Are Sodium-Glucose Cotransporter-2 Inhibitors the Cherry on Top of Cardio-Oncology Care?

The increasing aging of the population combined with improvements in cancer detection and care has significantly improved the survival and quality of life of cancer patients. These benefits are hampered by the increase of cardiovascular diseases being heart failure the most frequent manifestation of cardiotoxicity and becoming the major cause of morbidity and mortality among cancer survivor. Current strategies to prevent cardiotoxicity involves different approaches such as optimal management of CV risk factors, use of statins and/or neurohormonal medications, and, in some cases, even the use of chelating agents. As a class, SGLT2-i have revolutionized the therapeutic horizon of HF patients independently of their ejection fraction or glycemic status. There is an abundance of data from translational and observational clinical studies supporting a potential beneficial role of SGLT2-i in mitigating the cardiotoxic effects of cancer patients receiving anthracyclines. These findings underscore the need for more robust clinical trials to investigate the effect on cardiovascular outcomes of the prophylactic SGLT2-i treatment in patients undergoing cancer treatment.

SGLT2-Inhibitors on HFpEF Patients. Role of Ejection Fraction.

Results from DELIVER trial and publication of EMPEROR-Preserved with sodium-glucose cotransporter 2 (SGLT2) inhibitors in patients with heart failure (HF) with ejection fraction (EF) > 40% represent a significant step forward in the treatment of HF with preserved EF (HFpEF). However, detailed analysis and attenuation of effect at higher EF levels have sparked some doubts about whether empagliflozin is effective across the entire spectrum of EF. HFpEF is no longer considered as one disease entity, but has been reconceptualized as a heterogenous group of phenotypes with derangements in multiple organ systems, driven by comorbidities. This heterogeneity suggests that it should not be considered as a single group in terms of treatment goals or clinical approach. Future research at the higher range of EF should ideally tailor investigations for unequivocally preserved EF (> 50%), consider the dynamic nature of EF over time, and use low-variability imaging techniques such as CMR. Furthermore, classifications based on pathophysiology and HF phenotypes beyond the EF construct will shape the design of future trials and help narrow down groups of patients who may respond to personalized treatment.

Rationale and Design of the SOTA-P-CARDIA Trial (ATRU-V): Sotagliflozin in HFpEF Patients Without Diabetes.

Heart failure with preserved ejection fraction (HFpEF) is now the most common form of heart failure (HF). This syndrome is associated with an elevated morbi-mortality, and effective therapies are urgently needed. Sodium-glucose co-transporter 2 inhibitors (SGLT2i) are the first pharmacological class that has demonstrated to reduce hospitalization and cardiovascular mortality in large clinical trials in HFpEF. Furthermore, the dual SGLT 1/2 inhibitor sotagliflozin has shown a reduction in cardiovascular outcomes in diabetic HF patients, regardless of ejection fraction Sotagliflozin on Cardiovascular Events in Patients with Type 2 Diabetes Post Worsening Heart Failure (SOLOIST-WHF) Trial, and prevents the development of HF in patients with diabetes and chronic kidney disease Sotagliflozin on Cardiovascular and Renal Events in Patients with Type 2 Diabetes and Moderate Renal Impairment Who Are at Cardiovascular Risk (SCORED) trial. The major objective of the Sotagliflozin in Heart Failure With Preserved Ejection Fraction Patients (SOTA-P-CARDIA) trial (NCT05562063) is to investigate whether the observed cardiorenal benefits of sotagliflozin in HF patients with diabetes can be extended to a non-diabetic population. The SOTA-P-CARDIA is a prospective, randomized, double-blinded, placebo-controlled study that will randomize non-diabetic patients with the universal definition of HFpEF (ejection fraction > 50% assessed the day of randomization). Qualifying patients will be randomized, in blocks of 4, to receive either sotagliflozin or placebo for a period of 6 months. The primary outcome is changes in left ventricular mass by cardiac magnetic resonance from randomization to end of the study between the groups. Secondary end points include changes in peak VO2; myocardial mechanics, interstitial myocardial fibrosis, and volume of epicardial adipose tissue; distance in the 6-min walk test; and quality of life. Finally, the authors expect that this trial will help to clarify the potential benefits of the use of sotagliflozin in non-diabetic HFpEF patients.

Renal and Cardiovascular Metabolic Impact Caused by Ketogenesis of the SGLT2 Inhibitors.

Sodium-glucose cotransporter type 2 inhibitors (SGLT2i) are glycosuric drugs that were originally developed for the treatment of type 2 diabetes mellitus (T2DM). There is a hypothesis that SGLT2i are drugs that are capable of increasing ketone bodies and free fatty acids. The idea is that they could serve as the necessary fuel, instead of glucose, for the purposes of cardiac muscle requirements and could explain antihypertensive effects, which are independent of renal function. The adult heart, under normal conditions, consumes around 60% to 90% of the cardiac energy that is derived from the oxidation of free fatty acids. In addition, a small proportion also comes from other available substrates. In order to meet energy demands with respect to achieving adequate cardiac function, the heart is known to possess metabolic flexibility. This allows it to switch between different available substrates in order to obtain the energy molecule adenosine triphosphate (ATP), thereby rendering it highly adaptive. It must be noted that oxidative phosphorylation in aerobic organisms is the main source of ATP, which is a result of reduced cofactors. These cofactors include nicotine adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2), which are the result of electron transfer and are used as the enzymatic cofactors that are involved in the respiratory chain. When there is an excessive increase in energy nutrients-such as glucose and fatty acids-which occur in the absence of a parallel increase in demand, a state of nutrient surplus (which is better known as an excess in supply) is created. The use of SGLT2i at the renal level has also been shown to generate beneficial metabolic alterations, which are obtained by reducing the glucotoxicity that is induced by glycosuria. Together with the reduction in perivisceral fat in various organs, such alterations also lead to the use of free fatty acids in the initial stages of the affected heart. Subsequently, this results in an increase in production with respect to ketoacids, which are a more available energy fuel at the cellular level. In addition, even though their mechanism is not fully understood, their vast benefits render them of incredible importance for the purposes of further research.

Prolyl Hydroxylase Inhibitors: a New Opportunity in Renal and Myocardial Protection.

Hypoxia, via the activity of hypoxia-inducible factors (HIFs), plays a crucial role in fibrosis, inflammation, and oxidative injury, processes which are associated with progression of cardiovascular and kidney diseases. HIFs are key transcription heterodimers consisting of regulatory α-subunits (HIF-1α, HIF-2α, HIF-3α) and a constitutive ß-subunit (HIF-ß). The stability of HIFs is regulated by the prolyl hydroxylases (PHDs). Specific PHD inhibitors (PHD-i) are being investigated as a therapeutic approach to modulate the cellular signaling pathways and harness the native protective adaptive responses to hypoxia. Selective inhibition of PHD leads to the stabilization of the HIFs, which is the transcriptional gatekeeper of a multitude of genes involved in angiogenesis, energy metabolism, apoptosis, inflammation, and fibrosis. PHD-i downregulate hepcidin, improve iron absorption, and increase the endogenous production of erythropoietin. Furthermore, this pharmacological group has also been proven to ameliorate ischemic injuries in several organs, opening a new and promising field in cardiovascular research.. In this review, we present the basic and clinical potential of PHD-i treatment in different scenarios, such as ischemic heart disease, cardiac hypertrophy and heart failure, and their interplay with other pharmacological agents with proven cardiovascular benefits, such as sodium-glucose cotransporter 2 (SGLT2) inhibitors.

Is the Endothelium the Missing Link in the Pathophysiology and Treatment of COVID-19 Complications?

Patients with COVID-19 present a wide spectrum of disease severity, from asymptomatic cases in the majority to serious disease leading to critical care and even death. Clinically, four different scenarios occur within the typical disease timeline: first, an incubation and asymptomatic period; second, a stage with mild symptoms due mainly to the virus itself; third, in up to 20% of the patients, a stage with severe symptoms where a hyperinflammatory response with a cytokine storm driven by host immunity induces acute respiratory distress syndrome; and finally, a post-acute sequelae (PASC) phase, which present symptoms that can range from mild or annoying to actually quite incapacitating. Although the most common manifestation is acute respiratory failure of the lungs, other organs are also frequently involved. The clinical manifestations of the COVID-19 infection support a key role for endothelial dysfunction in the pathobiology of this condition. The virus enters into the organism via its interaction with angiotensin-converting enzyme 2-receptor that is present prominently in the alveoli, but also in endothelial cells, which can be directly infected by the virus. Cytokine release syndrome can also drive endothelial damage independently. Consequently, a distinctive feature of SARS-CoV-2 infection is vascular harm, with severe endothelial injury, widespread thrombosis, microangiopathy, and neo-angiogenesis in response to endothelial damage. Therefore, endothelial dysfunction seems to be the pathophysiological substrate for severe COVID-19 complications. Biomarkers of endothelial injury could constitute strong indicators of disease progression and severity. In addition, the endothelium could represent a very attractive target to both prevent and treat these complications. To establish an adequate therapy, the underlying pathophysiology and corresponding clinical stage should be clearly identified. In this review, the clinical features of COVID-19, the central role of the endothelium in COVID-19 and in other pathologies, and the potential of specific therapies aimed at protecting the endothelium in COVID-19 patients are addressed.

Effects of electret coating technology on coronary stent thrombogenicity.

Stent thrombosis (ST) is a catastrophic event and efforts to reduce its incidence by altering blood-stent interactions are longstanding. A new electret coating technology that produces long-lasting negative charge on stent surface could make them intrinsically resistant to thrombosis. We assessed the thrombogenicity of stents using an annular perfusion model with confocal microscopy, and determined the efficacy of electret coating technology to confer thrombo-resistant properties to standard stents. Using an annular perfusion chamber, Bare Metal Stent (BMS), standard uncoated DES (DES), and Electret-coated DES (e-DES) were exposed to human blood under arterial flow conditions. Deposits of fibrinogen and platelets on the stent surface were analyzed using immunofluorescence staining and confocal microscopy. Surface coverage by fibrinogen and platelets and the deposit/aggregate size were quantified using computerized morphometric analysis. The experimental methodology produced consistent, quantifiable results. Area of stent surface covered by fibrinogen and platelets and the average size of the deposits/aggregates were lowest for e-DES and highest on BMS, with DES in the middle. The size of fibrinogen-deposits showed no differences between the stents. The testing methodology used in our study successfully demonstrated that electret coating confers significant antithrombotic property to DES stents. These findings warrant confirmation in a larger study.

Direct Oral Anticoagulants and Coronary Artery Disease: The Debacle of the Aspirin Era?

Long-standing aspirin is the cornerstone to prevent recurrence of thrombotic events in patients with ischemic heart disease. However, clopidogrel, a more potent antiplatelet agent, is preferred over aspirin in targeted populations, including those with a high risk of gastrointestinal bleeding. In addition, clopidogrel offers superior oral tolerance, and it may reduce the rates of intracranial hemorrhages compared with aspirin. However, an extensive inhibition of the coagulation cascade seems to be reasonable to minimize thrombotic events in such patients. After several failed exploratory investigations in the past with vitamin K antagonists, the newest direct oral anticoagulants may represent an alternative. To counterbalance bleeding complications, a low dose of these agents should be considered. Few publications have already showed promising results with the combination of clopidogrel and low-dose direct oral anticoagulants. Further investigations should be addressed to elucidate whether this is the downfall of the aspirin era for secondary prevention of atherosclerotic cardiovascular events.

Idarucizumab, but not procoagulant concentrates, fully restores dabigatran-altered platelet and fibrin components of hemostasis.

BACKGROUND: Comparative studies on the restoration of hemostasis with different reversal agents after dabigatran therapy have not been performed. We compared the efficacy and prothrombotic potential of the specific antidote idarucizumab with that of previously recommended non-specific procoagulant concentrates. STUDY DESIGN AND METHODS: We explored the in vitro effects of dabigatran (184 ng/mL) on fibrin and platelet-aggregate formation onto a damaged vessel under flow conditions (600 s-1 ). The reversal mechanisms and efficacy of idarucizumab (0.3-3 mg/mL) were compared with that of the non-specific procoagulant concentrates aPCC (25-75 U/Kg), PCC (70 U/Kg), or rFVIIa (120 µg/Kg). Generation of thrombin and prothrombin fragment (F1 + 2), and thromboelastometry parameters of clot formation were measured. RESULTS: Dabigatran caused pronounced reductions in fibrin (87%) and platelet interactions (36%) with damaged vessels (p < 0.01) and significantly impaired thrombin generation and thromboelastometric parameters (delayed dynamics and reduced firmness). Idarucizumab completely normalized rates of fibrin and platelet coverage to baseline values in flow studies; and reversed the alterations in thrombin generation, F1 + 2 and thromboelastometry parameters produced by dabigatran. In comparison, aPCC and PCC only partially compensated for the dabigatran-induced alterations in fibrin deposition, but were unable to fully restore them to baseline values. Reversal with aPCC or PCC improved the majority of alterations in coagulation-related tests, but tended to overcompensate thrombin generation kinetics and significantly increased F1 + 2 levels. CONCLUSION: Idarucizumab antagonizes alterations of direct and indirect biomarkers of hemostasis caused by dabigatran. In our studies, idarucizumab was clearly more efficacious than strategies with non-specific procoagulant concentrates and devoid of the excessive procoagulant tendency observed with the latter.

Incremental effects of diabetes mellitus and chronic kidney disease in medial arterial calcification: Synergistic pathways for peripheral artery disease progression.

Diabetes mellitus (DM) and chronic kidney disease (CKD) separately are known to facilitate the progression of medial arterial calcification (MAC) in patients with symptomatic peripheral artery disease (PAD), but their combined effect on MAC and associated mediators of calcification is not well studied. The association of MAC and calcification inducer bone morphogenetic protein (BMP-2) and inhibitor fetuin-A, with PAD, is well known. Our aim was to investigate the association of MAC with alterations in BMP-2 and fetuin-A protein expression in patients with PAD with DM and/or CKD. Peripheral artery plaques (50) collected during directional atherectomy from symptomatic patients with PAD were evaluated, grouped into no-DM/no-CKD (n = 14), DM alone (n = 10), CKD alone (n = 12), and DM+CKD (n = 14). MAC density was evaluated using hematoxylin and eosin, and alizarin red stain. Analysis of inflammation, neovascularization, BMP-2 and fetuin-A protein density was performed by immunohistochemistry. MAC density, inflammation grade and neovessel content were significantly higher in DM+CKD versus no-DM/no-CKD and CKD (p < 0.01). BMP-2 protein density was significantly higher in DM+CKD versus all other groups (p < 0.01), whereas fetuin-A protein density was significantly lower in DM+CKD versus all other groups (p < 0.001). The combined presence of DM+CKD may be associated with MAC severity in PAD plaques more so than DM or CKD alone, as illustrated in this study, where levels of calcification mediators BMP-2 and fetuin-A protein were related most robustly to DM+CKD. Further understanding of mechanisms involved in mediating calcification and their association with DM and CKD may be useful in improving management and developing therapeutic interventions.

Rationale and Design of the EMPA-TROPISM Trial (ATRU-4): Are the "Cardiac Benefits" of Empagliflozin Independent of its Hypoglycemic Activity?

The SGLT2 inhibitor empagliflozin reduced cardiovascular mortality by 38% and heart failure (HF) hospitalizations by 35% in diabetic patients. We have recently demonstrated the efficacy of empagliflozin in ameliorating HF and improving cardiac function in a non-diabetic porcine model of HF mediated via a switch in myocardial metabolism that enhances cardiac energetics. Therefore, we hypothesized that the cardiac benefits of empagliflozin can also be extended to non-diabetic HF patients. The EMPA-TROPISM clinical trial is a randomized, double-blind, parallel group, placebo-controlled, trial comparing the efficacy of and safety of empagliflozin in non-diabetic HF patients. Eighty patients with stable HF for over 3 months, LVEF < 50%, and New York Heart Association functional class II to IV symptoms will be randomized to empagliflozin 10 mg for 6 months or placebo. All patients will undergo cardiac magnetic resonance (CMR), cardiopulmonary exercise test (CPET), 6-min walk test, and quality of life questionnaires. The primary outcome is the change in left ventricular end-diastolic volume measured by CMR. Secondary end-points include change in peak VO2 (CPET); change in LV mass, in LVEF, in myocardial mechanics (strains), in left atrium volumes, in RV function and volumes, in interstitial myocardial fibrosis, and in epicardial adipose tissue (CMR); change in the distance in the 6-min walk test; and changes in quality of life (Kansas Cardiomyopathy questionnaire [KCCQ-12] and the 36-Item Short Form Survey [SF-36]). Safety issues (e.g., hypoglycemia, urinary infections, ketoacidosis,…) will also be monitored. In summary, EMPA-TROPISM clinical trial will determine whether the SGLT2 inhibitor empagliflozin improves cardiac function and heart failure parameters in non-diabetic HF patients (EMPA-TROPISM [ATRU-4]: Are the "cardiac benefits" of Empagliflozin independent of its hypoglycemic activity; NCT 03485222).

Inhibition of Sodium Glucose Cotransporters Improves Cardiac Performance.

The sodium-glucose cotransporter (SGLT) inhibitors represent a new alternative for treating patients with diabetes mellitus. They act primarily by inhibiting glucose reabsorption in the renal tubule and therefore, decreasing blood glucose levels. While little is yet known about SGLT subtype 1, SGLT2 inhibitors have demonstrated to significantly reduce cardiovascular mortality and heart failure hospitalizations. This cardioprotective benefit seems to be independent of their glucose-lowering properties; however, the underlying mechanism(s) remains still unclear and numerous hypotheses have been postulated to date. Moreover, preclinical research has suggested an important role of SGLT1 receptors on myocardial ischemia. Following acute phase of cardiac injury there is an increased activity of SGLT1 cotransport that ensures adequate energy supply to the cardiac cells. Nonetheless, a long-term upregulation of this receptor may not be that beneficial and whether its inhibition is positive or not should be further addressed. This review aims to present the most cutting-edge insights into SGLT receptors.

Do the SGLT-2 Inhibitors Offer More than Hypoglycemic Activity?

Type 2 diabetes mellitus (T2DM) is one of the most common chronic health conditions in the USA; it affects approximately 10% of adults with up to one-quarter being undiagnosed. T2DM is associated with substantial cardiovascular (CV) morbidity and mortality. T2DM is a pathological condition characterized by elevated levels of glucose and associated with high CV risk. Traditional hypoglycemic drugs have demonstrated their capability for effective and maintained management of high glucose levels, but they have not significantly impacted on the incidence of CV events. Recently, a new class of hypoglycemic agents, SGLT-2 receptor inhibitors, has been developed. The EMPA-OUTCOME trial involving empagliflozin (a SGLT-2 receptor inhibitor) has shown significant reductions in major adverse cardiac events (MACEs), cardiovascular mortality, and hospitalization for heart failure (HF) when administered on top of standard-of-care therapy for T2DM patients at high CV risk. The dramatic change driving the superiority of the primary composite outcome (major adverse CV events) was a significantly lower CV death rate (38% relative risk reduction). In addition, there were also an impressive 35 and 32% relative risk reductions in hospitalization for heart failure (HF) and death from any cause, respectively. These effects are even more important given the difficulties for treating concomitant HF in T2DM patients. These surprising results have been also corroborated by another agent of this class, canagliflozin, and the CANVAS trial. The magnitude of these somehow surprising cardiac benefits attained in the absence of major differences in glycemic, lipid, or blood pressure (BP) control has led to several groups to suggest that these benefits may be independent of its hypoglycemic activity and whether this new class could be considered a "cardiac" drug. The objective of this review has been to review the different hypotheses proposed to explain the cardiac benefits of this new class of antidiabetic drugs.

Sphingosine-1-Phosphate Receptor Agonist Fingolimod Increases Myocardial Salvage and Decreases Adverse Postinfarction Left Ventricular Remodeling in a Porcine Model of Ischemia/Reperfusion.

BACKGROUND: Fingolimod, a sphingosine-1-phosphate receptor agonist, is used for the treatment of multiple sclerosis and exerts antiapoptotic properties. We hypothesized that sphingosine-1-phosphate receptor activation with fingolimod during acute myocardial infarction (MI) inhibits apoptosis, leading to increased myocardial salvage, reduced infarct size, and mitigated left ventricular (LV) remodeling in a porcine model of ischemia/reperfusion. METHODS AND RESULTS: Ischemia/reperfusion was induced in pigs by balloon occlusion of the left anterior descending artery, followed by reperfusion. Animals randomly received fingolimod or saline (control). In short-term experiments, fingolimod treatment activated the cardioprotective reperfusion injury salvage kinase and survivor activating factor enhancement pathways in the infarct border zone 24 hours after MI, leading to decreased cardiomyocyte apoptosis and reduced myocardial oxidative stress. These effects were abolished by specific inhibitors of both pathways, demonstrating that fingolimod-induced cardioprotection was mediated by reperfusion injury salvage kinase and survivor activating factor enhancement pathways. In long-term experiments, fingolimod significantly improved myocardial salvage, reduced infarct size, and improved systolic LV function measured by cardiac magnetic resonance 1 week and 1 month after MI. Importantly, fingolimod mitigated the development of adverse post-MI LV remodeling 1 month after MI. Specifically, fingolimod treatment led to a significant reduction in LV mass, LV dilatation, and neurohormonal activation, and it preserved LV geometry. Furthermore, fingolimod decreased interstitial fibrosis, cardiomyocyte hypertrophy, and chronic activation of Akt and extracellular receptor kinase 1/2 in the remote noninfarcted myocardium. CONCLUSIONS: Sphingosine-1-phosphate receptor activation with fingolimod during acute MI reduced infarct size via the reperfusion injury salvage kinase and survivor activating factor enhancement pathways, improved systolic LV function, and mitigated post-MI LV remodeling. Our data strongly support a cardioprotective role for sphingosine-1-phosphate receptor activation during MI.

Ticagrelor with aspirin or alone in high-risk patients after coronary intervention: Rationale and design of the TWILIGHT study.

BACKGROUND: Dual antiplatelet therapy (DAPT) is necessary to prevent thrombosis yet increases bleeding after percutaneous coronary intervention (PCI) with drug-eluting stents (DES). Antiplatelet monotherapy with a potent P2Y12 receptor antagonist may reduce bleeding while maintaining anti thrombotic efficacy compared with conventional DAPT. METHODS: TWILIGHT is a randomized, double-blind placebo-controlled trial evaluating the comparative efficacy and safety of antiplatelet monotherapy versus DAPT in up to 9000 high-risk patients undergoing PCI with DES. Upon enrollment after successful PCI, all patients will be treated with open label low-dose aspirin (81-100 mg daily) plus ticagrelor (90 mg twice daily) for 3 months. Event-free patients will then be randomized in a double-blind fashion to low-dose aspirin versus matching placebo with continuation of open-label ticagrelor for an additional 12 months. The primary hypothesis is that a strategy of ticagrelor monotherapy will be superior with respect to the primary endpoint of bleeding academic research consortium type 2, 3 or 5, while maintaining non-inferiority for ischemic events compared with ticagrelor plus ASA. CONCLUSIONS: TWILIGHT is the largest study to date that is specifically designed and powered to demonstrate reductions in bleeding with ticagrelor monotherapy versus ticagrelor plus ASA beyond 3 months post-procedure in a high-risk PCI population treated with DES. The trial will provide novel insights with respect to the potential role of ticagrelor monotherapy as an alternative for long-term platelet inhibition in a broad population of patients undergoing PCI with DES.

Alternatively spliced tissue factor promotes plaque angiogenesis through the activation of hypoxia-inducible factor-1α and vascular endothelial growth factor signaling.

BACKGROUND: Alternatively spliced tissue factor (asTF) is a novel isoform of full-length tissue factor, which exhibits angiogenic activity. Although asTF has been detected in human plaques, it is unknown whether its expression in atherosclerosis causes increased neovascularization and an advanced plaque phenotype. METHODS AND RESULTS: Carotid (n=10) and coronary (n=8) specimens from patients with stable or unstable angina were classified as complicated or uncomplicated on the basis of plaque morphology. Analysis of asTF expression and cell type-specific expression revealed a strong expression and colocalization of asTF with macrophages and neovessels within complicated, but not uncomplicated, human plaques. Our results showed that the angiogenic activity of asTF is mediated via hypoxia-inducible factor-1α upregulation through integrins and activation of phosphatidylinositol-3-kinase/Akt and mitogen-activated protein kinase pathways. Hypoxia-inducible factor-1α upregulation by asTF also was associated with increased vascular endothelial growth factor expression in primary human endothelial cells, and vascular endothelial growth factor-Trap significantly reduced the angiogenic effect of asTF in vivo. Furthermore, asTF gene transfer significantly increased neointima formation and neovascularization after carotid wire injury in ApoE(-/-) mice. CONCLUSIONS: The results of this study provide strong evidence that asTF promotes neointima formation and angiogenesis in an experimental model of accelerated atherosclerosis. Here, we demonstrate that the angiogenic effect of asTF is mediated via the activation of the hypoxia-inducible factor-1/vascular endothelial growth factor signaling. This mechanism may be relevant to neovascularization and the progression and associated complications of human atherosclerosis as suggested by the increased expression of asTF in complicated versus uncomplicated human carotid and coronary plaques.

Novel small leucine-rich repeat protein podocan is a negative regulator of migration and proliferation of smooth muscle cells, modulates neointima formation, and is expressed in human atheroma.

BACKGROUND: Smooth muscle cell (SMC) migration and proliferation critically influence the clinical course of vascular disease. We tested the effect of the novel small leucine-rich repeat protein podocan on SMC migration and proliferation using a podocan-deficient mouse in combination with a model of arterial injury and aortic explant SMC culture. In addition, we examined the effect of overexpression of the human form of podocan on human SMCs and tested for podocan expression in human atherosclerosis. In all these conditions, we concomitantly evaluated the Wnt-TCF (T-cell factor) pathway. METHODS AND RESULTS: Podocan was strongly and selectively expressed in arteries of wild-type mice after injury. Podocan-deficient mice showed increased arterial lesion formation compared with wild-type littermates in response to injury (P<0.05). Also, SMC proliferation was increased in arteries of podocan-deficient mice compared with wild-type (P<0.05). In vitro, migration and proliferation were increased in podocan-deficient SMCs and were normalized by transfection with the wild-type podocan gene (P<0.05). In addition, upregulation of the Wnt-TCF pathway was found in SMCs of podocan-deficient mice both in vitro and in vivo. On the other hand, podocan overexpression in human SMCs significantly reduced SMC migration and proliferation, inhibiting the Wnt-TCF pathway. Podocan and a Wnt-TCF pathway marker were differently expressed in human coronary restenotic versus primary lesions. CONCLUSIONS: Podocan appears to be a potent negative regulator of the migration and proliferation of both murine and human SMCs. The lack of podocan results in excessive arterial repair and prolonged SMC proliferation, which likely is mediated by the Wnt-TCF pathway.