No effect of thymosin beta-4 on the expression of the transcription factor Islet-1 in the adult murine heart

Weinberger F, Nicol P, Starbatty J, Stubbendorff M, Becher PM, Schrepfer S, Eschenhagen T · Pharmacology Research & Perspectives

A single Islet-1-positive cell was found outside the sinoatrial node, outflow tract and cardiac ganglia across roughly 2,500 sections from eight Tβ4-primed infarcted hearts, against two cells in five controls. Infarct size did not differ, 5.58 ± 1.38% on Tβ4 against 4.74 ± 0.99% on vehicle. In ventricular explant culture Tβ4 changed nothing: Islet-1-positive cells appeared at the same density with or without it, came only from the basal heart and outflow tract, and carried smooth-muscle actin and DDR2 — anatomy rather than an induced progenitor state. No evidence that Tβ4 reactivates the Islet-1 programme earlier work had attributed to it.

Population

Islet-1 reporter mice primed with Tβ4 and then infarcted

Intervention

Thymosin β4 priming before myocardial infarction

Comparator

Untreated infarcted reporter mice

Limitations

Two, four and two treated hearts at the three timepoints against one, three and one controls. It addresses one marker of one proposed mechanism, and cardiac function was not measured — infarct size was, and did not differ. Dosing followed the protocol of the study being reassessed. The peptide was provided by RegeneRx Biopharmaceuticals, which the acknowledgements state and the disclosure, "None declared", does not.