Estrogen Receptors α and β Mediate Contribution of Bone Marrow–Derived Endothelial Progenitor Cells to Functional Recovery After Myocardial Infarction

Background— Estradiol (E2) modulates the kinetics of circulating endothelial progenitor cells (EPCs) and favorably affects neovascularization after ischemic injury. However, the roles of estrogen receptors α (ERα) and β (ERβ) in EPC biology are largely unknown. Methods and Results— In response to E2, migration, tube formation, adhesion, and estrogen-responsive element–dependent gene transcription activities were severely impaired in EPCs obtained from ERα-knockout mice (ERαKO) and moderately impaired in ERβKO EPCs. The number of ERαΚΟ EPCs (42.4±1.5; P<0.001) and ERβKO EPCs (55.4±1.8; P=0.03) incorporated into the ischemic border zone was reduced as compared with wild-type (WT) EPCs (72.5±1.3). In bone marrow transplantation (BMT) models, the number of mobilized endogenous EPCs in E2-treated mice was significantly reduced in ERαKO BMT (WT mice transplanted with ERαKO bone marrow) (2.03±0.18%; P=0.004 versus WT BMT) and ERβKO BMT (2.62±0.07%; P=0.02 versus WT) compared with WT BMT (2.87±0.13%) (WT to WT BM...