel both the mineral and proteinaceous components of bone during normal growth and development as well as pathologic states ranging from osteoporosis to bone metastasis. The cysteine proteinase cathepsin K confers osteoclasts with potent type I collagenolytic activity; however, cathepsin K-null mice, as well as cathepsin K-mutant humans, continue to remodel bone and degrade collagen by as-yet-undefined effectors. Here, we identify a cathepsin K-independent collagenolytic system in osteoclasts that is composed of a functionally redundant network of the secreted matrix metalloproteinase MMP9 and the membrane-anchored matrix metalloproteinase MMP14. Unexpectedly, whereas deleting either of the proteinases individually leaves bone resorption intact, dual targeting of Mmp9 and Mmp14 inhibited the resorptive activity of mouse osteoclasts in vitro and in vivo and human osteoclasts in vitro. In vivo, Mmp9/Mmp14 conditional double-knockout mice exhibited marked increases in bone density and displayed a highly protected status against either parathyroid hormone- or ovariectomy-induced pathologic bone loss. Together, these studies characterize a collagenolytic system operative in mouse and human osteoclasts and identify the MMP9/MMP14 axis as a potential target for therapeutic interventions for bone-wasting disease states.

Cellular uptake of collagens and implications for immune cell regulation in disease

As the dominant constituent of the extracellular matrix (ECM), collagens of different types are critical for the structural properties of tissues and make up scaffolds for cellular adhesion and migration. Importantly, collagens also directly modulate the phenotypic state of cells by transmitting signals that influence proliferation, differentiation, polarization, survival, and more, to cells of mesenchymal, epithelial, or endothelial origin. Recently, the potential of collagens to provide immune regulatory signals has also been demonstrated, and it is believed that pathological changes in the ECM shape immune cell phenotype. Collagens are themselves heavily regulated by a multitude of structural modulations or by catabolic pathways. One of these pathways involves a cellular uptake of collagens or soluble collagen-like defense collagens of the innate immune system mediated by endocytic collagen receptors. This cellular uptake is followed by the degradation of collagens in lysosomes. The potential of this pathway to regulate collagens in pathological conditions is evident from the increased extracellular accumulation of both collagens and collagen-like defense collagens following endocytic collagen receptor ablation. Here, we review how endocytic collagen receptors regulate collagen turnover during physiological conditions and in pathological conditions, such as fibrosis and cancer. Furthermore, we highlight the potential of collagens to regulate immune cells and discuss how endocytic collagen receptors can directly regulate immune cell activity in pathological conditions or do it indirectly by altering the extracellular milieu. Finally, we discuss the potential collagen receptors utilized by immune cells to directly detect ECM-related changes in the tissues which they encounter.

Cell-Specific Effects of GATA (GATA Zinc Finger Transcription Factor Family)-6 in Vascular Smooth Muscle and Endothelial Cells on Vascular Injury Neointimal Formation

Objective- Transcription factor GATA (GATA zinc finger transcription factor family)-6 is highly expressed in vessels and rapidly downregulated in balloon-injured carotid arteries and viral delivery of GATA-6 to the vessels limited the neointimal formation, however, little is known about its cell-specific regulation of in vivo vascular smooth muscle cell (VSMC) phenotypic state contributing to neointimal formation. This study aims to determine the role of vascular cell-specific GATA-6 in ligation- or injury-induced neointimal hyperplasia in vivo. Approach and Results- Endothelial cell and VSMC-specific GATA-6 deletion mice are generated, and the results indicate that endothelial cell-specific GATA-6 deletion mice exhibit significant decrease of VSMC proliferation and attenuation of neointimal formation after artery ligation and injury compared with the wild-type littermate control mice. PDGF (platelet-derived growth factor)-B is identified as a direct target gene, and endothelial cell-GATA-6-PDGF-B pathway regulates VSMC proliferation and migration in a paracrine manner which controls the neointimal formation. In contrast, VSMC-specific GATA-6 deletion promotes injury-induced VSMC transformation from contractile to proliferative synthetic phenotype leading to increased neointimal formation. CCN (cysteine-rich 61/connective tissue growth factor/nephroblastoma overexpressed family)-5 is identified as a novel target gene, and VSMC-specific CCN-5 overexpression in mice reverses the VSMC-GATA-6 deletion-mediated increased cell proliferation and migration and finally attenuates the neointimal formation. Conclusions- This study gives us a direct in vivo evidence of GATA-6 cell lineage-specific regulation of PDGF-B and CCN-5 on VSMC phenotypic state, proliferation and migration contributing to neointimal formation, which advances our understanding of in vivo neointimal hyperplasia, meanwhile also provides opportunities for future therapeutic interventions.

PCSK6 Is a Key Protease in the Control of Smooth Muscle Cell Function in Vascular Remodeling

RATIONALE

PCSKs (Proprotein convertase subtilisins/kexins) are a protease family with unknown functions in vasculature. Previously, we demonstrated PCSK6 upregulation in human atherosclerotic plaques associated with smooth muscle cells (SMCs), inflammation, extracellular matrix remodeling, and mitogens.

OBJECTIVE

Here, we applied a systems biology approach to gain deeper insights into the PCSK6 role in normal and diseased vessel wall.

METHODS AND RESULTS

Genetic analyses revealed association of intronic PCSK6 variant rs1531817 with maximum internal carotid intima-media thickness progression in high-cardiovascular risk subjects. This variant was linked with PCSK6 mRNA expression in healthy aortas and plaques but also with overall plaque SMA+ cell content and pericyte fraction. Increased PCSK6 expression was found in several independent human cohorts comparing atherosclerotic lesions versus healthy arteries, using transcriptomic and proteomic datasets. By immunohistochemistry, PCSK6 was localized to fibrous cap SMA+ cells and neovessels in plaques. In human, rat, and mouse intimal hyperplasia, PCSK6 was expressed by proliferating SMA+ cells and upregulated after 5 days in rat carotid balloon injury model, with positive correlation to PDGFB (platelet-derived growth factor subunit B) and MMP (matrix metalloprotease) 2/MMP14. Here, PCSK6 was shown to colocalize and cointeract with MMP2/MMP14 by in situ proximity ligation assay. Microarrays of carotid arteries from Pcsk6^-/- versus control mice revealed suppression of contractile SMC markers, extracellular matrix remodeling enzymes, and cytokines/receptors. Pcsk6^-/- mice showed reduced intimal hyperplasia response upon carotid ligation in vivo, accompanied by decreased MMP14 activation and impaired SMC outgrowth from aortic rings ex vivo. PCSK6 silencing in human SMCs in vitro leads to downregulation of contractile markers and increase in MMP2 expression. Conversely, PCSK6 overexpression increased PDGFBB (platelet-derived growth factor BB)-induced cell proliferation and particularly migration.

CONCLUSIONS

PCSK6 is a novel protease that induces SMC migration in response to PDGFB, mechanistically via modulation of contractile markers and MMP14 activation. This study establishes PCSK6 as a key regulator of SMC function in vascular remodeling. Visual Overview: An online visual overview is available for this article.

MT1-MMP evaluation in neointimal hyperplasia in the late follow-up after prosthesis implantation

Vascular surgical interventions are often burdened with late complications, including thrombosis or restenosis. The latter is generally caused by neointimal hyperplasia. Although extracellular matrix (ECM) remodelling is an important part of neointima formation, this process is not clearly understood. The aim of the study was to assess the content and activity of membrane-type 1 matrix metalloproteinase in human neointima in the late stages of its development. Matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase-2 were also evaluated. The research was performed on neointima samples collected during secondary vascular interventions from patients with chronic limb ischaemia who developed vascular occlusion at 6-18 months after aorto/ilio-femoral bypass grafting. The control material consisted of segments of femoral arteries collected from organ donors. Western blot and/or ELISA were used for the determination of MT1-MMP and TIMP-2 expression. The activity of MT1-MMP was measured by fluorometric assay and that of MMP-2 by zymography. We demonstrated significantly increased MT1-MMP protein content in neointima when compared to normal arteries. However, the activity of MT1-MMP was significantly lower in neointima than in control samples. The decreased MT1-MMP activity was concomitant with reduced activity of MMP-2. The TIMP-2 protein levels in neointima and normal arteries were not significantly different. The results of our study suggest that the reduced activity of MT1-MMP and consequently MMP-2 in human neointima may play a role in decreased degradation of ECM components and thus promote neointimal overgrowth.

Screening, Identification, and Characterization of an Affinity Peptide Specific to MT1-MMP and Its Application in Tumor Imaging

Membrane type-1 matrix metalloproteinase (MT1-MMP) plays a crucial role in many physiological and pathological processes, especially in tumor invasion and metastasis. Bioimaging of this key molecule may find wide usage in various applications. MT-loop is a unique sequence of MT1-MMP and locates in the surface of the protein. In our previous studies, AF7p, an affinity peptide that targeting the MT-loop domain of MT1-MMP, was identified by screening a phage display (Ph.D.) peptide library. However, the target of AF7p is a synthetic sequence which lacked native conformation of the MT-loop region; thus, the binding affinity and specificity in reality may not be optimal. In this study, we considered the 3-dimensional (3-D) conformation of the MT-loop area in the MT1-MMP molecule and designed a novel strategy to screen the Ph.D. peptide library. The peptide we obtained showed a better binding affinity to WT-MT1-MMP than AF7p as observed through enzyme-linked immunosorbent assay (ELISA) and biolayer interferometry (BLI). The new peptide labeled and attached MT1-MMP expression cell lines HT1080 and did not show any toxicity to cells. Furthermore, for in vivo imaging, HT1080 tumor-bearing mice with higher MT1-MMP expression accumulated more Cy5.5-HS7 than mice with MT1-MMP low-expression cell lines A549 at tumor sites, and the half-life of HS7 was longer than that of AF7p, as confirmed by ex vivo imaging of the main organs. These results suggest the feasibility of using the subtraction biopanning strategy to screen the affinity peptide targeting MT-loop regions and HS7 is a superior probe for noninvasively imaging MT1-MMP expression in MT1-MMP-positive tumor models. It provides impetus for further studies to use HS7 in early diagnosis of tumors and in peptide-mediated drugs.

The Efficacy of Systemic Doxycycline Administration as an Inhibitor of Intimal Hyperplasia after Balloon Angioplasty Arterial Injury

BACKGROUND

Intimal hyperplasia (IH) is the most common indicator for secondary intervention in peripheral vascular disease. Matrix metalloproteinases (MMPs) play a role in IH development due to their degradation of the extracellular matrix. Doxycycline (Doxy), a member of the tetracycline family of antibiotics, is a potent MMP inhibitor. We have previously shown that Doxy inhibits MMP activity and vascular smooth muscle cell migration in vitro. We hypothesized that Doxy would decrease MMP activity in vivo and inhibit the development of IH in a rodent model of vascular injury.

METHODS AND RESULTS

Doxy (400 mg/pellet) was delivered by a slow-release pellet implanted 3 days prior to or at the time of balloon angioplasty (BA) of the common carotid artery in female rats. At 14 days post-BA, intima-to-media (I:M) ratios were 0.77 ± 0.21 and 1.04 ± 0.32 in the Doxy treated groups, respectively, compared to 1.25 ± 0.26 in the control group (P = not significant; n = 3). Additionally, the tested dose of Doxy in either group had no inhibitory effect on membrane type 1-MMP or MMP-2 tissue levels, as measured by immunohistochemistry, or on systemic levels of MMP, as measured by total MMP serum levels using enzyme-linked immunosorbent assay. At 14 days post-BA, VSMC proliferation in the injured artery was increased to Doxy treatment prior to and at the time of surgery (23.5 ± 3.4 and 27.2 ± 3.9%, respectively), compared to control (11.4 ± 0.4%; n = 3), as measured by proliferating cellular nuclear antigen immunostaining.

CONCLUSIONS

In our in vivo model of vascular injury, systemic Doxy administration prior to or at the time of vascular injury does not significantly hinder the progression of IH development. Additional doses and routes of administration could be examined in order to correlate therapeutic serum levels of Doxy with effective MMP inhibition in serum and arterial tissue. However, alternative drug delivery systems are needed in order to optimize therapeutic administration of targeted MMP inhibitors for the prevention of IH development.

Matrix metalloproteinase collagenolysis in health and disease

The proteolytic processing of collagen (collagenolysis) is critical in development and homeostasis, but also contributes to numerous pathologies. Mammalian interstitial collagenolytic enzymes include members of the matrix metalloproteinase (MMP) family and cathepsin K. While MMPs have long been recognized for their ability to catalyze the hydrolysis of collagen, the roles of individual MMPs in physiological and pathological collagenolysis are less defined. The use of knockout and mutant animal models, which reflect human diseases, has revealed distinct collagenolytic roles for MT1-MMP and MMP-13. A better understanding of temporal and spatial collagen processing, along with the knowledge of the specific MMP involved, will ultimately lead to more effective treatments for cancer, arthritis, cardiovascular conditions, and infectious diseases. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.

Membrane-Tethered Metalloproteinase Expressed by Vascular Smooth Muscle Cells Limits the Progression of Proliferative Atherosclerotic Lesions

BACKGROUND

The MMP (matrix metalloproteinase) family plays diverse and critical roles in directing vascular wall remodeling in atherosclerosis. Unlike secreted-type MMPs, a member of the membrane-type MMP family, MT1-MMP (membrane-type 1 MMP; MMP14), mediates pericellular extracellular matrix degradation that is indispensable for maintaining physiological extracellular matrix homeostasis. However, given the premature mortality exhibited by MT1-MMP-null mice, the potential role of the proteinase in atherogenesis remains elusive. We sought to determine the effects of both MT1-MMP heterozygosity and tissue-specific gene targeting on atherogenesis in APOE (apolipoprotein E)-null mice.

METHODS AND RESULTS

MT1-MMP heterozygosity in the APOE-null background (Mmp14+/-Apoe-/- ) significantly promoted atherogenesis relative to Mmp14+/+Apoe-/- mice. Furthermore, the tissue-specific deletion of MT1-MMP from vascular smooth muscle cells (VSMCs) in SM22α-Cre(+)Mmp14F/FApoe-/- (VSMC-knockout) mice likewise increased the severity of atherosclerotic lesions. Although VSMC-knockout mice also developed progressive atherosclerotic aneurysms in their iliac arteries, macrophage- and adipose-specific MT1-MMP-knockout mice did not display this sensitized phenotype. In VSMC-knockout mice, atherosclerotic lesions were populated by hyperproliferating VSMCs (smooth muscle actin- and Ki67-double-positive cells) that were characterized by a proinflammatory gene expression profile. Finally, MT1-MMP-null VSMCs cultured in a 3-dimensional spheroid model system designed to mimic in vivo-like cell-cell and cell-extracellular matrix interactions, likewise displayed markedly increased proliferative potential.

CONCLUSIONS

MT1-MMP expressed by VSMCs plays a key role in limiting the progression of atherosclerosis in APOE-null mice by regulating proliferative responses and inhibiting the deterioration of VSMC function in atherogenic vascular walls.

Anti-Inflammatory, Immunomodulatory, and Tissue Repair Activity on Human Keratinocytes by Green Innovative Nanocomposites

The use of raw materials obtained by waste and processed through innovative industrial methodologies has generated an industry of about a trillion dollars in a short time, and in the near future will provide resources and services for the conservation and sustainable use of natural resources in order to ensure a better and fairer welfare for the human race. The production of nano-fiber chitin non-woven tissue is in accordance with the Organization for Economic Co-operation and Development (OECD) and European Union (EU) bio-economic programs: 100% biodegradable, ecological, and therefore useful in decreasing dependence on fossil fuel resources. The aim of our study is the evaluation of different formulations of a non-woven tissue obtained from electrospinning of a mixture of nanochitin fibrils, lignin, and poly (ethylene) oxide (PEO) on the restoration of damaged tissues. Wound repair is a complex process that involves epithelial and immune cells and includes the induction of metalloproteinases, inflammatory mediators, and angiogenic factors. Our in vitro results have shown that all of the realized chitin nanofibrils-bio-lignin non-woven tissues tested as nontoxic for human keratinocytes (HaCat) cells. Furthermore, the bio-composites that included bio-lignin at 0.1% have been able to modulate the expression of pro-inflammatory cytokines (Tumor Necrosis Factor-α, IL-1α, and IL8), lipopolysaccharide (LPS)-induced, and matrix metalloproteinases (MMPs) and human beta-defensin 2 (HBD-2) expression in HaCat cells, suggesting an anti-inflammatory and immunomodulatory role. Taken together, our results suggest that our chitin nanofibrils-bio-lignin non-woven tissue represents a skin-friendly tool that is able to favor a correct and fast wound repair.

Matrix Metalloproteinases -14, -9 and -2 are Localized to the Podosome and Involved in Podosome Development in the A7r5 Smooth Muscle Cell

Aim

The purpose of the study was to localize matrix metalloproteinase (MMP)-14, -9, and -2 in the A7r5 smooth muscle cell and to understand the interaction between these MMPs and the cytoskeleton. This interaction was observed under non-stimulating and phorbol 12, 13-dibutyrate (PDBu)-stimulating conditions.

Methods

Confocal microscopy was utilized to define the localizations of MMPs and tissue inhibitor of matrix metalloproteinases (TIMPs) in the A7r5 cell and to determine interaction between MMPs and the cytoskeleton. Under PDBu-stimulating conditions, the presence of MMP active forms and activity by gel zymography was evaluated in the A7r5 cell. Actin and microtubule-polymerization inhibitors were used to evaluate MMP interaction with the cytoskeleton and the cytoskeleton was observed on matrix and within a Type I collagen gel.

Results

MMP-14, -9, and -2 were localized to the podosome in the A7r5 smooth muscle cell and interactions were seen with these MMPs and the actin cytoskeleton. PDBu-stimulation induced increases in the protein abundance of the active forms of the MMPs and MMP-2 activity was increased. MMPs also interact with a-actin and not β-tubulin in the A7r5 cell. Galardin, also known as GM-6001, was shown to inhibit podosome formation and prevented MMP localization to the podosome. This broad spectrum MMP inhibitor also prevented collagen gel contraction and prevented cell adhesion and spreading of A7r5 cells within this collagen matrix.

Conclusion

MMPs are important in the formation and function of podosomes in the A7r5 smooth muscle cell. MMPs interact with a-actin and not β-tubulin in the A7r5 cell. Podosomes play an important role in cell migration and understanding the function of podosomes can lead to insights into cancer metastasis and cardiovascular disease.

Quantitative evaluation of single cell spread on collagen matrices

Cells change their morphology as a response to environmental cues. The quantitative evaluation of single cell spread on extracellular matrices, such as type I collagen, is a key tool in cancer research. Inherent to the manual scoring of cellular spread is inter-observer but also intra-observer variation. To overcome these problems, we have developed the Morphology Analysis Software (MAS). MAS scores phase-contrast images of cells on native type I collagen gels and identifies whether a cell has a spread or round morphology using a combination of four unique parameters: the presence of a cellular extension, the cell area, the cell eccentricity and cell circularity. The MAS software scores are equivalent to the average score of five independent observers but MAS is faster, more objective and standardized. A functional screening assay using six cytokines identified TGFα as a stimulator of HCT8/E11 and SK-BR-3 single cell spreading on top of type I collagen gels. This change in morphology correlates with increased migration potential as evidenced by xCELLigence migration assays and are counteracted by EGFR signaling pathway inhibitors. This underscores the use of morphology classification on a population of unlabeled cells as read-out of an important cancer cell property and the potential for the MAS software in drug screening strategies.

Matrix Metalloproteinases in Non-Neoplastic Disorders

The matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases belonging to the metzincin superfamily. There are at least 23 members of MMPs ever reported in human, and they and their substrates are widely expressed in many tissues. Recent growing evidence has established that MMP not only can degrade a variety of components of extracellular matrix, but also can cleave and activate various non-matrix proteins, including cytokines, chemokines and growth factors, contributing to both physiological and pathological processes. In normal conditions, MMP expression and activity are tightly regulated via interactions between their activators and inhibitors. Imbalance among these factors, however, results in dysregulated MMP activity, which causes tissue destruction and functional alteration or local inflammation, leading to the development of diverse diseases, such as cardiovascular disease, arthritis, neurodegenerative disease, as well as cancer. This article focuses on the accumulated evidence supporting a wide range of roles of MMPs in various non-neoplastic diseases and provides an outlook on the therapeutic potential of inhibiting MMP action.

Effect of TGF-β1 on the Migration and Recruitment of Mesenchymal Stem Cells after Vascular Balloon Injury: Involvement of Matrix Metalloproteinase-14

Restenosis or occlusion after vascular procedures is ascribed to intimal hyperplasia. Transforming growth factor (TGF)-β1 is involved in recruitment of mesenchymal stem cells (MSCs) following arterial injury, and its release from latent TGF-binding protein by matrix metalloproteinase (MMP)-14-induced proteolysis contributes to neointima formation. However, the relationship between MMP-14 and TGF-β1 activation in restenosis is unknown. This study investigated the relationship using a rat model of balloon-induced injury. Rats were assigned to vehicle-, SB431542 (SB)-, or recombinant human (rh)TGF-β1-treated groups and examined at various time points after balloon-induced injury for expression of TGF-β1/Smad signalling pathway components, MMP-14 and MSCs markers including Nestin, CD29, and Sca1⁺CD29⁺CD11b/c⁻CD45⁻. Intimal hyperplasia was reduced in SB- and rhTGF-β1-treated rats. The expression of TGF-β1, TGF-β1RI, and Smad2/3 was decreased, but the levels of phosphorylated Smad2/3 were higher in SB-treated rats than vehicle-treated after 7 days to 14 days. rhTGF-β1 administration decreased the expression of TGF-β1/Smad pathway proteins, except for TGF-β1RI. Nestin and CD29 expression and the number of Sca1⁺CD29⁺CD11b⁻CD45⁻ cells were reduced, whereas MMP-14 expression was increased after SB431542 and rhTGF-β1 administration. These results suggest that TGF-β1/Smad signalling and MMP-14 act to recruit MSCs which differentiate to vascular smooth muscle cells and mesenchymal-like cells that participate in arterial repair/remodelling.

Transcription factor KLF6 upregulates expression of metalloprotease MMP14 and subsequent release of soluble endoglin during vascular injury

After endothelial injury, the transcription factor Krüppel-like factor 6 (KLF6) translocates into the cell nucleus to regulate a variety of target genes involved in angiogenesis, vascular repair and remodeling, including components of the membrane transforming growth factor beta (TGF-β) receptor complex such as endoglin and activin receptor-like kinase 1. The membrane metalloproteinase 14 (MMP14 or MT1-MMP) targets endoglin to release soluble endoglin and is involved in vascular inflammation and endothelial tubulogenesis. However, little is known about the regulation of MMP14 expression during vascular wounding. In vitro denudation of monolayers of human endothelial cell monolayers leads to an increase in the KLF6 gene transcriptional rate, followed by an upregulation of MMP14 and release of soluble endoglin. Concomitant with this process, MMP14 co-localizes with endoglin in the sprouting endothelial cells surrounding the wound border. MMP14 expression at mRNA and protein levels is increased by ectopic KLF6 and downregulated by KLF6 suppression in cultured endothelial cells. Moreover, after wire-induced endothelial denudation, Klf6^+/− mice show lower levels of MMP14 in their vasculature compared with their wild-type siblings. Ectopic cellular expression of KLF6 results in an increased transcription rate of MMP14, and chromatin immunoprecipitation assays show that KLF6 interacts with MMP14 promoter in ECs, this interaction being enhanced during wound healing. Furthermore, KLF6 markedly increases the transcriptional activity of different reporter constructs of MMP14 gene promoter. These results suggest that KLF6 regulates MMP14 transcription and is a critical player of the gene expression network triggered during endothelial repair.

The tissue-engineered human cornea as a model to study expression of matrix metalloproteinases during corneal wound healing

Corneal injuries remain a major cause of consultation in the ophthalmology clinics worldwide. Repair of corneal wounds is a complex mechanism that involves cell death, migration, proliferation, differentiation, and extracellular matrix (ECM) remodeling. In the present study, we used a tissue-engineered, two-layers (epithelium and stroma) human cornea as a biomaterial to study both the cellular and molecular mechanisms of wound healing. Gene profiling on microarrays revealed important alterations in the pattern of genes expressed by tissue-engineered corneas in response to wound healing. Expression of many MMPs-encoding genes was shown by microarray and qPCR analyses to increase in the migrating epithelium of wounded corneas. Many of these enzymes were converted into their enzymatically active form as wound closure proceeded. In addition, expression of MMPs by human corneal epithelial cells (HCECs) was affected both by the stromal fibroblasts and the collagen-enriched ECM they produce. Most of all, results from mass spectrometry analyses provided evidence that a fully stratified epithelium is required for proper synthesis and organization of the ECM on which the epithelial cells adhere. In conclusion, and because of the many characteristics it shares with the native cornea, this human two layers corneal substitute may prove particularly useful to decipher the mechanistic details of corneal wound healing.

Membrane Type 1 Matrix Metalloproteinase Regulates Monocyte Migration and Collagen Destruction in Tuberculosis

Tuberculosis (TB) remains a global pandemic and drug resistance is rising. Multicellular granuloma formation is the pathological hallmark of Mycobacterium tuberculosis infection. The membrane type 1 matrix metalloproteinase (MT1-MMP or MMP-14) is a collagenase that is key in leukocyte migration and collagen destruction. In patients with TB, induced sputum MT1-MMP mRNA levels were increased 5.1-fold compared with matched controls and correlated positively with extent of lung infiltration on chest radiographs (r = 0.483; p < 0.05). M. tuberculosis infection of primary human monocytes increased MT1-MMP surface expression 31.7-fold and gene expression 24.5-fold. M. tuberculosis-infected monocytes degraded collagen matrix in an MT1-MMP-dependent manner, and MT1-MMP neutralization decreased collagen degradation by 73%. In human TB granulomas, MT1-MMP immunoreactivity was observed in macrophages throughout the granuloma. Monocyte-monocyte networks caused a 17.5-fold increase in MT1-MMP surface expression dependent on p38 MAPK and G protein-coupled receptor-dependent signaling. Monocytes migrating toward agarose beads impregnated with conditioned media from M. tuberculosis-infected monocytes expressed MT1-MMP. Neutralization of MT1-MMP activity decreased this M. tuberculosis network-dependent monocyte migration by 44%. Taken together, we demonstrate that MT1-MMP is central to two key elements of TB pathogenesis, causing collagen degradation and regulating monocyte migration.

Deficiency of MMP17/MT4-MMP proteolytic activity predisposes to aortic aneurysm in mice

RATIONALE

Aortic dissection or rupture resulting from aneurysm causes 1% to 2% of deaths in developed countries. These disorders are associated with mutations in genes that affect vascular smooth muscle cell differentiation and contractility or extracellular matrix composition and assembly. However, as many as 75% of patients with a family history of aortic aneurysms do not have an identified genetic syndrome.

OBJECTIVE

To determine the role of the protease MMP17/MT4-MMP in the arterial wall and its possible relevance in human aortic pathology.

METHODS AND RESULTS

Screening of patients with inherited thoracic aortic aneurysms and dissections identified a missense mutation (R373H) in the MMP17 gene that prevented the expression of the protease in human transfected cells. Using a loss-of-function genetic mouse model, we demonstrated that the lack of Mmp17 resulted in the presence of dysfunctional vascular smooth muscle cells and altered extracellular matrix in the vessel wall; and it led to increased susceptibility to angiotensin-II-induced thoracic aortic aneurysm. We also showed that Mmp17-mediated osteopontin cleavage regulated vascular smooth muscle cell maturation via c-Jun N-terminal kinase signaling during aorta wall development. Some features of the arterial phenotype were prevented by re-expression of catalytically active Mmp17 or the N-terminal osteopontin fragment in Mmp17-null neonates.

CONCLUSIONS

Mmp17 proteolytic activity regulates vascular smooth muscle cell phenotype in the arterial vessel wall, and its absence predisposes to thoracic aortic aneurysm in mice. The rescue of part of the vessel-wall phenotype by a lentiviral strategy opens avenues for therapeutic intervention in these life-threatening disorders.

MEF2B-Nox1 signaling is critical for stretch-induced phenotypic modulation of vascular smooth muscle cells

OBJECTIVE

Blood vessel hemodynamics have profound influences on function and structure of vascular cells. One of the main mechanical forces influencing vascular smooth muscle cells (VSMC) is cyclic stretch (CS). Increased CS stimulates reactive oxygen species (ROS) production in VSMC, leading to their dedifferentiation, yet the mechanisms involved are poorly understood. This study was designed to test the hypothesis that pathological CS stimulates NADPH oxidase isoform 1 (Nox1)-derived ROS via MEF2B, leading to VSMC dysfunction via a switch from a contractile to a synthetic phenotype.

APPROACH AND RESULTS

Using a newly developed isoform-specific Nox1 inhibitor and gene silencing technology, we demonstrate that a novel pathway, including MEF2B-Nox1-ROS, is upregulated under pathological stretch conditions, and this pathway promotes a VSMC phenotypic switch from a contractile to a synthetic phenotype. We observed that CS (10% at 1 Hz) mimicking systemic hypertension in humans increased Nox1 mRNA, protein levels, and enzymatic activity in a time-dependent manner, and this upregulation was mediated by MEF2B. Furthermore, we show that stretch-induced Nox1-derived ROS upregulated a specific marker for synthetic phenotype (osteopontin), whereas it downregulated classical markers for contractile phenotype (calponin1 and smoothelin B). In addition, our data demonstrated that stretch-induced Nox1 activation decreases actin fiber density and augments matrix metalloproteinase 9 activity, VSMC migration, and vectorial alignment.

CONCLUSIONS

These results suggest that CS initiates a signal through MEF2B that potentiates Nox1-mediated ROS production and causes VSMC to switch to a synthetic phenotype. The data also characterize a new Nox1 inhibitor as a potential therapy for treatment of vascular dysfunction in hypertension.

Metalloproteinases promote plaque rupture and myocardial infarction: A persuasive concept waiting for clinical translation

Atherosclerotic plaque rupture provokes most myocardial infarctions. Matrix metalloproteinases (MMPs) have counteracting roles in intimal thickening, which stabilizes plaques, on the one hand and extracellular matrix destruction that leads to plaque rupture on the other. This review briefly summarizes the key points supporting the involvement of individual MMPs in provoking plaque rupture and discusses the barriers that stand in the way of clinical translation, which can be itemised as follows: structural and functional complexity of the MMP family; lack of adequate preclinical models partly owing to different expression patterns of MMPs and TIMPs in mouse and human macrophages; the need to target individual MMPs selectively; the difficulties in establishing causality in human studies; and the requirement for surrogate markers of efficacy. Overcoming these barriers would open the way to new treatments that could have a major impact on cardiovascular mortality worldwide.

Extracellular matrix determinants and the regulation of cancer cell invasion stratagems

During development, wound repair and disease-related processes, such as cancer, normal, or neoplastic cell types traffic through the extracellular matrix (ECM), the complex composite of collagens, elastin, glycoproteins, proteoglycans, and glycosaminoglycans that dictate tissue architecture. Current evidence suggests that tissue-invasive processes may proceed by protease-dependent or protease-independent strategies whose selection is not only governed by the characteristics of the motile cell population, but also by the structural properties of the intervening ECM. Herein, we review the mechanisms by which ECM dimensionality, elasticity, crosslinking, and pore size impact patterns of cell invasion. This summary should prove useful when designing new experimental approaches for interrogating invasion programs as well as identifying potential cellular targets for next-generation therapeutics.

Phenotypic modulation of primary vascular smooth muscle cells by short-term culture on micropatterned substrate

Loss of contractility and acquisition of an epithelial phenotype of vascular smooth muscle cells (VSMCs) are key events in proliferative vascular pathologies such as atherosclerosis and post-angioplastic restenosis. There is no proper cell culture system allowing differentiation of VSMCs so that it is difficult to delineate the molecular mechanism responsible for proliferative vasculopathy. We investigated whether a micropatterned substrate could restore the contractile phenotype of VSMCs in vitro. To induce and maintain the differentiated VSMC phenotype in vitro, we introduced a micropatterned groove substrate to modulate the morphology and function of VSMCs. Later than 7(th) passage of VSMCs showed typical synthetic phenotype characterized by epithelial morphology, increased proliferation rates and corresponding gene expression profiles; while short-term culture of these cells on a micropatterned groove induced a change to an intermediate phenotype characterized by low proliferation rates, increased migration, a spindle-like morphology associated with cytoskeletal rearrangement and expression of muscle-specific genes. Microarray analysis showed preferential expression of contractile and smooth muscle cell-specific genes in cells cultured on the micropatterned groove. Culture on a patterned groove may provide a valuable model for the study the role of VSMCs in normal vascular physiology and a variety of proliferative vascular diseases.

Basal localization of MT1-MMP is essential for epithelial cell morphogenesis in 3D collagen matrix

The membrane-anchored collagenase membrane type 1 matrix metalloprotease (MT1-MMP) has been shown to play an essential role during epithelial tubulogenesis in 3D collagen matrices; however, its regulation during tubulogenesis is not understood. Here, we report that degradation of collagen in polarized epithelial cells is post-translationally regulated by changing the localization of MT1-MMP from the apical to the basal surface. MT1-MMP predominantly localizes at the apical surface in inert polarized epithelial cells, whereas treatment with HGF induced basal localization of MT1-MMP followed by collagen degradation. The basal localization of MT1-MMP requires the ectodomains of the enzyme because deletion of the MT-loop region or the hemopexin domain inhibited basal localization of the enzyme. TGFβ is a well-known inhibitor of tubulogenesis and our data indicate that its mechanism of inhibition is, at least in part, due to inhibition of MT1-MMP localization to the basal surface. Interestingly, however, the effect of TGFβ was found to be bi-phasic: at high doses it effectively inhibited basal localization of MT1-MMP, whereas at lower doses tubulogenesis and basal localization of MT1-MMP was promoted. Taken together, these data indicate that basal localization of MT1-MMP is a key factor promoting the degradation of extracellular matrix by polarized epithelial cells, and that this is an essential part of epithelial morphogenesis in 3D collagen.

Matrix metalloproteinases in coronary artery disease

Matrix metalloproteinases (MMP) are a family of zinc-containing endoproteinases that degrade extracellular matrix (ECM) components. MMP have important roles in the development, physiology and pathology of cardiovascular system. Metalloproteases also play key roles in adverse cardiovascular remodeling, atherosclerotic plaque formation and plaque instability, vascular smooth muscle cell (SMC) migration and restenosis that lead to coronary artery disease (CAD), and progressive heart failure. The study of MMP in developing animal model cardiovascular systems has been helpful in deciphering numerous pathologic conditions in humans. Increased peripheral blood MMP-2 and MMP-9 in acute coronary syndrome (ACS) may be useful as noninvasive tests for detection of plaque vulnerability. MMP function can be modulated by certain pharmacological drugs that can be exploited for treatment of ACS. CAD is a polygenic disease and hundreds of genes contribute toward its predisposition. A large number of sequence variations in MMP genes have been identified. Case-control association studies have highlighted their potential association with CAD and its clinical manifestations. Although results thus far are inconsistent, meta-analysis has demonstrated that MMP-3 Glu45Lys and MMP-9 1562C/T gene polymorphisms were associated with CAD risk.

Heading off with the herd: how cancer cells might maneuver supernumerary centrosomes for directional migration

The complicity of centrosomes in carcinogenesis is unmistakable. Mounting evidence clearly implicates a robust correlation between centrosome amplification (CA) and malignant transformation in diverse tissue types. Furthermore, CA has been suggested as a marker of cancer aggressiveness, in particular the invasive phenotype, in breast and prostate cancers. One means by which CA promotes malignancy is through induction of transient spindle multipolarity during mitosis, which predisposes the cell to karyotypic changes arising from low-grade chromosome mis-segregation. It is well recognized that during cell migration in interphase, centrosome-mediated nucleation of a radial microtubule array is crucial for establishing a polarized Golgi apparatus, without which directionality is precluded. The question of how cancer cells maneuver their supernumerary centrosomes to achieve directionality during cell migration is virtually uncharted territory. Given that CA is a hallmark of cancers and has been correlated with cancer aggressiveness, malignant cells are presumably competent in managing their centrosome surfeit during directional migration, although the cellular logistics of this process remain unexplored. Another key angle worth pondering is whether an overabundance of centrosomes confers some advantage on cancer cells in terms of their migratory and invasive capabilities. Recent studies have uncovered a remarkable strategy that cancer cells employ to deal with the problem of excess centrosomes and ensure bipolar mitoses, viz., centrosome clustering. This review aims to change the narrative by exploring how an increased centrosome complement may, via aneuploidy-independent modulation of the microtubule cytoskeleton, enhance directional migration and invasion of malignant cells. We postulate that CA imbues cancer cells with cytoskeletal advantages that enhance cell polarization, Golgi-dependent vesicular trafficking, stromal invasion, and other aspects of metastatic progression. We also propose that centrosome declustering may represent a novel, cancer cell-specific antimetastatic strategy, as cancer cells may rely on centrosome clustering during migration as they do in mitosis. Elucidation of these details offers an exciting avenue for future research, as does investigating how CA may promote metastasis through enhanced directional migration.

MT-LOOP-dependent localization of membrane type I matrix metalloproteinase (MT1-MMP) to the cell adhesion complexes promotes cancer cell invasion

Localization of membrane type I matrix metalloproteinase (MT1-MMP) to the leading edge is thought to be a crucial step during cancer cell invasion. However, its mechanisms and functional impact on cellular invasion have not been clearly defined. In this report, we have identified the MT-LOOP, a loop region in the catalytic domain of MT1-MMP ((163)PYAYIREG(170)), as an essential region for MT1-MMP to promote cellular invasion. Deletion of the MT-LOOP effectively inhibited functions of MT1-MMP on the cell surface, including proMMP-2 activation, degradation of gelatin and collagen films, and cellular invasion into a collagen matrix. This is not due to loss of the catalytic function of MT1-MMP but due to inefficient localization of the enzyme to β1-integrin-rich cell adhesion complexes at the plasma membrane. We also found that an antibody that specifically recognizes the MT-LOOP region of MT1-MMP (LOOPAb) inhibited MT1-MMP functions, fully mimicking the phenotype of the MT-LOOP deletion mutant. We therefore propose that the MT-LOOP region is an interface for molecular interactions that mediate enzyme localization to cell adhesion complexes and regulate MT1-MMP functions. Our findings have revealed a novel mechanism regulating MT1-MMP during cellular invasion and have identified the MT-LOOP as a potential exosite target region to develop selective MT1-MMP inhibitors.

Matrix metalloproteinases: inflammatory regulators of cell behaviors in vascular formation and remodeling

Abnormal angiogenesis and vascular remodeling contribute to pathogenesis of a number of disorders such as tumor, arthritis, atherosclerosis, restenosis, hypertension, and neurodegeneration. During angiogenesis and vascular remodeling, behaviors of stem/progenitor cells, endothelial cells (ECs), and vascular smooth muscle cells (VSMCs) and its interaction with extracellular matrix (ECM) play a critical role in the processes. Matrix metalloproteinases (MMPs), well-known inflammatory mediators are a family of zinc-dependent proteolytic enzymes that degrade various components of ECM and non-ECM molecules mediating tissue remodeling in both physiological and pathological processes. MMPs including MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-12, and MT1-MMP, are stimulated and activated by various stimuli in vascular tissues. Once activated, MMPs degrade ECM proteins or other related signal molecules to promote recruitment of stem/progenitor cells and facilitate migration and invasion of ECs and VSMCs. Moreover, vascular cell proliferation and apoptosis can also be regulated by MMPs via proteolytically cleaving and modulating bioactive molecules and relevant signaling pathways. Regarding the importance of vascular cells in abnormal angiogenesis and vascular remodeling, regulation of vascular cell behaviors through modulating expression and activation of MMPs shows therapeutic potential.

Overexpression of endogenous TIMP-2 increases the proliferation of BeWo choriocarcinoma cells through the MAPK-signaling pathway

Choriocarcinoma is a highly malignant form of trophoblastic tumor that is characterized by malignant placental tumors and rapid cell growth. In vivo and in vitro studies have demonstrated that tissue inhibitor of metalloproteinase 2 (TIMP-2) is present in choriocarcinoma. However, the role of TIMP-2 in cell proliferation in choriocarcinoma has not been investigated. Exogenous TIMP-2 is known to promote cell proliferation. During growth, cells are subjected to varied concentrations of TIMP-2, which depend on the amount of TIMP-2 produced by the cells themselves. Thus, the effect of gradually increasing endogenous TIMP-2 on the proliferation of choriocarcinoma cells needs to be examined. Proliferation of BeWo human choriocarcinoma cells was stimulated by transient transfection of a plasmid expressing TIMP-2. Overexpression of endogenous TIMP-2 also activated ERK1/2 and JNK1/2 of the MAPK-signaling pathway. Furthermore, inhibition of these proteins resulted in suppression of the cell proliferation-stimulating effect of TIMP-2. These results suggest that TIMP-2 plays an important role in tumor growth in the case of BeWo cells. Moreover, proliferation of BeWo cells due to TIMP-2 expression can be used as a model for fast-growing choriocarcinomas, and TIMP-2 could be used as a novel tumor marker of choriocarcinoma.

Vinpocetine suppresses pathological vascular remodeling by inhibiting vascular smooth muscle cell proliferation and migration

Abnormal vascular smooth muscle cell (SMC) activation is associated with various vascular disorders such as atherosclerosis, in-stent restenosis, vein graft disease, and transplantation-associated vasculopathy. Vinpocetine, a derivative of the alkaloid vincamine, has long been used as a cerebral blood flow enhancer for treating cognitive impairment. However, its role in pathological vascular remodeling remains unexplored. Herein, we show that systemic administration of vinpocetine significantly reduced neointimal formation in carotid arteries after ligation injury. Vinpocetine also markedly decreased spontaneous remodeling of human saphenous vein explants in ex vivo culture. In cultured SMCs, vinpocetine dose-dependently suppressed cell proliferation and caused G1-phase cell cycle arrest, which is associated with a decrease in cyclin D1 and an increase in p27Kip1 levels. In addition, vinpocetine dose-dependently inhibited platelet-derived growth factor (PDGF)-stimulated SMC migration as determined by the two-dimensional migration assays and three-dimensional aortic medial explant invasive assay. Moreover, vinpocetine significantly reduced PDGF-induced type I collagen and fibronectin expression. It is noteworthy that PDGF-stimulated phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2), but not protein kinase B, was specifically inhibited by vinpocetine. Vinpocetine powerfully attenuated intracellular reactive oxidative species (ROS) production, which largely mediates the inhibitory effects of vinpocetine on ERK1/2 activation and SMC growth. Taken together, our results reveal a novel function of vinpocetine in attenuating neointimal hyperplasia and pathological vascular remodeling, at least partially through suppressing ROS production and ERK1/2 activation in SMCs. Given the safety profile of vinpocetine, this study provides insight into the therapeutic potential of vinpocetine in proliferative vascular disorders.

Effect of hormone replacement therapy in matrix metalloproteinase expression and intimal hyperplasia development after vascular injury

BACKGROUND

Postmenopausal women taking hormone replacement therapy (HRT) require secondary intervention after vascular reconstruction more frequently than women not taking HRT, often due to increased development of intimal hyperplasia (IH). Matrix metalloproteinases (MMPs) play a role in IH by degradation and remodeling of components of the vascular basement membrane. The MMP pathway is regulated by a balance between MMPs, membrane-type MMPs (MT-MMPs), and tissue inhibitor of MMPs (TIMPs). We have recently provided evidence for unbalanced regulation of the MT1-MMP/MMP-2 pathway in vascular smooth muscle cells (VSMCs) exposed to hormones in vitro. Herein we study the role of HRT in the development of IH in a postmenopausal rodent model of vascular injury and in the modulation of this MMP regulatory pathway in vivo.

METHODS

Female rats were aged to 12 months. Animals were ovariectomized (OVX) and 4 weeks later hormones or placebo was delivered via a 90-day slow-release pellet. After 6 weeks of HRT each rat underwent balloon angioplasty of the left common carotid artery. At 14 days postinjury tissue samples were collected and stained with trichrome elastin and for isoform-specific MMPs.

RESULTS

After vascular injury, the intima:media (I:M) ratio was decreased in OVX rats receiving placebos as compared with non-OVX controls (P < 0.05). In OVX animals receiving HRT, estrogen with and without progesterone and progesterone alone slightly increased I:M ratio compared with placebo, although no significant difference was found in any HRT group. Injury-induced intimal expression of MMP-2 and -9 was decreased in OVX placebo animals compared with non-OVX controls (P < 0.05). MMP-2 and -9 levels were subsequently increased by each type of hormone therapy compared with placebo, with a significant increase in MMP-9 in response to estrogen with and without progesterone (P < 0.05). Conversely, TIMP-2 was decreased by estrogen compared with placebo (P < 0.05). There was no effect on intimal MT1-MMP in any group.

CONCLUSIONS

In this study we detected a statistically significant decrease in IH as a result of OVX. Subsequent HRT exposure resulted in increased I:M ratios compared with OVX animals given placebo, although significance was not reached with the doses given. Long-term exogenous exposure may have a more deleterious effect compared with acute exposure and should be examined further. We also demonstrated a significant reduction in MMP-2 and -9 and TIMP-2 in response to OVX. Subsequent hormone exposure resulted in the upregulation of MMP-2 and -9 without a counterregulatory increase in TIMP, indicating that HRT modulates the MMP regulatory pathway in vivo. The data suggest that the lack of hormones after OVX protects against pathologic remodeling in our aged model of disease and that exposure to both natural and exogenous hormones could be a negative risk factor resulting in an exaggerated vascular response to injury. Future studies should focus on in vivo manipulation of unbalanced MMP regulation for prevention of IH in response to HRT and in general. Furthermore, the age-associated difference in response to the presence of natural hormones in young vs aged models should be investigated.

Bone marrow stromal cells stimulate an angiogenic program that requires endothelial MT1-MMP

Bone marrow-derived stromal/stem cells (BMSCs) have recently been characterized as mediators of tissue regeneration after injury. In addition to preventing fibrosis at the wound site, BMSCs elicit an angiogenic response within the fibrin matrix. The mechanistic interactions between BMSCs and invading endothelial cells (ECs) during this process are not fully understood. Using a three-dimensional, fibrin-based angiogenesis model, we sought to investigate the proteolytic mechanisms by which BMSCs promote vessel morphogenesis. We find that BMSC-mediated vessel formation depends on the proteolytic ability of membrane type 1-matrix metalloproteinase (MT1-MMP). Knockdown of the protease results in a small network of vessels with enlarged lumens. Contrastingly, vessel morphogenesis is unaffected by the knockdown of MMP-2 and MMP-9. Furthermore, we find that BMSC-mediated vessel morphogenesis in vivo follows mechanisms similar to what we observe in vitro. Subcutaneous, cellular fibrin implants in C.B-17/SCID mice form aberrant vasculature when MMPs are inhibited with a broad-spectrum chemical inhibitor, and a very minimal amount of vessels when MT1-MMP proteolytic activity is interrupted in ECs. Other studies have debated the necessity of MT1-MMP in the context of vessel invasion in fibrin, but this study clearly demonstrates its requirement in BMSC-mediated angiogenesis.

MT1-MMP regulates the PI3Kδ·Mi-2/NuRD-dependent control of macrophage immune function

Macrophages play critical roles in events ranging from host defense to obesity and cancer, where they infiltrate affected tissues and orchestrate immune responses in tandem with the remodeling of the extracellular matrix (ECM). Despite the dual roles played by macrophages in inflammation, the functions of macrophage-derived proteinases are typically relegated to tissue-invasive or -degradative events. Here we report that the membrane-tethered matrix metalloenzyme MT1-MMP not only serves as an ECM-directed proteinase, but unexpectedly controls inflammatory gene responses wherein MT1-MMP(-/-) macrophages mount exaggerated chemokine and cytokine responses to immune stimuli both in vitro and in vivo. MT1-MMP modulates inflammatory responses in a protease-independent fashion in tandem with its trafficking to the nuclear compartment, where it triggers the expression and activation of a phosphoinositide 3-kinase δ (PI3Kδ)/Akt/GSK3β signaling cascade. In turn, MT1-MMP-dependent PI3Kδ activation regulates the immunoregulatory Mi-2/NuRD nucleosome remodeling complex that is responsible for controlling macrophage immune response. These findings identify a novel role for nuclear MT1-MMP as a previously unsuspected transactivator of signaling networks central to macrophage immune responses.

Peri-adipocyte ECM remodeling in obesity and adipose tissue fibrosis

Adipocytes differentiate and function in environments rich in extracellular matrix (ECM) proteins. The phenotypes of genetically modified mice have aided in recognizing the importance of ECM proteins and their modifiers, e.g., proteinases, in the regulation of obesity and metabolism. Most of the molecular mechanisms through which ECM proteins and modifiers regulate adipogenesis or adipocyte function have not been fully defined. Adipose tissue fibrosis may be a factor that links obesity to diabetes or cardiovascular disease risk in conjunction with tissue inflammation. Defining the molecular mechanisms through which the ECM environment regulates adipogenesis and adipocyte function should provide us with a better understanding of the disease link between obesity and diabetes or cardiovascular diseases.

MT1-MMP-dependent remodeling of cardiac extracellular matrix structure and function following myocardial infarction

The myocardial extracellular matrix (ECM), an interwoven meshwork of proteins, glycoproteins, proteoglycans, and glycosaminoglycans that is dominated by polymeric fibrils of type I collagen, serves as the mechanical scaffold on which myocytes are arrayed for coordinated and synergistic force transduction. Following ischemic injury, cardiac ECM remodeling is initiated via localized proteolysis, the bulk of which has been assigned to matrix metalloproteinase (MMP) family members. Nevertheless, the key effector(s) of myocardial type I collagenolysis both in vitro and in vivo have remained unidentified. In this study, using cardiac explants from mice deficient in each of the major type I collagenolytic MMPs, including MMP-13, MMP-8, MMP-2, MMP-9, or MT1-MMP, we identify the membrane-anchored MMP, MT1-MMP, as the dominant collagenase that is operative within myocardial tissues in vitro. Extending these observations to an in vivo setting, mice heterozygous for an MT1-MMP-null allele display a distinct survival advantage and retain myocardial function relative to wild-type littermates in an experimental model of myocardial infarction, effects associated with preservation of the myocardial type I collagen network as a consequence of the decreased collagenolytic potential of cardiac fibroblasts. This study identifies MT1-MMP as a key MMP responsible for effecting postinfarction cardiac ECM remodeling and cardiac dysfunction.

Time course involvement of matrix metalloproteinases in the vascular alterations of renovascular hypertension

Increased vascular matrix metalloproteinases (MMPs) levels play a role in late phases of hypertensive vascular remodeling. However, no previous study has examined the time course of MMPs in the various phases of two-kidney, one-clip hypertension (2K1C). We examined structural vascular changes, collagen and elastin content, vascular oxidative stress, and MMPs levels/activities during the development of 2K1C hypertension. Plasma angiotensin converting enzyme (ACE) activity was measured to assess renin-angiotensin system activation. Sham or 2K1C hypertensive rats were studied after 2, 4, 6, and 10weeks of hypertension. Systolic blood pressure (SBP) was monitored weekly. Morphometry of structural changes in the aortic wall was studied in hematoxylin/eosin, orcein and picrosirius red sections. Aortic NADPH activity and superoxide production was evaluated. Aortic gelatinolytic activity was determined by in situ zymography, and MMP-2, MMP-14, and tissue inhibitor of MMPs (TIMP)-2 levels were determined by gelatin zymography, immunofluorescence and immunohistochemistry. 2K1C hypertension was associated with increased ACE activity, which decreased to normal after 10 weeks. We found increased aortic collagen and elastin content in the early phase of hypertension, which were associated with vascular hypertrophy, increased vascular MMP-2 and MMP-14 (but not TIMP-2) levels, and increased gelatinolytic activity, possibly as a result of increased vascular NADPH oxidase activity and oxidative stress. These results indicate that vascular remodeling of renovascular hypertension is an early process associated with early increases in MMPs activities, enhanced matrix deposition and oxidative stress. Using antioxidants or MMPs inhibitors in the early phase of hypertension may prevent the vascular alterations of hypertension.