Fibrous Skeleton Of Heart Research Articles

Cardiac System

The circulatory system, which consists of the heart, arterial system, venous system, and lymphatics, constitutes a complicated network of vessels and ducts that are responsible for the delivery of oxygenated blood to the body and return of deoxygenated blood to the heart and lungs. The heart is at the center of the circulatory system, and its pumping mechanism provides energy and nutrition to all organs in the body. This review focuses on the anatomy and physiology of the heart and describes anatomic details that are important to the planning of many common cardiac operations. This review contains 28 figures, and 25 references. Key words: aortic root, aortic valve, atrial septum, atrioventricular node, coronary artery, fibrous skeleton of heart, mitral valve, myocardium, pericardium, pulmonic valve, sinoatrial node, tricuspid valve, ventricular septum

The Cardiac System

The circulatory system, which consists of the heart, arterial system, venous system, and lymphatics, constitutes a complicated network of vessels and ducts that are responsible for the delivery of oxygenated blood to the body and return of deoxygenated blood to the heart and lungs. The heart is at the center of the circulatory system, and its pumping mechanism provides energy and nutrition to all organs in the body. This review focuses on the anatomy and physiology of the heart and describes anatomic details that are important to the planning of many common cardiac operations. This review contains 28 figures, and 25 references. Key words: aortic root, aortic valve, atrial septum, atrioventricular node, coronary artery, fibrous skeleton of heart, mitral valve, myocardium, pericardium, pulmonic valve, sinoatrial node, tricuspid valve, ventricular septum

Cardiac System

The circulatory system, which consists of the heart, arterial system, venous system, and lymphatics, constitutes a complicated network of vessels and ducts that are responsible for the delivery of oxygenated blood to the body and return of deoxygenated blood to the heart and lungs. The heart is at the center of the circulatory system, and its pumping mechanism provides energy and nutrition to all organs in the body. This review focuses on the anatomy and physiology of the heart and describes anatomic details that are important to the planning of many common cardiac operations. This review contains 28 figures, and 25 references. Key words: aortic root, aortic valve, atrial septum, atrioventricular node, coronary artery, fibrous skeleton of heart, mitral valve, myocardium, pericardium, pulmonic valve, sinoatrial node, tricuspid valve, ventricular septum

Cardiac System

The circulatory system, which consists of the heart, arterial system, venous system, and lymphatics, constitutes a complicated network of vessels and ducts that are responsible for the delivery of oxygenated blood to the body and return of deoxygenated blood to the heart and lungs. The heart is at the center of the circulatory system, and its pumping mechanism provides energy and nutrition to all organs in the body. This review focuses on the anatomy and physiology of the heart and describes anatomic details that are important to the planning of many common cardiac operations. This review contains 28 figures, and 25 references. Key words: aortic root, aortic valve, atrial septum, atrioventricular node, coronary artery, fibrous skeleton of heart, mitral valve, myocardium, pericardium, pulmonic valve, sinoatrial node, tricuspid valve, ventricular septum

Periostin expression by epicardium-derived cells is involved in the development of the atrioventricular valves and fibrous heart skeleton

The epicardium is embryologically formed by outgrowth of proepicardial cells over the naked heart tube. Epicardium-derived cells (EPDCs) migrate into the myocardium, contributing to myocardial architecture, valve development, and the coronary vasculature. Defective EPDC formation causes valve malformations, myocardial thinning, and coronary defects. In the atrioventricular (AV) valves and the fibrous heart skeleton isolating atrial from ventricular myocardium, EPDCs colocalize with periostin, a matrix molecule involved in remodeling. We investigated whether proepicardial outgrowth inhibition affected periostin expression and how this related to development of the AV valves and fibrous heart skeleton. Periostin expression by epicardium and EPDCs was confirmed in vitro in primary cultures of human and quail EPDCs. Disturbing EPDC formation in quail embryos reduced periostin expression in the endocardial cushions and AV junction. Disturbed fibrous tissue development resulted in AV myocardial connections reflected by preexcitation electrocardiographic patterns. We conclude that EPDCs are local producers of periostin. Disturbance of EPDC formation results in decreased cardiac periostin levels and hampers the development of fibrous tissue in AV junction and the developing AV valves. The resulting cardiac anomalies might link to Wolff–Parkinson White syndrome with persistent AV myocardial connections.

Cardiovascular development: towards biomedical applicability

.During cardiogenesis, the epicardium grows from the proepicardial organ to form the outermost layer of the early heart. Part of the epicardium undergoes epithelial-mesenchymal transformation, and migrates into the myocardium. These epicardium- derived cells differentiate into interstitial fibroblasts, coronary smooth muscle cells, and perivascular fibroblasts. Moreover, epicardium-derived cells are important regulators of formation of the compact myocardium, the coronary vasculature, and the Purkinje fiber network, thus being essential for proper cardiac development. The fibrous structures of the heart such as the fibrous heart skeleton and the semilunar and atrioventricular valves also depend on a contribution of these cells during development. We hypothesise that the essential properties of epicardium-derived cells can be recapitulated in adult diseased myocardium. These cells can therefore be considered as a novel source of adult stem cells useful in clinical cardiac regeneration therapy.

Origin, Fate, and Function of Epicardium-Derived Cells (EPDCs) in Normal and Abnormal Cardiac Development

During heart development, cells of the primary and secondary heart field give rise to the myocardial component of the heart. The neural crest and epicardium provide the heart with a considerable amount of nonmyocardial cells that are indispensable for correct heart development. During the past 2 decades, the importance of epicardium-derived cells (EPDCs) in heart formation became increasingly clear. The epicardium is embryologically formed by the outgrowth of proepicardial cells over the naked heart tube. Following epithelial-mesenchymal transformation, EPDCs form the subepicardial mesenchyme and subsequently migrate into the myocardium, and differentiate into smooth muscle cells and fibroblasts. They contribute to the media of the coronary arteries, to the atrioventricular valves, and the fibrous heart skeleton. Furthermore, they are important for the myocardial architecture of the ventricular walls and for the induction of Purkinje fiber formation.Whereas the exact signaling cascades in EPDC migration and function still need to be elucidated, recent research has revealed several factors that are involved in EPDC migration and specialization, and in the cross-talk between EPDCs and other cells during heart development. Among these factors are the Ets transcription factors Ets-1 and Ets-2. New data obtained with lentiviral antisense constructs targeting Ets-1 and Ets-2 specifically in the epicardium indicate that both factors are independently involved in the migratory behavior of EPDCs. Ets-2 seems to be especially important for the migration of EPDCs into the myocardial wall, and to subendocardial positions in the atrioventricular cushions and the trabeculae.With respect to the clinical importance of correct EPDC development, the relation with coronary arteriogenesis has been noted well before. In this review, we also propose a role for EPDCs in cardiac looping, and emphasize their contribution to the development of the valves and myocardial architecture. Lastly, we focus on the congenital heart anomalies that might be caused primarily by an epicardial developmental defect.

Expression patterns of Tgfbeta1-3 associate with myocardialisation of the outflow tract and the development of the epicardium and the fibrous heart skeleton.

Transforming growth factor-beta (Tgfbeta) is essential for normal embryogenesis. The cardiac phenotypes obtained after knockout of each of the three mammalian isoforms suggest different roles during morphogenesis. We studied cardiovascular expression of Tgfbeta1-3 in parallel tissue sections of normal mouse embryos from 9.5 to 15.5 days post coitum (dpc) by using radioactive in situ hybridisation. The Tgfbeta isoforms are differentially expressed in unique and in overlapping patterns during cardiovascular development. In the vessels, Tgfbeta1 is found in the intima, whereas Tgfbeta2 and -beta3 are mainly present in the media and adventitia of the great arteries. Tgfbeta1 is present in the endocardium at all stages examined. The Tgfbeta2 signal in the endocardium of the atrioventricular canal and outflow tract (9.5 dpc) shifts during epithelial-mesenchymal transformation toward the mesenchymal cushions (10.5-11.5 dpc) after which it exhibits a marked spatiotemporal expression pattern as the cushion differentiation progresses (11.5-15.5 dpc). The myocardium underlying the endocardial cushions and the atrial muscular septum are intensely positive for Tgfbeta2 at early stages (9.5-11.5 dpc) and expression decreases at 12.5 days. In contrast to earlier reports, we find marked overlap of Tgfbeta2 and -beta3 expression. Tgfbeta3 expression shows a characteristic distribution in the mesenchymal cushions, suggesting a role in cushion differentiation, possibly additional to Tgfbeta2. From 14.5 dpc onward, a strong Tgfbeta3 signal is found in the fibrous septum primum of the atrium and in the fibrous skeleton of the heart. Special attention was paid to the proepicardial organ and its derivatives. The proepicardial organ strongly expresses Tgfbeta2 as early as 9.5 days, and all isoforms are present in the epicardium from 12.5 dpc onward. The spatiotemporal cardiovascular expression of Tgfbeta1-3 supports both specific and complementary functions during cardiovascular development that might explain functional redundancy between the Tgfbeta-isoforms. The information provided favors novel roles of Tgfbeta1-3 in epicardial development, of Tgfbeta2 in myocardialisation, and of Tgfbeta3 in differentiation of the fibrous structures of the heart.

Epicardium-derived cells contribute a novel population to the myocardial wall and the atrioventricular cushions.

The epicardium and dorsal mesocardium are known to be the source of structures that form the wall of the coronary vessels. Because mouse knockout studies have shown that proper epicardial formation is also essential for myocardial development, we have studied in detail the migration and differentiation of epicardium-derived cells (EPDCs) within the developing heart. We constructed chicken-quail chimeras by grafting the quail epicardial organ, including a piece of primordial liver, at essentially stages 16 and 17. The embryos were studied at stages 25 to 43. To detect quail-derived EPDCs, an anti-quail nucleus antibody was used in combination with several differentiation markers, eg, for muscle actin, for vascular smooth muscle cells, for procollagen-I, for quail endothelium, and for Purkinje fibers. At stages 25 to 31, EPDCs are encountered in the myocardial wall and the subendocardial region. The latter deposition is spatially facilitated as the endocardium protrudes through transient discontinuities in the myocardium to contact the subepicardial layer. Later on, at stages 32 to 43, EPDCs invaded, by way of the atrioventricular sulcus, the atrioventricular cushion tissue. The localization is apparent at the interface with the myocardium, as well as subendocardially, but never within the endocardial lining. The origin of endothelium, smooth muscle cells, and fibroblasts of the coronary vessel wall from the epicardial graft were confirmed in accordance with already published data. The functional role of the novel EPDCs in the subendocardium, myocardium, and atrioventricular cushions remains to be investigated. A close positional relationship is found with the differentiating Purkinje fibers. Furthermore, a regulatory role is postulated in the process of endocardial-mesenchymal transformation. The ultimate fate of EPDCs seems to be a cardiac fibroblast cell line involved in the formation of the fibrous heart skeleton.