Expression And Localisation Of Thymosin Beta-4 In The Developing Human Early Fetal Heart

BackgroundThe objective of this study was to investigate the expression and localisation of thymosin beta 4 (T beta 4) in the developing human heart. T beta 4 is a cardioprotective protein which may have therapeutic potential. While T beta 4 is an endogenously produced protein with known importance during development, its role within the developing human heart is not fully understood. Elucidating the localisation of T beta 4 within the developing heart will help in understanding its role during cardiac development and is crucial for understanding its potential for cardioprotection and repair in the adult heart.MethodsExpression of T beta 4 mRNA in the early fetal human heart was assessed by PCR using both ventricular and atrial tissue. Fluorescence immunohistochemistry was used to assess the localisation of T beta 4 in sections of early fetal human heart. Co-staining with CD31, an endothelial cell marker, and with myosin heavy chain, a cardiomyocyte marker, was used to determine whether T beta 4 is localised to these cell types within the early fetal human heart.ResultsT beta 4 mRNA was found to be expressed in both the atria and the ventricles of the early fetal human heart. T beta 4 protein was found to be primarily localised to CD31-expressing endothelial cells and the endocardium as well as being present in the epicardium. T beta 4-associated fluorescence was greater in the compact layer of the myocardial wall and the interventricular septum than in the trabecular layer of the myocardium.ConclusionsThe data presented illustrates expression of T beta 4 in the developing human heart and demonstrates for the first time that T beta 4 in the human heart is primarily localised to endothelial cells of the cardiac microvasculature and coronary vessels as-well as to the endothelial-like cells of the endocardium and to the epicardium.