Mice are an important tool in biomedical research, particularly when it comes to testing possible new drugs, says 80beats' Joseph Castro. But when it comes to testing drug side effects, they're not always accurate — mouse livers and human livers react differently to pharmaceutical compounds. But in a new study published in PNAS, researchers at MIT say they've found a solution, Castro says: implanting mice with miniature, humanized livers. The team first developed tissue scaffolds by combining hepatocytes with other mouse and human cells. Once the scaffolds were implanted into the mice's abdominal cavities, the livers took about a week to integrate fully into the mice, Castro says. In addition to more accurately predicting drug toxicity, the researchers think the new livers will help scientists find treatments for diseases like hepatitis C, which mice don't normally contract, he adds.