# The Role of Macrophage Dynamics in Atherosclerosis Analyzed Using a Petri Net-Based Model
###### Abstract  
Atherosclerosis, a chronic inflammatory and oxidative stress-mediated disease impacting the arterial system, stands as a primary cause of morbidity and mortality worldwide. The complexity of this disease, driven by numerous factors, requires a thorough investigation of its underlying mechanisms. In our study, we explore the complex interplay between cholesterol homeostasis, macrophage dynamics, and atherosclerosis development using a Petri net-based model anchored in credible, peer-reviewed biological and medical research. Our findings underscore the significant role of macrophage colony-stimulating factor (M-CSF) inhibition in reducing atherosclerotic plaque formation by modulating inflammatory responses and lipid accumulation. Furthermore, our model highlights the therapeutic potential of targeting the C-X-C motif ligand 12 (CXCL12)/C-X-C motif chemokine receptor type 4 (CXCR4) pathway to hinder hematopoietic stem and progenitor cells' (HSPCs') mobilization and plaque development. Based on the results obtained, which are in agreement with current studies, additional strategies are also proposed, such as decreasing M1 macrophage polarization for therapeutic gains, opening the door to future research and novel treatment approaches. m acrophage; atherosclerosis; mathematical modeling; Petri nets; knockout analysis +
Footnote †: journal: Medical Sciences  
0000-0001-999-7880][PERSON]; [PERSON] [PERSON]. Adherent monocytes and infiltrating monocyte-derived macrophages locally release many cytokines, matrix metalloproteinases, and vasoactive and growth factors to promote vascular and tissue remodeling or lead to inflammatory response propagation [5]. They are highly plastic and dynamic; once activated, their morphology and protein expression can change rapidly, producing markers specific to various cells [6]. Within atherosclerotic plaque, macrophages can switch between pro-inflammatory and anti-inflammatory states. However, they can also reveal heterogeneous phenotypes \"in-between\" and even \"out-of-the spectrum\", depending on the local microenvironment, which increases the complexity of the studied phenomenon [6]. Macrophages' functioning is complex and goes beyond phagocytosis and participation in lipid uptake [3,7] through macrophage-expressed scavenger receptors, but also involves the activation of immune responses and distinct and non-redundant roles in fibrosis, regeneration, and tissue repair and surveillance, highlighting their essential role in atherosclerosis [8, 9, 10, 11]. Due to the complex nature of atherosclerosis, there is currently no single marker known that would allow for a clear assessment of its severity or the prediction of cardiovascular risk [12]. Therefore, much research is carried out to indicate the most important pathways involved, allowing for a better understanding of the process and, consequently, more effective treatment. As far as we know, no prior research has combined such a wide range of signaling pathways and fundamental processes related to human cholesterol balance, macrophage behavior, and the mechanisms underlying atherosclerosis within a single study. This approach, enabled by the Petri net theory, allows for the development of molecular interaction networks without requiring precise quantitative parameters. This sets it apart from approaches that rely on ordinary differential equations (ODEs) or partial differential equations (PDEs), which require specific parameter values to represent the quantitative aspects of the system accurately. The lack of reliable quantitative reaction data often presents challenges when creating ODE/PDE models, especially for complex biological systems. Numerous mathematical models exist that illustrate the inflammatory response of macrophages, primarily in the early stages of plaque formation [13, 14, 15, 16, 17, 18, 19, 20, 21, 22].