Hinze, A M

Abstract Rationale Systemic sclerosis (SSc) is a rare, chronic autoimmune disease characterized by vasculopathy and fibrosis of the skin and internal organs. Among its manifestations, interstitial lung disease (ILD) is the leading cause of mortality, yet its clinical course is variable, ranging from stable to progressive pulmonary fibrosis (PPF). The 2022 ATS/ERS/JRS/ALAT guidelines defined progressive PPF as a phenotype of non- Idiopathic Pulmonary Fibrosis (IPF) - ILDs that behave similarly to IPF. Although a subset of SSc-ILD patients develop PPF, biomarkers predicting progression remain lacking. We and others have shown that endothelial dysfunction contributes to the progression of fibrotic lung disease, and that the pulmonary vasculature, continuously exposed to the bloodstream, is influenced by soluble circulating factors, including circulating extracellular vesicles (cEVs), which carry bioactive cargo capable of modulating endothelial behavior. Here, we investigated whether cEVs from SSc patients with distinct fibrotic phenotypes differentially influence human lung endothelial cells (ECs), promoting a pro-fibrotic endothelial phenotype. Methods plasma samples were collected from five groups: 1) Healthy controls (n = 4); 2) SSc-noILD (no high-resolution-CT (HCRT( or functional evidence of ILD at time of enrollment, n = 4); 3) SSc-ILD (HCRT and functional evidence of ILD without meeting the PPF criteria at time of sampling, n = 3); 4) SSc-PPF (meeting the PPF criteria, plasma collected prior to anti-fibrotic therapy, n = 4); 5) IPF (plasma collected prior to anti-fibrotic therapy, n = 3). cEVs were isolated using size-exclusion-chromatography and characterized using Nanoparticle Tracking Analysis (NTA). Human lung ECs were treated with cEVs from the five groups (2x109 particles/ml, 48 hours), followed by qPCR for markers selected for their established involvement in endothelial dysfunction during lung fibrotic progression. Results NTA showed no significant differences in plasma cEV concentrations across the five groups. Human lung ECs exposed to cEVs from SSc or SSc-ILD patients exhibited no significant gene expression changes compared to healthy controls. In contrast, cEVs from SSc-PPF patients markedly downregulated endothelial identity (PECAM1, ERG, TEK), barrier integrity (CDH13, S1PR1), and basement membrane (COL4A1, HSPG2) genes, similarly to changes induced by cEVs from IPF patients. Conclusion cEVs from SSc-PPF patients induce pro-fibrotic transcriptional changes in lung ECs resembling those induced by IPF cEVs and distinct from SSc-ILD cEVs, suggesting that EVs carry cargo that both reflect and influence fibrosis progression. These findings highlight the potential of cEVs as biomarkers for identifying SSC-ILD patients at risk of progression and highlight the clinical relevance of future studies aimed at characterizing their cargo. This abstract is funded by: James Depauw Grant for Pilot Projects

Abstract Rationale Interstitial lung disease (ILD) affects ∼50% of patients with systemic sclerosis (SSc) and is a leading cause of mortality. Visual assessment of ILD extent and morphologies, including ground-glass opacities (GGO) and reticular densities (RD), suffers from poor interobserver agreement, limiting prognostic consistency. CALIPER Quantitative CT (QCT) provides reproducible volumetric measures of parenchymal and vascular features. This study evaluated baseline QCT-derived lung features for association with transplant/mortality risk in SSc-ILD. Methods A retrospective cohort of SSc patients (≥18 years) seen at an academic center from 2007-2018 was identified using ICD codes, with ACR/EULAR 2013 SSc criteria confirmed by chart review. Inclusion required ILD on high-resolution CT (HRCT) ±2 years of SSc diagnosis, and PFTs ±6 months of HRCT. CALIPER quantified volumes of normal lung, GGO, RD, hyperlucency, honeycombing (HC), and pulmonary vascular-related structures (PVRS), which are expressed as percentages of total lung volume. Right heart catheterization confirmed pulmonary hypertension (PH) defined by 2022 ESC/ERS criteria (Eur Heart J, 2022). Cox hazards models assessed associations with combined mortality/transplant outcome, a priori adjusted for age, sex, diffuse SSc subtype, ILD duration, and PH (Column B), and further adjusted for baseline percent predicted FVC (ppFVC) and ppDLCO (Column C)(Table 1). Results Of 132 SSc-ILD patients, median SSc and ILD disease durations at HRCT were 1.4 (0.6, 2.4) and 0.0 (0.0, 0.5) years. Median feature percentages: total ILD 13.0% (IQR: 6.4, 21.0), GGO 10.2% (4.6, 16.9), RD 1.9% (0.8, 3.7), HC 0.03% (0.00, 0.09), PVRS 3.2% (2.3, 4.1). Median ppFVC was 81.1% (69.4, 92.6), and ppDLCO 60.0% (46.0, 75.7); 21 patients had PH. There were 2 transplants and 45 deaths. Every 5% increase in baseline total ILD and GGO associated with 22% (HR 1.22; 95% CI 1.12-1.33) and 24% (1.24; 1.12-1.36) higher risk of transplant/mortality on unadjusted models (Column A), respectively, remaining significant after a priori (CB) and full adjustment (CC)(Table 1). Every 1% increase in RD and PVRS conferred 19% (1.19; 1.08-1.31) and 33% (1.33; 1.08-1.63) higher risk of transplant/mortality in unadjusted models (CA); RD retained significance after a priori adjustment (1.17; 1.03-1.33), while PVRS trended non-significant in adjusted models. Conclusions In early SSc-ILD, QCT-derived GGO, RD, and PVRS provide robust prognostic value for mortality/transplant risk assessment, with small increases in baseline severity—at or below visual detection thresholds—associating with clinically meaningful risk increases. These findings support integrating baseline QCT biomarkers into risk stratification beyond clinical and PFT measures. This abstract is funded by: Rheumatology Research Foundation