Thymosin beta 4 treatment after myocardial infarction does not reprogram epicardial cells into cardiomyocytes

Zhou B, Honor LB, Ma Q, Oh JH, Lin RZ, Melero-Martin JM, von Gise A, Zhou P, Hu T, He L, Wu KH, Zhang H, Zhang Y, Pu WT · Journal of Molecular and Cellular Cardiology

Tβ4 thickened the epicardium, raised coronary capillary density and, as in the original reports, reduced infarct size, fibrosis and cardiomyocyte apoptosis — but lineage tracing showed epicardium-derived cells never became cardiomyocytes or coronary endothelium. The angiogenic effect replicated, the regenerative one did not.

Population

Mice with genetic epicardial lineage tracing, treated after myocardial infarction

Intervention

Thymosin β4 daily for one week after infarction, analysed at two weeks

Comparator

PBS-treated infarcted mice

Limitations

Tests treatment after infarction rather than the pre-injury priming used in the original reports; a genuine partial non-replication rather than a flat contradiction. Clinical-grade Tβ4 from the same source as those reports, supplied by RegeneRx; NIH and American Heart Association funded, no disclosures.