Abstract Background Right ventricular (RV) function is the key determinant of survival in pulmonary hypertension (PH), yet RV immunobiology is incompletely defined. Left-ventricular (LV) injury studies implicate CCR2+ macrophages in monocyte recruitment and remodeling, but whether RV macrophages deploy similar or distinct programs is unknown. We hypothesized that under uniform hypoxia, RV, septum and LV mount different macrophage stress responses. Methods C57BL/6 mice were exposed to hypobaric hypoxia (18,000 ft) for 3, 7, or 21 days (n = 4/timepoint, balanced by sex). RV, septum and LV were dissected, enzymatically digested, and viable cells isolated by flow cytometry. Fixed cells underwent 10x Genomics Chromium Fixed RNA Profiling. Data were integrated and clustered (Seurat); macrophage subtypes were identified by canonical markers. Cluster-level differential expression (MAST hurdle), RV-LV contrasts across time, GO-based GSEA, and ligand-receptor analyses quantified transcriptional programs and intercellular communication. Results Despite uniform hypoxia, RV, septal and LV macrophages diverged in a time-dependent manner. At 3 days, RV macrophages upregulated interferon and chemokine modules (Ifit1/2/3, Isg15, Rsad2, Irf7; Ccl2/Ccl7), antigen-processing nodes (Tap1, Cd274), and a CCR2 recruitment signature, while LV induction was muted. At 7 days, RV retained interferon tone and expanded antigen presentation/immune interaction pathways (Ciita, H2-DMa/b1, Ctss) with early matrix engagement (Fn1, Tgfbi); LV remained comparatively homeostatic. At 21 days, RV transitioned to ECM/integrin programs (Fn1, Col1a1/2, Postn, Ltbp2/3), coincident with stronger RV macrophage-to-fibroblast/endothelial communication; LV networks remained attenuated. Collectively, RV responses reflect combined pressure/afterload and oxidative stress, driving CCR2-mediated recruitment and matrix remodeling, whereas LV showed a different, relatively homeostatic hypoxic response. Conclusions These findings demonstrate that under uniform hypoxia, RV macrophages mount a distinct immune-metabolic response driven by biomechanical and oxidative stress, in contrast to the relatively quiescent LV. RV-specific macrophage activation emerges as a key determinant of ventricular remodeling and a potential therapeutic target in pulmonary hypertension. This abstract is funded by: Janssen Pharmaceutical Companies of Johnson and Johnson Early Career Investigator Award in Pulmonary Vascular Disease Program
Gu et al. (Fri,) studied this question.