MEDICINE:Bone grafting is currently a difficult process, with many associated problems. RCSI have developed a material which could change all this, writes CLAIRE O'CONNELL

YOU PROBABLY don’t think much about your skeleton – until something goes wrong.

Disease and injury can damage joints and bones, sometimes to the point where you need surgery to replace or repair them and, no matter how you look at it, that kind of surgery is an invasive business.

But research at the Royal College of Surgeons in Ireland (RCSI) has come up with a bone graft substitute material to aid the healing and regeneration process.

The components and porous design of the material mean that, once implanted, it encourages the patient’s own bone to remodel at the injury site, and it supports new growth like a scaffold. The implanted material – known as HydroxyColl – degrades over time, leaving the new bone in place.

HydroxyColl is made of hydroxyapatite and collagen, substances that occur naturally in bone. It takes advantage of the bone tissue’s inherent ability to regrow, explains Dr John Gleeson, project and business development manager at RCSI’s Department of Anatomy.

“Bone is a very active material and remodels frequently,” he says. “It has an amazing ability to repair itself naturally once you don’t have too big a defect or site of damage.”

However, the current approach of surgically grafting actual bone tissue onto a site of injury can create problems.

“Currently the clinical gold standard is autografting whereby, if you need to augment the repair process, you would take a piece of bone from another site in the patient’s own body and reimplant it into the site that is damaged,” says Gleeson.

But that means another surgery site for the patient and, if there’s an underlying problem with the person’s bones, such as osteoporosis, the grafted bone may suffer from it too.

Another solution has been “allografting”, using bone donated from others, but the patient’s immune system could reject the donor graft, explains Gleeson. He says the practice of processing donated bone material can also have an impact on how the graft performs.

“Bone is harvested from donor patients from a number of sites worldwide. They would usually be stored in bone banks, or commercial businesses store and process these to reduce the risk of transmission of infectious disease,” he says. “But the process can remove cellular material that could promote the regenerative process once in the body.”

The alternative is a bone graft substitute. Some commercial products use materials coated with drugs to encourage bone tissue to grow, but Prof Fergal O’Brien’s research at RCSI has been developing HydroxyColl as a ‘bioactive’ material where the secret lies in the properties and design of the material itself, explains Gleeson.

“It’s optimised and designed to play a significant role in guiding a regenerative process as well as supporting it,” he says, explaining how the material can offer a scaffold to direct new growth.

“Cells can be directed and controlled to a certain extent by a number of different characteristics. The material they sit on has quite an influence on what they do, what they produce and what they might turn into.”

The porosity of the material also means that blood vessels can grow through the site and deliver nutrients and oxygen to the regenerating tissue, adds Gleeson.

“Our product is a highly porous material, it’s 99 per cent air, so there is lot of space for cells to get in and for them to grow networks, for fluids to perfuse,” he says. “It allows them to grow dynamically.”

Then, as the healing progresses, the bone substitute dissolves away.

“It’s highly biodegradable – we are able to match the regeneration of new tissue with the biodegradation of our scaffold,” says Gleeson. “So our material is made of the building blocks the cells are going to work with, and the cells are capable of remodelling what we put in there and then getting rid of it when they no longer need it.”

Pre-clinical trials have shown ‘phenomenal’ results, according to Gleeson. “We saw evidence, not only of healing, but that the bone is being actively remodelled or reshaped to return to the normal anatomy of the tissue itself,” he says.

Clinical trials are due to start this year through RCSI’s Cenre for Innovation in Surgical Technology. Gleeson reckons that in the long-term, HydroxyColl will be an “excellent material for small-to-medium sized bone grafts”. He notes that for large defects in bone or for older patients (who may have less of an inherent capacity to regenerate bone tissue) the scaffolds might be treated with additional growth factors before being used.

The team is also looking at the possibility of applying the material to dental practice.

“We have in the works a parallel study which is looking at using the material for dental reconstruction to improve the bedrock of the jaw,” says Gleeson. “So you have someone who is losing their teeth as they get older, their jawbone thins and you could maybe use these materials to improve the base where a dentist could implant a tooth.”

The scaffold could also be used for growing bone material in the lab before implantation into a patient. Research is currently underway at RCSI into optimising that process.

HydroxyColl is one of the technologies being presented at Enterprise Ireland’s Big Ideas Technology Showcase at Croke Park in October