Tenascin-C in human cardiac pathology

Effects of Tenascin C on the Integrity of Extracellular Matrix and Skin Aging

Tenascin C (TNC) is an element of the extracellular matrix (ECM) of various tissues, including the skin, and is involved in modulating ECM integrity and cell physiology. Although skin aging is apparently associated with changes in the ECM, little is known about the role of TNC in skin aging. In this study, we found that the Tnc mRNA level was significantly reduced in the skin tissues of aged mice compared with young mice, consistent with reduced TNC protein expression in aged human skin. TNC-large (TNC-L; 330-kDa) and -small (TNC-S; 240-kDa) polypeptides were observed in conditional media from primary dermal fibroblasts. Both recombinant TNC polypeptides, corresponding to TNC-L and TNC-S, increased the expression of type I collagen and reduced the expression of matrix metalloproteinase-1 in fibroblasts. Treatment of fibroblasts with a recombinant TNC polypeptide, corresponding to TNC-L, induced phosphorylation of SMAD2 and SMAD3. TNC increased the level of transforming growth factor-β1 (TGF-β1) mRNA and upregulated the expression of type I collagen by activating the TGF-β signaling pathway. In addition, TNC also promoted the expression of type I collagen in fibroblasts embedded in a three-dimensional collagen matrix. Our findings suggest that TNC contributes to the integrity of ECM in young skin and to prevention of skin aging.

Tenascin-C in cardiac disease: a sophisticated controller of inflammation, repair, and fibrosis

Tenascin-C (TNC) is a large extracellular matrix glycoprotein classified as a matricellular protein that is generally upregulated at high levels during physiological and pathological tissue remodeling and is involved in important biological signaling pathways. In the heart, TNC is transiently expressed at several important steps during embryonic development and is sparsely detected in normal adult heart but is re-expressed in a spatiotemporally restricted manner under pathological conditions associated with inflammation, such as myocardial infarction, hypertensive cardiac fibrosis, myocarditis, dilated cardiomyopathy, and Kawasaki disease. Despite its characteristic and spatiotemporally restricted expression, TNC knockout mice develop a grossly normal phenotype. However, various disease models using TNC null mice combined with in vitro experiments have revealed many important functions for TNC and multiple molecular cascades that control cellular responses in inflammation, tissue repair, and even myocardial regeneration. TNC has context-dependent diverse functions and, thus, may exert both harmful and beneficial effects in damaged hearts. However, TNC appears to deteriorate adverse ventricular remodeling by proinflammatory and profibrotic effects in most cases. Its specific expression also makes TNC a feasible diagnostic biomarker and target for molecular imaging to assess inflammation in the heart. Several preclinical studies have shown the utility of TNC as a biomarker for assessing the prognosis of patients and selecting appropriate therapy, particularly for inflammatory heart diseases.

Cardiac Fibroblasts and the Extracellular Matrix in Regenerative and Nonregenerative Hearts

During the postnatal period in mammals, the heart undergoes significant remodeling and cardiac cells progressively lose their embryonic characteristics. At the same time, notable changes in the extracellular matrix (ECM) composition occur with a reduction in the components considered facilitators of cellular proliferation, including fibronectin and periostin, and an increase in collagen fiber organization. Not much is known about the postnatal cardiac fibroblast which is responsible for producing the majority of the ECM, but during the days after birth, mammalian hearts can regenerate after injury with only a transient scar formation. This phenomenon has also been described in adult urodeles and teleosts, but relatively little is known about their cardiac fibroblasts or ECM composition. Here, we review the pre-existing knowledge about cardiac fibroblasts and the ECM during the postnatal period in mammals as well as in regenerative environments.

Circulating Proangiogenic Cells and Proteins in Patients with Glioma and Acute Myocardial Infarction: Differences in Neovascularization between Neoplasia and Tissue Regeneration

Although extensive angiogenesis takes place in glial tumors, antiangiogenic therapies have remained without the expected success. In the peripheral circulation of glioma patients, increased numbers of endothelial precursor cells (EPCs) are present, potentially offering targets for antiangiogenic therapy. However, for an antiangiogenic therapy to be successful, the therapy should specifically target glioma-related EPC subsets and secreted factors only. Here, we compared the EPC subsets and plasma factors in the peripheral circulation of patients with gliomas to acute myocardial infarctions. We investigated the five most important EPC subsets and 21 angiogenesis-related plasma factors in peripheral blood samples of 29 patients with glioma, 14 patients with myocardial infarction, and 20 healthy people as controls, by FACS and Luminex assay. In GBM patients, all EPC subsets were elevated as compared to healthy subjects. In addition, HPC and KDR⁺ cell fractions were higher than in MI, while CD133⁺ and KDR⁺CD133⁺ cell fractions were lower. There were differences in relative EPC fractions between the groups: KDR⁺ cells were the largest fraction in GBM, while CD133⁺ cells were the largest fraction in MI. An increase in glioma malignancy grade coincided with an increase in the KDR⁺ fraction, while the CD133⁺ cell fraction decreased relatively. Most plasma angiogenic factors were higher in GBM than in MI patients. In both MI and GBM, the ratio of CD133⁺ HPCs correlated significantly with elevated levels of MMP9. In the GBM patients, MMP9 correlated strongly with levels of all HPCs. In conclusion, the data demonstrate that EPC traffic in patients with glioma, representing neoplasia, is different from that in myocardial infarction, representing tissue regeneration. Glioma patients may benefit from therapies aimed at lowering KDR⁺ cells and HPCs.

Future perspectives of nanoparticle-based contrast agents for cardiac magnetic resonance in myocardial infarction

Cardiac Magnetic Resonance (CMR), thanks to high spatial resolution and absence of ionizing radiation, has been widely used in myocardial infarction (MI) assessment to evaluate cardiac structure, function, perfusion and viability. Nevertheless, it suffers from limitations in tissue and assessment of myocardial pathophysiological changes subsequent to MI. In this issue, nanoparticle-based contrast agents offer the possibility to track biological processes at cellular and molecular level underlying the various phases of MI, infarct healing and tissue repair. In this paper, first we examine the conventional CMR protocol and its findings in MI patients. Next, we looked at how nanoparticles can help in the imaging of MI and give an overview of the major approaches currently explored. Based on the presentation of successful nanoparticle applications as contrast agents (CAs) in preclinical and clinical models, we discuss promises and outstanding challenges facing the field of CMR in MI, their translational potential and clinical application.

Tenascin‑C promotes the migration of bone marrow stem cells via toll‑like receptor 4‑mediated signaling pathways: MAPK, AKT and Wnt

There are currently limitations in stem cell therapy due to the low rate of homing and proliferation of cells following transplantation. The present study was designed to investigate the effects of Tenascin-C (TN-C) on bone marrow mesenchymal stem cells (BMSCs) and its underlying mechanisms. BMSCs were obtained from C57BL/6 mice. The survival and proliferation of BMSCs was analyzed by Cell Counting Kit-8 assay, migration was evaluated using the Transwell method, and differentiation was assessed by immunocytochemistry and immunofluorescence. In addition, the levels of proteins were detected by western blotting. High concentrations of TN-C promoted the migration of BMSCs. H₂O₂ at concentrations of 60–90 µmol/ml induced cell death in BMSCs, and thus, it was used to simulate oxidative stress in the microenvironment of acute myocardial infarction (AMI). High concentrations of TN-C were able to protect BMSCs from cell death, and promoted the migration of BMSCs (P<0.05). However, TAK-242 [the inhibitor of Toll-like receptor 4, (TLR4)] reduced the promoting effect of TN-C (P<0.05). By contrast, TN-C had no effect on the proliferation and differentiation of BMSCs. TN-C reduced the phosphorylation levels of p38 mitogen-activated protein kinase (MAPK), and increased the phosphorylation levels of Ser473 protein kinase B (AKT) and β-catenin, all of which were inhibited by TAK-242 (P<0.05). In the simulated AMI microenvironment, TN-C promoted the migration of BMSCs via TLR4-mediated signaling pathways, including MAPK, AKT and Wnt.

Tenascin-C Is a Major Component of the Fibrogenic Niche in Kidney Fibrosis

Kidney fibrosis initiates at certain focal sites in which the fibrogenic niche provides a specialized microenvironment that facilitates fibroblast activation and proliferation. However, the molecular identity of these fibrogenic niches is poorly characterized. Here, we determined whether tenascin-C (TNC), an extracellular matrix glycoprotein, is a component of the fibrogenic niche in kidney fibrosis. In vivo, TNC expression increased rapidly in kidneys subjected to unilateral ureteral obstruction or ischemia/reperfusion injury and predominantly localized at the foci rich in fibroblasts in renal interstitium. In vitro, TNC selectively promoted renal interstitial fibroblast proliferation, bromodeoxyuridine incorporation, and the expression of proliferation-related genes. The mitogenic activity of TNC required the integrin/focal adhesion kinase/mitogen-activated protein kinase signaling cascade. Using decellularized extracellular matrix scaffolds, we found that TNC-enriched scaffolds facilitated fibroblast proliferation, whereas TNC-deprived scaffolds inhibited proliferation. Matrix scaffold prepared from fibrotic kidney also promoted greater ex vivo fibroblast proliferation than did scaffolds prepared from healthy kidney. Conversely, small interfering RNA-mediated knockdown of TNC in vivo repressed injury-induced fibroblast expansion and renal fibrosis. These studies identify TNC as a major constituent of the fibrogenic niche that promotes fibroblast proliferation, and illustrate a pivotal role for the TNC-enriched microenvironment in kidney fibrogenesis.

Myocardial extracellular matrix: an ever-changing and diverse entity

The cardiac extracellular matrix (ECM) is a complex architectural network consisting of structural and nonstructural proteins, creating strength and plasticity. The nonstructural compartment of the ECM houses a variety of proteins, which are vital for ECM plasticity, and can be divided into 3 major groups: glycoproteins, proteoglycans, and glycosaminoglycans. The common denominator for these groups is glycosylation, which refers to the decoration of proteins or lipids with sugars. This review will discuss the fundamental role of the matrix in cardiac development, homeostasis, and remodeling, from a glycobiology point of view. Glycoproteins (eg, thrombospondins, secreted protein acidic and rich in cysteine, tenascins), proteoglycans (eg, versican, syndecans, biglycan), and glycosaminoglycans (eg, hyaluronan, heparan sulfate) are upregulated on cardiac injury and regulate key processes in the remodeling myocardium such as inflammation, fibrosis, and angiogenesis. Albeit some parallels can be made regarding the processes these proteins are involved in, their specific functions are extremely diverse. In fact, under varying conditions, individual proteins can even have opposing functions, making spatiotemporal contribution of these proteins in the rearrangement of multifaceted ECM very hard to grasp. Alterations of protein characteristics by the addition of sugars may explain the immense, yet tightly regulated, variability of the remodeling cardiac matrix. Understanding the role of glycosylation in altering the ultimate function of glycoproteins, proteoglycans, and glycosaminoglycans in the myocardium may lead to the development of new biochemical structures or compounds with great therapeutic potential for patients with heart disease.

In vivo imaging of tissue-remodeling activity involving infiltration of macrophages by a systemically administered protease-activatable probe in colon cancer tissues

This study evaluated the detection of tumors using in vivo imaging with a commercially available and systemically administered protease-activatable fluorescent probe, ProSense. To this end, we analyzed the delivery and uptake of ProSense as well as the target protease and its cellular source in a mouse xenograft tumor model. In vivo and ex vivo multi wavelength imaging revealed that ProSense signals accumulated within tumors, with preferential distribution in the vascular leakage area that correlates with vasculature development at the tumor periphery. Immunohistochemically, cathepsin B, which is targeted by ProSense, was specifically localized in macrophages. The codistribution of tenascin C immunoreactivity and gelatinase activity provided evidence of tissue-remodeling at the tumor periphery. Furthermore, in situ zymography revealed extracellular ProSense cleavage in such areas. Colocalization of cathepsin B expression and ProSense signals showing reduction by addition of cathepsin B inhibitor was confirmed in cultured macrophage-derived RAW264.7 cells. These results suggest that increased tissue-remodeling activity involving infiltration of macrophages is a mechanism that may be responsible for the tumor accumulation of ProSense signals in our xenograft model. We further confirmed ProSense signals at the tumor margin showing cathepsin B(+) macrophage infiltration in a rat colon carcinogenesis model. Together, these data demonstrate that systemically administered protease-activatable probes can effectively detect cancer invasive fronts, where tissue-remodeling activity is high to facilitate neoplastic cell invasion.

Clinical implications of tenascin-C and OX40 ligand in patients with acute coronary syndrome

Acute coronary syndrome (ACS) typically occurs when coronary artery disease results in the obstruction of the coronary arteries. Tenascin-C (TNC) and OX40 ligand (OX40L) were shown to be involved in the pathogenesis of atherosclerosis. In this study, 50 healthy controls and 170 patients, including 50 patients with stable angina (SA), 70 with unstable angina and 50 with acute myocardial infarction, were evaluated to assess serum TNC and plasma OX40L levels. The serum TNC levels were measured by a quantitative automated particle-enhanced immunonephelometric assay. ELISA was used to determine the expression levels of OX40L. All the coronary stenoses with a ≥30% diameter reduction were assessed by angiographic coronary stenosis morphology. The patients with ACS exhibited a significant increase in TNC expression levels (39.39±19.80 ng/ml) compared to the levels in the control and SA groups (28.65±12.32 ng/ml, P<0.01 and 31.22±18.92 ng/ml, P<0.05, respectively). The levels of OX40L were also found to be higher in patients with ACS (38.59±15.76 ng/ml) compared to those in the control and SA groups (19.42±11.19 ng/ml, P<0.001 and 21.52±10.30 ng/ml, P<0.001, respectively). The TNC and OX40L levels were positively correlated with each other (r₁=0.68; P<0.001) and with fibrinogen levels (r₃=0.76 and r₄=0.45, respectively; P<0.001). A positive correlation was also observed between the expression of TNC and OX40L and complex coronary stenosis (r₅=0.69 and r₆=0.55, respectively; P<0.001). We concluded that TNC and OX40L may act synergistically in coronary plaque formation and may be also be involved in the pathogenesis of coronary lesions. Patients with ACS exhibited increased TNC and OX40L expression levels, which may have created a prothrombotic milieu, aggravating the development of atherosclerosis and the instability of atherosclerotic plaques. Therefore, the expression of TNC and OX40L may be a valuable marker for predicting the severity of ACS.

Assessment of tenascin-C levels in ventricular noncompaction/hypertrabeculation patients: a cross-sectional study

PURPOSE

Ventricular noncompaction/hypertrabeculation (NC/HT) is a rare form of congenital cardiomyopathy. We aimed to investigate the presence of serum tenascin-C (TN-C) in adult patients with NC/HT and evaluate its value.

METHODS AND RESULTS

Serum TN-C levels were measured by ELISA in 50 NC/HT patients both with/without systolic dysfunction and in 23 normal controls. Systolic dysfunction was defined as ejection fraction (EF) ≤ 40. Mann-Whitney U-test and ROC curve analysis were done. Of 49 NC/HT patients, 24 (49%) patients had systolic dysfunction (mean age 36 ± 15) and 25 patients (51%) had normal systolic function (mean age 36 ± 17). The ages between groups were not different. The mean levels of serum TN-C in patients with or without systolic dysfunction were 26 ± 10 ng/mL and 26 ± 8 ng/mL respectively, compared to normal controls, 7 ± 2 ng/mL (P < 0.001). No significance was observed between 2 groups of NC/HT patients regarding TN-C levels (P = 0.8). The ROC curve analysis revealed that a TN-C value of 11.7 ng/mL identified patients with NC/HT with 100% sensitivity and specifity.

CONCLUSION

High serum TN-C levels are present in adult NC/HT cardiomyopathy even when left ventricular systolic function remains normal. Also, serum TN-C levels could be regarded as a candidate biomarker in the diagnosis of NC/HT which needs to be tested in larger prospective studies.