WASHINGTON, Dec. 24 (Xinhua) -- Researchers at the University of Southern California (USC) have, for the first time, derived authentic embryonic stem (ES) cells from rats.

    This breakthrough finding will enable scientists to create far more effective animal models for the study of a range of human diseases, the university said in a press release on Wednesday.

    The research will be published on the Dec. 26 issue of the journal Cell.

    "This is a major development in stem cell research because we know that rats are much more closely related to humans than mice in many aspects of biology. The research direction of many labs around the world will change because of the availability of rat EScells," says Qilong Ying, a native of China and the study's principal investigator.

    The finding brings scientists much closer to creating "knockout" rats -- animals that are genetically modified to lack one or more genes -- for biomedical research. By observing what happens to animals when specific genes are removed, researchers can identify the function of the gene and whether it is linked to a specific disease.

    "Without ES cells it is impossible to perform precise genetic modifications for the creation of the disease model we want," he says. "The availability of rat ES cells will greatly facilitate the creation of rat models for the study of different human diseases, such as cancer, diabetes, high blood pressure, addiction and autoimmune diseases."

    The first ES cell lines were established from mice in 1981 by Martin Evans of Cardiff University, Britain, who was last year awarded the Nobel Prize in Medicine or Physiology. Researchers have long been working on establishing rat ES cells, but faced technical hurdles because the conventional methods developed for the derivation of mouse cells did not work in rats.

    Building on recent research into how ES cells are maintained, the USC researchers found that rat ES cells can be efficiently derived and grown in the presence of the "3i medium," which consists of molecules that inhibit three specific gene signaling components. This approach insulates the stem cell from signals that would normally cause it to differentiate. By blocking these signals, the researchers found that stem cells from rats, which have previously failed to propagate at all, could be grown indefinitely in the laboratory in the primitive embryonic state.

    Researchers at USC are currently working on generating the first gene knockout rat through ES cell-based technologies. "If our work is feasible it is likely that many labs will follow up to generate different types of gene knockout rat models," he says. "This will have a major impact on the future of biomedical research."