We analyzed the expression of the Hh ligand genes shhb, dhh, ihha, and ihhb using 4-HT–treated injured shhact/ctand tcf21:CreER; shhact/ctheart samples via qRT-PCR. shhb and ihha expression was not detectable, consistent with the result described in a previous study (Wang J, et al. Nature 2015). The expression of dhh and ihhb was detected in the injured heart, but their expression was not significantly changed by the inactivation of shha expression in the epicardium. As detailed in the response to comment #3, we also examined the expression of dhh and ihhb in purified epicardial cells via semi-qRT-PCR. We essentially observed the same result as that of the qRT-PCR analysis; namely, we did not observe a clear increase in the expression of these Hh ligand genes in shha-deficient epicardial cells.