WASHINGTON - Researchers have derived embryonic stem (ES) cells from rats, a breakthrough that will enable scientists to create far more effective animal models for the study of a range of human diseases.

‘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,’ said Qi-Long Ying.

‘The research direction of many labs around the world will change because of the availability of rat ES cells,’ added Ying, assistant professor of cell and neurobiology at the Keck School of Medicine of University of Southern California (USC) 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 said. ‘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.’

Embryonic stem cells are derived from a group of cells called the inner cell mass in a very early stage embryo. ES cells provide researchers with a valuable tool to address fundamental biological questions, because they enable scientists to study how genes function, and to develop animals with conditions that mimic important human diseases.

The first ES cell lines were established from mice in 1981 by Martin Evans of Cardiff University, who was last year awarded the Nobel Prize in Medicine.

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.

The research was published in the Friday issue of Cell.