Park Chanjae, Lee Moon Young, Park Paul J, Ha Se Eun, Berent Robyn M, Fuchs Robert, Miano Joseph M, Becker Laren S, Sanders Kenton M, Ro Seungil
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA.
Department of Physiology, Wonkwang Digestive Disease Research Institute and Institute of Wonkwang Medical Science, School of Medicine, Wonkwang University, Iksan, Jeollabuk-do, Korea.
J Neurogastroenterol Motil. 2015 Oct 1;21(4):589-602. doi: 10.5056/jnm15063.
BACKGROUND/AIMS: Smooth muscle cells (SMCs) characteristically express serum response factor (SRF), which regulates their development. The role of SRF in SMC plasticity in the pathophysiological conditions of gastrointestinal (GI) tract is less characterized.
We generated SMC-specific Srf knockout mice and characterized the prenatally lethal phenotype using ultrasound biomicroscopy and histological analysis. We used small bowel partial obstruction surgeries and primary cell culture using cell-specific enhanced green fluorescent protein (EGFP) mouse lines to study phenotypic and molecular changes of SMCs by immunofluorescence, Western blotting, and quantitative polymerase chain reaction. Finally we examined SRF change in human rectal prolapse tissue by immunofluorescence.
Congenital SMC-specific Srf knockout mice died before birth and displayed severe GI and cardiac defects. Partial obstruction resulted in an overall increase in SRF protein expression. However, individual SMCs appeared to gradually lose SRF in the hypertrophic muscle. Cells expressing low levels of SRF also expressed low levels of platelet-derived growth factor receptor alpha (PDGFRα(low)) and Ki67. SMCs grown in culture recaptured the phenotypic switch from differentiated SMCs to proliferative PDGFRα(low) cells. The immediate and dramatic reduction of Srf and Myh11 mRNA expression confirmed the phenotypic change. Human rectal prolapse tissue also demonstrated significant loss of SRF expression.
SRF expression in SMCs is essential for prenatal development of the GI tract and heart. Following partial obstruction, SMCs down-regulate SRF to transition into proliferative PDGFRα(low) cells that may represent a phenotype responsible for their plasticity. These findings demonstrate that SRF also plays a critical role in the remodeling process following GI injury.
背景/目的：平滑肌细胞（SMC）典型地表达血清反应因子（SRF），该因子调节其发育。SRF在胃肠道（GI）病理生理条件下SMC可塑性中的作用尚不明确。
我们构建了SMC特异性Srf基因敲除小鼠，并使用超声生物显微镜和组织学分析对产前致死表型进行了表征。我们采用小肠部分梗阻手术，并使用细胞特异性增强绿色荧光蛋白（EGFP）小鼠品系进行原代细胞培养，通过免疫荧光、蛋白质免疫印迹和定量聚合酶链反应研究SMC的表型和分子变化。最后，我们通过免疫荧光检测人直肠脱垂组织中SRF的变化。
先天性SMC特异性Srf基因敲除小鼠在出生前死亡，并表现出严重的胃肠道和心脏缺陷。部分梗阻导致SRF蛋白表达总体增加。然而，在肥厚的肌肉中，单个SMC似乎逐渐失去SRF。表达低水平SRF的细胞也表达低水平的血小板衍生生长因子受体α（PDGFRα(low)）和Ki67。在培养中生长的SMC重现了从分化的SMC向增殖性PDGFRα(low)细胞的表型转换。Srf和Myh11 mRNA表达的立即且显著降低证实了表型变化。人直肠脱垂组织也显示出SRF表达的显著丧失。
SMC中SRF的表达对于胃肠道和心脏的产前发育至关重要。部分梗阻后，SMC下调SRF以转变为增殖性PDGFRα(low)细胞，这些细胞可能代表了其可塑性的一种表型。这些发现表明，SRF在胃肠道损伤后的重塑过程中也起着关键作用。
