The Hippo/YAP Pathway Regulates Cellular Senescence In Ovarian Cells

Fertility is a major determinant of animal productivity.In humans and most domestic animals,individuals can produce multiple offspring in their lifetime.In these animals,aging has a significant effect on the reproductive physiology and performance in female animals(including humans).With the growth of age,the fertility rate of women and animals decreased significantly.A better understanding of the nature of female reproductive senescence can identify common mechanisms underlying apparently different phenotypes associated with senescence,improve our understanding of female dynamics required for successful reproduction,and highlight potential approaches for regulating fertility in agriculture and conservation settings.However,the molecular mechanism underlying the regulation of cellular senescence is unclear.As a potent regulator of cell proliferation,differentiation,programmed cell death and thus tissue homeostasis,the Hippo signaling pathway has quickly drawn scientists’ attention in various physiological and pathological contexts in the past decade.However,the role of the Hippo signaling in mammalian reproduction is still poorly understood.Some recent studies demonstrated the potential importance of the Hippo signaling in ovarian function,but still little is known about how this pathway is regulated and the role it plays during specific stages of ovarian development,especially the ovarian aging.It is well known that the expression of certain activated oncogenes and strong or persistent tumor suppressor signals can contribute on cellular senescence in normal cells.Overall,the upstream core kinases of the Hippo pathway have been attributed tumor suppressive functions,while the major downstream effector,YAP,has been mainly described as an oncogene.However,whether the Hippo/YAP pathway can be involved in cellular senescence process in ovarian cells is still unclear.In this study,we want to explore the possible mechanism of the Hippo / YAP signaling pathway affecting the reproductive process from the perspective of ovarian cells proliferation and aging.we used Human Ovarian Granulose Cells(HOGC),Human Ovarian Surface Epithelial Cells,(HOSE),Human Ovarian Microvascular Endothelial cells(HOMEC)and Human Cervical Epithelial Cells,(HCerEC)as cell models,a variety of intracellular gene silencing,knockdown,knockout and overexpression techniques were used to regulate the activity of Hippo / YAP signaling pathway in these cells.Then we tested the proliferation of these cells.We also detected intracellular cellular markers of senescence in these cells.We found that loss of YAP/TAZ inhibited proliferation in ovarian cells.However,overexpression of YAP also resulted in growth arrest in human primary epithelial,ovarian granulosa cells and endothelial cells of ovary.Phenotypes of these arrest cells were typically like cellular senescence.Retinoblastoma protein(pRB)and large tumor suppressor kinase 2(LATS2)were accumulated in YAP-overexpressed primary cells.Inactivation of either pRB or LATS2 can prevent YAP-triggered cellular senescence in primary ovarian cells.In addition,LATS2 was also up-regulated in replicative-induced senescent cells.Knockout of LATS2 diminished natural replicative-induced cellular senescence in primary cells.And overexpression of YAP resulted in growth arrest in human primary ovarian cells and induce cellular senescence.Our results supported the existence of a negative feedback loop involving YAP and its upstream suppressor LATS2 in regulating the cellular senescence.When YAP wall activated abnormally,it will negatively feedback to increase its upstream inhibitory gene,LATS2,to reverse the activity of YAP.And LAPS2 activation due to sustained overactivation of YAP will induce cell aging.Therefore,maintaining the dynamic balance of the Hippo / YAP signaling pathway is critical to ensuring the normal functioning of the various cells in the ovary.This study revealed the critical role of Hippo/YAP signaling in physiological regulation of the ovaries.Our results are also important for understanding the basic biological functions of the Hippo / YAP pathway and provided useful information to regulate the reproductive activity in human and farm animals in future.