Cardiac failure has a principal underlying aetiology of ischaemic damage arising from vascular insufficiency. Molecules that regulate collateral growth in the ischaemic heart also regulate coronary vasculature formation during embryogenesis. Here we identify thymosin β4 (Tβ4) as essential for all aspects of coronary vessel development in mice, and demonstrate that Tβ4 stimulates significant outgrowth from quiescent adult epicardial explants, restoring pluripotency and triggering differentiation of fibroblasts, smooth muscle cells and endothelial cells. Tβ4 knockdown in the heart is accompanied by significant reduction in the pro-angiogenic cleavage product N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). Although injection of AcSDKP was unable to rescue Tβ4 mutant hearts, it significantly enhanced endothelial cell differentiation from adult epicardially derived precursor cells. This study identifies Tβ4 and AcSDKP as potent stimulators of coronary vasculogenesis and angiogenesis, and reveals Tβ4-induced adult epicardial cells as a viable source of vascular progenitors for continued renewal of regressed vessels at low basal level or sustained neovascularization following cardiac injury.
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This research was supported by the British Heart Foundation and the Medical Research Council. We acknowledge the collaboration of K. Thiam and S. Millet of genOway (France) in generating the Tβ4shRNAflox line and G. Gish for providing RasGAPshRNA plasmid. We thank J. Clark for providing adult myocardial infarction heart samples and S. Bhattacharya for comments. Author Contributions N.S. carried out the majority of experimental work and data analyses with contributions from C.A.R., A.A.D.M. and P.R.R. K.M. and R.J.S. provided the Nkx2.5Cre mouse strain and K.R.C. provided the MLC2vCre mouse strain. P.R.R. devised and planned the project and the manuscript was written by P.R.R. and N.S.
Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.
This file contains Supplementary Methods detailing all the protocols used in the paper and Supplementary Figure Legends. (PDF 220 kb)
Supplementary Figures 1–9. (PDF 1070 kb)
A table summarising the penetrance and severity of the Tβ4 knockdown embryo phenotype. (PPT 29 kb)
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Smart, N., Risebro, C., Melville, A. et al. Thymosin β4 induces adult epicardial progenitor mobilization and neovascularization. Nature 445, 177–182 (2007). https://doi.org/10.1038/nature05383
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