Self-Renewing Trophoblast Organoids Recapitulate the Developmental Program of the Early Human Placenta

Abstract

Summary: Defective placentation is the underlying cause of various pregnancy complications, such as severe intrauterine growth restriction and preeclampsia. However, studies on human placental development are hampered by the lack of a self-renewing in vitro model that would recapitulate formation of trophoblast progenitors and differentiated subtypes, syncytiotrophoblast (STB) and invasive extravillous trophoblast (EVT), in a 3D orientation. Hence, we established long-term expanding organoid cultures from purified first-trimester cytotrophoblasts (CTBs). Molecular analyses revealed that the CTB organoid cultures (CTB-ORGs) express markers of trophoblast stemness and proliferation and are highly similar to primary CTBs at the level of global gene expression. Whereas CTB-ORGs spontaneously generated STBs, withdrawal of factors for self-renewal induced trophoblast outgrowth, expressing the EVT progenitor marker NOTCH1, and provoked formation of adjacent, distally located HLA-G+ EVTs. In summary, we established human CTB-ORGs that grow and differentiate under defined culture conditions, allowing future human placental disease modeling. : Failures in human placental development have been associated with severe pregnancy complications. However, due to the lack of a self-renewing model system, mimicking 3D in vivo growth and differentiation of placental trophoblast, the underlying mechanisms remain poorly understood. Herein, long-term expanding trophoblasts organoids were established that proliferate and differentiate under defined culture conditions allowing investigating normal and pathological placentation. Key words: human placenta, cytotrophoblast organoids, self-renewal, extravillous trophoblast lineage, differentiation, cell fusion, Wnt signalling