( ouldeasily use this technique with any...)Priming embryonic stem cells to fulfill their promise

ould easily use this technique with any other tissue in mouse, or human, or any other species," said Bhatia. Scientists have identified about 100 proteins - including laminin, fibronectin, and several kinds of collagen - that function as the extracellular matrix, or scaffolding, of most mammalian tissues. Until now, there has been no practical way to evaluate the daunting number of possible combinations of these proteins, any one of which could form the optimal "niche" for a desired type of differentiated cell. In their experiments, the UCSD researchers took advantage of the knowledge that the extracellular matrix in liver is comprised primarily of just five proteins. They applied spots of all 32 possible combinations of the five proteins as engineered niches onto the surface of gel-coated slides, and then added mouse embryonic stem cells to the niches. After the cells were allowed to grow, the researchers assayed their progression into liver cells. "We looked at all the combinations at once," said Bhatia. "Nobody has done this combinatorial approach before." Bhatia, Chien, and Flaim reported that either collagen-1 or fibronectin had strongly positive effects on the differentiation of the stem cells they tested. Unexpectedly however, when both collagen-1 and fibronectin were combined in one niche, the liver cell differentiation rate was subtly inhibited. "You would not predict that from the customary cell biology experiments," said Bhatia. "By using this combinatorial technique we were surprised to find many interesting interactions, and we were able to tease out the effects of each protein, alone and in combination with others." Cell biologists have not performed such combinatorial assays for other desired cell types because they have no practical way to do so. Bhatia, Chien, and Flaim seized on the unique ability of so-called DNA spotting machines to deliver tiny volumes of liquid, about one trillionth of a liter per spot. The spotting machines, which cost as litt
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Source:Eurekalert


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