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Modelling bone remodelling

2015 03 13

Qinghua Qin. Photo by Stuart Hay.

Osteoporosis is a debilitating disease. As the bones become thinner and less dense, they become exceedingly fragile. Painful fractures and breaks are a constant risk. 

Luckily, bones are pretty amazing structures. They have a remarkable capacity for remodelling.

If a piece of bone lost in a sheep, for example, is replaced with a piece of plastic, the bone will soon regrow around, and eventually absorb, the artificial portion of limb.

Professor Qinghua Qin and his team at ANU are using NCI’s supercomputing facilities to work out exactly how this process works.

The aim is to slow down or prevent entirely the insidious progression of osteoporosis.

“There is a strong link between inactivity and loss of bone mass,” explains Qin.

“People need sports and movement to keep their bones strong.

“We are using mathematical modelling to describe the process of bone degradation and establish the relationship between movement and bone density.”

There are two major types of cells involved in bone regrowth: osteoblasts and osteoclasts. Osteoblasts form bone cells, while osteoclasts absorb old bones and dissolve bone cells to reconstruct the shape of the bone.

“All bone remodelling at a cellular level is related to these two sorts of cells,” says Qin’s PhD candidate, Song Chen.

“Currently we are using the Raijin supercomputer to model the interaction between these two cells to predict how they proliferate.”

The team is collaborating with orthopaedic surgeon Professor Paul Smith’s team at the ANU Medical School.

Smith’s team collects bone samples of disease model from The Canberra Hospital and the two teams culture bone cells at The John Curtin School of Medical Research. Qin’s teamthen take 3D scans of the selected samples using the ANU Department of Applied Mathematics’ custom CT machine.

“We can use the CT machine to generate very high resolution images of the bone, which we can then turn into numerical data, including density and porosity, for computer simulation,” explains Qin.

“These high resolution images may take up more than 10GB each. That’s why we need a supercomputer.”

Intriguingly, another of Qin’s students – Jin Tao – is using a similar technique to delve into the microstructure of willow and ash wood, popular for sporting equipment like cricket and baseball bats.

“Currently I am using the CT facilities to look at wood microstructure, which is quite similar to bone,” says Tao.

“We have equipment that enables us to compress a piece of wood or drop something on it from a height while we’re taking the scan so we can analyse the same piece of wood before and after impact to see which species are most suited to certain sporting activities.”

Using similar before and after scans, Qin and Chen hope to gather insight into the benefits and disadvantages for bone density of different types of exercise and movement.

“Some sports are very useful for strengthening the bone,” says Qin.

“But other movements can be quite harmful. We are hoping to discover what works and what doesn’t.”

The next step for the team is to move from the cell level to the gene level.

“We already know that the main problem in osteoporosis is that the osteoblasts slow down production of new bone cells,” Qin says.

“Now we want to look at the genes involved and find out which genes are being up- or down-regulated to cause this.

“The long-term aim is to be able to screen people and tell them their likelihood of developing osteoporosis down the track.

“Because it is a slow-developing disease – appearing over a decade or more – the earlier we can intervene, the better.”

 

 

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