Specific degradation of the collagen molecule by tadpole collagenolytic enzyme

Biphenylsulfonamides as effective MMP-2 inhibitors with promising antileukemic efficacy: Synthesis, in vitro biological evaluation, molecular docking, and MD simulation analysis

Overexpression of matrix metalloproteinase-2 (MMP-2) possesses a correlation with leukemia especially chronic myeloid leukemia (CML). However, no such MMP-2 inhibitor has come out in the market to date for treating leukemia. In this study, synthesis, biological evaluation, and molecular modeling studies of a set of biphenylsulfonamide derivatives as promising MMP-2 inhibitors were performed, focusing on their potential applications as antileukemic therapeutics. Compounds DH-18 and DH-19 exerted the most effective MMP-2 inhibition (IC50 of 139.45 nM and 115.16 nM, respectively) with potent antileukemic efficacy against the CML cell line K562 (IC50 of 0.338 µM and 0.398 µM, respectively). The lead molecules DH-18 and DH-19 reduced the MMP-2 expression by 21.3% and 17.8%, respectively with effective apoptotic induction (45.4% and 39.8%, respectively) in the K562 cell line. Moreover, both these compounds significantly arrested different phases of the cell cycle. Again, both these molecules depicted promising antiangiogenic efficacy in the ACHN cell line. Nevertheless, the molecular docking and molecular dynamics (MD) simulation studies revealed that DH-18 formed strong bidentate chelation with the catalytic Zn2+ ion through the hydroxamate zinc binding group (ZBG). Apart from that, the MD simulation study also disclosed stable binding interactions of DH-18 and MMP-2 along with crucial interactions with active site amino acid residues namely His120, Glu121, His124, His130, Pro140, and Tyr142. In a nutshell, this study highlighted the importance of biphenylsulfonamide-based novel and promising MMP-2 inhibitors to open up a new avenue for potential therapy against CML.

Mechanochemistry of collagen

The collagen molecular family is the result of nearly one billion years of evolution. It is a unique family of proteins, the majority of which provide general mechanical support to biological tissues. Fibril forming collagens are the most abundant collagens in vertebrate animals and are generally found in positions that resist tensile loading. In animals, cells produce fibril-forming collagen molecules that self-assemble into larger structures known as collagen fibrils. Collagen fibrils are the fundamental, continuous, load-bearing elements in connective tissues, but are often further aggregated into larger load-bearing structures, fascicles in tendon, lamellae in cornea and in intervertebral disk. We know that failure to form fibrillar collagen is embryonic lethal, and excessive collagen formation/growth (fibrosis) or uncontrolled enzymatic remodeling (type II collagen: osteoarthritis) is pathological. Collagen is thus critical to vertebrate viability and instrumental in maintaining efficient mechanical structures. However, despite decades of research, our understanding of collagen matrix formation is not complete, and we know still less about the detailed mechanisms that drive collagen remodeling, growth, and pathology. In this perspective, we examine the known role of mechanical force on the formation and development of collagenous structure. We then discuss a mechanochemical mechanism that has the potential to unify our understanding of collagenous tissue assembly dynamics, which preferentially deposits and grows collagen fibrils directly in the path of mechanical force, where the energetics should be dissuasive and where collagen fibrils are most required. We term this mechanism: Mechanochemical force-structure causality. STATEMENT OF SIGNIFICANCE: Our mechanochemical-force structure causality postulate suggests that collagen molecules are components of mechanochemically-sensitive and dynamically-responsive fibrils. Collagen molecules assemble preferentially in the path of applied strain, can be grown in place by mechanical extension, and are retained in the path of force through strain-stabilization. The mechanisms that drive this behavior operate at the level of the molecules themselves and are encoded into the structure of the biomaterial. The concept might change our understanding of structure formation, enhance our ability to treat injuries, and accelerate the development of therapeutics to prevent pathologies such as fibrosis. We suggest that collagen is a mechanochemically responsive dynamic element designed to provide a substantial "material assist" in the construction of adaptive carriers of mechanical signals.

Segment-Long-Spacing (SLS) and the Polymorphic Structures of Fibrillar Collagen

The diverse and complex functions of collagen during the development of an organism are closely related to the polymorphism of its supramolecular structures in the extracellular matrix. SLS (segment-long-spacing) is one of the best understood alternative structures of collagen. SLS played an instrumental role in the original studies of collagen more than half a century ago that laid the foundation of nearly everything we know about collagen today. Despite being used mostly under in vitro conditions, the natural occurrence of SLS in tissues has also been reported. Here we will provide a brief overview of the major findings of the SLS and other structures of collagen based on a wealth of work published starting from the 1940s. We will discuss the factors that determine the stability and the structural specificity of the different molecular assemblies of collagen in light of the new studies using designed fibril forming collagen peptides. At the end of the chapter, we will summarize some recent discoveries of the alternative structures of collagen in tissues, especially those involved in pathogenic states. A revisit of SLS will likely inspire new understandings concerning the range of critical roles of fibrillar collagen in terms of its organizational diversity in the extracellular matrix.

Use of Exogenous Enzymes in Human Therapy: Approved Drugs and Potential Applications

The development of safe and efficacious enzyme-based human therapies has increased greatly in the last decades, thanks to remarkable advances in the understanding of the molecular mechanisms responsible for different diseases, and the characterization of the catalytic activity of relevant exogenous enzymes that may play a remedial effect in the treatment of such pathologies. Several enzyme-based biotherapeutics have been approved by FDA (the U.S. Food and Drug Administration) and EMA (the European Medicines Agency) and many are undergoing clinical trials. Apart from enzyme replacement therapy in human genetic diseases, which is not discussed in this review, approved enzymes for human therapy find applications in several fields, from cancer therapy to thrombolysis and the treatment, e.g., of clotting disorders, cystic fibrosis, lactose intolerance and collagen-based disorders. The majority of therapeutic enzymes are of microbial origin, the most convenient source due to fast, simple and cost-effective production and manipulation. The use of microbial recombinant enzymes has broadened prospects for human therapy but some hurdles such as high immunogenicity, protein instability, short half-life and low substrate affinity, still need to be tackled. Alternative sources of enzymes, with reduced side effects and improved activity, as well as genetic modification of the enzymes and novel delivery systems are constantly searched. Chemical modification strategies, targeted- and/or nanocarrier-mediated delivery, directed evolution and site-specific mutagenesis, fusion proteins generated by genetic manipulation are the most explored tools to reduce toxicity and improve bioavailability and cellular targeting. This review provides a description of exogenous enzymes that are presently employed for the therapeutic management of human diseases with their current FDA/EMA-approved status, along with those already experimented at the clinical level and potential promising candidates.

Surface-bound matrix metalloproteinase-8 on macrophages: Contributions to macrophage pericellular proteolysis and migration through tissue barriers

Objective

MMP‐8 binds to surface‐bound tissue inhibitor of metalloproteinase‐1 (TIMP‐1) on PMNs to promote pericellular proteolysis during the development of inflammatory diseases associated with tissue destruction. Little is known about the biology of MMP‐8 in macrophages. We tested the hypotheses that: (1) MMP‐8 and TIMP‐1 are also expressed on the surface of activated macrophages, (2) surface‐bound MMP‐8 on macrophages promotes TIMP‐resistant pericellular proteolysis and macrophage migration through tissue barriers, and (3) MMP‐8 binds to surface‐bound TIMP‐1 on macrophages.

Methods

Surface MMP‐8 and TIMP‐1 levels were measured on human monocyte‐derived macrophages (MDM) and/or murine macrophages using immunostaining, biotin‐labeling, and substrate cleavage methods. The susceptibility of membrane‐bound Mmp‐8 on activated macrophages from wild‐type (WT) mice to TIMPs was measured. Migration of WT and Mmp‐8^−/− macrophages through models of tissue barriers in vitro and the accumulation of peritoneal macrophages in WT versus Mmp‐8^−/− mice with sterile peritonitis was compared. Surface levels of Mmp‐8 were compared on activated macrophages from WT and Timp‐1^−/− mice.

Results

Lipopolysaccharides and a cluster of differentiation 40 ligand increased surface MMP‐8 and/or TIMP‐1 staining and surface type I collagenase activity on MDM and/or murine macrophages. Activated Mmp‐8^−/− macrophages degraded less type I collagen than activated WT macrophages. The surface type‐I collagenase activity on WT macrophages was resistant to inhibition by Timp‐1. Peritoneal macrophage accumulation was similar in WT and Mmp‐8^−/− mice with sterile acute peritonitis. However, Mmp‐8^−/− macrophages migrated less efficiently through models of tissue barriers (especially those containing type I collagen) than WT cells. Activated WT and Timp‐1^−/− macrophages had similar surface‐bound Mmp‐8 levels.

Conclusions

MMP‐8 and TIMP‐1 are expressed on the surface of activated human MDM and murine macrophages, but Mmp‐8 is unlikely to bind to surface‐bound Timp‐1 on these cells. Surface‐bound MMP‐8 contributes to TIMP‐resistant monocyte/macrophage pericellular proteolysis and macrophage migration through collagen‐containing tissue barriers.

Integrins as biomechanical sensors of the microenvironment

Integrins, and integrin-mediated adhesions, have long been recognized to provide the main molecular link attaching cells to the extracellular matrix (ECM) and to serve as bidirectional hubs transmitting signals between cells and their environment. Recent evidence has shown that their combined biochemical and mechanical properties also allow integrins to sense, respond to and interact with ECM of differing properties with exquisite specificity. Here, we review this work first by providing an overview of how integrin function is regulated from both a biochemical and a mechanical perspective, affecting integrin cell-surface availability, binding properties, activation or clustering. Then, we address how this biomechanical regulation allows integrins to respond to different ECM physicochemical properties and signals, such as rigidity, composition and spatial distribution. Finally, we discuss the importance of this sensing for major cell functions by taking cell migration and cancer as examples.

The significance of collagen dressings in wound management: a review

Clinical experience and research has improved our understanding of wound healing which, in turn, has enabled health professionals to aid wound healing and manufacturers to develop modern wound dressings. The significant role of collagen in wound healing has led to the development of numerous products on the basis of this biological material. The main focus of this review is to provide a critical appraisal of publications about collagen and acellular collagen dressings with a fleece-like or spongy structure. It is intended for clinicians and researchers, and aims to keep them up-to-date in the complex field of interactive, collagen-based wound dressings, including their manufacture, combination possibilities, mechanisms of action, performance in the promotion of wound healing and indications. Despite the small number of clinical studies, the importance of acellular collagen dressings with a fleece- or sponge-like structure is likely to increase in the future. As there is no ideal wound dressing, the knowledge attained is meant to support health professionals in selecting the right product, and pave the way for new applications and clinical studies.

Collagenolytic Enzymes and their Applications in Biomedicine

Nowadays, enzymatic therapy is a very promising line of treatment for many different diseases. There is a group of disorders and conditions, caused by fibrotic and scar processes and associated with the excessive accumulation of collagen that needs to be catabolized to normalize the connective tissue content. The human body normally synthesizes special extracellular enzymes, matrix metalloproteases (MMPs) by itself. These enzymes can cleave components of extracellular matrix (ECM) and different types of collagen and thus maintain the balance of the connective tissue components. MMPs are multifunctional enzymes and are involved in a variety of organism processes. However, under pathological conditions, the function of MMPs is not sufficient, and these enzymes fail to deal with disease. Thus, medical intervention is required. Enzymatic therapy is a very effective way of treating such collagen-associated conditions. It involves the application of exogenous collagenolytic enzymes that catabolize excessive collagen at the affected site and lead to the successful elimination of disease. Such collagenolytic enzymes are synthesized by many organisms: bacteria, animals (especially marine organisms), plants and fungi. The most studied and commercially available are collagenases from Clostridium histolyticum and from the pancreas of the crab Paralithodes camtschatica, due to their ability to effectively hydrolyse human collagen without affecting other tissues, and their wide pH ranges of collagenolytic activity. In the present review, we summarize not only the data concerning existing collagenase-based medications and their applications in different collagen-related diseases and conditions, but we also propose collagenases from different sources for their potential application in enzymatic therapy.

The contribution of Tannerella forsythia dipeptidyl aminopeptidase IV in the breakdown of collagen

In this study, we characterized a serine protease from Tannerella forsythia that degrades gelatin, type I, and III collagen. Tannerella forsythia is associated with periodontitis progression and severity. The primary goal of this research was to understand the mechanisms by which T. forsythia contributes to periodontitis progression. One of our previous metatranscriptomic analysis revealed that during periodontitis progression T. forsythia highly expressed the bfor_1659 ORF. The N-terminal end is homologous to dipeptidyl aminopeptidase IV (DPP IV). DPP IV is a serine protease that cleaves X-Pro or X-Ala dipeptide from the N-terminal end of proteins. Collagen type I is rich in X-Pro and X-Ala sequences, and it is the primary constituent of the periodontium. This work assessed the collagenolytic and gelatinolytic properties of BFOR_1659. To that end, the complete BFOR_1659 and its domains were purified as His-tagged recombinant proteins, and their collagenolytic activity was tested on collagen-like substrates, collagen type I and III combined, and on the extracellular matrix (ECM) formed on human gingival fibroblasts culture HGF-1. BFOR_1659 was only found in T. forsythia supernatants, highlighting its potential role on the pathogenicity of T. forsythia. We also found that BFOR_1659 efficiently degrades all tested substrates but the individual domains were inactive. Given that BFOR_1659 is highly expressed in the periodontal pocket, its clinical relevance is suggested to periodontitis progression.

Collagenolytic enzymes produced by fungi: a systematic review

Specific proteases capable of degrading native triple helical or denatured collagen have been required for many years and have a large spectrum of applications. There are few complete reports that fully uncover production, characterization and purification of fungi collagenases. In this review, authors searched through four scientific on line data bases using the following keywords (collagenolytic OR collagenase) AND (fungi OR fungus OR fungal) AND (production OR synthesis OR synthesize) AND (characterization). Scientific criteria were adopted in this review to classify found articles by score (from 0 to 10). After exclusion criteria, 21 articles were selected. None obtained the maximum of 10 points defined by the methodology, which indicates a deficiency in studies dealing simultaneously with production, characterization and purification of collagenase by fungi. Among microorganisms studied the non-pathogenic fungi Penicillium aurantiogriseum and Rhizoctonia solani stood out in volumetric and specific collagenase activity. The only article found that made sequencing of a true collagenase showed 100% homology with several metalloproteinases fungi. A clear gap in literature about collagenase production by fungi was verified, which prevents further development in the area and increases the need for further studies, particularly full characterization of fungal collagenases with high specificity to collagen.

Internal strain drives spontaneous periodic buckling in collagen and regulates remodeling

Fibrillar collagen, an essential structural component of the extracellular matrix, is remarkably resistant to proteolysis, requiring specialized matrix metalloproteinases (MMPs) to initiate its remodeling. In the context of native fibrils, remodeling is poorly understood; MMPs have limited access to cleavage sites and are inhibited by tension on the fibril. Here, single-molecule recordings of fluorescently labeled MMPs reveal cleavage-vulnerable binding regions arrayed periodically at ∼1-µm intervals along collagen fibrils. Binding regions remain periodic even as they migrate on the fibril, indicating a collective process of thermally activated and self-healing defect formation. An internal strain relief model involving reversible structural rearrangements quantitatively reproduces the observed spatial patterning and fluctuations of defects and provides a mechanism for tension-dependent stabilization of fibrillar collagen. This work identifies internal-strain-driven defects that may have general and widespread regulatory functions in self-assembled biological filaments.

In vitro analysis of the anticancer properties of scorpion venom in colorectal and breast cancer cell lines

Scorpion venom contains various types of proteins and peptides that are able to act as inhibitors of neurotransmitter molecules. This is achieved primarily via the inhibition of ion channels. In addition, scorpion venom has been demonstrated to exhibit anticancer properties in prostate and breast cancer, as well as leukemia. The anticancer properties of scorpion venom are due to its inhibitory effect on matrix metalloproteinase (MMP) activity, which leads to reduced motility and invasion in tumor cells. The inhibitory effects of venom on MMPs additionally lead to a reduction in the metastatic potential of malignant tumors. In the present study, the effect of venom obtained from a local serpentarium facility was examined in colorectal and breast cancer cell lines. Cell motility and clonogenic survival assays revealed a significant decrease (60-90%) in cell motility and colony formation, two significant hallmarks of cancer survival, following treatment with various concentrations of venom. These results were in agreement with previous studies demonstrating the anticancer activity of scorpion venom. In conclusion, the venom utilized at the Research Center of Prince Sultan Military Medical City Hospital (Riyadh, Saudi Arabia) possesses significant anticancer potential against colorectal and breast cancer cell lines.

Insights into Collagen Uptake by C-type Mannose Receptors from the Crystal Structure of Endo180 Domains 1-4

The C-type mannose receptor and its homolog Endo180 (or uPARAP, for urokinase plasminogen activator receptor-associated protein) mediate the endocytic uptake of collagen by macrophages and fibroblasts. This process is required for normal tissue remodeling, but also facilitates the growth and dissemination of tumors. We have determined the crystal structure at 2.5 Å resolution of the N-terminal region of Endo180, consisting of a ricin-like domain, a fibronectin type II (FN2) domain, and two C-type lectin (CTL) domains. The L-shaped arrangement of these domains creates a shallow trench spanning the FN2 and CTL1 domains, which was shown by mutagenesis to bind triple-helical and denatured collagen. Small-angle X-ray scattering showed that the L-shaped structure is maintained in solution at neutral and acidic pH, irrespective of calcium ion loading. Collagen binding was equally unaffected by acidic pH, suggesting that collagen release in endosomes is not regulated by changes within the Endo180 N-terminal region.

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Domains 1–4 of the endocytic receptor Endo180 form an L-shaped structure

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The fibronectin type II domain (domain 2) is crucial for collagen/gelatin binding

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The first C-type lectin domain (domain 3) also contributes to collagen binding

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Collagen binding to Endo180 domains 1–4 is not reduced by low pH or Ca²⁺ depletion

Emergence of a metalloproteinase / phospholipase A2 axis of systemic inflammation

We review select aspects of the biology of matrix metalloproteinases (MMPs) with a focus on the modulation of inflammatory responses by MMP-2. MMP-2 is a zinc- and calcium-dependent endoprotease with substrates including extracellular matrix proteins, vasoactive peptides and chemokines. Humans and mice with MMP-2 deficiency exhibit a predominantly inflammatory phenotype. Recent research shows that MMP-2 deficient mice display elevated activity of a secreted phospholipase A₂ in the heart. Additionally, MMP-2 deficient mice exhibit abnormally high prostaglandin E₂ levels in various organs (i.e., the heart, brain and liver), signs of inflammation and exacerbated lipopolysaccharide-induced fever. We briefly review the biology of sPLA₂ enzymes to propose the existence of a heart-centric MMP-2/sPLA₂ axis of systemic inflammation. Moreover, we postulate that PLA₂ activation is induced by chemokines, whose ability to signal inflammation is regulated in a tissue-specific fashion by MMPs. Thus, genetic and pharmacologically induced MMP-deficiencies can be expected to perturb PLA₂-mediated inflammatory mechanisms.

Elucidating the Uptake and Distribution of Nanoparticles in Solid Tumors via a Multilayered Cell Culture Model

Multicellular layers (MCLs) have previously been used to determine the pharmacokinetics of a variety of different cancer drugs including paclitaxel, doxorubicin, methotrexate, and 5-fluorouracil across a number of cell lines. It is not known how nanoparticles (NPs) navigate through the tumor microenvironment once they leave the tumor blood vessel. In this study, we used the MCL model to study the uptake and penetration dynamics of NPs. Gold nanoparticles (GNPs) were used as a model system to map the NP distribution within tissue-like structures. Our results show that NP uptake and transport are dependent on the tumor cell type. MDA-MB-231 tissue showed deeper penetration of GNPs as compared to MCF-7 one. Intracellular and extracellular distributions of NPs were mapped using CytoViva imaging. The ability of MCLs to mimic tumor tissue characteristics makes them a useful tool in assessing the efficacy of particle distribution in solid tumors.

Bacterial collagenases - A review

Bacterial collagenases are metalloproteinases involved in the degradation of the extracellular matrices of animal cells, due to their ability to digest native collagen. These enzymes are important virulence factors in a variety of pathogenic bacteria. Nonetheless, there is a lack of scientific consensus for a proper and well-defined classification of these enzymes and a vast controversy regarding the correct identification of collagenases. Clostridial collagenases were the first ones to be identified and characterized and are the reference enzymes for comparison of newly discovered collagenolytic enzymes. In this review we present the most recent data regarding bacterial collagenases and overview the functional and structural diversity of bacterial collagenases. An overall picture of the molecular diversity and distribution of these proteins in nature will also be given. Particular aspects of the different proteolytic activities will be contextualized within relevant areas of application, mainly biotechnological processes and therapeutic uses. At last, we will present a new classification guide for bacterial collagenases that will allow the correct and straightforward classification of these enzymes.

Profibrotic activities for matrix metalloproteinase-8 during bleomycin-mediated lung injury

Matrix metalloproteinase-8 (MMP-8) is a potent interstitial collagenase thought to be expressed mainly by polymorphonuclear neutrophils. To determine whether MMP-8 regulates lung inflammatory or fibrotic responses to bleomycin, we delivered bleomycin by the intratracheal route to wild-type (WT) versus Mmp-8(-/-) mice and quantified MMP-8 expression, and inflammation and fibrosis in the lung samples. Mmp-8 steady state mRNA and protein levels increase in whole lung and bronchoalveolar lavage samples when WT mice are treated with bleomycin. Activated murine lung fibroblasts express Mmp-8 in vitro. MMP-8 expression is increased in leukocytes in the lungs of patients with idiopathic pulmonary fibrosis compared with control lung samples. Compared with bleomycin-treated WT mice, bleomycin-treated Mmp-8(-/-) mice have greater lung inflammation, but reduced lung fibrosis. Whereas bleomycin-treated Mmp-8(-/-) and WT mice have similar lung levels of several pro- and antifibrotic mediators (TGF-β, IL-13, JE, and IFN-γ), Mmp-8(-/-) mice have higher lung levels of IFN-γ-inducible protein-10 (IP-10) and MIP-1α. Genetically deleting either Ip-10 or Mip-1α in Mmp-8(-/-) mice abrogates their lung inflammatory response to bleomycin, but reconstitutes their lung fibrotic response to bleomycin. Studies of bleomycin-treated Mmp-8 bone marrow chimeric mice show that both leukocytes and lung parenchymal cells are sources of profibrotic MMP-8 during bleomycin-mediated lung fibrosis. Thus, during bleomycin-mediated lung injury, MMP-8 dampens the lung acute inflammatory response, but promotes lung fibrosis by reducing lung levels of IP-10 and MIP-1α. These data indicate therapeutic strategies to reduce lung levels of MMP-8 may limit fibroproliferative responses to injury in the human lung.

Regulation of proteases after spinal cord injury

Spinal cord injury is a major medical problem worldwide. Unfortunately, we still do not have suitable therapeutic agents for the treatment of spinal cord injury and prevention of its devastating consequences. Scientists and physicians are baffled by the challenges of controlling progressive neurodegeneration in spinal cord injury, which has not been healed with any currently-available treatments. Although extensive work has been carried out to better understand the pathophysiology of spinal cord injury, our current understanding of the repair mechanisms of secondary injury processes is still meager. Several investigators reported the crucial role played by various proteases after spinal cord injury. Understanding the beneficial and harmful roles these proteases play after spinal cord injury will allow scientists to plan and design appropriate treatment strategies to improve functional recovery after spinal cord injury. This review will focus on various proteases such as matrix metalloproteinases, cysteine proteases, and serine proteases and their inhibitors in the context of spinal cord injury.

Suppression of matrix metalloproteinase-9 expression in undifferentiated, non-apoptotic keratinocytes is abrogated by the cleavage of poly(ADP-ribose) polymerase-1

Matrix metalloproteinase (MMP)-9, an enzyme that degrades the extracellular matrix, has been implicated as a key enzyme in the process of tissue remodeling. This study demonstrates the regulation of MMP-9 transcription through a gene regulatory element in its promoter (the KRE-M9 element). The KRE-M9-binding protein was purified and identified as poly(ADP-ribose) polymerase-1 (PARP-1), which inhibits the transcription of MMP-9 similar to involucrin. This regulation occurs in non-apoptotic keratinocytes using the distinctive culture conditions of high and low Ca(2+) levels. PARP cleavage, which occurs during apoptosis, results in de-repression of MMP-9 promoter activity. These data clarify a new role of PARP-1 and suggest a physiologically relevant connection between caspase activation and MMP-9 expression.

Nuclear localization of matrix metalloproteinases

Matrix metalloproteinases (MMPs) were originally identified as matrixin proteases that act in the extracellular matrix. Recent works have uncovered nontraditional roles for MMPs in the extracellular space as well as in the cytosol and nucleus. There is strong evidence that subspecialized and compartmentalized matrixins participate in many physiological and pathological cellular processes, in which they can act as both degradative and regulatory proteases. In this review, we discuss the transcriptional and translational control of matrixin expression, their regulation of intracellular sorting, and the structural basis of activation and inhibition. In particular, we highlight the emerging roles of various matrixin forms in diseases. The activity of matrix metalloproteinases is regulated at several levels, including enzyme activation, inhibition, complex formation and compartmentalization. Most MMPs are secreted and have their function in the extracellular environment. MMPs are also found inside cells, both in the nucleus, cytosol and organelles. The role of intracellular located MMPs is still poorly understood, although recent studies have unraveled some of their functions. The localization, activation and activity of MMPs are regulated by their interactions with other proteins, proteoglycan core proteins and / or their glycosaminoglycan chains, as well as other molecules. Complexes formed between MMPs and various molecules may also include interactions with noncatalytic sites. Such exosites are regions involved in substrate processing, localized outside the active site, and are potential binding sites of specific MMP inhibitors. Knowledge about regulation of MMP activity is essential for understanding various physiological processes and pathogenesis of diseases, as well as for the development of new MMP targeting drugs.

Matrix metalloproteinase-8 is involved in dermal nerve growth: implications for possible application to pruritus from in vitro models

Cutaneous nerve density is related to abnormal itch perception in dermatoses, such as atopic dermatitis and xerosis. However, the mechanisms underlying the elongation of dermal nerve fibers within the interstitial collagen (CoL) matrix are poorly understood. In this study, a culture system of rat dorsal root ganglion neurons consisting of type I CoL and a Boyden chamber containing a nerve growth factor (NGF) concentration gradient was used. Nerve fibers penetrating into type I CoL gel were observed in the presence of the NGF concentration gradient. Levels of matrix metalloproteinase-8 (MMP-8) mRNA and protein were increased in the cultured neurons and the conditioned medium, respectively. The nerve fiber penetration was dose dependently inhibited by MMP-8 blockers. Moreover, MMP-8 immunoreactivity was partially localized at growth cones in NGF-responsive nerve fibers. Semaphorin 3A stimulation also showed the opposite effects on these NGF-dependent events. Intriguingly, MMP-8 expression was upregulated by type I and III CoLs, which are substrates for this enzyme. These results suggested that MMP-8 is involved in sensory nerve growth within the interstitial CoL matrix through modulation by the axonal guidance molecules and/or extracellular matrix components. These findings provide insight into the development of pruritus involving skin nerve density.

Trends in matrix metalloproteinase research from 1986–2007: a bibliometric study

Using the SCI-expanded database, this study provides a quantitative description of the development of the research involving matrix metalloproteinase (MMP) over a period of 20 years. From 1986 to 2007 the scientific literature related to MMP increased sevenfold (397 papers in 1986–1987 and 2834 in 2006–2007). The number of countries participating in MMP-related research doubled during this period (33 in 1986–1987 to 67 in 2006–2007), and the USA continually remained the leader. Several industrialized nations (Japan, Germany, UK, Canada, and France) also continuously played important roles, with some emerging Asian countries joining the top 10 most productive countries in 2006–2007: China (ranked 5th), South Korea (6th), and Taiwan (10th). The MMP-related literature was distributed among a continuously growing number of journals (188 in 1986–1987, 527 in 1996–1997, and 913 in 2006–2007) and The Journal of Biological Chemistry remained the most prolific throughout the entire period. The development of the research involving MMPs during the past two decades was also characterized by a progressive transfer of interest from basic research to clinical medicine; cell biology and pharmacology were important routes of investigation generally pursued by researchers. Journals dedicated to oncology have progressively risen to the top 8 most prolific journals during the 20 year period analyzed.

Collagenase production by nematode-trapping fungi

A number of species of nematode-trapping fungi, which capture and digest nematodes having keratin and collagen in their cuticles, were tested for the ability to produce extracellular collagenase and keratinase. Collagenase, which is active on ichthyocol, earthworm collagen, and procollagen from chicken embryo fibroblasts, was found in the growth medium of all tested species; keratinase was not found. The enzyme from Arthrobotrys amerospora was concentrated by precipitation with (NH(4))(2)SO(4) and further purified by adsorption on collagen at 0 degrees C. The collagenase was active over a pH range of 2.5 to 10.0. It was not inactivated by dialysis against ethylenediaminetetraacetic acid for 48 h or by the sulfhydryl group inhibitors N-ethylmaleimide and p-chloromercuribenzoate. The production of collagenase may aid the fungus to penetrate the cuticle of its prey.

Analysing the role of endogenous matrix molecules in the development of osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis worldwide. In this condition, damage to the extracellular matrix (ECM) of cartilage occurs, resulting in joint destruction. Factors mediating cartilage damage include mechanical injury, cytokine and superoxide release on a background of genetic susceptibility and obesity. Studies of arthritic cartilage show increased production of ECM molecules including type II collagen, cartilage oligomeric matrix protein, fibronectin (FN) and fibromodulin. Recent reports suggest that ECM proteins may become endogenous catabolic factors during joint damage. Activation of pro-inflammatory pathways by ECM proteins has led to their description as damage-associated molecular patterns (DAMPs). The ECM proteins involved include fibromodulin, which activates the complement pathway and may promote the persistence of joint inflammation. Fragmentation of type II collagen, FN and hyaluronan reveals cryptic epitopes that stimulate proteolytic enzymes including matrix metalloproteinases and aggrecanases (ADAMTSs - a disintegrin and metalloproteinase with thrombospondin type 1 motifs). Proteolytic fragments also stimulate the release of nitric oxide, chemokines and cytokines and activation of the MAP kinases. Reports are emerging that the receptors for the fragments described involve interaction with integrins and toll-like receptors. In this review the contribution of endogenous ECM molecules to joint destruction will be discussed. A deeper understanding of the pathways stimulated by endogenous ligands could offer potential avenues for novel therapies in the future.

The Scar-in-a-Jar: studying potential antifibrotic compounds from the epigenetic to extracellular level in a single well

BACKGROUND AND PURPOSE

Fibrosis, a pathological accumulation of collagen in tissues, represents a major global disease burden. Effective characterization of potential antifibrotic drugs has been constrained by poor formation of the extracellular matrix in vitro, due to tardy procollagen processing by collagen C-proteinase/BMP-1, and difficulties in relating this matrix to cell numbers in experimental samples.

EXPERIMENTAL APPROACH

The Scar-in-a-Jar model provided, in vitro, the complete biosynthetic cascade of collagen matrix formation including complete conversion of procollagen by C-proteinase/BMP-1, its subsequent extracellular deposition and lysyl oxidase-mediated cross-linking, achieved by applying the biophysical principle of macromolecular 'crowding'. Collagen matrix deposition, velocity and morphology can be controlled using negatively charged 'crowders' in a rapid (2 days) mode or a mixture of neutral 'crowders' in an accelerated (6 days) mode. Combined with quantitative optical bioimaging, this novel system allows for in situ assessment of the area of deposited collagen(s) per cell.

KEY RESULTS

Optical evaluation of known and novel antifibrotic compounds effective at the epigenetic, post-transcriptional/translational/secretional level correlated excellently with corresponding biochemical analyses. Focusing on quantitation of deposited collagen, the Scar-in-a-Jar was most effective in assessing novel inhibitors that may have multiple targets, such as microRNA29c, found to be a promising antifibrotic agent.

CONCLUSIONS AND IMPLICATIONS

This novel screening system supersedes current in vitro fibroplasia models, as a fast, quantitative and non-destructive technique. This method distinguishes a reduction in collagen I deposition, excluding collagen cross-linking, and allows full evaluation of inhibitors of C-proteinase/BMP-1 and other matrix metalloproteinases.

Matrix metalloproteinases and their tissue inhibitors in endometrial remodelling and menstruation

The architecture of the human endometrium is extensively remodelled during the course of each normal menstrual cycle, unlike most other tissues and organs which undergo very little change during adult life. During menstruation, when loss of most of the functionalis layer occurs, there is concomitant epithelial regrowth; repair of the luminal surface is complete almost as bleeding ceases. During the proliferative phase of the cycle and under the influence of rising oestrogen levels, the stromal cells, glands and blood vessels undergo rapid proliferation which results in tissue thickening. Following ovulation (around day 14 of the idealized 28-day cycle), the secretory phase of the cycle is characterized by increasing tortuosity of the spiral arterioles and glands and increased glandular secretory activity. After about day 22, decidualization of many of the stromal fibroblasts also occurs, the resultant decidual cells having many characteristics typical of epithelial cells. Periods of tissue oedema are apparent both in mid-proliferative (days 8–11) and mid-secretory (days 20–23) endometrium. Late in the cycle, there is regression of the tissue as menstruation is initiated.

Assessment of local proteolytic milieu as a factor in tumor invasiveness and metastasis formation: in vitro collagen degradation and invasion assays

Matrix invasion by a tumor cell requires the degradation of components in the extracellular matrix (ECM) as one of the initial steps in the metastatic process. Tumors cells achieve ECM invasion primarily through the overexpression of matrix metalloproteinases (MMPs), a family of enzymes that function to degrade ECM proteins. In this chapter, an in vitro collagen degradation assay and a modified collagen invasion assay system are described. The collagen degradation assay is a simple method to measure the ability of tumor cells to degrade type I collagen, the main constituent of the stromal compartment, in a 3-D matrix environment. The modified collagen invasion assay system enables researchers to study the effects of transient overexpression and/or targeted knockdown (as with siRNAs) of a given gene on collagen invasion of tumor cells in a real-time format.

Membrane-type MMPs enable extracellular matrix permissiveness and mesenchymal cell proliferation during embryogenesis

Peri-cellular remodeling of mesenchymal extracellular matrices is considered a prerequisite for cell proliferation, motility and development. Here we demonstrate that membrane-type 3 MMP, MT3-MMP, is expressed in mesenchymal tissues of the skeleton and in peri-skeletal soft connective tissue. Consistent with this localization, MT3-MMP-deficient mice display growth inhibition tied to a decreased viability of mesenchymal cells in skeletal tissues. We document that MT3-MMP works as a major collagenolytic enzyme, enabling cartilage and bone cells to cleave high-density fibrillar collagen and modulate their resident matrix to make it permissive for proliferation and migration. Collectively, these data uncover a novel extracellular matrix remodeling mechanism required for proper function of mesenchymal cells. The physiological significance of MT3-MMP is highlighted in mice double deficient for MT1-MMP and MT3-MMP. Double deficiency transcends the combined effects of the individual single deficiencies and leads to severe embryonic defects in palatogenesis and bone formation incompatible with life. These defects are directly tied to loss of indispensable collagenolytic activities required in collagen-rich mesenchymal tissues for extracellular matrix remodeling and cell proliferation during embryogenesis.

Membrane type-1 matrix metalloproteinases and tissue inhibitor of metalloproteinases-2 RNA levels mimic each other during Xenopus laevis metamorphosis

Matrix metalloproteinases (MMPs) and their endogenous inhibitors TIMPs (tissue inhibitors of MMPs), are two protein families that work together to remodel the extracellular matrix (ECM). TIMPs serve not only to inhibit MMP activity, but also aid in the activation of MMPs that are secreted as inactive zymogens. Xenopus laevis metamorphosis is an ideal model for studying MMP and TIMP expression levels because all tissues are remodeled under the control of one molecule, thyroid hormone. Here, using RT-PCR analysis, we examine the metamorphic RNA levels of two membrane-type MMPs (MT1-MMP, MT3-MMP), two TIMPs (TIMP-2, TIMP-3) and a potent gelatinase (Gel-A) that can be activated by the combinatory activity of a MT-MMP and a TIMP. In the metamorphic tail and intestine the RNA levels of TIMP-2 and MT1-MMP mirror each other, and closely resemble that of Gel-A as all three are elevated during periods of cell death and proliferation. Conversely, MT3-MMP and TIMP-3 do not have similar RNA level patterns nor do they mimic the RNA levels of the other genes examined. Intriguingly, TIMP-3, which has been shown to have anti-apoptotic activity, is found at low levels in tissues during periods of apoptosis.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

Localized delivery of DNA to the cells by viral collagen-loaded silica colloidal crystals

Low-molecular-weight colloidal crystals with enhanced biocompatibility and ordered porous structure are used in drug-delivery systems. The objective of our study is to demonstrate the use of silica nanoscale colloid particles for localized recombinant DNA release. The colloids were coated with collagen-containing viral vector constructs of lentiviral green fluorescent protein (GFP), and solidified at 37°C. The colloid-collagen-viral vector platform (CCP) was transferred to cell monolayer cultures of human lung fibroblasts. Results show specific infection of cells directly beneath the platform, as evidenced by positive GFP in their cytoplasm, while neighboring cells show no cytoplasmic GFP. The infection of specific cells is probably due to the gradual release of viral particles from the collagen matrix by cell-secreted collagenase, which avoids overdosing the cells with viral particles, resulting from the cytopathic effect often seen with high-titer viral infection. Cells infected with the lentiviral-GFP or lentivirus alone, not incorporated into the colloid-collagen device, show caspase 3-associated apoptotic cell death. This suggests that colloidal crystal-coated collagen may be used as a powerful platform to deliver genes of choice to localized subgroups of specific cells of interest. This specificity in the delivery mode is beneficial for functional studies of gene-directed impact on a particular cell population of interest in a heterogeneous cell culture.

Matrix metalloproteinases and proteoglycans in axonal regeneration

After an injury to the adult mammalian central nervous system (CNS), a variety of growth-inhibitory molecules are upregulated. A glial scar forms at the site of injury and is composed of numerous molecular substances, including chondroitin sulfate proteoglycans (CSPGs). These proteoglycans inhibit axonal growth in vitro and in vivo. Matrix metalloproteinases (MMPs) can degrade the core protein of some CSPGs as well as other growth-inhibitory molecules such as Nogo and tenascin-C. MMPs have been shown to facilitate axonal regeneration in the adult mammalian peripheral nervous system (PNS). This review will focus on the various roles of proteoglycans and MMPs within the injured nervous system. First, we will present a general background on the injured central nervous system and explore the roles that proteoglycans play in the injured PNS and CNS. Second, we will discuss the various functions of MMPs within the injured PNS and CNS. Special attention will be paid to the possibility of how MMPs might modify the growth-inhibitory extracellular environment of the injured adult mammalian spinal cord and facilitate axonal regeneration in the CNS.

Chlorhexidine arrests subclinical degradation of dentin hybrid layers in vivo

The recent paradigm that endogenous collagenolytic and gelatinolytic activities derived from acid-etched dentin result in degradation of hybrid layers requires in vivo validation. This study tested the null hypothesis that there is no difference between the degradation of dentin bonded with an etch-and-rinse adhesive and that in conjunction with chlorhexidine, an MMP inhibitor, applied after phosphoric-acid-etching. Contralateral pairs of bonded Class I restorations in primary molars of clinical subjects were retrieved after a six-month period of intra-oral functioning and processed for transmission electron microscopy. Hybrid layers from the chlorhexidine-treated teeth exhibited normal structural integrity of the collagen network. Conversely, abnormal hybrid layers were seen in the control teeth, with progressive disintegration of the fibrillar network, to the extent that it was beyond detection by collagen staining. Self-destruction of collagen matrices occurs rapidly in resin-infiltrated dentin in vivo and may be arrested with the use of chlorhexidine as an MMP inhibitor.

Collagenase in cranial morphogenesis

Collagen is the most abundant extracellular matrix protein in connective tissues of higher animals. The growth of connective tissues is intimately linked to the ability to model and remodel the collagen-rich matrices of the organism at critical points during development and growth to allow expansion and adaptation of tissue interfaces. The mammalian cranium is one such place where collagen remodeling is required for proper growth, and this review explores the consequences of abrogated collagen remodeling as they materialize in a mouse model deficient for the membrane type 1 matrix metalloproteinase.

Keloid-derived fibroblasts show increased secretion of factors involved in collagen turnover and depend on matrix metalloproteinase for migration

BACKGROUND

A keloid is a specific skin lesion that expands beyond the boundaries of the original injury as it heals. Histologically, it is characterized by the excessive accumulation of collagen. However, the reasons for the expansion and the invasive nature of keloids remain unknown.

OBJECTIVES

We evaluated collagen degradation and migration by cultured keloid fibroblasts based on the assumption that these variables were of functional relevance to the expanding and invasive nature of keloid lesions.

METHODS

Collagen production was investigated by the detection of type 1 collagen (procollagen type 1C peptide: P1P). Matrix metalloproteinase (MMP)-1 (interstitial collagenase) and MMP-2 (gelatinase-A), were investigated as elements of the collagen degradation system. Enzyme immunoassays were performed to measure the production of P1P, MMP-1, MMP-2, and tissue inhibitor of metalloproteinase (TIMP)-1. To assess the production of MMP-2 its gelatinolytic activity was measured by zymography using gelatin-containing gels. The participation of transforming growth factor-beta1 (TGF-beta1) in the production and degradation of collagen was also investigated. Finally, the migratory activity of keloid fibroblasts was evaluated using a colony dispersion assay.

RESULTS

The production of type 1 collagen, MMP-1, MMP-2, and TIMP-1 by keloid fibroblasts was 3-fold, 6-fold, 2.4-fold, and 2-fold greater than that of normal dermal fibroblasts, respectively. Production of P1P was increased when TGF-beta1 was added to cultures of keloid fibroblasts, while it was decreased when anti-TGF-beta1 antibody was added to the cultures. In contrast, the production of MMP-1 was decreased by the addition of TGF-beta1 to cultured keloid fibroblasts, while it was increased when anti-TGF-beta1 antibody was added to the cultures. The production of MMP-2 increased after treatment with TGF-beta1, but did not change significantly when anti-TGF-beta1 antibody was added to the cultures. Production of TIMP-1 did not change significantly when either TGF-beta1 or anti-TGF-beta1 antibody was added to the cultures. Keloid fibroblasts showed a 2.5-fold increase of migratory activity compared with normal dermal fibroblasts, while the migratory activity of these fibroblasts was reduced to the control level by treatment with a broad-spectrum MMP inhibitor (GM 6001).

CONCLUSIONS

Cultured keloid fibroblasts showed increased production of collagen and MMPs, and TGF-beta1 played a role in this regulation of production. In addition, increased production of MMPs had a role in the high migratory activity of cultured keloid fibroblasts.

Expression and mechanical modulation of matrix metalloproteinase-1 and -2 genes in facial and cranial sutures

Craniofacial sutures create a soft tissue interface between various calvarial and facial bones. Facial and cranial sutures show differences in their surrounding anatomical structures and local mechanical strain environments. Despite previous attempts to identify the expression of matrix metalloproteinase genes (MMPs) in cranial sutures, little is known regarding whether facial and cranial sutures differ in MMP expression. We have investigated the expression of MMP-1 and MMP-2 in the pre-maxillomaxillary suture (PMS; facial suture) and the frontoparietal suture (FPS; cranial suture) in 32-day-old rats with or without the application of cyclic loading. Expression of MMP-1 and MMP-2 was detected by the reverse transcription/polymerase chain reaction technique. At 32 days of postnatal development (n=6), both MMP-1 and MMP-2 were reproducibly expressed in the facial PMS, in comparison with negligible MMP-1 and MMP-2 expression in the cranial FPS. In six age- and sex-matched control rats, cyclic loading at 4 Hz and 1000 mN was applied to the maxilla for two 20-min episodes within a 12-h interval. In some (but not all) cases, cyclic loading induced marked expression of MMP-1 and MMP-2 in the PMS and FPS in comparison with corresponding non-loaded controls. These data confirm our previous finding that short doses of cyclic loading upregulate MMP-2 expression in craniofacial sutures and suggest the possibility that facial and cranial sutures differ in matrix degradation rates during postnatal development.

Tadpole collagenase, the single parent of such a large family

This editorial review comments the development of the field of the matrix metalloproteinases that was initiated by the demonstration of the tadpole collagenase in 1962.

Expression of matrix metalloproteinase genes in the rat intramembranous bone during postnatal growth and upon mechanical stresses

A cranial suture consists of neural-crest derived cells and matrices between mineralized skull bones. Little is known regarding the involvement of matrix metalloproteinases (MMPs) in the degradation of extracellular matrix of cranial sutures. In the postnatal rat model, the posterior frontal suture (PFS) undergoes complete ossification between P12-P22, whereas the sagittal suture (SS) remains patent. The present study utilized reverse transcriptase-polymerase chain reaction (RT-PCR) to explore the expression of MMP-1 and MMP-2 genes in the PFS and SS in P8 and P32 rats, and also to determine whether these MMP genes are modulated by exogenous mechanical forces. RNA was isolated from P8 and P32 normal PFS and SS each by pooling sutural specimens from 14 to 20 rats. RT-PCR analysis and semi-quantitative luminosity demonstrated the expression of MMP-1 and MMP-2 genes in the patent P8 PFS, P8 SS, and P32 SS, but no apparent MMP-2 expression in the physiologically ossified P32 PFS. Exogenous cyclic forces applied to the maxilla at 1000 mN and 4 Hz elicited corresponding cyclic bone strain waveforms with peak strain of 134.14+/-38.15 muepsilon (mean+/-S.D.) for the PFS, and 28.35+/-10.86 muepsilon for the SS in P32 rats. These cyclic forces delivered for 20 min/d over 2 consecutive days induced the expression of MMP-2 gene in the physiologically fused P32 PFS that was not expressed without mechanical stresses. Taken together, these data suggest potentially important roles of MMP genes in the postnatal development of cranial sutures, and their susceptibility to mechanical stresses.

Membrane-bound matrix metalloproteinase-8 on activated polymorphonuclear cells is a potent, tissue inhibitor of metalloproteinase-resistant collagenase and serpinase

Little is known about the cell biology or the biologic roles of polymorphonuclear cell (PMN)-derived matrix metalloproteinase-8 (MMP-8). When activated with proinflammatory mediators, human PMN release only approximately 15-20% of their content of MMP-8 ( approximately 60 ng/10(6) cells) exclusively as latent pro-MMP-8. However, activated PMN incubated on type I collagen are associated with pericellular collagenase activity even when bathed in serum. PMN pericellular collagenase activity is attributable to membrane-bound MMP-8 because: 1) MMP-8 is expressed in an inducible manner in both pro- and active forms on the surface of human PMN; 2) studies of activated PMN from mice genetically deficient in MMP-8 (MMP-8(-/-)) vs wild-type (WT) mice show that membrane-bound MMP-8 accounts for 92% of the MMP-mediated, PMN surface type I collagenase activity; and 3) human membrane-bound MMP-8 on PMN cleaves types I and II collagens, and alpha(1)-proteinase inhibitor, but is substantially resistant to inhibition by tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2. Binding of MMP-8 to the PMN surface promotes its stability because soluble MMP-8 has t(1/2) = 7.5 h at 37 degrees C, but membrane-bound MMP-8 retains >80% of its activity after incubation at 37 degrees C for 18 h. Studies of MMP-8(-/-) vs WT mice given intratracheal LPS demonstrate that 24 h after intratracheal LPS, MMP-8(-/-) mice have 2-fold greater accumulation of PMN in the alveolar space than WT mice. Thus, MMP-8 has an unexpected, anti-inflammatory role during acute lung injury in mice. TIMP-resistant, active MMP-8 expressed on the surface of activated PMN is likely to be an important form of MMP-8, regulating lung inflammation and collagen turnover in vivo.

Collagenase unwinds triple-helical collagen prior to peptide bond hydrolysis

Breakdown of triple-helical interstitial collagens is essential in embryonic development, organ morphogenesis and tissue remodelling and repair. Aberrant collagenolysis may result in diseases such as arthritis, cancer, atherosclerosis, aneurysm and fibrosis. In vertebrates, it is initiated by collagenases belonging to the matrix metalloproteinase (MMP) family. The three-dimensional structure of a prototypic collagenase, MMP-1, indicates that the substrate-binding site of the enzyme is too narrow to accommodate triple-helical collagen. Here we report that collagenases bind and locally unwind the triple-helical structure before hydrolyzing the peptide bonds. Mutation of the catalytically essential residue Glu200 of MMP-1 to Ala resulted in a catalytically inactive enzyme, but in its presence noncollagenolytic proteinases digested collagen into typical 3/4 and 1/4 fragments, indicating that the MMP-1(E200A) mutant unwinds the triple-helical collagen. The study also shows that MMP-1 preferentially interacts with the alpha2(I) chain of type I collagen and cleaves the three alpha chains in succession. Our results throw light on the basic mechanisms that control a wide range of biological and pathological processes associated with tissue remodelling.

Pathogenesis of pterygia: role of cytokines, growth factors, and matrix metalloproteinases

Pterygium is a common ocular surface disease apparently only observed in humans. Chronic UV exposure is a widely accepted aetiological factor in the pathogenesis of this disease and this concept is supported by epidemiological data, ray tracing models and histopathological changes that share common features with UV damaged skin. The mechanism(s) of pterygium formation is incompletely understood. Recent data have provided evidence implicating a genetic component, anti-apoptotic mechanisms, cytokines, growth factors, extracellular matrix remodelling (through the actions of matrix metalloproteinases), immunological mechanisms and viral infections in the pathogenesis of this disease. In this review, the current knowledge on pterygium pathogenesis is summarised, highlighting recent developments. In addition, we provide novel data further demonstrating the complexity of this intriguing disease.

Mediation of transforming growth factor-beta(1)-stimulated matrix contraction by fibroblasts: a role for connective tissue growth factor in contractile scarring

Excessive cell-mediated tissue contraction after injury can lead to morbid contractile scarring in the body. In the eye this can cause blindness because of posterior capsule opacification, proliferative vitroretinopathy, failure of glaucoma filtration surgery, and corneal haze. During repair, transforming growth factor (TGF)-beta and connective tissue growth factor (CTGF) genes are co-ordinately expressed. Although TGF-beta and CTGF stimulate new matrix deposition, their role and regulation during contractile scarring is unknown. In this study, an in vitro model of collagen matrix contraction culminating from tractional forces generated by fibroblasts showed that both TGF-beta(1) and CTGF-stimulated contraction. Using a specific anti-sense oligodeoxynucleotide to CTGF the procontractile activity of TGF-beta(1) was found to be mediated by CTGF. During contraction fibroblasts produced similar levels of matrix metalloproteinases (MMPs)-2 and -9 with TGF-beta(1) or CTGF and a modest increase in MMP-1 with CTGF only (indicated by zymography and enzyme-linked immunosorbent assay). The requirement of MMPs for contraction was demonstrated using a broad-spectrum synthetic inhibitor. This study demonstrates a new function for CTGF in mediating matrix contraction by fibroblasts involving MMPs and suggests a novel regulatory mechanism for TGF-beta-stimulated contraction. Inhibition of CTGF activity or gene transcription could be a suitable target for anti-scarring therapies.

Cellular inflammatory response to porcine collagen membranes

OBJECTIVES

The purpose of this study was to assess local inflammatory changes associated with the implantation of three different porcine collagen membranes having potential use in periodontal regeneration.

METHODS

Materials were implanted subcutaneously into prepared sites along the dorsal skin surface of 60 female Wistar rats. Saline and turpentine were used as negative and positive controls, respectively. Animals were killed and biopsies obtained after 3 d, and at 1, 2, 4, 6, and 8 weeks after membrane implantation. A panel of six monoclonal antibodies was used to identify circulating monocytes (ED1), resident tissue macrophages (ED2), lymphoid macrophages (ED3), Ia-antigen expression (OX6), T-lymphocytes (OX19), and B-lymphocytes (OX33). Cells identified by each antibody were subjected to quantitative immunocytochemistry to compare any differences present among groups. Sera obtained 8 weeks after grafting were used in immunoblotting assays to detect the presence of systemic antiporcine antibodies.

RESULTS

We found that the mononuclear cell subsets associated with implantation of porcine collagen membranes were similar to those obtained with saline administration. On the other hand, the use of turpentine resulted in an inflammatory infiltrate characterized by significantly higher numbers of all six monoclonal cell subsets at all time periods evaluated, compared to either saline or any of the membranes (P < 0.001).

CONCLUSIONS

The collagen membranes do not appear to be associated with a significant local inflammatory response, nor a systemic immune response, and thus appear to be well tolerated, rendering them useful in periodontal regeneration.