Abstract

Induced pluripotent stem (iPS) cells provide a promising source of cardiac progenitor cells for administration to the infarcted heart. Here, we describe a protocol for efficient, serum free, directed differentiation of human iPS cells, as a monolayer, that yields a mixed population in which cardiomyocytes, endothelium and smooth muscle cells constitute over 50% of the differentiated population, with no additional selection strategies utilised. GFP positive cardiac progenitors from human iPS cells (2×10⁶) were administered by direct injection into the myocardium of athymic nude rats following 50 min of ischaemia. Cardiac function was measured using MRI at 2 days, 2, 6 and 10 weeks. At 10 weeks the hearts were removed for histology. By 6 weeks, control infarcted hearts (n=5) had significantly larger end systolic volumes and lower ejection fractions than sham operated hearts (n=3) whereas hearts treated with iPS-derived cardiac differentiated cells (n=4) maintained cardiac function; such that by 10 weeks the end systolic volumes and ejection fractions were not significantly different from those of the sham operated animals (ejection fraction at 10 weeks: sham 77±5%, infarct 45±9% (p<0.05 vs sham), iPS 62±4%). Histological analysis showed that the human iPS-derived cardiac progenitor cells engrafted, differentiated into cardiomyocytes and smooth muscle, and persisted for at least 10 weeks post-infarct. Thus efficient directed differentiation of human iPS cells towards the cardiac lineage generates cells that can prevent loss of heart function after ischaemic heart damage.