Heart valve replacement is the second most common cardiac surgery in the United States, and aortic valve sclerosis, an indicator of calcification, occurs in >25% of aged individuals. Recent findings have established common molecular interactions in valve development and adult disease. However, a cellular basis for valve regeneration or repair has not yet been identified. Preliminary studies demonstrate that the bHLH transcription factor Twist1 promotes proliferation and migration while inhibiting differentiation of valve progenitor cells. During normal development, Twist1 expression is downregulated during valve remodeling, and expression is undetectable in normal adult valves. However, Twist1 expression is increased in diseased human valves in regions with increased cell proliferation and ECM disorganization, supporting a role for Twist1 in adult valve pathogenesis and potentially repair. We hypothesize that Twist1 promotes valve progenitor cell proliferation and inhibits differentiation, thereby maintaining the progenitor population, during embryonic development and postnatal valve pathogenesis. The proposed studies will dissect the cellular and molecular mechanisms of valve progenitor generation and maintenance in heart valve development and disease.
The aims are 1) Determine if Twist1 homo- and hetero-dimers have differential functions in valve progenitor cell proliferation, migration and differentiation. 2) Determine if Twist1 expression is sufficient to generate valve progenitors by inducing EMT and cell proliferation in late stages of embryonic valve development and in mature adult valves. 3) Define the pathology associated with Twist1 induction in human valve disease and determine if Twist1 expression prevents valve disease progression in mice. The long-term goals of these studies are the definition of critical regulatory pathways in heart valve cell lineage development and the identification of potential regenerative mechanisms with therapeutic applications in valve disease.

Public Health Relevance

Heart valve malformations are among the most common types of birth defects and adult valve disease is a significant cause of morbidity and mortality in the United States. Our studies will examine the ability of the transcription factor Twist1 to promote the formation and expansion of progenitor cells in normal valve development. We also will determine if Twist1 functions in adult valve disease to promote cell proliferation while inhibiting pathological calcification.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Cardiovascular Differentiation and Development Study Section (CDD)
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Schramm, Charlene A
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Cincinnati Children's Hospital Medical Center
United States
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Wirrig, Elaine E; Yutzey, Katherine E (2014) Conserved transcriptional regulatory mechanisms in aortic valve development and disease. Arterioscler Thromb Vasc Biol 34:737-41
Chakraborty, Santanu; Sengupta, Arunima; Yutzey, Katherine E (2013) Tbx20 promotes cardiomyocyte proliferation and persistence of fetal characteristics in adult mouse hearts. J Mol Cell Cardiol 62:203-13
Yutzey, Katherine E (2013) A twist of proepicardial fate. Circ Res 113:1106-8
Cheek, Jonathan D; Wirrig, Elaine E; Alfieri, Christina M et al. (2012) Differential activation of valvulogenic, chondrogenic, and osteogenic pathways in mouse models of myxomatous and calcific aortic valve disease. J Mol Cell Cardiol 52:689-700
Chakraborty, Santanu; Yutzey, Katherine E (2012) Tbx20 regulation of cardiac cell proliferation and lineage specialization during embryonic and fetal development in vivo. Dev Biol 363:234-46
Lee, Mary P; Yutzey, Katherine E (2011) Twist1 directly regulates genes that promote cell proliferation and migration in developing heart valves. PLoS One 6:e29758
Hinton, Robert B; Yutzey, Katherine E (2011) Heart valve structure and function in development and disease. Annu Rev Physiol 73:29-46
Wirrig, Elaine E; Hinton, Robert B; Yutzey, Katherine E (2011) Differential expression of cartilage and bone-related proteins in pediatric and adult diseased aortic valves. J Mol Cell Cardiol 50:561-9
Lincoln, Joy; Yutzey, Katherine E (2011) Molecular and developmental mechanisms of congenital heart valve disease. Birth Defects Res A Clin Mol Teratol 91:526-34
Wirrig, Elaine E; Yutzey, Katherine E (2011) Transcriptional regulation of heart valve development and disease. Cardiovasc Pathol 20:162-7

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