A project grant from the NC3Rs helped Dr Alastair Sloan, from the University of Cardiff, to develop a new ex vivo mouse model of periodontal disease.
Principal Investigator: Alastair Sloan, Reader in Bone Biology and Tissue Engineering
Organisation: University of Cardiff
Award: £193,680, in 2007, over 24 months
Title: Development of a new ex vivo mouse model of periodontal disease
Read more about Dr Sloan's research.
Over half of UK adults are affected by dental disease
Periodontal diseases are a group of chronic inflammatory diseases of the tissues which surround and support the teeth. The severity of the diseases ranges from mild and reversible inflammation of the gums to bone damage and tooth loss. Chronic inflammation of the periodontium is caused by the host immune response to the bacterial pathogens which form the subgingival biofilm (bacteria living just beneath the gums).
The most prevalent form of the disease is adult periodontitis which is the major cause of tooth loss in the developed world. In the UK, 54% of adults are affected by periodontitis with 85% of over 65s exhibiting periodontal destruction. The estimated cost to the NHS is £500 million annually. There is also a link between periodontal disease and increased risk of coronary heart disease, bacterial pneumonia and stroke.
A range of animals are used to study periodontal disease
A range of animals including rodents, dogs and nonhuman primates are used to study the pathogenesis of periodontal diseases and to develop and evaluate potential therapeutics. Disease is induced experimentally by tying a ligature around the tooth and either allowing disease to develop naturally or injecting bacteria into the ligatured area. Animal models have provided information on host/bacterial interactions, however, they are limited by differences in dental anatomy and oral microbiota and difficulties associated with translation to man. There are also animal welfare concerns, with most procedures of this type classified as moderate severity under the Animals (Scientific Procedures) Act 1986.
In vitro models using rodent cells are used to study some aspects of periodontal disease but without the complex cell/cell and host/bacterial interactions their use is limited.
Given the small tissue volume available from the rodent mandible (lower jaw), obtaining a sufficient quantity of viable cells can necessitate using large numbers of animals, typically 25 to 50 mice per study.
A new three-dimensional model of the lower jaw
With NC3Rs funding, Dr Alastair Sloan, Cardiff University, has developed and validated an ex vivo mouse model to study inflammation and bone metabolism in periodontal disease. The model mimics what happens in vivo, is more representative of disease progression than in vitro assays, and reduces animal use.
The three-dimensional model uses a slice culture of the mouse mandible which can be maintained for up to 21 days. The model maintains the in vivo cellular phenotypes and tissue architecture of the mandible and tooth. This includes odontoblasts (which secrete dentin, the layer under the tooth enamel), fibroblasts of the tooth pulp and the periodontal ligament (which secrete extracellular matrix proteins), bone marrow cells (which mainly give rise to haematopoetic cells, plus osteoblast progenitor cells and bone marrow stromal cells) and osteoclasts (which resorb bone). Importantly, it also includes immune cells such as monocytes, activated macrophages and neutrophils which are crucial to the development of periodontitis.
The ex vivo model mimics the in vivo response to exogenous factors such as inflammatory cytokines, with key hallmarks of disease progression, including increased bone resorption, cell death and cytokine induction, observed. The model is now being used to investigate bone repair and cellular/extracellular matrix interactions.
An 80% reduction in the number of mice used
A typical in vivo study of periodontal disease with five time points uses five animals per time point.
Ten mandibular slices can be obtained from a single mouse and this means that with the ex vivo model there is an 80% reduction in the number of animals used. The ex vivo model also uses 96% fewer mice than the in vitro assays.
Prize winning scientist
There have been two publications arising from this grant so far. In 2011 Dr Sloan was given the International Association for Dental Research’s Distinguished Scientist, Young Investigator Award, in recognition of his work, including that funded by the NC3Rs.
The ex vivo model has been adopted by groups at the University of Alberta in Canada, Baylor College of Dentistry in the USA, and in the UK by the University of Central Lancashire. It has also been used by a large pharmaceutical company for a commercial study.
This case study was published in a review of our research portfolio in September 2011.