Morphing cells into body parts

Scientists at NUI Galway have made it on to the front cover of a prestigious journal with their research into controlling ‘tissue engineering’

MECHANICAL engineering and biology merge in the field of tissue engineering. Researchers blend the expertise used for many years to design aircraft wings and apply it to the smallest of body parts, an individual cell.

By its very nature tissue engineering is exceptionally multidisciplinary, says Prof Peter McHugh who heads NUI Galway’s department of mechanical and biomedical engineering. He and PhD candidate Adam Stops joined Prof Patrick Prendergast and Dr Louise McMahon in Trinity College Dublin’s centre for bioengineering in a research project that reflects the complexity of tissue engineering.

Their work has had a huge impact, providing the cover story in the current issue of the Journal of Biomechanical Engineering, published by the American Society of Mechanical Engineers. “The project fits into the whole area of tissue engineering and regeneration,” says McHugh, who is also the research cluster leader for biomechanics within Galway’s National Centre for Biomedical Engineering Science.

It is all about growing skin, tendon, cartilage or muscle in the lab for use as replacement tissue after loss or injury. It has huge potential given the original cells would come from the recipient and so there is no question of tissue rejection.

McHugh acknowledges however that the techniques are still in development. “Tissue engineering is a little futuristic in that it isn’t something on the shelves yet,” he says.

Even so, researchers have learned a great deal about culturing cells and growing them in the lab. They are usually seeded into “scaffolds”, tiny porus structures that hold the cells but allow growth promoting nutrients to reach them, explains McHugh.

It is not enough simply to grow them however. Skin and tendon expand and compress, stretch and twist and research has shown that cells grow and proliferate better when they are put under stresses and strains.

But what was the best way to apply these forces and at what strength to achieve the best possible growth? And how could the the actual forces experienced by the cells be measured?

These were the research questions answered by the NUIG/TCD team. Working with funding from the HEA’s Programme for Research in Third Level Institutions, the researchers developed a model that could predict the forces placed on the cells by compressing the scaffold. It used “advanced finite element analysis”, long applied by mechanical engineers to gauge forces on individual components in aircraft and other applications.

“The idea is we would use biomechanical and bioengineering to see what forces the cells are experiencing. For example how far was the cell being stretched? Our model takes that down to what the individual cells feel,” McHugh says. Advanced imaging was also used so that the cells could be seen inside the scaffold. “You can get very detailed images of the scaffold and where the cell might be within it.”

The model can now predict forces applied to the cells and effectively “allows you to join the dots” when studying their response, he explains. The model predicts the forces that come to bear on the cells depending on the pressure applied to the scaffold. This helps identify the most promising options for actual cell growth. “It also allows you to provide calculations that wouldn’t be available otherwise, for example the pressures on individual cells,” he adds.

The next step will be to enhance the model to make predictions about how well cells will grow when put under specific stresses. The Royal College of Surgeons in Ireland will also participate in this next step, building on existing collaborations between biomedical and biomechanical researchers.