Suppression by heparin of smooth muscle cell proliferation in injured arteries

Development of heparinized and hepatocyte growth factor-coated acellular scaffolds using porcine carotid arteries

Tissue-engineered blood vessel substitutes have been developed due to the lack of suitable small-diameter vascular grafts. Xenogeneic extracellular matrix (ECM) scaffolds have the potential to provide an ideal source for off-the-shelf vascular grafts. In this study, porcine carotid arteries were used to develop ECM scaffolds by decellularization and coating with heparin and hepatocyte growth factor (HGF). After decellularization, cellular and nucleic materials were successfully removed with preservation of the main compositions (collagen, elastin, and basement membrane) of the native ECM. The ultimate tensile strength, suture strength, and burst pressure were significantly increased after cross-linking. Pore size distribution analysis revealed a porous structure within ECM scaffolds with a high distribution of pores larger than 10 μm. Heparinized scaffolds exhibited sustained release of heparin in vitro and showed potent anticoagulant activity by prolonging activated partial thromboplastin time. The scaffolds showed an enhanced HGF binding capacity as well as a constant release of HGF as a result of heparin modification. When implanted subcutaneously in rats, the modified scaffolds revealed good biocompatibility with enzyme degradation resistance, mitigated immune response, and anti-calcification. In conclusion, heparinized and HGF-coated acellular porcine carotid arteries may be a promising biological scaffold for tissue-engineered vascular grafts.

Incorporating Anticoagulant and Antiplatelet Dual Functional Groups into Thermosetting Polymer Chain for Enhancing Antithrombogenicity

In clinical practice, high-effective antithrombosis remains a challenge for blood-contacting medical devices. Inspired by the enhanced antithrombogenicity of anticoagulant and antiplatelet combination therapy, a strategy is proposed to synthesize dual-pathway antithrombotic polymers by incorporating anticoagulant and antiplatelet dual functional groups into a single thermosetting polymer chain. The synthesized polymer shows increased antithrombogenicity in vitro, with prolonged activated partial thromboplastin time (APTT) and decreased platelet adhesion. Additionally, it downregulates the expression of coagulation- and inflammation-related factors in rabbit plasma after ex vivo arteriovenous shunt assay and maintains patency of small vascular grafts for at least 6 months without thrombosis on the luminal surface after in vivo replacement of rabbit carotid artery. This work provides a new approach to producing novel antithrombotic polymers for blood-contacting medical devices.

Monocyte adhesive hyaluronan matrix induced by hyperglycemia in diabetic lung injuries

Infiltrated pre-inflammatory monocytes and macrophages have important roles in the induction of diabetic lung injuries, but the mechanism mediating their infiltration is still unclear. Here, we showed that airway smooth muscle cells (SMCs) activated monocyte adhesion in response to hyperglycemic glucose (25.6 mM) by significantly increasing hyaluronan (HA) in the cell matrix, with concurrent 2- to 4-fold increases in adhesion of U937 monocytic-leukemic cells. The HA-based structures were attributed directly to the high-glucose and not to increased extracellular osmolality, and they required growth stimulation of SMCs by serum. Treatment of SMCs with heparin in high-glucose induces synthesis of a much larger HA matrix, consistent with our observations in the glomerular SMCs. Further, we observed increases in tumor necrosis factor-stimulated gene-6 (TSG-6) expression in high-glucose and high-glucose plus heparin cultures, and the heavy chain (HC)-modified HA structures existed on the monocyte-adhesive cable structures in high-glucose and in high-glucose plus heparin-treated SMC cultures. Interestingly, these HC-modified HA structures were unevenly distributed along the HA cables. Further, the in vitro assay with recombinant human TSG-6 and the HA14 oligo showed that heparin has no inhibitory activity on the TSG-6-induced HC-transfer to HA, consistent with the results from SMC cultures. These results support the hypothesis that hyperglycemia in airway smooth muscle induces the synthesis of a HA matrix that recruits inflammatory cells and establishes a chronic inflammatory process and fibrosis that lead to diabetic lung injuries.

Heparin and calreticulin interact on the surface of early G0/G1 dividing rat mesangial cells to regulate hyperglycemic glucose-induced responses

Heparin can block pathological responses associated with diabetic nephropathy in animal models and human patients. Our previous studies showed that the interaction of heparin on the surface of rat mesangial cells (RMCs) entering G1 of cell division in hyperglycemic glucose: 1) blocked glucose uptake by glucose transporter 4; 2) inhibited cytosolic uridine diphosphate-glucose elevation that would occur within 6 h from G0/G1; and 3) prevented subsequent activation of hyaluronan synthesis in intracellular compartments and subsequent inflammatory responses. However, specific proteins that interact with heparin are unresolved. Here, we showed by live cell imaging that fluorescent heparin was rapidly internalized into the cytoplasm and then into the endoplasmic reticulum, Golgi, and nuclei compartments. Biotinylated-heparin was applied onto the surface of growth arrested G0/G1 RMCs in order to extract heparin-binding protein(s). SDS-PAGE gels showed two bands at ∼70 kDa in the extract that were absent when unlabeled heparin was used to compete. Trypsin digests of the bands were analyzed by MS and identified as calreticulin and prelamin A/C. Immunostaining with their antibodies identified the presence of calreticulin on the G0/G1 RMC cell surface. Previous studies have shown that calreticulin can be on the cell surface and can interact with the LDL receptor-related protein, which has been implicated in glucose transport by interaction with glucose transporter 4. Thus, cell surface calreticulin can act as a heparin receptor through a mechanism involving LRP1, which prevents the intracellular responses in high glucose and reprograms the cells to synthesize an extracellular hyaluronan matrix after division.

Comparative Evaluation on Impacts of Fibronectin, Heparin-Chitosan, and Albumin Coating of Bacterial Nanocellulose Small-Diameter Vascular Grafts on Endothelialization In Vitro

In this study, we contrast the impacts of surface coating bacterial nanocellulose small-diameter vascular grafts (BNC-SDVGs) with human albumin, fibronectin, or heparin–chitosan upon endothelialization with human saphenous vein endothelial cells (VEC) or endothelial progenitor cells (EPC) in vitro. In one scenario, coated grafts were cut into 2D circular patches for static colonization of a defined inner surface area; in another scenario, they were mounted on a customized bioreactor and subsequently perfused for cell seeding. We evaluated the colonization by emerging metabolic activity and the preservation of endothelial functionality by water soluble tetrazolium salts (WST-1), acetylated low-density lipoprotein (AcLDL) uptake assays, and immune fluorescence staining. Uncoated BNC scaffolds served as controls. The fibronectin coating significantly promoted adhesion and growth of VECs and EPCs, while albumin only promoted adhesion of VECs, but here, the cells were functionally impaired as indicated by missing AcLDL uptake. The heparin–chitosan coating led to significantly improved adhesion of EPCs, but not VECs. In summary, both fibronectin and heparin–chitosan coatings could beneficially impact the endothelialization of BNC-SDVGs and might therefore represent promising approaches to help improve the longevity and reduce the thrombogenicity of BNC-SDVGs in the future.

Heparin-Eluting Tissue-Engineered Bioabsorbable Vascular Grafts

The creation of small-diameter tissue-engineered vascular grafts using biodegradable materials has the potential to change the quality of cardiovascular surgery in the future. The implantation of these tissue-engineered arterial grafts has yet to reach clinical application. One of the reasons for this is thrombus occlusion of the graft in the acute phase. In this paper, we first describe the causes of accelerated thrombus formation and discuss the drugs that are thought to inhibit thrombus formation. We then review the latest research on methods to locally bind the anticoagulant heparin to biodegradable materials and methods to extend the duration of sustained heparin release. We also discuss the results of studies using large animal models and the challenges that need to be overcome for future clinical applications.

The birth, decline, and contemporary re-emergence of endovascular brachytherapy for prevention of in-stent restenosis

Despite the advent of drug-eluting stents and dual antiplatelet therapy in the interventional management of cardiovascular disease, restenosis rates remain high with significant sequelae. Endovascular brachytherapy-popular in the 1990s and early 2000s-has recently resurfaced as a cost-effective treatment option. In this work, we outline the history of endovascular brachytherapy starting with its earliest promise in the 1990s. We discuss the development of drug-eluting stents and dual antiplatelet strategies and their impact on the perceived benefit of endovascular brachytherapy. For the contemporary era, we propose novel roles for endovascular brachytherapy in complex coronary artery disease and in high-risk patients managed with drug-eluting stents. We discuss the impetus for reducing the requirement and duration of dual antiplatelet therapy using endovascular brachytherapy. We also review innovative opportunities for endovascular brachytherapy after bare-metal stent placement in both coronary and noncoronary territories and offer economic arguments in favor of endovascular brachytherapy. Trials of endovascular brachytherapy in these regimes are merited.

The effect of Substance P/Heparin conjugated PLCL polymer coating of bioinert ePTFE vascular grafts on the recruitment of both ECs and SMCs for accelerated regeneration

Artificial vascular grafts consisting of ePTFE have been mainly used in clinics for the treatment of cardiovascular disease. However, artificial grafts can become clogged after a long time due to thrombosis, as graft maturation by endothelialization is limited. The strategy introduced in this study is to induce graft remodeling through interaction between the bioinert graft and the body. The Substance P (SP) and heparin were covalently conjugated with PLCL, an elastic biocompatible copolymer and the Substance P-conjugated PLCL (SP-PLCL) and/or heparin-conjugated PLCL (Hep-PLCL) were vacuum-coated onto ePTFE vascular grafts. To assess the effectiveness of the coating, coated samples were evaluated by implanting them subcutaneously into SD-Rats. Coatings allow grafts to be remodeled by creating a microenvironment where cells can grow by infiltrating into the grafts while also greatly enhancing angiogenesis. In particular, a double coating of Hep-PLCL and SP-PLCL (Hep/SP-PLCL) at four weeks showed markedly improved vascular remodeling through the recruitment of mesenchymal stem cells (MSCs), vascular cells (ECs, SMCs) and M2 macrophages. Based on these results, it is expected that when the Hep/SP-PLCL-coated ePTFE vascular grafts are implanted in situ, long-term patency will be assured due to the appropriate formation of an endothelial layer and smooth muscle cells in the grafts like native vessels.

Poly(ε-caprolactone)/keratin/heparin/VEGF biocomposite mats for vascular tissue engineering

Vascular endothelial growth factor (VEGF) is an effective growth and angiogenic cytokine, which stimulates proliferation and survival of endothelial cells, and promotes angiogenesis and vascular permeability. Binding VEGF with heparin could protect it from rapid degradation, subsequently allowing it to be controlled release. Primarily, poly(ε-caprolactone) (PCL) and keratin were coelectrospun, followed by conjugating with heparin and subsequently binding VEGF. The loaded heparin and VEGF on these mats were quantified, respectively. The surface characteristics of mats were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The VEGF delivery results indicated these mats could sustainably release VEGF for 2 weeks. Cell viability assays suggested these mats were valid to accelerate human umbilical vein endothelial cells (HUVECs) proliferation, while inhibit human umbilical arterial smooth muscle cells (HUASMCs) growth under the combined actions of VEGF and heparin. The results tested by blood clotting times (APTT, PT, and TT), hemolysis, and platelet adhesion indicated the mats were blood compatible. To sum up, these biocomposite mats are ideal scaffolds for vascular tissue engineering.

Macroporous nanofibrous vascular scaffold with improved biodegradability and smooth muscle cells infiltration prepared by dual phase separation technique

INTRODUCTION

The fast degradation of vascular graft and the infiltration of smooth muscle cells (SMCs) into the vascular graft are considered to be critical for the regeneration of functional neo-vessels. In our previous study, a novel dual phase separation technique was developed to one-pot prepare macroporous nanofibrous poly(L-lactic acid) (PLLA)/poly(ε-caprolactone) (PCL) vascular scaffold by phase separating the immiscible polymer blend. However, the slow degradation of PLLA/PCL limited cell infiltration. Herein, we hypothesized that poly(lactic-co-glycolic acid) (PLGA) would be miscible with PLLA but immiscible with PCL. Then, PLGA can be introduced into the PLLA/PCL blend to fabricate macroporous nanofibrous scaffold with improved biodegradability by using dual phase separation technique.

MATERIALS AND METHODS

The miscibility of PLGA with PLLA and PCL was evaluated. Then, the PLLA/PLGA/PCL scaffold was prepared by dual phase separation technique. The prepared scaffolds were characterized in terms of the morphology, in vitro degradation, mechanical properties, and cells' infiltration and viability for human vascular SMCs (HVSMCs). Finally, platelet-derived growth factor-BB (PDGF-BB) was immobilized on the scaffold and its effect on the bioactivity of HVSMCs was studied.

RESULTS

PLGA is miscible with PLLA but immiscible with PCL as hypothesized. The addition of PLGA enlarged the pore size and improved the biodegradability of composite scaffold. Notably, PLLA/PLGA/PCL scaffold with the blend ratio of 30:40:30 possessed improved pore interconnectivity for cells' infiltration and enough mechanical properties. Moreover, HVSMCs could grow and infiltrate into this scaffold, and surface modification with PDGF-BB on the nanofibrous scaffold enhanced HVSMCs migration and proliferation.

CONCLUSION

This study provides a strategy to expand dual phase separation technique into utilizing ternary even multinary polymer blend to fabricate macroporous nanofibrous scaffold with improved physicochemical properties. The prepared PLLA/PLGA/PCL scaffold would be promising for the regeneration of functional tunica media in vascular tissue engineering.

A role for proteoglycans in vascular disease

The content of proteoglycans (PGs) is low in the extracellular matrix (ECM) of vascular tissue, but increases dramatically in all phases of vascular disease. Early studies demonstrated that glycosaminoglycans (GAGs) including chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS) and heparan sulfate (HS) accumulate in vascular lesions in both humans and in animal models in areas of the vasculature that are susceptible to disease initiation (such as at branch points) and are frequently coincident with lipid deposits. Later studies showed the GAGs were covalently attached to specific types of core proteins that accumulate in vascular lesions. These molecules include versican (CSPG), biglycan and decorin (DS/CSPGs), lumican and fibromodulin (KSPGs) and perlecan (HSPG), although other types of PGs are present, but in lesser quantities. While the overall molecular design of these macromolecules is similar, there is tremendous structural diversity among the different PG families creating multiple forms that have selective roles in critical events that form the basis of vascular disease. PGs interact with a variety of different molecules involved in disease pathogenesis. For example, PGs bind and trap serum components that accumulate in vascular lesions such as lipoproteins, amyloid, calcium, and clotting factors. PGs interact with other ECM components and regulate, in part, ECM assembly and turnover. PGs interact with cells within the lesion and alter the phenotypes of both resident cells and cells that invade the lesion from the circulation. A number of therapeutic strategies have been developed to target specific PGs involved in key pathways that promote vascular disease. This review will provide a historical perspective of this field of research and then highlight some of the evidence that defines the involvement of PGs and their roles in the pathogenesis of vascular disease.

Heparinized PCL/keratin mats for vascular tissue engineering scaffold with potential of catalytic nitric oxide generation

Heparins are capable of improving blood compatibility, enhancing HUVEC viability, while inhibiting HUASMC proliferation. Combination of biodegradable poly(ε-caprolactone) (PCL) with keratin and heparins would provide an anticoagulant and endothelialization supporting environment for vascular tissue engineering. Herein, PCL and keratin were first coelectrospun and then covalently conjugated with heparins. The resulting mats were surface-characterized by ATR-FTIR, SEM, WCA, and XPS. Cell viability data showed that the heparinized PCL/keratin mats could motivate the adhesion and growth of HUVEC, while inhibit HUASMC proliferation. In addition, these mats could prolong blood clotting time and reduce platelet adhesion as well as no erythrolysis. Interestingly, these mats could catalyze the NO donor in blood to release NO, which could enhance endothelial cell growth, while decrease smooth muscle cell proliferation and platelet adhesion. In summary, the heparinized mats would be a good candidate as a scaffold for vascular tissue engineering. This study is novel in that we prepared a type of heparinized tissue scaffold that could catalyze the NO donor to release NO to regulate endothelialization without angiogenesis and thrombus formation.

Catechol/polyethyleneimine conversion coating with enhanced corrosion protection of magnesium alloys: potential applications for vascular implants

A catechol/polyethyleneimine conversion coating on a MgZnMn alloy possessed good corrosion resistance. Heparin was further grafted on it and this showed the potential for surface modification of magnesium-based vascular implants.

Anticoagulation Therapy in Patients with Chronic Kidney Disease

Patients with chronic kidney disease (CKD) are at increased risk for both thrombotic events and bleeding. The early stages of CKD are mainly associated with prothrombotic tendency, whereas in its more advanced stages, beside the prothrombotic state, platelets can become dysfunctional due to uremic-related toxin exposure leading to an increased bleeding tendency. Patients with CKD usually require anticoagulation therapy for treatment or prevention of thromboembolic diseases. However, this benefit could easily be offset by the risk of anticoagulant-induced bleeding. Treatment of patients with CKD should be based on evidence from randomized clinical trials, but usually CKD patients are excluded from these trials. In the past, unfractionated heparins were the anticoagulant of choice for patients with CKD because of its independence of kidney elimination. However, currently low-molecular-weight heparins have largely replaced the use of unfractionated heparins owing to fewer incidences of heparin-induced thrombocytopenia and bleeding. We undertook this review in order to explain the practical considerations for the management of anticoagulation in these high risk population.

Surface modification of endovascular stents with rosuvastatin and heparin-loaded biodegradable nanofibers by electrospinning

This study describes the development of drug-loaded nanofibrous scaffolds as a nanocoating for endovascular stents for the local and sustained delivery of rosuvastatin (Ros) and heparin (Hep) to injured artery walls after endovascular procedures via the electrospinning process.

PURPOSE

The proposed hybrid covered stents can promote re-endothelialization; improve endothelial function; reduce inflammatory reaction; inhibit neointimal hyperplasia of the injured artery wall, due to well-known pleiotropic actions of Ros; and prevent adverse events such as in-stent restenosis (ISR) and stent thrombosis (ST), through the antithrombotic action of Hep.

METHODS

Biodegradable nanofibers were prepared by dissolving cellulose acetate (AC) and Ros in N,N-dimethylacetamide (DMAc) and acetone-based solvents. The polymeric solution was electrospun (e-spun) into drug-loaded AC nanofibers onto three different commercially available stents (Co-Cr stent, Ni-Ti stent, and stainless steel stent), resulting in nonwoven matrices of submicron-sized fibers. Accordingly, Hep solution was further used for fibrous coating onto the engineered Ros-loaded stent. The functional encapsulation of Ros and Hep drugs into polymeric scaffolds further underwent physicochemical analysis. Morphological characterization took place via scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses, while scaffolds' wettability properties were obtained by contact angle (CA) measurements.

RESULTS

The morphology of the drug-loaded AC nanofibers was smooth, with an average diameter of 200-800 nm, and after CA measurement, we concluded to the superhydrophobic nature of the engineered scaffolds. In vitro release rates of the pharmaceutical drugs were determined using a high-performance liquid chromatography assay, which showed that after the initial burst, drug release was controlled slowly by the degradation of the polymeric materials.

CONCLUSION

These results imply that AC nanofibers encapsulated with Ros and Hep drugs have great potential in the development of endovascular grafts with anti-thrombogenic properties that can accelerate the re-endothelialization, reduce the neointimal hyperplasia and inflammatory reaction, and improve the endothelial function.

Vascular scaffolds with enhanced antioxidant activity inhibit graft calcification

There is a need for off-the-shelf, small-diameter vascular grafts that are safe and exhibit high long-term patency. Decellularized tissues can potentially be used as vascular grafts; however, thrombogenic and unpredictable remodeling properties such as intimal hyperplasia and calcification are concerns that hinder their clinical use. The objective of this study was to investigate the long-term function and remodeling of extracellular matrix (ECM)-based vascular grafts composited with antioxidant poly(1, 8-octamethylene-citrate-co-cysteine) (POCC) with or without immobilized heparin. Rat aortas were decellularized to create the following vascular grafts: 1) ECM hybridized with POCC (Poly-ECM), 2) Poly-ECM subsequently functionalized with heparin (Poly-ECM-Hep), and 3) non-modified vascular ECM. Grafts were evaluated as interposition grafts in the abdominal aorta of adult rats at three months. All grafts displayed antioxidant activity, were patent, and exhibited minimal intramural cell infiltration with varying degrees of calcification. Areas of calcification co-localized with osteochondrogenic differentiation of vascular smooth muscle cells, lipid peroxidation, oxidized DNA damage, and cell apoptosis, suggesting an important role for oxidative stress in the calcification of grafts. The extent of calcification within grafts was inversely proportional to their antioxidant activity: Poly-ECM-Hep > ECM > Poly-ECM. The incorporation of antioxidants into vascular grafts may be a viable strategy to inhibit degenerative changes.

Erythrocyte Efferocytosis by the Arterial Wall Promotes Oxidation in Early-Stage Atheroma in Humans

Background

Since red blood cells (RBCs) are the predominant cellular blood component interacting with the arterial wall, we explored the role of RBCs efferocytosis by vascular smooth muscle cells (vSMCs) in the initiation of human atheroma.

Methods and results

The comparison of human healthy aortas with aortic fatty streaks or fibroatheromas revealed that RBC angiophagy is implicated from the earliest stages of atherogenesis, as documented by the concomitant detection of redox-active iron, hemoglobin, glycophorin A, and ceroids. RBCs infiltration in the arterial wall was associated with local lipid and protein oxidation, as well as vascular response (expression of heme oxygenase-1 and of genes related to iron metabolism as well as those encoding for phagocytosis). These effects were recapitulated in vitro when vSMCs were co-cultured with phosphatidyl-exposing senescent (s) RBCs but not with fresh RBCs. VSMCs engulfing sRBC increased their intracellular iron content, accumulated hemoglobin, lipids, and activated their phagolysosomes. Strikingly, injections of sRBCs into rats promoted iron accumulation in the aortic wall. In rabbits, hypercholesterolemia increased circulating senescent RBCs and induced the subendothelial accumulation of iron-rich phagocytic foam cells. RBCs bring cholesterol and iron/heme into the vascular wall and interact with vSMCs that phagocytize them.

Conclusion

This study presents a previously unforeseen mechanism of plaque formation that implicates intimal RBC infiltration as one of the initial triggers for foam cell formation and intimal oxidation. Pathogenic effects exerted by several metabolic and hemodynamic factors may rely on their effect on RBC biology, thereby impacting how RBCs interact with the vascular wall.

Calcium-Independent Activation of an Allosteric Network in Langerin by Heparin Oligosaccharides

The C-type lectin receptor Langerin is a glycan-binding protein that serves as an uptake receptor on Langerhans cells and is essential for the formation of Birbeck granules. Whereas most Langerin ligands are recognized by a canonical Ca²⁺ -dependent binding site, heparins have been proposed to make additional contacts to a secondary, Ca²⁺ -independent site. Glycan array screening and biomolecular NMR spectroscopy were employed to investigate the molecular mechanism of these interactions. We observed that binding of heparin hexasaccharides to a secondary site did not require the presence of Ca²⁺ and activated a previously identified intradomain allosteric network of Langerin (thus far only associated with Ca²⁺ affinity and release). We propose a communication hub between these two binding sites, which sheds new light on modulatory functions of Langerin-heparin interactions.

Pharmacology of Heparin and Related Drugs

Heparin has been recognized as a valuable anticoagulant and antithrombotic for several decades and is still widely used in clinical practice for a variety of indications. The anticoagulant activity of heparin is mainly attributable to the action of a specific pentasaccharide sequence that acts in concert with antithrombin, a plasma coagulation factor inhibitor. This observation has led to the development of synthetic heparin mimetics for clinical use. However, it is increasingly recognized that heparin has many other pharmacological properties, including but not limited to antiviral, anti-inflammatory, and antimetastatic actions. Many of these activities are independent of its anticoagulant activity, although the mechanisms of these other activities are currently less well defined. Nonetheless, heparin is being exploited for clinical uses beyond anticoagulation and developed for a wide range of clinical disorders. This article provides a "state of the art" review of our current understanding of the pharmacology of heparin and related drugs and an overview of the status of development of such drugs.

Functional behavior and gene expression of magnetic nanoparticle-loaded primary endothelial cells for targeting vascular stents

AIM

To assess functional competence and gene expression of magnetic nanoparticle (MNP)-loaded primary endothelial cells (ECs) as potential cell-based therapy vectors.

MATERIALS & METHODS

A quantitative tube formation, nitric oxide and adhesion assays were conducted to assess functional potency of the MNP-loaded ECs. A quantitative real-time PCR was used to profile genes in both MNP-loaded at static conditions and in vitro targeted ECs.

RESULTS

Functional behavior of MNP-loaded and unloaded cells was comparable. MNPs induce expression of genes involved in EC growth and survival, while repress genes involved in coagulation.

CONCLUSION

MNPs do not adversely affect cellular function. Gene expression indicates that targeting MNP-loaded ECs to vascular stents may potentially stimulate re-endothelialization of an implant and attenuate neointimal hyperplasia.

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.

Transmembrane Protein 184A Is a Receptor Required for Vascular Smooth Muscle Cell Responses to Heparin

Vascular cell responses to exogenous heparin have been documented to include decreased vascular smooth muscle cell proliferation following decreased ERK pathway signaling. However, the molecular mechanism(s) by which heparin interacts with cells to induce those responses has remained unclear. Previously characterized monoclonal antibodies that block heparin binding to vascular cells have been found to mimic heparin effects. In this study, those antibodies were employed to isolate a heparin binding protein. MALDI mass spectrometry data provide evidence that the protein isolated is transmembrane protein 184A (TMEM184A). Commercial antibodies against three separate regions of the TMEM184A human protein were used to identify the TMEM184A protein in vascular smooth muscle cells and endothelial cells. A GFP-TMEM184A construct was employed to determine colocalization with heparin after endocytosis. Knockdown of TMEM184A eliminated the physiological responses to heparin, including effects on ERK pathway activity and BrdU incorporation. Isolated GFP-TMEM184A binds heparin, and overexpression results in additional heparin uptake. Together, these data support the identification of TMEM184A as a heparin receptor in vascular cells.

High mobility group box 1-immobilized nanofibrous scaffold enhances vascularization, osteogenesis and stem cell recruitment

An engineered, multi-functional HMGB1-immobilized scaffold is developed. HMGB1 is immobilized on the surface of electrospinning poly-l-lactide (PLLA)/polycaprolactone (PCL) nanofibers via heparin, which is used as a “trigger” signal to make the bone scaffold capable of enhancing vascularization, inducing osteogenesis and recruiting stem cells.

Perlecan Heparan Sulfate Is Required for the Inhibition of Smooth Muscle Cell Proliferation by All-trans-Retinoic Acid

Smooth muscle cell (SMC) proliferation is a key process in stabilization of atherosclerotic plaques, and during restenosis after interventions. A clearer understanding of SMC growth regulation is therefore needed to design specific anti-proliferative therapies. Retinoic acid has been shown to inhibit proliferation of SMCs both in vitro and in vivo and to affect the expression of extracellular matrix molecules. To explore the mechanisms behind the growth inhibitory activity of retinoic acid, we hypothesized that retinoids may induce the expression of perlecan, a large heparan sulfate proteoglycan with anti-proliferative properties. Perlecan expression and accumulation was induced in murine SMC cultures by all-trans-retinoic acid (AtRA). Moreover, the growth inhibitory effect of AtRA on wild-type cells was greatly diminished in SMCs from transgenic mice expressing heparan sulfate-deficient perlecan, indicating that the inhibition is perlecan heparan sulfate-dependent. In addition, AtRA influenced activation and phosphorylation of PTEN and Akt differently in wild-type and mutant SMCs, consistent with previous studies of perlecan-dependent SMC growth inhibition. We demonstrate that AtRA regulates perlecan expression in SMCs and that the inhibition of SMC proliferation by AtRA is, at least in part, secondary to an increased expression of perlecan and dependent upon its heparan sulfate-chains.

Prophylactic Low Molecular Weight Heparin Improving Perinatal Outcome in Non-thrombophilic Placental-Mediated Complications

OBJECTIVE

To study the role of low molecular weight heparin (LMWH) in perinatal outcome.

METHODS

A randomized, case control study was conducted at Safdarjang hospital, New Delhi. Patients were recruited from Sept. 2011 to May 2013 and were followed up till delivery. Thirty cases and controls were enrolled which comprised non-thrombophilic patients with previous history of preeclampsia, fetal growth restriction, abruption, and stillbirth (>20 weeks). Study group received daily single dose of LMWH depending upon the weight, subcutaneously; it was started before 15 weeks of gestation and continued up to 36 weeks. Nursery/NICU admission, APGAR score at 0 and 5 min, birth weight, gestational age at delivery, mode of delivery were observed among the interventional and control groups.

RESULT

There was substantial reduction (80 %) in nursery/NICU admission. The mean gestational age and birth weight of the cases were observed to be higher as compared to those of control (38.05 ± 2.02 vs. 37.58 ± 2.06 weeks and 2770 ± 400 vs. 2530 ± 0.533 g).

CONCLUSION

Prophylactic LMWH before 15 weeks of gestation improved the perinatal outcome in non-thrombophilic pregnant women.

Heparin responses in vascular smooth muscle cells involve cGMP-dependent protein kinase (PKG)

Published data provide strong evidence that heparin treatment of proliferating vascular smooth muscle cells results in decreased signaling through the ERK pathway and decreases in cell proliferation. In addition, these changes have been shown to be mimicked by antibodies that block heparin binding to the cell surface. Here, we provide evidence that the activity of protein kinase G is required for these heparin effects. Specifically, a chemical inhibitor of protein kinase G, Rp-8-pCPT-cGMS, eliminates heparin and anti-heparin receptor antibody effects on bromodeoxyuridine incorporation into growth factor-stimulated cells. In addition, protein kinase G inhibitors decrease heparin effects on ERK activity, phosphorylation of the transcription factor Elk-1, and heparin-induced MKP-1 synthesis. Although transient, the levels of cGMP increase in heparin treated cells. Finally, knock down of protein kinase G also significantly decreases heparin effects in growth factor-activated vascular smooth muscle cells. Together, these data indicate that heparin effects on vascular smooth muscle cell proliferation depend, at least in part, on signaling through protein kinase G.

Mussel-inspired one-step adherent coating rich in amine groups for covalent immobilization of heparin: hemocompatibility, growth behaviors of vascular cells, and tissue response

Heparin, an important polysaccharide, has been widely used for coatings of cardiovascular devices because of its multiple biological functions including anticoagulation and inhibition of intimal hyperplasia. In this study, surface heparinization of a commonly used 316L stainless steel (SS) was explored for preparation of a multifunctional vascular stent. Dip-coating of the stents in an aqueous solution of dopamine and hexamethylendiamine (HD) (PDAM/HD) was presented as a facile method to form an adhesive coating rich in primary amine groups, which was used for covalent heparin immobilization via active ester chemistry. A heparin grafting density of about 900 ng/cm(2) was achieved with this method. The retained bioactivity of the immobilized heparin was confirmed by a remarkable prolongation of the activated partial thromboplastin time (APTT) for about 15 s, suppression of platelet adhesion, and prevention of the denaturation of adsorbed fibrinogen. The Hep-PDAM/HD also presented a favorable microenvironment for selectively enhancing endothelial cell (EC) adhesion, proliferation, migration and release of nitric oxide (NO), and at the same time inhibiting smooth muscle cell (SMC) adhesion and proliferation. Upon subcutaneous implantation, the Hep-PDAM/HD exhibited mitigated tissue response, with thinner fibrous capsule and less granulation formation compared to the control 316L SS. This number of unique functions qualifies the heparinized coating as an attractive alternative for the design of a new generation of stents.

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.

Fabrication of highly interconnected porous silk fibroin scaffolds for potential use as vascular grafts

Silk fibroin (SF) scaffolds have been designed and fabricated for multiple organ engineering owing to SF's remarkable mechanical property, excellent biocompatibility and biodegradability, as well as its low immunogenicity. In this study, an easy-to-adopt and mild approach based on a modified freeze-drying method was developed to fabricate a highly interconnected porous SF scaffold. The physical properties of the SF scaffold, including pore morphology, pore size, porosity and compressive modulus, could be adjusted by the amount of ethanol added, the freezing temperature and the concentration of SF. Fourier transform infrared spectroscopy illustrated that treatment of the lyophilized scaffolds with 90% methanol led to a structure transition of SF from silk I (random coil) to silk II (beta-sheet), which stabilized the SF scaffolds in water. We also incorporated heparin during fabrication to obtain a heparin-loaded scaffold which possessed excellent anticoagulant property. The heparin that was incorporated into the SF scaffolds could be released in a sustain manner for approximately 7days, inhibiting the proliferation of human smooth muscle cells within the scaffold in vitro while promoting neovascularization in vivo. We therefore propose that the SF porous scaffold fabricated here may be an attractive candidate for use as a potential vascular graft for implantation based on its high porosity, excellent blood compatibility and mild fabrication process.

The role of vascular-derived perlecan in modulating cell adhesion, proliferation and growth factor signaling

Smooth muscle cell proliferation can be inhibited by heparan sulfate proteoglycans whereas the removal or digestion of heparan sulfate from perlecan promotes their proliferation. In this study we characterized the glycosaminoglycan side chains of perlecan isolated from either primary human coronary artery smooth muscle or endothelial cells and determined their roles in mediating cell adhesion and proliferation, and in fibroblast growth factor (FGF) binding and signaling. Smooth muscle cell perlecan was decorated with both heparan sulfate and chondroitin sulfate, whereas endothelial perlecan contained exclusively heparan sulfate chains. Smooth muscle cells bound to the protein core of perlecan only when the glycosaminoglycans were removed, and this binding involved a novel site in domain III as well as domain V/endorepellin and the α2β1 integrin. In contrast, endothelial cells adhered to the protein core of perlecan in the presence of glycosaminoglycans. Smooth muscle cell perlecan bound both FGF1 and FGF2 via its heparan sulfate chains and promoted the signaling of FGF2 but not FGF1. Also endothelial cell perlecan bound both FGF1 and FGF2 via its heparan sulfate chains, but in contrast, promoted the signaling of both growth factors. Based on this differential bioactivity, we propose that perlecan synthesized by smooth muscle cells differs from that synthesized by endothelial cells by possessing different signaling capabilities, primarily, but not exclusively, due to a differential glycanation. The end result is a differential modulation of cell adhesion, proliferation and growth factor signaling in these two key cellular constituents of blood vessels.

A critical role for proinflammatory behavior of smooth muscle cells in hemodynamic initiation of intracranial aneurysm

Background

Intracranial aneurysm initiation is poorly understood, although hemodynamic insult is believed to play an important role in triggering the pathology. It has recently been found in a rabbit model that while macrophages are absent during hemodynamic aneurysm initiation, matrix metalloproteinases (MMPs) are elevated and co-localize with smooth muscle cells (SMCs). This study investigates whether SMCs play a mechanistic role in aneurysm initiation triggered by hemodynamics.

Methods

Aneurysmal damage was induced at the basilar terminus via bilateral common carotid artery ligation in rabbits (n = 45, plus 7 sham controls). 16 ligated rabbits were treated with doxycycline to inhibit MMPs, 7 received clodronate liposomes to deplete circulating monocytes, and the rest received no drug. Effects of the treatments on aneurysm development were assessed histologically 5 days and 6 months after ligation. MMP production and expression of inflammatory markers by SMCs was monitored by immunohistochemistry and in situ hybridization.

Results

Treatment with doxycycline attenuated aneurysmal development examined at 5 days and 6 months, suggesting that MMPs contribute to aneurysm initiation. However, systemic depletion of macrophages did not decrease MMPs or suppress aneurysmal development. Immunofluorescence showed that during aneurysm initiation MMP-2 and MMP-9 were distributed in SMCs, and in situ hybridization indicated that they were transcribed by SMCs. In regions of early aneurysmal lesion, SMCs exhibited decreased expression of smooth muscle actin and increased NF-κB and MCP-1 expressions.

Conclusions

During aneurysm initiation triggered by hemodynamics, SMCs rather than macrophages are responsible for MMP production that is critical for aneurysmal lesion development. These SMCs exhibit proinflammatory behavior.

Evaluation of a novel thermosensitive heparin-poloxamer hydrogel for improving vascular anastomosis quality and safety in a rabbit model

Despite progress in the design of advanced surgical techniques, stenosis recurs in a large percentage of vascular anastomosis. In this study, a novel heparin-poloxamer (HP) hydrogel was designed and its effects for improving the quality and safety of vascular anastomosis were studied. HP copolymer was synthesized and its structure was confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (¹H-NMR). Hydrogels containing HP were prepared and their important characteristics related to the application in vascular anastomosis including gelation temperature, rheological behaviour and micromorphology were measured. Vascular anastomosis were performed on the right common carotid arteries of rabbits, and the in vivo efficiency and safety of HP hydrogel to achieve vascular anastomosis was verified and compared with Poloxamer 407 hydrogel and the conventional hand-sewn method using Doppler ultrasound, CT angiograms, scanning electron microscopy (SEM) and histological technique. Our results showed that HP copolymer displayed special gel-sol-gel phase transition behavior with increasing temperature from 5 to 60 °C. HP hydrogel prepared from 18 wt% HP solution had a porous sponge-like structure, with gelation temperature at approximately 38 °C and maximum elastic modulus at 10,000 Pa. In animal studies, imaging and histological examination of rabbit common jugular artery confirmed that HP hydrogel group had similar equivalent patency, flow and burst strength as Poloxamer 407 group. Moreover, HP hydrogel was superior to poloxamer 407 hydrogel and hand-sewn method for restoring the functions and epithelial structure of the broken vessel junctions after operation. By combining the advantages of heparin and poloxamer 407, HP hydrogel holds high promise for improving vascular anastomosis quality and safety.

Heparin and related drugs: beyond anticoagulant activity

Heparin has been widely used as an anticoagulant for more than 80 years. However, there is now considerable evidence that heparin also possesses anti-inflammatory activity, both experimentally and clinically. Importantly in many instances, the anti-inflammatory actions of heparin are independent of anticoagulant activity raising the possibility of developing novel drugs based on heparin that retain the anti-inflammatory activity. Heparin exhibits anti-inflammatory activities via a variety of mechanisms including neutralization of cationic mediators, inhibition of adhesion molecules, and the inhibition of heparanase, all involved in leukocyte recruitment into tissues. It is anticipated that furthering our understanding of the anti-inflammatory actions of heparin will lead to the development of novel anti-inflammatory drugs for a variety of clinical indications.

The antineoplastic effect of low-molecular-weight heparins - a literature review

There is some evidence for the antitumor effect of heparins, especially the low-molecular-weight ones. The authors discuss the potential mechanism of this antineoplastic effect and present results from several in vitro and in vivo experiments. The clinical trials concerning the impact of low-molecular-weight heparins on the tumor and on the patients' survival are described. The objective was to find out if heparins could be administered as an antitumor drug, independently of their anticoagulatory properties. The antitumor role of tissue factor, heparinase, chemokines, stromal proteins, cellular interactions as well as angiogenesis and immunology seems certain. The results of the available studies seem promising but large clinical trials are necessary in order to confirm the antineoplastic effect of the low-molecular-weight heparins and to approve them for standard anticancer treatment. It could be a breakthrough in modern oncology.

The effect of controlled release of PDGF-BB from heparin-conjugated electrospun PCL/gelatin scaffolds on cellular bioactivity and infiltration

Heparin-conjugated electrospun poly(ε-caprolactone) (PCL)/gelatin scaffolds were developed to provide controlled release of platelet-derived growth factor-BB (PDGF-BB) and allow prolonged bioactivity of this molecule. A mixture of PCL and gelatin was electrospun into three different morphologies. Next, heparin molecules were conjugated to the reactive surface of the scaffolds. This heparin-conjugated scaffold allowed the immobilization of PDGF-BB via electrostatic interaction. In vitro PDGF-BB release profiles indicated that passive physical adsorption of PDGF-BB to non-heparinized scaffolds resulted in an initial burst release of PDGF-BB within 5 days, which then leveled off. However, electrostatic interaction between PDGF-BB and the heparin-conjugated scaffolds gave rise to a sustained release of PDGF-BB over the course of 20 days without an initial burst. Moreover, PDGF-BB that was strongly bound to the heparin-conjugated scaffolds enhanced smooth muscle cell (SMC) proliferation. In addition, scaffolds composed of 3.0 μm diameter fibers that were immobilized with PDGF-BB accelerated SMC infiltration into the scaffold when compared to scaffolds composed of smaller diameter fibers or scaffolds that did not release PDGF-BB. We concluded that the combination of the large pore structure in the scaffolds and the heparin-mediated delivery of PDGF-BB provided the most effective cellular interactions through synergistic physical and chemical cues.