Johansen Anne Katrine Z, Kasam Rajesh K, Vagnozzi Ronald J, Lin Suh-Chin J, Gomez-Arroyo Jose, Shittu Adenike, Bowers Stephanie L K, Kuwabara Yasuhide, Grimes Kelly M, Warrick Kathrynne, Sargent Michelle A, Baldwin Tanya A, Quaggin Susan E, Barski Artem, Molkentin Jeffery D
Division of Molecular Cardiovascular Biology (A.K.Z.J., R.K.K., R.J.V., S.-C.J.L., S.L.K.B., Y.K., K.M.G., K.W., M.A.S., T.A.B., J.D.M.), Department of Pediatrics, University of Cincinnati and Cincinnati Children's Hospital Medical Center, OH.
Division of Cardiology, Department of Medicine, Consortium for Fibrosis Research and Translation, University of Colorado Anschutz Medical Campus, Aurora (R.J.V.).
Circ Res. 2025 Jan 3;136(1):44-58. doi: 10.1161/CIRCRESAHA.124.325527. Epub 2024 Dec 4.
TCF21 (transcription factor 21) is a bHLH (basic helix-loop-helix) protein required for the developmental specification of cardiac fibroblasts (CFs) from epicardial progenitor cells that surround the embryonic heart. In the adult heart, TCF21 is expressed in tissue-resident fibroblasts and is downregulated in response to injury or stimuli leading to myofibroblast differentiation. These findings led to the hypothesis that TCF21 regulates fibroblast differentiation in the adult mammalian heart to affect fibrosis.
Tamoxifen-inducible Cre genetic mouse models were used to permit either gene deletion or its enforced expression in adult CFs. Histological and echocardiographic analyses were used, as well as transcriptomic analysis to determine the consequences of TCF21 gain-of-function and loss-of-function in vivo. Genomic occupancy was identified by chromatin immunoprecipitation and sequencing in CFs. Myocardial infarction and AngII (angiotensin II)/phenylephrine served as models of cardiac fibrosis.
Acute and long-term deletion of in CFs of the adult mouse heart does not alter fibroblast numbers, myofibroblast differentiation, or fibrosis. Fibroblast-specific gene-deleted mice demonstrate no significant alterations in cardiac function or scar formation in response to cardiac injury compared with control mice. In contrast, enforced expression of TCF21 in CFs inhibits myofibroblast differentiation and significantly reduces cardiac fibrosis and hypertrophy in response to 1 week of Ang II/phenylephrine infusion. Mechanistically, sustained TCF21 expression prevents the induction of genes associated with fibrosis and ECM (extracellular matrix) organization.
TCF21 expression is not required to maintain the cell state of CFs in the adult heart. However, preventing the normal downregulation of TCF21 expression with injury reduces myofibroblast formation, cardiac fibrosis, and the acute cardiac hypertrophic response following 1 week of Ang II/phenylephrine stimulation.
转录因子21（TCF21）是一种碱性螺旋-环-螺旋（bHLH）蛋白，是心外膜祖细胞发育分化为心脏成纤维细胞（CFs）所必需的，心外膜祖细胞环绕着胚胎心脏。在成年心脏中，TCF21在组织驻留成纤维细胞中表达，并在损伤或刺激导致肌成纤维细胞分化时下调。这些发现导致了这样一种假说，即TCF21调节成年哺乳动物心脏中的成纤维细胞分化以影响纤维化。
使用他莫昔芬诱导型Cre基因小鼠模型，以允许在成年CFs中进行基因缺失或强制表达。采用组织学和超声心动图分析，以及转录组分析来确定TCF21功能获得和功能丧失在体内的后果。通过染色质免疫沉淀和CFs测序鉴定基因组占有率。心肌梗死和血管紧张素II（AngII）/去氧肾上腺素用作心脏纤维化模型。
成年小鼠心脏CFs中TCF21的急性和长期缺失不会改变成纤维细胞数量、肌成纤维细胞分化或纤维化。与对照小鼠相比，成纤维细胞特异性TCF21基因缺失的小鼠在心脏损伤后心脏功能或瘢痕形成没有显著改变。相反，在CFs中强制表达TCF21可抑制肌成纤维细胞分化，并在输注1周的Ang II/去氧肾上腺素后显著减少心脏纤维化和肥大。机制上，持续的TCF21表达可防止与纤维化和细胞外基质（ECM）组织相关基因的诱导。
在成年心脏中，维持CFs的细胞状态不需要TCF21表达。然而，在损伤后阻止TCF21表达的正常下调可减少肌成纤维细胞形成、心脏纤维化以及在Ang II/去氧肾上腺素刺激1周后的急性心脏肥厚反应。
