Epicardium formation on isolated hearts in vitro. Hearts from cmlc2:EGFP; tcf21:DsRed2 larvae were extracted and placed in culture for 7 days. (A) Representative confocal image of a single ventricle prior at the time of isolation (Day 0; n = 10). (B) Confocal image of a fixed ventricle after 7 days in culture (n = 10). (C) Epifluorescent images tracking epicardium formation in culture. Images shown are from days 1, 3, 5 and 7 (n = 10). tcf21:DsRed2 marks epicardial cells (red) and cmlc2:EGFP marks cardiomyocytes (green). DAPI (DNA) is in blue in A and B. Scale bars = 50 microns.