NRG1 and myocardial infarction: As ERBB2 is incompetent to bind NRG1, transplanting unmodified MSCs that lack ERBB4 cannot activate NRG1-ERBB signaling, and thus stultifies the existing NRG1 in the infarcted myocardium.24 We introduced ERBB4 expression into MSCs (MSC-ERBB4) and transplanted them into MI model.