Development of a spontaneously beating vein by cardiomyocyte transplantation in the wall of the inferior vena cava in a rat: a pilot study

Thinking Outside the Heart: Use of Engineered Cardiac Tissue for the Treatment of Chronic Deep Venous Insufficiency

This article considers the use of autologous stem cell-derived cardiomyocytes as a novel means to aid venous return. The approach consists of creating external cuffs of engineered heart tissue around vein segments with incompetent or poorly competent valves. The engineered heart tissue cuff prevents distention of the impaired vein segments and aids unidirectional flow by its rhythmic contractions. There appear to be no fundamental limitations to this approach as feasibility of all of the individual components has already been shown. Here, we underline the clinical need for novel ways to treat chronic deep venous insufficiency, review previous research that enabled this approach, consider potential designs of engineered heart tissue cuffs, and outline its advantages and future challenges.

Discontinuous thoracic venous cardiomyocytes and heart exhibit synchronized developmental switch of troponin isoforms

Cardiomyocyte-like cells have been reported in thoracic veins of rodents and other mammals, but their differentiation state and relationship to the muscle mass in the heart remain to be characterized. Here we investigated the distribution, ultrastructure, expression and developmental regulation of myofilament proteins of mouse and rat pulmonary and azygos venous cardiomyocytes. Tracing cardiomyocytes in transgenic mouse tissues using a lacZ reporter gene driven by a cloned rat cardiac troponin T promoter demonstrated scattered distribution of cardiomyocytes discontinuous from the atrial sleeves. The longitudinal axis of venous cardiomyocytes is perpendicular to that of the vessel. These cells contain typical sarcomere structures and intercalated discs as shown in electron microscopic images, and express cardiac isoforms of troponin T, troponin I and myosin. The expression of troponin I isoform genes and the alternative splicing of cardiac troponin T in thoracic venous cardiomyocytes are regulated during postnatal development in precise synchrony with that in the heart. However, the patterns of cardiac troponin T splicing in adult rat thoracic venous cardiomyocytes are slightly but clearly distinct from those in the atrial and ventricular muscles. The data indicate that mouse and rat thoracic venous cardiomyocytes residing in extra-cardiac tissue possess a physiologically differentiated state and an intrinsically pre-set developmental clock, which are apparently independent of the very different hemodynamic environments and functional features of the vessels and heart.