Temporary augmentation of glycosaminoglycans content in the heart after left coronary artery ligation

Serum collected from rats with myocardial infarction increases extracellular matrix accumulation by myofibroblasts isolated from myocardial infarction scar

The effect on extracellular matrix content is believed to be an average of several serum derived compounds acting in opposition. The aim of the study is to determine whether whole serum of rats with myocardial infarction may modify the accumulation of extracellular matrix in cultures of myofibroblasts isolated from the myocardial infarction scar. A second aim is to determine whether the tested serum can also degranulate the mast cells. Serum was collected from rats with sham myocardial infarction, rats with myocardial infarction induced by coronary artery ligation and control animals. The experiments were carried out on myocardial infarction scar myofibroblasts or mast cells from the peritoneal cavity. The cultures were divided into three groups containing eight cultures each: one treated with serum from control rats, from animals after sham operation or from those after myocardial infarction. In all groups, the serum was used at concentrations of 10%, 20% or 30%. The total collagen content (Woesner method) glycosaminoglycan level (Farandale method), cell proliferation (BrdU), histamine secretion from mast cells (spectrofluorymetry), β1 integrin and α-smooth muscle actin expression (flow cytometry) were evaluated. Isolated cells were α-smooth muscle actin positive and identified as myofibroblasts. Serum derived from rats with myocardial infarction increased collagen and glycosaminoglycan content in the cultures and modified myofibroblast proliferation in a concentration-dependent manner. The serum also results in an imbalance between collagen and glycosaminoglycan levels. The content of β1 integrin was not influenced by myocardial infarction serum. The serum of rats with myocardial infarction is involved in regulation of collagen and glycosaminoglycan content in myofibroblast cultures, as well as the modification of their proliferation. These changes were not accompanied with integrin β1 density variations. The serum of the myocardial infarction rats did not influence the mast cell degranulation.

Cardiac glycosaminoglycans and structural alterations during chronic stress-induced depression-like behavior in mice

Major depressive disorder (MDD) is an independent risk factor for cardiovascular disease (CVD) and its complications; however, causal mechanisms remain unclear. In the present study, we investigate cardiac structural and functional alterations and associated changes in myocardial glycosaminoglycans (GAGs) disaccharide profile in mice that exhibit depression-like behavior. Mice were assigned to the chronic mild stress (CMS) group and nonstress control group (CT). The CMS group was exposed to a series of mild, unpredictable stressors for 7 wk. Mice in the CMS group show a significant decrease in protein expression of hippocampal brain-derived neurotrophic factor (BDNF) and exhibit depression-like behavioral changes, such as learned helplessness and decreased exploration behavior, as compared with the control group. Although cardiac function remained unchanged between the groups, echocardiography analysis showed slightly increased left ventricular wall thickness in the CMS group. Furthermore, the CMS group shows an increase in cardiomyocyte cross-sectional area and an associated decrease in BDNF protein expression and increase in IL-6 mRNA expression, when compared with control mice. GAG disaccharide analysis of the left ventricles of the CMS and CT mice revealed an elevation in heparan (HS) and chondroitin sulfate (CS) content in the CMS hearts (35.3% and 17.9%, respectively, vs. control group). Furthermore, we also observed that unsulfated or monosulfated disaccharides were the most abundant units; however, we did not find any significant difference in mole percent or sulfation pattern of HS/CS disaccharides between the groups. The current investigation highlights a need for further research to explore the relationship between cardiac GAGs biology and myocardial remodeling as a causal mechanism that underlie cardiovascular complications in patients with MDD.NEW & NOTEWORTHY Comorbidity between depression and CVD is well established, whereas its etiology, especially the role of nonfibrous components (proteoglycans/GAGs) of the extracellular matrix, is unexplored. To the best of our knowledge, this is the first study to characterize cardiac proteoglycan/glycosaminoglycan profile in response to depression-like behavioral changes in mice. We observed that chronic mild stress (CMS)-induced depression-like behavior and alterations in glycosaminoglycan profile were associated with structural changes in the heart.

Targeting Chondroitin Sulfate Glycosaminoglycans to Treat Cardiac Fibrosis in Pathological Remodeling

Background:

Heart failure is a leading cause of mortality and morbidity, and the search for novel therapeutic approaches continues. In the monogenic disease mucopolysaccharidosis VI, loss-of-function mutations in arylsulfatase B lead to myocardial accumulation of chondroitin sulfate (CS) glycosaminoglycans, manifesting as myriad cardiac symptoms. Here, we studied changes in myocardial CS in nonmucopolysaccharidosis failing hearts and assessed its generic role in pathological cardiac remodeling.

Methods:

Healthy and diseased human and rat left ventricles were subjected to histological and immunostaining methods to analyze glycosaminoglycan distribution. Glycosaminoglycans were extracted and analyzed for quantitative and compositional changes with Alcian blue assay and liquid chromatography–mass spectrometry. Expression changes in 20 CS-related genes were studied in 3 primary human cardiac cell types and THP-1–derived macrophages under each of 9 in vitro stimulatory conditions. In 2 rat models of pathological remodeling induced by transverse aortic constriction or isoprenaline infusion, recombinant human arylsulfatase B (rhASB), clinically used as enzyme replacement therapy in mucopolysaccharidosis VI, was administered intravenously for 7 or 5 weeks, respectively. Cardiac function, myocardial fibrosis, and inflammation were assessed by echocardiography and histology. CS-interacting molecules were assessed with surface plasmon resonance, and a mechanism of action was verified in vitro.

Results:

Failing human hearts displayed significant perivascular and interstitial CS accumulation, particularly in regions of intense fibrosis. Relative composition of CS disaccharides remained unchanged. Transforming growth factor–β induced CS upregulation in cardiac fibroblasts. CS accumulation was also observed in both the pressure-overload and the isoprenaline models of pathological remodeling in rats. Early treatment with rhASB in the transverse aortic constriction model and delayed treatment in the isoprenaline model proved rhASB to be effective at preventing cardiac deterioration and augmenting functional recovery. Functional improvement was accompanied by reduced myocardial inflammation and overall fibrosis. Tumor necrosis factor–α was identified as a direct binding partner of CS glycosaminoglycan chains, and rhASB reduced tumor necrosis factor–α—induced inflammatory gene activation in vitro in endothelial cells and macrophages.

Conclusions:

CS glycosaminoglycans accumulate during cardiac pathological remodeling and mediate myocardial inflammation and fibrosis. rhASB targets CS effectively as a novel therapeutic approach for the treatment of heart failure.

Myocardial expression of PDECGF is associated with extracellular matrix remodeling in experimental myocardial infarction in rats

Platelet-derived endothelial cell growth factor (PDECGF) is a potent angiogenic peptide with anti-apoptotic activity expressed widely in tumours. However, its expression in myocardial infarction (MI) is not yet established. This study aimed to assess the myocardial expression of PDECGF in rats after MI. Extracellular matrix (ECM) remodeling plays an important role in angiogenesis; hence, changes in the ECM components were investigated in the myocardium after MI, which was induced in rats by coronary artery ligation (CAL) and verified using biochemical markers and histopathology. Immunohistochemistry, RT-PCR, and activity assays identified the expression pattern of PDECGF on days 1, 2, 4, 8, 16, and 32 after CAL. The levels of TNF-alpha, MMP-2, collagen, and glycosaminoglycans in the ECM were assessed. Studies on immunohistochemistry, RT-PCR, and PDECGF activity demonstrated elevated levels of PDECGF expression from day 2 after CAL. Macrophages, endothelial cells, fibroblasts, and cardiomyocytes, especially at the border region of the lesion, showed an enhanced expression for PDECGF. Remodeling of the ECM was depicted by changes in the levels of TNF-alpha, MMP-2, collagen, and GAG. Hence, this study clearly indicated PDECGF as an important angiogenic molecule expressed during MI and the alterations in ECM components facilitated the process of angiogenesis.

Regulatory influence of melatonin on collagen accumulation in the infarcted heart scar

The regulatory influence of the pineal gland on superficial wound healing and collagen content is documented. The aim of the present study was to determine whether the pineal gland and its secretory product melatonin regulate collagen accumulation in the scar of the infarcted heart and to explain the mechanisms of its action. To induce myocardial infarction in rats the left coronary artery was ligated. Metoprolol at the dose of 0.2 mg/100 g body weight (b.w.) was injected intraperitoneally to inhibit melatonin secretion. Pinealectomy was performed on some animals. For the in vitro study, cells were isolated from the heart scar and cultured in Dulbecco's modified Eagle medium with 3% fetal calf serum and antibiotics. Collagen content was evaluated as hydroxyproline content according to the Woessner method. Melatonin subcutaneously injected into the rats at the doses of 30 microg/100 g or 60 microg/100 g b.w. increased collagen accumulation in the heart scar. The doses of 3 microg/100 g b.w. and 300 microg/100 g b.w. were not effective. Surgical and pharmacological pinealectomies had opposite effects and reduced collagen content in the scar. However, melatonin administration (60 microg/100 g b.w.) to pinealectomized rats reversed the effect of pinealectomy and normalized collagen levels in heart after infarction. Cells isolated from the heart scar were identified as myofibroblasts. Melatonin (10(-7)-10(-8) m) increased collagen accumulation in the cultures. Collagen accumulation in the scar of the infarcted heart is regulated by melatonin and it exerts effects directly on the myofibroblasts of the infarcted area. Therefore, melatonin-induced collagen accumulation in the infarcted heart could be considered as the event improving the tensile strength of the scar and retarding the development of complications.