Each year 3 to 4 million women and men with signs/symptoms suggestive of myocardial ischemia have no obstructive ischemic heart disease (IHD). Although the same number of women and men die annually from cardiovascular disease, women are more likely to have no obstructive IHD compared to men. The mechanisms underlying this pathological state are not known and treatment guidelines are missing. Our hypothesis is that in patients with no obstructive IHD, platelets are hyperactive and promote a pro-inflammatory state in which dysfunctional recruitment and activation of leukocytes lead to coronary microvascular dysfunction and ultimately to no obstructive IHD. The objective of the study is to understand how platelet and immune dysfunctions determine no obstructive IHD and whether sex differences in platelet reactivity and immunity explain why women are more likely to have this form of ischemia compared to men. To achieve this objective we propose three tasks to be pursued by a coordinated effort of three research units. The Unit of V. Raparelli will be in charge of patient evaluation and recruitment and sample collection (task 1). The samples will be collected from adults included in the Endocrine Vascular disease Approach (EVA) project (ClinicalTrials.gov identifier NCT02737982), an observational cohort prospective study currently in recruiting phase. The Unit of L. Stefanini will employ time-resolved flow cytometry to investigate whether platelets circulate in a pre-activated and pro-inflammatory state in patients with no obstructive IHD (task 2). The Unit of S. Piconese will perform immunological profiling of patients with multiparameter flow cytometry-based techniques (task 3). In summary, the proposed project will employ state-of-the-art flow cytometry techniques to dissect the mechanisms underlying no obstructive IHD, an emerging clinical issue especially for women. We anticipate that these studies will facilitate the tailoring of safer sex-specific therapies.
An increasing number of patients with evidence of ischemia but no obstructive coronary artery disease at coronary angiography are being recognised. Although these patients were previously thought to be at low risk for major adverse cardiovascular events (MACE) and were provided only reassurance, newer data document that these patients are a heterogeneous population with an elevated MACE risk. Thus there is an urgent need to address several important knowledge gaps to improve the diagnosis and the management of these patients.
The work laid out in this proposal will advance our knowledge and the management of no obstructive IHD in 3 ways:
First of all it will provide insight into the mechanisms underlying no obstructive IHD. Identification of parameters of platelet and/or leukocyte dysfunction that are associated with increased risk of no obstructive IHD, will enable the development of easily accessible tools for human phenotyping to classify patients into discrete disease endotypes, improve diagnosis and facilitate the tailoring of a personalized therapy.
Secondly, this study will try to fill the gap of knowledge between the sexes on the pathogenesis of IHD. Ischemic heart disease is the main cause of death among women and men. Nonetheless, IHD has been perceived as a primarily male disease, and evidence-based clinical standards have been based on male pathophysiology and outcomes in basic and clinical research. The low participation of women in clinical trials for CVD is cause of concern, especially in IHD patients. In fact, despite the decrease in CVD mortality over the past decade, trends are less favorable in women. Women with symptoms and signs of myocardial ischemia are more likely to have no obstructive IHD than men. This study will determine whether sex differences in the platelet pro-inflammatory state, leukocyte function and cytokine abundance explain the higher incidence of no obstructive IHD in women, an understudied population in cardiovascular research.
Last but not least, we anticipate that understanding the mechanistic interplay between platelets and the immune system will aid in the identification of new and potentially safer therapeutic strategies. Since anti-platelet therapy not only reduces the thrombo-ischemic risk but also decreases ongoing platelet-driven systemic inflammation, prolonged intensified anti-platelet therapy may also lower the risk of no obstructive IHD. However, targeting molecules implicated in the overall platelet activation, such as P2Y12, may protect from IHD at the cost of enhanced bleeding complications. Each of the molecular determinants of platelet-leukocyte cross-talk is a potential target for novel pharmacological agents. Thus, a more detailed understanding of the interplay between platelets and the immune system in the context of IHD may help identify new targets that would interfere with platelet-driven inflammation while preserving hemostasis.
This project is novel at various levels. First, it focuses on no obstructive IHD, an emerging clinical issue that has been recognised only recently.
Furthermore, the knowledge advancements ensured by this project will enable the implementation of precision medicine, in particular for women. Precision Medicine refers to the tailoring of medical treatment to the individual characteristics of each patient. It is based on the ability to classify individuals into subpopulations that differ in their susceptibility to a particular disease, in the biology and/or prognosis of the diseases they may develop, or in their response to a specific treatment. Preventive or therapeutic interventions can then be concentrated on those who will benefit, sparing expense and side effects for those who will not. The implementation of Precision Medicine is extremely important in the field of cardiovascular disease. To identify new preventive strategies of adverse outcome and innovative therapeutic targets, we need to know more about the pathogenesis of obstructive vs no obstructive IHD in females and males.
The proposed project will tackle this important medical issue by employing state-of-the-art flow cytometry techniques. Platelet studies in clinical settings, in particular when patients are in critical conditions, are limited by the volume of blood available. Multiparameter flow cytometry-based techniques will give us the opportunity to obtain large of amount of data i.e. platelet surface markers expression, immune cell subtypes frequencies and platelet-leukocyte interactions, from very small samples. Moreover, in this project we will employ time-resolved flow cytometry, an assay that was recently established by Professor Stefanini (Stefanini, JCI 2015) by exploiting the unique features of the BD Accuri C6 Plus flow cytometer. This innovative technique not only measures simultaneously different markers of platelet activation but also determines their kinetics, thus providing insight on the underlying molecular mechanisms.