Growing Stem Cells Into Lung Tissue
An example of work that lays the foundations for lung tissue engineering, which has been lagging behind advances for other organs: "How do you grow stem cells into lungs? The question has puzzled scientists for years. First you need the right recipe, and it took [researchers] seven years of trial and error and painstaking science to come up with it. ... Some tissues, like muscle and nerves, are relatively easy to grow, but others, including liver, lung, thyroid, and pancreas, have been much more difficult. These troublesome tissues all spring from the endoderm, the innermost layer of an early embryo. The endoderm forms when an embryo is about three weeks old and differentiates into organs as early as five weeks. Somehow, in these two weeks the endoderm transforms into differentiated organs as diverse as the lungs and the stomach. ... [Researchers] decided to create a knock-in reporter gene that would glow green during the 'fate decision' - the moment when the stem cells expressed a gene called Nkx2-1 and thereby took a step toward becoming lungs. This allowed the team to track the cells as they developed, mapping each of the six critical decisions on the path to lung tissue. ... Once [the] team had grown what appeared to be lung cells, they had to make sure they had the recipe right. They took samples of mouse lungs and rinsed them with detergent until they became cell-free lung-shaped scaffolds. They seeded one lung with 15-day-old homegrown lung cells that they had purified from stem cells. As a control, they seeded another lung with undifferentiated embryonic stem cells. Within 10 days after seeding, the lung cells organized themselves and populated the lung, creating a pattern recognizable [as] lung tissue. ... A happy side effect of the discovery was that the scientists also mapped out the road from stem cell to thyroid. [The] thyroid, it turns out, also comes from the endoderm layer, deriving from a progenitor that expresses the same key gene as lung progenitors. [The] work will likely have a huge impact on lung stem cell researchers, who have been waiting for a discovery like this to propel their research on inherited lung disease."
Link: http://www.bu.edu/today/2012/from-stem-cells-to-lung-cells/