Colon stroma mediates an inflammation-driven fibroblastic response controlling matrix remodeling and healing.

Chronic inflammation is often associated with the development of tissue fibrosis, but how mesenchymal cell responses dictate pathological fibrosis versus resolution and healing remains unclear. Defining stromal heterogeneity and identifying molecular circuits driving extracellular matrix deposition and remodeling stands to illuminate the relationship between inflammation, fibrosis, and healing. We performed single-cell RNA-sequencing of colon-derived stromal cells and identified distinct classes of fibroblasts with gene signatures that are differentially regulated by chronic inflammation, including IL-11-producing inflammatory fibroblasts. We further identify a transcriptional program associated with trans-differentiation of mucosa-associated fibroblasts and define a functional gene signature associated with matrix deposition and remodeling in the inflamed colon. Our analysis supports a critical role for the metalloprotease Adamdec1 at the interface between tissue remodeling and healing during colitis, demonstrating its requirement for colon epithelial integrity. These findings provide mechanistic insight into how inflammation perturbs stromal cell behaviors to drive fibroblastic responses controlling mucosal matrix remodeling and healing.

ADAM8 affects glioblastoma progression by regulating osteopontin-mediated angiogenesis.

Glioblastoma multiforme (GBM) is the most aggressive type of brain cancer with a median survival of only 15 months. To complement standard treatments including surgery, radiation and chemotherapy, it is essential to understand the contribution of the GBM tumor microenvironment. Brain macrophages and microglia particularly contribute to tumor angiogenesis, a major hallmark of GBM. ADAM8, a metalloprotease-disintegrin strongly expressed in tumor cells and associated immune cells of GBMs, is related to angiogenesis and correlates with poor clinical prognosis. However, the specific contribution of ADAM8 to GBM tumorigenesis remains elusive. Knockdown of ADAM8 in U87 glioma cells led to significantly decreased angiogenesis and tumor volumes of these cells after stereotactic injection into striate body of mice. We found that the angiogenic potential of ADAM8 in GBM cells and in primary macrophages is mediated by the regulation of osteopontin (OPN), an important inducer of tumor angiogenesis. By in vitro cell signaling analyses, we demonstrate that ADAM8 regulates OPN via JAK/STAT3 pathway in U87 cells and in primary macrophages. As ADAM8 is a dispensable protease for physiological homeostasis, we conclude that ADAM8 could be a tractable target to modulate angiogenesis in GBM with minor side-effects.

ADAM (a Disintegrin and Metalloproteinase) 15 Deficiency Exacerbates Ang II (Angiotensin II)-Induced Aortic Remodeling Leading to Abdominal Aortic Aneurysm.

OBJECTIVE: ADAM (a disintegrin and metalloproteinase) 15-a membrane-bound metalloprotease from the ADAM (disintegrin and metalloproteinase) family-has been linked to endothelial permeability, inflammation, and metastasis. However, its function in aortic aneurysm has not been explored. We aimed to determine the function of ADAM15 in the pathogenesis of aortic remodeling and aneurysm formation. Approach and Results: Male Adam15-deficient and WT (wild type) mice (10 weeks old), on standard laboratory diet, received Ang II (angiotensin II; 1.5 mg/kg per day) or saline (Alzet pump) for 2 or 4 weeks. Ang II increased ADAM15 in WT aorta, while Adam15-deficiency resulted in abdominal aortic aneurysm characterized by loss of medial smooth muscle cells (SMCs), elastin fragmentation, inflammation, but unaltered Ang II-mediated hypertension. In the abdominal aortic tissue and primary aortic SMCs culture, Adam15 deficiency decreased SMC proliferation, increased apoptosis, and reduced contractile properties along with F-actin depolymerization to G-actin. Ang II triggered a markedly greater increase in THBS (thrombospondin) 1 in Adam15-deficient aorta, primarily the medial layer in vivo, and in aortic SMC in vitro; increased SSH1 (slingshot homolog 1) phosphatase activity and cofilin dephosphorylation that promoted F-actin depolymerization and G-actin accumulation. rhTHBS1 (recombinant THBS1) alone was sufficient to activate the cofilin pathway, increase G-actin, and induce apoptosis of aortic SMCs, confirming the key role of THBS1 in this process. Further, in human abdominal aortic aneurysm specimens, decreased ADAM15 was associated with increased THBS1 levels and loss of medial SMCs. CONCLUSIONS: This study is the first to demonstrate a key role for ADAM15 in abdominal aortic aneurysm through regulating the SMC function, thereby placing ADAM15 in a critical position as a potential therapeutic target for abdominal aortic aneurysm.

Metalloprotease-Dependent Attenuation of BMP Signaling Restricts Cardiac Neural Crest Cell Fate.

In higher vertebrates, cephalic neural crest cells (NCCs) form craniofacial skeleton by differentiating into chondrocytes and osteoblasts. A subpopulation of cephalic NCCs, cardiac NCCs (CNCCs), migrates to the heart. However, CNCCs mostly do not yield skeletogenic derivatives, and the molecular mechanisms of this fate restriction remain elusive. We identify a disintegrin and metalloprotease 19 (Adam19) as a position-specific fate regulator of NCCs. Adam19-depleted mice abnormally form NCC-derived cartilage in their hearts through the upregulation of Sox9 levels in CNCCs. Moreover, NCC-lineage-specific Sox9-overexpressing mice recapitulate CNCC chondrogenesis. In vitro experiments show that Adam19 mediates the cleavage of bone morphogenic protein (BMP) type I receptor Alk2 (Acvr1), whereas pharmacogenetic approaches reveal that Adam19 inhibits CNCC chondrogenesis by suppressing the BMP-Sox9 cascade, presumably through processing Alk2. These findings suggest a metalloprotease-dependent mechanism attenuating cellular responsiveness to BMP ligands, which is essential for both the positional restriction of NCC skeletogenesis and normal heart development.

Notch1-ADAM8 positive feed-back loop regulates the degradation of chondrogenic extracellular matrix and osteoarthritis progression.

BACKGROUND: Osteoarthritis (OA) is one of the most prevalent joint disease, and there are still no effective therapeutic agents or clinical methods for the cure of this disease to date. The degradation of cartilage extracellular matrix (ECM) is a major cause of OA. METHOD: IL-1ß was used to induce chondrogenic degradation. Q-PCR and Western blotting were used to detect mRNA and protein level, respectively. ELISA was used to detect the secreted TNF-α and IL-6 level. Immunofluorescence was used to detect the protein level of Aggrecan, Collagen II and ki67. TUNEL and flow cytometry were used to examine cell apoptosis of chondrocytes. ChIP and luciferase assay were used to study molecular gene regulation. Osteoarthritic animal model and Safranin-O staining were used to determine the in vivo OA phenotype. RESULTS: The expression of ADAM8 was up-regulated in osteoarthritic chondrocytes. Knockdown of ADAM8 suppressed the OA phenotype in the in vitro OA cell model. ADAM8 regulated OA progression through the activation of EGFR/ERK/NF-κB signaling pathway. Inhibition of Notch signaling suppressed OA phenotype in the in vitro OA cell model. Notch signaling regulated the gene expression of ADAM8 directly via Hes1. Notch1-ADAM8 positive feedback loop promoted the progression of OA in vivo. CONCLUSION: Notch1-ADAM8 feed-back loop regulates the degradation of chondrogenic extracellular matrix and osteoarthritis progression.

ADAM-like Decysin-1 (ADAMDEC1) is a positive regulator of Epithelial Defense Against Cancer (EDAC) that promotes apical extrusion of RasV12-transformed cells.

Recent studies have revealed that newly emerging transformed cells are often eliminated from epithelia via cell competition with the surrounding normal epithelial cells. However, it remains unknown whether and how soluble factors are involved in this cancer preventive phenomenon. By performing stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative mass spectrometric analyses, we have identified ADAM-like Decysin-1 (ADAMDEC1) as a soluble protein whose expression is upregulated in the mix culture of normal and RasV12-transformed epithelial cells. Expression of ADAMDEC1 is elevated in normal epithelial cells co-cultured with RasV12 cells. Knockdown of ADAMDEC1 in the surrounding normal cells substantially suppresses apical extrusion of RasV12 cells, suggesting that ADAMDEC1 secreted by normal cells positively regulate the elimination of the neighboring transformed cells. In addition, we show that the metalloproteinase activity of ADAMDEC1 is dispensable for the regulation of apical extrusion. Furthermore, ADAMDEC1 facilitates the accumulation of filamin, a crucial regulator of Epithelial Defense Against Cancer (EDAC), in normal cells at the interface with RasV12 cells. This is the first report demonstrating that an epithelial intrinsic soluble factor is involved in cell competition in mammals.

A Disintegrin and Metalloprotease-22 Attenuates Hypertrophic Remodeling in Mice Through Inhibition of the Protein Kinase B Signaling Pathway.

BACKGROUND: Severe cardiac hypertrophy can lead to cardiac remodeling and even heart failure in the end, which is a leading cause of cardiovascular disease-related mortality worldwide. A disintegrin and metalloprotease-22 (ADAM22), a member of the transmembrane and secreted metalloendopeptidase family, participates in many biological processes, including those in the cardiovascular system. However, there is no explicit information on whether ADAM22 can regulate the process of cardiac hypertrophy; the effects that ADAM22 exerts in cardiac hypertrophy remain elusive. METHODS AND RESULTS: We observed significantly increased ADAM22 expression in failing hearts from patients with dilated cardiomyopathy and hypertrophic cardiomyopathy; the same trend was observed in mice induced by transaortic constriction and in neonatal rat cardiomyocytes treated by angiotensin II. Therefore, we constructed both cardiac-specific ADAM22 overexpression and knockout mice. At 4 weeks after transaortic constriction, cardiac-specific ADAM22 knockout, by the CRISPR/Cas9 (clustered regularly interspaced palindromic repeat (CRISPR)-Cas9) system, deteriorated the severity of cardiac hypertrophy in mice, whereas cardiac-specific ADAM22 overexpression mitigated the degrees of cardiac hypertrophy in mice. Similarly, altered ADAM22 expression modulated the angiotensin II-mediated cardiomyocyte hypertrophy in neonatal rat cardiomyocytes. After screening several signaling pathways, we found ADAM22 played a role in inhibition of protein kinase B (AKT) activation. Under the cardiac-specific ADAM22 knockout background, AKT activation was enhanced in transaortic constriction-induced mice and angiotensin II-stimulated neonatal rat cardiomyocytes, with a severe degree of cardiac hypertrophy. Treatment of a specific AKT inhibitor attenuated the transaortic constriction-enhanced AKT activation and cardiac hypertrophy in mice. CONCLUSIONS: The findings demonstrated that ADAM22 negatively regulates the AKT activation and the process of cardiac hypertrophy and may provide new insights into the pathobiological features of cardiac hypertrophy.

Whole body and hematopoietic ADAM8 deficiency does not influence advanced atherosclerotic lesion development, despite its association with human plaque progression.

Although A Disintegrin And Metalloproteinase 8 (ADAM8) is not crucial for tissue development and homeostasis, it has been implicated in various inflammatory diseases by regulating processes like immune cell recruitment and activation. ADAM8 expression has been associated with human atherosclerosis development and myocardial infarction, however a causal role of ADAM8 in atherosclerosis has not been investigated thus far. In this study, we examined the expression of ADAM8 in early and progressed human atherosclerotic lesions, in which ADAM8 was significantly upregulated in vulnerable lesions. In addition, ADAM8 expression was most prominent in the shoulder region of human atherosclerotic lesions, characterized by the abundance of foam cells. In mice, Adam8 was highly expressed in circulating neutrophils and in macrophages. Moreover, ADAM8 deficient mouse macrophages displayed reduced secretion of inflammatory mediators. Remarkably, however, neither hematopoietic nor whole-body ADAM8 deficiency in mice affected atherosclerotic lesion size. Additionally, except for an increase in granulocyte content in plaques of ADAM8 deficient mice, lesion morphology was unaffected. Taken together, whole body and hematopoietic ADAM8 does not contribute to advanced atherosclerotic plaque development, at least in female mice, although its expression might still be valuable as a diagnostic/prognostic biomarker to distinguish between stable and unstable lesions.

Deletion of ADAM-9 in HGF/CDK4 mice impairs melanoma development and metastasis.

ADAM-9 is a metalloproteinase expressed in peritumoral areas by invading melanoma cells and by adjacent peritumoral stromal cells; however, its function in stromal and melanoma cells is not fully understood. To address this question in vivo in a spontaneous melanoma model, we deleted ADAM-9 in mice carrying the hepatocyte growth factor (Hgf) transgene and knock-in mutation Cdk4R24C/R24C, demonstrated to spontaneously develop melanoma. Spontaneous melanoma arose less frequently in ADAM-9-deleted mice than in controls. Similarly reduced tumor numbers (although with faster growth kinetics) were detected upon induction of melanoma with 7,12-dimethylbenz[a]anthracene (DMBA). However, more lesions were induced at early time points in the absence of ADAM-9. Increased initial and decreased late tumor numbers were paralleled by altered tumor cell proliferation, but not apoptosis or inflammation. Importantly, significantly reduced lung metastases were detected upon ADAM-9 deletion. Using in vitro assays to address this effect mechanistically, we detected reduced adhesion and transmigration of ADAM-9-silenced melanoma cells to/through the endothelium. This implies that ADAM-9 functionally and cell autonomously mediates extravasation of melanoma cells. In vitro and in vivo we demonstrated that the basement membrane (BM) component laminin ß3-chain is a direct substrate of ADAM-9, thus contributing to destabilization and disruption of the BM barrier during invasion. In in vitro invasion assays using human melanoma cells and skin equivalents, depletion of ADAM-9 resulted in decreased invasion of the BM, which remained almost completely intact, as shown by continuous staining for laminin ß3-chain. Importantly, supplying soluble ADAM-9 to the system reversed this effect. Taken together, our data show that melanoma derived ADAM-9 autonomously contributes to melanoma progression by modulating cell adhesion to the endothelium and altering BM integrity by proteolytically processing the laminin-ß3 chain. This newly described process and ADAM-9 itself may represent potential targets for anti-tumor therapies.

ADAMTS3 activity is mandatory for embryonic lymphangiogenesis and regulates placental angiogenesis.

The only documented activity of a subclass of ADAMTS proteases comprising ADAMTS2, 3 and 14 is the cleavage of the aminopropeptide of fibrillar procollagens. A limited number of in vitro studies suggested that ADAMTS3 is mainly responsible for procollagen II processing in cartilage. Here, we created an ADAMTS3 knockout mouse (Adamts3(-/-)) model to determine in vivo the actual functions of ADAMTS3. Heterozygous Adamts3(+/-) mice were viable and fertile, but their intercrosses demonstrated lethality of Adamts3(-/-) embryos after 15 days of gestation. Procollagens I, II and III processing was unaffected in these embryos. However, a massive lymphedema caused by the lack of lymphatics development, an abnormal blood vessel structure in the placenta and a progressive liver destruction were observed. These phenotypes are most probably linked to dysregulation of the VEGF-C pathways. This study is the first demonstration that an aminoprocollagen peptidase is crucial for developmental processes independently of its primary role in collagen biology and has physiological functions potentially involved in several human diseases related to angiogenesis and lymphangiogenesis.

miR-203 suppresses the proliferation and metastasis of hepatocellular carcinoma by targeting oncogene ADAM9 and oncogenic long non-coding RNA HULC.

MicroRNAs (miRNAs) have been integrated into tumorigenic programs by regulating genes at post-transcriptional level. Long non-coding RNAs (lncRNAs) are novel targets for miRNAs. Here, we reported that miR-203 down-regulation was closely linked to advanced clinical features and poor overall survival (OS) of patients with hepatocellular carcinoma. We also confirmed that miR-203 and oncogene ADAM9 (a disintegrin and metalloproteinase 9)/oncogenic long non-coding RNA HULC (highly up-regulated in liver cancer) were inversely expressed in hepatocellular carcinoma (HCC) tissues or cell lines. More intriguingly, up-regulation of miR-203 diminished the expression of ADAM9 and HULC in HCC cancer cells. Over-expression of miR-203 could markedly inhibit cell proliferation, invasion and induce cell apoptosis. Furthermore, we identified that miR-203 modulated ADAM9 and HULC in a novel post-transcriptional regulatory mechanism. Over-expression of HULC partly rescued the miR-203-mediated antitumor effects. These results suggested that miR-203 played tumor suppressive roles by downregulating ADAM9 and HULC and indicated its potential application in cancer treatment.

Cytokine secretion and NK cell activity in human ADAM17 deficiency.

Genetic deficiencies provide insights into gene function in humans. Here we describe a patient with a very rare genetic deficiency of ADAM17. We show that the patient's PBMCs had impaired cytokine secretion in response to LPS stimulation, correlating with the clinical picture of severe bacteremia from which the patient suffered. ADAM17 was shown to cleave CD16, a major NK killer receptor. Functional analysis of patient's NK cells demonstrated that his NK cells express normal levels of activating receptors and maintain high surface levels of CD16 following mAb stimulation. Activation of individual NK cell receptors showed that the patient's NK cells are more potent when activated directly by CD16, albeit no difference was observed in Antibody Depedent Cytotoxicity (ADCC) assays. Our data suggest that ADAM17 inhibitors currently considered for clinical use to boost CD16 activity should be cautiously applied, as they might have severe side effects resulting from impaired cytokine secretion.

MiR-33a suppresses breast cancer cell proliferation and metastasis by targeting ADAM9 and ROS1.

MicroRNAs (miRNAs) are small noncoding RNAs that have a pivotal role in the post-transcriptional regulation of gene expression by sequence-specifically targeting multiple mRNAs. Although miR-33a was recently reported to play an important role in lipid homeostasis, atherosclerosis, and hepatic fibrosis, the functions of miR-33a in tumor progression and metastasis are largely unknown. Here, we found that downregulated miR-33a in breast cancer tissues correlates with lymph node metastasis. MiR-33a expression is significantly lower in the highly metastatic breast cancer cell lines than the noncancerous breast epithelial cells and non-metastatic breast cancer cells. Moreover, the overexpression of miR-33a in metastatic breast cancer cells remarkably decreases cell proliferation and invasion in vitro and significantly inhibits tumor growth and lung metastasis in vivo, whereas its knockdown in non-metastatic breast cancer cells significantly enhances cell proliferation and invasion in vitro and promotes tumor growth and lung metastasis in vivo. Combining bioinformatics prediction and biochemical analyses, we showed that ADAM9 and ROS1 are direct downstream targets of miR-33a. These findings identified miR-33a as a negative regulator of breast cancer cell proliferation and metastasis.

Impact of severe ADAMTS13 deficiency on clinical presentation and outcomes in patients with thrombotic microangiopathies: the experience of the Harvard TMA Research Collaborative.

The Harvard TMA Research Collaborative is a multi-institutional registry-based effort to study thrombotic microangiopathies (TMA). Laboratory and clinical parameters were recorded for 254 cases of suspected autoimmune thrombotic thrombocytopenic purpura (TTP). Patients with severe ADAMTS13 deficiency (activity ≤10%, N = 68) were more likely to be young, female and without a history of cancer treatment or transplantation. While all patients with severe deficiency were diagnosed with autoimmune TTP, those without severe deficiency frequently had disseminated intravascular coagulation, drug-associated TMA and transplant-related TMA. Patients with severe ADAMTS13 deficiency had superior overall survival at 360 d compared to those without severe deficiency (93·0% vs. 47·5%, P < 0·0001). Almost all patients with severe deficiency received therapeutic plasma exchange (TPE), but the use of TPE in patients with ADAMTS13 activity >10% varied significantly across the institutions in our consortium (13·2-63·8%, P < 0·0001). Nevertheless, 90-d mortality was not different in patients with ADAMTS13 activity >10% between the three hospitals (P = 0·98). Our data show that patients with severe ADAMTS13 deficiency represent a clinically distinct cohort that responds well to TPE. In contrast, TMA without severe ADAMTS13 deficiency is associated with increased mortality that may not be influenced by TPE.

Dysbiosis and Staphylococcus aureus Colonization Drives Inflammation in Atopic Dermatitis.

Staphylococcus aureus skin colonization is universal in atopic dermatitis and common in cancer patients treated with epidermal growth factor receptor inhibitors. However, the causal relationship of dysbiosis and eczema has yet to be clarified. Herein, we demonstrate that Adam17(fl/fl)Sox9-(Cre) mice, generated to model ADAM17-deficiency in human, developed eczematous dermatitis with naturally occurring dysbiosis, similar to that observed in atopic dermatitis. Corynebacterium mastitidis, S. aureus, and Corynebacterium bovis sequentially emerged during the onset of eczematous dermatitis, and antibiotics specific for these bacterial species almost completely reversed dysbiosis and eliminated skin inflammation. Whereas S. aureus prominently drove eczema formation, C. bovis induced robust T helper 2 cell responses. Langerhans cells were required for eliciting immune responses against S. aureus inoculation. These results characterize differential contributions of dysbiotic flora during eczema formation, and highlight the microbiota-host immunity axis as a possible target for future therapeutics in eczematous dermatitis.

The procollagen N-proteinases ADAMTS2, 3 and 14 in pathophysiology.

Collagen fibers are the main components of most of the extracellular matrices where they provide a structural support to cells, tissues and organs. Fibril-forming procollagens are synthetized as individual chains that associate to form homo- or hetero-trimers. They are characterized by the presence of a central triple helical domain flanked by amino and carboxy propeptides. Although there are some exceptions, these two propeptides have to be proteolytically removed to allow the almost spontaneous assembly of the trimers into collagen fibrils and fibers. While the carboxy-propeptide is mainly cleaved by proteinases from the tolloid family, the amino-propeptide is usually processed by procollagen N-proteinases: ADAMTS2, 3 and 14. This review summarizes the current knowledge concerning this subfamily of ADAMTS enzymes and discusses their potential involvement in physiopathological processes that are not directly linked to fibrillar procollagen processing.

Loss of ADAM17 is associated with severe multiorgan dysfunction.

ADAM metallopeptidase domain 17 (ADAM17) is responsible for processing large numbers of proteins. Recently, 1 family involving 2 patients with a homozygous mutation in ADAM17 were described, presenting with skin lesions and diarrhea. In this report, we describe a second family confirming the existence of this syndrome. The proband presented with severe diarrhea, skin rash, and recurrent sepsis, eventually leading to her death at the age of 10 months. We performed exome sequencing and detailed pathological and immunological investigations. We identified a novel homozygous frameshift mutation in ADAM17 (NM_003183.4:c.308dupA) leading to a premature stop codon. CD4(+) and CD8(+) T-cell stimulation assays showed severely diminished tumor necrosis factor-α and interleukin-2 production. Skin biopsies indicated a focal neutrophilic infiltrate and spongiotic dermatitis. Interestingly, the patient developed unexplained systolic hypertension and nonspecific hepatitis with apoptosis. This report provides evidence for an important role of ADAM17 in human immunological response and underscores its multiorgan involvement.

Myeloid A disintegrin and metalloproteinase domain 10 deficiency modulates atherosclerotic plaque composition by shifting the balance from inflammation toward fibrosis.

A disintegrin and metalloproteinase domain 10 (ADAM10) is a metalloprotease involved in cleavage of various cell surface molecules, such as adhesion molecules, chemokines, and growth factor receptors. Although we have previously shown an association of ADAM10 expression with atherosclerotic plaque progression, a causal role of ADAM10 in atherosclerosis has not been investigated. Bone marrow from conditional knockout mice lacking Adam10 in the myeloid lineage or from littermate controls was transplanted into lethally irradiated low density lipoprotein receptor Ldlr(-/-) mice on an atherogenic diet. Myeloid Adam10 deficiency did not affect plaque size, but it increased plaque collagen content. Matrix metalloproteinase 9 and 13 expression and matrix metalloproteinase 2 gelatinase activity were significantly impaired in Adam10-deficient macrophages, whereas their capacity to stimulate collagen production was unchanged. Furthermore, relative macrophage content in advanced atherosclerotic lesions was decreased. In vitro, Adam10-deficient macrophages showed reduced migration toward monocyte chemoattractant protein-1 and transmigration through collagen. In addition, Adam10-deficient macrophages displayed increased anti-inflammatory phenotype with elevated IL-10, and reduced production of proinflammatory tumor necrosis factor, IL-12, and nitric oxide in response to lipopolysaccharide. These data suggest a critical role of Adam10 for leukocyte recruitment, inflammatory mediator production, and extracellular matrix degradation. Thereby, myeloid ADAM10 may play a causal role in modulating atherosclerotic plaque stability.

Knockout of Adamts7, a novel coronary artery disease locus in humans, reduces atherosclerosis in mice.

BACKGROUND: Genome-wide association studies have established ADAMTS7 as a locus for coronary artery disease in humans. However, these studies fail to provide directionality for the association between ADAMTS7 and coronary artery disease. Previous reports have implicated ADAMTS7 in the regulation of vascular smooth muscle cell migration, but a role for and the direction of impact of this gene in atherogenesis have not been shown in relevant model systems. METHODS AND RESULTS: We bred an Adamts7 whole-body knockout mouse onto both the Ldlr and Apoe knockout hyperlipidemic mouse models. Adamts7(-/-)/Ldlr(-/-) and Adamts7(-/-)/Apoe(-/-) mice displayed significant reductions in lesion formation in aortas and aortic roots compared with controls. Adamts7 knockout mice also showed reduced neointimal formation after femoral wire injury. Adamts7 expression was induced in response to injury and hyperlipidemia but was absent at later time points, and primary Adamts7 knockout vascular smooth muscle cells showed reduced migration in the setting of tumor necrosis factor-α stimulation. ADAMTS7 localized to cells positive for smooth muscle cell markers in human coronary artery disease lesions, and subcellular localization studies in cultured vascular smooth muscle cells placed ADAMTS7 at the cytoplasm and cell membrane, where it colocalized with markers of podosomes. CONCLUSIONS: These data represent the first in vivo experimental validation of the association of Adamts7 with atherogenesis, likely through modulation of vascular cell migration and matrix in atherosclerotic lesions. These results demonstrate that Adamts7 is proatherogenic, lending directionality to the original genetic association and supporting the concept that pharmacological inhibition of ADAMTS7 should be atheroprotective in humans, making it an attractive target for novel therapeutic interventions.

ADAM17 limits the expression of CSF1R on murine hematopoietic progenitors.

All-lymphoid progenitors (ALPs) yield few myeloid cells in vivo, but readily generate such cells in vitro. The basis for this difference remains unknown. We hypothesized that ALPs limit responsiveness to in vivo concentrations of myeloid-promoting cytokines by reducing expression of the corresponding receptors, potentially through posttranscriptional mechanisms. Consistent with such a mechanism, ALPs express higher levels of CSF1R transcripts than their upstream precursors, yet show limited cell-surface protein expression of colony-stimulating factor 1 receptor (CSF1R). All-lymphoid progenitors and other hematopoietic progenitors deficient in A disintegrin and metalloproteinase domain 17 (ADAM17), display elevated cell surface CSF1R expression. ADAM17(-/-) ALPs, however, fail to yield myeloid cells upon transplantation into irradiated recipients. Moreover, ADAM17(-/-) ALPs yield fewer macrophages in vitro than control ALPs at high concentrations of macrophage colony stimulating factor. Mice with hematopoietic-specific deletion of ADAM17 have normal numbers of myeloid and lymphoid progenitors and mature cells in vivo. These data demonstrate that ADAM17 limits CSF1R protein expression on hematopoietic progenitors, but that compensatory mechanisms prevent elevated CSF1R levels from altering lymphoid progenitor potential.