Dasatinib induces endothelial dysfunction leading to impaired recovery from ischaemia.

Chronic myeloid leukaemia (CML) management is complicated by treatment-emergent vascular adverse events seen with tyrosine kinase inhibitors (TKIs) such as nilotinib, dasatinib and ponatinib. Pleural effusion and pulmonary arterial hypertension (PAH) have been associated with dasatinib treatment. Endothelial dysfunction and impaired angiogenesis are hallmarks of PAH. In this study, we explored, at cellular and whole animal levels, the connection between dasatinib exposure and disruption of endothelial barrier integrity and function, leading to impaired angiogenesis. Understanding the mechanisms whereby dasatinib initiates PAH will provide opportunities for intervention and prevention of such adverse effects, and for future development of safer TKIs, thereby improving CML management.

Thrombogenicity and endothelial progenitor cells function during Acute myocardial infarction - comparison of Prasugrel versus Ticagrelor.

BACKGROUND: Thrombin generation (TG), platelet function and circulating endothelial progenitor cells (EPCs) have an important role in the pathophysiology of coronary artery disease (CAD). To date, the effect of novel P2Y12 inhibitors on these aspects has mostly been studied in the sub-acute phase following myocardial infarction. OBJECTIVES: Comparing the effects of prasugrel and ticagrelor on TG and EPCs in the acute phase of ST-segment elevation myocardial infarction (STEMI). METHODS: STEMI patients were randomized to either ticagrelor or prasugrel treatment. TG, platelet reactivity and EPCs were evaluated prior to P2Y12 inhibitor loading dose (T0), and one day following (T1). RESULTS: Between December 2018 - July 2021, 83 consecutive STEMI patients were randomized to ticagrelor (N = 42) or prasugrel (N = 41) treatment. No differences were observed at T0 for all measurements. P2Y12 reactivity units (PRU) at T1 did not differ as well (prasugrel 13.2 [5.5-20.8] vs. ticagrelor 15.8 [4.0-26.3], p = 0.40). At T1, prasugrel was a significantly more potent TG inhibitor, with longer lag time to TG initiation (7.7 ± 7.5 vs. 3.9 ± 2.1 min, p < 0.01), longer time to peak (14.1 ± 12.6 vs. 8.3 ± 9.7 min, p = 0.03) and a lower endogenous thrombin potential (AUC 2186.1 ± 1123.1 vs. 3362.5 ± 2108.5 nM, p < 0.01). Furthermore, EPCs measured by percentage of cells expressing CD34 (2.6 ± 4.1 vs. 1.1 ± 1.1, p = 0.01) and CD133 (2.3 ± 1.8 vs. 1.4 ± 1.5, p = 0.01) and number of colony forming units (CFU, 2.1 ± 1.5 vs. 1.1 ± 1.0, p < 0.01) were significantly higher in the prasugrel group. CONCLUSION: Among STEMI patients, prasugrel as compared to ticagrelor was associated with more potent TG inhibition and improved EPCs count and function.

Impact of Calcium Channel Blockers on Aspirin Reactivity in Patients with Coronary Artery Disease.

PURPOSE: Calcium channel blockers (CCBs) do not reduce the risk of initial or recurrent myocardial infarction (MI) in patients diagnosed with stable coronary artery disease (CAD). The aim of this current study was to evaluate the association between CCBs and aspirin resistance in patients with CAD. METHODS: Patients with stable CAD who were regularly taking aspirin (75-100 mg qd) for at least 1 month prior to enrollment in the study were included. The VerifyNow system was used for platelet function testing with high on-aspirin platelet reactivity (HAPR) defined as aspirin reaction units (ARU) >550. We compared patients treated with CCBs versus control group. RESULTS: Five hundred three patients with CAD were included in this study, and 88 were treated with CCBs. Mean age (67.9±9.7 in the CCB group vs. 66.5±11.4 in the control group), gender (77.3 male vs. 82.9%), rates of diabetes mellitus (34.7 vs. 36.9%), rates of CKD (23.5 vs. 23.5%), dyslipidemia (85.1 vs. 85.3%), and statin therapy (89.5 vs. 90.7%) were similar. The mean ARU was 465.4±70.0 for patients treated with CCBs versus 445.2±60.0 in controls (p=0.006). Similarly, 15.9% of CCB patients demonstrated HAPR compared to 7.0% (p=0.006). The administration of CCBs was independently associated with HAPR in a multivariate analysis (OR 1.72, 95% CI: 1.04-8.91, p=0.047) as well as in propensity score matched analysis (OR 1.56; CI: 1.22-1.93; p<0.001). CONCLUSIONS: Usage of CCBs is positively correlated with aspirin resistance. These findings may suggest an adverse pharmacologic effect of CCBs among patients with stable CAD treated with aspirin.

The Effect of Proprotein Convertase Subtilisin Kexin Type 9 Inhibitors on Circulating Endothelial Progenitor Cells in Patients with Cardiovascular Disease.

PURPOSE: Circulating endothelial progenitor cells (cEPCs) are vital to vascular repair by re-endothelialization. We aimed to explore the effect of proprotein convertase subtilisin kexin type 9 inhibitors (PCSK9i) on cEPCs hypothesizing a possible pleiotropic effect. METHODS: Patients with cardiovascular disease (CVD) were sampled for cEPCs at baseline and following the initiation of PCSK9i. cEPCs were assessed using flow cytometry by the expression of CD34(+)/CD133(+) and vascular endothelial growth factor receptor (VEGFR)-2(+), and by the formation of colony-forming units (CFUs) and production of VEGF. RESULTS: Our cohort included 26 patients (median age 68 (IQR 63, 73) years; 69% male). Following 3 months of treatment with PCSK9i and a decline in low-density lipoprotein cholesterol levels (153 (IQR 116, 176) to 56 (IQR 28, 72) mg/dl), p < 0.001), there was an increase in CD34(+)/CD133(+) and VEGFR-2(+) cell levels (0.98% (IQR 0.37, 1.55) to 1.43% (IQR 0.90, 4.51), p = 0.002 and 0.66% (IQR 0.22, 0.99) to 1.53% (IQR 0.73, 2.70), p = 0.05, respectively). Functionally, increase in EPCs-CFUs was microscopically evident following treatment with PCSK9i (1 CFUs (IQR 0.0, 1.0) to 2.5 (IQR 1.5, 3), p < 0.001) with a concomitant increase in EPC's viability as demonstrated by an MTT assay (0.15 (IQR 0.11, 0.19) to 0.21 (IQR 0.18, 0.23), p < 0.001). VEGF levels increased following PCSK9i treatment (57 (IQR 18, 24) to 105 (IQR 43, 245), p = 0.006). CONCLUSIONS: Patients with CVD treated with PCSK9i demonstrate higher levels of active cEPCs, reflecting the promotion of endothelial repair. These findings may represent a novel mechanism of action of PCSK9i.

The Effect of Tafamidis on Circulating Endothelial Progenitor Cells in Patients with Transthyretin Cardiac Amyloidosis.

AIMS: Endothelial microvascular dysfunction is a known mechanism of vascular pathology in cardiac amyloidosis (CA). Scientific evidence regarding the possible protective role of the amyloid transthyretin (ATTR) stabilizer, tafamidis, is lacking. Circulating endothelial progenitor cells (cEPCs) have an important role in the process of vascular repair. We aimed to examine the effect of tafamidis on cEPCs. METHODS AND RESULTS: Study population included patients with ATTR-CA. cEPCs were assessed using flow cytometry by the expression of CD34(+)/CD133(+) and vascular endothelial growth factor receptor (VEGFR)-2(+) and by the formation of colony-forming units (CFUs) and production of VEGF. Tests were repeated at pre-specified time-points up to 12 months following the initiation of tafamidis. Included were 18 ATTR-CA patients at a median age of 77 (IQR 71, 85) years and male predominance (n = 15, 83%). Following the initiation of tafamidis and during 12 months of drug treatment, there was a gradual increase in the levels of CD34(+)/VEGFR-2(+) (0.43 to 2.42% (IQR 1.53, 2.91)%, p = 0.002) and CD133(+)/VEGFR-2(+) (0.49 to 1.64% (IQR 0.97, 2.90)%, p = 0.004). Functionally, increase in EPCs-CFUs was microscopically evident following treatment with tafamidis (from 0.5 CFUs (IQR 0.0, 1.0) to 3.0 (IQR 1.3, 3.8) p < 0.001) with a concomitant increase in EPC's viability as demonstrated by an MTT assay (from 0.12 (IQR 0.03, 0.16) to 0.30 (IQR 0.18, 0.33), p < 0.001). VEGF levels increased following treatment (from 54 (IQR 52, 72) to 107 (IQR 62, 129) pg/ml, p = 0.039). CONCLUSIONS: Tafamidis induced the activation of the cEPCs pathway, possibly promoting endothelial repair in ATTR-CA.

The Scattering of Gold Nanorods Combined with Differential Uptake, Paving a New Detection Method for Macrophage Subtypes Using Flow Cytometery.

The strategy of identification for M1 and M2 macrophages both in vivo and in vitro would help to predict the health condition of the individual. Here, we introduced a solution to this problem with the advantage of both the phagocytic nature of macrophages and the scattering effect of gold nanorods (GNRs). The internalized GNRs, relating to their extent of intake, caused a conspicuous scattering profile at the red channel in flow cytometry, overruling the contribution of the cellular side scatters. This internalization is solely governed by the surface chemistry of GNRs. The PAH-GNRs showed maximum intake potency followed by Cit-, PSS-, and PEG-GNRs. On a substantial note, PAH-GNRs lead to differential uptake between M1 and M2 cells, with three times higher intake in M2 cells over M1. This is the first report of employing the scattering of unlabeled GNRs to discriminate M1 and M2 cell types using a flow cytometer.

The effect of cessation of 2nd generation P2Y12 inhibitor therapy on platelet reactivity in patients 1 year after acute myocardial infarction.

To assess the effect of cessation of dual antiplatelet therapy (DAPT) regimens containing 2nd generation P2Y12 inhibitors on platelet reactivity, in patients who completed 12 months of DAPT following an acute myocardial infarction. Clinical data has shown an increased cardiovascular risk in the 90 days following cessation of DAPT. One possible explanation is a transient platelet hyper-reactivity after cessation of treatment. Data from patients treated with 2nd generation P2Y12 inhibitors is scarce. Patients who completed 12 month DAPT with prasugrel/ticagrelor underwent serial assessment of platelet reactivity (on DAPT and 1, 4 and 12 weeks post cessation). The primary outcome was platelet reactivity, expressed as platelet reactivity units (PRU) at each time point. 41 participants were included in this study, (23 ticagrelor, 18 prasugrel). There was no statistically significant differences in baseline characteristics between prasugrel/ticagrelor treated patients . The pattern of platelet reactivity recovery after DAPT cessation differed between the ticagrelor and prasugrel: with ticagrelor, after the initial PRU increase from baseline, the PRU remained stable, while with prasugrel, there was a further increase in PRU between 1 and 4 weeks, with a return to the 1 week level by 12 weeks (p = 0.034 for the time × treatment interaction between ticagrelor and prasugrel). Our results suggest there is a transient platelet hyper-reactivity after cessation of ADP receptor blockers therapy with prasugrel, but not ticagrelor. Further research is required to elucidate the pathophysiologic mechanisms behind these findings and to evaluate potential strategies to prevent or overcome this "rebound" effect.

The Effect of Mineralocorticoid Receptor Antagonists on Recruitment and Function of Endothelial Progenitor Cells in Patients with Congestive Heart Failure.

BACKGROUND: Circulating endothelial progenitor cells have an important role in the process of vascular repair. Impaired recruitment and function of endothelial progenitor cells is related to the pathophysiology of congestive heart failure. Endothelial progenitor cells have been shown to express the mineralocorticoid receptor. OBJECTIVES: To investigate the effect of mineralocorticoid receptor antagonists on endothelial progenitor cells in patients with heart failure. METHODS: Twenty-four patients with compensated heart failure, who were not under mineralocorticoid receptor antagonist therapy, were recruited. Either eplerenone (n=8) or spironolactone (n=16) therapy was initiated. Circulating endothelial progenitor cell level, identified as the proportion of mononuclear cells expressing vascular endothelial growth factor receptor 2 (VEGFR-2), CD133, and CD34, was evaluated by flow cytometry at baseline and after 8 weeks. Following 7 days of culture, colonies were counted by microscopy and MTT assay was performed on randomly selected patients (n=12) to estimate viability. RESULTS: Both median CD34+/VEGFR2+ and median CD133+/VEGFR2+ increased significantly (P = 0.04 and 0.02, respectively). However, the number of colonies and viability of the cells after therapy (as assessed by the MTT assay) was not significantly different compared with the baseline. CONCLUSIONS: These preliminary results suggest that mineralocorticoid receptor blockade may enhance endothelial progenitor cells recruitment in patients with compensated heart failure.

Characterization of surface antigens of reticulated immature platelets.

Reticulated platelets (RPs) are immature platelets with high dense granules content and a residual amount of megakaryocyte-derived of mRNA. Increased level of RPs has been found to be an independent predictor of cardiovascular ischemic events, and has been associated with impaired response to various anti-platelet drugs. The study aimed to characterize and compare the surface antigenic properties of reticulated versus mature platelets. Platelets from healthy individuals and diabetic patients were tested at rest and after activation with adenosine diphosphate (ADP). For each patient, we calculated the proportion of RPs and mature platelets using flow cytometry analysis with thiazole orange staining (for RPs) and CD42b platelet-specific antibody. We also tested the surface expression of P-selectin and Annexin V, by double staining flow cytometry in RPs versus mature platelets. A total of 20 subjects were recruited (10 healthy individuals, 10 diabetics). Activation with ADP did not cause a significant change in the proportion of RPs. Following activation, RPs demonstrated a significant increase in the expression of both P-selectin and Annexin V, while mature platelets exhibited a non-significant increase in both markers. These findings were consistent in both healthy subjects and patients with diabetes. In conclusion, RPs have a significantly higher capacity to increase the expression of platelet activation markers compared with mature platelets.

Circulating reticulated platelets over time in patients with myocardial infarction treated with prasugrel or ticagrelor.

Reticulated platelets (RP) are young, hyperactive platelets that are increased during situations of enhanced platelet turnover such as acute myocardial infarction (AMI). The dynamics of RP levels after AMI is not established. We aimed to characterize the levels of circulating RP over time in patients with AMI. Patients with AMI treated with ticagrelor or prasugrel who underwent percutaneous coronary intervention (PCI) were tested for circulating RP using flow cytometry with Thiazole orange staining at 3 time points at 2-4 days, 30-60 days and 1 year post PCI. Platelet reactivity was assessed using the VerifyNow P2Y12 assay at these time points (results in platelet reactivity units-PRU). Thirty-five patients were included in the study (mean age 62.6 ± 9.1 years, 82.9 % males). Median RP levels were similar at the first and second time points (17.5 %, IQR 25-75: 10.8-22.4 % and 14.9 %, IQR 25-75: 9.7-26.8 %, respectively; p = 0.75). However, RP levels after 1 year were significantly lower as compared to the first and second time points (10.5 % (IQR 25-75: 5.3-18.1 %), p = 0.005 and p = 0.01, respectively). Residual platelet reactivity was very low at all 3 time points (median PRU 25, IQR 25-75: 7-53) and did not change significantly between them (p = 0.66). No significant correlation was found between levels of RP and PRU at any given time point. RP levels of patients with AMI treated with prasugrel or ticagrelor decrease over time after the acute event. However, RP levels over time do not correlate well with residual platelet reactivity.

Relation between ticagrelor response and levels of circulating reticulated platelets in patients with non-ST elevation acute coronary syndromes.

Antiplatelet responses to clopidogrel and prasugrel are highly variable and subject to significant rates of high on-treatment platelet reactivity (HTPR) after percutaneous coronary intervention (PCI). The proportion of circulating young reticulated platelets (RPs) inversely correlates with responsiveness to both agents. We aimed to determine the relationship between RPs and on-treatment platelet reactivity in ticagrelor-treated patients. Patients with non-ST-elevation acute coronary syndromes (NSTE-ACS) treated with PCI and ticagrelor were tested for platelet reactivity using the VerifyNow P2Y12 assay and multiplate aggregometry. RPs levels were determined using flow cytometry with thiazole orange staining. Tests were performed at 2-4 and 30 days post-PCI. Fifty three patients were included (mean age 62.6 ± 9.8 years, 18.9 % women, 35.8 % diabetes), of which 41 patients (77 %) completed follow-up. Variability in response to ticagrelor was very low according to both assays with no identified cases of HTPR at either time-point. In addition, there were no differences in platelet reactivity, as analyzed by the VerifyNow P2Y12 assay, or in the proportion of RPs between the two time points (p > 0.5). With the multiplate assay, platelet reactivity increased between the two time-points (8.6 ± 6.0 vs. 15.5 ± 11 AU*min; p = 0.0007). There was no significant correlation between RPs and platelet reactivity at both time-points and using both assays (p > 0.5). There were no cases of HTPR up to 30-days post-PCI in patients with NSTE-ACS treated with ticagrelor. In this cohort, no correlation between % RPs and platelet reactivity was observed. Attenuation of RP-induced platelet reactivity as a novel mechanism for ticagrelor's benefit requires further investigation.

The effect of dabigatran and rivaroxaban on platelet reactivity and inflammatory markers.

The new oral anticoagulants (NOACs) reduce stroke and systemic embolism in patients with non-valvular atrial fibrillation (AF), but dabigatran may increase risk of coronary ischemic events for unclear reasons. Thus, this study assessed the effects of dabigatran and rivaroxaban on platelet reactivity and inflammatory markers in patients with non-valvular AF. Patients with non-valvular AF planned to begin treatment with NOACs were included. Seventeen patients were prescribed dabigatran and ten rivaroxaban. Platelet function (as assessed by multiple-electrode aggregometry, Impact-R shear-induced platelet deposition, P-selectin expression and plasma RANTES levels) and high-sensitivity C-reactive protein (hs-CRP) were measured at enrollment (prior to initiation of NOAC treatment) and at least 7 days into treatment with either dabigratran or rivaroxaban. Seventeen patients treated with dabigatran (mean age 69 ± 7 years, 35 % women, mean CHADS2 score 2.6 ± 1.2), and ten patients treated with rivaroxaban (mean age 73 ± 9 years, 20 % women, mean CHADS2 score 2.7 ± 1.6) completed the study. In both groups, there were no significant differences in platelet reactivity between the baseline and on-anticoagulant treatment time-points, as measured by each of the platelet-specific assays. There was a trend towards increased platelet reactivity in response to arachidonic acid from baseline to on-treatment in both groups, probably as a result of aspirin discontinuation in 33 % of patients. No significant differences were noted between baseline and on-treatment in hs-CRP in both anticoagulant groups. Treatment with dabigatran and rivaroxaban does not appear to be associated with changes in markers of platelet reactivity or systemic inflammation.

Gold nanorods as absorption contrast agents for the noninvasive detection of arterial vascular disorders based on diffusion reflection measurements.

In this study we report the use of gold nanorods (GNRs) as absorption contrast agents in the diffusion reflection (DR) method for the in vivo detection of atherosclerotic injury. The early detection and characterization of atherosclerotic vascular disease is considered to be one of the greatest medical challenges today. We show that macrophage cells, which are major components of unstable active atherosclerotic plaques, uptake gold nanoparticles, resulting in a change in the optical properties of tissue-like phantoms and a unique DR profile. In vivo DR measurements of rats that underwent injury of the carotid artery showed a clear difference between the DR profiles of the injured compared with healthy arteries. The results suggest that DR measurements following GNRs administration represent a potential novel method for the early detection of atherosclerotic vascular disease.

TGF-ß1 signaling and Krüppel-like factor 10 regulate bone marrow-derived proangiogenic cell differentiation, function, and neovascularization.

Emerging evidence demonstrates that proangiogenic cells (PACs) originate from the BM and are capable of being recruited to sites of ischemic injury where they contribute to neovascularization. We previously determined that among hematopoietic progenitor stem cells, common myeloid progenitors (CMPs) and granulocyte-macrophage progenitor cells (GMPs) differentiate into PACs and possess robust angiogenic activity under ischemic conditions. Herein, we report that a TGF-ß1-responsive Krüppel- like factor, KLF10, is strongly expressed in PACs derived from CMPs and GMPs, ∼ 60-fold higher than in progenitors lacking PAC markers. KLF10(-/-) mice present with marked defects in PAC differentiation, function, TGF-ß responsiveness, and impaired blood flow recovery after hindlimb ischemia, an effect rescued by wild-type PACs, but not KLF10(-/-) PACs. Overexpression studies revealed that KLF10 could rescue PAC formation from TGF-ß1(+/-) CMPs and GMPs. Mechanistically, KLF10 targets the VEGFR2 promoter in PACs which may underlie the observed effects. These findings may be clinically relevant because KLF10 expression was also found to be significantly reduced in PACs from patients with peripheral artery disease. Collectively, these observations identify TGF-ß1 signaling and KLF10 as key regulators of functional PACs derived from CMPs and GMPs and may provide a therapeutic target during cardiovascular ischemic states.

Elevated level of pro-inflammatory eicosanoids and EPC dysfunction in diabetic patients with cardiac ischemia.

BACKGROUND: Circulating endothelial progenitor cells (EPCs) are recruited from the blood system to sites of ischemia and endothelial damage, where they contribute to the repair and development of blood vessels. Since numerous eicosanoids including leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) have been shown to exert potent pro-inflammatory activities, we examined their levels in chronic diabetic patients with severe cardiac ischemia in conjunction with the level and function of EPCs. RESULTS: Lipidomic analysis revealed a diabetes-specific increase (p<0.05) in inflammatory and angiogenic eicosanoids including the 5-lipoxygenase-derived LTB (4.11±1.17 vs. 0.96±0.27 ng/ml), the lipoxygenase/CYP-derived 12-HETE (117.08±35.05 vs. 24.34±10.03 ng/ml), 12-HETrE (17.56±4.43 vs. 4.15±2.07 ng/ml), and the CYP-derived 20-HETE (0.32±0.04 vs. 0.06±0.05 ng/ml) the level of which correlated with BMI (p=0.0027). In contrast, levels of the CYP-derived EETs were not significantly (p=0.36) different between these two groups. EPC levels and their colony-forming units were lower (p<0.05) with a reduced viability in diabetic patients compared with non-diabetics. EPC function (colony-forming units (CFUs) and MTT assay) also negatively correlated with the circulating levels of HgA1C. CONCLUSION: This study demonstrates a close association between elevated levels of highly pro-inflammatory eicosonoids, diabetes and EPC dysfunction in patients with cardiac ischemia, indicating that chronic inflammation impact negatively on EPC function and angiogenic capacity in diabetes.

Simultaneous Noninvasive Detection and Therapy of Atherosclerosis Using HDL Coated Gold Nanorods.

Cardiovascular disease (CVD) is a major cause of death and disability worldwide. A real need exists in the development of new, improved therapeutic methods for treating CVD, while major advances in nanotechnology have opened new avenues in this field. In this paper, we report the use of gold nanoparticles (GNPs) coated with high-density lipoprotein (HDL) (GNP-HDL) for the simultaneous detection and therapy of unstable plaques. Based on the well-known HDL cardiovascular protection, by promoting the reverse cholesterol transport (RCT), injured rat carotids, as a model for unstable plaques, were injected with the GNP-HDL. Noninvasive detection of the plaques 24 h post the GNP injection was enabled using the diffusion reflection (DR) method, indicating that the GNP-HDL particles had accumulated in the injured site. Pathology and noninvasive CT measurements proved the recovery of the injured artery treated with the GNP-HDL. The DR of the GNP-HDL presented a simple and highly sensitive method at a low cost, resulting in simultaneous specific unstable plaque diagnosis and recovery.

Reticulated Platelets and Their Relationship with Endothelial Progenitor Cells during the Acute Phase of ST-Elevation Myocardial Infarction.

Introduction: Endothelial progenitor cells (EPC) and reticulated platelets (RP) have central roles in the thrombotic and angiogenetic interactions during ST-elevation myocardial infarction (STEMI). The EPC and RP response in patients with STEMI treated by primary percutaneous intervention (PPCI) has not yet been investigated. Methods: We assessed EPC quantification by the expression of CD133+ and CD34+, and EPC function by the capacity of the cells to form colony-forming units (CFU) and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) during the acute phase of STEMI. These measurements were correlated with RP at baseline and after 24 h following PPCI. Results: Our cohort included 89 consecutive STEMI-diagnosed patients enrolled between December 2018 and July 2021. At baseline, there was a strong positive correlation between reticulated platelet quantity and MTT levels (R = 0.766 and R2 = 0.586, p < 0.001), CD34+ levels (R = 0.602, and R2 = 0.362, p < 0.001); CD133+ levels (R = 0.666 and R2 = 0.443, p < 0.001) and CFU levels (R = 0.437, R2 = 0.191, p < 0.001). The multiple linear regression showed that levels of MTT (adjusted R2 = 0.793; p < 0.001), CD34+ and CD133+ (adjusted R2 = 0.654; p < 0.001 and adjusted R2 = 0.627; p < 0.001, respectively) had strong independent correlations with RP response. At 24 h after PPCI, the correlation between RP quantity and EPC markers was not significant, except for MTT levels (R = 0.465, R2 = 0.216, p < 0.001). Conclusions: In patients with STEMI, higher levels of RP at baseline are significantly correlated with a more potent EPC response. The translational significance of these findings needs further investigation.

Identification of protective biologic factors in patients with high cardiovascular risk, but normal coronary arteries (NormCorn).

BACKGROUND: Endothelial progenitor cells (EPCs) have an important role in repair following vascular injury. Telomere length has been shown to be correlated with genome stability and overall cell health. We hypothesized that both EPCs and telomere size are related to protective mechanisms against coronary artery disease. Our aim was to evaluate the level and function of circulating EPCs and telomere length in patients with multiple cardiovascular risk factors and anatomically normal coronary arteries vs. matched controls. METHODS: We included 24 patients, with coronary CTA demonstrating normal coronaries and a high risk of CAD of >10% by ASCVD risk estimator. Control groups included 17 patients with similar cardiovascular profiles but with established CAD and a group of 20 healthy volunteers. Circulating EPCs levels were assessed by flow cytometry for expression of vascular endothelial growth factor receptor 2, CD34 and CD133. The capacity of the cells to form colony forming units (CFUs) was quantified after 1 week of culture. Telomere length was determined by the southern blotting technique. RESULTS: Patients with high risk for CVD and normal coronaries had augmented EPCs function, compared with the CAD group (1.1 vs. 0.22 CFU/f; P = 0.04) and longer telomeres compared with the CAD group (10.7 kb vs. 2.8 kb P = 0.015). These patients displayed a similar profile to the healthy group. CONCLUSION: Patients with a high risk for CAD, but normal coronary arteries have EPCs function and telomere length which resemble healthy volunteers, and augmented compared with patients with established CAD, which could serve as a protective mechanism against atherosclerosis development in these high-risk patients.

Circulating endothelial progenitor cell levels and function in patients who experienced late coronary stent thrombosis.

AIMS: The pathogenesis of late coronary stent thrombosis may be related to impaired arterial healing. Endothelial progenitor cells (EPCs) have been shown to play an important role in repair and re-endothelialization following vascular injury. We hypothesized that patients who develop late stent thrombosis may have reduced or dysfunctional EPCs, and aimed to compare EPC level and function in patients who experienced stent thrombosis vs. matched controls. METHODS AND RESULTS: Patients who developed late (> 30 days) stent thrombosis within the past 3 years were compared with matched patients who underwent stenting and did not develop stent thrombosis. All patients had blood samples taken ≥ 3 months from the stent thrombosis or index procedure. The proportion of peripheral mononuclear cells (PMNCs) expressing vascular endothelial growth factor receptor 2 (VEGFR-2), CD133, and CD34 was evaluated by flow cytometry. Endothelial progenitor cell colony forming units (CFUs) were grown from PMNCs, characterized and counted following 7 days of culture. The two groups (n = 30 each) were well-matched (93.3% men, mean age 60-62 years, 33.3% diabetes, 73-80% DESs). The proportion of cells co-expressing VEGFR-2, CD133, and CD34 was lower in the stent thrombosis group compared with the control [VEGFR-2(+)CD133(+): 0.18% (0.03-0.41%) vs. 0.47% (0.16-0.66%), P = 0.01; VEGFR-2(+)CD34(+): 0.32% (0.22-0.70%) vs. 0.66% (0.24-1.1%), P = 0.03]. The number of EPC CFUs was also lower in the stent thrombosis group [3.9% (3.2-5.5%) vs. 8.3% (6.5-13.4%) colonies/well, respectively, P < 0.0001]. CONCLUSION: Patients who suffered late coronary stent thrombosis appear to have reduced levels of circulating EPCs and impaired functional properties of the cells. These findings require validation by further studies, but may contribute to understanding the pathogenesis of late stent thrombosis.

Generation of vascular chimerism within donor organs.

Whole organ perfusion decellularization has been proposed as a promising method to generate non-immunogenic organs from allogeneic and xenogeneic donors. However, the ability to recellularize organ scaffolds with multiple patient-specific cells in a spatially controlled manner remains challenging. Here, we propose that replacing donor endothelial cells alone, while keeping the rest of the organ viable and functional, is more technically feasible, and may offer a significant shortcut in the efforts to engineer transplantable organs. Vascular decellularization was achieved ex vivo, under controlled machine perfusion conditions, in various rat and porcine organs, including the kidneys, liver, lungs, heart, aorta, hind limbs, and pancreas. In addition, vascular decellularization of selected organs was performed in situ, within the donor body, achieving better control over the perfusion process. Human placenta-derived endothelial progenitor cells (EPCs) were used as immunologically-acceptable human cells to repopulate the luminal surface of de-endothelialized aorta (in vitro), kidneys, lungs and hind limbs (ex vivo). This study provides evidence that artificially generating vascular chimerism is feasible and could potentially pave the way for crossing the immunological barrier to xenotransplantation, as well as reducing the immunological burden of allogeneic grafts.