Mending broken hearts: cardiac development as a basis for adult heart regeneration and repair

In response to myocardial infarction, damaged adult cardiomyocytes are replaced by activated fibroblasts that form a fibrotic scar, leading to reduced cardiac function and heart failure. As the adult heart has limited regenerative capacity, there is a need to develop innovative strategies to enhance cardiac repair and regeneration.Cellular replacement strategies for heart repair, in which stem cells and other cell types are injected directly into the injured heart or into the coronary circulation, have shown modest beneficial effects on cardiac function. An alternative approach is to reprogramme non-muscle cells in the injured heart to adopt a cardiac fate.Positive cell cycle regulators are highly expressed in the embryonic heart and downregulated in the adult heart. Activation of various signalling pathways in the heart can modestly reactivate proliferation in adult cardiomyocytes.Identification of transcription factors and microRNAs that control heart formation has enabled reprogramming of non-muscle cells into cardiomyocytes and other cell types of the heart. Following injury, in vivo reprogramming of non-myocytes into cardiomyocytes has improved heart function in mice.Epicardial cells are activated following cardiac injury and have the potential to differentiate into various cell types, offering a niche that can be targeted with small molecules. This provides an attractive approach for regenerative medicine.The inflammatory response has a role in cardiac repair following injury. Several studies have shed light on both positive and negative roles of the inflammatory response in tissue repair and regeneration.