Angelini Aude, Li Zhenlin, Mericskay Mathias, Decaux Jean-François
Biology of Adaptation and Ageing, Institut de Biologie Paris Seine (IBPS), DHU FAST Sorbonne Universités, UPMC Université Paris 06, Paris, France; CNRS, UMR8256, Paris, France; INSERM, U1164, Paris, France.
PLoS One. 2015 Oct 6;10(10):e0139858. doi: 10.1371/journal.pone.0139858. eCollection 2015.
Myocardial fibrosis contributes to the remodeling of heart and the loss of cardiac function leading to heart failure. SRF is a transcription factor implicated in the regulation of a large variety of genes involved in cardiac structure and function. To investigate the impact of an SRF overexpression in heart, we developed a new cardiac-specific and tamoxifen-inducible SRF overexpression mouse model by the Cre/loxP strategy. Here, we report that a high level overexpression of SRF leads to severe modifications of cardiac cytoarchitecture affecting the balance between cardiomyocytes and cardiac fibroblasts and also a profound alteration of cardiac gene expression program. The drastic development of fibrosis was characterized by intense sirius red staining and associated with an increased expression of genes encoding extracellular matrix proteins such as fibronectin, procollagen type 1α1 and type 3α1 and especially connective tissue growth factor (CTGF). Furthermore miR-133a, one of the most predominant cardiac miRNAs, is strongly downregulated when SRF is overexpressed. By comparison a low level overexpression of SRF has minor impact on these different processes. Investigation with miR-133a, antimiR-133a and AdSRF-VP16 experiments in H9c2 cardiac cells demonstrated that: 1)-miR-133a acts as a repressor of SRF and CTGF expression; 2)-a simultaneous overexpression of SRF by AdSRF-VP16 and inhibition of miR-133a by a specific antimiR increase CTGF expression; 3)-miR-133a overexpression can block the upregulation of CTGF induced by AdSRF-VP16. Taken together, these findings reveal a key role of the SRF/CTGF/miR-133a axis in the regulation of cardiac fibrosis.
心肌纤维化会导致心脏重塑和心功能丧失，进而引发心力衰竭。血清反应因子（SRF）是一种转录因子，参与调控大量与心脏结构和功能相关的基因。为了研究SRF在心脏中过表达的影响，我们通过Cre/loxP策略构建了一种新的心脏特异性且可由他莫昔芬诱导的SRF过表达小鼠模型。在此，我们报告SRF的高水平过表达会导致心脏细胞结构的严重改变，影响心肌细胞和心脏成纤维细胞之间的平衡，同时也会使心脏基因表达程序发生深刻变化。纤维化的急剧发展表现为天狼星红染色强烈，并与编码细胞外基质蛋白（如纤连蛋白、Ⅰ型前胶原α1链和Ⅲ型前胶原α1链，尤其是结缔组织生长因子（CTGF））的基因表达增加有关。此外，当SRF过表达时，最主要的心脏微小RNA之一miR - 133a会强烈下调。相比之下，SRF的低水平过表达对这些不同过程的影响较小。在H9c2心脏细胞中进行的miR - 133a、抗miR - 133a和AdSRF - VP16实验表明：1）- miR - 133a可作为SRF和CTGF表达的抑制因子；2）- AdSRF - VP16同时过表达SRF以及用特异性抗miR抑制miR - 133a会增加CTGF表达；3）- miR - 133a过表达可阻断AdSRF - VP16诱导的CTGF上调。综上所述，这些发现揭示了SRF/CTGF/miR - 133a轴在心脏纤维化调控中的关键作用。
