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. Author manuscript; available in PMC: 2013 Jul 17.
Published in final edited form as: Nature. 2012 Dec 5;493(7432):433–436. doi: 10.1038/nature11682

Figure 3. New cardiomyocytes are derived from pre-existing cardiomyocytes during aging.

Figure 3

a) Experimental strategy. MerCreMer+/ZEG+ mice (n=4) treated for 2 wks with 4OH-tamoxifen to induce cardiomyocyte-specific GFP expression. 15N-thymidine administered continuously during 10 wk chase, then cycling cells identified by 15N-labeling. New cardiomyocytes (15N+) derived from preexisting cardiomyocytes should express GFP at a rate similar to surrounding quiescent (15N−) cardiomyocytes. New cardiomyocytes (15N+) derived from progenitors should be GFP−.

b) Left: 15N:14N HSI image demonstrating 15N-thymidine labeled cardiomyocyte nucleus (white asterisk) and 15N-labeled non-cardiomyocyte (white arrow). Right: Immunofluorescent image showing 15N-labeled cardiomyocyte is GFP+. Scale bar = 15μm.