A device that successfully recapitulates key processes following human embryo implantation may improve our understanding of early human embryonic development. The system, described in Nature this week, circumvents bioethical issues associated with studying human embryos by using human pluripotent stem cells (PSCs) in a carefully controlled environment.
Efforts to study early embryo development after implantation into the uterus have been limited by suboptimal cell culture protocols and bioethical guidelines prohibiting the use of cultured human embryos beyond 14 days post-fertilization. Human and mouse PSCs (which can differentiate into specialized cell types) have been used to model post-implantation embryonic development, but such systems have had limited success in reproducing crucial developmental events.
Jianping Fu and colleagues demonstrate a controllable environment for culturing human PSCs that can improve the efficiency and reproducibility of synthetic model systems. They have developed a microfluidic device that comprises three channels: one for holding a material in which cells can embed, one for loading stem cells, and another for delivering factors to stimulate stem cell differentiation. The device enables the authors to control the differentiation of stem cells towards major cell lineages that arise in early human embryos, producing synthetic embryonic-like sacs. These sacs lack specific cell types needed to produce viable embryos. The authors also identify specific cell types that drive key events in embryo development.