C98-03 Cigarette Smoke-induced Endothelial Col4a1 Deficiency Impairs Sdc4 Signaling and Drives Satellite Cell Dysfunction for Sarcopenia in Chronic Obstructive Pulmonary Disease

Abstract Rationale Chronic obstructive pulmonary disease (COPD) is characterized by high morbidity and mortality, with limited effective therapies. Sarcopenia is an independent risk factor for poor prognosis in COPD, yet its molecular mechanisms remain poorly defined, particularly regarding how vascular endothelial injury disrupts skeletal muscle homeostasis. Existing studies have primarily focused on muscle atrophy, neglecting impaired regeneration. This study aimed to elucidate whether endothelial Col4a1 deficiency disrupts its interaction with muscle satellite cell (MuSC) receptor syndecan-4 (Sdc4), thereby mediating microenvironmental imbalance and driving MuSC dysfunction during smoke exposure-induced sarcopenia. Methods We analyzed skeletal muscle microstructure using immunofluorescence, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Tibialis anterior muscles from smoke-exposed and control mice underwent 10× single-cell RNA sequencing (scRNA-seq), followed by unsupervised clustering, marker gene identification, gene set variation analysis (GSVA), AUCell, and CellChat analysis to characterize intercellular communication. Col4a1 and Sdc4 expression and localization were verified by qPCR, Western blot, and immunohistochemistry in both mouse and human muscle tissues. Functional assays used siRNA knockdown of Col4a1, Sdc4-neutralizing antibody (5D10), and recombinant Col4a1 supplementation in endothelial-MuSC coculture and smoke-exposed mouse models. Results Smoke exposure disrupted extracellular matrix integrity and reduced basal lamina continuity, correlating with decreased muscle fiber cross-sectional area. Single-cell transcriptomics revealed MuSC dysfunction, with depletion of late-activated subsets, suppression of proliferative pathways (cell cycle, MYC targets), and upregulation of senescence markers (p16, SA-β-Gal). CellChat analysis identified collagen signaling as the most enhanced pathway after smoke exposure, while endothelial-MuSC Col4a1-Sdc4 interactions showed the greatest loss (↓∼50%, p 0.01). Col4a1 expression decreased by 60% (p 0.001) in skeletal muscle, accompanied by reduced Sdc4. Functionally, endothelial Col4a1 knockdown or smoke exposure impaired MuSC proliferation (↓KI67+) and differentiation (Myogenin+ cells 45%→12%, p 0.001). Conversely, Col4a1 overexpression or recombinant Col4a1 treatment restored MuSC differentiation, and intramuscular Col4a1 injection improved muscle atrophy by 40% and endurance to 85% of control levels (p 0.01). In COPD patients with sarcopenia, serum Col4a1 was reduced and positively correlated with handgrip strength and 6-minute walking distance. Conclusion This study identifies a previously unrecognized endothelial-muscle crosstalk mediated by the Col4a1/Sdc4 axis. Smoke-induced endothelial Col4a1 deficiency disrupts vascular-MuSC communication, leading to microenvironmental imbalance and impaired muscle regeneration. Targeting the Col4a1/Sdc4 pathway may represent a novel therapeutic strategy for preventing and treating sarcopenia in COPD. This abstract is funded by: None