Using sound waves, researchers have turned stem cells into bone cells – a tissue engineering advancement that could one day help bone regeneration in patients who have lost bone to degenerative diseases or cancer.

Bone can be lost to disease, but regrowing or replacing lost bone cells often involves invasive and painful treatment. Now researchers looking at stem cells have come up with an innovative bone regeneration treatment harnessing the precision power of high-frequency sound waves.

Longevity.Technology: Although our bone density tends to stay stable until about the age of 50, with bone formation keeping up with bone breakdown, things take a turn for the worse with age. Bone breakdown begins to outpace bone formation and can cause osteoporosis, fractures and frailty, particularly in women who have undergone menopause.

Tissue engineering is an emerging field that is aiming to rebuild bone and muscle by harnessing the human body’s natural ability to heal itself. However, a key challenge in bone regeneration is the need for large amounts of bone cells that need to be able to thrive and flourish once they have been implanted in the target area. Previous experimental processes to change adult stem cells into bone cells have been built upon the use of complicated and expensive equipment, and, additionally, this therapy struggles with mass production and scalability, making widespread clinical application unrealistic.

Clinical trials attempting bone regeneration have so far mostly used stem cells that have been extracted from a patient’s bone marrow, which is an invasive and very painful procedure.

In a new study published in the journal Small, a research team from the Royal Melbourne Institute of Technology (RMIT University) demonstrate that stem cells treated with high-frequency sound waves turn into bone cells quickly and efficiently. Significantly, the treatment was shown to be effective on various different types of cells including stem cells derived from fat, which are far less painful to extract from a patient [1].

Co-lead researcher Dr Amy Gelmi, Vice-Chancellor’s Research Fellow at RMIT said the new approach was faster and simpler than other methods.

“The sound waves cut the treatment time usually required to get stem cells to begin to turn into bone cells by several days,” she said. “This method also doesn’t require any special ‘bone-inducing’ drugs and it’s very easy to apply to the stem cells. Our study found this new approach has strong potential to be used for treating the stem cells, before we either coat them onto an implant or inject them directly into the body for tissue engineering [2].”

The high-frequency sound waves used in the stem cell treatment were generated on a low-cost microchip device developed by RMIT. Using high-frequency MHz-order mechanostimulation, the research team could trigger the differentiation of human mesenchymal stem cells towards osteoblast (bone building cells) lineage. In addition, rapid treatments of 10 minutes daily over a period of 5 days with high frequency (10 MHz) mechanostimulation triggered significant upregulation in early osteogenic markers and a sustained increase in late markers [1].

Co-lead researcher Distinguished Professor Leslie Yeo and his team have spent over a decade researching the interaction of sound waves at frequencies above 10 MHz with different materials and have developed a sound wave-generating device that can be used to precisely manipulate cells, fluids or materials.

“We can use the sound waves to apply just the right amount of pressure in the right places to the stem cells, to trigger the change process,” Yeo said. “Our device is cheap and simple to use, so could easily be upscaled for treating large numbers of cells simultaneously – vital for effective tissue engineering [2].”

As the researchers conclude in their paper: “Given the miniaturizability and low cost of the devices, the possibility for upscaling the platform toward practical bioreactors, to address a pressing need for more efficient stem cell differentiation technologies in the pursuit of translatable regenerative medicine strategies, is envisaged [1].”

The next stage in the research is investigating methods to upscale the platform, working towards the development of practical bioreactors to drive efficient stem cell differentiation for bone regeneration.