Abstract
Local endometrial stem cells play an important role in regulating endometrial thickness, which is an essential factor for successful embryo implantation and pregnancy outcomes. Importantly, defects in endometrial stem cell function can be responsible for thin endometrium and subsequent recurrent pregnancy losses. Therefore, many researchers have directed their efforts toward finding a novel stimulatory factor that can enhance the regenerative capacity of endometrial stem cells. Sonic hedgehog (SHH) is a morphogen that plays a key role in regulating pattern formation throughout embryonic limb development. In addition to this canonical function, we identified for the first time that SHH is actively secreted as a stem cell-activating factor in response to tissue injury and subsequently stimulates tissue regeneration by promoting various beneficial functions of endometrial stem cells. Our results also showed that SHH exerts stimulatory effects on endometrial stem cells via the FAK/ERK1/2 and/or phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways. More importantly, we also observed that endometrial stem cells stimulated with SHH showed markedly enhanced differentiation and migratory capacities and subsequent in vivo therapeutic effects in an endometrial ablation animal model.