Rapid cyclic stretching of cultured human visceral smooth muscle cells promotes a synthetic, proinflammatory phenotype

Bowel smooth muscle experiences mechanical stress constantly during normal function and pathologic mechanical stressors in disease states. We tested the hypothesis that pathologic mechanical stress could alter transcription to induce smooth muscle phenotypic class switching. To test this hypothesis, primary human intestinal smooth muscle cells (HISMCs), seeded on electrospun aligned poly-ε-caprolactone nano-fibrous scaffolds, were subjected to pathologic, high-frequency (1 Hz) uniaxial 3% cyclic stretch (loaded) or kept unloaded in culture for 6 hours. RNA-Seq, quantitative PCR (qPCR), and quantitative IHC defined loading-induced changes in gene expression. NicheNet predicted how differentially expressed genes might affect HISMCs and other bowel cells. These studies show loading induced differential expression of 4,537 HISMC genes. Loaded HISMCs had a less contractile phenotype, with increased expression of synthetic SMC genes, proinflammatory cytokines, and altered expression of axon guidance molecules, growth factors, and morphogens. Many differentially expressed genes encode secreted ligands that could act cell autonomously on smooth muscle and on other cells in the bowel wall. These data show that HISMCs undergo remarkably rapid phenotypic plasticity in response to mechanical stress that may convert contractile HISMCs into proliferative fibroblast-like cells or proinflammatory cells. These mechanical stress-induced changes in HISMC gene expression may be relevant for human bowel disease.