Involvement of circulating endothelial progenitor cells in carotid plaque growth and vulnerability

Impact of distribution of carotid intraplaque neovessels on plaque vulnerability

BACKGROUND AND PURPOSE

Intraplaque neovessels (INVs) are considered important contributors to carotid plaque vulnerability. The purpose of this study was to examine whether differences in INV distribution affect plaque vulnerability.

METHODS

The study cohort comprised 110 patients with significant stenosis of the carotid artery who had undergone carotid endarterectomy. The distribution of INVs within carotid plaques was assessed by immunohistochemical studies using anti-CD-34 antibody as a marker for endothelial cells. First, we divided the patients into M group and S group depending on the numbers of INVs in middle and shoulder region. Next, we categorized carotid plaques into four categories according to the distributions of INVs: Shoulder, Middle, Mixed, and Scarce. We then compared total area of intraplaque hemorrhage, cholesterol, and calcification, width of thinnest fibrous cap, and number of INVs between the four categories of plaque.

RESULTS

The area of intraplaque hemorrhage was significantly larger in the M group than in the S group (P = 0.011). Meanwhile, symptomatic carotid stenosis was significantly more frequently associated with the Middle and Mixed than the Shoulder and Scarce categories (P < 0.01). The area of intraplaque hemorrhage was significantly different between the four groups (P = 0.022). Rupture of the fibrous cap was more frequently detected in the Middle and Mixed than the other categories (P = 0.002).

CONCLUSIONS

INVs in the middle region of carotid plaques are strongly associated with symptomatic carotid stenosis, intraplaque hemorrhage, and rupture of the fibrous cap. Our findings indicate that the distribution of INVs may affect plaque vulnerability.

Thin calcification (< 2 mm) can highly predict intraplaque hemorrhage in carotid plaque: the clinical significance of calcification types

PURPOSE

Calcification pathogenesis and the relationship between calcification and plaque composition remain unclear. This study explored the calcification characteristics of vulnerable plaques, especially focusing on calcification thickness, using computed tomography angiography and magnetic resonance plaque imaging.

METHODS

Demographic, computed tomography angiography, and magnetic resonance plaque imaging data were acquired from 178 patients with 229 lesions diagnosed with carotid stenosis. The calcification types were categorized by calcification thickness. We evaluated their features, including the anatomical location and the plaque composition compared with MR plaque imaging, and clarify the clinical characteristics. Furthermore, an immunohistochemical subgroup analysis was performed on 84 lesions treated with carotid endarterectomy.

RESULTS

The result of the ROC analysis suggested the threshold between symptomatic and asymptomatic calcification was 2.04 mm (AUC;0.841, 95%CI; 0.771-0.894). Calcification with ≥ 2 mm thickness was classified as thick calcification and < 2 mm thickness as thin calcification. Multivariate analysis suggested the prevalence of symptomatic patients in the thin calcification group was significantly higher than others (P = 0.01; odds ratio, 4.1; 95% confidence interval 2.8-7.2). Plaques with thin calcification were associated with plaque with intraplaque hemorrhage (P < 0.01). The interobserver reliability (κ) of calcification type was 0.962 (95% confidence interval, 0.941-0.988). Immunohistochemical analysis demonstrated that the numbers of CD68-positive cells and CD31-positive microvessels in shoulder lesions were significantly higher in the thin calcification group than in the non-thin group (both P < 0.01).

CONCLUSIONS

Thin calcification was associated with plaques with intraplaque hemorrhage and had different clinical implications than thick calcification.

Empagliflozin does not reverse lipotoxicity-induced impairment in human myeloid angiogenic cell bioenergetics

Background

Empagliflozin can curb inflammation and oxidative stress, through sodium-proton exchanger (NHE) inhibition, in a model of lipotoxicity in human myeloid angiogenic cells (MAC), which mediate endothelial repairing processes. Aim of this study is to assess in human MAC whether: (1) Stearic acid (SA) induced inflammation and increase in oxidant stress is accompanied by bioenergetic alterations; (2) empagliflozin anti-lipotoxic action is concomitant with coherent changes in bioenergetic metabolism, possibly via NHE blockade.

Methods

MAC were isolated from peripheral blood of healthy volunteers and incubated in the presence/absence of SA (100 μM for 3 h) with/without empagliflozin (EMPA 100 μM) or amiloride (Ami 100 μM) for 1 h. Cell respiration (oxygen consumption rate OCR) and anaerobic glycolysis (measured as proton production rate) were recorded in real-time by Seahorse technology, and ATP production (anaerobic glycolysis- and oxphos-derived) rates were calculated.

Results

SA, at the concentration causing inflammation and increased oxidant stress, altered cell bioenergetics of human MAC, with overall reductions in basal OCR and oxphos-derived ATP production (all p < 0.05), pointing to mitochondrial alterations. EMPA, at the concentration counteracting SA-induced lipotoxicity, both alone and in the presence of SA, caused NHE-independent extensive bioenergetic alterations (from p < 0.05 to p < 0.01), greater than those induced by SA alone.

Conclusions

In human MAC: (1) SA altered cell bioenergetics, concomitantly with inflammation and oxidant stress; (2) EMPA possibly inhibited mitochondrial respiration, (3) the protective effect of EMPA against SA-induced lipotoxicity was unlikely to be mediated through bioenergetic metabolism.

The Association of Nephroblastoma Overexpressed (NOV) and Endothelial Progenitor Cells with Oxidative Stress in Obstructive Sleep Apnea

Objective

Obstructive sleep apnea (OSA) is a sleep disorder characterized by intermittent hypoxia, chronic inflammation, and oxidative stress and is associated with cardiometabolic disease. Several biological substrates have been associated with OSA such as nephroblastoma overexpressed (NOV), endothelial progenitor cells (EPC), and circulating endothelial cells (CEC). Few studies have looked at the association of NOV with OSA while the EPC/CEC relationships with OSA are unclear. In this study, we hypothesize that (1) NOV is associated with the severity of OSA independent of BMI, identifying a protein that may play a role in the biogenesis of OSA complications, and (2) EPCs and CECs are also associated with the severity of OSA and are biomarkers of endothelial dysfunction in OSA.

Methods

61 subjects underwent overnight polysomnography (PSG), clinical evaluation, and blood analysis for NOV, EPC, CEC, interleukin 6 (IL-6), and other potential biomarkers.

Results

NOV and EPCs were independently associated with the oxygen desaturation index (ODI) after adjusting for potential confounders including body mass index (BMI), age, and sex (NOV p = 0.032; EPC p = 0.001). EPC was also independently associated with AHI after adjusting for BMI, age, and sex (p = 0.017). IL-6 was independently associated with AHI, but not with ODI.

Conclusion

NOV and EPC levels correlate with the degree of OSA independent of BMI, indicating that these biomarkers could potentially further elucidate the relationship between OSA patients and their risk of the subsequent development of cardiovascular disease.

Dilated microvessel with endothelial cell proliferation involves intraplaque hemorrhage in unstable carotid plaque

BACKGROUND

The purpose of the present study was to clarify the characteristics of endothelial cell (EC) proliferation in intraplaque microvessels in vulnerable plaques and impact on clinical results.

METHODS

The present study included 76 patients who underwent carotid endarterectomy. Patients were classified into three groups based on their symptoms: asymptomatic, symptomatic without recurrent ischemic event, and symptomatic with recurrent ischemic event. MR plaque imaging was performed and surgical specimens underwent immunohistochemical analysis. The number of CD31⁺ microvessels, and Ki67⁺ and CD105⁺ ECs in the carotid plaques was quantified, as measurements of maximum CD31⁺ microvessel diameter.

RESULTS

MR plaque imaging yielded 41 subjects (54.0%) diagnosed with plaque with intraplaque hemorrhage (IPH), 14 subjects (18.4%) diagnosed with fibrous plaques, and 21 (27.6%) subjects diagnosed with lipid-rich plaques. The average largest diameter of microvessel in fibrous plaques, lipid-rich plaques, and plaque with IPH was 12.7 ± 4.1 μm, 31.3 ± 9.3 μm, and 56.4 ± 10.0 μm, respectively (p < 0.01). Dilated microvessels (>40 μm) were observed in 9.6% of plaques with IPH but only in 2.8% of lipid-rich plaques and 0% of fibrous plaques (p < 0.01). Ki67⁺/CD31⁺ ECs were identified in 2.8 ± 1.2% of fibrous plaques, 9.6 ± 6.9% of lipid-rich plaques, and in 19.5 ± 5.9% of plaques with IPH (p < 0.01). The average largest diameter of microvessels in the asymptomatic group was 17.1 ± 8.7 μm, 32.3 ± 10.8 μm in the symptomatic without recurrence group, and 55.2 ± 13.2 μm in the symptomatic with recurrence group (p < 0.01).

CONCLUSION

Dilated microvessels with proliferative ECs may play a key role in IPH pathogenesis. Furthermore, dilated microvessels are likely related to clinical onset and the recurrence of ischemic events. The purpose of the present study was to clarify the characteristics of EC proliferation in intraplaque microvessels in vulnerable plaques and their impact on clinical results, focusing on dilated intraplaque microvessels.

Sodium-glucose cotransporter 2 inhibitors antagonize lipotoxicity in human myeloid angiogenic cells and ADP-dependent activation in human platelets: potential relevance to prevention of cardiovascular events

BACKGROUND

The clear evidence of cardiovascular benefits in cardiovascular outcome trials of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in type 2 diabetes might suggest an effect on atherosclerotic plaque vulnerability and/or thrombosis, in which myeloid angiogenic cells (MAC) and platelets (PLT) are implicated. We tested the effects of SGLT2i on inflammation and oxidant stress in a model of stearic acid (SA)-induced lipotoxicity in MAC and on PLT activation. The possible involvement of the Na⁺/H⁺ exchanger (NHE) was also explored.

METHOD

MAC and PLT were isolated from peripheral blood of healthy subjects and incubated with/without SGLT2i [empagliflozin (EMPA) and dapagliflozin (DAPA) 1-100 μM] to assess their effects on SA (100 μM)-induced readouts of inflammation, oxidant stress and apoptosis in MAC and on expression of PLT activation markers by flow-cytometry after ADP-stimulation. Potential NHE involvement was tested with amiloride (aspecific NHE inhibitor) or cariporide (NHE1 inhibitor). Differences among culture conditions were identified using one-way ANOVA or Friedman test.

RESULTS

NHE isoforms (1,5-9), but not SGLT2 expression, were expressed in MAC and PLT. EMPA and DAPA (100 μM) significantly reduced SA-induced inflammation (IL1β, TNFα, MCP1), oxidant stress (SOD2, TXN, HO1), but not apoptosis in MAC. EMPA and DAPA (both 1 μM) reduced PLT activation (CD62p and PAC1 expression). SGLT2i effects were mimicked by amiloride, and only partially by cariporide, in MAC, and by both inhibitors in PLT.

CONCLUSIONS

EMPA and DAPA ameliorated lipotoxic damage in stearate-treated MAC, and reduced ADP-stimulated PLT activation, potentially via NHE-inhibition, thereby pointing to plaque stabilization and/or thrombosis inhibition as potential mechanism(s) involved in SGLT2i-mediated cardiovascular protection.

Hypoxia accelerates intraplaque neovascularization derived from endothelial progenitor cells in carotid stenosis

OBJECTIVE

The relationship between intraplaque hypoxia and intraplaque hemorrhage (IPH) has been reported, but the details remain obscure. In this study, the authors aimed to clarify the relationship among intraplaque hypoxia, endothelial progenitor cells (EPCs), and neovascularization, which causes IPH. The histological findings of specimens obtained from carotid endarterectomy were assessed.

METHODS

This study included 49 patients who underwent carotid endarterectomy. Magnetic resonance plaque imaging was performed to analyze the components of the carotid plaques, and surgical specimens were subjected to immunohistochemical analysis. The numbers of hypoxia-inducible factor-1 alpha (HIF-1α)-, CD34-, CD133-, and vascular endothelial growth factor receptor-2 (VEGFR-2)-positive cells in the carotid plaques were precisely quantified, as were the number and maximum diameter of CD31-positive microvessels.

RESULTS

Plaque components were judged as fibrous in 7 samples, lipid-rich in 22, and IPH in 20. The number of CD34-, VEGFR-2-, and CD133-positive cells as an EPC-specific marker was significantly correlated with the number of HIF-1α-positive cells (r = 0.9, r = 0.82, and r = 0.81, respectively). These numbers varied among the 3 plaque components (IPH > lipid-rich > fibrous). The number and maximum luminal diameter of CD31-positive microvessels were also significantly correlated with the number of HIF-1α-positive cells (r = 0.85 and r = 0.89, respectively) and varied among the 3 plaque components (IPH > lipid-rich > fibrous).

CONCLUSIONS

The present findings suggest that intraplaque hypoxia may accelerate abnormal microvessel formation derived from EPCs, which in turn promotes IPH. The results also suggest that microvessel enlargement is a pivotal characteristic of IPH and these enlarged microvessels are immature endothelial tubes with disorganized branching and are fragile and prone to rupture.