Inflammation causes proliferation of intestinal smooth muscle cells (ISMC), which contributes to a thickened intestinal wall, and also to stricture formation in Crohn's disease. Proliferation of ISMC both in vitro and in vivo caused decreased expression of marker proteins, but the underlying cause is unclear. Since epigenetic change is important in other systems, we examined this in cell lines from rat colon at either low passage or after extended growth, using immunocytochemistry, immunoblotting and qPCR to evaluate phenotype. Exposure to the HDAC inhibitor trichostatin A or 5-azacytidine, a DNMT inhibitor, reversed the characteristic loss of phenotypic markers among high passage cell lines of ISMC. Expression of smooth muscle actin and SM-22 were markedly increased, as well as functional expression of the neurotrophin GDNF. Increased expression of muscarinic receptor-3 and MLCK was correlated with an upregulated response to cholinergic stimulation. In human ISMC (hISMC) lines from terminal ileum, phenotype was similarly affected by extended proliferation. However, hISMC from resected Crohn's strictures at low passage already displayed a significantly reduced contractile phenotype, compared with patient-matched intrinsic controls, and was associated with increased, patient-specific expression of DNMT1, HDAC2, and HDAC5. Therefore, protracted growth causes epigenetic alterations that account for an altered phenotype of ISMC. A similar process may promote stricture formation in Crohn's disease, where the potential for halting progression or even reversal of disease through control of phenotypic modulation may become a novel treatment option.

No abstract

This study reports a new methodology for right heart imaging by ultrasound in mice under right ventricular (RV) pressure overload. Pulmonary artery constriction (PAC) or sham surgeries were performed on C57BL/6 male mice at 8 weeks of age. Ultrasound imaging was conducted at 2, 4 and 8 weeks post-surgery using both classical and advanced ultrasound imaging modalities including ECG-based kilohertz visualization, anatomical M-mode and strain imaging. Based on pulsed Doppler, the PAC group demonstrated dramatically enhanced pressure gradient in the main pulmonary artery (MPA) as compared to the sham group. By applying advanced imaging modalities in novel short axis views of the ventricles, the PAC group demonstrated increased thickness of RV free wall, enlarged RV chamber and reduced RV fractional shortening compared to the sham group. The PAC group also showed prolonged RV contraction, asynchronous inter-play between RV and left ventricle (LV), and passive leftward motion of the inter-ventricular septum (IVS) at early diastole. Consequently, the PAC group exhibited prolongation of LV isovolumic relaxation time, without change in LV wall thickness or systolic function. Significant correlations were found between the maximal pressure gradient in MPA measured by Doppler and the RV systolic pressure by catheterization, as well as the morphological and functional parameters of RV by ultrasound.