Mechanical stretch regulates inflammatory signaling in human smooth muscle cells
Background and aimsVascular smooth muscle cells (SMCs) cultured under standard static conditions adopt a modulated phenotype that resembles the SMC states found in atherosclerotic plaques, but the mechanical determinants of this drift are not well defined. We investigated how mechanical loading shapes SMC phenotype and inflammatory signaling. MethodsHuman aortic SMCs were maintained under static conditions, physiological cyclic stretch (10% elongation), or pathological stretch (15% elongation) and analyzed by bulk and single-cell RNA sequencing. Mechanistic experiments included siRNA-mediated knockdown of IKBKB, p65 immunofluorescence, and regulon inference from single-cell transcriptomes. ResultsStretch regulated cell cycle, contractile, and inflammatory gene programs in an intensity-dependent manner: 10% stretch suppressed basal and TNF-induced inflammatory gene expression, whereas 15% stretch did not. The anti-inflammatory effect of physiological stretch required IKBKB, yet the proportion of cells with nuclear p65 was unchanged, indicating that stretch constrains NF-{kappa}B output downstream of p65 nuclear entry rather than by blocking translocation. Single-cell RNA sequencing resolved nine states for SMCs in culture whose transcriptomes overlapped substantially with the modulated mesenchymal populations of human coronary and carotid plaques, and physiological stretch attenuated pro-inflammatory gene expression across the major clusters. Regulatory network analysis identified inflammatory transcription factors (RELB, CEBPB/D, IRF1/2, STAT2) as less active under physiological stretch, whereas mechano-lineage regulators (MEF2C, TEAD1, SMAD6) were selectively induced, providing candidate mediators of the effect. ConclusionsStatic culture represents a disease-like SMC baseline that physiological stretch attenuates, in part by constraining NF-{kappa}B transcriptional output at a step downstream of p65 nuclear entry. Graphical abstractPhysiological stretch (10%) maintains a low-inflammatory, healthy-like state in human aortic smooth muscle cells, whereas its absence (static culture) or excess (15% stretch) favors an inflammatory, plaque-like state. NF-{kappa}B-p65 enters the nucleus under all conditions; physiological stretch constrains its inflammatory output downstream of nuclear entry. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/685276v2_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@bbcf58org.highwire.dtl.DTLVardef@29ba95org.highwire.dtl.DTLVardef@1989aa4org.highwire.dtl.DTLVardef@1d0c253_HPS_FORMAT_FIGEXP M_FIG C_FIG