The effect of T regulatory cells on the proliferation capacity of cardiomyocytes (cardiac muscle cells) is analysed in Nature Communications this week. The study in mice sheds light on the cellular factors allowing proliferation of cardiomyocytes in the heart of an embryo, and suggests that the same factors may also promote proliferation of maternal cardiomyocytes. The findings may have potential implications for the treatment of heart attacks.

Cardiomyocytes proliferate during the development of the embryo’s heart but lose this capacity after birth, which is one of the main reasons why the adult heart does not regenerate spontaneously after damage.

Serena Zacchigna and colleagues find that immune cells called T regulatory cells, known to allow the immunological tolerance of the mother towards the embryo, also promote the proliferation of embryonic cardiomyocytes. Additionally, they show that these immune cells may also promote proliferation of cardiomyocytes in the mother’s heart during pregnancy. In a mouse model of cardiac disease, the injection of T regulatory cells close to the site of a cardiac ischemic wound promotes a regenerative response in the heart partly through the stimulation of cardiomyocyte proliferation. This is suggested to be a consequence of the release of pro-proliferative molecules by T regulatory cells.

Further investigations will be required to confirm the pro-proliferative effects of T regulatory cells; however, the findings add to our understanding of cardiac biology during pregnancy and suggest potential ways to boost cardiac repair.