MIT: 'Micro' livers could aid drug...( CAMBRIDGE Mass.--MIT researchers hav...)

CAMBRIDGE, Mass.--MIT researchers have devised a novel way to create tiny colonies of living human liver cells that model the full-sized organ. The work could allow better screening of new drugs that are potentially harmful to the liver and reduce the costs associated with their development.

Liver toxicity is one of the main reasons pharmaceutical companies pull drugs off the market. These dangerous drugs slip through approval processes due in part to the shortcomings of liver toxicity tests. Existing tests rely on liver cells from rats, which do not always respond to toxins the way human cells do. Or they rely on dying human cells that survive for only a few days in the lab.

The new technology arranges human liver cells into tiny colonies only 500 micrometers (millionths of a meter) in diameter that act much like a real liver and survive for up to six weeks.

Sangeeta Bhatia, associate professor in the Harvard-MIT Division of Health Sciences and Technology (HST) and MIT's Department of Electrical Engineering and Computer Science, and HST postdoctoral associate Salman Khetani describe their model liver tissue and its behavior in the November 18 online issue of Nature Biotechnology.

To build these model livers, Khetani uses micropatterning technologythe same technology used to place tiny copper wires on computer chipsto precisely arrange human liver cells and other supporting cells on a plate. Khetani adapted this method from Bhatias early work as an HST graduate student building micropatterned co-cultures of rat liver cells and supporting cells.

Such precisely arranged cells results in what Bhatia calls a high-fidelity tissue model because it so closely mimics the behavior of a human liver. For example, each model organ secretes the blood protein albumin, synthesizes urea, and produces the enzymes necessary to break down drugs and toxins.

To predict how close their model tissue is to real liver tissue, w
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