Understanding the forces that shape our bones

TOO OFTEN WE don’t appreciate our skeleton until injury or age stops it working as well as it used to. But by better understanding the forces that shape our bones and joints, two new European-funded projects in Ireland aim to help keep us moving.

One study looks at the stresses and strains that help our bones function well, and is being led by Dr Laoise McNamara, a Science Foundation Ireland Stokes lecturer in biomedical engineering at NUI Galway.

She has secured €1.5 million in funding from the European Research Council to examine how mechanical forces, like stretching and pulling on cells, can affect our bones.

“We need to load our bones, we need to walk around, to climb stairs in order to keep bone healthy,” says McNamara. “So we are looking to understand how exactly are the cells able to monitor what sort of loads we are applying, how much we are walking and how heavy the weights are that we are lifting.”

Many questions remain about how exactly our bones respond to stresses – and why astronauts lose bone density when they spend extended time away from gravity. Getting new insights on the mechanobiology of bone could help shed light on health issues such as bone thinning, and on how hormones such as oestrogen affect cellular responses to forces, notes McNamara.

“Our understanding should give us an idea about what loading regimes should be appropriate at different stages during life and especially at the onset of osteoporosis – you could advise a patient of a strategy of exercise and loading, that could minimise bone loss,” she says.

Figuring out the kinds of mechanical environments that bone cells like to “see” should also help the team develop a bioreactor to grow new bone tissue in the lab for use in grafts.

“Biologists have come nowhere near being able to grow new bone in lab because they can’t get the cells to make strong bone tissue – it’s jelly-like and you wouldn’t be able to stand on it,” says McNamara. “So by understanding which cells are most appropriate, and what mechanical loads, how much we put on the cell or how much fluid flow we put over them, [we want] to try and develop a method to grow new bone in the lab.”

A separate project – also being funded by the ERC – will zone in on cartilage, a tissue that helps to cushion and protect joints between bones.

“At the moment if you present in a clinic with pain in your knee with damaged cartilage there are very limited treatment options available to surgeons,” explains Dr Daniel Kelly from Trinity College Dublin’s school of engineering.

He is looking to develop a rapid way of encouraging the patient’s own stem cells to do the rebuilding work.

Using microbeads to isolate adult stem cells from a biopsy of the fat pad in the patient’s knee, the proposed approach then seeds the stem cells onto a biological scaffold. A few hours after the procedure begins, the loaded scaffold is put back into the ailing joint and grows cartilage in situ.

“My big thing is understanding how environmental factors inside the joint are going to affect the cartilage repair tissue,” says Kelly, whose five-year study will also look to develop ways of growing cartilage in the lab to address larger injuries or defects.

“People have much higher expectations now, they want to be more active as they age,” he says. “Anything we can do that will delay or hopefully prevent the need for a total knee or hip prosthesis obviously has massive benefits in terms of quality of life.”