Intermediate Conductance Calcium Activated Potassium Channel is Critical to Balance Trophoblast Development During Human Placentation.

ASEF JAWAD NILOY¹; Rajnish Kumar¹; Purbasa Dasgupta¹; Namrata Roy¹; Soma Ray¹; and Soumen Paul¹.

            ¹Institute for Reproductive and Developmental Sciences. Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, Kansas, KS 66160, USA.

Abstract Text: Successful outcome of human pregnancy relies on precisely controlled cytotrophoblast proliferation and differentiation to syncytiotrophoblasts. The syncytiotrophoblast cells are crucial to ensure transfer of nutrients between the mother and the fetus. Another major function of syncytiotrophoblast cells is to regulate ion transport. However, the importance of potassium ion channels that regulate potassium ion transportation in trophoblast cells during human placentation is poorly defined. In this study, we focused on the importance of the intermediate conductance calcium activated potassium channel (IK_ca) in cytotrophoblast proliferation and syncytiotrophoblast differentiation processes. We found that IK_ca channel and KCCN4 gene, are expressed in both cytotrophoblasts and syncytiotrophoblasts within a 1^st trimester human placenta with a higher expression in syncytiotrophoblasts. Similarly, IK channel is expressed more in the syncytiotrophoblast cell culture. Genetic depletion as well as pharmacological inhibition of IK_ca channel inhibits human trophoblast stem cell proliferation and hinders organoid formation. Genetic depletion reduces key human trophoblast stem cell proliferation regulating genes ELF5, ITGA6 and GATA2. Interestingly, the activation of IK_ca channel also reduces human trophoblast stem cell proliferation and it accelerates syncytiotrophoblast differentiation. Mechanistic analyses revealed that the activation of IK_ca channel in human trophoblast stem cells reduces expression of Wnt4 and Wnt7A, which are key regulators of human trophoblast stem cell self-renewal process. In contrast, the activation of IK_ca channel promotes expressions of syncytiotrophoblast -specific genes, retroviral gene ERVW-1, transcription factor GCM1 and pregnancy hormone hCG-beta. Overall, our results provide a novel insight regarding human trophoblast development in which balanced function of the IK_ca channel provides critical balance of cytotrophoblast proliferation and activation of the channel promotes differentiation to syncytiotrophoblast cells.