Extracellular Vesicle Dynamics Predicting Vascular Complications and Treatment Response in Systemic Sclerosis

Systemic sclerosis (SSc) is a multi-organ disease characterized by vascular, immune, and fibrotic changes. Vascular complications significantly contribute to mortality, disability, and healthcare costs in patients with SSc. These include digital ulcers (DUs) and associated conditions such as gangrene and osteomyelitis, as well as pulmonary arterial hypertension (PAH), all of which continue to have poor outcomes despite treatment advances. Notably, severe vascular disease increases the risk of cardiac and peripheral atherosclerosis, even in the absence of symptoms or overt risk factors. Timely management improves outcomes, but screening and prognostic stratification tools for SSc remain limited. Evidence supporting personalized treatment selection among currently available therapies is lacking.

Extracellular vesicles (EVs) are subcellular particles that facilitate the transfer of proteins, nucleic acids, and lipids between cells. They have been explored as biomarkers, therapeutic targets, and drug carriers across a wide range of diseases.

The investigators hypothesize that EVs play a direct and distinct role in the pathophysiology of multiorgan complications in SSc, particularly PAH and DUs. This hypothesis is supported by preclinical evidence demonstrating the involvement of EVs in endothelial dysfunction, intimal proliferation, immune dysregulation, and fibrosis, which are key processes in SSc pathogenesis. In mouse models, intravenously administered EVs are primarily taken up by the lungs, and PAH can be induced in healthy mice by injecting EVs isolated from pulmonary hypertensive animals. In humans, circulating EVs in the peripheral blood of patients with PAH are more abundant and exhibit distinct proteomic and transcriptomic profiles compared with those of healthy controls. Preliminary evidence further suggests that EV profiles in the venous blood of patients with SSc may correlate with disease severity and activity, although data specifically addressing vascular complications remain limited.

EVs exert biological effects through their protein, nucleic acid, and lipid cargo, as well as their ability to reach and interact with target cells. Recent studies in transgenic zebrafish have demonstrated that endogenous EVs can extravasate to distant target tissues in vivo. However, direct tracking of EVs in humans remains technically unfeasible with current methods. As a surrogate for in vivo tracking, the investigators propose characterizing circulating EVs at specific vascular locations accessible through acral vessels and during clinically indicated procedures such as right heart catheterization (RHC) and coronary angiography. These procedures, recommended for the assessment of PAH in patients with SSc, are consistent with international guidelines and pose no additional risk, making SSc an ideal model for investigating EV dynamics in humans.

This study aims to map EV characteristics across the circulatory system by evaluating changes at key anatomical sites. Sampling locations include the pulmonary artery and ascending aorta, reflecting pulmonary circulation and cardiac EV exchange, and the peripheral radial artery and cephalic vein, representing EV exchange within the acral circulation. EV profiles at these locations are expected to differ as a result of intravasation, extravasation, and collateral blood flow. Current approaches, which rely exclusively on peripheral venous sampling, lack this regional specificity and capture only the aggregate EV output.

The investigators further propose a comprehensive structural and functional evaluation of the cardiopulmonary and peripheral vascular systems to address the complex and heterogeneous nature of SSc complications. Pulmonary hypertension (PH) may arise from pulmonary vascular disease, including PAH or, less commonly, pulmonary veno-occlusive disease (group 1 PH); SSc-associated cardiac disease, including myocarditis, microvascular dysfunction, or accelerated coronary artery disease (group 2 PH); interstitial lung disease (group 3 PH); or, less frequently, chronic thromboembolic disease (group 4 PH). Similarly, DUs may result from microcirculatory failure or accelerated peripheral atherosclerotic disease. Defining the contribution of these overlapping mechanisms in individual patients is essential for interpreting and generalizing EV-related findings.

The unique characteristics of SSc among human diseases may provide broader insights into EV dynamics within the human circulatory system, potentially informing future research on other vascular and multiorgan diseases.

• Treatment failure in participants with pulmonary arterial hypertension. [Time frame: 24 weeks.]
• Treatment failure in participants with recurrent digital ulcers. [Time frame: 24 weeks.]