Expression and localisation of thymosin beta-4 in the developing human early fetal heart

Abstract

BackgroundThe objective of this study was to investigate the expression and localisation of thymosin β4 (Tβ4) in the developing human heart. Tβ4 is a cardioprotective protein which may have therapeutic potential. While Tβ4 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 Tβ4 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 Tβ4 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 Tβ4 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 Tβ4 is localised to these cell types within the early fetal human heart.ResultsTβ4 mRNA was found to be expressed in both the atria and the ventricles of the early fetal human heart. Tβ4 protein was found to be primarily localised to CD31-expressing endothelial cells and the endocardium as well as being present in the epicardium. Tβ4-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 Tβ4 in the developing human heart and demonstrates for the first time that Tβ4 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.

Spatiotemporal single-cell RNA sequencing of developing chicken hearts identifies interplay between cellular differentiation and morphogenesis

“…Our analysis demonstrates that thymosin beta-4 is ubiquitously expressed by all cell types but remains significantly enriched at the mRNA and protein levels in only the coronary vasculature cells at all the stages analyzed. A previous study in one late fetal human heart stage demonstrated high protein expression within vascular endothelial cells only low expression in cardiomyocytes 56 , in agreement with our observations. Beta thymosins have regenerative potential as demonstrated in adult myocardial infarction models 41 , 57 , 58 .…”

Utilizing Developmentally Essential Secreted Peptides Such as Thymosin Beta-4 to Remind the Adult Organs of Their Embryonic State—New Directions in Anti-Aging Regenerative Therapies

“…In human embryos, TB4 protein was primarily localized in endothelial cells of the heart, including the medium coronary vessels. The expression of TB4 in the atria, epicardium, and endocardium, however, was equally confirmed in mice and humans [81]. Note absence or very low levels of thymosin β4 expression in mesenchymal cells (a,c, magenta arrowhead).…”

“…Finally, in addition to the expression in the heart, whole mount mRNA analyses revealed the peptide is equally expressed in the brain, pharyngeal arches, eyes, limb buds, and myotomes, suggesting a potential role for the molecule during the development of these organs in mice [87]. Excitingly, recent analyses of TB4 in human embryos confirmed the presence of the peptide in the developing human heart [81]. In contrast to our findings demonstrating that TB4 co-localizes clearly with muscle actin positive cells in murine embryos, Saunders et al did not find TB4 in the ventricular myocardium.…”

“…As suggested, investigation of a molecule's pre-and postnatal expression may presumably provide significant information regarding its potential clinical utilization and appliance. According to the present and earlier literature, beta thymosins are widely expressed among various tissues such as the brain, kidneys, heart, skin, eyes and cell types of the body [73][74][75][76][77][78][79][80][81][82][83][84]. The first investigations were communicated by Lin and colleagues in 1990, when they presented significant mRNA expression of both TB10 and TB4 in the cortex and cerebellum [73].…”

Epicardial Contribution to the Developing and Injured Heart: Exploring the Cellular Composition of the Epicardium

“…Therefore, considering the marginal cellular contribution to the injured heart it could be relevant to promote epicardial proliferation and migration via external stimuli. One approach to stimulate cardiac repair via the epicardium is by treating mice with thymosin ß4 (Tß4), a peptide secreted by endothelial cells and the epicardium during development and after injury (117)(118)(119). Importantly, treatment post-MI resulted in an increase in proliferating EPDCs and neovascularization of the injured heart (120).…”