Inducible SAA transgenic mice: a refined model of human amyloidosis
Lead Research Organisation:
University College London
Department Name: Cell and Developmental Biology
Abstract
Amyloidosis is the name for a group of diseases caused by abnormal aggregation and build-up of certain proteins (amyloid) in various organs throughout the body. Amyloid interferes with organ function and is frequently fatal. About one in a thousand people in the UK die from generalised (systemic) amyloidosis, and a localised build-up of amyloid also occurs in some common disorders including the brain in Alzheimer?s disease and the pancreas in type II diabetes. There is presently no specific treatment for amyloidosis, although a number of drugs are in development.
About 5% of patients with chronic inflammatory diseases such as rheumatoid arthritis develop a type of amyloid called AA amyloidosis, which causes kidney failure and often death. AA amyloidosis also occurs in wild and farmed animals that have inflammatory disorders. It is caused by the presence of very high levels of a blood protein called SAA, which accompanies inflammation.
Mice with inflammation develop AA amyloidosis after about two months, and the mouse model of AA amyloidosis has been studied for over 50 years. It closely resembles human amyloidosis, and remains a vital and widely used model for studying the effects of new treatments. Indeed, proof of efficacy in mouse AA amyloidosis is a necessary milestone in the development of anti-amyloid drugs, and no suitable test tube models exist.
The experimental induction of mouse AA amyloidosis requires persistent inflammation for two months or more produced by daily injections of substances that cause inflammation in the skin. This is a moderately severe procedure.
It is self-evident that daily injections of inflammatory substances for many weeks are undesirable on welfare grounds. We therefore propose to generate transgenic mice that will massively overproduce SAA when given a specific simple dietary supplement. The availability of mice in which SAA production can be increased from healthy trace levels to very high levels without the need for any inflammation should enable the induction of amyloidosis to be achieved reliably and consistently without recourse to administration of toxic inflammation-provoking substances, and will provide much new information on amyloidosis.
We hope that this project will ultimately enable the present invasive method for inducing mouse amyloidosis to be abandoned completely by colleagues throughout the world.
About 5% of patients with chronic inflammatory diseases such as rheumatoid arthritis develop a type of amyloid called AA amyloidosis, which causes kidney failure and often death. AA amyloidosis also occurs in wild and farmed animals that have inflammatory disorders. It is caused by the presence of very high levels of a blood protein called SAA, which accompanies inflammation.
Mice with inflammation develop AA amyloidosis after about two months, and the mouse model of AA amyloidosis has been studied for over 50 years. It closely resembles human amyloidosis, and remains a vital and widely used model for studying the effects of new treatments. Indeed, proof of efficacy in mouse AA amyloidosis is a necessary milestone in the development of anti-amyloid drugs, and no suitable test tube models exist.
The experimental induction of mouse AA amyloidosis requires persistent inflammation for two months or more produced by daily injections of substances that cause inflammation in the skin. This is a moderately severe procedure.
It is self-evident that daily injections of inflammatory substances for many weeks are undesirable on welfare grounds. We therefore propose to generate transgenic mice that will massively overproduce SAA when given a specific simple dietary supplement. The availability of mice in which SAA production can be increased from healthy trace levels to very high levels without the need for any inflammation should enable the induction of amyloidosis to be achieved reliably and consistently without recourse to administration of toxic inflammation-provoking substances, and will provide much new information on amyloidosis.
We hope that this project will ultimately enable the present invasive method for inducing mouse amyloidosis to be abandoned completely by colleagues throughout the world.
Technical Summary
Amyloidosis is a disorder of protein metabolism in which normally soluble proteins are deposited as insoluble fibrils. These amyloid fibrils disrupt the structure and function of affected tissues and lead to serious disease. Systemic amyloidosis is usually fatal and is the cause of about one per thousand deaths in developed countries. Several more common important diseases, including Alzheimer?s disease and type II diabetes, are associated with localized amyloid deposition. As yet, there are no specific treatments for any kind of amyloidosis, although a variety of promising pharmacological strategies are under development.
AA amyloidosis is the second most common type of systemic amyloidosis in man, occurring in up to 5% of patients with chronic inflammatory diseases. Inflammation dramatically increases production of serum amyloid A protein (SAA) by the liver. When SAA concentrations remain elevated for prolonged periods SAA can be converted into AA amyloid deposits, resulting in systemic AA amyloidosis.
By far the most widely used animal model of amyloidosis is murine AA amyloidosis, which very closely resembles human systemic AA amyloidosis. It is an invaluable model for the study of the pathogenesis of amyloidosis and for the evaluation of the new treatments, several of which are currently in development. There is no suitable in vitro model for such testing.
In the existing murine model, developed 60 years ago, SAA overproduction is induced by creating persistent inflammation. This requires daily subcutaneous injections of an inflammatory stimulant for up to several weeks, and more rapid induction of amyloid requires more aggressive agents.
We propose here to develop, using transgenic techniques, a greatly refined model of AA amyloidosis in which overexpression of an SAA-encoding transgene will be regulated by dietary manipulation (administration or withdrawal of the antibiotic doxycycline). We already have preliminary results suggesting that an appropriate degree of overexpression is feasible. The objectives of the project are (1) to optimise the transgenic overexpression of SAA, (2) to validate tet-regulatable SAA transgenic mice as a model of amyloidosis and (3) to prepare the model for dissemination. We anticipate that in addition to the welfare benefits, this model will be more consistent and less labour-intensive, advantages that will substantially advance development of new therapies and that it will largely replace existing less satisfactory methods.
AA amyloidosis is the second most common type of systemic amyloidosis in man, occurring in up to 5% of patients with chronic inflammatory diseases. Inflammation dramatically increases production of serum amyloid A protein (SAA) by the liver. When SAA concentrations remain elevated for prolonged periods SAA can be converted into AA amyloid deposits, resulting in systemic AA amyloidosis.
By far the most widely used animal model of amyloidosis is murine AA amyloidosis, which very closely resembles human systemic AA amyloidosis. It is an invaluable model for the study of the pathogenesis of amyloidosis and for the evaluation of the new treatments, several of which are currently in development. There is no suitable in vitro model for such testing.
In the existing murine model, developed 60 years ago, SAA overproduction is induced by creating persistent inflammation. This requires daily subcutaneous injections of an inflammatory stimulant for up to several weeks, and more rapid induction of amyloid requires more aggressive agents.
We propose here to develop, using transgenic techniques, a greatly refined model of AA amyloidosis in which overexpression of an SAA-encoding transgene will be regulated by dietary manipulation (administration or withdrawal of the antibiotic doxycycline). We already have preliminary results suggesting that an appropriate degree of overexpression is feasible. The objectives of the project are (1) to optimise the transgenic overexpression of SAA, (2) to validate tet-regulatable SAA transgenic mice as a model of amyloidosis and (3) to prepare the model for dissemination. We anticipate that in addition to the welfare benefits, this model will be more consistent and less labour-intensive, advantages that will substantially advance development of new therapies and that it will largely replace existing less satisfactory methods.