Transient formation of collaterals contributes to the restoration of the arterial tree during cardiac regeneration in neonatal mice

Revascularization of ischemic myocardium following cardiac damage is an important step in cardiac regeneration. However, the mechanism of arteriogenesis has not been well described during cardiac regeneration. Here we investigated coronary artery remodeling and collateral growth during cardiac regeneration. Neonatal MI was induced by ligature of the left descending artery (LAD) in postnatal day (P) 1 or P7 pups from the Cx40-GFP mouse line and the arterial tree was reconstructed in 3D from images of cleared hearts collected at 1, 2, 4, 7 and 14 days after infarction. We show a rapid remodeling of the left coronary arterial tree induced by neonatal MI and the formation of numerous collateral arteries, which are transient in regenerating hearts after MI at P1 and persistent in non-regenerating hearts after MI at P7. This difference is accompanied by restoration of a perfused or a non-perfused LAD following MI at P1 or P7 respectively. Interestingly, collaterals ameliorate cardiac perfusion and drive LAD repair, and lineage tracing analysis demonstrates that the restoration of the LAD occurs by remodeling of pre-existing arterial cells independently of whether they originate in large arteries or arterioles. These results demonstrate that the restoration of the LAD artery during cardiac regeneration occurs by pruning as the rapidly forming collaterals that support perfusion of the disconnected lower LAD subsequently disappear on restoration of a unique LAD. These results highlight a rapid phase of arterial remodeling that plays an important role in vascular repair during cardiac regeneration. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/572474v3_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@5cb672org.highwire.dtl.DTLVardef@cdffc9org.highwire.dtl.DTLVardef@53e795org.highwire.dtl.DTLVardef@8920d0_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIRapid remodeling of the arterial tree is induced by myocardial infarction. C_LIO_LIThe endocardial response to ischemia differs between regenerated and non-regenerated hearts following myocardial infarction at postnatal days 1 or 7. C_LIO_LICollateral growth is rapid and transient in regenerated hearts while delayed and persistent in non-regenerated hearts. C_LIO_LICollateral arteries ameliorate cardiac perfusion and drive LAD repair. C_LIO_LIThe restoration of the LAD occurs by remodeling of pre-existing arterial cells. C_LI