Pseudoislets as a model system to study beta cell dysfunction in diabetes

Insulin is an essential hormone made by islet beta-cells and reductions in its release cause diabetes. The importance of beta-cells in the development of diabetes means that much research is focused on studying their function, or on using islets/beta-cells to test new diabetes therapies. This is valuable and has led to new drug development and to novel transplantation methods to treat diabetes. The most common source of islets for these studies is laboratory animals, particularly rats and mice, and we estimate that this accounts for the use of tens of thousands of these animals each year. This project proposes to allow a substantial reduction in the numbers of animals required by developing alternatives to islets taken from animals.
We already have a variety of animal-derived hormone-producing cells that have been modified so that they grow continuously in tissue culture without the need for using more animals. However, islets are complicated organs in which interactions between cells are very important for their function ? when the cells are grown in isolation they no longer behave normally, and so their usefulness for experiments is limited. We have spent several years investigating interactions between islet cells to find out how to put the cells together to form islet-like structures (pseudoislets) so they perform like normal islets: our current pseudoislet model is much better than the original cell lines, but it is not yet as good as a real islet. We now propose to improve pseudoislet function further through a defined series of experiments and the impact of this model to the 3Rs will be in replacement of animals that would otherwise be used as a source of primary pancreatic islets.
Since the development of our current pseudoislet model we have routinely used pseudoislets, rather than islets taken from animals, in our studies of insulin secretion and we have published these studies in first class, peer-reviewed scientific journals. We have also introduced the pseudoislet model into the laboratories of some of our collaborators, but we acknowledge that the scientific community is inherently conservative so an important part of our application is directed towards a programme of dissemination of the results of the studies to investigators who currently use experimental animals as a source of islets. We propose that this will maximize the impact of our project on the replacement of animals that would otherwise be used for islet isolation.

Islets of Langerhans are aggregates of endocrine cells dispersed throughout the pancreas. The majority of islet cells are insulin-secreting beta-cells, but islets also contain glucagon-secreting alpha-cells and somatostatin-secreting delta-cells. The importance of pancreatic beta-cell function in the development of diabetes mellitus, and the search for new therapies for diabetes, has driven a great deal of research into every aspect of islet/beta-cell biology. This area of research has been greatly assisted by the development of methods for isolating islets from experimental animals (predominantly rodents), but this has required the use of a considerable number of animals - we calculate that data published from islet studies in 2006 alone may have used 30-40,000 rodents as a source of islets. This project proposes to reduce the numbers of animals used by developing useful in vitro substitutes for primary islets. A number of rodent islet hormone-secreting cell lines are currently available, but they lack the differentiated functions of primary islets, which limits their usefulness in many studies. We have demonstrated that the function of insulin-secreting cell lines is much improved by configuring them as three-dimensional islet-like structures (which we call pseudoislets), and we have now incorporated a glucagon-secreting cell line (alphaTC1) into the pseudoislet model ? preliminary results show that our endocrine cell lines retain ability to self-organise into anatomically-appropriate islet-like structures, and that this is important for their function. We have also demonstrated that interactions through cell-surface adhesion molecules influence the proliferative capacity and the differentiated function of cells within pseudoislet structures, suggesting that islet-like structures generated in vitro can offer a viable experimental alternative to islets isolated from experimental animals. We propose a series of studies to refine the pseudoislet model to ensure that it more closely approximates a mouse primary islet in anatomy and function such that it offers a valid alternative to islets in many experimental protocols. We also propose an extensive programme of dissemination of information to UK and international groups that currently use animals as their source of islet material for experiments. The impact of this model to the 3Rs will be in Replacement of animals that would otherwise be used as a source of primary pancreatic islets of Langerhans.