Faculty Bibliography

Cardiometabolic risk factors, obesity, diabetes and hyperlipidemia contribute to cardiovascular disease (CVD). While platelets are involved in CVD pathogenesis, the relationship between risk factor burden on platelet indices and the platelet transcriptome remains uncertain. Blood was collected from CVD-free adults, measuring platelet count, mean platelet volume (MPV), immature platelet fraction (IPF), and absolute immature platelet fraction (AIPF) by hemogram. Platelets were isolated and analyzed via RNA sequencing. Participants were stratified by number of cardiometabolic risk factors (diabetes, obesity, hyperlipidemia). We calculated median (IQR) values of platelet indices and p-for-trend via linear regression across risk factor burden. To evaluate the association between risk factor burden and platelet transcripts, we performed multivariable linear regression adjusting for age, sex, and race/ethnicity. Among 141 participants, (50.5 ± 14.8 years, 42% male, 26% Black) risk factor burden was associated with increasing platelet size, IPF, and AIPF but not platelet count. Platelet RNA sequencing identified 100 differentially expressed transcripts (p < .01; 66 upregulated, 34 downregulated). Gene ontology enrichment analysis demonstrated upregulated pathways of secondary metabolic processes (NES = 1.96, p < .01), and hematopoietic stem cell proliferation (NES = 1.95, p < .01). Greater cardiometabolic risk factor burden is associated with increased platelet size and immaturity and suggesting novel platelet-mediated mechanisms linking risk factor burden with CVD.

Insulin resistance impairs benefits of lipid-lowering treatment as evidenced by higher cardiovascular risk in individuals with type 2 diabetes versus those without. Because platelet activity is higher in insulin-resistant patients and promotes atherosclerosis progression, we questioned whether platelets impair inflammation resolution in plaques during lipid-lowering. In mice with obesity and insulin resistance, we induced advanced plaques, then implemented lipid-lowering to promote atherosclerotic plaque inflammation-resolution. Concurrently, mice were treated with either platelet-depleting or control antibodies for 3 weeks. Platelet activation and insulin resistance were unaffected by lipid-lowering. Both antibody-treated groups showed reduced plaque macrophages, but plaque cellular and structural composition differed. In platelet-depleted mice, scRNA seq revealed dampened inflammatory gene expression in plaque macrophages and an expansion of a subset of Fcgr4+ macrophages having features of inflammation-resolving, phagocytic cells. Necrotic core size was smaller and collagen content greater, resembling stable human plaques. Consistent with the mouse results, clinical data showed that patients with lower platelet counts had decreased pro-inflammatory signaling pathways in circulating non-classical monocytes after lipid-lowering. These findings highlight that platelets hinder inflammation-resolution in atherosclerosis during lipid-lowering treatment. Identifying novel platelet-targeted therapies following lipid-lowering treatment in individuals with insulin resistance may be a promising therapeutic approach to promote atherosclerotic plaque inflammation-resolution.

BACKGROUND:Abdominal computed tomography (CT) is commonly performed in adults. Abdominal aortic calcification (AAC) can be visualized and quantified using artificial intelligence (AI) on CTs performed for other clinical purposes (opportunistic CT). We sought to investigate the value of AI-enabled AAC quantification as a predictor of coronary artery disease and its association with cardiovascular events. METHODS:A fully automated AI algorithm to quantify AAC from the diaphragm to aortic bifurcation using the Agatston score was retrospectively applied to a cohort of patient that underwent both non-contrast abdominal CT for routine clinical care and cardiac CT for coronary artery calcification (CAC) assessment. Subjects were followed for a median of 36 months for major adverse cardiovascular events (MACE, composite of death, myocardial infarction [MI], ischemic stroke, coronary revascularization) and major coronary events (MCE, MI or coronary revascularization). RESULTS:Our cohort included 3599 patients (median age 60 years, 62% male, 74% white) with an evaluable abdominal and cardiac CT. There was a positive correlation between presence and severity of AAC and CAC (r=0.56, P<0.001). AAC showed excellent discriminatory power for detecting or ruling out any CAC (AUC for PREVENT risk score 0.701 [0.683 to 0.718]; AUC for PREVENT plus AAC 0.782 [0.767 to 0.797]; P<0.001). There were 324 MACE, of which 246 were MCE. Following adjustment for the 10-year cardiovascular disease PREVENT score, the presence of AAC was associated with a significant risk of MACE (adjHR 2.26, 95% CI 1.67-3.07, P<0.001) and MCE (adjHR 2.58, 95% CI 1.80-3.71, P<0.001). A doubling of the AAC score resulted in an 11% increase in the risk of MACE and a 13% increase in the risk of MCE. CONCLUSIONS:Using opportunistic abdominal CTs, assessment of AAC using a fully automated AI algorithm, predicted CAC and was independently associated with cardiovascular events. These data support the use of opportunistic imaging for cardiovascular risk assessment. Future studies should investigate whether opportunistic imaging can help guide appropriate cardiovascular prevention strategies.

BACKGROUND:Platelets are major players in the pathogenesis of cardiovascular events, and the number of circulating platelets in whole blood is routinely available in clinical testing. The relationship between the preoperative platelet count and major adverse cardiovascular events (MACE) after non-cardiac surgery is uncertain. METHODS:We identified adults age ≥18 years undergoing non-cardiac surgery from 2009 to 2015 from the National Surgical Quality Improvement Program. Pre-operative platelet counts within 90 days of surgery were recorded. Patients were prospectively followed for 30-days. The primary outcome was 30-day MACE (a composite of death, myocardial infarction [MI], or stroke). Multivariable logistic regression models estimated the association between platelet count and odds of postoperative outcomes. RESULTS:/L]). There was a U-shaped relationship between platelet count and MACE. The adjusted odds of MACE were elevated in mild(aOR 1.44, 95% CI 1.39-1.48) and moderate-severe thrombocytopenia (aOR 2.79, 95% CI 2.69-2.90), and in moderate (aOR 1.57, 95% CI 1.52-1.63) and severe (aOR 1.91, 95% CI 1.74-2.09) thrombocytosis. Findings were consistent for the individual endpoints of death, MI, and stroke. CONCLUSION/CONCLUSIONS:In adults undergoing non-cardiac surgery, pre-operative thrombocytopenia and thrombocytosis was identified in nearly 12% of cases and was associated with increased odds of cardiovascular events at 30 days.

AIM/OBJECTIVE:To investigate how psychosocial stress contributes to accelerated thrombosis, focusing on platelet activation and hyperreactivity. The specific objective was to identify novel platelet regulators involved in stress-mediated thrombosis, with a particular emphasis on the tetraspanin CD37. METHODS AND RESULTS/RESULTS:To explore how stress contributes to platelet hyperreactivity, platelets were isolated from (1) mice that experienced chronic variable stress and stress-free controls (n=8/group) and (2) human subjects with self-reported high and no stress levels (n=18/group), followed by RNA-sequencing. By comparing mutually expressed transcripts, a subset of genes differentially expressed following psychosocial stress was identified in both human and mouse platelets. In both mice and humans, platelet CD37 positively associates with platelet aggregation responses that underlie thrombosis, with Cd37-/- platelets exhibiting impaired integrin αIIbβ3 signaling, characterized by reduced platelet fibrinogen spreading and decreased agonist-induced αIIbβ3 activation. Consistent with a role for CD37 in regulating platelet activation responses, chimeric mice that received Cd37-/- bone marrow experienced a significantly increased time to vessel occlusion in the carotid artery FeCl3 model compared to mice reconstituted with wild-type bone marrow. CD37 deficiency did not alter hemostasis, as platelet count, coagulation metrics, prothrombin time, and partial thromboplastin time did not differ in Cd37-/- mice relative to wild-type mice. Consistent with this, bleeding time did not differ between wild-type and Cd37-/- mice following tail tip transection. CONCLUSIONS:This study provides new insights into the platelet-associated mechanisms underlying stress-mediated thrombosis. Identifying CD37 as a novel regulator of platelet activation responses offers potential therapeutic targets for reducing the thrombotic risk associated with psychosocial stress. The findings also contribute to understanding how psychosocial stress accelerates thrombotic events and underscore the importance of platelet activation in this process.

BACKGROUND:The BEST-CLI (Best Endovascular Versus Best Surgical Therapy in Patients With Critical Limb Ischemia) trial tested the optimal initial revascularization strategy in patients with chronic limb-threatening ischemia. Little is known about the prognostic relevance of Lp(a) (lipoprotein[a]) and its modification by renal function in patients with chronic limb-threatening ischemia. We investigated the relationship between Lp(a) and prespecified cardiovascular outcomes. METHODS:A subgroup of patients from the BEST-CLI trial (as part of the TIDE [The Impact of Diabetes on Revascularization] study) underwent blinded, core-laboratory assessment of Lp(a) levels and were included in this analysis. The primary end point was major adverse limb events or death from any cause. Secondary end points were the components of the primary end point, major amputation, major reintervention, and major adverse cardiac events (myocardial infarction, ischemic stroke, or death from any cause). The association of Lp(a) with end points was assessed using Cox proportional hazard models adjusting for traditional risk factors and then also for renal function and statin use, which increase Lp(a) levels. RESULTS:=0.009). Results were similar regardless of peripheral revascularization strategy. CONCLUSIONS:Elevated Lp(a) level was not associated with major adverse limb events or death but was associated with all-cause death after controlling for renal function. Lp(a) may be an important therapeutic target in the patient population with high-risk chronic limb-threatening ischemia. REGISTRATION/BACKGROUND:https://clinicaltrials.gov/study/NCT03085524; Unique identifier: NCT03085524.

BACKGROUND AND AIMS/OBJECTIVE:Low functional capacity is an independent risk factor for cardiovascular (CV) events. Regular physical activity may reduce CV risk through suppression of inflammation and reduced platelet activity. We aimed to investigate the association of functional capacity quantified by the validated Duke Activity Status Index (DASI) with platelet activity and incident major adverse CV and limb events (MACLE) in individuals with peripheral artery disease (PAD) undergoing lower extremity revascularization (LER). METHODS:Light transmission aggregometry and platelet RNAseq were performed on specimens isolated from men and women prior to LER. Functional capacity was assessed using DASI. Prospective follow-up occurred at 1, 6, 12, and every 6 months following the LER. Subjects were separated into tertiles of DASI scores and incidence rates for MACLE were calculated using log-rank tests. Mediation analysis using linear regression fit with least squares was performed to test whether DASI exerted its effect on MACLE via platelet aggregation. RESULTS:281 patients completed the DASI questionnaire with scores ranging from 0.0 to 50.2 (bottom tertile: 0.0-9.95). Mean age was 74.4 ± 10.9 years and 32.4 % were female. During a median follow-up of 19 months, 163 (58.0 %) participants experienced a MACLE. After correction for demographics and CV risk factors, individuals in the lowest DASI tertile experienced significantly more MACLE than participants in other tertiles. The association between DASI and MACLE was consistent across multiple subgroups stratified by age, sex, body mass index, antiplatelet therapy, and clinical comorbidities. Mediation analyses suggested higher platelet aggregation to epinephrine in the bottom DASI tertile mediated 24.7 % [5.0 %, 103 %] of increased MACLE risk. Platelet mRNA demonstrated upregulation of inflammation pathways in the most sedentary individuals (lowest DASI tertile). CONCLUSIONS:Patients with PAD and low functional capacity have increased platelet activity and high incidence of MACLE. Our data suggest that elevated platelet aggregation mediates one-quarter of the MACLE risk in persons with low functional capacity undergoing LER. Our findings support a potential platelet-mediated mechanism for improved CV outcomes associated with regular physical activity.

Patients with myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), are at increased risk of atherosclerosis, including peripheral arterial disease (PAD). Critical limb ischemia (CLI) may complicate PAD and is associated with significant mortality and morbidity. Despite the increased risk of thrombosis with MPN, outcomes of CLI in MPN patients are unclear. We conducted an analysis utilizing the 2017-2020 National Readmission Database (NRD) of patients hospitalized for CLI with and without MPN. Patients with MPN were propensity score matched (PSM) with patients without MPN. Primary outcome was composite outcome of major adverse cardiovascular and limb events (MACLE). Logistic regression was utilized to estimate risk of MACLE in patients with MPN vs. without MPN. Inverse-probability treatment weighted (IPTW) analysis was performed to evaluate the effect of revascularization on MACLE in patients with MPN. A total of 102,598 patients were included, 931 (0.9%) had MPN. After PSM, MPN was associated with increased risk of MACLE (47.3% vs. 39.1%; OR 1.40, 95% CI 1.21-1.62). After IPTW, revascularization was associated with decreased risk of MACLE among patients with MPN (45.0% vs. 50.7%; OR 0.80, 95% CI 0.66-0.96). Among patients admitted with CLI, MPN was associated with increased risk of MACLE especially ET and MF phenotypes. Revascularization was associated with decreased risk of MACLE among patients with MPN. Further investigation is needed in order to improve outcomes in patients with MPN and CLI.