Cells, cytokines and cellular immunity in the pathogenesis of fibroproliferative vasculopathies

Modulation of Cathepsin L Expression in the Coronary Arteries of Atherosclerotic Swine

INTRODUCTION

Neointimal hyperplasia (NIH) and restenosis after percutaneous transluminal coronary angioplasty (PTCA) and intravascular stenting remain a problem on a long-term basis by causing endothelial denudation and damage to the intima and media. Vascular sterile inflammation has been attributed to the formation of NIH. Cathepsin L (CTSL), a lysosome protease, is associated with diet-induced atherogenesis. Vitamin D regulates the actions and regulatory effects of proteases and protease inhibitors in different cell types. Objectives of this study are to evaluate the modulatory effect of vitamin D on CTSL activity in post-PTCA coronary arteries of atherosclerotic swine.

METHODS

Yucatan microswine were fed with high-cholesterol atherosclerotic diets. The swine were stratified to receive three diets: (1) vitamin D-deficient diet, (2) vitamin D-sufficient diet, and (3) vitamin D-supplement diet. After 6 mo, PTCA was performed in the left circumflex coronary artery (LCx). After 1 y, angiography and optical coherence tomography imaging were performed, and swine was euthanized. Coronary arteries were embedded in paraffin. Tissue sections were stained with hematoxylin and eosin. Expression of Ki67 and CTSL were evaluated by immunofluorescence.

RESULTS

Increased number of Ki67 + cells were observed in the postangioplasty LCx in vitamin D-deficient compared with vitamin D-sufficient or vitamin D-supplemented swine. Notably, the expression of CTSL was significantly increased in postangioplasty LCx of vitamin D-deficient swine compared with the vitamin D-sufficient or vitamin D-supplemented animal groups.

CONCLUSIONS

Increased expression of CTSL correlates with the formation of NIH in the PTCA-injured coronary arteries. However, in the presence of sufficient or supplemented levels of vitamin D in the blood, CTSL expression was significantly reduced.

Sex differences in pulmonary arterial hypertension: role of infection and autoimmunity in the pathogenesis of disease

Registry data worldwide indicate an overall female predominance for pulmonary arterial hypertension (PAH) of 2–4 over men. Genetic predisposition accounts for only 1–5% of PAH cases, while autoimmune diseases and infections are closely linked to PAH. Idiopathic PAH may include patients with undiagnosed autoimmune diseases based on the relatively high presence of autoantibodies in this group. The two largest PAH registries to date report a sex ratio for autoimmune connective tissue disease-associated PAH of 9:1 female to male, highlighting the need for future studies to analyze subgroup data according to sex. Autoimmune diseases that have been associated with PAH include female-dominant systemic sclerosis, systemic lupus erythematosus, rheumatoid arthritis, Sjögren’s syndrome, and thyroiditis as well as male-dominant autoimmune diseases like myocarditis which has been linked to HIV-associated PAH. The sex-specific association of PAH to certain infections and autoimmune diseases suggests that sex hormones and inflammation may play an important role in driving the pathogenesis of disease. However, there is a paucity of data on sex differences in inflammation in PAH, and more research is needed to better understand the pathogenesis underlying PAH in men and women. This review uses data on sex differences in PAH and PAH-associated autoimmune diseases from registries to provide insight into the pathogenesis of disease.

Enhanced biocompatibility of CD47-functionalized vascular stents

The effectiveness of endovascular stents is hindered by in-stent restenosis (ISR), a secondary re-obstruction of treated arteries due to unresolved inflammation and activation of smooth muscle cells in the arterial wall. We previously demonstrated that immobilized CD47, a ubiquitously expressed transmembrane protein with an established role in immune evasion, can confer biocompatibility when appended to polymeric surfaces. In present studies, we test the hypothesis that CD47 immobilized onto metallic surfaces of stents can effectively inhibit the inflammatory response thus mitigating ISR. Recombinant CD47 (recCD47) or a peptide sequence corresponding to the Ig domain of CD47 (pepCD47), were attached to the surfaces of both 316L-grade stainless steel foils and stents using bisphosphonate coordination chemistry and thiol-based conjugation reactions to assess the anti-inflammatory properties of CD47-functionalized surfaces. Initial in vitro and ex vivo analysis demonstrated that both recCD47 and pepCD47 significantly reduced inflammatory cell attachment to steel surfaces without impeding on endothelial cell retention and expansion. Using a rat carotid stent model, we showed that pepCD47-functionalized stents prevented fibrin and platelet thrombus deposition, inhibited inflammatory cell attachment, and reduced restenosis by 30%. It is concluded that CD47-modified stent surfaces mitigate platelet and inflammatory cell attachment, thereby disrupting ISR pathophysiology.

Dichloroacetate prevents restenosis in preclinical animal models of vessel injury

Despite the introduction of antiproliferative drug-eluting stents, coronary heart disease remains the leading cause of death in the United States. In-stent restenosis and bypass graft failure are characterized by excessive smooth muscle cell (SMC) proliferation and concomitant myointima formation with luminal obliteration. Here we show that during the development of myointimal hyperplasia in human arteries, SMCs show hyperpolarization of their mitochondrial membrane potential (ΔΨm) and acquire a temporary state with a high proliferative rate and resistance to apoptosis. Pyruvate dehydrogenase kinase isoform 2 (PDK2) was identified as a key regulatory protein, and its activation proved necessary for relevant myointima formation. Pharmacologic PDK2 blockade with dichloroacetate or lentiviral PDK2 knockdown prevented ΔΨm hyperpolarization, facilitated apoptosis and reduced myointima formation in injured human mammary and coronary arteries, rat aortas, rabbit iliac arteries and swine (pig) coronary arteries. In contrast to several commonly used antiproliferative drugs, dichloroacetate did not prevent vessel re-endothelialization. Targeting myointimal ΔΨm and alleviating apoptosis resistance is a novel strategy for the prevention of proliferative vascular diseases.

Effects of chemokine-like factor 1 on vascular smooth muscle cell migration and proliferation in vascular inflammation

OBJECTIVE

Vascular smooth muscle cell (VSMC) migration and proliferation are key components of vascular inflammation that may lead to atherosclerosis and restenosis, in which cytokines are considered as pivotal factors regarding recruitment of VSMC. A member of recently described family of chemokines, chemokine-like factor 1 (CKLF1), displays a wide spectrum of chemotaxis. This study investigated the role of CKLF1 in VSMC migration and proliferation during the process of vascular inflammation.

METHODS AND RESULTS

: The effects of CKLF1 on migration, proliferation and neointimal formation were investigated in cultured VSMCs, rat balloon injured arteries and human atherosclerotic plaques. CKLF1 overexpression greatly enhanced, whereas shRNA knockdown markedly retarded, VSMC migration and proliferation in vitro. In addition, CKLF1 protein accumulated preferentially in neointima of the injured rat arteries in vivo. CKLF1 overexpression resulted in a 2.5-fold increase in intimal thickness. In contrast, shRNA-mediated CKLF1 knockdown significantly suppressed neointima formation by 70% compared that in control group. Intriguingly, besides animal model, higher level of CKLF1 was observed in human atherosclerotic plaques than that in normal arteries.

CONCLUSION

CKLF1 plays an essential role in migration and proliferation of VSMCs, which in turn facilitated neointimal hyperplasia and atherosclerosis. Inhibition of CKLF1 activity provides a potential target for the prevention of atherosclerosis and restenosis.

Intimal thickening of meningeal arteries after serial corticectomies for Rasmussen encephalitis

Rasmussen encephalitis is a rare cause of intractable epilepsy in children. Between 2008 and 2010, 4 patients had second cortical resections performed after a primary corticectomy for Rasmussen encephalitis. In each case, we observed some degree of vessel wall change in leptomeningeal arteries, consisting of moderate to moderately severe intimal hyperplasia. The intervals between original resection and second operation ranged from 8 months to 10 years. Ages of the patients ranged from 9 to 12 years at their first resection and from 10 to 19 years at the time of revision. Four other Rasmussen encephalitis cases operated upon in the years 2006 to 2010 and 2 surgical revisions for severe cortical dysplasia, 1 for mild cortical dysplasia and 1 for recurrent dysembryoplastic neuroepithelial tumor, did not show significant vascular abnormalities (with surgical intervals of 10 months to 16 years). Leptomeningeal intimal hyperplasia appears to develop in the interval between repeated cortical resections for Rasmussen encephalitis, an inflammatory disorder. The pathogenesis of this vascular change may be related to meningeal inflammation in Rasmussen encephalitis. This finding in children undergoing surgical resection for Rasmussen encephalitis may itself lead to "secondary" ischemic change that contributes to worsening of epilepsy.

Restenosis and therapy

The vascular disease involves imbalanced function of the blood vessels. Risk factors playing a role in development of impaired vessel functions will be briefly discussed. In ischemia/reperfusion (I/R), ischemic hypoxia is one of the cardinal risk factors of restenosis. Various insults are shown to initiate the phenotype switch of VSMCs. The pathological process, leading to activated inflammatory process, complement activation, and release of growth factors, initiate the proliferation of VSMCs in the media and cause luminal narrowing and impaired vascular function. The review summarizes the alteration process and demonstrates some of the clinical genetic background showing the role of complement and the genotypes of mannose-binding lectin (MBL2). Those could be useful markers of carotid restenosis after stent implantation. Gene therapy and therapeutic angiogenesis is proposed for therapy in restenosis. We suggest a drug candidate (iroxanadine), which ensures a noninvasive treatment by reverse regulation of the highly proliferating VSMCs and the disturbed function of ECs.

Characterization of the chemotactic and mitogenic response of SMCs to PDGF-BB and FGF-2 in fibrin hydrogels

The delivery of growth factors to cellularize biocompatible scaffolds like fibrin is a commonly used strategy in tissue engineering. We characterized smooth muscle cells (SMC) proliferation and chemotaxis in response to PDGF-BB and FGF-2, alone and in combination, in 2D culture and in 3D fibrin hydrogels. While both growth factors induced an equipotent mitogenic response in 2D culture, only FGF-2 was significantly mitogenic for SMCs in 3D culture. Only PDGF-BB was significantly chemotactic in a modified Boyden chamber assay. In a 3D assay of matrix invasion, both growth factors induced an invasive response into the fibrin hydrogel in both proliferating and nonproliferating, mitomycin C (MMC) treated cells. The invasive response was less attenuated by the inhibition of proliferation in PDGF-BB stimulated cells compared with FGF-2 stimulated cells. We conclude that SMCs cultured in fibrin hydrogels have a more robust chemotactic response to PDGF-BB compared with FGF-2, and that the response to FGF-2 is more dependent on cell proliferation. Delivery of both growth factors together potentiates the chemotactic, but not mitogenic response to either growth factor alone.

Can eccentric arterial plaques alone cause flow stagnation points and favour thrombus incorporation?

We have used an experimental model of aorta stenosis, with a Plexiglas plug, simulating a stable atheromatous plaque that promotes local turbulence and thrombosis. With animal survival of more than 24 h, we followed the partial fibrinolysis of the thrombus as well as its posterior organization and incorporation to the arterial wall as a neointima for up to 30 days. The mushroom plug form permitted the development of recirculation and stasis areas around it, favouring this evolution. Despite noted limitations, this study demonstrates that thrombus incorporation can contribute to plaque extension, as it can promote recirculation and stasis areas.

Heparin coating of small-caliber decellularized xenografts reduces macrophage infiltration and intimal hyperplasia

Small-caliber decellularized xenografts with surface heparin coating are known to reduce in vivo thrombogenicity. This study was performed to examine whether heparin coating on the small-caliber decellularized xenografts would reduce macrophage infiltration and intimal hyperplasia. In a rabbit model of bilateral carotid implantation, each of the animals (n = 18) received a heparin-coated decellularized xenograft from a canine carotid artery on one side and a nonheparin-coated one on the other side. These experiments were terminated respectively at 1 week (n = 6), 3 weeks (n = 6), and 12 weeks (n = 6). Results showed that, compared with the nonheparin-coated grafts, the heparin-coated grafts had significantly less macrophage infiltration 1 week after implantation, identified by the mouse antirabbit macrophage antibody (RAM11)-positive cells on the vascular wall, covering all the proximal, middle, and distal parts of the grafts (P < 0.01). Moreover, the heparin-coated grafts also showed less deposition of proliferation cell nuclear antigen (PCNA)-positive cells on the vascular wall, indicating less cell proliferation, which was significant not only at 1 week (P < 0.01) but also at 12 weeks (P < 0.01). Intimal hyperplasia, measured by the intimal : media (I : M) ratio, was found similar in both groups at 1 and 3 weeks. However, the I : M ratio was significantly lower in the heparin-coated group than in the nonheparin-coated group at 12 weeks, especially in the proximal anastomosis area (0.76 +/- 0.12 vs. 0.345 +/- 0.06, P < 0.01). Heparin coating of small-caliber decellularized xenografts is associated with an early reduction of macrophage infiltration and intimal hyperplasia in a rabbit model of bilateral carotid artery implantation for 12 weeks. Thus, heparin coating appears to deliver not only the antithrombogeneity but also the antiproliferative property for small-caliber decellularized xenografts.

Early onset of fibrosis within the arterial media in a rat model of type 2 diabetes mellitus with erectile dysfunction

OBJECTIVES

To determine, in the obese Zucker fa/fa rat (OZR), whether the loss in smooth muscle cells (SMCs) as well as the increase in fibrosis that occurs within the corpora cavernosa accompanying corporal veno-occlusive dysfunction (CVOD), also occurs within the media of the arterial tree.

MATERIALS AND METHODS

The penis and aorta from both 7-month-old male diabetic OZR (5 months of diabetes) and aged-matched nondiabetic lean Zucker rats (LZR) rats were harvested (eight per group). The penis and aorta were subjected to histo- or immnohistochemistry, followed by quantitative image analysis (QIA) to determine the contents of SMC, collagen and the pro-fibrotic transforming growth factor (TGF)beta1. The turnover of SMCs was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) and proliferating cell nuclear antigen (PCNA) assays. Quantitative Western blots determined calponin (SMC marker) and PCNA, and hydroxyproline was used for collagen. In vitro relaxation of corporal strips was measured.

RESULTS

In vitro relaxation of corporal tissue from OZR was considerably less than in the LZR. In the media of the penile dorsal artery (PDA) of OZR, there was a considerable reduction in the SMC content and the SMC/collagen ratio, as well as an increase in apoptosis, but there were no changes in PCNA or TGFbeta1 expression, or in the intima-media/lumen ratio. In the aorta of the OZR, in contrast to the PDA, there was a reduction in PCNA as well as a more pronounced decrease in the SMC/collagen ratio, mainly from an increase in collagen, but there were no changes in TGFbeta1 or the wall/lumen morphometry. In the OZR, Western blots of aortic tissue confirmed the decrease in PCNA and a reduction in the SMC marker calponin.

CONCLUSIONS

These data show that 5 months after the onset of hyperglycaemia in the OZR, the rats develop both abnormal corporal SMC relaxation and a generalized fibrosis of the arterial media of both the large and small diameter vessels. It is possible that this pan-fibrosis of the media of the arterial system might contribute to the diabetes-related ED that occurs during this period in this rat model.

Focal and multifocal diabetic neuropathies

Diabetic neuropathy is the most common neuropathy in industrialized countries, with a remarkable range of clinical manifestations. The vast majority of the patients with clinical diabetic neuropathy have a distal symmetrical form that progress following a fiber-length dependent pattern, with predominant sensory and autonomic manifestations. This pattern of neuropathy is associated with a progressive distal axonopathy. Patients are exposed to trophic changes in the feet, pains and autonomic disturbances. Less often, diabetic patients may develop focal and multifocal neuropathy that includes cranial nerve involvement, limb and truncal neuropathies. This neuropathic pattern tends to occur after 50 years of age, mostly in patients with longstanding diabetes mellitus. The LDDP does not show any trend to improvement and either relentlessly progresses or remain relatively stable over years. Conversely the focal diabetic neuropathies, which are often associated with inflammatory vasculopathy on nerve biopsies, remain self limited, sometimes after a relapsing course.

Temporal PTEN inactivation causes proliferation of saphenous vein smooth muscle cells of human CABG conduits

Internal mammary artery (IMA) coronary artery bypass grafts (CABG) are remarkably resistant to intimal hyperplasia (IH) as compared to saphenous vein (SV) grafts following aorto-coronary anastomosis. The reason behind this puzzling difference still remains an enigma. In this study, we examined the effects of IGF-1 stimulation on the PI3K-AKT/PKB pathway mediating proliferation of smooth muscle cells (SMCs) of IMA and SV origin and the specific contribution of phosphatase and tensin homologue (PTEN) in regulating the IGF-1-PI3K-AKT/PKB axis under these conditions. Mitogenic activation with IGF-1, time-dependently stimulated the phosphorylation of PI3K and AKT/PKB in the SV SMCs to a much greater extent than the IMA. Conversely, PTEN was found to be significantly more active in IMA SMCs. Transient overexpression of PTEN in SMCs of SV and IMA inhibited AKT/PKB activity and upstream of AKT/PKB, caused a reduction of IGF-1 receptors. Downstream, PTEN overexpression in SV SMCs induced the transactivation of tumour suppressor protein p53 by down-regulating the expression of its inhibitor MDM2. However, PTEN overexpression had no significant effect on MDM2 and p53 expression in IMA SMCs. PTEN overexpression inhibited IGF-1-induced SMC proliferation in both SV and IMA. PTEN suppression, induced by siRNA transfection of IMA SMCs diminished the negative regulation of PI3K-PKB signalling leading to greater proliferative response induced by IGF-1 stimulation. Thus, we show for the first time that early inactivation of PTEN in SV SMCs leads to temporally increased activity of the pro-hyperplasia PI3K-AKT/PKB pathway leading to IH-induced vein graft occlusion. Therefore, modulation of the PI3K-AKT/PKB pathway via PTEN might be a novel and effective strategy in combating SV graft failure following CABG.

The role of nitric oxide in the pathophysiology of intimal hyperplasia

Since its discovery, nitric oxide (NO) has emerged as a biologically important molecule and was even named Molecule of the Year by Science magazine in 1992. Specific to our interests, NO has been implicated in the regulation of vascular pathology. This review begins with a summary of the molecular biology of NO, from its discovery to the mechanisms of endogenous production. Next, we turn our attention to describing the arterial injury response of neointimal hyperplasia, and we review the role of NO in the pathophysiology of neointimal hyperplasia. Finally, we review the literature regarding NO-based therapies. This includes the development of inhalational-based NO therapies, systemically administered L-arginine and NO donors, NO synthase gene therapy, locally applied NO donors, and NO-releasing prosthetic materials. By reviewing the current literature, we emphasize the tremendous clinical potential that NO-based therapies can have on the development of neointimal hyperplasia.