A good demonstration of the state of the art of tissue engineering: "Last spring, a research team at Japan's RIKEN Center for Developmental Biology created retina-like structures from cultured mouse embryonic stem cells. This week, the same group reports that it's achieved an even more complicated feat - synthesizing a stem-cell-derived pituitary gland. The pituitary gland is a small organ at the base of the brain that produces many important hormones and is a key part of the body's endocrine system. It's especially crucial during early development, so the ability to simulate its formation in the lab could help researchers better understand how these developmental processes work. ... The experiment wouldn't have been possible without a three-dimensional cell culture. The pituitary gland is an independent organ, but it can't develop without chemical signals from the hypothalamus, the brain region that sits just above it. With a three-dimensional culture, the researchers could grow both types of tissue together, allowing the stem cells to self-assemble into a mouse pituitary. ... Using this method, we could mimic the early mouse development more smoothly, since the embryo develops in 3-D in vivo. ... Fluorescence staining showed that the cultured pituitary tissue expressed the appropriate biomarkers and secreted the right hormones. The researchers went a step further and tested the functionality of their synthesized organs by transplanting them into mice with pituitary deficits. The transplants were a success, restoring levels of glucocorticoid hormones in the blood and reversing behavioral symptoms, such as lethargy."