Expression and Deposition of Fibrous Extracellular Matrix Proteins in Cardiac Valves during Chick Development

• Published in: Microscopy and microanalysis Vol. 17; no. 1; pp. 91 - 100
• Main Authors: Tan, Hong, Junor, Lorain, Price, Robert L., Norris, Russell A., Potts, Jay D., Goodwin, Richard L.
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.02.2011; Oxford University Press
• Subjects: Animals; Cardiovascular diseases; Chick Embryo; Chickens - anatomy & histology; Chickens - genetics; Chickens - growth & development; Chickens - metabolism; Collagen; Embryos; Extracellular Matrix - genetics; Extracellular Matrix - metabolism; Extracellular Matrix Proteins - analysis; Extracellular Matrix Proteins - genetics; Extracellular Matrix Proteins - metabolism; Gene Expression Regulation, Developmental; Heart Valves - anatomy & histology; Heart Valves - chemistry; Heart Valves - embryology; Heart Valves - metabolism; Microscopy, Confocal; Microscopy, Electron, Transmission; Proteins; Studies; cardiac valve development; spatiotemporal expression; annulus fibrosus; tenascin; valve morphology; membrane protrusion; collagen
• ISSN: 1431-9276; 1435-8115
• DOI: 10.1017/S1431927610094365

Extracellular matrix (ECM) plays essential signaling and structural roles required for the proper function of cardiac valves. Cardiac valves initially form as jelly-like cushions, which must adapt to withstand the increased circulation hemodynamics associated with fetal development and birth. This increased biomechanical stability of the developing valves is largely imparted by ECM proteins, which form a highly organized fibrous meshwork. Since heart valve defects contribute to most congenital heart diseases, understanding valve development will provide insight into the pathogenesis of various congenital valve anomalies. Thus, the goal of this study is to describe the spatiotemporal deposition of fibrous ECM proteins during cardiac valve development. Chick embryonic and fetal atrioventricular and semilunar valves were examined by light, confocal, and transmission electron microscopy (TEM). Our data demonstrate that fibrous ECM proteins are deposited when the leaflets are adopting an elongated and compacted phenotype. A general pattern of increased fibrotic ECM deposition was detected in valve tissues. Also, each ECM protein examined displayed a unique pattern of organization, suggesting that regulation of fibrous protein deposition is complex and likely involves both genetic and mechanical factors. In addition, the TEM study revealed the presence of membrane protrusions from valvular endocardium, indicating a potential mechanism for mechanical force transduction.