Microfibril-associated glycoprotein 2 (MAGP2) loss of function has pleiotropic effects in vivo

Loci cg06256735 and cg15815843 in the MFAP5 gene regulatory regions are hypomethylated in varicose veins apparently due to active demethylation

Varicose vein disease (VVD) is a common health problem worldwide. Microfibril-associated protein 5 (MFAP5) is one of the potential key players in its pathogenesis. Our previous microarray analysis revealed the cg06256735 and cg15815843 loci in the regulatory regions of the MFAP5 gene as hypomethylated in varicose veins which correlated with its up-regulation. The aim of this work was to validate preliminary microarray data, estimate the level of 5-hydroxymethylcytosine (5hmC) at these loci, and determine the methylation status of one of them in different layers of the venous wall. For this, methyl- and hydroxymethyl-sensitive restriction techniques were used followed by real-time PCR and droplet digital PCR, correspondingly, as well as bisulfite pyrosequencing of +/- oxidized DNA. Our microarray data on hypomethylation at the cg06256735 and cg15815843 loci in whole varicose vein segments were confirmed and it was also demonstrated that the level of 5hmC at these loci is increased in VVD. Specifically, among other layers of the venous wall, tunica (t.) intima is the main contributor to hypomethylation at the cg06256735 locus in varicose veins. Thus, it was shown that hypomethylation at the cg06256735 and cg15815843 loci takes place in VVD, with evidence to suggest that it happens through their active demethylation leading to up-regulation of the MFAP5 gene, and t. intima is most involved in this biochemical process.

MAGP2 promotes osteogenic differentiation during fracture healing through its crosstalk with the β-catenin pathway

Osteogenic differentiation is important for fracture healing. Microfibrial-associated glycoprotein 2 (MAGP2) is found to function as a proangiogenic regulator in bone formation; however, its role in osteogenic differentiation during bone repair is not clear. Here, a mouse model of critical-sized femur fracture was constructed, and the adenovirus expressing MAGP2 was delivered into the fracture site. Mice with MAGP2 overexpression exhibited increased bone mineral density and bone volume fraction (BV/TV) at Day 14 postfracture. Within 7 days postfracture, overexpression of MAGP2 increased collagen I and II expression at the fracture callus, with increasing chondrogenesis. MAGP2 inhibited collagen II level but elevated collagen I by 14 days following fracture, accompanied by increased endochondral bone formation. In mouse osteoblast precursor MC3T3-E1 cells, MAGP2 treatment elevated the expression of osteoblastic factors (osterix, BGLAP and collagen I) and enhanced ALP activity and mineralization through activating β-catenin signaling after osteogenic induction. Besides, MAGP2 could interact with lipoprotein receptor-related protein 5 (LRP5) and upregulated its expression. Promotion of osteogenic differentiation and β-catenin activation mediated by MAGP2 was partially reversed by LRP5 knockdown. Interestingly, β-catenin/transcription factor 4 (TCF4) increased MAGP2 expression probably by binding to MAGP2 promoter. These findings suggest that MAGP2 may interact with β-catenin/TCF4 to enhance β-catenin/TCF4's function and activate LRP5-activated β-catenin signaling pathway, thus promoting osteogenic differentiation for fracture repair. mRNA sequencing identified the potential targets of MAGP2, providing novel insights into MAGP2 function and the directions for future research.

Hyperoxia prevents the dynamic neonatal increases in lung mesenchymal cell diversity

Rapid expansion of the pulmonary microvasculature through angiogenesis drives alveolarization, the final stage of lung development that occurs postnatally and dramatically increases lung gas-exchange surface area. Disruption of pulmonary angiogenesis induces long-term structural and physiologic lung abnormalities, including bronchopulmonary dysplasia, a disease characterized by compromised alveolarization. Although endothelial cells are primary determinants of pulmonary angiogenesis, mesenchymal cells (MC) play a critical and dual role in angiogenesis and alveolarization. Therefore, we performed single cell transcriptomics and in-situ imaging of the developing lung to profile mesenchymal cells during alveolarization and in the context of lung injury. Specific mesenchymal cell subtypes were present at birth with increasing diversity during alveolarization even while expressing a distinct transcriptomic profile from more mature correlates. Hyperoxia arrested the transcriptomic progression of the MC, revealed differential cell subtype vulnerability with pericytes and myofibroblasts most affected, altered cell to cell communication, and led to the emergence of Acta1 expressing cells. These insights hold the promise of targeted treatment for neonatal lung disease, which remains a major cause of infant morbidity and mortality across the world.

MFAP5 variant-induced multiple giant thoracic aortic aneurysm

Heritable thoracic aortic aneurysms are complex conditions characterised by the dilation or rupture of the thoracic aorta, often occurring as an autosomal-dominant disorder associated with life-threatening complications. In this case report, we present a de novo variant, MFAP5 c.236_237insA (p.N79Kfs9), which is implicated in the development of inherited thoracic aortic aneurysm. The proband, a 15-year-old male, presented with recurrent cough, dull chest pain, chest distress, vomiting, and reduced activity tolerance, leading to the diagnosis of heritable thoracic aortic aneurysms. Whole-exome sequencing identified a novel heterozygous variant in MFAP5 (NM_003480, c.236_237insA, and p.N79Kfs9). MutationTester and PolyPhen-s predicted this variant to be damaging and disease-causing (probability = 1), while the SFIT score indicated protein damage (0.001). Structural analysis using the AlphaFold Protein structure database revealed that this mutation disrupted the N-linked glycosylation site, resulting in a frameshift, amino acid sequence alteration, and truncation of an essential protein site. To our knowledge, this is the first case report describing a young patient with heritable thoracic aortic aneurysm carrying the novel MFAP5 c.236_237insA (p.N79Kfs*9) variant. This variant represents the third identified mutation site associated with heritable thoracic aortic aneurysm. Given the high mortality and morbidity rates associated with thoracic aortic aneurysms, the prevention of severe and fatal complications is crucial in the clinical management of this condition. Our case highlights the importance of whole-exome sequencing and genetic screening in identifying potential pathogenic or likely pathogenic variants, particularly in early-onset patients with aortic dilation, to inform appropriate management strategies.

A genomic perspective of the aging human and mouse lung with a focus on immune response and cellular senescence

BACKGROUND

The aging lung is a complex process and influenced by various stressors, especially airborne pathogens and xenobiotics. Additionally, a lifetime exposure to antigens results in structural and functional changes of the lung; yet an understanding of the cell type specific responses remains elusive. To gain insight into age-related changes in lung function and inflammaging, we evaluated 89 mouse and 414 individual human lung genomic data sets with a focus on genes mechanistically linked to extracellular matrix (ECM), cellular senescence, immune response and pulmonary surfactant, and we interrogated single cell RNAseq data to fingerprint cell type specific changes.

RESULTS

We identified 117 and 68 mouse and human genes linked to ECM remodeling which accounted for 46% and 27%, respectively of all ECM coding genes. Furthermore, we identified 73 and 31 mouse and human genes linked to cellular senescence, and the majority code for the senescence associated secretory phenotype. These cytokines, chemokines and growth factors are primarily secreted by macrophages and fibroblasts. Single-cell RNAseq data confirmed age-related induced expression of marker genes of macrophages, neutrophil, eosinophil, dendritic, NK-, CD4+, CD8+-T and B cells in the lung of aged mice. This included the highly significant regulation of 20 genes coding for the CD3-T-cell receptor complex. Conversely, for the human lung we primarily observed macrophage and CD4+ and CD8+ marker genes as changed with age. Additionally, we noted an age-related induced expression of marker genes for mouse basal, ciliated, club and goblet cells, while for the human lung, fibroblasts and myofibroblasts marker genes increased with age. Therefore, we infer a change in cellular activity of these cell types with age. Furthermore, we identified predominantly repressed expression of surfactant coding genes, especially the surfactant transporter Abca3, thus highlighting remodeling of surfactant lipids with implications for the production of inflammatory lipids and immune response.

CONCLUSION

We report the genomic landscape of the aging lung and provide a rationale for its growing stiffness and age-related inflammation. By comparing the mouse and human pulmonary genome, we identified important differences between the two species and highlight the complex interplay of inflammaging, senescence and the link to ECM remodeling in healthy but aged individuals.

Genetic Overlap of Spontaneous Dissection of Either the Thoracic Aorta or the Coronary Arteries

Ascending thoracic aortic dissection (ATAD) is a well-known vascular cause of sudden death. Spontaneous coronary artery dissections (SCAD) are emerging as an important cause of early-onset myocardial infarction and sudden death. Genetic variants in multiple connective tissue genes have been recognized to underlie ATAD; other genetic variants have similarly been recognized to underlie SCAD. Little data are available regarding any genetic commonality between ATAD and SCAD. Our objective is to determine and characterize any genetic overlap between genes coding for ATAD and SCAD. We identified and reviewed 17 retrospective and prospective genetic studies of thoracic aortic dissection and SCAD published between 2016 and 2022 identified through PubMed and Orbis. Articles highlighting the significant plausible triggers for ATAD or SCAD individually were analyzed. No previous study reviewed both ATAD and SCAD genetics together. Separate lists of causative genes were constructed for ATAD and SCAD-and then commonalities were sought. A Venn diagram was constructed to display the genetic overlap and common physiologic pathways involved. We identified a definite, meaningful overlap of 15 independent genes based on a genome-wide association study or other genetic methods. The associated genetic pathways involved various biologic processes including elastin degradation, smooth muscle cell function, and the TGFβ-pathway. The overlapping genes included the following: COL3A1, TGFB2, SMAD3, MYLK, TGFBR2, TGFBR1, LOX, FBN1, NOTCH1, ELN, COL5A1, COL5A2, COL1A2, MYH11, and TLN1. The corresponding molecular pathways were investigated and correlated for both diseases. We are not aware of other studies searching for genetic commonalities between ATAD and SCAD. We have successfully identified overlapping genes-and their corresponding molecular pathways-for ATAD and SCAD. We hope that these insights will lead to further clinical and scientific understanding of each disease through study of their fundamental commonalities.

Microfibril-Associated Glycoprotein-2 Promoted Fracture Healing via Integrin αvβ3/PTK2/AKT Signaling

Fracture healing is a complex physiological process in which angiogenesis plays an essential role. Microfibril-associated glycoprotein-2 (MAGP2) has been reported to possess a proangiogenic activity via integrin αvβ3, yet its role in bone repair is unexplored. In this study, a critical-sized femoral defect (2 mm) was created in mice, followed by the delivery of an adenovirus-based MAGP2 overexpression vector or its negative control at the fracture site. At days 7, 14, 21, and 28 postfracture, bone fracture healing was evaluated by radiography, micro-computed tomography, and histopathologic analysis. Adenovirus-based MAGP2 overexpression vector-treated mice exhibited increased bone mineral density and bone volume fraction. MAGP2 overexpression contributed to an advanced stage of endochondral ossification and induced cartilage callus into the bony callus. Further analysis indicated that MAGP2 was associated with enhanced angiogenesis, as evidenced by marked MAGP2 and integrin αvβ3 costaining and increased endothelial cell markers such as endomucin and CD31 levls, as well as elevated phosphorylation of protein tyrosine kinase 2 (PTK2) and AKT serine/threonine kinase 1 (AKT) in the callus. In vitro, recombinant human MAGP2 treatment enhanced the viability, migration, and tube formation ability of human microvascular endothelial cells, which was partially reversed by integrin αvβ3 inhibition or MK-2206, a specific AKT inhibitor. Inhibition of integrin αvβ3 abolished MAGP2-induced PTK2 and AKT activation. Taken together, our data provide the first evidence that MAGP2 promotes angiogenesis and bone formation by activating the integrin αvβ3/PTK2/AKT signaling pathway.

Microfibril-associated protein 5 and the regulation of skin scar formation

Many factors regulate scar formation, which yields a modified extracellular matrix (ECM). Among ECM components, microfibril-associated proteins have been minimally explored in the context of skin wound repair. Microfibril-associated protein 5 (MFAP5), a small 25 kD serine and threonine rich microfibril-associated protein, influences microfibril function and modulates major extracellular signaling pathways. Though known to be associated with fibrosis and angiogenesis in certain pathologies, MFAP5's role in wound healing is unknown. Using a murine model of skin wound repair, we found that MFAP5 is significantly expressed during the proliferative and remodeling phases of healing. Analysis of existing single-cell RNA-sequencing data from mouse skin wounds identified two fibroblast subpopulations as the main expressors of MFAP5 during wound healing. Furthermore, neutralization of MFAP5 in healing mouse wounds decreased collagen deposition and refined angiogenesis without altering wound closure. In vitro, recombinant MFAP5 significantly enhanced dermal fibroblast migration, collagen contractility, and expression of pro-fibrotic genes. Additionally, TGF-ß1 increased MFAP5 expression and production in dermal fibroblasts. Our findings suggest that MFAP5 regulates fibroblast function and influences scar formation in healing wounds. Our work demonstrates a previously undescribed role for MFAP5 and suggests that microfibril-associated proteins may be significant modulators of wound healing outcomes and scarring.

Microfibrillar-associated protein 5 suppresses adipogenesis by inhibiting essential coactivator of PPARγ

Femoral head necrosis is responsible for severe pain and its incidence is increasing. Abnormal adipogenic differentiation and fat cell hypertrophy of bone marrow mesenchymal stem cells increase intramedullary cavity pressure, leading to osteonecrosis. By analyzing gene expression before and after adipogenic differentiation, we found that Microfibril-Associated Protein 5 (MFAP5) is significantly down-regulated in adipogenesis whilst the mechanism of MFAP5 in regulating the differentiation of bone marrow mesenchymal stem cells is unknown. The purpose of this study was to clarify the role of MAFP5 in adipogenesis and therefore provide a theoretical basis for future therapeutic options of osteonecrosis. By knockdown or overexpression of MFAP5 in C3H10 and 3T3-L1 cells, we found that MFAP5 was significantly down-regulated as a key regulator of adipogenic differentiation, and identified the underlying downstream molecular mechanism. MFAP5 directly bound to and inhibited the expression of Staphylococcal Nuclease And Tudor Domain Containing 1, an essential coactivator of PPARγ, exerting an important regulatory role in adipogenesis.

SARA suppresses myofibroblast precursor transdifferentiation in fibrogenesis in a mouse model of scleroderma

We previously reported that Smad anchor for receptor activation (SARA) plays a critical role in maintaining epithelial cell phenotype. Here, we show that SARA suppressed myofibroblast precursor transdifferentiation in a mouse model of scleroderma. Mice overexpressing SARA specifically in PDGFR-β+ pericytes and pan-leukocytes (SARATg) developed significantly less skin fibrosis in response to bleomycin injection compared with wild-type littermates (SARAWT). Single-cell RNA-Seq analysis of skin PDGFR-β+ cells implicated pericyte subsets assuming myofibroblast characteristics under fibrotic stimuli, and SARA overexpression blocked the transition. In addition, a cluster that expresses molecules associated with Th2 cells and macrophage activation was enriched in SARAWT mice, but not in SARATg mice, after bleomycin treatment. Th2-specific Il-31 expression was increased in skin of the bleomycin-treated SARAWT mice and patients with scleroderma (or systemic sclerosis, SSc). Receptor-ligand analyses indicated that lymphocytes mediated pericyte transdifferentiation in SARAWT mice, while with SARA overexpression the myofibroblast activity of pericytes was suppressed. Together, these data suggest a potentially novel crosstalk between myofibroblast precursors and immune cells in the pathogenesis of SSc, in which SARA plays a critical role.

Fibrillin-1 Regulates Arteriole Integrity in the Retina

Fibrillin-1 is an extracellular matrix protein that assembles into microfibrils that provide critical functions in large blood vessels and other tissues. Mutations in the fibrillin-1 gene are associated with cardiovascular, ocular, and skeletal abnormalities in Marfan syndrome. Fibrillin-1 is a component of the wall of large arteries but has been poorly described in other vessels. We examined the microvasculature in the retina using wild type mice and two models of Marfan syndrome, Fbn1^C1041G/+ and Fbn1^mgR/mgR. In the mouse retina, fibrillin-1 was detected around arterioles, in close contact with the basement membrane, where it colocalized with MAGP1. Both a mutation in fibrillin-1 or fibrillin-1 underexpression characteristically altered the microvasculature. In Fbn1^C1041G/+ and Fbn1^mgR/mgR mice, arterioles were enlarged with reduced MAGP1 deposition and focal loss of smooth muscle cell coverage. Losartan, which prevents aortic enlargement in Fbn1^C1041G/+ mice, prevented smooth muscle cell loss and vessel leakiness when administrated in a preventive mode. Moreover, losartan also partially rescued the defects in a curative mode. Thus, fibrillin-1/MAGP1 performs essential functions in arteriolar integrity and mutant fibrillin-1-induced defects can be prevented or partially rescued pharmacologically. These new findings could have implications for people with Marfan syndrome.

A resource for integrated genomic analysis of the human liver

In this study, we generated whole-transcriptome RNA-Seq from n = 192 genotyped liver samples and used these data with existing data from the GTEx Project (RNA-Seq) and previous liver eQTL (microarray) studies to create an enhanced transcriptomic sequence resource in the human liver. Analyses of genotype-expression associations show pronounced enrichment of associations with genes of drug response. The associations are primarily consistent across the two RNA-Seq datasets, with some modest variation, indicating the importance of obtaining multiple datasets to produce a robust resource. We further used an empirical Bayesian model to compare eQTL patterns in liver and an additional 20 GTEx tissues, finding that MHC genes, and especially class II genes, are enriched for liver-specific eQTL patterns. To illustrate the utility of the resource to augment GWAS analysis with small sample sizes, we developed a novel meta-analysis technique to combine several liver eQTL data sources. We also illustrate its application using a transcriptome-enhanced re-analysis of a study of neutropenia in pancreatic cancer patients. The associations of genotype with liver expression, including splice variation and its genetic associations, are made available in a searchable genome browser.

Tracking an Elusive Killer: State of the Art of Molecular-Genetic Knowledge and Laboratory Role in Diagnosis and Risk Stratification of Thoracic Aortic Aneurysm and Dissection

The main challenge in diagnosing and managing thoracic aortic aneurysm and dissection (TAA/D) is represented by the early detection of a disease that is both deadly and “elusive”, as it generally grows asymptomatically prior to rupture, leading to death in the majority of cases. Gender differences exist in aortic dissection in terms of incidence and treatment options. Efforts have been made to identify biomarkers that may help in early diagnosis and in detecting those patients at a higher risk of developing life-threatening complications. As soon as the hereditability of the TAA/D was demonstrated, several genetic factors were found to be associated with both the syndromic and non-syndromic forms of the disease, and they currently play a role in patient diagnosis/prognosis and management-guidance purposes. Likewise, circulating biomarker could represent a valuable resource in assisting the diagnosis, and several studies have attempted to identify specific molecules that may help with risk stratification outside the emergency department. Even if promising, those data lack specificity/sensitivity, and, in most cases, they need more testing before entering the “clinical arena”. This review summarizes the state of the art of the laboratory in TAA/D diagnostics, with particular reference to the current and future role of molecular-genetic testing.

CD105+CD90+CD13+ identifies a clonogenic subset of adventitial lung fibroblasts

Mesenchymal cells are important components of specified niches in the lung, and can mediate a wide range of processes including tissue regeneration and repair. Dysregulation of these processes can lead to improper remodeling of tissue as observed in several lung diseases. The mesenchymal cells responsible remain poorly described, partially due to the heterogenic nature of the mesenchymal compartment and the absence of appropriate markers. Here, we describe that CD105⁺CD90⁺ mesenchymal cells can be divided into two populations based on their expression of CD13/aminopeptidase N (CD105⁺CD90⁺CD13⁻ and CD105⁺CD90⁺CD13⁺). By prospective isolation using FACS, we show that both these populations give rise to clonogenic fibroblast-like cells, but with an increased clonogenic and proliferative capacity of CD105⁺CD90⁺CD13⁺ cells. Transcriptomic and spatial analysis pinpoints an adventitial fibroblast subset as the origin of CD105⁺CD90⁺CD13⁺ clonogenic mesenchymal cells in human lung.

MAGP2 induces tumor progression by enhancing uPAR-mediated cell proliferation

Microfibril-associated glycoprotein 2 (MAGP2) plays an important role in regulating cell signaling and acts as a biomarker to predict the prognostic effect of tumor therapy. However, research on MAGP2 mostly focuses on its extracellular signal transmission features, and its potential intracellular function is rarely reported. Here, we reported that intracellular MAGP2 increased the stability of urokinase-type plasminogen activator receptor (uPAR) in the cell by direct interaction which inhibits the lysosomal-mediated degradation of uPAR. Furthermore, with the detection of protein content changes and proteomics analysis, we found that highly expressed MAGP2 promoted the proliferation of tumor cells through uPAR-mediated p38-NF-ĸB signaling axis activation, enhancement of DNA damage repair and reduction of cell stagnation in the S phase of the cell cycle. In the nude mouse xenograft model of colorectal cancer, the upregulation of MAGP2 in tumor cells significantly promoted tumor progression, while the downregulation of uPAR significantly attenuated tumor progression. These studies elucidate the role of MAGP2 inside the cell and provide a new explanation for why patients with higher MAGP2 expression in tumors are associated with a worse prognosis. In addition, we also determined a mechanism for the stable existence of uPAR in the cell, providing information for the development of tumor drugs targeting uPAR.

Modulation of Photoaging-Induced Cutaneous Elastin: Evaluation of Gene and Protein Expression of Markers Related to Elastogenesis Under Different Photoexposure Conditions

INTRODUCTION

Photoaging is the process by which ultraviolet rays gradually induce clinical and histological changes in the skin through the production and organization of biological molecules, such as elastin, which is critical to skin strength and elasticity. After exposure to radiation, elastin may undergo alternative mRNA splicing, resulting in modified proteins that contribute to the formation of aging characteristics, such as solar elastosis. The present work aimed to study two different forms of elastin under these conditions: normal elastin and elastin that had been altered in exon 26A.

METHODS

These different forms of elastin were characterized for gene expression by quantitative real-time polymerase chain reaction (qPCR) and for protein expression by immunohistochemistry of ex vivo skins (from photoexposed and non-photoexposed areas) and in vitro reconstituted skin. In addition, up- and downstream molecules in the elastin signaling cascade were evaluated.

RESULTS

As a result, a significant increase in the gene expression of elastin 26A was observed in both ex vivo photoexposed skin tissues and the in vitro photoexposed reconstituted skins. Additionally, significant increases in the gene expression levels of matrix metalloproteinase-12 (MMP12) and lysyl oxidase (LOX) were observed in the ex vivo skin model. The evaluation of protein expression levels of some photoaging markers on the reconstituted skin revealed increased tropoelastin and fibrillin-1 expression after photoexposure.

CONCLUSION

This work contributes to a better understanding of the biological mechanisms involved in photoaging, making it possible to obtain new strategies for the development of dermocosmetic active ingredients to prevent and treat skin aging.

Decreased Levels of Microfibril-Associated Glycoprotein (MAGP)-1 in Patients with Colon Cancer and Obesity Are Associated with Changes in Extracellular Matrix Remodelling

OBJECTIVE

The protein microfibril-associated glycoprotein (MAGP)-1 constitutes a crucial extracellular matrix protein. We aimed to determine its impact on visceral adipose tissue (VAT) remodelling during obesity-associated colon cancer (CC).

METHODS

Samples obtained from 79 subjects (29 normoponderal (NP) (17 with CC) and 50 patients with obesity (OB) (19 with CC)) were used in the study. Circulating concentrations of MAGP-1 and its gene expression levels (MFAP2) in VAT were analysed. The impact of inflammation-related factors and adipocyte-conditioned media (ACM) on MFAP2 mRNA levels in colon adenocarcinoma HT-29 cells were further analysed. The effects of MAGP-1 in the expression of genes involved in the extracellular matrix (ECM) remodelling and tumorigenesis in HT-29 cells was also explored.

RESULTS

Obesity (p < 0.01) and CC (p < 0.001) significantly decreased MFAP2 gene expression levels in VAT whereas an opposite trend in TGFB1 mRNA levels was observed. Increased mRNA levels of MFAP2 after the stimulation of HT-29 cells with lipopolysaccharide (LPS) (p < 0.01) and interleukin (IL)-4 (p < 0.01) together with a downregulation (p < 0.05) after hypoxia mimicked by CoCl₂ treatment was observed. MAGP-1 treatment significantly enhanced the mRNA levels of the ECM-remodelling genes collagen type 6 α3 chain (COL6A3) (p < 0.05), decorin (DCN) (p < 0.01), osteopontin (SPP1) (p < 0.05) and TGFB1 (p < 0.05). Furthermore, MAGP-1 significantly reduced (p < 0.05) the gene expression levels of prostaglandin-endoperoxide synthase 2 (COX2/PTGS2), a key gene controlling cell proliferation, growth and adhesion in CC. Interestingly, a significant decrease (p < 0.01) in the mRNA levels of MFAP2 in HT-29 cells preincubated with ACM from volunteers with obesity compared with control media was observed. Conclusion: The decreased levels of MAGP-1 in patients with obesity and CC together with its capacity to modulate key genes involved in ECM remodelling and tumorigenesis suggest MAGP-1 as a link between AT excess and obesity-associated CC development.

Extracellular matrix-mediated remodeling and mechanotransduction in large vessels during development and disease

The vascular extracellular matrix (ECM) is synthesized and secreted during embryogenesis and facilitates the growth and remodeling of large vessels. Proper interactions between the ECM and vascular cells are pivotal for building the vasculature required for postnatal dynamic circulation. The ECM serves as a structural component by maintaining the integrity of the vessel wall while also regulating intercellular signaling, which involves cytokines and growth factors. The major ECM component in large vessels is elastic fibers, which include elastin and microfibrils. Elastin is predominantly synthesized by vascular smooth muscle cells (SMCs) and uses microfibrils as a scaffold to lay down and assemble cross-linked elastin. The absence of elastin causes developmental defects that result in the subendothelial proliferation of SMCs and inward remodeling of the vessel wall. Notably, elastic fiber formation is attenuated in the ductus arteriosus and umbilical arteries. These two vessels function during embryogenesis and close after birth via cellular proliferation, migration, and matrix accumulation. In dynamic postnatal mechano-environments, the elastic fibers in large vessels also serve an essential role in proper signal transduction as a component of elastin-contractile units. Disrupted mechanotransduction in SMCs leads to pathological conditions such as aortic aneurysms that exhibit outward remodeling. This review discusses the importance of the ECM-mainly the elastic fiber matrix-in large vessels during developmental remodeling and under pathological conditions. By dissecting the role of the ECM in large vessels, we aim to provide insights into the role of ECM-mediated signal transduction that can provide a basis for seeking new targets for intervention in vascular diseases.

Insights on the Pathogenesis of Aneurysm through the Study of Hereditary Aortopathies

Thoracic aortic aneurysms (TAA) are permanent and localized dilations of the aorta that predispose patients to a life-threatening risk of aortic dissection or rupture. The identification of pathogenic variants that cause hereditary forms of TAA has delineated fundamental molecular processes required to maintain aortic homeostasis. Vascular smooth muscle cells (VSMCs) elaborate and remodel the extracellular matrix (ECM) in response to mechanical and biochemical cues from their environment. Causal variants for hereditary forms of aneurysm compromise the function of gene products involved in the transmission or interpretation of these signals, initiating processes that eventually lead to degeneration and mechanical failure of the vessel. These include mutations that interfere with transduction of stimuli from the matrix to the actin-myosin cytoskeleton through integrins, and those that impair signaling pathways activated by transforming growth factor-β (TGF-β). In this review, we summarize the features of the healthy aortic wall, the major pathways involved in the modulation of VSMC phenotypes, and the basic molecular functions impaired by TAA-associated mutations. We also discuss how the heterogeneity and balance of adaptive and maladaptive responses to the initial genetic insult might contribute to disease.

Human Microfibrillar-Associated Protein 4 (MFAP4) Gene Promoter: A TATA-Less Promoter That Is Regulated by Retinol and Coenzyme Q10 in Human Fibroblast Cells

Elastic fibers are one of the major structural components of the extracellular matrix (ECM) in human connective tissues. Among these fibers, microfibrillar-associated protein 4 (MFAP4) is one of the most important microfibril-associated glycoproteins. MFAP4 has been found to bind with elastin microfibrils and interact directly with fibrillin-1, and then aid in elastic fiber formation. However, the regulations of the human MFAP4 gene are not so clear. Therefore, in this study, we firstly aimed to analyze and identify the promoter region of the human MFAP4 gene. The results indicate that the human MFAP4 promoter is a TATA-less promoter with tissue- and species-specific properties. Moreover, the promoter can be up-regulated by retinol and coenzyme Q10 (coQ10) in Detroit 551 cells.

Thoracic aortic aneurysm gene dictionary

Thoracic aortic aneurysm is typically clinically silent, with a natural history of progressive enlargement until a potentially lethal complication such as rupture or dissection occurs. Underlying genetic predisposition strongly influences the risk of thoracic aortic aneurysm and dissection. Familial cases are more virulent, have a higher rate of aneurysm growth, and occur earlier in life. To date, over 30 genes have been associated with syndromic and non-syndromic thoracic aortic aneurysm and dissection. The causative genes and their specific variants help to predict the disease phenotype, including age at presentation, risk of dissection at small aortic sizes, and risk of other cardiovascular and systemic manifestations. This genetic "dictionary" is already a clinical reality, allowing us to personalize care based on specific causative mutations for a substantial proportion of these patients. Widespread genetic sequencing of thoracic aortic aneurysm and dissection patients has been and continues to be crucial to the rapid expansion of this dictionary and ultimately, the delivery of truly personalized care to every patient.

Molecular structure and function of microfibrillar-associated proteins in skeletal and metabolic disorders and cancers

Microfibrillar-associated proteins (MFAPs) are extracellular matrix glycoproteins, which play a role in microfibril assembly, elastinogenesis, and tissue homeostasis. MFAPs consist of five subfamily members, including MFAP1, MFAP2, MFAP3, MFAP4, and MFAP5. Among these, MFAP2 and MFAP5 are most closely related, and exhibit very limited amino acid sequence homology with MFAP1, MFAP3, and MFAP4. Gene expression profiling analysis reveals that MFAP2, MFAP5, and MFAP4 are specifically expressed in osteoblastic like cells, whereas MFAP1 and MFAP3 are more ubiquitously expressed, indicative of their diverse role in the tropism of tissues. Molecular structural analysis shows that each MFAP family member has distinct features, and functional evidence reveals discrete purposes of individual MFAPs. Animal studies indicate that MFAP2-deficient mice exhibit progressive osteopenia with elevated receptor activator of NF-κB ligand (RANKL) expression, whereas MFAP5-deficient mice are neutropenic, and MFAP4-deficient mice displayed emphysema-like pathology and the impaired formation of neointimal hyperplasia. Emerging data also suggest that MFAPs are involved in cancer progression and fat metabolism. Further understanding of tissue-specific pathophysiology of MFAPs might offer potential novel therapeutic targets for related diseases, such as skeletal and metabolic disorders, and cancers.

Extracellular Matrix Analysis of Human Renal Arteries in Both Quiescent and Active Vascular State

In vascular tissue engineering strategies, the addition of vascular-specific extracellular matrix (ECM) components may better mimic the in vivo microenvironment and potentially enhance cell-matrix interactions and subsequent tissue growth. For this purpose, the exact composition of the human vascular ECM first needs to be fully characterized. Most research has focused on characterizing ECM components in mature vascular tissue; however, the developing fetal ECM matches the active environment required in vascular tissue engineering more closely. Consequently, we characterized the ECM protein composition of active (fetal) and quiescent (mature) renal arteries using a proteome analysis of decellularized tissue. The obtained human fetal renal artery ECM proteome dataset contains higher levels of 15 ECM proteins versus the mature renal artery ECM proteome, whereas 16 ECM proteins showed higher levels in the mature tissue compared to fetal. Elastic ECM proteins EMILIN1 and FBN1 are significantly enriched in fetal renal arteries and are mainly produced by cells of mesenchymal origin. We functionally tested the role of EMILIN1 and FBN1 by anchoring the ECM secreted by vascular smooth muscle cells (SMCs) to glass coverslips. This ECM layer was depleted from either EMILIN1 or FBN1 by using siRNA targeting of the SMCs. Cultured endothelial cells (ECs) on this modified ECM layer showed alterations on the transcriptome level of multiple pathways, especially the Rho GTPase controlled pathways. However, no significant alterations in adhesion, migration or proliferation were observed when ECs were cultured on EMILIN1- or FNB1-deficient ECM. To conclude, the proteome analysis identified unique ECM proteins involved in the embryonic development of renal arteries. Alterations in transcriptome levels of ECs cultured on EMILIN1- or FBN1-deficient ECM showed that these candidate proteins could affect the endothelial (regenerative) response.

Microfibril-Associated Protein 2 (MFAP2) Potentiates Invasion and Migration of Melanoma by EMT and Wnt/β-Catenin Pathway

Background

Growing evidence indicates an association between microfibril-associated protein 2 (MFAP2) and a number of physiological and pathological mechanisms. The potential role of MFAP2 in cancer requires further elucidation. The present study investigated the biological behavior of MFAP2 in melanoma patients.

Material/Methods

MFAP2 inhibition was established in the B16 melanoma cell line through the use of RNA interference and was assessed by quantitative real-time PCR (qRT-PCR) and Western blot analysis. Wound-healing analysis, transwell assay, and in vivo imaging were performed to investigate the roles of MFAP2 reducing cell mobility, migration, and invasion abilities in vitro and in vivo.

Results

We found substantially higher MFAP2 expression in B16 melanoma cells. The knockdown of MFAP2 inhibited B16 melanoma cells migration and invasion. Western blot analysis was used to assess changes in biomarkers of EMT, indicating the function of MFAP2 in EMT. We found that downregulation of MFAP2 altered the expression of Wnt/β-catenin-linked protein.

Conclusions

Our results suggest that MFAP2 has potential as a molecular target to treat melanoma and suppress metastasis of melanoma cells.

Biomarker Signatures of Quality for Engineering Nasal Chondrocyte-Derived Cartilage

The definition of quality controls for cell therapy and engineered product manufacturing processes is critical for safe, effective, and standardized clinical implementation. Using the example context of cartilage grafts engineered from autologous nasal chondrocytes, currently used for articular cartilage repair in a phase II clinical trial, we outlined how gene expression patterns and generalized linear models can be introduced to define molecular signatures of identity, purity, and potency. We first verified that cells from the biopsied nasal cartilage can be contaminated by cells from a neighboring tissue, namely perichondrial cells, and discovered that they cannot deposit cartilaginous matrix. Differential analysis of gene expression enabled the definition of identity markers for the two cell populations, which were predictive of purity in mixed cultures. Specific patterns of expression of the same genes were significantly correlated with cell potency, defined as the capacity to generate tissues with histological and biochemical features of hyaline cartilage. The outlined approach can now be considered for implementation in a good manufacturing practice setting, and offers a paradigm for other regenerative cellular therapies.

MAGP2, a Component of Extracellular Matrix, Is Upregulated in Colorectal Cancer and Negatively Modulated by miR-200b-3p

Background:

Colorectal cancer is one of the leading causes of cancer-related death worldwide, but its mechanism has not been clarified clearly. Microfibrial-associated glycoprotein 2 is mainly located in extracellular matrix, and its role in colorectal cancer is obscure.

Methods:

Immunohistochemical staining and quantitative real-time polymerase chain reaction were used to compare the expression level of microfibrial-associated glycoprotein 2 in colorectal cancer tissues and adjacent tissues. Western blot was used to detect the expression of microfibrial-associated glycoprotein 2 in colorectal cancer cell lines and normal colonic epithelium cell line. Kaplan-Meier analysis and χ² test were applied to evaluate the potential of microfibrial-associated glycoprotein 2 to function as cancer biomarker. Lentiviral transduction was used to induce microfibrial-associated glycoprotein 2 overexpression in HCT116 cells and NCM460 cells, followed by detecting cell proliferation, migration, and invasion. Quantitative real-time polymerase chain reaction was used to investigate the changes in downstream genes after microfibrial-associated glycoprotein 2 overexpression. Luciferase assay was conducted to validate whether miR-200b-3p can directly target microfibrial-associated glycoprotein 2.

Results:

We validated that microfibrial-associated glycoprotein 2 was upregulated in colorectal cancer samples and cells. We also demonstrated its upregulation was associated with several clinicopathologic features such as Dukes stage (P = .048), differentiation status (P = .034), and local lymphatic metastasis (P = .036) of patients with colorectal cancer, and its high expression indicated shorter overall survival of the patients. Microfibrial-associated glycoprotein 2 overexpression remarkably promoted cell proliferation and metastasis via regulating the downstream genes of Notch, including hes family bHLH transcription factor 1 (HES1), Slug, Snail, matrix metalloproteinase 2, matrix metalloproteinase 9, and Kruppel-like factor 4. We also identified miR-200b-3p as a posttranscriptional regulator of microfibrial-associated glycoprotein 2, which partly explain the high expression mechanism of microfibrial-associated glycoprotein 2 in cancer tissues. Conclusion: Microfibrial-associated glycoprotein 2, negatively modulated by miR-200b-3p, is an oncogene of colorectal cancer associated with patients’ prognosis. It may function as a potential biomarker and therapeutic target for colorectal cancer.

Identification of the growth factor-binding sequence in the extracellular matrix protein MAGP-1

Microfibril-associated glycoprotein-1 (MAGP-1) is a component of vertebrate extracellular matrix (ECM) microfibrils that, together with the fibrillins, contributes to microfibril function. Many of the phenotypes associated with MAGP-1 gene inactivation are consistent with dysregulation of the transforming growth factor β (TGFβ)/bone morphogenetic protein (BMP) signaling system. We have previously shown that full-length MAGP-1 binds active TGFβ-1 and some BMPs. The work presented here further defines the growth factor-binding domain of MAGP-1. Using recombinant domains and synthetic peptides, along with surface plasmon resonance analysis to measure the kinetics of the MAGP-1-TGFβ-1 interaction, we localized the TGFβ- and BMP-binding site in MAGP-1 to a 19-amino acid-long, highly acidic sequence near the N terminus. This domain was specific for binding active, but not latent, TGFβ-1. Growth factor activity experiments revealed that TGFβ-1 retains signaling activity when complexed with MAGP-1. Furthermore, when bound to fibrillin, MAGP-1 retained the ability to interact with TGFβ-1, and active TGFβ-1 did not bind fibrillin in the absence of MAGP-1. The absence of MAGP was sufficient to raise the amount of total TGFβ stored in the ECM of cultured cells, suggesting that the MAGPs compete with the TGFβ large latent complex for binding to microfibrils. Together, these results indicate that MAGP-1 plays an active role in TGFβ signaling in the ECM.

The Genetics of Thoracic Aortic Aneurysms and Dissection: A Clinical Perspective

Thoracic aortic aneurysm and dissection (TAAD) affects many patients globally and has high mortality rates if undetected. Once thought to be solely a degenerative disease that afflicted the aorta due to high pressure and biomechanical stress, extensive investigation of the heritability and natural history of TAAD has shown a clear genetic basis for the disease. Here, we review both the cellular mechanisms and clinical manifestations of syndromic and non-syndromic TAAD. We particularly focus on genes that have been linked to dissection at diameters <5.0 cm, the current lower bound for surgical intervention. Genetic screening tests to identify patients with TAAD associated mutations that place them at high risk for dissection are also discussed.

Hypoxia-induced MFAP5 Promotes Tumor Migration and Invasion via AKT Pathway in Head and Neck Squamous Cell Carcinoma

Objective: Microfibrillar-associated protein 5 (MFAP5) is highly expressed in many types of cancers. Our previous study has observed that overexpression of MFAP5 was correlated with lymph nodes metastasis and poor prognosis in head and neck squamous cell carcinoma (HNSCC), but the underlying mechanism is poorly understood.

Materials and methods: The MFAP5 expression is detected under hypoxia condition. HNSCC cell lines are transfected with MFAP5-expressing lentivirus vector to establish stable overexpression model. Wound-healing, migration and invasion assay are used to determine the effect of MFAP5 on HNSCC and metastasis-related proteins are examined by Western blot. In vivo lung metastasis assays are conducted by the tail vein injection. In addition, immunohistochemistry is applied to analyze the correlation of MFAP5, hypoxia-induced factor-1 α (HIF-1α), and vimentin in 84 HNSCC patients' tissue samples.

Results: Firstly, MFAP5 expression can be markedly induced under hypoxia condition in HNSCC cell lines. Cell lines with MFAP5 overexpression has a significant higher ability of migration and invasion. In addition, in vivo assay observes that overexpression of MFAP5 can promote tumor lung metastasis. Furthermore, MFAP5 facilitates this process by activating epithelial-mesenchymal transition (EMT) program via AKT pathway in HNSCC cell lines. The pro-metastatic effect of MFAP5 can be reversed by MK2206, an AKT phosphorylation inhibitor. Lastly, the positive correlation among HIF-1α, MFAP5 and vimentin from tissue samples and TCGA dataset are also observed in HNSCC.

Conclusion: Our study demonstrates MFAP5 plays a critical role in hypoxia-induced EMT program via AKT pathway in HNSCC, which would be a very promising therapeutic target.

Genes Associated with Thoracic Aortic Aneurysm and Dissection: 2019 Update and Clinical Implications

Thoracic aortic aneurysm is a typically silent disease characterized by a lethal natural history. Since the discovery of the familial nature of thoracic aortic aneurysm and dissection (TAAD) almost 2 decades ago, our understanding of the genetics of this disorder has undergone a transformative amplification. To date, at least 37 TAAD-causing genes have been identified and an estimated 30% of the patients with familial nonsyndromic TAAD harbor a pathogenic mutation in one of these genes. In this review, we present our yearly update summarizing the genes associated with TAAD and the ensuing clinical implications for surgical intervention. Molecular genetics will continue to bolster this burgeoning catalog of culprit genes, enabling the provision of personalized aortic care.

Cardiomyocyte dedifferentiation and remodeling in 3D scaffolds to generate the cellular diversity of engineering cardiac tissues

The use of engineered cardiac tissues (ECTs) is a new strategy for the repair and replacement of cardiac tissues in patients with myocardial infarction, particularly at late stages. However, the mechanisms underlying the development of ECTs, including cell-scaffold interactions, are not fully understood, although they are closely related to their therapeutic effect. In the present study, we aimed to determine the cellular fate of cardiomyocytes in a 3D scaffold microenvironment, as well as their role in generating the cellular diversity of ECTs by single-cell sequencing analysis. Consistent with the observed plasticity of cardiomyocytes during cardiac regeneration, cardiomyocytes in 3D scaffolds appeared to dedifferentiate, showing an initial loss of normal cytoskeleton organization in the adaptive response to the new scaffold microenvironment. Cardiomyocytes undergoing this process regained their proliferation potential and gradually developed into myocardial cells at different developmental stages, generating heterogeneous regenerative ECTs. To better characterize the remodeled ECTs, high-throughput single-cell sequencing was performed. The ECTs contained a wide diversity of cells related to endogenous classes in the heart, including myocardial cells at different developmental stages and different kinds of interstitial cells. Non-cardiac cells seemed to play important roles in cardiac reconstruction, especially Cajal-like interstitial cells and macrophages. Altogether, our results showed for the first time that cells underwent adaptive dedifferentiation for survival in a 3D scaffold microenvironment to generate heterogeneous tissues. These findings provide an important basis for an improved understanding of the development and assembly of engineered tissues.

Stromal fibroblast-derived MFAP5 promotes the invasion and migration of breast cancer cells via Notch1/slug signaling

BACKGROUND

The tumor microenvironment (TME) regulates tumor progression, and cancer-associated fibroblasts (CAFs) are the primary stromal components of the TME, with the potential to drive tumor metastasis via the secretion of paracrine factors, but the specific mechanisms driving this process have not been defined.

METHODS

Proteins secreted from CAFs and normal fibroblasts (NFs) were analyzed via proteomic analysis (fold change > 2, p < 0.05) to identify tumor-promoting proteins secreted by CAFs.

RESULTS

Proteomic analysis revealed that microfibrillar-associated protein 5 (MFAP5) is preferentially expressed and secreted by CAFs relative to NFs, which was confirmed by Western blotting and RT-qPCR. Transwell and wound healing assays confirmed that MFAP5 is secreted by CAFs, and drives the invasion and migration of MCF7 breast cancer cells. We further found that in MCF7 cells MFAP5 promoted epithelial-mesenchymal transition, activating Notch1 signaling and consequently upregulating NICD1 and slug. When Notch1 was knocked down in MCF7 cells, the ability of MFAP5 to promote invasion and migration decreased.

CONCLUSION

CAFs promote cancer cells invasion and migration via MFAP5 secretion and activation of the Notch1/slug signaling. These data highlight this pathway as a therapeutic target to disrupt tumor progression through the interference of CAF-tumor crosstalk.

DNA methylation and gene expression profiling reveal MFAP5 as a regulatory driver of extracellular matrix remodeling in varicose vein disease

AIM

To integrate transcriptomic and DNA-methylomic measurements on varicose versus normal veins using a systems biological analysis to shed light on the interplay between genetic and epigenetic factors.

MATERIALS & METHODS

Differential expression and methylation were measured using microarrays, supported by real-time quantitative PCR and immunohistochemistry confirmation for relevant gene products. A systems biological 'upstream analysis' was further applied.

RESULTS

We identified several potential key players contributing to extracellular matrix remodeling in varicose veins. Specifically, our analysis suggests MFAP5 acting as a master regulator, upstream of integrins, of the cellular network affecting the varicose vein condition. Possible mechanism and pathogenic model were outlined.

CONCLUSION

A coherent model proposed incorporates the relevant signaling networks and will hopefully aid further studies on varicose vein pathogenesis.

Fibrillin microfibrils and elastic fibre proteins: Functional interactions and extracellular regulation of growth factors

Fibrillin microfibrils are extensible polymers that endow connective tissues with long-range elasticity and have widespread distributions in both elastic and non-elastic tissues. They act as a template for elastin deposition during elastic fibre formation and are essential for maintaining the integrity of tissues such as blood vessels, lung, skin and ocular ligaments. A reduction in fibrillin is seen in tissues in vascular ageing, chronic obstructive pulmonary disease, skin ageing and UV induced skin damage, and age-related vision deterioration. Most mutations in fibrillin cause Marfan syndrome, a genetic disease characterised by overgrowth of the long bones and other skeletal abnormalities with cardiovascular and eye defects. However, mutations in fibrillin and fibrillin-binding proteins can also cause short-stature pathologies. All of these diseases have been linked to dysregulated growth factor signalling which forms a major functional role for fibrillin.

Contribution of metabolic disease to bone fragility in MAGP1-deficient mice

Microfibril-associated glycoprotein-1 (MAGP1) is an extracellular matrix protein that interacts with fibrillin and is involved in regulating the bioavailability of signaling molecules such as TGFβ. Mice with germline MAGP1 deficiency (Mfap2-/-) develop increased adiposity, hyperglycemia, insulin resistance, bone marrow adipose tissue expansion, reduced cancellous bone mass, cortical bone thinning and bone fragility. The goal of this study was to assess whether the Mfap2-/- bone phenotypes were due to loss of MAGP1 locally or secondary to a change in whole body physiology (metabolic dysfunction). To do this, mice with conditional deletion of MAGP1 in the limb skeleton were generated by crossing MAGP1-flox mice (Mfap2lox/lox) with Prx1-Cre mice. Mfap2Prx-/- mice did not show any changes in peripheral adiposity, hyperglycemia or insulin sensitivity, but did have increased bone length and cancellous bone loss that was comparable to the germline Mfap2-/- knockout. Unlike the germline knockout, marrow adiposity, cortical bone thickness and bone strength in Mfap2Prx-/- mice were normal. These findings implicate systemic metabolic dysfunction in the development of bone fragility in germline Mfap2-/- mice. An unexpected finding of this study was the detection of MAGP1 protein in the Mfap2Prx-/- hematopoietic bone marrow, despite the absence of MAGP1 protein in osseous bone matrix and absent Mfap2 transcript expression at both sites. This suggests MAGP1 from a secondary site may accumulate in the bone marrow, but not be incorporated into the bone matrix, during times of regional MAGP1 depletion.

MFAP5 promotes tumor progression and bone metastasis by regulating ERK/MMP signaling pathways in breast cancer

Breast cancer accounts for about 30% of all cancers in women, while approximately 70% breast cancer patients developed bone metastases throughout the course of their disease, highlighting the importance of exploring new therapeutic targets. Microfibrillar-associated protein 5 (MFAP5) is a component of extracellular elastic microfibril which has been confirmed to function in tissue development and cancer progression. But the role of MFAP5 in breast cancer remains unclear. The present study demonstrated that MFAP5 was up-regulated in breast cancers compared with that in normal breast tissues, and further increased in breast cancer bone metastasis. Functionally, MFAP5 overexpression accelerated breast cancer cell proliferation and migration, while an opposite effect was observed when MFAP5 was knocked down. In addition, up-regulation of MFAP5 increased the expression of MMP2 and MMP9 and activated the ERK signaling pathway. Conversely, inhibition of MFAP5 suppressed the expression of MMP2, MMP9, p-FAK, p-Erk1/2 and p-cJun. These findings may provide a better understanding about the mechanism of breast cancer and suggest that MFAP5 may be a potential prognostic biomarker and therapeutic target for breast cancer, especially for bone metastasis of breast cancer.

Microfibril-associated glycoproteins MAGP-1 and MAGP-2 in disease

Microfibril-associated glycoproteins 1 and 2 (MAGP-1, MAGP-2) are protein components of extracellular matrix microfibrils. These proteins interact with fibrillin, the core component of microfibrils, and impart unique biological properties that influence microfibril function in vertebrates. MAGPs bind active forms of TGFβ and BMPs and are capable of modulating Notch signaling. Mutations in MAGP-1 or MAGP-2 have been linked to thoracic aneurysms and metabolic disease in humans. MAGP-2 has also been shown to be an important biomarker in several human cancers. Mice lacking MAGP-1 or MAGP-2 have defects in multiple organ systems, which reflects the widespread distribution of microfibrils in vertebrate tissues. This review summarizes our current understanding of the function of the MAGPs and their relationship to human disease.

Genes Associated with Thoracic Aortic Aneurysm and Dissection: 2018 Update and Clinical Implications

Thoracic aortic aneurysms, with an estimated prevalence in the general population of 1%, are potentially lethal, via rupture or dissection. Over the prior two decades, there has been an exponential increase in our understanding of the genetics of thoracic aortic aneurysm and/or dissection (TAAD). To date, 30 genes have been shown to be associated with the development of TAAD and ∼30% of individuals with nonsyndromic familial TAAD have a pathogenic mutation in one of these genes. This review represents the authors' yearly update summarizing the genes associated with TAAD, including implications for the surgical treatment of TAAD. Molecular genetics will continue to revolutionize the approach to patients afflicted with this devastating disease, permitting the application of genetically personalized aortic care.

FGF receptors control alveolar elastogenesis

Alveologenesis, the final step of lung development, is characterized by the formation of millions of alveolar septa that constitute the vast gas-exchange surface area. The genetic network driving alveologenesis is poorly understood compared with earlier steps in lung development. FGF signaling through receptors Fgfr3 and Fgfr4 is crucial for alveologenesis, but the mechanisms through which they mediate this process remain unclear. Here we show that in Fgfr3;Fgfr4 (Fgfr3;4) global mutant mice, alveolar simplification is first observed at the onset of alveologenesis at postnatal day 3. This is preceded by disorganization of elastin, indicating defects in the extracellular matrix (ECM). Although Fgfr3 and Fgfr4 are expressed in the mesenchyme and epithelium, inactivation in the mesenchyme, but not the epithelium, recapitulated the defects. Expression analysis of components of the elastogenesis machinery revealed that Mfap5 (also known as Magp2), which encodes an elastin-microfibril bridging factor, is upregulated in Fgfr3;4 mutants. Mfap5 mutation in the Fgfr3;4 mutant background partially attenuated the alveologenesis defects. These data demonstrate that, during normal lung maturation, FGF signaling restricts expression of the elastogenic machinery in the lung mesenchyme to control orderly formation of the elastin ECM, thereby driving alveolar septa formation to increase the gas-exchange surface.

Crossing Bridges between Extra- and Intra-Cellular Events in Thoracic Aortic Aneurysms

Thoracic aortic aneurysms (TAAs) are common, life-threatening diseases and are a major cause of mortality and morbidity. Over the past decade, genetic approaches have revealed that 1) activation of the transforming growth factor beta (TGF-β) signaling, 2) alterations in the contractile apparatus of vascular smooth muscle cells (SMCs), and 3) defects in the extracellular matrix (ECM) were responsible for development of TAAs. Most recently, a fourth mechanism has been proposed in that dysfunction of mechanosensing in the aortic wall in response to hemodynamic stress may be a key driver of TAAs. Interestingly, the elastin-contractile unit, which is an anatomical and functional unit connecting extracellular elastic laminae to the intracellular SMC contractile filaments, via cell surface receptors, has been shown to play a critical role in the mechanosensing of SMCs, and many genes identified in TAAs encode for proteins along this continuum. However, it is still debated whether these four pathways converge into a common pathway. Currently, an effective therapeutic strategy based on the underlying mechanism of each type of TAAs has not been established. In this review, we will update the present knowledge on the molecular mechanism of TAAs with a focus on the signaling pathways potentially involved in the initiation of TAAs. Finally, we will evaluate current therapeutic strategies for TAAs and propose new directions for future treatment of TAAs.

Genes Associated with Thoracic Aortic Aneurysm and Dissection: An Update and Clinical Implications

Thoracic aortic aneurysm (TAA) is a lethal disease, with a natural history of enlarging progressively until dissection or rupture occurs. Since the discovery almost 20 years ago that ascending TAAs are highly familial, our understanding of the genetics of thoracic aortic aneurysm and dissection (TAAD) has increased exponentially. At least 29 genes have been shown to be associated with the development of TAAD, the majority of which encode proteins involved in the extracellular matrix, smooth muscle cell contraction or metabolism, or the transforming growth factor-β signaling pathway. Almost one-quarter of TAAD patients have a mutation in one of these genes. In this review, we provide a summary of TAAD-associated genes, associated clinical features of the vasculature, and implications for surgical treatment of TAAD. With the widespread use of next-generation sequencing and development of novel functional assays, the future of the genetics of TAAD is bright, as both novel TAAD genes and variants within the genes will continue to be identified.

Single-Cell Resolution of Temporal Gene Expression during Heart Development

Activation of complex molecular programs in specific cell lineages governs mammalian heart development, from a primordial linear tube to a four-chamber organ. To characterize lineage-specific, spatiotemporal developmental programs, we performed single-cell RNA sequencing of >1,200 murine cells isolated at seven time points spanning embryonic day 9.5 (primordial heart tube) to postnatal day 21 (mature heart). Using unbiased transcriptional data, we classified cardiomyocytes, endothelial cells, and fibroblast-enriched cells, thus identifying markers for temporal and chamber-specific developmental programs. By harnessing these datasets, we defined developmental ages of human and mouse pluripotent stem-cell-derived cardiomyocytes and characterized lineage-specific maturation defects in hearts of mice with heterozygous mutations in Nkx2.5 that cause human heart malformations. This spatiotemporal transcriptome analysis of heart development reveals lineage-specific gene programs underlying normal cardiac development and congenital heart disease.

Comparison between smaller ruptured intracranial aneurysm and larger un-ruptured intracranial aneurysm: gene expression profile analysis

As it grows in size, an intracranial aneurysm (IA) is prone to rupture. In this study, we compared two extreme groups of IAs, ruptured IAs (RIAs) smaller than 10 mm and un-ruptured IAs (UIAs) larger than 10 mm, to investigate the genes involved in the facilitation and prevention of IA rupture. The aneurismal walls of 6 smaller saccular RIAs (size smaller than 10 mm), 6 larger saccular UIAs (size larger than 10 mm) and 12 paired control arteries were obtained during surgery. The transcription profiles of these samples were studied by microarray analysis. RT-qPCR was used to confirm the expression of the genes of interest. In addition, functional group analysis of the differentially expressed genes was performed. Between smaller RIAs and larger UIAs, 101 genes and 179 genes were significantly over-expressed, respectively. In addition, functional group analysis demonstrated that the up-regulated genes in smaller RIAs mainly participated in the cellular response to metal ions and inorganic substances, while most of the up-regulated genes in larger UIAs were involved in inflammation and extracellular matrix (ECM) organization. Moreover, compared with control arteries, inflammation was up-regulated and muscle-related biological processes were down-regulated in both smaller RIAs and larger UIAs. The genes involved in the cellular response to metal ions and inorganic substances may facilitate the rupture of IAs. In addition, the healing process, involving inflammation and ECM organization, may protect IAs from rupture.

Notch: A multi-functional integrating system of microenvironmental signals

The Notch signaling cascade is an evolutionarily ancient system that allows cells to interact with their microenvironmental neighbors through direct cell-cell interactions, thereby directing a variety of developmental processes. Recent research is discovering that Notch signaling is also responsive to a broad variety of stimuli beyond cell-cell interactions, including: ECM composition, crosstalk with other signaling systems, shear stress, hypoxia, and hyperglycemia. Given this emerging understanding of Notch responsiveness to microenvironmental conditions, it appears that the classical view of Notch as a mechanism enabling cell-cell interactions, is only a part of a broader function to integrate microenvironmental cues. In this review, we summarize and discuss published data supporting the idea that the full function of Notch signaling is to serve as an integrator of microenvironmental signals thus allowing cells to sense and respond to a multitude of conditions around them.

Simple and rapid characterization of novel large germline deletions in SDHB, SDHC and SDHD-related paraganglioma

Germline mutations in genes encoding subunits of succinate dehydrogenase (SDH) are associated with hereditary paraganglioma and pheochromocytoma. Although most mutations in SDHB, SDHC and SDHD are intraexonic variants, large germline deletions may represent up to 10% of all variants but are rarely characterized at the DNA sequence level. Additional phenotypic effects resulting from deletions that affect neighboring genes are also not understood. We performed multiplex ligation-dependent probe amplification, followed by a simple long-range PCR 'chromosome walking' protocol to characterize breakpoints in 20 SDHx-linked paraganglioma-pheochromocytoma patients. Breakpoints were confirmed by conventional PCR and Sanger sequencing. Heterozygous germline deletions of up to 104 kb in size were identified in SDHB, SDHC, SDHD and flanking genes in 20 paraganglioma-pheochromocytoma patients. The exact breakpoint could be determined in 16 paraganglioma-pheochromocytoma patients of which 15 were novel deletions. In six patients proximal genes were also deleted, including PADI2, MFAP2, ATP13A2 (PARK9), CFAP126, TIMM8B and C11orf57. These genes were either partially or completely deleted, but did not modify the phenotype. This study increases the number of known SDHx deletions by over 50% and demonstrates that a significant proportion of large gene deletions can be resolved at the nucleotide level using a simple and rapid method.

LTBP-2 Has a Single High-Affinity Binding Site for FGF-2 and Blocks FGF-2-Induced Cell Proliferation

Latent transforming growth factor-beta-1 binding protein-2 (LTBP-2) belongs to the fibrillin-LTBP superfamily of extracellular matrix proteins. LTBPs and fibrillins are involved in the sequestration and storage of latent growth factors, particularly transforming growth factor β (TGF-β), in tissues. Unlike other LTBPs, LTBP-2 does not covalently bind TGF-β, and its molecular functions remain unclear. We are screening LTBP-2 for binding to other growth factors and have found very strong saturable binding to fibroblast growth factor-2 (FGF-2) (Kd = 1.1 nM). Using a series of recombinant LTBP-2 fragments a single binding site for FGF-2 was identified in a central region of LTBP-2 consisting of six tandem epidermal growth factor-like (EGF-like) motifs (EGFs 9–14). This region was also shown to contain a heparin/heparan sulphate-binding site. FGF-2 stimulation of fibroblast proliferation was completely negated by the addition of 5-fold molar excess of LTBP-2 to the assay. Confocal microscopy showed strong co-localisation of LTBP-2 and FGF-2 in fibrotic keloid tissue suggesting that the two proteins may interact in vivo. Overall the study indicates that LTBP-2 is a potent inhibitor of FGF-2 that may influence FGF-2 bioactivity during wound repair particularly in fibrotic tissues.

MFAP5 is related to obesity-associated adipose tissue and extracellular matrix remodeling and inflammation

OBJECTIVE

Low-grade inflammation is involved in adipose tissue (AT) and extracellular matrix (ECM) remodeling and induces deposition of ECM proteins in AT. We have previously shown that MFAP5 (microfibrillar-associated protein 5) expression decreases in AT after weight loss. The aim of this study was to investigate MFAP5 localization in human AT and gene expression in adipocytes and the role of MFAP5 in adipocyte metabolism and inflammation.

METHODS

MFAP5 protein localization and gene expression were studied with immunohistochemistry and quantitative reverse transcriptase PCR (RT-qPCR) in human subcutaneous AT and cultured Simpson-Golabi-Behmel syndrome (SGBS) adipocytes, respectively. The effect of MFAP5 knock-down by siRNA on gene expression and insulin action was examined with RT-qPCR, western blot, and insulin-stimulated glucose uptake. The effect of different cytokines on MFAP5 gene and protein expression was investigated in cultured human SGBS preadipocytes.

RESULTS

MFAP5 protein was highly expressed in AT, and gene expression decreased during adipocyte differentiation in SGBS cells. Treatment of preadipocytes with TNFα and TGFβ1 increased MFAP5 gene and protein expression. Furthermore, MFAP5 knock-down decreased the expression of genes involved in inflammation.

CONCLUSIONS

Our results demonstrate that factors involving low-grade inflammation modulate MFAP5 expression and that the modified expression of MFAP5 may further regulate AT inflammation.

The microfibril-associated glycoproteins (MAGPs) and the microfibrillar niche

The microfibril-associated glycoproteins MAGP-1 and MAGP-2 are extracellular matrix proteins that interact with fibrillin to influence microfibril function. The two proteins are related through a 60 amino acid matrix-binding domain but their sequences differ outside of this region. A distinguishing feature of both proteins is their ability to interact with TGFβ family growth factors, Notch and Notch ligands, and multiple elastic fiber proteins. MAGP-2 can also interact with αvβ3 integrins via a RGD sequence that is not found in MAGP-1. Morpholino knockdown of MAGP-1 expression in zebrafish resulted in abnormal vessel wall architecture and altered vascular network formation. In the mouse, MAGP-1 deficiency had little effect on elastic fibers in blood vessels and lung but resulted in numerous unexpected phenotypes including bone abnormalities, hematopoietic changes, increased fat deposition, diabetes, impaired wound repair, and a bleeding diathesis. Inactivation of the gene for MAGP-2 in mice produced a neutropenia yet had minimal effects on bone or adipose homeostasis. Double knockouts had phenotypes characteristic of each individual knockout as well as several additional traits only seen when both genes are inactivated. A common mechanism underlying all of the traits associated with the knockout phenotypes is altered TGFβ signaling. This review summarizes our current understanding of the function of the MAGPs and discusses ideas related to their role in growth factor regulation.

MAGP1, the extracellular matrix, and metabolism

Adipose tissue and the extracellular matrix were once considered passive players in regulating physiological processes. Now, both entities are acknowledged for their capacity to engage signal transduction pathways, and for their involvement in maintaining normal tissue homeostasis. We recently published a series of studies that identified a novel mechanism whereby an extracellular matrix molecule, MAGP1 (microfibril associated glycoprotein 1), can regulate energy metabolism in adipose tissue. MAGP1 is a component of extracellular microfibrils and plays a supportive role in maintaining thermoregulation by indirectly regulating expression of the thermogenic uncoupling proteins (UCPs). The focus of this commentary is to draw attention to the role of the extracellular matrix in regulating the bioavailability of signaling molecules, like transforming growth factor β (TGFβ), and exemplify that a better understanding of the extracellular matrix's biological properties could unveil a new source of therapeutic targets for metabolic diseases.