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Genetic Linkage

Stem Cell Ups and Downs

We expect too much of stem cells. The February 3 issue of Nature reveals both a setback and a stupendous achievement in the field.

An article in the news section takes induced pluripotent stem cells (iPS cells) down a notch or two. The genes of the "reprogrammed" cells retain methylation patterns of the “adult” cells from which they were derived. In other words, they aren’t exactly like embryonic stem cells because they bear echoes of their origins. This might complicate eventually putting them into people – you wouldn’t want your made-to-order gallbladder suddenly becoming a stretch of skin.

But in a technical report at the back of the journal is a recipe for a “human intestinal organoid.” Researchers at the University of Cincinnati took samples of multi-purpose skin fibroblasts and washed them in a series of growth factors that would normally bathe an embryo – like a developmental drive-through car wash. The cells sucked up the growth factors and then proceeded to undulate themselves into snippets of small intestine, forming the perfect tiny hills and valleys of intestinal villi and crypts, complete with lining cells that absorb nutrients and the occasional goblet cell that keeps matters mucosy moist. The gut-in-a-dish even had its very own stem cells.

The intestinal organoids courtesy of stem cells may fill a gap between cells-in-a-dish to study drugs, and sticking stem cells into sick people to heal them. Researchers created bits of an organ that is three-dimensional and works. Applications boggle the mind.

We can watch irritable bowel syndrome and Crohn's disease start. We can see how a birth defect like a short bowel arises. Perhaps most importantly, we can use the tiny intestines to study how drugs are absorbed. And none of this involves embryos or the fetal factories of Aldous Huxley’s Brave New World.

So maybe we’ve got our priorities skewed. Instead of expecting stem cells to replace body parts, instead of hollering that deriving them kills embryos, we should use them to recreate bits of our bodies in a controlled laboratory situation so we can understand how we become ill – and what we can do about it.
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