The physiological role of calcitonin and its receptor in bone cell metabolism.

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Throughout adult life, bone tissue is continuously remodelled. The two main processes involved in bone remodelling, are bone formation and bone breakdown. Bone formation is controlled by cells known as osteoblasts and bone breakdown is controlled by cells known as osteoclasts. Under normal circumstances these two processes are tightly coupled. Excessive breakdown of bone, causes these two processes to become unbalanced and results in bone loss. This is the basis of many bone diseases such as osteoporosis, a condition in which the bones become fragile and therefore more susceptible to fracture. 1 in 2 women and 1 in 3 men aged 70 years and older suffer from osteoporosis in Australia. Despite this, the mechanisms which control osteoclast breakdown of bone are not well understood. Our laboratory is interested in how hormones affect osteoclast action. We plan to examine the role of the hormone calcitonin, an important inhibitor of osteoclastic bone breakdown. This will be achieved by studying transgenic mice in which the receptor, or target, for calcitonin is specifically removed from osteoclasts. This will allow us to precisely determine the role of calcitonin in osteoclast function. Data generated by our research group indicates that calcitonin is also involved in controlling bone formation, however, the way in which calcitonin acts on osteoblasts remains poorly understood. Therefore, studying our transgenic mice will also help clarify the role calcitonin plays in bone formation. Current treatment for osteoporosis involves the administration of drugs which inhibit bone breakdown. This project will increase our understanding of how calcitonin acts to regulate bone breakdown and bone formation and may assist in the design of new therapies for osteoporosis. We believe that this research is of great importance as osteoporosis is becoming more prevalent as the population ages.