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Regenerating organs from scratch

Tony Atala, MD, was the guest speaker yesterday at Stanford's 5th annual Oscar Salvatierra, Jr., M.D. lecture in transplantation. Atala, a pediatric urologist and the director of the Wake Forest Institute for Regenerative Medicine in Winston-Salem, NC, is a highly regarded tissue-engineering pioneer. He and his colleagues are now growing more than 20 types of tissues, with some notable successes in delivering them to patients with failing or defective organs.

In general, the approach involves creating a scaffold that can be seeded either with the patient's cells, if those of the appropriate type can be harvested, or with stem cells.

The scaffold itself can be the collagenous extracellular matrix of a donor organ whose cells have been removed with detergents, or it can be a wholly artificial construct - Atala's team has been able to create off-the-shelf organ scaffolds using a desktop inkjet printer. The printer is modified to spray not ink but a cell-filled gel, layer by layer, according to a computer program. The output is an intricate three-dimensional structure. When fetal cardiomyocytes - the cells that compose heart muscle - were seeded onto a heart-specific scaffold generated this way, the resulting entity started beating within four hours, Atala told his attentive audience.

As for which kinds of starter-material cells to use, Atala spoke in some detail about a promising class of stem cells isolated from amniotic fluid and placenta. These cells seem somewhat more mature than either embryonic stem (ES) cells or induced pluripotent stem (iPS) cells. Yet they multiply robustly and have, so far, been shown capable of differentiating into bone, cartilage, liver, lung, kidney, blood, pancreatic beta cells, intestine and cardiac and endothelial tissues. On the other hand, they do not form teratomas or tumors, a major drawback of both ES and iPS cells. Cherry on the sundae: They appear to suppress immune rejection.

Sounds like progress to me.

I've said it before. One reason I love my job so much is that it's the opposite of writing obituaries.

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