Tgfβ-Smad and MAPK signaling mediate scleraxis and proteoglycan expression in heart valves. J Mol Cell Cardiol 2013 Dec;65:137-46
Date
10/26/2013Pubmed ID
24157418Pubmed Central ID
PMC3869408DOI
10.1016/j.yjmcc.2013.10.007Scopus ID
2-s2.0-84887141758 (requires institutional sign-in at Scopus site) 34 CitationsAbstract
Mature heart valves are complex structures consisting of three highly organized extracellular matrix layers primarily composed of collagens, proteoglycans and elastin. Collectively, these diverse matrix components provide all the necessary biomechanical properties for valve function throughout life. In contrast to healthy valves, myxomatous valve disease is the most common cause of mitral valve prolapse in the human population and is characterized by an abnormal abundance of proteoglycans within the valve tri-laminar structure. Despite the clinical significance, the etiology of this phenotype is not known. Scleraxis (Scx) is a basic-helix-loop-helix transcription factor that we previously showed to be required for establishing heart valve structure during remodeling stages of valvulogenesis. In this study, we report that remodeling heart valves from Scx null mice express decreased levels of proteoglycans, particularly chondroitin sulfate proteoglycans (CSPGs), while overexpression in embryonic avian valve precursor cells and adult porcine valve interstitial cells increases CSPGs. Using these systems we further identify that Scx is positively regulated by canonical Tgfβ2 signaling during this process and this is attenuated by MAPK activity. Finally, we show that Scx is increased in myxomatous valves from human patients and mouse models, and overexpression in human mitral valve interstitial cells modestly increases proteoglycan expression consistent with myxomatous mitral valve phenotypes. Together, these studies identify an important role for Scx in regulating proteoglycans in embryonic and mature valve cells and suggest that imbalanced regulation could influence myxomatous pathogenesis.
Author List
Barnette DN, Hulin A, Ahmed AS, Colige AC, Azhar M, Lincoln JAuthor
Joy Lincoln PhD Professor in the Pediatrics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsAnimals, Newborn
Basic Helix-Loop-Helix Transcription Factors
Chickens
Disease Models, Animal
Heart Valves
Humans
MAP Kinase Signaling System
Mice
Mitral Valve
NIH 3T3 Cells
Proteoglycans
Smad Proteins
Sus scrofa
Transforming Growth Factor beta