Cardiac disease is the second leading cause of death, with most cases caused by heart attacks stemming from occlusion of coronary arteries.
Most heart attacks are survived but the heart is often left in an impaired state which leads to shortened lifespan.
There is considerable interest and research looking into the use of stem cells to repair damaged heart, with promising results already shown in human trials.
A striking new study shows how potent the regenerative potential in the heart is.
In this study, researchers simulated a massive heart attack by tying the main coronary artery in one day old mice. As expected, “the LAD ligation triggered substantial cardiac injury in the left ventricle defined by Caspase 3 activation and massive cell death. Ischemia-induced cardiomyocyte death was also visible on day 4 after LAD ligation.”
However the authors found “remarkably, 7 days after the initial ischemic insult, we observed complete cardiac regeneration without any signs of tissue damage or scarring. This tissue regeneration translated into long-term normal heart functions as assessed by echocardiography.”
This total regeneration was not observed when 7 day old mice underwent the same procedure. “LAD ligations in 7-day-old mice resulted in extensive scarring comparable to adult mice, indicating that the regenerative capacity for complete cardiac healing after heart attacks can be traced to the first week after birth.”
The authors went on the analyse the RNA transcription pattern differences in the 1 and 7 day old mice to see what molecular pathways underlie the ability of the heart to completely regenerate.
They found a “transcriptional programme of major changes in genes mediating mitosis and cell division between days 1, 3 and 10 postnatally and a very limited set of genes, including genes regulating cell cycle and extracellular matrix synthesis, being differentially regulated in the regenerating hearts.”
“We present for the first time a mammalian model of complete cardiac regeneration following a severe ischemic cardiac injury. This novel model system provides the unique opportunity to uncover molecular and cellular pathways that can induce cardiac regeneration after ischemic injury, findings that one day could be translated to human heart attack patients.”