Back to the Mouse

For the last couple of months, the pages of Lab Animal have been filled with articles dealing with some of the so-called 'exotic' species being used in biomedical research. From the Nile grass rat's diurnal lifestyle to the axolotl's amazing regenerative capacity, these animals can provide research opportunities not available with more conventional species. This month we step away from these odd creatures and go back to taking a look at biomedical research's most important model—the mouse.

Since the Animal Welfare Act does not cover rats and mice, the exact number of these animals used in research each year is difficult, if not impossible, to get a handle on. A recent report¹ by the National Academies' Committee on Increasing Veterinary Involvement in Biomedical Research estimated that in 1998 approximately 23 million rats and mice were used in biomedical research. The group predicts that mouse use alone will continue to increase by 10–20% annually over the decade 2000–2010. Others estimate that as many as 60 million mice will be needed to study the function of every gene in the mouse genome².

In this issue, we get a detailed look at the mouse models that are being used to study two of today's most significant threats to public health—obesity and infectious disease.

There is no doubt that obesity is increasing in the developed world, with today's culture of leisure and excess combining to cause much of the weight problem we see today. Despite the prodigious number of diets out there—from low-carbohydrate, to low-fat, to diets based on consumption of fast-food sandwiches—there is a large segment of the population that just cannot seem to maintain a healthy weight. Fortunately, there are more than 50 transgenic, knockout, and spontaneous mouse models of obesity available, and these animals are providing valuable insights into the genetic and hormonal underpinnings of this extremely common problem. On p. 30, Deborah J. Good presents an overview of the special considerations involved in caring for obese rodents, both for personnel and for IACUC members charged with reviewing protocols involving these animals.

Some in the medical field were declaring victory over infectious disease as far back as the 1960s, but the emergence of antibiotic-resistant strains of bacteria and new viral pathogens, such as the hepatitis C virus (HCV), has proven these optimists terribly wrong. Although hepatitis C was not recognized as a distinct disease until 1975, and the causative virus was not isolated until 1989, current estimates suggest that 170 million people worldwide are now infected. There are no particularly effective treatments, and the grim prognosis for those chronically infected—many of whom are destined to develop cirrhosis and liver cancer—has created an urgent need for additional research into HCV. Chimpanzees are the only animals that are naturally susceptible to HCV, but there are ethical and economic hurdles to using this species to study disease progression and treatment options. A number of groups have developed alternative models, including transgenic mice, and mice with human-mouse chimeric livers. On p. 39, Chandan Guha and colleagues review the animal and cell culture models that are currently being used to learn more about how to prevent HCV from spreading, and how to treat those people already infected.