Heparan sulfate proteoglycans mediate a potent inhibitory signal for migration of vascular smooth muscle cells

Methyl donor diet attenuates intimal hyperplasia after vascular injury in rats

Environmental factors, particularly dietary habits, play an important role in cardiovascular disease susceptibility and progression through epigenetic modification. Previous studies have shown that hyperplastic vascular intima after endarterectomy is characterized by genome-wide hypomethylation. The purpose of this study was to investigate whether methyl donor diet affects intimal hyperplasia and the possible mechanisms involved. Intimal hyperplasia was induced in SD rats by carotid artery balloon injury. From 8 d before surgery to 28 d after surgery, the animals were fed a normal diet (ND) or a methyl donor diet (MD) supplemented with folic acid, vitamin B12, choline, betaine, and zinc. Carotid artery intimal hyperplasia was observed by histology, the effect of MD on carotid protein expression was analyzed by proteomics, functional clustering, signaling pathway, and upstream-downstream relationship of differentially expressed proteins were analyzed by bioinformatics. Results showed that MD attenuated balloon injury-induced intimal hyperplasia in rat carotid arteries. Proteomic analysis showed that there were many differentially expressed proteins in the common carotid arteries of rats fed with two different diets. The differentially expressed proteins are mainly related to the composition and function of the extracellular matrix (EMC), and changes in the EMC can lead to vascular remodeling by affecting fibrosis and stiffness of the blood vessel wall. Changes in the levels of vasculotropic proteins such as S100A9, ILF3, Serpinh1, Fbln5, LOX, HSPG2, and Fmod may be the reason why MD attenuates intimal hyperplasia. Supplementation with methyl donor nutrients may be a beneficial measure to prevent pathological vascular remodeling after injury.

Application of decellularized vascular matrix in small-diameter vascular grafts

Coronary artery bypass grafting (CABG) remains the most common procedure used in cardiovascular surgery for the treatment of severe coronary atherosclerotic heart disease. In coronary artery bypass grafting, small-diameter vascular grafts can potentially replace the vessels of the patient. The complete retention of the extracellular matrix, superior biocompatibility, and non-immunogenicity of the decellularized vascular matrix are unique advantages of small-diameter tissue-engineered vascular grafts. However, after vascular implantation, the decellularized vascular matrix is also subject to thrombosis and neoplastic endothelial hyperplasia, the two major problems that hinder its clinical application. The keys to improving the long-term patency of the decellularized matrix as vascular grafts include facilitating early endothelialization and avoiding intravascular thrombosis. This review article sequentially introduces six aspects of the decellularized vascular matrix as follows: design criteria of vascular grafts, components of the decellularized vascular matrix, the changing sources of the decellularized vascular matrix, the advantages and shortcomings of decellularization technologies, modification methods and the commercialization progress as well as the application prospects in small-diameter vascular grafts.

Biomechanical Assessment of Macro-Calcification in Human Carotid Atherosclerosis and Its Impact on Smooth Muscle Cell Phenotype

Intimal calcification and vascular stiffening are predominant features of end-stage atherosclerosis. However, their role in atherosclerotic plaque instability and how the extent and spatial distribution of calcification influence plaque biology remain unclear. We recently showed that extensive macro calcification can be a stabilizing feature of late-stage human lesions, associated with a reacquisition of more differentiated properties of plaque smooth muscle cells (SMCs) and extracellular matrix (ECM) remodeling. Here, we hypothesized that biomechanical forces related to macro-calcification within plaques influence SMC phenotype and contribute to plaque stabilization. We generated a finite element modeling (FEM) pipeline to assess plaque tissue stretch based on image analysis of preoperative computed tomography angiography (CTA) of carotid atherosclerotic plaques to visualize calcification and soft tissues (lipids and extracellular matrix) within the lesions. Biomechanical stretch was significantly reduced in tissues in close proximity to macro calcification, while increased levels were observed within distant soft tissues. Applying this data to an in vitro stretch model on primary vascular SMCs revealed upregulation of typical markers for differentiated SMCs and contractility under low stretch conditions but also impeded SMC alignment. In contrast, high stretch conditions in combination with calcifying conditions induced SMC apoptosis. Our findings suggest that the load bearing capacities of macro calcifications influence SMC differentiation and survival and contribute to atherosclerotic plaque stabilization.

Perlecan, A Multi-Functional, Cell-Instructive, Matrix-Stabilizing Proteoglycan With Roles in Tissue Development Has Relevance to Connective Tissue Repair and Regeneration

This review highlights the multifunctional properties of perlecan (HSPG2) and its potential roles in repair biology. Perlecan is ubiquitous, occurring in vascular, cartilaginous, adipose, lymphoreticular, bone and bone marrow stroma and in neural tissues. Perlecan has roles in angiogenesis, tissue development and extracellular matrix stabilization in mature weight bearing and tensional tissues. Perlecan contributes to mechanosensory properties in cartilage through pericellular interactions with fibrillin-1, type IV, V, VI and XI collagen and elastin. Perlecan domain I - FGF, PDGF, VEGF and BMP interactions promote embryonic cellular proliferation, differentiation, and tissue development. Perlecan domain II, an LDLR-like domain interacts with lipids, Wnt and Hedgehog morphogens. Perlecan domain III binds FGF-7 and 18 and has roles in the secretion of perlecan. Perlecan domain IV, an immunoglobulin repeat domain, has cell attachment and matrix stabilizing properties. Perlecan domain V promotes tissue repair through interactions with VEGF, VEGF-R2 and α2β1 integrin. Perlecan domain-V LG1-LG2 and LG3 fragments antagonize these interactions. Perlecan domain V promotes reconstitution of the blood brain barrier damaged by ischemic stroke and is neurogenic and neuroprotective. Perlecan-VEGF-VEGFR2, perlecan-FGF-2 and perlecan-PDGF interactions promote angiogenesis and wound healing. Perlecan domain I, III and V interactions with platelet factor-4 and megakaryocyte and platelet inhibitory receptor promote adhesion of cells to implants and scaffolds in vascular repair. Perlecan localizes acetylcholinesterase in the neuromuscular junction and is of functional significance in neuromuscular control. Perlecan mutation leads to Schwartz-Jampel Syndrome, functional impairment of the biomechanical properties of the intervertebral disc, variable levels of chondroplasia and myotonia. A greater understanding of the functional working of the neuromuscular junction may be insightful in therapeutic approaches in the treatment of neuromuscular disorders. Tissue engineering of salivary glands has been undertaken using bioactive peptides (TWSKV) derived from perlecan domain IV. Perlecan TWSKV peptide induces differentiation of salivary gland cells into self-assembling acini-like structures that express salivary gland biomarkers and secrete α-amylase. Perlecan also promotes chondroprogenitor stem cell maturation and development of pluripotent migratory stem cell lineages, which participate in diarthrodial joint formation, and early cartilage development. Recent studies have also shown that perlecan is prominently expressed during repair of adult human articular cartilage. Perlecan also has roles in endochondral ossification and bone development. Perlecan domain I hydrogels been used in tissue engineering to establish heparin binding growth factor gradients that promote cell migration and cartilage repair. Perlecan domain I collagen I fibril scaffolds have also been used as an FGF-2 delivery system for tissue repair. With the availability of recombinant perlecan domains, the development of other tissue repair strategies should emerge in the near future. Perlecan co-localization with vascular elastin in the intima, acts as a blood shear-flow endothelial sensor that regulates blood volume and pressure and has a similar role to perlecan in canalicular fluid, regulating bone development and remodeling. This complements perlecan’s roles in growth plate cartilage and in endochondral ossification to form the appendicular and axial skeleton. Perlecan is thus a ubiquitous, multifunctional, and pleomorphic molecule of considerable biological importance. A greater understanding of its diverse biological roles and functional repertoires during tissue development, growth and disease will yield valuable insights into how this impressive proteoglycan could be utilized successfully in repair biology.

The Unifying Hypothesis of Alzheimer's Disease: Heparan Sulfate Proteoglycans/Glycosaminoglycans Are Key as First Hypothesized Over 30 Years Ago

The updated "Unifying Hypothesis of Alzheimer's disease" (AD) is described that links all the observed neuropathology in AD brain (i.e., plaques, tangles, and cerebrovascular amyloid deposits), as well as inflammation, genetic factors (involving ApoE), "AD-in-a-Dish" studies, beta-amyloid protein (Aβ) as a microbial peptide; and theories that bacteria, gut microflora, gingivitis and viruses all play a role in the cause of AD. The common link is the early accumulation of heparan sulfate proteoglycans (HSPGs) and heparan sulfate glycosaminoglycans (GAGs). HS GAG accumulation and/or decreased HS GAG degradation is postulated to be the key initiating event. HS GAGs and highly sulfated macromolecules induce Aβ 1-40 (but not 1-42) to form spherical congophilic maltese-cross star-like amyloid core deposits identical to those in the AD brain. Heparin/HS also induces tau protein to form paired helical filaments (PHFs). Increased sulfation and/or decreased degradation of HSPGs and HS GAGs that occur due to brain aging leads to the formation of plaques and tangles in AD brain. Knockout of HS genes markedly reduce the accumulation of Aβ fibrils in the brain demonstrating that HS GAGs are key. Bacteria and viruses all use cell surface HS GAGs for entry into cells, including SARS-CoV-2. Bacteria and viruses cause HS GAGs to rapidly increase to cause near-immediate aggregation of Aβ fibrils. "AD-in-a-dish" studies use "Matrigel" as the underlying scaffold that spontaneously causes plaque, and then tangle formation in a dish. Matrigel mostly contains large amounts of perlecan, the same specific HSPG implicated in AD and amyloid disorders. Mucopolysaccharidoses caused by lack of specific HS GAG enzymes lead to massive accumulation of HS in lysosomal compartments in neurons and contribute to cognitive impairment in children. Neurons full of HS demonstrate marked accumulation and fibrillization of Aβ, tau, α-synuclein, and prion protein (PrP) in mucopolysaccharidosis animal models demonstrating that HS GAG accumulation is a precursor to Aβ accumulation in neurons. Brain aging leads to changes in HSPGs, including newly identified splice variants leading to increased HS GAG sulfation in the AD brain. All of these events lead to the new "Unifying Hypothesis of Alzheimer's disease" that further implicates HSPGs /HS GAGs as key (as first hypothesized by Snow and Wight in 1989).

The multifaceted roles of perlecan in fibrosis

Perlecan, or heparan sulfate proteoglycan 2 (HSPG2), is a ubiquitous heparan sulfate proteoglycan that has major roles in tissue and organ development and wound healing by orchestrating the binding and signaling of mitogens and morphogens to cells in a temporal and dynamic fashion. In this review, its roles in fibrosis are reviewed by drawing upon evidence from tissue and organ systems that undergo fibrosis as a result of an uncontrolled response to either inflammation or traumatic cellular injury leading to an over production of a collagen-rich extracellular matrix. This review focuses on examples of fibrosis that occurs in lung, liver, kidney, skin, kidney, neural tissues and blood vessels and its link to the expression of perlecan in that particular organ system.

Cardiovascular Risk Factors and Markers

Cardiovascular risk is assessed for the prediction and appropriate management of patients using collections of identified risk markers obtained from clinical questionnaire information, concentrations of certain blood molecules (e.g., N-terminal proB-type natriuretic peptide fragment and soluble receptors of tumor-necrosis factor-α and interleukin-2), imaging data using various modalities, and electrocardiographic variables, in addition to traditional risk factors.

Biomechanical Regulation of Mesenchymal Stem Cells for Cardiovascular Tissue Engineering

Mesenchymal stem cells (MSCs) are an appealing potential therapy for vascular diseases; however, many challenges remain in their clinical translation. While the use of biochemical, pharmacological, and substrate-mediated treatments to condition MSCs has been subjected to intense investigation, there has been far less exploration of using these treatments in combination with applied mechanical force for conditioning MSCs toward vascular phenotypes. This review summarizes the current understanding of the use of applied mechanical forces to differentiate MSCs into vascular cells and enhance their therapeutic potential for cardiovascular disease. First recent work on the use of material-based mechanical cues for differentiation of MSCs into vascular and cardiovascular phenotypes is examined. Then a summary of the studies using mechanical stretch or shear stress in combination with biochemical treatments to enhance vascular phenotypes in MSCs is presented.

Cellular and Molecular Mechanisms of Phenotypic Switch in Gastrointestinal Smooth Muscle

As a general rule, smooth muscle cells (SMC) are able to switch from a contractile phenotype to a less mature synthetic phenotype. This switch is accompanied by a loss of differentiation with decreased expression of contractile markers, increased proliferation as well as the synthesis and the release of several signaling molecules such as pro-inflammatory cytokines, chemotaxis-associated molecules, and growth factors. This SMC phenotypic plasticity has extensively been investigated in vascular diseases, but interest is also emerging in the field of gastroenterology. It has in fact been postulated that altered microenvironmental conditions, including the composition of microbiota, could trigger the remodeling of the enteric SMC, with phenotype changes and consequent alterations of contraction and impairment of gut motility. Several molecular actors participate in this phenotype remodeling. These include extracellular molecules such as cytokines and extracellular matrix proteins, as well as intracellular proteins, for example, transcription factors. Epigenetic control mechanisms and miRNA have also been suggested to participate. In this review key roles and actors of smooth muscle phenotypic switch, mainly in GI tissue, are described and discussed in the light of literature data available so far. J. Cell. Physiol. 231: 295-302, 2016. © 2015 Wiley Periodicals, Inc.

Mesoglycan attenuates VSMC proliferation through activation of AMP-activated protein kinase and mTOR

BACKGROUND

Vascular smooth muscle cells (VSMC) proliferation contributes significantly to intimal thickening in atherosclerosis and restenosis diseases. Platelet derived growth factor (PDGF) has been implicated in VSMC proliferation though the activation of multiple growth-promoting signals. Mesoglycan, a natural glycosaminoglycans preparation, is reported to show vascular protective effect. However, the mechanisms by which mesoglycan inhibits proliferation of VSMC are not fully understood. Here, we investigated whether mesoglycan exert therapeutic effect via AMP-activated protein kinase (AMPK) and its underlying mechanism.

METHODS

We cultured VSMC with increasing doses of mesoglycan. AMPK activation was measured by western blot analysis and cell proliferation was measured by flow cytometry.

RESULTS

Mesoglycan dose- and time- dependently increased the phosphorylation of AMPK (Thr(172)) and its upstream target, LKB1 (Ser(428)) and its downstream, ACC (Ser(79)) in VSMCs. Mesoglycan also blocked the PDGF-stimulated cell cycle progression through the G0/G1 arrest. AMPK DNα1, AMPK DNα2 or AMPK siRNA reduced the mesoglycan-mediated inhibition of VSMC proliferation. AMPK signaling activated by mesoglycan regulates mTOR phosphorylation which closely related to cell proliferation.

CONCLUSION

These data suggest that mesoglycan-induced AMPK activation suppress the VSMC proliferation via mTOR-dependent mechanism and mesoglycan may have beneficial effects on vascular proliferative disorders such as atherosclerosis.

The function of heparanase in diabetes and its complications

Heparan sulfate proteoglycans are ubiquitous glycoproteins that contain several heparan sulfate polysaccharide side chains attached to a core protein. They function not only as a primary structural component of the extracellular matrix, but also provide a storage depot for bioactive molecules, such as basic fibroblast growth factor, vascular endothelial growth factor and lipoprotein lipase. Heparanase is an endoglycosidase that specifically hydrolyzes heparan sulfate into oligosaccharides. Recent studies have indicated that heparanase is engaged in the initiation and progression of diabetes, in addition to its associated complications. This review focuses on the participation of heparanase in the cleavage of heparan sulfate proteoglycans in pancreatic islets promoting beta cell death, promotion of atherosclerosis, and its role in cardiac metabolic switching in the early stage of cardiomyopathy during diabetes. Understanding the mechanisms by which heparanase is regulated in diabetes could provide a drug target to prevent diabetes and its complications.

The sGC activator inhibits the proliferation and migration, promotes the apoptosis of human pulmonary arterial smooth muscle cells via the up regulation of plasminogen activator inhibitor-2

BACKGROUND

Different types of pulmonary hypertension (PH) share the same process of pulmonary vascular remodeling, the molecular mechanism of which is not entirely clarified by far. The abnormal biological behaviors of pulmonary arterial smooth muscle cells (PASMCs) play an important role in this process.

OBJECTIVES

We investigated the regulation of plasminogen activator inhibitor-2 (PAI-2) by the sGC activator, and explored the effect of PAI-2 on PASMCs proliferation, apoptosis and migration.

METHODS

After the transfection with PAI-2 overexpression vector and specific siRNAs or treatment with BAY 41-2272 (an activator of sGC), the mRNA and protein levels of PAI-2 in cultured human PASMCs were detected, and the proliferation, apoptosis and migration of PASMCs were investigated.

RESULTS

BAY 41-2272 up regulated the endogenous PAI-2 in PASMCs, on the mRNA and protein level. In PAI-2 overexpression group, the proliferation and migration of PASMCs were inhibited significantly, and the apoptosis of PASMCs was increased. In contrast, PAI-2 knockdown with siRNA increased PASMCs proliferation and migration, inhibited the apoptosis.

CONCLUSIONS

PAI-2 overexpression inhibits the proliferation and migration and promotes the apoptosis of human PASMCs. Therefore, sGC activator might alleviate or reverse vascular remodeling in PH through the up-regulation of PAI-2.

Heparan sulfate side chains have a critical role in the inhibitory effects of perlecan on vascular smooth muscle cell response to arterial injury

Perlecan is a proteoglycan composed of a 470-kDa core protein linked to three heparan sulfate (HS) glycosaminoglycan chains. The intact proteoglycan inhibits the smooth muscle cell (SMC) response to vascular injury. Hspg2(Δ3/Δ3) (MΔ3/Δ3) mice produce a mutant perlecan lacking the HS side chains. The objective of this study was to determine differences between these two types of perlecan in modifying SMC activities to the arterial injury response, in order to define the specific role of the HS side chains. In vitro proliferative and migratory activities were compared in SMC isolated from MΔ3/Δ3 and wild-type mice. Proliferation of MΔ3/Δ3 SMC was 1.5× greater than in wild type (P < 0.001), increased by addition of growth factors, and showed a 42% greater migratory response than wild-type cells to PDGF-BB (P < 0.001). In MΔ3/Δ3 SMC adhesion to fibronectin, and collagen types I and IV was significantly greater than wild type. Addition of DRL-12582, an inducer of perlecan expression, decreased proliferation and migratory response to PDGF-BB stimulation in wild-type SMC compared with MΔ3/Δ3. In an in vivo carotid artery wire injury model, the medial thickness, medial area/lumen ratio, and macrophage infiltration were significantly increased in the MΔ3/Δ3 mice, indicating a prominent role of the HS side chain in limiting vascular injury response. Mutant perlecan that lacks HS side chains had a marked reduction in the inhibition of in vitro SMC function and the in vivo arterial response to injury, indicating the critical role of HS side chains in perlecan function in the vessel wall.

Vascular biomechanical properties in mice with smooth muscle specific deletion of Ndst1

Heparan sulfate proteoglycans act as co-receptors for many chemokines and growth factors. The sulfation pattern of the heparan sulfate chains is a critical regulatory step affecting the binding of chemokines and growth factors. N-deacetylase-N-sulfotransferase1 (Ndst1) is one of the first enzymes to catalyze sulfation. Previously published work has shown that HSPGs alter tangent moduli and stiffness of tissues and cells. We hypothesized that loss of Ndst1 in smooth muscle would lead to significant changes in heparan sulfate modification and the elastic properties of arteries. In line with this hypothesis, the axial tangent modulus was significantly decreased in aorta from mice lacking Ndst1 in smooth muscle (SM22αcre(+)Ndst1(-/-), p < 0.05, n = 5). The decrease in axial tangent modulus was associated with a significant switch in myosin and actin types and isoforms expressed in aorta and isolated aortic vascular smooth muscle cells. In contrast, no changes were found in the compliance of smaller thoracodorsal arteries of SM22αcre(+)Ndst1(-/-) mice. In summary, the major findings of this study were that targeted ablation of Ndst1 in smooth muscle cells results in altered biomechanical properties of aorta and differential expression of myosin and actin types and isoforms.

Smooth muscle cell hypertrophy, proliferation, migration and apoptosis in pulmonary hypertension

Pulmonary hypertension is a multifactorial disease characterized by sustained elevation of pulmonary vascular resistance (PVR) and pulmonary arterial pressure (PAP). Central to the pathobiology of this disease is the process of vascular remodelling. This process involves structural and functional changes to the normal architecture of the walls of pulmonary arteries (PAs) that lead to increased muscularization of the muscular PAs, muscularization of the peripheral, previously nonmuscular, arteries of the respiratory acinus, formation of neointima, and formation of plexiform lesions. Underlying or contributing to the development of these lesions is hypertrophy, proliferation, migration, and resistance to apoptosis of medial cells and this article is concerned with the cellular and molecular mechanisms of these processes. In the first part of the article we focus on the concept of smooth muscle cell phenotype and the difficulties surrounding the identification and characterization of the cell/cells involved in the remodelling of the vessel media and we review the general mechanisms of cell hypertrophy, proliferation, migration and apoptosis. Then, in the larger part of the article, we review the factors identified thus far to be involved in PH intiation and/or progression and review and discuss their effects on pulmonary artery smooth muscle cells (PASMCs) the predominant cells in the tunica media of PAs.

Regulation and characteristics of vascular smooth muscle cell phenotypic diversity

Vascular smooth muscle cells can perform both contractile and synthetic functions, which are associated with and characterised by changes in morphology, proliferation and migration rates, and the expression of different marker proteins. The resulting phenotypic diversity of smooth muscle cells appears to be a function of innate genetic programmes and environmental cues, which include biochemical factors, extracellular matrix components, and physical factors such as stretch and shear stress. Because of the diversity among smooth muscle cells, blood vessels attain the flexibility that is necessary to perform efficiently under different physiological and pathological conditions. In this review, we discuss recent literature demonstrating the extent and nature of smooth muscle cell diversity in the vascular wall and address the factors that affect smooth muscle cell phenotype. (Neth Heart J 2007;15:100-8.).

Multiple mechanisms for exogenous heparin modulation of vascular endothelial growth factor activity

Heparin and heparin-like molecules are known to modulate the cellular responses to vascular endothelial growth factor-A (VEGF-A). In this study, we investigated the likely mechanisms for heparin's influence on the biological activity of VEGF-A. Previous studies have shown that exogenous heparin's effects on the biological activity of VEGF-A are many and varied, in part due to the endogenous cell-surface heparan sulfates. To circumvent this problem, we used mutant endothelial cells lacking cell-surface heparan sulfates. We showed that VEGF-induced cellular responses are dependent in part on the presence of the heparan sulfates, and that exogenous heparin significantly augments VEGF's cellular effects especially when endogenous heparan sulfates are absent. Exogenous heparin was also found to play a cross-bridging role between VEGF-A(165) and putative heparin-binding sites within its cognate receptor, VEGFR2 when they were examined in isolation. The cross-bridging appears to be more dependent on molecular weight than on a specific heparin structure. This was confirmed by surface plasmon resonance binding studies using sugar chips immobilized with defined oligosaccharide structures, which showed that VEGF-A(165) binds to a relatively broad range of sulfated glycosaminoglycan structures. Finally, studies of the far-UV circular dichroism spectra of VEGF-A(165) showed that heparin can also modulate the conformation and secondary structure of the protein.

PDGF receptor-{beta} modulates metanephric mesenchyme chemotaxis induced by PDGF AA

PDGF B chain or PDGF receptor (PDGFR)-beta-deficient (-/-) mice lack mesangial cells. To study responses of alpha- and beta-receptor activation to PDGF ligands, metanephric mesenchymal cells (MMCs) were established from embryonic day E11.5 wild-type (+/+) and -/- mouse embryos. PDGF BB stimulated cell migration in +/+ cells, whereas PDGF AA did not. Conversely, PDGF AA was chemotactic for -/- MMCs. The mechanism by which PDGFR-beta inhibited AA-induced migration was investigated. PDGF BB, but not PDGF AA, increased intracellular Ca(2+) and the production of reactive oxygen species (ROS) in +/+ cells. Transfection of -/- MMCs with the wild-type beta-receptor restored cell migration and ROS generation in response to PDGF BB and inhibited AA-induced migration. Inhibition of Ca(2+) signaling facilitated PDGF AA-induced chemotaxis in the wild-type cells. The antioxidant N-acetyl-l-cysteine (NAC) or the NADPH oxidase inhibitor diphenyleneiodonium (DPI) abolished the BB-induced increase in intracellular Ca(2+) concentration, suggesting that ROS act as upstream mediators of Ca(2+) in suppressing PDGF AA-induced migration. These data indicate that ROS and Ca(2+) generated by active PDGFR-beta play an essential role in suppressing PDGF AA-induced migration in +/+ MMCs. During kidney development, PDGFR beta-mediated ROS generation and Ca(2+) influx suppress PDGF AA-induced chemotaxis in metanephric mesenchyme.

Chemotaxis of human articular chondrocytes and mesenchymal stem cells

Migration of chondrocytes and mesenchymal stem cells (MSCs) may be important in cartilage development, tissue response to injury, and in tissue engineering. This study analyzed growth factors and cytokines for their ability to induce migration of human articular chondrocytes and bone marrow-derived mesenchymal stem cells in Boyden chamber assays. In human articular chondrocytes serum induced dose- and time-dependent increases in cell migration. Among a series of growth factors and cytokines tested only PDGF induced a significant increase in cell migration. The PDGF isoforms AB and BB were more potent than AA. There was an aging-related decline in the ability of chondrocytes to migrate in response to serum and PDGF. Human bone marrow MSC showed significant chemotaxis responses to several factors, including FBS, PDGF, VEGF, IGF-1, IL-8, BMP-4, and BMP-7. In summary, these results demonstrate that directed cell migration is inducible in human articular chondrocytes and MSC. PDGF is the most potent factor analyzed, and may be useful to promote tissue integration during cartilage repair or tissue engineering.

A heparin-bonded vascular graft generates no systemic effect on markers of hemostasis activation or detectable heparin-induced thrombocytopenia-associated antibodies in humans

OBJECTIVES

Almost a third of patients who undergo peripheral bypass procedures do not have suitable veins, making the use of prosthetic materials necessary. Prosthetic materials can cause platelet adhesion and activation of the coagulation cascade on the graft. One potential strategy to reduce this thrombogenicity is to covalently bind heparin to the endoluminal surface of grafts. This human in vivo study examined systemic effects of the endoluminal heparin and addressed whether graft implantation results in (1) a measurable reduction of systemic markers of hemostasis activation compared with control grafts and (2) antibody formation against heparin, potentially responsible for heparin-induced thrombocytopenia (HIT).

METHODS

The study included 20 patients undergoing femoropopliteal bypass grafting, of whom 10 received a standard Gore-Tex Thin Walled Stretch Vascular Graft (W. L. Gore & Associates, Flagstaff, Ariz) and 10 received a heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft (Gore-Tex Propaten Vascular Graft). Blood samples were drawn before and directly after the operation and at days 1, 3, 5, and week 6 after surgery. Established markers of in vivo activation of platelets and blood coagulation (prothrombin fragment 1+2, fibrinopeptide A, soluble glycoprotein V, thrombin-antithrombin complexes, and D-dimers) were measured using standard commercially available techniques. Antiplatelet factor 4/heparin antibody titers were measured using a commercially available enzyme-linked immunosorbent assay, and platelet counts were determined.

RESULTS

No statistical differences were observed in any of the markers of in vivo activation of platelets and blood coagulation between patients receiving Propaten or control ePTFE. Moreover, no antibodies against heparin could be demonstrated up to 6 weeks after implantation.

CONCLUSIONS

No measurable effect of heparin immobilization on systemic markers of hemostasis was found using a heparin-bonded ePTFE graft in vivo. Also, no antibodies against heparin could be detected up to 6 weeks after implantation.

Role of smooth muscle cells in the initiation and early progression of atherosclerosis

The initiation of atherosclerosis results from complex interactions of circulating factors and various cell types in the vessel wall, including endothelial cells, lymphocytes, monocytes, and smooth muscle cells (SMCs). Recent reviews highlight the role of activated endothelium and inflammatory cell recruitment in the initiation of and progression of early atherosclerosis. Yet, human autopsy studies, in vitro mechanistic studies, and in vivo correlative data suggest an important role for SMCs in the initiation of atherosclerosis. SMCs are the major producers of extracellular matrix within the vessel wall and in response to atherogenic stimuli can modify the type of matrix proteins produced. In turn, the type of matrix present can affect the lipid content of the developing plaque and the proliferative index of the cells that are adherent to it. SMCs are also capable of functions typically attributed to other cell types. Like macrophages, SMCs can express a variety of receptors for lipid uptake and can form foam-like cells, thereby participating in the early accumulation of plaque lipid. Like endothelial cells, SMCs can also express a variety of adhesion molecules such as vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 to which monocytes and lymphocytes can adhere and migrate into the vessel wall. In addition, through these adhesion molecules, SMCs can also stabilize these cells against apoptosis, thus contributing to the early cellularity of the lesion. Like many cells within the developing plaque, SMCs also produce many cytokines such as PDGF, transforming growth factor-beta, IFNgamma, and MCP-1, all of which contribute to the initiation and propagation of the inflammatory response to lipid. Recent advances in SMC-specific gene modulation have enhanced our ability to determine the role of SMCs in early atherogenesis.

Utility and control of proteoglycans in tissue engineering

This review addresses various methods of integrating proteoglycans (PGs) into the design of engineered tissues and provides insight for designing tissue-engineered disease models that leverage current knowledge of PG biology. Even though PGs show immense possibilities in tissue-engineering applications, they have seldom been used to their full potential. The most common tissue-engineering application of PGs has been in scaffolds (matrigels and collagen-chondroitin sulfate matrices), in which PGs or their glycosaminoglycan (GAG) chains are incorporated into the scaffold to promote cell growth, tissue remodeling, and intracellular signaling. In addition, many studies have reported the total amount of PGs synthesized within engineered tissues but have not delineated which specific PGs or GAG classes are involved in engineered tissue development. In native tissues, various PGs are dynamically and differentially regulated to achieve specific biophysical and biological functions, such as compressibility and transparency. Therefore, the targeted modulation of specific PGs (via exogenous addition, endogenous stimulation with growth factors, or mechanical stimulation) may help engineered tissues to achieve native tissue properties. The PG composition of engineered tissues could also be modified to achieve disease models in vitro and thus provide a way to study the effect of external agents on PG-related disease mechanisms.

The cell cycle: a critical therapeutic target to prevent vascular proliferative disease

Percutaneous coronary intervention is the preferred revascularization approach for most patients with coronary artery disease. However, this strategy is limited by renarrowing of the vessel by neointimal hyperplasia within the stent lumen (in-stent restenosis). Vascular smooth muscle cell proliferation is a major component in this healing process. This process is mediated by multiple cytokines and growth factors, which share a common pathway in inducing cell proliferation: the cell cycle. The cell cycle is highly regulated by numerous mechanisms ensuring orderly and coordinated cell division. The present review discusses current concepts related to regulation of the cell cycle and new therapeutic options that target aspects of the cell cycle.

Defective N-sulfation of heparan sulfate proteoglycans limits PDGF-BB binding and pericyte recruitment in vascular development

During vascular development, endothelial platelet-derived growth factor B (PDGF-B) is critical for pericyte recruitment. Deletion of the conserved C-terminal heparin-binding motif impairs PDGF-BB retention and pericyte recruitment in vivo, suggesting a potential role for heparan sulfate (HS) in PDGF-BB function during vascular development. We studied the participation of HS chains in pericyte recruitment using two mouse models with altered HS biosynthesis. Reduction of N-sulfation due to deficiency in N-deacetylase/N-sulfotransferase-1 attenuated PDGF-BB binding in vitro, and led to pericyte detachment and delayed pericyte migration in vivo. Reduced N-sulfation also impaired PDGF-BB signaling and directed cell migration, but not proliferation. In contrast, HS from glucuronyl C5-epimerase mutants, which is extensively N- and 6-O-sulfated, but lacks 2-O-sulfated L-iduronic acid residues, retained PDGF-BB in vitro, and pericyte recruitment in vivo was only transiently delayed. These observations were supported by in vitro characterization of the structural features in HS important for PDGF-BB binding. We conclude that pericyte recruitment requires HS with sufficiently extended and appropriately spaced N-sulfated domains to retain PDGF-BB and activate PDGF receptor beta (PDGFRbeta) signaling, whereas the detailed sequence of monosaccharide and sulfate residues does not appear to be important for this interaction.

Dietary manganese affects the concentration, composition and sulfation pattern of heparan sulfate glycosaminoglycans in Sprague-Dawley rat aorta

We examined the effect of dietary Mn on the composition and structure of heparan sulfate (HS) glycosaminoglycans (GAGs) of rat aorta. Animals were randomly assigned to either a Mn deficient (MnD), adequate (MnA) or supplemented (MnS) diet (Mn<1, 10-15 and 45-50 ppm, respectively). After 15 weeks, aortic tissue GAGs were isolated with papain digestion, alkaline borohydride treatment and anion-exchange chromatography. Cellulose acetate electrophoresis and treatment of the fractions with specific lyases revealed the presence of three GAG populations, i.e. hyaluronan (HA), heparan sulfate (HS) and galactosaminoglycans (GalAGs). Disaccharide composition of the HS fractions was determined by HPCE following treatment with heparin lyases I, II and III. In MnS aortas we observed increased concentration of total GalAGs and decreased concentration of HS and HA, when compared to MnA aortas. Aortas from MnD and MnA rats appeared to have similar distribution of individual GAGs. Heparan sulfate chains of MnS aortas contained higher (41%) concentration of non-sulfated units compared to MnA ones. Variable amounts of trisulfated and disulfated units were found only in MnD and MnA groups but not in MnS. Our results demonstrate that HS biosynthesis in the rat aorta undergoes marked structural modifications that depend upon dietary Mn intake. The reduced expression and undersulfation of HSPGs with Mn supplementation might indicate a reduced ability of vascular cells to interact with biologically active molecules such as growth factors. Alterations in cell-membrane binding ability to a variety of extracellular ligands might affect signal-transduction pathways and arterial functional properties.

Reduced perlecan expression and accumulation in human carotid atherosclerotic lesions

Heparan sulfate in the extracellular matrix of the artery wall has been proposed to possess anti-atherogenic properties by interfering with lipoprotein retention, suppression of inflammation, and inhibition of smooth muscle cell growth. Previously, the amount of heparan sulfate in atherosclerotic lesions from humans and animals has been shown to be reduced but the identity or identities of the heparan sulfate molecules being down regulated in this disease are not known. In this study, atherosclerotic lesions were retrieved from 44 patients undergoing surgery for symptomatic carotid stenosis. Normal iliac arteries from organ donors were used as controls. Analysis of the specimens by gene microarray showed a selective reduction in perlecan gene expression, whereas, expression of the other heparan sulfate proteoglycans in the artery wall, agrin and collagen XVIII, remained unchanged. Expression of the large chondroitin sulfate proteoglycan, versican, also remained unchanged. Real-time PCR confirmed the decrease in perlecan gene expression and the unchanged expression of versican. The findings were supported by immunohistochemical analysis demonstrating a reduced accumulation of both perlecan core protein and heparan sulfate in carotid lesions. The study demonstrates a reduction of perlecan mRNA-expression and protein deposition in human atherosclerosis, which in part explains the low levels of heparan sulfate in this disease.

Drug-Eluting Coronary Stents

The introduction and widespread use of coronary stents have been the most important advancement in the percutaneous treatment of coronary artery disease since the introduction of balloon angioplasty. Coronary artery stents reduce the rate of angiographic and clinical restenosis compared to balloon angioplasty. This angiographic restenosis was further reduced with the introduction of drug-eluting stents and hence further reduction in the frequency of major adverse cardiac events. Herein we present a comprehensive and up-to-date review about the use of drug-eluting stents in the treatment of coronary artery disease.

Reduced syndecan-4 expression in arterial smooth muscle cells with enhanced proliferation

Syndecans, a family of cell surface heparan sulfate (HS) containing proteoglycans (PGs), are known regulators of many biological processes including inhibition of smooth muscle cell (SMC) proliferation. Cultured arterial SMCs from atherosclerosis-susceptible White Carneau (WC) pigeons have increased proliferation rates and significant reductions in total cell-surface HS relative to atherosclerosis-resistant Show Racer (SR) SMC. Using a specific syndecan-4 cDNA, 1.5- to 2.0-fold reductions in gene expression were observed in WC SMC compared to SR SMC. Immunolocalization studies demonstrated reduced cell surface syndecan-4 protein in WC cells. Gene induction demonstrated that the reduction in syndecan-4 expression in WC cells was not due to reduced mRNA stability. Studies using cycloheximide to superinduce gene expression indicated transcriptional suppression of syndecan-4 in WC cells. The results suggest that reduced cell surface HS PG in WC arterial SMC can be explained, in part, by reductions in syndecan-4 gene expression. Differential transcriptional regulation of syndecan-4 in WC and SR cells provides a system to explore regulation of the syndecan-4 gene as well as the potential mechanisms by which syndecan-4 can exert a specific antiproliferative effect.

Ca(2+)/calmodulin-dependent protein kinase II inhibition by heparin in mesangial cells

Heparin exerts an antiproliferative effect in smooth muscle cells, and the Ca(2+)/calmodulin-dependent protein kinase (CaMK) signaling pathway is heparin sensitive. Here, we report that transfection with a truncated 326-amino acid fragment of CaMK-IIalpha increases basal activity of CaMK-II in mesangial cells. Ionomycin increased CaMK-II activity in both transfected and untransfected cells, with a concomitant increase in activated Ca(2+)/calmodulin. Heparin (1 microg/ml), but not chondroitin or dermatan sulfate, significantly attenuated both serum- or ionomycin-induced CaMK-II activity, and attendant c-fos mRNA expression, but did not affect upstream Ca(2+)/calmodulin. Autophosphorylation of Thr286 generates an autonomously active CaMK-II. Both serum and ionomycin increased phosphorylation at this site and increased CaMK-II activity in antiphosphothreonine immunoprecipitates. Heparin (1 microg/ml) did not inhibit phosphorylation of Thr286 (although much higher concentrations did). Replacement of Thr286 with Asp produces a constitutively active mutant that was insensitive to ionomycin but was inhibited by heparin maximally at 1 microg/ml. These results suggest that heparin at physiological concentrations acts at or downstream of CaMK-II to suppress its activity independent of an effect on autophosphorylation.

Impaired angiogenesis, delayed wound healing and retarded tumor growth in perlecan heparan sulfate-deficient mice

Perlecan, a modular proteoglycan carrying primary heparan sulfate (HS) side chains, is a major component of blood vessel basement membranes. It sequesters growth factors such as fibroblast growth factor 2 (FGF-2) and regulates the ligand-receptor interactions on the cell surface, and thus it has been implicated in the control of angiogenesis. Both stimulatory and inhibitory effects of perlecan on FGF-2 signaling have been reported. To understand the in vivo function of HS carried by perlecan, the perlecan gene heparan sulfate proteoglycan 2 (Hspg2) was mutated in mouse by gene targeting. The HS at the NH(2) terminus of perlecan was removed while the core protein remained intact. Perlecan HS-deficient (Hspg2(Delta3/Delta3)) mice survived embryonic development and were apparently healthy as adults. However, mutant mice exhibited significantly delayed wound healing, retarded FGF-2-induced tumor growth, and defective angiogenesis. In the mouse corneal angiogenesis model, FGF-2-induced neovascularization was significantly impaired in Hspg2(Delta3/Delta3) mutant mice. Our results suggest that HS in perlecan positively regulates the angiogenesis in vivo.

Distribution of syndecans 1-4 within the anterior segment of the human eye: expression of a variant syndecan-3 and matrix-associated syndecan-2

Control of the actomyosin network plays a role in regulating the movement of aqueous humor through the anterior segment of the eye. Receptors that could control its activity are unknown. In this study, we show that all four members of the syndecan family, which can regulate the actomyosin network, are present within the anterior segment. In both sections of human anterior segments and cultures of human trabecular meshwork (HTM), Schlemm's canal (HSC) and the ciliary muscle (HCM) cells from the anterior segment, syndecans-3 and -4 were the predominant family members. They were widely distributed throughout the anterior segment. Syndecan-3 within the anterior segment was a novel, recently described variant 55 kDa form. Low levels of syndecans-1 and -2 were also observed in situ and in all three cultures. Their expression was weaker and more localized than that observed for syndecans-3 and -4. Staining for syndecan-1 in HCM cultures was variable. In HTM and HSC cultures, syndecan-2 also co-distributed with fibronectin, laminin and type IV collagen suggesting that it was shed and associated with the extracellular matrix. Western blots supported this idea and showed syndecan-2 ectodomains in lysates from anterior segments.

Platelet-derived growth factor gene delivery stimulates ex vivo gingival repair

Destruction of tooth support due to the chronic inflammatory disease periodontitis is a major cause of tooth loss. There are limitations with available treatment options to tissue engineer soft tissue periodontal defects. The exogenous application of growth factors (GFs) such as platelet-derived growth factor (PDGF) has shown promise to enhance oral and periodontal tissue regeneration. However, the topical administration of GFs has not led to clinically significant improvements in tissue regeneration because of problems in maintaining therapeutic protein levels at the defect site. The utilization of PDGF gene transfer may circumvent many of the limitations with protein delivery to soft tissue wounds. The objective of this study was to test the effect of PDGF-A and PDGF-B gene transfer to human gingival fibroblasts (HGFs) on ex vivo repair in three-dimensional collagen lattices. HGFs were transduced with adenovirus encoding PDGF-A and PDGF-B genes. Defect fill of bilayer collagen gels was measured by image analysis of cell repopulation into the gingival defects. The modulation of gene expression at the defect site and periphery was measured by RT-PCR during a 10-day time course after gene delivery. The results demonstrated that PDGF-B gene transfer stimulated potent (>4-fold) increases in cell repopulation and defect fill above that of PDGF-A and corresponding controls. PDGF-A and PDGF-B gene expression was maintained for at least 10 days. PDGF gene transfer upregulated the expression of phosphatidylinosital 3-kinase and integrin alpha5 subunit at 5 days after adenovirus transduction. These results suggest that PDGF gene transfer has potential for periodontal soft tissue-engineering applications.

Concomitant blockade of platelet-derived growth factor receptors alpha and beta induces intimal atrophy in baboon PTFE grafts

OBJECTIVE

Although current treatments for restenosis attempt to prevent the development of intimal hyperplasia, an alternative strategy is to induce intimal atrophy after restenosis has developed. Because platelet-derived growth factor (PDGF) is a smooth muscle cell growth and survival factor, we tested the hypothesis that complete blockade of PDGF by using antibodies against PDGF receptors alpha and beta would cause intimal atrophy in a baboon vascular graft model.

METHODS

We administered chimeric antibodies against PDGF receptor alpha or PDGF receptor beta, either separately or together, to baboons with bilateral prosthetic aortoiliac grafts, the intimas of which had reached maximal size before treatment was begun. High blood flow, which we have previously shown to cause intimal atrophy, was induced through one graft to serve as a positive control. After 2 weeks, the intima lining the grafts was assessed for cross-sectional area, cell proliferation, and apoptosis by standard morphologic and immunohistochemical techniques.

RESULTS

Blocking both PDGF receptors simultaneously reduced the cross-sectional area of the normal-flow graft intima by 44% (P <.05 vs control), whereas treatment with the individual antibodies did not significantly alter intimal area. Blockade of both receptors also inhibited smooth muscle cell proliferation by 66% (P <.05 vs control), whereas neither antibody alone altered proliferation. In contrast, all treatments increased smooth muscle cell apoptosis threefold to fivefold.

CONCLUSIONS

These data suggest that simultaneous inhibition of cell proliferation and stimulation of cell death by the administration of antibodies to both PDGF receptor alpha and receptor beta is required for intimal atrophy in this baboon graft model. In addition, these data provide an in vivo model for the pharmacologic induction of intimal atrophy and introduce a novel clinical approach to treat intimal hyperplasia. Clinical relevance This study introduces the concept of pharmacologic induction of intimal atrophy. Intimal hyperplasia plagues all forms of arterial reconstruction. Currently, the only effective treatment of these restenotic lesions is balloon angioplasty or operative revision. An alternative approach to patients with clinically significant intimal hyperplasia might be to stimulate intimal regression by modulating growth and survival factors required for intimal maintenance. Although PDGF is known to be critical in intimal formation, the results of this study suggest that PDGF is also critical for intimal maintenance. Inhibition of the PDGF system may prove to be a clinically applicable approach for inducing intimal atrophy.

Suppression of mitogen-activated protein kinase phosphatase-1 (MKP-1) by heparin in vascular smooth muscle cells

Heparin inhibits vascular smooth muscle cell (VSMC) proliferation, but mechanisms remain elusive. Because heparin inhibits signaling through multiple kinase cascades, we investigated the possibility that phosphatases could be involved. Mitogen-activated protein kinase phosphatase-1 (MKP-1) was the predominant MKP detected in VSMC lines. MKP-1 protein was increased by serum stimulation of quiescent cells, and this increase was diminished by heparin (1 microg/mL). Increased MKP-1 expression was dependent on the mitogen-activated protein kinase, Erk. Decreased Erk activity in the presence of heparin preceded, and may account for, decreased MKP-1. The antimitogenic effects of heparin are therefore unlikely to act through a shift in the kinase/phosphatase balance, but rather through direct kinase suppression. However, because MKP-1 is known to cause an increase in activity of kinases upstream of Erk, that may signal through additional pathways, the decrease in MKP-1 activity may paradoxically enhance heparin's antiproliferative effects. VSMC selected to grow in the presence of heparin express decreased levels of MKP-1 that are unresponsive to heparin, and Erk activity becomes unresponsive to heparin in one cell line. We conclude that phosphatase activation is not a direct mechanism of suppression of multiple kinase cascades by heparin.

Heparin inhibits DNA synthesis and gene expression in alveolar type II cells

Responses of isolated type II alveolar cells to fibroblast growth factors (FGF) have been shown to be sensitive to the level of sulfation in extracellular matrix (ECM) substrata. These observations may reflect the specific in situ distribution and level of sulfation of ECM within the alveolar basement membranes (ABM) associated with type II cells. The goal of this study was to determine if the model sulfated ECM heparin modified DNA synthesis and gene expression by type II cells in a concentration dependent-manner. Isolated rat type II cells were exposed to different concentrations of heparin (0.005-500 micro g/ml) in serum-free medium for 1-3 d with or without FGF-1 or FGF-2. The effects of heparin were examined by [(3)H]thymidine incorporation into DNA, total cell protein, cell number, and selected gene expression. Results indicated that heparin inhibited [(3)H]thymidine uptake in a concentration-dependent manner. Total protein, cell number, and FGF-2 protein expression and mRNA of FGF-1, -2, and FGF receptor-2 detected by reverse transcriptase-polymerase chain reaction were decreased by heparin. These results demonstrate that sulfated molecules in the ABM may play important regulatory role(s) in selected type II cell activities during normal cell homeostasis, turnover, and repair after lung injury.

Early changes in proteoglycans production by resistance arteries smooth muscle cells of hypertensive rats

Several functional and structural modifications at the vascular level have been described in spontaneously hypertensive rats (SHR) during the early development of hypertension. In this study, we hypothesize that changes in the extracellular matrix (ECM) could precede the development of hypertension. Synthesis of secreted and membrane-bound sulfated proteoglycans (S-PG) by cultured vascular smooth muscle cells (VSMC) obtained from young spontaneously hypertensive rats (pSHR) mesenteric resistance arteries, during the period preceding the elevation of blood pressure (BP) was tested. After 24 h of stimulation with angiotensin II (Ang II), 10% fetal calf serum (FCS), or 0.1% FCS as control, medium and cell layer S-PG synthesis was evaluated by labeling sulfated disaccharides with [35S] sodium sulfate. To relate this variable with cell proliferation, DNA synthesis was measured by incorporation of [3H]thymidine in the cell lysate. The VSMC from pSHR synthesized more secreted and membrane-bound S-PG than age-matched Wistar rat (pW) cells in the nonstimulated (0.1% FCS) and stimulated (Ang II or 10% FCS) experimental groups. When data were expressed as percent of their own control value, both Ang II and 10% FCS lowered basal secreted and cell-associated S-PG content in VSMC from pSHR, whereas in pW rat cells, these agents produced a small increase or no change. An inverse relationship between proliferation and total S-PG production (secreted plus membrane-bound) was found in pSHR cells, but not in pW cells. In conclusion, the present study demonstrates that changes in S-PG synthesis by VSMC of resistance arteries precede the vascular dysfunction associated with the development of hypertension in SHR.

Differential effects of gemfibrozil on migration, proliferation and proteoglycan production in human vascular smooth muscle cells

The aim of this study was to determine, if gemfibrozil has anti-atherogenic actions on human vascular smooth muscle cells (SMCs) and whether these actions are affected by high glucose concentrations, which mimic the hyperglycemia of diabetes. Proliferation of SMCs treated with gemfibrozil was estimated by cell counting (Coulter Counter) and [3H]thymidine incorporation, migration in a scrape-wound assay, proteoglycan (PG) biosynthesis and glycosaminoglycan (GAG) synthesis on xyloside by [35S]sulfate labeling and sizing by sodium dodecyl sulphide-polyacrylamide gel electrophoresis (SDS-PAGE). Gemfibrozil (100 micromol/l) did not affect migration in low or high glucose media. Gemfibrozil caused concentration-dependent inhibition of proliferation in low glucose media (24% inhibition at 100 micromol/l, P<0.01) and inhibited the re-initiation of DNA synthesis by 33.3% (100 micromol/l, P<0.05) in low glucose and 31.4% (100 micromol/l, P<0.001) in high glucose conditions. In low and high glucose media, gemfibrozil (100 micromol/l) reduced total PG production in the presence of TGF-beta 1, which was associated with a decrease in the apparent size of PGs. Gemfibrozil and another PPAR-alpha ligand, WY-14643, significantly inhibited basal and TGF-beta1 stimulated GAG synthesis. We conclude that some SMCs properties associated with atherogenesis are favorably affected by gemfibrozil. Hence, direct vascular actions of gemfibrozil observed in this study may contribute to the reduction in cardiovascular disease observed in clinical studies with gemfibrozil.

The angiogenic factor cysteine-rich 61 (CYR61, CCN1) supports vascular smooth muscle cell adhesion and stimulates chemotaxis through integrin alpha(6)beta(1) and cell surface heparan sulfate proteoglycans

Cysteine-rich 61 (CYR61, CCN1) is a heparin-binding, extracellular, matrix-associated protein of the cysteine-rich 61/nephroblastoma family, which also includes connective tissue growth factor, nephroblastoma overexpressed, Wnt-induced secreted protein-1 (WISP-1), WISP-2, and WISP-3. CYR61 induces angiogenesis in vivo and supports cell adhesion, promotes cell migration, and enhances growth factor-stimulated mitogenesis in fibroblasts and endothelial cells. Although the expression of CYR61 has been observed in arterial walls, its function in vascular smooth muscle cells (VSMCs) has not been examined to date. Here we show that purified CYR61 supports VSMC adhesion in a dose-dependent, saturable manner through integrin alpha(6)beta(1) with an absolute requirement of cell surface heparan sulfate proteoglycans. In addition, CYR61 induces VSMC chemotaxis, but not chemokinesis, through integrin alpha(6)beta(1) and heparan sulfate proteoglycans. Heparin-binding defective CYR61 mutants are unable to support VSMC adhesion but can still induce chemotaxis at a reduced level. Following balloon angioplasty in rat carotid artery, CYR61 protein level is elevated in the media and neointima of the injured vessel by d 4 post angioplasty, peaks from d 7 to 14, and remains high for at least 28 d. These data demonstrate the activities of CYR61 in VSMCs, identify the receptors that mediate its functions, and show that CYR61 is synthesized in arterial smooth muscle walls during proliferative restenosis. Together, these results implicate CYR61 as a novel factor that modulates the responses of VSMCs to vascular injury.

Changes of the uterine proteoglycan distribution at term pregnancy and during labour

OBJECTIVE

To characterise uterine proteoglycans and changes therein during pregnancy and labour.

STUDY DESIGN

Uterine samples were collected from 6 non-pregnant, 10 term-pregnant and from 10 women in active labour. The proteoglycans were extracted by 4M guanidine hydrochloride and precipitated with Alcian Blue. They were separated by electrophoresis and identified by Western blotting.

RESULTS

Decorin was the dominating proteoglycan and smaller amounts of biglycan was found. A considerable amount of heparan sulphate proteoglycans was also detected. Decorin and biglycan decreased by 40% until term. The amount of heparan sulphate proteoglycans increased by 46% during active labour.

CONCLUSION

Our data indicate that a considerable remodelling of the uterine connective tissue occurs during pregnancy and labour. The decrease of decorin and biglycan and the increase of heparan sulphate proteoglycans may be important for normal myometrial contractions during labour.

Membrane-type matrix metalloproteinase-1 and -3 activity in primate smooth muscle cells

Membrane-type matrix metalloproteinases-1 and -3 (MT1- and MT3-MMPs) are expressed by activated smooth muscle cells (SMCs) both in vitro and in vivo (19). To define their functions in SMCs, we transduced MT1- and MT3-MMP cDNAs into baboon SMCs by using adenoviral vectors. Overexpression of MT1-MMP increased the conversion of proMMP-2 to the intermediate and active forms. In contrast, in MT3-MMP-overexpressing cells, MMP-2 was activated partially. Immunoblot analyses revealed that MT1-MMP protein was present in the SMCs and accumulated in the presence of the synthetic MMP inhibitor, BB94, or tissue inhibitor of metalloproteinase-2 (TIMP-2). However, MT3-MMP protein was detectable only when BB94, but not TIMP-2, was present. Zymographic analyses showed that MT3-MMP had much stronger casein- and gelatin-degrading activities than did MT1-MMP. Furthermore, when MT3-MMP and MT1-MMP were coexpressed, MT1-MMP degradation was enhanced; this result supports the possibility that MT3-MMP can degrade MT1-MMP. SMCs overexpressing either MT1- or MT3-MMP exhibited altered morphology, without changing their proliferation. This alteration was prevented by BB94 addition. The cells, which underwent this change, showed reduced adhesion to both collagen and fibronectin and increased migration in a Boyden chamber. The present study demonstrates that MT1- and MT3-MMPs have different enzymatic activities but may nevertheless affect SMC function in the same way.

Antibodies against a putative heparin receptor slow cell proliferation and decrease MAPK activation in vascular smooth muscle cells

Heparin has long been known to slow the growth of vascular smooth muscle cells. However, the mechanism(s) by which heparin acts has yet to be resolved. The identification of a putative heparin receptor in endothelial cells with antibodies that blocked heparin binding to the cells provided the means to further examine the possible involvement of a heparin receptor in smooth muscle cell responses to heparin. Immunoprecipitation of a smooth muscle cell protein with the anti-heparin receptor antibodies provided evidence that the protein was present in smooth muscle cells. Experiments with the anti-heparin receptor antibodies indicate that the antibodies can mimic heparin in decreasing PDGF induced thymidine and BrdU incorporation. The anti-heparin receptor antibodies were also found to decrease MAPK activity levels after activation similarly to heparin. These results support the identification of a heparin receptor and its role in heparin effects on vascular smooth muscle cell growth.

Apolipoprotein E receptor binding versus heparan sulfate proteoglycan binding in its regulation of smooth muscle cell migration and proliferation

This study showed that synthetic peptides containing either a single copy or tandem repeat of the receptor binding domain sequence of apolipoprotein (apo) E, or a peptide containing its C-terminal heparin binding domain, apoE-(211-243), were all effective inhibitors of platelet-derived growth factor (PDGF)-stimulated smooth muscle cell proliferation. In contrast, only the peptide containing a tandem repeating unit of the receptor binding domain sequence of apoE, apoE-(141-155)(2), was capable of inhibiting PDGF-directed smooth muscle cell migration. Peptide containing only a single unit of this sequence, apoE-(141-155), or the apoE-(211-243) peptide were ineffective in inhibiting PDGF-directed smooth muscle cell migration. Additional experiments showed that reductively methylated apoE, which is incapable of receptor binding yet retains its heparin binding capability, was equally effective as apoE in inhibiting PDGF-stimulated smooth muscle cell proliferation. However, reductively methylated apoE was unable to inhibit smooth muscle cell migration toward PDGF. Additionally, the receptor binding domain-specific apoE antibody 1D7 also mitigated the anti-migratory properties of apoE on smooth muscle cells. Finally, pretreatment of cells with heparinase failed to abolish apoE inhibition of smooth muscle cell migration. Taken together, these data documented that apoE inhibition of PDGF-stimulated smooth muscle cell proliferation is mediated by its binding to heparan sulfate proteoglycans, while its inhibition of cell migration is mediated through apoE binding to cell surface receptors.

Involvement of platelet-derived growth factor in disease: development of specific antagonists

Platelet-derived growth factor (PDGF) is a family of dimeric isoforms that stimulates, e.g., growth, chemotaxis and cell shape changes of various connective tissue cell types and certain other cells. The cellular effects of PDGF isoforms are exerted through binding to two structurally related tyrosine kinase receptors. Ligand binding induces receptor dimerization and autophosphorylation. This enables a number of SH2 domain containing signal transduction molecules to bind to the receptors, thereby initiating various signaling pathways. PDGF isoforms have important roles during the embryonic development, particularly in the formation of connective tissue in various organs. In the adult, PDGF stimulates wound healing. Overactivity of PDGF has been implicated in certain disorders, including fibrotic conditions, atherosclerosis, and malignancies. Different kinds of PDGF antagonists are currently being developed and evaluated in different animal disease models, as well as in clinical trials.

Ryudocan expression by luteinized granulosa cells is associated with the process of follicle atresia

OBJECTIVE

To evaluate the presence of ryudocan in follicular fluid (FF) and its possible correlation with FF E(2) and P, and to study the levels of ryudocan in granulosa-lutein cells stimulated with hCG.

DESIGN

Controlled clinical study and in vitro experiment.

SETTING

University teaching hospital.

PATIENT(S)

One hundred seven patients undergoing IVF.

INTERVENTION(S)

The FF and granulosa-lutein cells were aspirated from follicles 34 hours after an ovulatory gonadotropin bolus.

MAIN OUTCOME MEASURE(S)

FF ryudocan, E(2), and P levels as well as hCG-mediated induction of ryudocan.

RESULT(S)

Ryudocan was abundant in the FF; the concentration of ryudocan in human FF was estimated to be 305.5 +/- 200.8 ng/mL (mean +/- SD). Atretic follicles had higher concentrations of ryudocan (559.1 +/- 156.5 ng/mL). FF ryudocan levels were inversely correlated with FF E(2) (r = -0.5023) and P concentrations (r = -0.4459). A detectable amount of ryudocan was found in pooled granulosa-lutein cells. Ryudocan production was augmented by surge levels of hCG.

CONCLUSION(S)

Ryudocan is expressed in luteinized granulosa cells in vitro. The higher concentrations of ryudocan in FF of atretic follicles suggest an involvement of ryudocan in the process of atresia.

The mechanisms of coronary restenosis: insights from experimental models

Since its introduction into clinical practice, more than 20 years ago, percutaneous transluminal coronary angioplasty (PTCA) has proven to be an effective, minimally invasive alternative to coronary artery bypass grafting (CABG). During this time there have been great improvements in the design of balloon catheters, operative procedures and adjuvant drug therapy, and this has resulted in low rates of primary failure and short-term complications. However, the potential benefits of angioplasty are diminished by the high rate of recurrent disease. Up to 40% of patients undergoing angioplasty develop clinically significant restenosis within a year of the procedure. Although the deployment of endovascular stents at the time of angioplasty improves the short-term outcome, 'in-stent' stenosis remains an enduring problem. In order to gain an insight into the mechanisms of restenosis, several experimental models of angioplasty have been developed. These have been used together with the tools provided by recent advances in molecular biology and catheter design to investigate restenosis in detail. It is now possible to deliver highly specific molecular antagonists, such as antisense gene sequences, to the site of injury. The knowledge provided by these studies may ultimately lead to novel forms of intervention. The present review is a synopsis of our current understanding of the pathological mechanisms of restenosis.

Perlecan mediates the antiproliferative effect of apolipoprotein E on smooth muscle cells. An underlying mechanism for the modulation of smooth muscle cell growth?

Apolipoprotein E (apoE) is known to inhibit cell proliferation; however, the mechanism of this inhibition is not clear. We recently showed that apoE stimulates endothelial production of heparan sulfate (HS) enriched in heparin-like sequences. Because heparin and HS are potent inhibitors of smooth muscle cell (SMC) proliferation, in this study we determined apoE effects on SMC HS production and cell growth. In confluent SMCs, apoE (10 microg/ml) increased (35)SO(4) incorporation into PG in media by 25-30%. The increase in the medium was exclusively due to an increase in HSPGs (2.2-fold), and apoE did not alter chondroitin and dermatan sulfate proteoglycans. In proliferating SMCs, apoE inhibited [(3)H]thymidine incorporation into DNA by 50%; however, despite decreasing cell number, apoE increased the ratio of (35)SO(4) to [(3)H]thymidine from 2 to 3.6, suggesting increased HS per cell. Purified HSPGs from apoE-stimulated cells inhibited cell proliferation in the absence of apoE. ApoE did not inhibit proliferation of endothelial cells, which are resistant to heparin inhibition. Analysis of the conditioned medium from apoE-stimulated cells revealed that the HSPG increase was in perlecan and that apoE also stimulated perlecan mRNA expression by >2-fold. The ability of apoE isoforms to inhibit cell proliferation correlated with their ability to stimulate perlecan expression. An anti-perlecan antibody completely abrogated the antiproliferative effect of apoE. Thus, these data show that perlecan is a potent inhibitor of SMC proliferation and is required to mediate the antiproliferative effect of apoE. Because other growth modulators also regulate perlecan expression, this may be a key pathway in the regulation of SMC growth.