Mouse models of MMP and TIMP function

Exposure to atrazine and endosulfan alters oviductal adenogenesis in the broad-snouted caiman (Caiman latirostris)

The molecular pathways involved in oviductal adenogenesis are highly conserved among vertebrates. In this work, we study the histomorphological changes and molecular pathways involved in Caiman latirostris oviductal adenogenesis and the effects of in ovo exposure to environmentally relevant doses of endosulfan (END) and atrazine (ATZ) on these processes. To this end, the histomorphological changes at epithelial and subepithelial compartments, the protein expressions of β-catenin and Wnt-7a, and the gene expression of metalloproteinases (MMPs) and its inhibitors (TIMPs) were evaluated as biomarkers of oviductal adenogenesis in prepubertal juvenile C. latirostris. Exposure to END altered adenogenesis-related epithelium characteristics and mRNA expression of MMP2, MMP9, and TIMP1. Exposure to ATZ increased the width of the subepithelial stroma with loosely arranged collagen fibers and increased β-catenin expression in buds (invaginated structures that precede glands). The results demonstrate that in ovo exposure to ATZ and END alters oviductal adenogenesis at tissue, cellular, and molecular levels. An altered oviductal adenogenesis could impair fertility, raising concern on the effects of pesticide pollution in wildlife and domestic animals.

Redefining metalloproteases specificity through network proteolysis

Proteolytic processes on cell surfaces and extracellular matrix (ECM) sustain cell behavior and tissue integrity in health and disease. Matrix metalloproteases (MMPs) and a disintegrin and metalloproteases (ADAMs) remodel cell microenvironments through irreversible proteolysis of ECM proteins and cell surface bioactive molecules. Pan-MMP inhibitors in inflammation and cancer clinical trials have encountered challenges due to promiscuous activities of MMPs. Systems biology advances revealed that MMPs initiate multifactorial proteolytic cascades, creating new substrates, activating or suppressing other MMPs, and generating signaling molecules. This review highlights the intricate network that underscores the role of MMPs beyond individual substrate-enzyme activities. Gaining insight into MMP function and tissue specificity is crucial for developing effective drug discovery strategies and novel therapeutics. This requires considering the dynamic cellular processes and consequences of network proteolysis.

Therapeutic Potential of the Molecular Chaperone and Matrix Metalloproteinase Inhibitor Clusterin for Dry Eye

Evidence is presented herein supporting the potential of the natural homeostatic glycoprotein CLU (clusterin) as a novel therapeutic for the treatment of dry eye. This idea began with the demonstration that matrix metalloproteinase MMP9 is required for damage to the ocular surface in mouse dry eye. Damage was characterized by degradation of OCLN (occludin), a known substrate of MMP9 and a key component of the paracellular barrier. Following up on this finding, a yeast two-hybrid screen was conducted using MMP9 as the bait to identify other proteins involved. CLU emerged as a strong interacting protein that inhibits the enzymatic activity of MMP9. Previously characterized as a molecular chaperone, CLU is expressed prominently by epithelia at fluid-tissue interfaces and secreted into bodily fluids, where it protects cells and tissues against damaging stress. It was demonstrated that CLU also protects the ocular surface in mouse dry eye when applied topically to replace the natural protein depleted from the dysfunctional tears. CLU is similarly depleted from tears in human dry eye. The most novel and interesting finding was that CLU binds selectively to the damaged ocular surface. In this position, CLU protects against epithelial cell death and barrier proteolysis, and dampens the autoimmune response, while the apical epithelial cell layer is renewed. When present at high enough concentration, CLU also blocks staining by vital dyes used clinically to diagnose dry eye. None of the current therapeutics have this combination of properties to "protect, seal, and heal". Future work will be directed towards human clinical trials to investigate the therapeutic promise of CLU.

Dysregulation of fibrosis related genes in HCV induced liver disease

BACKGROUND

Liver fibrosis results from a wound healing response to chronic injury, which leads to excessive matrix deposition. Genome wide association studies have showen transcriptional dysregulation in mild and severe liver fibrosis. Recent studies suggested that genetic markers may be able to define the exact stage of liver fibrosis.

AIM

To define genes or genetic pathways that could serve as markers for staging or as therapeutic targets to halt progression of liver fibrosis.

METHODS

The study was performed on 105 treatment naïve HCV genotype 4 infected patients [F0-F2, n = 56; F3-F4, n = 49] and 16 healthy subjects. The study included PCR array on 84 fibrosis related genes followed by customization of a smaller array consisting of 11 genes that were designed on the bases of results obtained from the larger array. Genes that displayed significant dysregulation at mRNA levels were validated at protein levels.

RESULTS AND DISCUSSION

Two major pathways exhibited high dysregulation in early fibrosis as compared with controls or when compared with late fibrosis, these were the TGFβ - related pathway genes and Matrix - deposition associated genes. Hepatic stellate cell (HSC) activators i.e. TGFβ pathway genes [TGFβ1, 2 and 3, their receptors TGFβR1 and 2, signaling molecules SMAD genes and PDGF growth factors] were considerably over-expressed at transcriptional levels as early as F0, whereas expression of their inhibitor TGIF1 was simultaneously down regulated. Matrix proteins including collagen and MMPs were upregulated in early fibrosis whereas tissue inhibitors TIMPs 1 and 2 began over expression in late fibrosis. Expression at protein levels was concordant with RNA data excluding dysregulation at post transcriptional levels.

CONCLUSION

Since these 2 gene sets are closely interrelated regarding HSC activation and proliferation, we assume that the current findings suggest that they are favorable targets to further search for stage specific markers.

Matrix metalloproteinases in emphysema

Several studies have implicated a causative role for specific matrix metalloproteinases (MMPs) in the development and progression of cigarette smoke-induced chronic obstructive pulmonary disease (COPD) and its severe sequela, emphysema. However, the precise function of any given MMP in emphysema remains an unanswered question. Emphysema results from the degradation of alveolar elastin - among other possible mechanisms - a process that is often thought to be caused by elastolytic proteinases made by macrophages. In this article, we discuss the data suggesting, supporting, or refuting causative roles of macrophage-derived MMPs, with a focus on MMPs-7, -9, -10, -12, and 28, in both the human disease and mouse models of emphysema. Findings from experimental models suggest that some MMPs, such as MMP-12, may directly breakdown elastin, whereas others, particularly MMP-10 and MMP-28, promote the development of emphysema by influencing the proteolytic and inflammatory activities of macrophages.

Matrix metalloproteinase-10 regulates stemness of ovarian cancer stem-like cells by activation of canonical Wnt signaling and can be a target of chemotherapy-resistant ovarian cancer

Epithelial ovarian cancer (EOC) is one of the most lethal cancers in females. Cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) have been reported to be origin of primary and recurrent cancers and to be resistant to several treatments. In this study, we identified matrix metalloproteinase-10 (MMP10) is expressed in CSCs/CICs of EOC. An immunohistochemical study revealed that a high expression level of MMP10 is a marker for poor prognosis and platinum resistance in multivariate analysis. MMP10 gene overexpression experiments and MMP10 gene knockdown experiments using siRNAs revealed that MMP10 has a role in the maintenance of CSCs/CICs in EOC and resistance to platinum reagent. Furthermore, MMP10 activate canonical Wnt signaling by inhibiting noncanonical Wnt signaling ligand Wnt5a. Therefore, MMP10 is a novel marker for CSCs/CICs in EOC and that targeting MMP10 is a novel promising approach for chemotherapy-resistant CSCs/CICs in EOC.

The Balance Between Metalloproteinases and TIMPs: Critical Regulator of Microvascular Endothelial Cell Function in Health and Disease

Endothelial cells (EC), especially the microvascular EC (MVEC), have critical functions in health and disease. For example, healthy MVEC provide a barrier between the fluid and protein found within the blood, and the surrounding tissue. Following tissue injury or infection, the microvascular barrier is often disrupted due to activation and dysfunction of the MVEC. Multiple mechanisms promote MVEC activation and dysfunction, including stimulation by cytokines, mechanical interaction with activated leukocytes, and exposure to harmful leukocyte-derived molecules, which collectively result in a loss of MVEC barrier function. However, MVEC activation is also critical to facilitate recruitment of inflammatory cells, such as neutrophils (PMNs) and monocytes, into the injured or infected tissue. Metalloproteinases, including the matrix metalloproteinases (MMPs) and the closely related, a disintegrin and metalloproteinases (ADAMs), have been implicated in regulating both MVEC barrier function, through cleavage of adherens and tight junctions proteins between adjacent MVEC and through degradation of the extracellular matrix, as well as PMN-MVEC interaction, through shedding of cell surface PMN receptors. Moreover, the tissue inhibitors of metalloproteinases (TIMPs), which collectively inhibit most MMPs and ADAMs, are critical regulators of MVEC activation and dysfunction through their ability to inhibit metalloproteinases and thereby promote MVEC stability. However, TIMPs have been also found to modulate MVEC function through metalloproteinase-independent mechanisms, such as regulation of vascular endothelial growth factor signaling. This chapter is focused on examining the role of the metalloproteinases and TIMPs in regulation of MVEC function in both health and disease.

Matrix Metalloproteinases and Leukocyte Activation

As their name implies, matrix metalloproteinases (MMPs) are thought to degrade extracellular matrix proteins, a function that is indeed performed by some members. However, regardless of their cell source, matrix degradation is not the only function of these enzymes. Rather, individual MMPs have been shown to regulate specific immune processes, such as leukocyte influx and migration, antimicrobial activity, macrophage activation, and restoration of barrier function, typically by processing a range of nonmatrix protein substrates. Indeed, MMP expression is low under steady-state conditions but is markedly induced during inflammatory processes including infection, wound healing, and cancer. Increasing research is showing that MMPs are not just a downstream consequence of a generalized inflammatory process, but rather are critical factors in the overall regulation of the pattern, type, and duration of immune responses. This chapter outlines the role of leukocytes in tissue remodeling and describes recent progress in our understanding of how MMPs alter leukocyte activity.

Tissue inhibitor of metalloproteinases 3-dependent microvascular endothelial cell barrier function is disrupted under septic conditions

Sepsis is associated with dysfunction of microvascular endothelial cells (MVEC) leading to tissue edema and multiple organ dysfunction. Metalloproteinases can regulate MVEC function through processing of cell surface proteins, and tissue inhibitor of metalloproteinases 3 (TIMP3) regulates metalloproteinase activity in the lung following injury. We hypothesize that TIMP3 promotes normal pulmonary MVEC barrier function through inhibition of metalloproteinase activity. Naive Timp3(-/-) mice had significantly higher basal pulmonary microvascular Evans blue (EB) dye-labeled albumin leak vs. wild-type (WT) mice. Additionally, cecal-ligation/perforation (CLP)-induced sepsis significantly increased pulmonary microvascular EB-labeled albumin leak in WT but not Timp3(-/-) mice. Similarly, PBS-treated isolated MVEC monolayers from Timp3(-/-) mice displayed permeability barrier dysfunction vs. WT MVEC, evidenced by lower transendothelial electrical resistance and greater trans-MVEC flux of fluorescein-dextran and EB-albumin. Cytomix (equimolar interferon γ, tumor necrosis factor α, and interleukin 1β) treatment of WT MVEC induced significant barrier dysfunction (by all three methods), and was associated with a time-dependent decrease in TIMP3 mRNA and protein levels. Additionally, basal Timp3(-/-) MVEC barrier dysfunction was associated with disrupted MVEC surface VE-cadherin localization, and both barrier dysfunction and VE-cadherin localization were rescued by treatment with GM6001, a synthetic metalloproteinase inhibitor. TIMP3 promotes normal MVEC barrier function, at least partially, through inhibition of metalloproteinase-dependent disruption of adherens junctions, and septic downregulation of TIMP3 may contribute to septic MVEC barrier dysfunction.

Mammary gland development: cell fate specification, stem cells and the microenvironment

The development of the mammary gland is unique: the final stages of development occur postnatally at puberty under the influence of hormonal cues. Furthermore, during the life of the female, the mammary gland can undergo many rounds of expansion and proliferation. The mammary gland thus provides an excellent model for studying the ‘stem/progenitor’ cells that allow this repeated expansion and renewal. In this Review, we provide an overview of the different cell types that constitute the mammary gland, and discuss how these cell types arise and differentiate. As cellular differentiation cannot occur without proper signals, we also describe how the tissue microenvironment influences mammary gland development.

Matrix metalloproteinase 2 is required for ovulation and corpus luteum formation in Drosophila

Ovulation is critical for successful reproduction and correlates with ovarian cancer risk, yet genetic studies of ovulation have been limited. It has long been thought that the mechanism controlling ovulation is highly divergent due to speciation and fast evolution. Using genetic tools available in Drosophila, we now report that ovulation in Drosophila strongly resembles mammalian ovulation at both the cellular and molecular levels. Just one of up to 32 mature follicles per ovary pair loses posterior follicle cells (“trimming”) and protrudes into the oviduct, showing that a selection process prefigures ovulation. Follicle cells that remain after egg release form a “corpus luteum (CL)” at the end of the ovariole, develop yellowish pigmentation, and express genes encoding steroid hormone biosynthetic enzymes that are required for full fertility. Finally, matrix metalloproteinase 2 (Mmp2), a type of protease thought to facilitate mammalian ovulation, is expressed in mature follicle and CL cells. Mmp2 activity is genetically required for trimming, ovulation and CL formation. Our studies provide new insights into the regulation of Drosophila ovulation and establish Drosophila as a model for genetically investigating ovulation in diverse organisms, including mammals.

Sexual reproduction is thought to be a highly divergent process due to fast evolution and speciation. For example, sperm from one species can seldom fertilize eggs from another species, indicating that different molecular machinery for fertilization is applied in different species. In contrast to this divergent view, ovulation, the process of liberating mature eggs from the ovary, is a general phenomenon throughout the Metazoa. We provide evidence that basic mechanisms of ovulation are conserved. Like mammalian follicles, Drosophila follicles consist of single oocytes surrounded by a layer of follicle cells. Drosophila follicles degrade their posterior follicle cells to allow the oocyte to rupture into the oviduct during ovulation. The residual postovulatory follicles reside in the ovary, accumulate yellowish pigmentation, and produce the steroid hormone ecdysone, features which resemble the mammalian corpus luteum. We also showed that matrix metalloproteinase, a type of proteinase proposed to degrade the mammalian follicle wall during ovulation, is required in Drosophila for posterior follicle cell degradation and ovulation. These findings are particularly important because this simple genetic model system will speed up the identification of many conserved regulators required for regulating matrix metalloproteinase activity and ovulation in human, processes that influence ovarian cancer formation and cancer metastasis.

Matrix metalloproteinases in fish biology and matrix turnover

Matrix metalloproteinases have important functions for tissue turnover in fish, with relevance both for the fish industry and molecular and cellular research on embryology, inflammation and tissue repair. These metalloproteinases have been studied in different fish types, subjected to both aquaculture and experimental conditions. This review highlights studies on these metalloproteinases in relation to both fish quality and health and further, the future importance of fish for basic research studies.

Diverse functions of matrix metalloproteinases during fibrosis

Fibrosis--a debilitating condition that can occur in most organs - is characterized by excess deposition of a collagen-rich extracellular matrix (ECM). At first sight, the activities of proteinases that can degrade matrix, such as matrix metalloproteinases (MMPs), might be expected to be under-expressed in fibrosis or, if present, could function to resolve the excess matrix. However, as we review here, some MMPs are indeed anti-fibrotic, whereas others can have pro-fibrotic functions. MMPs modulate a range of biological processes, especially processes related to immunity and tissue repair and/or remodeling. Although we do not yet know precisely how MMPs function during fibrosis--that is, the protein substrate or substrates that an individual MMP acts on to effect a specific process--experiments in mouse models demonstrate that MMP-dependent functions during fibrosis are not limited to effects on ECM turnover. Rather, data from diverse models indicate that these proteinases influence cellular activities as varied as proliferation and survival, gene expression, and multiple aspects of inflammation that, in turn, impact outcomes related to fibrosis.

Tissue inhibitor of metalloproteinases (TIMPs) in heart failure

Remodeling of the myocardium and the extracellular matrix (ECM) occurs in heart failure irrespective of its initial cause. The ECM serves as a scaffold to provide structural support as well as housing a number of cytokines and growth factors. Hence, disruption of the ECM will result in structural instability as well as activation of a number of signaling pathways that could lead to fibrosis, hypertrophy, and apoptosis. The ECM is a dynamic entity that undergoes constant turnover, and the integrity of its network structure is maintained by a balance in the function of matrix metalloproteinases (MMPs) and their inhibitors, the tissue inhibitor of metalloproteinases (TIMPs). In heart disease, levels of MMPs and TIMPs are altered resulting in an imbalance between these two families of proteins. In this review, we will discuss the structure, function, and regulation of TIMPs, their MMP-independent functions, and their role in heart failure. We will review the knowledge that we have gained from clinical studies and animal models on the contribution of TIMPs in the development and progression of heart disease. We will further discuss how ECM molecules and regulatory genes can be used as biomarkers of disease in heart failure patients.

Lack of MMP10 exacerbates experimental colitis and promotes development of inflammation-associated colonic dysplasia

Inflammatory bowel diseases (IBD) such as ulcerative colitis (UC) represent serious health burdens because of both the tissue-damaging disease itself and an elevated risk of colon cancer. The increased expression of many members of the matrix metalloproteinase (MMP) family of enzymes that occurs in colitis has long been associated with the destructive nature of the disease. Recent findings in cancer and other MMP-associated diseases, however, led us to question whether MMPs are indeed detrimental in the setting of colitis. Here, we focus on a single MMP family member, MMP10, and assess its role in a murine model of colonic tissue damage induced by dextran sulfate sodium (DSS) treatment. Using mice genetically deficient for MMP10, we find that absence of this enzyme leads to significantly worse disease scores and failure to resolve inflammation even after extended recovery periods. We show that MMP10 is produced predominantly by infiltrating myeloid cells in both murine and human colitis. Through bone marrow transplant experiments, we confirm that bone marrow-derived MMP10 contributes to colitis severity. Mice lacking MMP10 have a significantly higher propensity for development of dysplastic lesions in the colon after two rounds of DSS exposure. Thus, we conclude that MMP10 is required for resolution of DSS-induced colonic damage, and in its absence, chronic inflammation and ultimately dysplasia occurs.

Effect of dietary β carotene on cerebral aneurysm and subarachnoid haemorrhage in the brain apo E-/- mice

Atherosclerosis will lead to stenosis/occlusion in the lumen of various arteries of living body. This can lead various conditions including myocardial infarction, cerebral infarction/aneurysm and peripheral artery disease. Ang II is believed to be an important regulatory peptide involved in maintaining cardiovascular homeostasis and pathogenesis of various cardiovascular diseases. Matrix metalloproteinase's (MMPs), adhesion molecules and plasminogen systems are involved in the inflammatory reaction of various blood vessels as well as pathogenesis of cerebro vasuclar disease in apo E(-/-) mice during angiotensin II injection. The present study analyses the role of ang II in development of cerebral aneurysm and also evaluated the mRNA levels of MMPs, adhesion molecules, plasminogen systems and peroxisome proliferators-associated receptors in the brain of apo E(-/-) mouse during the progression of cerebral aneurysm and ischemic conditions. Also, this study evaluates the role of dietary β carotene on cerebrovascular disease. Serum total cholesterol (TC), Low density lipoprotein (LDL) and triglyceride (TG) levels were significantly increased in angiotensin II treated animals and further β carotene supplementation reduces TC but does not affect the triglyceride and LDL levels. Circulating levels of macrophages were significantly increased in angiotensin treated animals and further beta carotene supplementation significantly reduced the circulating macrophages. Cerebro meningeous aneurysm, subarachnoid haemorrhage, multiple foci of infarction, necrosis and infiltration of inflammatory cells were observed in the cerebral hemispheres of ang II treated animals, however, infarction size were reduced and no aneurysm, inflammatory foci was observed in β carotene treated animals. Real time analysis showed down regulation of mRNA levels of MMP 2, uPA, PAI, PPAR-A, MCSF1 and up regulation of tPA and MCP-1 in the brain during the progression of cerebral aneurysm and β carotene supplementation to bring to normal expression levels of all the candidate genes for cerebrovascular diseases. Based on above results, Ang II may induced cerebral aneurysm, ischemia/infarction on brain through RAS system by down regulating the mRNA levels of MMP 2, uPA, PAI, PPAR-A, MCSF1 and up regulating tPA and MCP-1 and β carotene attenuates the disease condition and bring down to normal expression levels of above genes.

Analysis of the MMP-dependent and independent functions of tissue inhibitor of metalloproteinase-2 on the invasiveness of breast cancer cells

Matrix metalloproteinases (MMPs) are secreted endopeptidases that play an essential role in remodeling the extracellular matrix (ECM). MMPs are primarily active during development, when the majority of ECM remodeling events occurs. In adults, elevated MMP activity has been observed in many pathological conditions such as cancer and osteoarthritis. The proteolytic activity of MMPs is controlled by their natural inhibitors - the tissue inhibitor of metalloproteinases (TIMPs). In addition to blocking MMP-mediated proteolysis, TIMPs have a number of MMP-independent functions including binding to cell surface proteins thereby stimulating signaling cascades. TIMP-2, the most studied member of the family, can both inhibit and activate MMPs directly, as well as inhibit MMP activity indirectly by upregulating expression of RECK, a membrane anchored MMP regulator. While TIMP-2 has been shown to play important roles in breast cancer, we describe how the MMP-independent effects of TIMP-2 can modulate the invasiveness of MCF-7, T47D and MDA-MB-231 breast cancer cells. Using an ALA + TIMP-2 mutant which is devoid of MMP inhibition, but still capable of initiating specific cell signaling cascades, we show that TIMP-2 can differentially affect MMP activity and cellular invasiveness in both an MMP dependent and independent manner. More specifically, MMP activity and invasiveness is increased with the addition of exogenous TIMP-2 in poorly invasive cell lines whereas it is decreased in highly invasive cells lines (MDA-MB-231). Conversely, the addition of ALA + TIMP-2 resulted in decreased invasiveness regardless of cell line.

Mannose receptor 2 attenuates renal fibrosis

Mannose receptor 2 (Mrc2) expresses an extracellular fibronectin type II domain that binds to and internalizes collagen, suggesting that it may play a role in modulating renal fibrosis. Here, we found that Mrc2 levels were very low in normal kidneys but subsets of interstitial myofibroblasts and macrophages upregulated Mrc2 after unilateral ureteral obstruction (UUO). Renal fibrosis and renal parenchymal damage were significantly worse in Mrc2-deficient mice. Similarly, Mrc2-deficient Col4α3(-/-) mice with hereditary nephritis had significantly higher levels of total kidney collagen, serum BUN, and urinary protein than Mrc2-sufficient Col4α3(-/-) mice. The more severe phenotype seemed to be the result of reduced collagen turnover, because procollagen III (α1) mRNA levels and fractional collagen synthesis in the wild-type and Mrc2-deficient kidneys were similar after UUO. Although Mrc2 associates with the urokinase receptor, differences in renal urokinase activity did not account for the increased fibrosis in the Mrc2-deficient mice. Treating wild-type mice with a cathepsin inhibitor, which blocks proteases implicated in Mrc2-mediated collagen degradation, worsened UUO-induced renal fibrosis. Cathepsin mRNA profiles were similar in Mrc2-positive fibroblasts and macrophages, and Mrc2 genotype did not alter relative cathepsin mRNA levels. Taken together, these data establish an important fibrosis-attenuating role for Mrc2-expressing renal interstitial cells and suggest the involvement of a lysosomal collagen turnover pathway.

From buds to follicles: matrix metalloproteinases in developmental tissue remodeling during feather morphogenesis

Organogenesis involves a series of dynamic morphogenesis and remodeling processes. Since feathers exhibit complex forms, we have been using the feather as a model to analyze how molecular pathways and cellular events are used. While several major molecular pathways have been studied, the roles of matrix degrading proteases and inhibitors in feather morphogenesis are unknown. Here we addressed this knowledge gap by studying the temporal and spatial expression of proteases and inhibitors in developing feathers using mammalian antibodies that cross react with chicken proteins. We also investigated the effect of protease inhibitors on feather development employing an in vitro feather bud culture system. The results show that antibodies specific for mammalian MMP2 and TIMP2 stained positive in both feather epithelium and mesenchyme. The staining co-localized in structures of E10-E13 developing feathers. Interestingly, MMP2 and TIMP2 exhibited a complementary staining pattern in developing E15 and E20 feathers and in maturing feather filaments. Although they exhibited a slight delay in feather bud development, similar patterns of MMP2 and TIMP2 staining were observed in in vitro culture explants. The broad spectrum pharmacological inhibitors AG3340 and BB103 (MMP inhibitors) but not Aprotinin (a plasmin inhibitor) showed a reversible effect on epithelium invagination and feather bud elongation. TIMP2, a physiological inhibitor to MMPs, exhibited a similar effect. Markers of feather morphogenesis showed that MMP activity was required for both epithelium invagination and mesenchymal cell proliferation. Inhibition of MMP activity led to an overall delay in the expression of molecules that regulate either early feather bud growth and/or differentiation and thereby produced abnormal buds with incomplete follicle formation. This work demonstrates that MMPs and their inhibitors are not only important in injury repair, but also in development tissue remodeling as demonstrated here for the formation of feather follicles.

Cleavage of E-Cadherin by Matrix Metalloproteinase-7 Promotes Cellular Proliferation in Nontransformed Cell Lines via Activation of RhoA

Perturbations in cell-cell contact machinery occur frequently in epithelial cancers and result in increased cancer cell migration and invasion. Previously, we demonstrated that MMP-7, a protease implicated in mammary and intestinal tumor growth, can process the adherens junction component E-cadherin. This observation leads us to test whether MMP-7 processing of E-cadherin could directly impact cell proliferation in nontransformed epithelial cell lines (MDCK and C57MG). Our goal was to investigate the possibility that MMP-7 produced by cancer cells may have effects on adjacent normal epithelium. Here, we show that MMP-7 processing of E-cadherin mediates, (1) loss of cell-cell contact, (2) increased cell migration, (3) a loss of epithelial cell polarization and (4) increased cell proliferation via RhoA activation. These data demonstrate that MMP-7 promotes epithelial cell proliferation via the processing of E-cadherin and provide insights into the molecular mechanisms that govern epithelial cell growth.